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@ -51,4 +51,70 @@ Blake3:\\
SHA3-256:\\
\texttt{66ebbdb20b5459360368d29615e6e80f36bcf464d5519ca08ae651f27a8970bf}\\
\priloha{Whys}\label{appendix:whys}
This appendix is concerned with explaining why certain technologies were used.
\n{2}{Why Go}\label{appendix:whygo}
First, a question of \textit{`Why pick Go for building a web application?'}
might arise, so the following few lines will try to address that.
Go~\cite{golang}, or \emph{Golang} for SEO-friendliness and disambiguating Go
the ancient game, is a strongly typed, high-level \emph{garbage-collected}
language where functions are first-class citizens and errors are values.
The appeal for the author comes from a number of features of the language, such
as built-in support for concurrency and unit testing, sane \emph{zero} values,
lack of pointer arithmetic, inheritance and implicit type conversions,
easy-to-read syntax, producing a statically linked binary by default, etc., on
top of that, the language has got a cute mascot. Thanks to the foresight of the
Go Authors regarding \emph{the formatting question} (i.e.\ where to put the
braces, \textbf{tabs vs.\ spaces}, etc.), most of the discussions on this topic
have been foregone. Every \emph{gopher}\footnote{euph.\ a person writing in the
Go programming language} is expected to format their source code with the
official formatter (\texttt{gofmt}), which automatically ensures that the code
adheres to the one formatting standard. Then, there is \emph{The Promise} of
backwards compatibility for Go 1.x, which makes it a good choice for long-term
without the fear of being rug-pulled.
\n{2}{Why Nix/devenv}\label{appendix:whynix}
Nix (\url{https://builtwithnix.org/}) is a functional programming language
resembling Haskell and a declarative package manager, which has been used in
this project in the form of \texttt{devenv} tool (\url{https://devenv.sh/}) to
create \textbf{declarable} and \textbf{reproducible} development environment.
The author has previously used Nix directly with \emph{flakes} and liked
\texttt{devenv}, as it effectively exposed only a handful of parameters for
configuration, and rid of the need to manage the full flake, which is of course
still an option for people who choose so. See \texttt{devenv.nix} in the
repository root.
\priloha{Terminology}\label{appendix:terms}
\n{2}{Linux}
The term \emph{Linux} is exclusively used in the meaning of the
Linux kernel~\cite{linux}.
\n{2}{GNU/Linux}
As far as a Linux-based operating system is concerned, the term ``GNU/Linux''
as defined by the Free Software Foundation~\cite{fsfgnulinux} is used. While it
is longer and arguably a little bit cumbersome, the author aligns with the
opinion that this term more correctly describes its actual target. Being aware
that there are many people who conflate the complete operating system with its
(be it core) component, the kernel, the author is taking care to distinguish
the two, although writing from experience, colloquially, this probably brings
more confusion and a lengthy explanation is usually required.
\n{2}{The program}
By \emph{the program} or \emph{the application} without any additional context
the author most probably means the Password Compromise Monitoring Tool program.
% =========================================================================== %

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@ -179,7 +179,7 @@
@misc{age,
howpublished = {[online]},
title = {A simple, modern and secure encryption tool (and Go library) with small explicit keys, no config options, and UNIX-style composability.},
author = {Filippo Sotille and Ben Cox and age contributors},
author = {Filippo Valsorda and Ben Cox and age contributors},
year = 2021,
note={{Available from: \url{https://github.com/FiloSottile/age}. [viewed 2023-05-23]}}
}

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@ -72,177 +72,130 @@ practices in an effort to build a maintainable and long-lasting piece of
software that serves its users well. When deployed, it could provide real
value.
Terminology is located in Appendix~\ref{appendix:terms}, feel free to give it a
read.
% =========================================================================== %
\part{Theoretical part}
\n{1}{Terminology}
\n{2}{Linux}
The term \emph{Linux} is exclusively used in the meaning of the
Linux kernel~\cite{linux}.
\n{2}{GNU/Linux}
As far as a Linux-based operating system is concerned, the term ``GNU/Linux''
as defined by the Free Software Foundation~\cite{fsfgnulinux} is used. While it
is longer and arguably a little bit cumbersome, the author aligns with the
opinion that this term more correctly describes its actual target. Being aware
there are many people that conflate the complete operating system with its (be
it core) component, the kernel, the author is taking care to distinguish the
two, although writing from experience, colloquially, this probably brings more
confusion and a lengthy explanation is usually required.
\n{2}{Containers}
When the concept of \emph{containerisation} and \emph{containers} is mentioned
throughout this work, the author has OCI containers~\cite{ocicontainers} in
mind, which is broadly a superset of \emph{Linux Containers} where some set of
processes is presented with a view of kernel resources (there are multiple
kinds of resources, such as IPC queues; network devices, stacks, ports; mount
points, process IDs, user and group IDs, Cgroups and others) that differs for
each different set of processes, similar in thought to FreeBSD
\emph{jails}~\cite{freebsdjails} with the distinction being that they are, of
course, facilitated by the Linux kernel namespace
functionality~\cite{linuxnamespaces}, which is in turn regarded to be
\emph{inspired} by Plan 9's namespaces~\cite{plan9namespaces}, Plan 9 being a
Bell Labs successor to Unix 8th Edition, discontinued in 2015.
While there without a doubt \emph{is} specificity bound to using each of the
tools that enable creating (Podman vs.\ Buildah vs.\ Docker BuildX) or running
(ContainerD vs.\ runC vs.\ crun) container images, when describing an action
that gets performed with or onto a container, the process should generally be
explained in such a way that it is repeatable using any spec-conforming tool
that is available and \emph{intended for the job}.
\vspace*{-\baselineskip}
\n{2}{The program}
By \emph{the program} or \emph{the application} without any additional context
the author usually means the Password Compromise Monitoring Tool program.
\n{1}{Cryptography primer}\label{sec:cryptographyprimer}
\n{2}{Encryption}
Encryption is the process of transforming certain data, called a
\emph{message}, using, as Aumasson writes in Serious Cryptography, ``an
algorithm called a \emph{cipher} and a secret value called the
key''~\cite{seriouscryptography}. Its purpose is to protect the said message so
that only its intended recipients that know/hold the key are able to
\emph{decipher} and read it.
\n{3}{Symmetric encryption}
Symmetric encryption is simply when the \emph{key} used is to facilitate both
encryption and decryption operations.
\n{3}{Asymmetric encryption}
Asymmetric encryption is different from symmetric encryption in that there are
now two keys in use - a key \emph{pair}. One part is used solely for
encryption, while the other part's only purpose is to decrypt. This notion of
two keys is generally transposed to a domain called \emph{public key
cryptography}, whereby the decryption component is declared private and the
encryption component is called \emph{public}, hence the name. The rationale is
that everybody can encrypt messages \emph{for} the recipient but only they are
able to \emph{decrypt} them, which is a feature allowed by the mathematical
complementarity of the two components, and also explains why the private key
should be kept \emph{private}. Compared to symmetric encryption, this variant
is generally slower.
\n{3}{The key exchange problem}
Suppose a communication scheme that is protected by a pre-shared secret.
In order to establish secure communications, this secret needs to be
distributed to the other party via untrusted channels. In 1976 Whitfield Diffie
and Martin Hellman published a paper in which they devised a \emph{public-key
distribution scheme}, which allows the two parties to arrive at a shared secret
by exchanging information via insecure channels with the presence of an
eavesdropper. This scheme (or its variations) is in use to this day.
\textbf{TODO:} add \emph{why} we care and how it's going to be used.
\n{2}{Hash functions}
Hash functions are cryptographic algorithms used to help with a number of
things: integrity verification, password protection, digital signature,
public-key encryption and others. Hashes are used in forensic analysis to prove
authenticity of digital artifacts, to uniquely identify a change-set within
revision-based source code management systems such as Git, Subversion or
Mercurial, to detect known-malicious software by anti-virus programs or by
advanced filesystems in order to verify block integrity and enable repairs, and
also in many other applications that each person using a modern computing
device has come across, such as when connecting to a website protected by the
famed HTTPS.
Hash functions are algorithms used to help with a number of things: integrity
verification, password protection, digital signature, public-key encryption and
others. Hashes are used in forensic analysis to prove authenticity of digital
artifacts, to uniquely identify a change-set within revision-based source code
management systems such as Git, Subversion or Mercurial, to detect
known-malicious software by anti-virus programs or by advanced filesystems in
order to verify block integrity and enable repairs, and also in many other
applications that each person using a modern computing device has come across,
such as when connecting to a website protected by the famed HTTPS.
The popularity stems from a common use case: the need to identify a chunk of
data. Of course, two chunks of data, two files, frames or packets could always
be compared bit by bit, but that can get prohibitive from both cost and energy
point of view relatively quickly. That is when the hash functions come in,
since they are able to take a long input and produce a short output, named a
digest or a hash value. It also does not work the other way around, a file
cannot be reconstructed from the hash digest, it is a one-way function.
The popularity of hash functions stems from a common use case: the need to
simplify reliably identifying a chunk of data. Of course, two chunks of data,
two files, frames or packets could always be compared bit by bit, but that can
get prohibitive from both cost and energy point of view relatively quickly.
That is when the hash functions come in, since they are able to take a long
input and produce a short output, named a digest or a hash value. The function
also only works one way.
\n{3}{Rainbow tables}
A file, or any original input data for that matter, cannot be reconstructed
from the hash digest alone by somehow \emph{reversing} the hashing operation,
since at the heart of any hash function there is essentially a compression
function.
As passwords are in more responsible scenarios stored not directly but as
hashes, attackers that would be interested in recovering the passwords really
only have one option (except finding a critical vulnerability in the hash
function): rainbow tables. Rainbow tables are lists of pre-computed hashes
paired with the passwords that were used to create them. When attackers gain
access to a password breach that contains hashes, all it takes is to find a
match within the rainbow table and reversely resolve that to the known
message: the password.
Most alluringly, hashes are frequently used with the intent of
\emph{protecting} passwords by making those unreadable, while still being able
to verify that the user knows the password, therefore should be authorised.
One of the popular counter-measures to pre-computed tables is adding a
\emph{salt} to the user-provided password before passing it to the KDF (Key
Derivation Function) or the hash function. Of course, the salt should be random
\textbf{per-user} and not reused, as that would mean that two users with the
same password would still end up with the same hash, and the salt should also
be adequately long to be effective. As the salt is supposed to be
\emph{random}, it would be a good idea to use an actual CSPRNG, such as
\textbf{Fortuna}~\cite{fortuna} as a source of entropy (randomness). In
FreeBSD, Fortuna is in fact the one serving \texttt{/dev/random}.
