git/credential.c

#include "git-compat-util.h"
#include "abspath.h"
#include "config.h"
#include "credential.h"
#include "gettext.h"
#include "string-list.h"
#include "run-command.h"
#include "url.h"
#include "prompt.h"
#include "sigchain.h"
#include "strbuf.h"
#include "urlmatch.h"
#include "git-compat-util.h"

void credential_init(struct credential *c)
{
	struct credential blank = CREDENTIAL_INIT;
	memcpy(c, &blank, sizeof(*c));
}

void credential_clear(struct credential *c)
{
	free(c->protocol);
	free(c->host);
	free(c->path);
	free(c->username);
	free(c->password);
	string_list_clear(&c->helpers, 0);
	strvec_clear(&c->wwwauth_headers);

	credential_init(c);
}

int credential_match(const struct credential *want,
		     const struct credential *have)
{
#define CHECK(x) (!want->x || (have->x && !strcmp(want->x, have->x)))
	return CHECK(protocol) &&
	       CHECK(host) &&
	       CHECK(path) &&
	       CHECK(username);
#undef CHECK
}


static int credential_from_potentially_partial_url(struct credential *c,
						   const char *url);

static int credential_config_callback(const char *var, const char *value,
				      void *data)
{
	struct credential *c = data;
	const char *key;

	if (!skip_prefix(var, "credential.", &key))
		return 0;

	if (!value)
		return config_error_nonbool(var);

	if (!strcmp(key, "helper")) {
		if (*value)
			string_list_append(&c->helpers, value);
		else
			string_list_clear(&c->helpers, 0);
	} else if (!strcmp(key, "username")) {
		if (!c->username_from_proto) {
			free(c->username);
			c->username = xstrdup(value);
		}
	}
	else if (!strcmp(key, "usehttppath"))
		c->use_http_path = git_config_bool(var, value);

	return 0;
}

static int proto_is_http(const char *s)
{
	if (!s)
		return 0;
	return !strcmp(s, "https") || !strcmp(s, "http");
}

static void credential_describe(struct credential *c, struct strbuf *out);
static void credential_format(struct credential *c, struct strbuf *out);

static int select_all(const struct urlmatch_item *a,
		      const struct urlmatch_item *b)
{
	return 0;
}

static int match_partial_url(const char *url, void *cb)
{
	struct credential *c = cb;
	struct credential want = CREDENTIAL_INIT;
	int matches = 0;

	if (credential_from_potentially_partial_url(&want, url) < 0)
		warning(_("skipping credential lookup for key: credential.%s"),
			url);
	else
		matches = credential_match(&want, c);
	credential_clear(&want);

	return matches;
}

static void credential_apply_config(struct credential *c)
{
	char *normalized_url;
	struct urlmatch_config config = URLMATCH_CONFIG_INIT;
	struct strbuf url = STRBUF_INIT;

	if (!c->host)
		die(_("refusing to work with credential missing host field"));
	if (!c->protocol)
		die(_("refusing to work with credential missing protocol field"));

	if (c->configured)
		return;

	config.section = "credential";
	config.key = NULL;
	config.collect_fn = credential_config_callback;
	config.cascade_fn = NULL;
	config.select_fn = select_all;
	config.fallback_match_fn = match_partial_url;
	config.cb = c;

	credential_format(c, &url);
	normalized_url = url_normalize(url.buf, &config.url);

	git_config(urlmatch_config_entry, &config);
	string_list_clear(&config.vars, 1);
	free(normalized_url);
	urlmatch_config_release(&config);
	strbuf_release(&url);

	c->configured = 1;

	if (!c->use_http_path && proto_is_http(c->protocol)) {
		FREE_AND_NULL(c->path);
	}
}

