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>
+# -DCOLLISION_CHECK if you believe that SHA1's
+# 1461501637330902918203684832716283019655932542976 hashes do not give you
+# enough guarantees about no collisions between objects ever hapenning.
CC=gcc
PROG= update-cache show-diff init-db write-tree read-tree commit-tree \
CC=gcc
PROG= update-cache show-diff init-db write-tree read-tree commit-tree \
int fd;
fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
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;
write(fd, buf, size);
close(fd);
return 0;