As the hashing operation is irreversible, once the one-way function produces a
short a digest, there is no way to reconstruct the original message from it.
That is, unless the input of the hash function is also known, in which case all
it takes is hashing the supposed input and comparing the digest with existing
digests that are known to be digests of passwords.
\\ \textbf{TODO:} ad more on \emph{why} we care and what types of hashes should be
used (with refs) and why.
\n{3}{TLS}\label{sec:tls}
\n{3}{Types and use cases}
Hash functions can be loosely categorised based on their intended use case to
\emph{password protection hashes}, \emph{integrity verification hashes},
\emph{message authentication codes} and \emph{cryptographic hashes}. Each of
these possess unique characteristics and using the wrong type of hash function
for the wrong job can potentially result in a security breach.
As an example, suppose \texttt{MD5}, a popular hash function internally using
the same data structure - \emph{Merkle-Damgård} construction - as
\texttt{BLAKE3}. While the former produces 128 bit digests, the latter by
default outputs 256 bit digest with no upper limit (Merkle tree extensibility).
There is a list of differences that could further be mentioned, however, they
both have one thing in common: they are \emph{designed} to be \emph{fast}. The
latter, as a cryptographic hash function, is conjectured to be \emph{random
oracle indifferentiable}, secure against length extension, but it is also in
fact faster than all of \texttt{MD5}, \texttt{SHA3-256}, \texttt{SHA-1} and
even \texttt{Blake2} family of functions.
The use case of both is to (quickly) verify integrity of a given chunk of data,
in case of \texttt{BLAKE3} with pre-image and collision resistance in mind, not
to secure a password by hashing it first, which poses a big issue when used
to...secure passwords by hashing them first.
A password hash function, such as \texttt{argon2} or \texttt{bcrypt} are good
choices for securely storing hashed passwords, namely because they place CPU
and memory burden on the host computing the digest, as well as limit potential
parallelism, thus preventing the scale at which an exhaustive search could be
launched. Additionally, both functions automatically \emph{salt} the passwords
before hashing them, which means that two exact same passwords of two different
users will not end up hashing to the same digest value, making it that much
harder to recover the original, supposedly weak password.
\n{3}{Why are hashes interesting}
As already mentioned, since hashes are often used to store the
representation of the password instead of the password itself, they become a
subject of interest when they get leaked. There have been enough instances of
leaked raw passwords that anyone with enough interest can put together a neat
list of hashes of the most popular passwords.
So while the service does not store plain text passwords, which is good, using
a hashing function not designed to protect passwords does not offer much
additional protection in case of weak passwords, which are the most commonly
used ones.
It seems logical that a service that is not using cryptographic primitives
correctly is more likely to get hacked and have its users' passwords/hashes
leaked. Then, the Internet ends up serving as a storage of every data dump,
often exposing these passwords/hashes for everyone to access.
\n{2}{TLS}\label{sec:tls}
The Transport Layer Security protocol (or TLS) serves as as an encryption and
\emph{authentication} protocol to secure internet communications. An important
part of the protocol is the \emph{handhake}, during which the two communicating
part of the protocol is the \emph{handshake}, during which the two communicating
parties exchange messages that acknowledge each other's presence, verify each
other, choose what cryptographic algorithms will be used and decide session
keys. As there are multiple versions of the protocol in active duty even at the
moment, the server together with the client need to agree upon the version they
are going to use (these days it should be 1.2 or 1.3), pick cipher suites
(TLSv1.3 dramatically reduced the number of available suites), the client
verifies the server's public key (and the signature of the certificate
authority that issued it) and they both generate session keys for use after
handshake completion.
are going to use (these days it is recommended to use either 1.2 or 1.3),
pick cipher suites (), the client verifies the server's public key (and the signature of the
certificate authority that issued it) and they both generate session keys for
use after handshake completion.
The handshake consists of multiple stages (again, depending on the version), for
TLSv1.3 that would be:
\begin{itemize}
\item \textbf{Client hello}: client sends a client hello message containing
the protocol version, a list of cipher suites and the client random value.
The client in this step also includes the ephemeral Diffie-Helman (EDH)
parameters, which are later used for calculating the pre-master key.
\item \textbf{Server generating a master secret}: the server has got the
cipher suites, the client's paramaters and client random and already has
the server random, which means it can create the master secret.
\item \textbf{Server hello and ``Finished''}: the server includes in the
hello its certificate, digital signature, server random, the chosen
cipher suite, and sends a ``Finished'' (meaning \emph{ready}) message.
\item \textbf{Signature and certificate verification}: the client at this
step verifies server's certificate and signature, generates the master
secret and is ready (sends the ``Finished'' message).
\end{itemize}
At the end of the process, the connection is protected by symmetric encryption
using the session key that the both parties have arrived at.
TLSv1.3 dramatically reduced the number of available suites to only include the
ones deemed secure enough, which is why it is no longer needed to manually
specify what cipher suite should be used (or rely on the client/server to
choose wisely). While possibly facing compatibility issues with legacy devices,
the simplicity that enabling TLSv1.3 brings is a worthy trade-off.
\n{1}{Passwords}\label{sec:passwords}
@ -381,151 +334,7 @@ internet that is discussed in the next sections and covers what browsers are,
what they do and how they relate to web security.
\n{2}{Browsers}\label{sec:browsers}
Browsers, sometimes used together with the word that can serve as a real tell
for their specialisation - \emph{web} browsers - are programs intended for
\emph{browsing} of \emph{the web}. In more technical terms, browsers are
programs that facilitate (directly or via intermediary tools) domain name
lookups, connecting to web servers, optionally establishing a secure
connection, requesting the web page in question, determining its \emph{security
policy} and resolving what accompanying resources the web page specifies and
depending on the applicable security policy, requesting those from their
respective origins, applying stylesheets and running scripts. Constructing a
program that can speak many protocols and securely runs untrusted code from the
internet is no easy task.
\n{3}{Complexity}
Browsers these days are also quite ubiquitous programs running on
\emph{billions} of consumer grade mobile devices (which are also notorious for
bad update hygiene) or desktop devices all over the world. Regular users
usually expect them to work flawlessly with a multitude of network conditions,
network scenarios (the proverbial café WiFi, cellular data in a remote
location, home broadband that is DNS-poisoned by the ISP), differently tuned
(or commonly misconfigured) web servers, a combination of modern and
\emph{legacy} encryption schemes and different levels of conformance to web
standards from both web server and website developers. Of course, if a website
is broken, it is the browser's fault. Browsers are expected to detect if
\emph{captive portals} (a type of access control that usually tries to force
the user through a webpage with terms of use) are active and offer redirects.
All of this is immense complexity and the combination of ubiquity and great
exposure that this type of software gets is, in the author's opinion, the cause
behind a staggering amount of vulnerabilities found, reported and fixed in
browsers every year.
\n{3}{Standardisation}
Over the years, a consortium of parties interested in promoting and developing
the web (also due to its potential as a digital marketplace, i.e.\ financial
incentives) and browser vendors (of which the most neutral participant is
perhaps \emph{Mozilla}, with Chrome being run by Google, Edge by Microsoft and
Safari/Webkit by Apple) has evolved a great volume of web standards, which are
also relatively frequently getting updated or deprecated and replaced by
revised or new ones, rendering the browser maintenance task into essentially a
cat-and-mouse game.
It is the web's extensibility that enabled this build-up and ironically has
been proclaimed by some to be its greatest asset. It has also been ostensibly
been criticised~\cite{ddvweb} in the past and the frustration with the status
quo of web standards has relatively recently prompted a group of people to even
create ``\textit{a new application-level internet protocol for the distribution
of arbitrary files, with some special consideration for serving a lightweight
hypertext format which facilitates linking between files}'':
Gemini~\cite{gemini}\cite{geminispec} that in the words of its authors can be
thought of as ``\textit{the web, stripped right back to its essence}'' or as
``\textit{Gopher, souped up and modernised just a little}'', depending upon the
reader's perspective, noting that the latter view is probably more accurate.
\n{3}{HTTP}
Originally, HTTP was also designed just for fetching hypertext
\emph{resources}, but it has evolved since then, particularly due to its
extensibility, to allow for fetching of all sorts of web resources a modern
website of today provides, such as scripts or images, or even to \emph{post}
content back to servers.
HTTP relies on TCP (Transmission Control Protocol), which is one of the
\emph{reliable} (mandated by HTTP) protocols used to send data across
contemporary IP (Internet Protocol) networks, to deliver the data it requests
or sends. When Tim Berners-Lee invented the World Wide Web (WWW) in 1989 while
working at CERN (The European Organization for Nuclear Research) with a rather
noble intent as a ``\emph{wide-area hypermedia information retrieval initiative
to give universal access to a large universe of documents}''~\cite{wwwf}, he
also invented the HyperText Markup Language (HTML) to serve as a formatting
method for these new hypermedia documents. The first website was written
roughly the same way as today's websites are, using HTML, although the markup
language has changed since, with the current version being HTML5.
It has been mentioned that the client \textbf{requests} a \textbf{resource} and
receives a \textbf{response}, so those terms should probably be defined.
A request is what the client sends to the server. A resource is what it
requests and a response is the answer provided by the server.
HTTP follows a classic client-server model whereby it is \textbf{always} the
client that initiates the request.
A web page is, to be blunt, a chunk of \emph{hypertext}. To display a web page,
a browser first needs to send a request to fetch the HTML representing the
page, which is then parsed and additional requests for sub-resources are made.
If a page defines a layout information in the form of CSS, that is parsed as
well.
A web page needs to be present on the local computer first \emph{before} it can
be parsed by the browser, and since websites are usually still served by
programs called \emph{web servers} as in the \emph{early days}, that presents a
problem of how tell the browser where the resource should be fetched from. In
today's browsers, the issue is sorted (short of the CLI) by the \emph{address
bar}, a place into which user types what they wish the browser to fetch for
them.
The formal name of this segment is a \emph{Universal Resource Locator}, or URL,
and it contains the schema (or the protocol, such as \texttt{http://}), the
host address or a domain name and a (TCP) port number.
Since a TCP connection needs to be established first, to connect to a server
whose only URL contains a domain name, the browser needs to perform a domain
name \emph{lookup} using system facilities, or as was the case for a couple of
notorious Chromium versions, send some additional and unrelated queries which
(with Chromium-based derivatives' numbers) ended up placing unnecessary load
directly at the root DNS servers~\cite{chromiumrootdns}.
If a raw IP address+port combination is used, the browser attempts to connect
to it directly and requests the user-requested page by default using the
\texttt{GET} \emph{method}. A \emph{well-known} HTTP port 80 is assumed unless
other port is explicitly specified and it can be omitted both if host is a
domain name or an IP address.