static void credential_describe(struct credential *c, struct strbuf *out)
{
	if (!c->protocol)
		return;
	strbuf_addf(out, "%s://", c->protocol);
	if (c->username && *c->username)
		strbuf_addf(out, "%s@", c->username);
	if (c->host)
		strbuf_addstr(out, c->host);
	if (c->path)
		strbuf_addf(out, "/%s", c->path);
}

static void credential_format(struct credential *c, struct strbuf *out)
{
	if (!c->protocol)
		return;
	strbuf_addf(out, "%s://", c->protocol);
	if (c->username && *c->username) {
		strbuf_add_percentencode(out, c->username, STRBUF_ENCODE_SLASH);
		strbuf_addch(out, '@');
	}
	if (c->host)
		strbuf_addstr(out, c->host);
	if (c->path) {
		strbuf_addch(out, '/');
		strbuf_add_percentencode(out, c->path, 0);
	}
}

static char *credential_ask_one(const char *what, struct credential *c,
				int flags)
{
	struct strbuf desc = STRBUF_INIT;
	struct strbuf prompt = STRBUF_INIT;
	char *r;

	credential_describe(c, &desc);
	if (desc.len)
		strbuf_addf(&prompt, "%s for '%s': ", what, desc.buf);
	else
		strbuf_addf(&prompt, "%s: ", what);

	r = git_prompt(prompt.buf, flags);

	strbuf_release(&desc);
	strbuf_release(&prompt);
	return xstrdup(r);
}

static void credential_getpass(struct credential *c)
{
	if (!c->username)
		c->username = credential_ask_one("Username", c,
						 PROMPT_ASKPASS|PROMPT_ECHO);
	if (!c->password)
		c->password = credential_ask_one("Password", c,
						 PROMPT_ASKPASS);
}

int credential_read(struct credential *c, FILE *fp)
{
	struct strbuf line = STRBUF_INIT;

	while (strbuf_getline(&line, fp) != EOF) {
		char *key = line.buf;
		char *value = strchr(key, '=');

		if (!line.len)
			break;

		if (!value) {
			warning("invalid credential line: %s", key);
			strbuf_release(&line);
			return -1;
		}
		*value++ = '\0';

		if (!strcmp(key, "username")) {
			free(c->username);
			c->username = xstrdup(value);
			c->username_from_proto = 1;
		} else if (!strcmp(key, "password")) {
			free(c->password);
			c->password = xstrdup(value);
		} else if (!strcmp(key, "protocol")) {
			free(c->protocol);
			c->protocol = xstrdup(value);
		} else if (!strcmp(key, "host")) {
			free(c->host);
			c->host = xstrdup(value);
		} else if (!strcmp(key, "path")) {
			free(c->path);
			c->path = xstrdup(value);
		} else if (!strcmp(key, "wwwauth[]")) {
			strvec_push(&c->wwwauth_headers, value);
		} else if (!strcmp(key, "password_expiry_utc")) {
			errno = 0;
			c->password_expiry_utc = parse_timestamp(value, NULL, 10);
			if (c->password_expiry_utc == 0 || errno == ERANGE)
				c->password_expiry_utc = TIME_MAX;
		} else if (!strcmp(key, "url")) {
			credential_from_url(c, value);
		} else if (!strcmp(key, "quit")) {
			c->quit = !!git_config_bool("quit", value);
		}
		/*
		 * Ignore other lines; we don't know what they mean, but
		 * this future-proofs us when later versions of git do
		 * learn new lines, and the helpers are updated to match.
		 */
	}

	strbuf_release(&line);
	return 0;
}

static void credential_write_item(FILE *fp, const char *key, const char *value,
				  int required)
{
	if (!value && required)
		BUG("credential value for %s is missing", key);
	if (!value)
		return;
	if (strchr(value, '\n'))
		die("credential value for %s contains newline", key);
	fprintf(fp, "%s=%s\n", key, value);
}

