Jon SeymourFor the purposes of merging the contents of remote git object repositories at the filesystem level, it would be helpful to be able to verify the integrity of a remote git object file before it is actually copied into the local repository.
To enable this, the option syntax for the usage of the cat-file tool is extended with a -i option, per the modified usage string quoted below:
usage: cat-file [-t | tagname] <sha1> [ -i displaced-git-object-file ]
If the -i option is specified, cat-file uses the filename specified on the command line rather than the derived filename to locate and process the git object file implied by the sha1 argument.
In addition, the -i option forces cat-file to check the SHA1 signature of the specified input file against the SHA1 signature specified on the command line and report an error if there is a mismatch.
Signed-off-by: Jon Seymour <jon.seymour@gmail.com> --
Show changes to diff +45 −9
Index: cache.h =================================================================== --- e6d3a81c30ad237102e2ca82f3dfc57d0b9f0ddf/cache.h (mode:100644 sha1:bf30ac4741d2eeeb483079f566182505898082f3) +++ 1b503f0571727a865b413e28641d2be09c8c3304/cache.h (mode:100644 sha1:56eacfa0ab43c93a838efedca429e865c95f16bc) @@ -121,8 +121,9 @@ extern void * map_sha1_file(const unsigned char *sha1, unsigned long *size); extern void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size); extern void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size); +extern void * read_displaced_sha1_file(char *type, unsigned long *size, const char *filename); extern int write_sha1_file(char *buf, unsigned len, unsigned char *return_sha1); -extern int check_sha1_signature(unsigned char *sha1, void *buf, unsigned long size, const char *type); +extern int check_sha1_signature(const unsigned char *sha1, void *buf, unsigned long size, const char *type); /* Read a tree into the cache */ extern int read_tree(void *buffer, unsigned long size, int stage); Index: cat-file.c =================================================================== --- e6d3a81c30ad237102e2ca82f3dfc57d0b9f0ddf/cat-file.c (mode:100644 sha1:3c47d79a16305d326a65768fe9f37ee25928510b) +++ 1b503f0571727a865b413e28641d2be09c8c3304/cat-file.c (mode:100644 sha1:c88df7287b6ce7d6d33d016ffb524cc5a793cad2) @@ -5,16 +5,32 @@ */ #include "cache.h" +static char _usage[]="cat-file [-t | tagname] <sha1> [ -i displaced-git-object-file ]"; + int main(int argc, char **argv) { unsigned char sha1[20]; char type[20]; - void *buf; + void *buf = NULL; unsigned long size; - if (argc != 3 || get_sha1_hex(argv[2], sha1)) - usage("cat-file [-t | tagname] <sha1>"); - buf = read_sha1_file(sha1, type, &size); + if (argc < 3 || get_sha1_hex(argv[2], sha1)) + usage(_usage); + + if (argc == 3) { + buf = read_sha1_file(sha1, type, &size); + } else if (argc == 5 && !strcmp(argv[3], "-i")) { + buf = read_displaced_sha1_file(type, &size, argv[4]); + if (!buf) + die("bad file: %s", argv[4]); + + if (check_sha1_signature(sha1, buf, size, type) < 0) + die("signature mismatch for %s", argv[4]); + + } else { + usage(_usage); + } + if (!buf) die("cat-file %s: bad file", argv[2]); if (!strcmp("-t", argv[1])) { Index: sha1_file.c =================================================================== --- e6d3a81c30ad237102e2ca82f3dfc57d0b9f0ddf/sha1_file.c (mode:100644 sha1:6f7228e106d4e24b18f8416cc6adc2a6fd303eb7) +++ 1b503f0571727a865b413e28641d2be09c8c3304/sha1_file.c (mode:100644 sha1:25e2e8b22cf9590a6df05f234ce88db8c2cd1030) @@ -80,7 +80,7 @@ return base; } -int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type) +int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type) { char header[100]; unsigned char real_sha1[20]; @@ -93,13 +93,12 @@ return memcmp(sha1, real_sha1, 20) ? -1 : 0; } -void *map_sha1_file(const unsigned char *sha1, unsigned long *size) +static void *map_file(const char *filename, unsigned long *size) { - char *filename = sha1_file_name(sha1); - int fd = open(filename, O_RDONLY); struct stat st; void *map; + int fd = open(filename, O_RDONLY); if (fd < 0) { perror(filename); return NULL; @@ -116,6 +115,12 @@ return map; } +void *map_sha1_file(const unsigned char *sha1, unsigned long *size) +{ + char *filename = sha1_file_name(sha1); + return map_file(filename, size); +} + void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size) { int ret, bytes; @@ -166,6 +171,20 @@ return NULL; } +void * read_displaced_sha1_file(char *type, unsigned long *size, const char *filename) +{ + unsigned long mapsize; + void *map, *buf; + + map = map_file(filename, &mapsize); + if (map) { + buf = unpack_sha1_file(map, mapsize, type, size); + munmap(map, mapsize); + return buf; + } + return NULL; +} + void *read_tree_with_tree_or_commit_sha1(const unsigned char *sha1, unsigned long *size, unsigned char *tree_sha1_return)