The method is a way for the user-agent to define what operation it wants to
perform. \texttt{GET} is used for fetching resources while \texttt{POST} is
used to send data to the server, such as to post the values of an HTML form.
A server response is comprised of a \textbf{status code}, a status message,
HTTP \textbf{headers} and an optional \textbf{body} containing the content. The
status code indicates if the original request was successful or not and the
browser is generally there to interpret these status codes to the user. There
is enough status codes to be confused by the sheer numbers but luckily, there
is a method to the madness and they can be divided into groups/classes:
\begin{itemize}
\item 1xx: Informational responses
\item 2xx: Successful responses
\item 3xx: Redirection responses
\item 4xx: Client error responses
\item 5xx: Server error responses
\end{itemize}
In case the \emph{user agent} (a web \emph{client}) such as a browser receives
a response with content, it has to parse it.
A header is additional information sent by both the server and the client that
can guide or alter the behaviour of software reading it. For instance a
\texttt{Cache-control} header with a duration value can be used by the server
to signify that the client can store certain resources for some time before
needing to re-fetch them, if they are not \emph{expired}.
\n{3}{Site Isolation}
\n{2}{Site Isolation}
Modern browsers such as Firefox or Chromium come with a security focus in mind.
Their developers are acutely aware of the dangers that parsing untrusted code
@ -558,6 +367,7 @@ access to session tokens and any cookies associated with the website's origin,
apart from being able to rewrite the HTML content. The results of XSS can
range from account compromise to identity theft.
\n{2}{Content Security Policy}\label{sec:csp}
Content Security Policy (CSP) has been an important addition to the arsenal of
@ -600,15 +410,380 @@ in production. There are many more directives and settings than mentioned in
this section, the author encourages anybody interested to give it a read, e.g.\
at \url{https://web.dev/csp/}.
\n{2}{Summary}
\textbf{TODO}: add more concrete examples.
Passwords are in use everywhere and probably will be for the foreseeable
future. As long as passwords are going to be handled and stored by
service/application providers, they are going to get leaked, be it due to
provider carelessness or the attackers' resolve and wit. Of course, sifting
through all the available password breach data by hand is not a reasonable
option, and therefore tools should come in to provide assistance. The next part
of the thesis will explore that and offer a solution.
\n{1}{Configuration}
Every non-trivial program usually offers at least \emph{some} way to
tweak/manage its behaviour, and these changes are usually persisted
\emph{somewhere} on the filesystem of the host: in a local SQLite3 database, a
\emph{LocalStorage} key-value store in the browser, a binary or plain text
configuration file. These configuration files need to be read and checked at
least on program start-up and either stored into operating memory for the
duration of the runtime of the program, or loaded and parsed and the memory
subsequently \emph{freed} (initial configuration).
There is an abundance of configuration languages (or file formats used to craft
configuration files, whether they were intended for it or not) available, TOML,
INI, JSON, YAML, to name some of the popular ones (as of today).
Dhall stood out as a language that was designed with both security and the
needs of dynamic configuration scenarios in mind, borrowing a concept or two
from Nix~\cite{nixoslearn}~\cite{nixlang} (which in turn sources more than a
few of its concepts from Haskell), and in its apparent core being very similar
to JSON, which adds to familiar feel. In fact, in Dhall's authors' own words it
is: ``a programmable configuration language that you can think of as: JSON +
functions + types + imports''~\cite{dhalllang}.
Among all of the listed features, the especially intriguing one to the author
was the promise of \emph{types}. There are multiple examples directly on the
project's documentation webpage demonstrating for instance the declaration and
usage of custom types (that are, of course merely combinations of the primitive
types that the language provides, such as \emph{Bool}, \emph{Natural} or
\emph{List}, to name just a few), so it was not exceedingly hard to start
designing a custom configuration \emph{schema} for the program.
Dhall not being a Turing-complete language also guarantees that evaluation
\emph{always} terminates eventually, which is a good attribute to possess as a
configuration language.
\n{3}{Safety considerations}
Having a programmable configuration language that understands functions and
allows importing not only arbitrary text from random internet URLs, but also
importing and \emph{evaluating} (i.e.\ running) potentially untrusted code, it
is important that there are some safety mechanisms employed, which can be
relied on by the user. Dhall offers this in multiple features: enforcing a
same-origin policy and (optionally) pinning a cryptographic hash of the value
of the expression being imported.
\n{3}{Possible alternatives}
While developing the program, the author has also
come across certain shortcomings of Dhall, namely long start-up with \emph{cold
cache}, which can generally be observed in the scenario of running the program
in an environment that does not allow to write the cache files (a read-only
filesystem), of does not keep the written cache files, such as a container that
is not configured to mount a persistent volume at the pertinent location.
To describe the way Dhall works when performing an evaluation, it resolves
every expression down to a combination of its most basic types (eliminating all
abstraction and indirection) in the process called
\textbf{normalisation}~\cite{dhallnorm} and then saves this result in the
host's cache. The \texttt{dhall-haskell} binary attempts to resolve the
variable \texttt{\$\{XDG\_CACHE\_HOME\}} (have a look at \emph{XDG Base
Directory Spec}~\cite{xdgbasedirspec} for details) to decide \emph{where} the
results of the normalisation will be written for repeated use. Do note that
this behaviour has been observed on a GNU/Linux host and the author has not
verified this behaviour on a non-GNU/Linux host, such as FreeBSD.
If normalisation is performed inside an ephemeral container (as opposed to, for
instance, an interactive desktop session), the results effectively get lost on
each container restart. That is both wasteful and not great for user
experience, since the normalisation of just a handful of imports (which
internally branches widely) can take an upwards of two minutes, during which
the user is left waiting for the hanging application with no reporting on the
progress or current status.
While workarounds for the above mentioned problem can be devised relatively
easily (such as bind mounting persistent volumes inside the container in place
of the \texttt{\$\{XDG\_CACHE\_HOME\}/dhall} and
\texttt{\$\{XDG\_CACHE\_HOME\}/dhall-haskell} to preserve the cache between
restarts, or let the cache be pre-computed during container build, since the
application is only really expected to run together with a compatible version
of the configuration schema and this version \emph{is} known at container build
time), it would certainly feel better if there was no need to work
\emph{around} the configuration system of choice.
Alternatives such as CUE (\url{https://cuelang.org/}) offer themselves nicely
as a potentially almost drop-in replacement for Dhall feature-wise, while also
resolving costly \emph{cold cache} normalisation operations, which is in
author's view Dhall's titular issue.
\n{1}{Compromise Monitoring}
There are, of course, several ways one could approach monitoring of compromised
of credentials, some more \emph{manual} in nature than others. When using a
service that is suspected/expected to be breached in the future, one can always
create a unique username/password combination specifically for the subject
service and never use that combination anywhere else. That way, if the
credentials ever \emph{do} happen to appear in a data dump online in the
future, it is going to be a safe assumption as to where they came from.
Unfortunately, the task of actually \emph{monitoring} the credentials can prove
to be a little more arduous than one could expect at first. There are a couple
of points that can prove to pose a challenge in case the search is performed by
hand, namely:
\begin{itemize}
\item finding the breached data to look through
\item verifying the trustworthiness of the data
\item varying quality of the data
\item sifting through (possibly) unstructured data by hand
\end{itemize}
Of course, as this is a popular topic for a number of people, the above
mentioned work has already been packaged into neat and practical online
offerings. In case one decides in favour of using those, an additional range of
issues (the previous one still applicable) arises:
\begin{itemize}
\item the need to trust the provider with input credentials
\item relying on the goodwill of the provider to be able to access the data
\item hoping that the terms of service are kept
\end{itemize}
Besides that, there is a plethora of breaches floating around the Internet
available simply as zip files, which makes the job even harder.
The overarching goal of this thesis is devising and implementing a system in
which the user can \emph{monitor} whether their credentials have been
\emph{compromised} (at least as far as the data can tell), and allowing them to
do so without needing to entrust their sensitive data to a provider.
\n{2}{Data Sources}\label{sec:dataSources}
A data source in this place is considered anything that provides the
application with data that it understands.
Of course, the results of credential compromise verification/monitoring is only
going to be as good as the data underpinning it, which is why it is imperative
that high quality data sources be used, if at all possible. While great care
does have to be taken to only choose the highest quality data sources, the
application must offer a means to be able to utilise these.
The sources from which breached data can be loaded into an application can be
split into two basic categories: \textbf{online} or \textbf{local}, and it is
possible to further discern between \emph{structured} and \emph{unstructured}
data.
An online source is generally a service that ideally exposes a programmatic
API, which an application can query and from which it can request the necessary
subsets of data.
These types of services often additionally front the data by a user-friendly
web interface for one-off searches, which is, however, not of use here.
Among some examples of online services could be named:
\begin{itemize}
\item {Have I Been Pwned?} - \url{https://haveibeenpawned.com}
\item {DeHashed} - \url{https://dehashed.com}
\end{itemize}
Large lumps of unstructured data available on forums or shady web servers would
technically also count here, given that they provide data and are available
online. However, even though data is frequently found online precisely in this
form, it is also not of direct use for the application without manual
\emph{preprocessing}, as it is attended to in
Section~\ref{sec:localDatasetPlugin}.
Another source is then simply any locally supplied data, which, of course,
could have been obtained from a breach available online beforehand.
Locally supplied data is specific in that it needs to be formatted in such a
way that it can be understood by the application. That is, the data is not in
its raw form anymore but has been morphed into the precise shape the
application needs for further processing. Once imported, the application can
query the data at will, as it knows exactly the shape of it.
This supposes the existence of a \emph{format} for importing, schema of which
is devised in Section~\ref{sec:localDatasetPlugin}.
\n{3}{Local Dataset Plugin}\label{sec:localDatasetPlugin}
Unstructured breach data from locally available datasets can be imported into
the application by first making sure it adheres to the specified schema (have a
look at the \emph{Breach Data Schema} in Listing~\ref{breachDataGoSchema}). If
it does not (which is very likely with random breach data, as already mentioned
in Section~\ref{sec:dataSources}), it needs to be converted to a form that
\emph{does} before importing it to the application, e.g.\ using a Python script
or a similar method.
Attempting to import data that does not follow the outlined schema should
result in an error. Equally so, importing a dataset which is over a reasonable
size limit should by default be rejected by the program as a precaution.
Unmarshaling, for instance, a 1 TiB document would most likely result in an
out-of-memory (OOM) situation on the host running the application, assuming
contemporary consumer hardware conditions (not HPC).