void credential_write(const struct credential *c, FILE *fp)
{
	credential_write_item(fp, "protocol", c->protocol, 1);
	credential_write_item(fp, "host", c->host, 1);
	credential_write_item(fp, "path", c->path, 0);
	credential_write_item(fp, "username", c->username, 0);
	credential_write_item(fp, "password", c->password, 0);
	if (c->password_expiry_utc != TIME_MAX) {
		char *s = xstrfmt("%"PRItime, c->password_expiry_utc);
		credential_write_item(fp, "password_expiry_utc", s, 0);
		free(s);
	}
	for (size_t i = 0; i < c->wwwauth_headers.nr; i++)
		credential_write_item(fp, "wwwauth[]", c->wwwauth_headers.v[i], 0);
}

static int run_credential_helper(struct credential *c,
				 const char *cmd,
				 int want_output)
{
	struct child_process helper = CHILD_PROCESS_INIT;
	FILE *fp;

	strvec_push(&helper.args, cmd);
	helper.use_shell = 1;
	helper.in = -1;
	if (want_output)
		helper.out = -1;
	else
		helper.no_stdout = 1;

	if (start_command(&helper) < 0)
		return -1;

	fp = xfdopen(helper.in, "w");
	sigchain_push(SIGPIPE, SIG_IGN);
	credential_write(c, fp);
	fclose(fp);
	sigchain_pop(SIGPIPE);

	if (want_output) {
		int r;
		fp = xfdopen(helper.out, "r");
		r = credential_read(c, fp);
		fclose(fp);
		if (r < 0) {
			finish_command(&helper);
			return -1;
		}
	}

	if (finish_command(&helper))
		return -1;
	return 0;
}

static int credential_do(struct credential *c, const char *helper,
			 const char *operation)
{
	struct strbuf cmd = STRBUF_INIT;
	int r;

	if (helper[0] == '!')
		strbuf_addstr(&cmd, helper + 1);
	else if (is_absolute_path(helper))
		strbuf_addstr(&cmd, helper);
	else
		strbuf_addf(&cmd, "git credential-%s", helper);

	strbuf_addf(&cmd, " %s", operation);
	r = run_credential_helper(c, cmd.buf, !strcmp(operation, "get"));

	strbuf_release(&cmd);
	return r;
}

void credential_fill(struct credential *c)
{
	int i;

	if (c->username && c->password)
		return;

	credential_apply_config(c);

	for (i = 0; i < c->helpers.nr; i++) {
		credential_do(c, c->helpers.items[i].string, "get");
		if (c->password_expiry_utc < time(NULL)) {
			/* Discard expired password */
			FREE_AND_NULL(c->password);
			/* Reset expiry to maintain consistency */
			c->password_expiry_utc = TIME_MAX;
		}
		if (c->username && c->password)
			return;
		if (c->quit)
			die("credential helper '%s' told us to quit",
			    c->helpers.items[i].string);
	}

	credential_getpass(c);
	if (!c->username && !c->password)
		die("unable to get password from user");
}

void credential_approve(struct credential *c)
{
	int i;

	if (c->approved)
		return;
	if (!c->username || !c->password || c->password_expiry_utc < time(NULL))
		return;

	credential_apply_config(c);

	for (i = 0; i < c->helpers.nr; i++)
		credential_do(c, c->helpers.items[i].string, "store");
	c->approved = 1;
}

void credential_reject(struct credential *c)
{
	int i;

	credential_apply_config(c);

	for (i = 0; i < c->helpers.nr; i++)
		credential_do(c, c->helpers.items[i].string, "erase");

	FREE_AND_NULL(c->username);
	FREE_AND_NULL(c->password);
	c->password_expiry_utc = TIME_MAX;
	c->approved = 0;
}

static int check_url_component(const char *url, int quiet,
			       const char *name, const char *value)
{
	if (!value)
		return 0;
	if (!strchr(value, '\n'))
		return 0;

	if (!quiet)
		warning(_("url contains a newline in its %s component: %s"),
			name, url);
	return -1;
}

