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[PATCH] SHA1 naive collision checking 

When compiled with -DCOLLISION_CHECK, we will check against SHA1
collisions when writing to the object database.

From: Christopher Li <chrislgit@chrisli.org>
Signed-off-by: Petr Baudis <pasky@ucw.cz>
This commit is contained in:
Petr Baudis 2005-04-13 02:14:06 -07:00 committed by Petr Baudis
parent 7912c07037
commit 5c2a7fbc36
2 changed files with 23 additions and 2 deletions
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4
Makefile
View File

@ -1,4 +1,8 @@
# -DCOLLISION_CHECK if you believe that SHA1's
# 1461501637330902918203684832716283019655932542976 hashes do not give you
# enough guarantees about no collisions between objects ever hapenning.
CFLAGS=-g -O3 -Wall
CC=gcc
PROG= update-cache show-diff init-db write-tree read-tree commit-tree \

21
read-cache.c
View File

@ -216,8 +216,25 @@ int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
int fd;
fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
if (fd < 0)
return (errno == EEXIST) ? 0 : -1;
if (fd < 0) {
void *map;
static int error(const char * string);
if (errno != EEXIST)
return -1;
#ifndef COLLISION_CHECK
fd = open(filename, O_RDONLY);
if (fd < 0)
return -1;
map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
if (map == MAP_FAILED)
return -1;
if (memcmp(buf, map, size))
return error("SHA1 collision detected!"
" This is bad, bad, BAD!\a\n");
#endif
return 0;
}
write(fd, buf, size);
close(fd);
return 0;