\vspace{\parskip}
\begin{lstlisting}[language=Go, caption={Breach Data Schema represented as a Go
struct with imports from the standard library assumed},
label=breachDataGoSchema]
type breachDataSchema struct {
Name string
Time time.Time
IsVerified bool
ContainsPasswords bool
ContainsHashes bool
HashType string
HashSalted bool
HashPepperred bool
ContainsUsernames bool
ContainsEmails bool
Data any
}
\end{lstlisting}
\vspace*{-\baselineskip}
The Go representation shown in Listing~\ref{breachDataGoSchema} will in
actuality translate to a YAML document written and supplied by an
administrative user of the program. The YAML format was chosen for several
reasons:
\begin{itemize}
\item relative ease of use (plain text, readability)
\item capability to store multiple \emph{documents} inside of a single file
\item most of the inputs being implicitly typed as strings
\item support for inclusion of comments
\item machine readability thanks to being a superset of JSON
\end{itemize}
The last point specifically should allow for documents similar to what can be
seen in Listing~\ref{breachDataYAMLSchema} to be ingested by the program, read
and written by humans and programs alike.
\smallskip
\begin{lstlisting}[language=YAML, caption={Example Breach Data Schema supplied
to the program as a YAML file, optionally containing multiple documents},
label=breachDataYAMLSchema]
---
name: Horrible breach
time: 2022-04-23T00:00:00Z+02:00
isVerified: false
containsPasswds: false
containsHashes: true
containsEmails: true
hashType: md5
hashSalted: false
hashPeppered: false
data:
hashes:
- hash1
- hash2
- hash3
emails:
- email1
-
- email3
---
# document #2, describing another breach.
name: Horrible breach 2
...
\end{lstlisting}
\vspace*{-\baselineskip}
Notice how the emails list in Listing~\ref{breachDataYAMLSchema} misses one
record, perhaps because it was not supplied or mistakenly omitted. This is a
valid scenario (mistakes happen) and the application needs to be able to handle
it. The alternative would be to require the user to prepare the data in such a
way that the empty/partial records would be dropped entirely.
\n{3}{Have I Been Pwned? Integration}
Troy Hunt's \textbf{Have I Been Pwned?} online service
(\url{https://haveibeenpwned.com/}) has been chosen as the online source of
compromised data. The service offers private APIs that are protected by API
keys. The application's \texttt{hibp} module and database representation models
the values returned by this API, which allows searching in large breaches using
email addresses.\\
The architecture there is relatively simple: the application administrator
configures an API key for HIBP, the user enters the query parameters, the
application constructs a query and calls the API and waits for a response. As
the API is rate-limited based on the key supplied, this can pose an issue and
it has not been fully resolved in the UI. The application then parses the
returned data and binds it to the local model for validation. If that goes
well, the data is saved into the database as a cache and the search query is
performed on the saved data. If it returns anything, it is displayed to the
user for browsing.
\n{1}{Deployment recommendations}\label{sec:deploymentRecommendations}
It is, of course, recommended that the application runs in a secure environment
\allowbreak although definitions of that almost certainly differ depending on
who you ask. General recommendations would be either to effectively reserve a
machine for a single use case - running this program - so as to dramatically
decrease the potential attack surface of the host, or run the program isolated
in a container or a virtual machine. Further, if the host does not need
management access (it is a deployed-to-only machine that is configured
out-of-band, such as with a \emph{golden} image/container or declaratively with
Nix), then an SSH \emph{daemon} should not be running in it, since it is not
needed. In an ideal scenario, the host machine would have as little software
installed as possible besides what the application absolutely requires.
System-wide cryptographic policies should target highest feasible security
level, if at all available (such as by default on Fedora or RHEL), covering
SSH, DNSSec, IPsec, Kerberos and TLS protocols. Firewalls should be configured
and SELinux (kernel-level mandatory access control and security policy
mechanism) running in \emph{enforcing} mode, if available.
\n{2}{Transport security}
User connecting to the application should rightfully expect for their data to
be protected \textit{in transit} (i.e.\ on the way between their browser and
the server), which is what \emph{Transport Layer Security} family of
protocols~\cite{tls13rfc8446} was designed for, and which is the underpinning
of HTTPS. TLS utilises the primitives of asymmetric cryptography to let the
client authenticate the server (verify that it is who it claims it is) and
negotiate a symmetric key for encryption in the process named the \emph{TLS
handshake} (see Section~\ref{sec:tls} for more details), the final purpose of
which is establishing a secure communications connection. The operator should
configure the program to either directly utilise TLS using configuration or
have it listen behind a TLS-terminating \emph{reverse proxy}.
\n{2}{Containerisation}
Whether the pre-built or a custom container image is used to deploy the
application, it still needs access to secrets, such as database connection
string (containing database host, port, user, password/encrypted password,
authentication method and database name).
The application should be able to handle the most common Postgres
authentication methods~\cite{pgauthmethods}, namely \emph{peer},
\emph{scram-sha-256}, \emph{user name maps} and raw \emph{password}, although
the \emph{password} option should not be used in production, \emph{unless} the
connection to the database is protected by TLS.\ In any case, using the
\emph{scram-sha-256}~\cite{scramsha256rfc7677} method is preferable. One of the
ways to verify in development environment that everything works as intended is
the \emph{Password generator for PostgreSQL} tool~\cite{goscramsha256}, which
allows retrieving the encrypted string from a raw user input.
If the application running in a container wants to use the \emph{peer}
authentication method, it is up to the operator to supply the Postgres socket
to the application (e.g.\ as a volume bind mount). This scenario was not
tested; however, and the author is also not entirely certain how \emph{user
namespaces} (on GNU/Linux) would influence the process (as in when the
\emph{ID}s of a user \textbf{outside} the container are mapped to a range of
\emph{UIDs} \textbf{inside} the container), for which the setup would likely
need to account.
Equally, if the application is running inside the container, the operator needs
to make sure that the database is either running in a network that is also
directly attached to the container or that there is a mechanism in place that
routes the requests for the database hostname to the destination.
One such mechanism is container name based routing inside \emph{pods}
(Podman/Kubernetes), where the resolution of container names is the
responsibility of a specially configured (often auto-configured) piece of
software called Aardvark for the former and CoreDNS for the latter.
\n{1}{Summary}
Passwords (and/or passphrases) are in use everywhere and quite probably will be
for the foreseeable future. If not as \textit{the} principal way to
authenticate, then at least as \textit{a} way to authenticate. As long as
passwords are going to be handled and stored by service/application providers,
they are going to get leaked, be it due to provider carelessness or the
attackers' resolve and wit. Of course, sifting through all the available
password breach data by hand is not a reasonable option, and therefore tools
providing assistance come in handy. The next part of this diploma thesis will
explore that issue and introduce a solution.
% =========================================================================== %
@ -616,14 +791,10 @@ of the thesis will explore that and offer a solution.
\n{1}{Kudos}
\textbf{Disclaimer:} the author is not affiliated in any way with any of the
projects described on this page.
The \textit{Password Compromise Monitoring Tool} (\texttt{pcmt}) program has
been developed using and utilising a great deal of free (as in Freedom) and
open-source software in the process, either directly or as an outstanding work
tool, and the author would like to take this opportunity to recognise that
fact.
The program that has been developed as part of this thesis used and utilised a
great deal of free (as in \textit{freedom}) and open-source software in the
process, either directly or as an outstanding work tool, and the author would
like to take this opportunity to recognise that fact\footnotemark.
In particular, the author acknowledges that this work would not be the same
without:
@ -641,9 +812,12 @@ without:
All of the code written has been typed into VIM (\texttt{9.0}), the shell used
to run the commands was ZSH, both running in the author's terminal emulator of
choice - \texttt{kitty} on a \raisebox{.8ex}{\texttildelow}8 month (at the time
of writing) installation of \textit{Arch Linux (by the way)} using a
\texttt{6.3.x-wanderer-zfs-xanmod1} variant of the Linux kernel.
choice, \texttt{kitty}. The development machines ran a recent installation of
\textit{Arch Linux (by the way)} and Fedora 38, both using a \texttt{6.3.x}
XanMod variant of the Linux kernel.
\footnotetext{\textbf{Disclaimer:} the author is not affiliated in any way with any
of the projects described on this page.}
\n{1}{Development}
@ -689,9 +863,9 @@ There is one caveat to this though, git first needs some additional
configuration for the code in Listing~\ref{gitverif} to work as one would
expect. Namely that the public key used to verify the signature needs to be
stored in git's ``allowed signers file'', then git needs to be told where that
file is using the configuration value \texttt{gpg.ssh.allowedsignersfile} and
finally the configuration value of the \texttt{gpg.format} field needs to be
set to \texttt{ssh}.
file is located using the configuration value
\texttt{gpg.ssh.allowedsignersfile} and finally the configuration value of the
\texttt{gpg.format} field needs to be set to \texttt{ssh}.
Because git allows the configuration values to be local to each repository,
both of the mentioned issues can be solved by running the following commands
@ -703,10 +877,11 @@ label=gitsshprep, basicstyle=\linespread{0.9}\footnotesize\ttfamily]
% # set the signature format for the local repository.
% git config --local gpg.format ssh
% # save the public key.
% cat >./tmp/.allowed_signers \
<<<'leo ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIKwshTdBgLzwY4d8N7VainZCngH88OwvPGhZ6bm87rBO'
% cat > ./.tmp-allowed_signers \
<<<'surtur <insert literal surtur pubkey>
leo <insert literal leo pubkey>'
% # set the allowed signers file path for the local repository.
% git config --local gpg.ssh.allowedsignersfile=./tmp/.allowed_signers
% git config --local gpg.ssh.allowedsignersfile=./.tmp-allowed_signers
\end{lstlisting}
\vspace*{-\baselineskip}
@ -767,17 +942,17 @@ The fourth pipeline focuses on linting the Containerfile and building the
container, although the latter action is only performed on feature branches,
\emph{pull requests} or \emph{tag} events.
The median build time as of writing was 1 minute, which includes running all
four pipelines, and that is acceptable. Build times might of course vary
depending on the hardware, for reference, these builds were being run on a
machine equipped with a Zen 3 Ryzen 5 5600 CPU with nominal clock times, DDR4
3200MHz RAM, a couple of PCIe Gen 4 NVMe drives in a mirrored setup (using ZFS)
and a 400Mbps downlink, software-wise running Arch with an author-flavoured
Xanmod kernel version 6.3.x.
\obr{Drone CI median build
time}{fig:drone-median-build}{.84}{graphics/drone-median-build}
The median build time as of writing was 1 minute, which includes running all
four pipelines, and that is acceptable. Build times might of course vary
depending on the hardware, for reference, these builds were run on a machine
equipped with a Zen 3 Ryzen 5 5600 CPU with nominal clock times, DDR4 3200MHz
RAM, a couple of PCIe Gen 4 NVMe drives in a mirrored setup (using ZFS) and a
400Mbps downlink, software-wise running Arch with an author-flavoured Xanmod
kernel version 6.3.x.