/*
 * Potentially-partial URLs can, but do not have to, contain
 *
 * - a protocol (or scheme) of the form "<protocol>://"
 *
 * - a host name (the part after the protocol and before the first slash after
 *   that, if any)
 *
 * - a user name and potentially a password (as "<user>[:<password>]@" part of
 *   the host name)
 *
 * - a path (the part after the host name, if any, starting with the slash)
 *
 * Missing parts will be left unset in `struct credential`. Thus, `https://`
 * will have only the `protocol` set, `example.com` only the host name, and
 * `/git` only the path.
 *
 * Note that an empty host name in an otherwise fully-qualified URL (e.g.
 * `cert:///path/to/cert.pem`) will be treated as unset if we expect the URL to
 * be potentially partial, and only then (otherwise, the empty string is used).
 *
 * The credential_from_url() function does not allow partial URLs.
 */
static int credential_from_url_1(struct credential *c, const char *url,
				 int allow_partial_url, int quiet)
{
	const char *at, *colon, *cp, *slash, *host, *proto_end;

	credential_clear(c);

	/*
	 * Match one of:
	 *   (1) proto://<host>/...
	 *   (2) proto://<user>@<host>/...
	 *   (3) proto://<user>:<pass>@<host>/...
	 */
	proto_end = strstr(url, "://");
	if (!allow_partial_url && (!proto_end || proto_end == url)) {
		if (!quiet)
			warning(_("url has no scheme: %s"), url);
		return -1;
	}
	cp = proto_end ? proto_end + 3 : url;
	at = strchr(cp, '@');
	colon = strchr(cp, ':');

	/*
	 * A query or fragment marker before the slash ends the host portion.
	 * We'll just continue to call this "slash" for simplicity. Notably our
	 * "trim leading slashes" part won't skip over this part of the path,
	 * but that's what we'd want.
	 */
	slash = cp + strcspn(cp, "/?#");

	if (!at || slash <= at) {
		/* Case (1) */
		host = cp;
	}
	else if (!colon || at <= colon) {
		/* Case (2) */
		c->username = url_decode_mem(cp, at - cp);
		if (c->username && *c->username)
			c->username_from_proto = 1;
		host = at + 1;
	} else {
		/* Case (3) */
		c->username = url_decode_mem(cp, colon - cp);
		if (c->username && *c->username)
			c->username_from_proto = 1;
		c->password = url_decode_mem(colon + 1, at - (colon + 1));
		host = at + 1;
	}

	if (proto_end && proto_end - url > 0)
		c->protocol = xmemdupz(url, proto_end - url);
	if (!allow_partial_url || slash - host > 0)
		c->host = url_decode_mem(host, slash - host);
	/* Trim leading and trailing slashes from path */
	while (*slash == '/')
		slash++;
	if (*slash) {
		char *p;
		c->path = url_decode(slash);
		p = c->path + strlen(c->path) - 1;
		while (p > c->path && *p == '/')
			*p-- = '\0';
	}

	if (check_url_component(url, quiet, "username", c->username) < 0 ||
	    check_url_component(url, quiet, "password", c->password) < 0 ||
	    check_url_component(url, quiet, "protocol", c->protocol) < 0 ||
	    check_url_component(url, quiet, "host", c->host) < 0 ||
	    check_url_component(url, quiet, "path", c->path) < 0)
		return -1;

	return 0;
}

static int credential_from_potentially_partial_url(struct credential *c,
						   const char *url)
{
	return credential_from_url_1(c, url, 1, 0);
}

int credential_from_url_gently(struct credential *c, const char *url, int quiet)
{
	return credential_from_url_1(c, url, 0, quiet);
}

void credential_from_url(struct credential *c, const char *url)
{
	if (credential_from_url_gently(c, url, 0) < 0)
		die(_("credential url cannot be parsed: %s"), url);
}