sha1dc: allow building with the external sha1dc library
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>
Takashi Iwai committed
Aug 15, 2017 at 14:04 UTC
3964cbbb5c30609ebd795a979074251cf59436c3
3 files changed
+33
-1
Makefile
+13
@@ -162,6 +162,11 @@ all::
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# algorithm. This is slower, but may detect attempted collision attacks.
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# Takes priority over other *_SHA1 knobs.
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#
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+# Define DC_SHA1_EXTERNAL in addition to DC_SHA1 if you want to build / link
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+# git with the external SHA1 collision-detect library.
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+# Without this option, i.e. the default behavior is to build git with its
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+# own built-in code (or submodule).
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+#
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# Define DC_SHA1_SUBMODULE in addition to DC_SHA1 to use the
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# sha1collisiondetection shipped as a submodule instead of the
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# non-submodule copy in sha1dc/. This is an experimental option used
@@ -1474,6 +1479,13 @@ else
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DC_SHA1 := YesPlease
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BASIC_CFLAGS += -DSHA1_DC
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LIB_OBJS += sha1dc_git.o
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+ifdef DC_SHA1_EXTERNAL
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+ ifdef DC_SHA1_SUBMODULE
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+$(error Only set DC_SHA1_EXTERNAL or DC_SHA1_SUBMODULE, not both)
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+ endif
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+ BASIC_CFLAGS += -DDC_SHA1_EXTERNAL
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+ EXTLIBS += -lsha1detectcoll
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+else
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ifdef DC_SHA1_SUBMODULE
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LIB_OBJS += sha1collisiondetection/lib/sha1.o
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LIB_OBJS += sha1collisiondetection/lib/ubc_check.o
@@ -1491,6 +1503,7 @@ endif
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endif
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endif
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endif
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+endif
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ifdef SHA1_MAX_BLOCK_SIZE
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LIB_OBJS += compat/sha1-chunked.o
sha1dc_git.c
+11
@@ -1,5 +1,16 @@
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#include "cache.h"
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+#ifdef DC_SHA1_EXTERNAL
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+/*
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+ * Same as SHA1DCInit, but with default save_hash=0
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+ */
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+void git_SHA1DCInit(SHA1_CTX *ctx)
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+{
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+ SHA1DCInit(ctx);
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+ SHA1DCSetSafeHash(ctx, 0);
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+}
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+#endif
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+
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/*
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* Same as SHA1DCFinal, but convert collision attack case into a verbose die().
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*/
sha1dc_git.h
+9
-1
@@ -2,14 +2,22 @@
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#ifdef DC_SHA1_SUBMODULE
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#include "sha1collisiondetection/lib/sha1.h"
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+#elif defined(DC_SHA1_EXTERNAL)
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+#include <sha1dc/sha1.h>
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#else
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#include "sha1dc/sha1.h"
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#endif
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+#ifdef DC_SHA1_EXTERNAL
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+void git_SHA1DCInit(SHA1_CTX *);
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+#else
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+#define git_SHA1DCInit SHA1DCInit
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+#endif
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+
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void git_SHA1DCFinal(unsigned char [20], SHA1_CTX *);
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void git_SHA1DCUpdate(SHA1_CTX *ctx, const void *data, unsigned long len);
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#define platform_SHA_CTX SHA1_CTX
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-#define platform_SHA1_Init SHA1DCInit
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+#define platform_SHA1_Init git_SHA1DCInit
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#define platform_SHA1_Update git_SHA1DCUpdate
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#define platform_SHA1_Final git_SHA1DCFinal