\n{2}{Source code repositories}\label{sec:repos}
@ -805,20 +980,28 @@ The repository containing the \LaTeX{} source code of this thesis:\\
\n{2}{Toolchain}
Throughout the creation of this work, the \emph{current} version of the Go
Throughout the creation of this work, the \emph{then-current} version of the Go
programming language was used, i.e. \texttt{go1.20}.
To read more on why Go was chosen, see Appendix~\ref{appendix:whygo}.
Nix/\texttt{devenv} tools have also aided heavily during development, see
Appendix~\ref{appendix:whynix} to learn more.
\tab{Tool/Library-Usage Matrix}{tab:toolchain}{1.0}{ll}{
\textbf{Name} & \textbf{Usage} \\
Go programming language & program core \\
Dhall configuration language & program configuration \\
Echo & HTTP handlers, controllers, web server \\
ent & ORM using graph-based modelling \\
bluemonday & HTML sanitising \\
bluemonday & sanitising HTML \\
TailwindCSS & stylesheets using a utility-first approach \\
PostgreSQL & storing data \\
PostgreSQL & persistently storing data \\
}
Table~\ref{tab:depsversionmx} contains the names and versions of the most
important libraries and supporting software that were used to build the
application.
\tab{Dependency-Version Matrix}{tab:depsversionmx}{1.0}{ll}{
\textbf{Name} & \textbf{version} \\
\texttt{echo} (\url{https://echo.labstack.com/}) & 4.10.2 \\
@ -829,90 +1012,85 @@ programming language was used, i.e. \texttt{go1.20}.
\texttt{PostgreSQL} (\url{https://www.postgresql.org/}) & 15.2 \\
}
\n{2}{A word about Go}
First, a question of \textit{`Why pick Go for building a web
application?'} might arise, so the following few lines will try to address
that.
Go~\cite{golang}, or \emph{Golang} for SEO-friendliness and disambiguating Go
the ancient game, is a strongly typed, high-level \emph{garbage-collected}
language where functions are first-class citizens and errors are values.
The appeal for the author comes from a number of features of the language, such
as built-in support for concurrency and unit testing, sane \emph{zero} values,
lack of pointer arithmetic, inheritance and implicit type conversions,
easy-to-read syntax, producing a statically linked binary by default, etc., on
top of that, the language has got a cute mascot. Thanks to the foresight of the
Go Authors regarding \emph{the formatting question} (i.e.\ where to put the
braces, \textbf{tabs vs.\ spaces}, etc.), most of the discussions on this topic
have been foregone. Every \emph{gopher}~\footnote{euph.\ a person writing in
the Go programming language} is expected to format their source code with the
official formatter (\texttt{gofmt}), which automatically ensures that the code
adheres to the one formatting standard. Then, there is \emph{The Promise} of
backwards compatibility for Go 1.x, which makes it a good choice for long-term
without the fear of being rug-pulled.
\n{2}{A word about Nix/devenv}
Nix (\url{https://builtwithnix.org/}) is a declarative package manager and a
functional programming language resembling Haskell, which has been used in this
project in the form of \texttt{devenv} tool (\url{https://devenv.sh/}) to
create \textbf{declarable} and \textbf{reproducible} development environment.
The author has previously used Nix directly with \emph{flakes} and liked
\texttt{devenv}, as it effectively exposed only a handful of parameters for
configuration, and rid of the need to manage the full flake, which is of course
still an option for people who choose so. See \texttt{devenv.nix} in the
repository root.
\n{1}{Application architecture}
The source code of the main module further is split into Go \emph{packages}
appropriately along a couple of domains: logging, core application, web
routers, configuration and settings, etc. In Go, packages are delimited by
folder structure -- each folder can be package.
\n{2}{Package structure}
The source code of the main module is organised into smaller, self-contained Go
\emph{packages} appropriately along a couple of domains: logging, core
application, web routers, configuration and settings, etc. In Go, packages are
delimited by folder structure -- each folder can be a package.
Generally speaking, the program aggregates decision points into central places,
such as \texttt{run.go}, which imports child packages that facilitate each of
loading the configuration, connecting to the database and running migrations,
consolidating flag, environment variable and configuration-based values into
canonical \emph{settings}, setting up routes and handling graceful shutdown.
such as \texttt{run.go}, which then imports child packages that facilitate each
of the task of loading the configuration, connecting to the database and
running migrations, consolidating flag, environment variable and
configuration-based values into canonical \emph{settings}, setting up routes
and handling graceful shutdown.
\n{3}{Internal package}
The \texttt{internal} package was not used as of writing, but the author plans
to eventually migrate \emph{internal} logic of the program into the internal
package to prevent accidental imports.
\n{2}{Logging}
The program uses dependency injection to share a single logger instance,
similar applies to the database client. These are passed around as a pointer,
so the underlying data stays the same. As a rule of thumb, every larger
\texttt{struct} that needs to be passed around is passed around as a pointer.
The \texttt{internal} package was not used as of writing, but the author plans
to eventually migrate \emph{internal} logic of the program into the internal
package to prevent accidental imports.
The authentication logic is relatively simple and the author would like to
\n{2}{Authentication}
The authentication logic is relatively simple and the author attempted to
isolate it into a custom \emph{middleware}. User passwords are hashed using a
secure KDF before being sent to the database. The KDF used is \texttt{bcrypt}
(with a sane \emph{Cost} of 10), which automatically includes \emph{salt} for
the password and provides ``length-constant'' time hash comparisons. The author
plans to add support for the more modern \texttt{scrypt} and the
state-of-the-art, P-H-C (Password Hashing Competition) winner algorithm
\texttt{Argon2} (\url{https://github.com/P-H-C/phc-winner-argon2}). Besides, no
raw queries are used to access the database, helping decrease the likelihood of
SQL injection attacks.
secure KDF before being sent to the database. The KDF of choice is
\texttt{bcrypt} (with a sane \emph{Cost} of 10), which automatically includes
\emph{salt} for the password and provides ``length-constant'' time hash
comparisons. The author plans to add support for the more modern
\texttt{scrypt} and the state-of-the-art, P-H-C (Password Hashing Competition)
winner algorithm \texttt{Argon2}
(\url{https://github.com/P-H-C/phc-winner-argon2}) for flexibility.
\n{2}{SQLi prevention}
No raw SQL queries are directly used to access the database, thus decreasing
the likelihood of SQL injection attacks. Instead, parametric queries are
constructed in code using a graph-like API of the \texttt{ent} library, which
is attended to in-depth in Section~\ref{sec:dbschema}.
\n{2}{Configurability}
Virtually any important value in the program has been made into a configuration
value, so that the operator can customise the experience as needed. A choice of
sane configuration defaults was attempted, which resulted in the configuration
file essentially only needing to contain secrets, unless there is a need to
override the defaults. It is not entirely \emph{zero-config} situation, rather
a \emph{minimal-config} one. An example can be seen in
Section~\ref{sec:configuration}.
\n{2}{Embedded assets}
An important thing to mention is embedded assets and templates. Go has multiple
mechanisms to natively embed arbitrary files directly into the binary during
the regular build process. The built-in \texttt{embed} package was used to
bundle all template files and web assets, such as images, logos and stylesheets
at the package level, and these are also the passed around the application as
needed. There is also a toggle in the application configuration, which can
instruct the program at start to either rely entirely on embedded assets or
pull live files from the filesystem. The former option makes the application
more portable, while the latter allows for flexibility not only during
development. Basically, any important value in the program has been made into a
configuration value, so that the operator can customise the experience as
needed. A choice of sane configuration defaults was attempted, which resulted
in the configuration file essentially only needing to contain secrets, unless
there is a need to override the defaults. It is not entirely \emph{zero-config}
situation, rather a \emph{minimal-config} one.
needed.
There is also a toggle in the application configuration, which can instruct the
program at start to either rely entirely on embedded assets or pull live files
from the filesystem. The former option makes the application more portable,
while the latter allows for flexibility not only during development.
\n{2}{Composability}
Templates used for rendering of the web pages were created in a composable
manner, split into smaller, reusable parts, such as \texttt{footer.tmpl} and
@ -924,6 +1102,9 @@ performed ergonomically and directly using Echo's built-in facilities. A
popular HTML sanitiser \emph{bluemonday} has been employed to aid with battling
XSS.
\n{2}{Server-side rendering}
The application constructs the web pages entirely server-side and it runs
without a single line of JavaScript, of which the author is especially proud.
It improves load times, decreases attack surface, increases maintainability and
@ -933,12 +1114,8 @@ updates (where \texttt{PUT}s should be used) and the accompanying frequent
full-page refreshes, but that still is not enough to warrant the use of
JavaScript.
As an aside, the author has briefly experimented with WebAssembly for this
project, but has ultimately scrapped the functionality in favour of the
entirely server-side rendered one. It is possible that it would get revisited
if the client-side dynamic functionality was necessary and performance
mattered. Even from the short experiments it was obvious how much faster
WebAssembly was compared to JavaScript.
\n{2}{Frontend}
Frontend-side, the application was styled using TailwindCSS, which promotes
using of flexible \emph{utility-first} classes in the markup (HTML) instead of
@ -950,61 +1127,112 @@ need to be parsed by Tailwind in order to construct its final stylesheet and
there is also an original CLI tool for that called \texttt{tailwindcss}.
Overall, simple and accessible layouts had preference over convoluted ones.
\n{3}{Frontend experiments}
As an aside, the author has briefly experimented with WebAssembly for this
project, but has ultimately scrapped the functionality in favour of the
entirely server-side rendered one. It is possible that it would get revisited
if the client-side dynamic functionality was necessary and performance
mattered. Even from the short experiments it was obvious how much faster
WebAssembly was compared to JavaScript.
\newpage
\n{2}{User isolation}
Users are allowed into certain parts of the application based on the role they
currently posses. For the moment, two basic roles were envisioned, while this
list might get amended in the future, should the need arise:
\begin{itemize}
\item Administrator
\item User
\end{itemize}
\obr{Application use case diagram}{fig:usecasediagram}{.9}{graphics/pcmt-use-case.pdf}
It is paramount that the program protects itself from the insider threats as
well and therefore each role is only able to perform actions that it is
explicitly assigned. While there definitely is certain overlap between the
capabilities of the two outlined roles, each also possesses unique features
that the other one does not.
For example, the administrator role is not able to perform searches on the
breach data directly using their administrator account, for that a separate
user account has to be devised. Similarly, the regular user is not able to
manage breach lists and other users, because that is a privileged operation.
