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sha1dc: allow building with the external sha1dc library

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Some distros provide SHA1 collision-detect code as a shared library.
It's the same code as we have in git tree (but may be with a different
init default for hash), and git can link with it as well; at least, it
may make maintenance easier, according to our security guys.

This patch allows user to build git linking with the external sha1dc
library instead of the built-in code.  User needs to define
DC_SHA1_EXTERNAL explicitly.  As default without it, the built-in
sha1dc code is used like before.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Takashi Iwai 2017-08-15 14:04:17 +02:00 committed by Junio C Hamano
parent 36f048c5e4
commit 3964cbbb5c
3 changed files with 33 additions and 1 deletions
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13
Makefile
View File

@ -162,6 +162,11 @@ all::
# algorithm. This is slower, but may detect attempted collision attacks.
# Takes priority over other *_SHA1 knobs.
#
# Define DC_SHA1_EXTERNAL in addition to DC_SHA1 if you want to build / link
# git with the external SHA1 collision-detect library.
# Without this option, i.e. the default behavior is to build git with its
# own built-in code (or submodule).
#
# Define DC_SHA1_SUBMODULE in addition to DC_SHA1 to use the
# sha1collisiondetection shipped as a submodule instead of the
# non-submodule copy in sha1dc/. This is an experimental option used
@ -1474,6 +1479,13 @@ else
DC_SHA1 := YesPlease
BASIC_CFLAGS += -DSHA1_DC
LIB_OBJS += sha1dc_git.o
ifdef DC_SHA1_EXTERNAL
ifdef DC_SHA1_SUBMODULE
$(error Only set DC_SHA1_EXTERNAL or DC_SHA1_SUBMODULE, not both)
endif
BASIC_CFLAGS += -DDC_SHA1_EXTERNAL
EXTLIBS += -lsha1detectcoll
else
ifdef DC_SHA1_SUBMODULE
LIB_OBJS += sha1collisiondetection/lib/sha1.o
LIB_OBJS += sha1collisiondetection/lib/ubc_check.o
@ -1491,6 +1503,7 @@ endif
endif
endif
endif
endif
ifdef SHA1_MAX_BLOCK_SIZE
LIB_OBJS += compat/sha1-chunked.o

11
sha1dc_git.c
View File

@ -1,5 +1,16 @@
#include "cache.h"
#ifdef DC_SHA1_EXTERNAL
/*
* Same as SHA1DCInit, but with default save_hash=0
*/
void git_SHA1DCInit(SHA1_CTX *ctx)
{
SHA1DCInit(ctx);
SHA1DCSetSafeHash(ctx, 0);
}
#endif
/*
* Same as SHA1DCFinal, but convert collision attack case into a verbose die().
*/

10
sha1dc_git.h
View File

@ -2,14 +2,22 @@
#ifdef DC_SHA1_SUBMODULE
#include "sha1collisiondetection/lib/sha1.h"
#elif defined(DC_SHA1_EXTERNAL)
#include <sha1dc/sha1.h>
#else
#include "sha1dc/sha1.h"
#endif
#ifdef DC_SHA1_EXTERNAL
void git_SHA1DCInit(SHA1_CTX *);
#else
#define git_SHA1DCInit SHA1DCInit
#endif
void git_SHA1DCFinal(unsigned char [20], SHA1_CTX *);
void git_SHA1DCUpdate(SHA1_CTX *ctx, const void *data, unsigned long len);
#define platform_SHA_CTX SHA1_CTX
#define platform_SHA1_Init SHA1DCInit
#define platform_SHA1_Init git_SHA1DCInit
#define platform_SHA1_Update git_SHA1DCUpdate
#define platform_SHA1_Final git_SHA1DCFinal