In-application administrators are not able to view sensitive (any) user data
and should therefore only be able to perform the following actions:
\begin{itemize}
\item Create user accounts
\item View list of users
\item View user email
\item Change user email
\item Toggle whether user is an administrator
\item Delete user accounts
\end{itemize}
Let us consider a case when a user manages self, while demoting from
administrator to a regular user is permitted, promoting self to be an
administrator would constitute a \emph{privilege escalation} and likely be a
precursor to at least a \emph{denial of service} of sorts.
\n{2}{Zero trust principle}
\textit{Confidentiality, i.e.\ not trusting the provider}
There is no way for the application (and consequently, the in-application
administrator) to read user's data. This is possible by virtue of encrypting
the pertinent data before saving them in the database by a state-of-the-art
\emph{age} key~\cite{age} (backed by X25519~\cite{x25519rfc7748}), which is in
turn safely stored encrypted by a passphrase that only the user controls. Of
course, the user-supplied password is run by a password based key derivation
function (PBKDF: a key derivation function with a sliding computational cost)
before letting it encrypt the \emph{age} key.
The \emph{age} key is only generated when the user changes their password for
the first time to prevent scenarios such as in-application administrator with
access to physical database being able to both \textbf{recover} the key from
the database and \textbf{decrypt} it given that they already know the user
password (because they set it), which would subsequently give them unbounded
access to any future encrypted data, as long as they would be able to maintain
their database access. This is why the \emph{age} key generation and protection
are bound to the first password change. Of course, the evil administrator could
just perform the change themselves; however, the user would at least be able to
find those changes in the activity logs and know not to use the application.
But given the scenario of a total database compromise, the author finds all
hope is already lost at that point. At least when the database is dumped, it
only contains non-sensitive, functional information in plain test, everything
else should be encrypted.
Consequently, both the application operators and the in-application
administrators should never be able to learn the details of what the user is
tracking, the same being applicable even to potential attackers with direct
access to the database. Thus the author maintains that every scenario that
could potentially lead to a data breach (apart from a compromised user machine
and the like) would have to entail some form of operating memory acquisition,
for instance using \texttt{LiME}~\cite{lime}, or perhaps directly the
\emph{hypervisor}, if considering a virtualised (``cloud'') environments.
\n{1}{Implementation}
\n{2}{Configuration}
Every non-trivial program usually offers at least \emph{some} way to
tweak/manage its behaviour, and these changes are usually persisted
\emph{somewhere} on the filesystem of the host: in a local SQLite3 database, a
\emph{LocalStorage} key-value store in the browser, a binary or plain text
configuration file. These configuration files need to be read and checked at
least on program start-up and either stored into operating memory for the
duration of the runtime of the program, or loaded and parsed and the memory
subsequently \emph{freed} (initial configuration).
There is an abundance of configuration languages (or file formats used to craft
configuration files, whether they were intended for it or not) available, TOML,
INI, JSON, YAML, to name some of the popular ones (as of today).
Dhall stood out as a language that was designed with both security and the
needs of dynamic configuration scenarios in mind, borrowing a concept or two
from Nix~\cite{nixoslearn}~\cite{nixlang} (which in turn sources more than a
few of its concepts from Haskell), and in its apparent core being very similar
to JSON, which adds to familiar feel. In fact, in Dhall's authors' own words it
is: ``a programmable configuration language that you can think of as: JSON +
functions + types + imports''~\cite{dhalllang}.
Among all of the listed features, the especially intriguing one to the author
was the promise of \emph{types}. There are multiple examples directly on the
project's documentation webpage demonstrating for instance the declaration and
usage of custom types (that are, of course merely combinations of the primitive
types that the language provides, such as \emph{Bool}, \emph{Natural} or
\emph{List}, to name just a few), so it was not exceedingly hard to start
designing a custom configuration \emph{schema} for the program.
Dhall not being a Turing-complete language also guarantees that evaluation
\emph{always} terminates eventually, which is a good attribute to possess as a
configuration language.
\n{3}{Dhall Schema}
\n{2}{Dhall Configuration Schema}\label{sec:configuration}
The configuration schema was at first being developed as part of the main
project's repository, before it was determined that it would benefit both the
development and overall clarity if the schema lived in its own repository (see
Section~\ref{sec:repos} for details). This enabled it to be independently
developed and versioned, and only pulled into the main application whenever it
is determined the application is ready for it.
Section~\ref{sec:repos} for details). This now enables the schema to be
independently developed and versioned, and only pulled into the main
application whenever the application is determined to be ready for it.
The full schema with type annotations can be seen in Listing~\ref{dhallschema}.
The \texttt{let} statement declares a variable called \texttt{Schema} and
assigns it the result of the expression on the right side of the equals sign,
which has for practical reasons been trimmed and is displayed without the
\emph{default} block, which is instead shown in its own
Listing~\ref{dhallschemadefaults}.
\vspace{\parskip}
% \vspace{\parskip}
\smallskip
% \vspace{\baselineskip}
\begin{lstlisting}[language=Haskell, caption={Dhall configuration schema version 0.0.1-rc.2},
label=dhallschema, basicstyle=\linespread{0.9}\footnotesize\ttfamily]
let Schema =
@ -1055,8 +1283,16 @@ let Schema =
\end{lstlisting}
\vspace*{-\baselineskip}
The main configuration is comprised of both raw attributes and child records,
which allow for grouping of related functionality. For instance, configuration
Full schema with type annotations can be seen in Listing~\ref{dhallschema}.
The \texttt{let} statement declares a variable called \texttt{Schema} and
assigns to it the result of the expression on the right side of the equals
sign, which has for practical reasons been trimmed and is displayed without the
\emph{default} block. The default block is instead shown in its own
Listing~\ref{dhallschemadefaults}.
The main configuration comprises both raw attributes and child records, which
allow for grouping of related functionality. For instance, configuration
settings pertaining mailserver setup are grouped in a record named
\textbf{Mailer}. Its attribute \textbf{Enabled} is annotated as \textbf{Bool},
which was deemed appropriate for a on-off switch-like functionality, with the
@ -1067,10 +1303,19 @@ while \textbf{true} is evaluated as an \emph{unbound} variable, that is, a
variable \emph{not} defined in the current \emph{scope} and thus not
\emph{present} in the current scope.
\vspace{\parskip}
Another one of Dhall specialties is that `$==$' and `$!=$' (in)equality
operators \textbf{only} work on values of type \texttt{Bool}, which for example
means that variables of type \texttt{Natural} (\texttt{uint}) or \texttt{Text}
(\texttt{string}) cannot be compared directly as in other languages, which
either leaves the work for a higher-level language (such as Go), or from the
perspective of the Dhall authors, \emph{enums} are promoted when the value
matters.
\newpage
% \vspace{\parskip}
\begin{lstlisting}[language=Haskell, caption={Dhall configuration defaults for
schema version 0.0.1-rc.2},
label=dhallschemadefaults, basicstyle=\linespread{0.9}\scriptsize\ttfamily]
label=dhallschemadefaults, basicstyle=\linespread{0.9}\footnotesize\ttfamily]
, default =
-- | have sane defaults.
{ Host = ""
@ -1122,8 +1367,7 @@ label=dhallschemadefaults, basicstyle=\linespread{0.9}\scriptsize\ttfamily]
, Init =
{ CreateAdmin =
-- | if this is True, attempt to create a user with admin
-- | privileges with the password specified below (or better -
-- | overriden); it fails if users already exist in the DB.
-- | privileges with the password specified below
False
, AdminPassword =
-- | used for the first admin, forced change on first login.
@ -1135,71 +1379,9 @@ label=dhallschemadefaults, basicstyle=\linespread{0.9}\scriptsize\ttfamily]
in Schema
\end{lstlisting}
Another one of specialties of Dhall is that $==$ and $!=$ equality operators
only work on values of type \texttt{Bool}, which for example means that
variables of type \texttt{Natural} (\texttt{uint}) or \texttt{Text}
(\texttt{string}) cannot be compared directly as in other languages, which
either leaves the work for a higher-level language (such as Go), or from the
perspective of the Dhall authors, \emph{enums} are promoted when the value
matters.
\n{3}{Safety considerations}
Having a programmable configuration language that understands functions and
allows importing not only arbitrary text from random internet URLs, but also
importing and \emph{evaluating} (i.e.\ running) potentially untrusted code, it
is important that there are some safety mechanisms employed, which can be
relied on by the user. Dhall offers this in multiple features: enforcing a
same-origin policy and (optionally) pinning a cryptographic hash of the value
of the expression being imported.
\n{3}{Possible alternatives}
While developing the program, the author has also
come across certain shortcomings of Dhall, namely long start-up with \emph{cold
cache}, which can generally be observed in the scenario of running the program
in an environment that does not allow to write the cache files (a read-only
filesystem), of does not keep the written cache files, such as a container that
is not configured to mount a persistent volume at the pertinent location.
To describe the way Dhall works when performing an evaluation, it resolves
every expression down to a combination of its most basic types (eliminating all
abstraction and indirection) in the process called
\textbf{normalisation}~\cite{dhallnorm} and then saves this result in the
host's cache. The \texttt{dhall-haskell} binary attempts to resolve the
variable \texttt{\$\{XDG\_CACHE\_HOME\}} (have a look at \emph{XDG Base
Directory Spec}~\cite{xdgbasedirspec} for details) to decide \emph{where} the
results of the normalisation will be written for repeated use. Do note that
this behaviour has been observed on a GNU/Linux host and the author has not
verified this behaviour on a non-GNU/Linux host, such as FreeBSD.
If normalisation is performed inside an ephemeral container (as opposed to, for
instance, an interactive desktop session), the results effectively get lost on
each container restart, which is both wasteful and not great for user
experience, since the normalisation of just a handful of imports (which
internally branches widely) can take an upwards of two minutes, during which
the user is left waiting for the hanging application with no reporting on the
progress or current status.
While workarounds for the above mentioned problem can be devised relatively
easily (such as bind mounting persistent volumes inside the container in place
of the \texttt{\$\{XDG\_CACHE\_HOME\}/dhall} and
\texttt{\$\{XDG\_CACHE\_HOME\}/dhall-haskell} to preserve the cache between
restarts, or let the cache be pre-computed during container build, since the
application is only really expected to run together with a compatible version
of the configuration schema and this version \emph{is} known at container build
time), it would certainly feel better if there was no need to work
\emph{around} the configuration system of choice.
Alternatives such as CUE (\url{https://cuelang.org/}) offer themselves nicely
as a potentially almost drop-in replacement for Dhall feature-wise, while also
resolving costly \emph{cold cache} normalisation operations, which is in
author's view Dhall's titular issue.
\vspace*{-\baselineskip}
\vspace*{-\baselineskip}
\vspace*{-\baselineskip}
\n{2}{Data integrity and authenticity}
The user can interact with the application via a web client, such as a browser,
@ -1243,194 +1425,20 @@ e.g.\ for tamper protection purposes and similar; however, that work remains
yet to be materialised.
\n{2}{User isolation}
Users are allowed into certain parts of the application based on the role they
currently posses. For the moment, two basic roles were envisioned, while this
list might get amended in the future, if the need arises:
\begin{itemize}
\item Administrator
\item User
\end{itemize}
It is paramount that the program protects itself from the insider threats as
well and therefore each role is only able to perform actions that it is
explicitly assigned. While there definitely is certain overlap between the
capabilities of the two outlined roles, each also possesses unique features
that the other does not.
For example, the administrator role is not able to perform searches on the
breach data directly using their administrator account, for that a separate
user account has to be devised. Similarly, the regular user is not able to
manage breach lists and other users, because that is a privileged operation.
In-application administrators are not able to view sensitive (any) user data
and should therefore only be able to perform the following actions:
\begin{itemize}
\item Create user accounts
\item View list of users
\item View user email
\item Change user email
\item Change user email
\item Toggle whether user is an administrator
\item Delete user accounts
\end{itemize}
Let us consider a case when a user manages self, while demoting from
administrator to a regular user is permitted, promoting self to be an
administrator would constitute a \emph{privilege escalation} and likely be a
precursor to at least a \emph{denial of service} of sorts.
\n{2}{Zero trust principle}
\textit{Data confidentiality, i.e.\ not trusting the provider}
There is no way for the application (and consequently, the in-application
administrator) to read user's data. This is possible by virtue of encrypting
the pertinent data before saving them in the database by a state-of-the-art
\emph{age} key~\cite{age} (backed by X25519~\cite{x25519rfc7748}), which in
turn is safely stored encrypted by a passphrase that only the user controls. Of
course, the user-supplied password is run by a password based key derivation
function (PBKDF: a key derivation function with a sliding computational cost)
before letting it encrypt the \emph{age} key.
The \emph{age} key is only generated when the user changes their password for
the first time to prevent scenarios such as in-application administrator with
access to physical database being able to both \textbf{recover} the key from
the database and \textbf{decrypt} it given that they already know the user
password (because they set it), which would subsequently give them unbounded
access to any future encrypted data, as long as they would be able to maintain
their database access. This is why the \emph{age} key generation and protection
are bound to the first password change. Of course, the evil administrator could
just perform the change themselves; however, the user would at least be able to
find those changes in the activity logs and know not to use the application.
But given the scenario of a total database compromise, the author finds all
hope is already lost at that point. At least when the database is dumped, it
only contains non-sensitive, functional information in plain test, everything
else should be encrypted.
Consequently, both the application operators and the in-application
administrators should never be able to learn the details of what the user is
tracking, the same being applicable even to potential attackers with direct
access to the database. Thus the author maintains that every scenario that
could potentially lead to a data breach (apart from a compromised user machine
and the like) would have to entail some form of operating memory acquisition,
for instance using \texttt{LiME}~\cite{lime}, or perhaps directly the
\emph{hypervisor}, if considering a virtualised (``cloud'') environments.
\n{2}{Compromise Monitoring}
\n{3}{Have I Been Pwned? Integration}
Troy Hunt's Have I Been Pwned? online service
(\url{https://haveibeenpwned.com/}) has been chosen as the online source of
compromised data. The service offers private APIs that are protected by API
keys. The application's \texttt{hibp} module and database representation models
the values returned by this API, which allows searching in large breaches using
email addresses.\\
The architecture there is relatively simple: the application administrator
configures an API key for HIBP, the user enters the query parameters, the
application constructs a query and calls the API and waits for a response. As
the API is rate-limited based on the key supplied, this can pose an issue and
it has not been fully resolved in the UI. The application then parses the
returned data and binds it to the local model for validation. If that goes
well, the data is saved into the database as a cache and the search query is
performed on the saved data. If it returns anything, it is displayed to the
user for browsing.
\n{3}{Local Dataset Plugin} Breach data from locally available datasets can be
imported into the application by first making sure it adheres to the specified
schema (have a look at the \emph{breach data schema} in
Listing~\ref{breachDataGoSchema}). If it doesn't (which is very likely with
random breach data), it needs to be converted to a form that does before
importing it to the application, e.g.\ using a Python script or similar.
Attempting to import data that does not follow the outlined schema would result
in an error. Also, importing a dataset which is over a reasonable size limit
would by default be rejected by the program as a precaution, since marshaling
e.g.\ a 1 TiB document would likely result in an OOM situation on the host,
assuming regular consumer hardware conditions, not HPC.
\vspace{\parskip}
\begin{lstlisting}[language=Go, caption={Breach Data Schema represented as a Go struct with imports from the standard library are assumed},
label=breachDataGoSchema]
type breachDataSchema struct {
Name string
Time time.Time
IsVerified bool
ContainsPasswords bool
ContainsHashes bool
HashType string
HashSalted bool
HashPepperred bool
ContainsUsernames bool
ContainsEmails bool
Data any
}
\end{lstlisting}
\vspace*{-\baselineskip}
The Go representation shown in Listing~\ref{breachDataGoSchema} will in
actuality be written and supplied by the user of the program as a YAML
document. YAML was chosen for multiple reasons: relative ease of use (plain
text, readable, support for inclusion of comments, its capability to store
multiple \emph{documents} inside of a single file with most of the inputs
implicitly typed as strings while thanks to being a superset of JSON it sports
machine readability. That should allow for documents similar to what can be
seen in Listing~\ref{breachDataYAMLSchema} to be ingested by the program,
read and written by humans and programs alike.
\smallskip
\begin{lstlisting}[language=YAML, caption={Example Breach Data Schema supplied
to the program as a YAML file, optionally containing multiple documents},
label=breachDataYAMLSchema]
---
name: Horrible breach
time: 2022-04-23T00:00:00Z+02:00
isVerified: false
containsPasswds: false
containsHashes: true
containsEmails: true
hashType: md5
hashSalted: false
hashPeppered: false
data:
hashes:
- hash1
- hash2
- hash3
emails:
- email1
-
- email3
---
# document #2, describing another breach.
name: Horrible breach 2
...
\end{lstlisting}
\vspace*{-\baselineskip}
Notice how the emails list in Listing~\ref{breachDataYAMLSchema} misses one
record, perhaps because it was not supplied or mistakenly omitted. This is a
valid scenario (mistakes happen) and the application needs to be able to handle
it. The alternative would be to require the user to prepare the data in such a
way that the empty/partial records would be dropped entirely.
\n{2}{Database configuration}
\n{2}{Database schema}\label{sec:dbschema}
The database schema is not being created manually in the database. Instead, an
Object-relational Mapping (ORM) tool named ent is used, which allows defining
the table schema and relations entirely in Go.
the table schema and relations entirely in Go. The application does not need
for the database schema to be pre-created when the application starts, it only
requires a connection string providing access to the database for a reasonably
privileged user if that is the case.
The best part about ent is that there is no need to define supplemental methods
on the models, since with ent these are meant to be \emph{code generated} (in
the older sense of word, not with Large Language Models). That creates files
with models based on the types of the attributes in the database model, and the
The best part about \texttt{ent} is that there is no need to define
supplemental methods on the models, as with \texttt{ent} these are meant to be
\emph{code generated} (in the older sense of word, not with Large Language
Models) into existence. Code generation creates files with actual Go models
based on the types of the attributes in the database schema model, and the
respective relations are transformed into methods on the receiver or functions
taking object attributes as arguments.
@ -1449,90 +1457,164 @@ These methods can further be imported into other packages and this makes
working with the database a morning breeze.
\n{1}{Production}
\n{1}{Deployment}
It is, of course, recommended that the application runs in a secure environment
\allowbreak although definitions of that almost certainly differ depending on
who you ask. General recommendations would be either to effectively reserve a
machine for a single use case - running this program - so as to dramatically
decrease the potential attack surface of the host, or run the program isolated
in a container or a virtual machine. Further, if the host does not need
management access (it is a deployed-to-only machine that is configured
out-of-band, such as with a \emph{golden} image/container or declaratively with
Nix), then an SSH \emph{daemon} should not be running in it, since it is not
needed. In an ideal scenario, the host machine would have as little software
installed as possible besides what the application absolutely requires.
\textbf{TODO}: mention how \texttt{systemd} aids in running the pod.
A demonstration of the above can be found in the multi-stage Containerfile that
is available in the main sources. The resulting container image only contains a
statically linked copy of the program, a default configuration file and
corresponding Dhall expressions cached at build time, which only support the
main configuration file. Since the program also needs a database, an example
scenario could include the container being run in a Podman pod together with
the database, which would not have to be exposed from the pod and would
therefore only be available over \texttt{localhost}.
A deployment setup as suggested in Section~\ref{sec:deploymentRecommendations}
is already partially covered by the multi-stage \texttt{Containerfile} that is
available in the main sources. Once built, the resulting container image only
contains a handful of things it absolutely needs:
It goes without saying that the operator should substitute values of any
default configuration secrets with the new ones that were securely generated.
\begin{itemize}
\item a statically linked copy of the program
\item a default configuration file and corresponding Dhall expressions cached
at build time
\item a recent CA certs bundle
\end{itemize}
System-wide cryptographic policies should target highest feasible security
level, if at all available (such as by default on Fedora or RHEL), covering
SSH, DNSSec, IPsec, Kerberos and TLS protocols. Firewalls should be configured
and SELinux (kernel-level mandatory access control and security policy
mechanism) running in \emph{enforcing} mode, if available.
Since the program also needs a database for proper functioning, an example
scenario includes the application container being run in a Podman \textbf{pod}
together with the database. That results in not having to expose the database
to the entire host or out of the pod at all, it is only be available over pod's
\texttt{localhost}.
It goes without saying that the default values of any configuration secrets
should be substituted by the application operator with new, securely generated
ones.
\n{2}{Deployment recommendations}
\n{2}{Rootless Podman}
\n{3}{Transport security}
Assuming rootless Podman set up and the \texttt{just} tool installed on the
host, the application could be deployed by following a series of relatively
simple steps:
User connecting to the application should rightfully expect for their data to
be protected \textit{in transit} (i.e.\ on the way between their browser and
the server), which is what \emph{Transport Layer Security} family of
protocols~\cite{tls13rfc8446} was designed for, and which is the underpinning
of HTTPS. TLS utilises the primitives of asymmetric cryptography to let the
client authenticate the server (verify that it is who it claims it is) and
negotiate a symmetric key for encryption in the process named the \emph{TLS
handshake} (see Section~\ref{sec:tls} for more details), the final purpose of
which is establishing a secure communications connection. The operator should
configure the program to either directly utilise TLS using configuration or
have it listen behind a TLS-terminating \emph{reverse proxy}.
\begin{itemize}
\item build (or pull) the application container image
\item create a pod with user namespacing, exposing the application port
\item run the database container inside the pod
\item run the application inside the pod
\end{itemize}
In concrete terms, it would resemble something along the lines of
Listing~\ref{podmanDeployment}. Do note that all the commands are executed
under the unprivileged \texttt{user@containerHost} that is running rootless
Podman, i.e.\ it has \texttt{UID}/\texttt{GID} mapping entries in
\texttt{/etc/setuid} and \texttt{\etc/setgid} files \textbf{prior} to running any
Podman commands.
\n{3}{Containerisation}
Whether the pre-built or a custom container image is used to deploy the
application, it still needs access to secrets, such as database connection
string (containing database host, port, user, password/encrypted password,
authentication method and database name).
% \newpage
Currently, the application is able to handle \emph{peer}, \emph{scram-sha-256},
\emph{user name maps} and raw \emph{password} as Postgres authentication
methods~\cite{pgauthmethods}, although the \emph{password} option should not be
used in production, \emph{unless} the connection to the database is protected
by TLS.\ In any case, using the \emph{scram-sha-256}~\cite{scramsha256rfc7677}
method is preferable and one way to verify in development environment that
everything works as intended is the \emph{Password generator for PostgreSQL}
tool~\cite{goscramsha256}, which allows to get the encrypted string from a raw
user input.
\begin{lstlisting}[language=bash, caption={Example application deployment using
rootless Podman},
label=podmanDeployment, basicstyle=\linespread{0.9}\small\ttfamily]
# From inside the project folder, build the image locally using kaniko.
just kaniko
If the application running in a container wants to use the \emph{peer}
authentication method, it is up to the operator to supply the Postgres socket
to the application (e.g.\ as a volume bind mount). This scenario was not
tested; however, and the author is also not entirely certain how \emph{user
namespaces} (on GNU/Linux) would influence the process (given that the
\emph{ID}s of a user \textbf{outside} the container are mapped to a range of
\emph{UIDs} \textbf{inside} the container), for which the setup would likely
need to account.
# Create a pod.
podman pod create --userns=keep-id -p3005:3000 --name pcmt
Equally, if the application is running inside the container, the operator needs
to make sure that the database is either running in a network that is also
directly attached to the container or that there is a mechanism in place that
routes the requests for the database hostname to the destination.
# Run the database in the pod.
podman run --pod pcmt --replace -d --name "pcmt-pg" --rm \
-e POSTGRES_INITDB_ARGS="--auth-host=scram-sha-256 \
--auth-local=scram-sha-256" \
-e POSTGRES_PASSWORD=postgres -v $PWD/tmp/db:/var/lib/postgresql/data \
docker.io/library/postgres:15.2-alpine3.17
One such mechanism is container name based routing inside \emph{pods}
(Podman/Kubernetes), where the resolution of container names is the
responsibility of a specially configured piece of software called Aardvark for
the former and CoreDNS for the latter.
# Run the application in the pod.
podman run --pod pcmt --replace --name pcmt-og -d --rm \
-e PCMT_LIVE=False \
-e PCMT_DBTYPE="postgres" \
-e PCMT_CONNSTRING="host=pcmt-pg port=5432 sslmode=disable \
user=postgres dbname=postgres password=postgres"
-v $PWD/config.dhall:/config.dhall:ro \
docker.io/immawanderer/pcmt:testbuild -config /config.dhall
\end{lstlisting}
To summarise Listing~\ref{podmanDeployment}, first, the application
container is built from inside the project folder using \texttt{kaniko}.
Alternatively, the container image could be pulled from the container
repository, but it makes more sense showing the image being built from sources
since the listing depicts a \texttt{:testbuild} tag being used.
Next, a \emph{pod} is created and given a name, setting the port binding for
the application. Then, the database container is started inside the pod.
As a final step, the application container itself is run inside the pod. The application configuration named \texttt{config.dhall} located in
\texttt{\$PWD} is mounted as a volume into container's \texttt{/config.dhall},
providing the application with a default configuration. The default container
does contain a default configuration for reference, however, running the
container as is without additional configuration would fail as it does not
contain the necessary secrets.
\n{3}{Sanity checks}
Do also note that the application connects to the database using its
\emph{container} name, i.e.\ not the IP address. That is possible thanks to
Podman setting up DNS inside the pod in such a way that all containers in the
pod can reach each other using their (container) names. Interestingly,
connecting via \texttt{localhost} would also work, as from inside the pod, any
container in the pod can reach any other container in the same pod via pod's
\texttt{localhost}.
In fact, \emph{pinging} the database or application containers from an ad-hoc
\texttt{alpine} container added to the pod yields:
\vspace{\parskip}
\begin{lstlisting}[language=bash, caption={Pinging pod containers using their
names}, label=podmanPing, basicstyle=\linespread{0.9}\small\ttfamily]
user@containerHost % podman run --rm -it --user=0 --pod=pcmt \
docker.io/library/alpine:3.18
/ # ping -c2 pcmt-og
PING pcmt-og (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: seq=0 ttl=42 time=0.072 ms
64 bytes from 127.0.0.1: seq=1 ttl=42 time=0.118 ms
--- pcmt-og ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.072/0.095/0.118 ms
/ # ping -c2 pcmt-pg
PING pcmt-pg (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: seq=0 ttl=42 time=0.045 ms
64 bytes from 127.0.0.1: seq=1 ttl=42 time=0.077 ms
--- pcmt-pg ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.045/0.061/0.077 ms
/ #
\end{lstlisting}
\vspace*{-\baselineskip}
The pod created in Listing~\ref{podmanDeployment} only set the binding for a
port used by the application (\texttt{5005/tcp}). The Postgres default port
\texttt{5432/tcp} is not among pod's port bindings, as can be seen in the pod
creation command. This can also easily be verified using the command in
Listing~\ref{podmanPortBindings}:
\begin{lstlisting}[language=bash, caption={Podman pod port bindings},
label=podmanPortBindings, basicstyle=\linespread{0.9}\small\ttfamily]
user@containerHost % podman pod inspect pcmt \
--format="Port bindings: {{.InfraConfig.PortBindings}}\n\
Host network: {{.InfraConfig.HostNetwork}}"
Port bindings: map[3000/tcp:[{ 5005}]]
Host network: false
\end{lstlisting}
\vspace*{-\baselineskip}
To be absolutely sure, trying to connect to the database from outside of the
pod (i.e. from the container host) should \emph{fail}, unless, of course, there
is another process listening on that port:
\begin{lstlisting}[language=bash, caption={In-pod database is unreachable from
the host}, breaklines=true, label=podDbUnreachable,
basicstyle=\linespread{0.9}\small\ttfamily]
user@containerHost % curl localhost:5432
--> curl: (7) Failed to connect to localhost port 5432 after 0 ms: Couldn't connect to server
\end{lstlisting}
\vspace*{-\baselineskip}
The error in Listing~\ref{podDbUnreachable} is expected, as it is the result of
the database port not been exposed from the pod.
\n{1}{Validation}
@ -1541,19 +1623,15 @@ the former and CoreDNS for the latter.
Unit testing is a hot topic for many people and the author does not count
himself to be a staunch supporter of neither extreme. The ``no unit tests''
seems to discount any benefit there is to unit testing, while a `` TDD-only''
(TDD, or Test Driven Development is a development methodology whereby tests are
written first, then a complementary piece of code that is supposed to be
tested, just enough to get past the compile errors and to see the test fail,
then the code is refactored to make the test pass and then it can be fearlessly
extended because the test is the safety net catching us when the user slips and
alters the originally intended behaviour) approach can be a little too much for
some people's taste. The author tends to sport a \emph{middle ground} approach
here, with writing enough tests where meaningful but not necessarily testing
everything or writing tests prior to code, although arguably that practice
should result in writing a \emph{better} designed code, particularly because
there has to be a prior though about it because it needs to be tested
\emph{first}.
seems to discount any benefit there is to unit testing, while a ``
TDD-only''\footnotemark{} approach can be a little too much for some people's
taste. The author tends to prefer a \emph{middle ground} approach in this
particular case, i.e. writing enough tests where meaningful but not necessarily
testing everything or writing tests prior to business logic code. Arguably,
following the practice of TDD should result in writing a \emph{better designed}
code, particularly because there needs to be a prior thought about the shape
and function of the code, as it is tested for before it is even written, but it
adds an slight inconvenience to what is otherwise a straightforward process.
Thanks to Go's built in support for testing via its \texttt{testing} package
and the tooling in the \texttt{go} tool, writing tests is relatively simple. Go
@ -1578,6 +1656,15 @@ informing the developer that no tests were found, which is handy to learn if it
was not intended/expected. When compiling regular source code, the Go files
with \texttt{\_test} in the name are simply ignored by the build tool.
\footnotetext{TDD, or Test Driven Development, is a development methodology
whereby tests are written \emph{first}, then a complementary piece of code
that is supposed to be tested is added, just enough to get past the compile
errors and to see the test \emph{fail} and then is the code finally
refactored to make the test \emph{pass}. The code can then be fearlessly
extended because the test is the safety net catching the programmer when the
mind slips and alters the originally intended behaviour of the code.}
\n{2}{Integration tests}
Integrating with external software, namely the database in case of this
@ -1724,26 +1811,29 @@ by \emph{Let's Encrypt}\allowbreak issued, short-lived, ECDSA
a testing instance; therefore, limits to prevent abuse might be imposed.
\n{3}{Deployment validation}
TODO: show the results of testing the app in prod using
\url{https://testssl.sh/}.
% =========================================================================== %
\nn{Conclusion}
The objectives of the thesis have been to create the Password Compromise
Monitoring Tool aimed at security-conscious user in order to validate their
assumptions on the security of their credentials. The thesis opened by
introducing common terminology and continued with a dive into cryptography
topics such as encryption, Diffie-Hellman key distribution scheme and briefly
mentioned TLS. Furthermore, it discussed the inner workings of browsers and the
protocols that underpin them.
assumptions on the security of their credentials. The thesis opened by diving
into cryptography topics such as encryption and briefly mentioned TLS.
Additionally, security mechanisms such as Site Isolation and Content Security
Policy, commonly employed by mainstream browsers of today, were
introduced and the reader learnt how Content Security Policy is easily and
dynamically configured.
Policy, commonly employed by mainstream browsers of today, were introduced and
the reader learnt how Content Security Policy is easily and dynamically
configured.
An extensive body of the thesis then revolved around the practical part,
describing everything from tooling used through application high-level-view
architecture to implementation of specific parts of the application across the
stack.
describing everything from tooling used through high-level view of
application's architecture to implementation of specific parts of the
application across the stack.
Finally, the practical part concluded by broadly depicting validation
methods used to verify if the application worked correctly.