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b97e3dfa76
Instead of always assuming it can be read with a single read() system call, loop around properly. Pointed out by Pasky, but I ended up implementing it differently from his suggested patch.
131 lines
3.0 KiB
C
131 lines
3.0 KiB
C
#include "cache.h"
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/*
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* A signature file has a very simple fixed format: three lines
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* of "object <sha1>" + "type <typename>" + "tag <tagname>",
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* followed by some free-form signature that git itself doesn't
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* care about, but that can be verified with gpg or similar.
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*
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* The first three lines are guaranteed to be at least 63 bytes:
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* "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
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* shortest possible type-line, and "tag .\n" at 6 bytes is the
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* shortest single-character-tag line.
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*
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* We also artificially limit the size of the full object to 8kB.
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* Just because I'm a lazy bastard, and if you can't fit a signature
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* in that size, you're doing something wrong.
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*/
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// Some random size
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#define MAXSIZE (8192)
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/*
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* We refuse to tag something we can't verify. Just because.
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*/
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static int verify_object(unsigned char *sha1, const char *expected_type)
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{
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int ret = -1;
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char type[100];
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unsigned long size;
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void *buffer = read_sha1_file(sha1, type, &size);
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if (buffer) {
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if (!strcmp(type, expected_type))
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ret = check_sha1_signature(sha1, buffer, size, type);
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free(buffer);
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}
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return ret;
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}
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static int verify_tag(char *buffer, unsigned long size)
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{
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int typelen;
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char type[20];
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unsigned char sha1[20];
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const char *object, *type_line, *tag_line;
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if (size < 64 || size > MAXSIZE-1)
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return -1;
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buffer[size] = 0;
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/* Verify object line */
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object = buffer;
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if (memcmp(object, "object ", 7))
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return -1;
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if (get_sha1_hex(object + 7, sha1))
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return -1;
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/* Verify type line */
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type_line = object + 48;
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if (memcmp(type_line - 1, "\ntype ", 6))
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return -1;
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/* Verify tag-line */
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tag_line = strchr(type_line, '\n');
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if (!tag_line)
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return -1;
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tag_line++;
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if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
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return -1;
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/* Get the actual type */
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typelen = tag_line - type_line - strlen("type \n");
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if (typelen >= sizeof(type))
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return -1;
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memcpy(type, type_line+5, typelen);
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type[typelen] = 0;
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/* Verify that the object matches */
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if (get_sha1_hex(object + 7, sha1))
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return -1;
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if (verify_object(sha1, type))
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return -1;
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/* Verify the tag-name: we don't allow control characters or spaces in it */
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tag_line += 4;
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for (;;) {
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unsigned char c = *tag_line++;
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if (c == '\n')
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break;
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if (c > ' ')
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continue;
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return -1;
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}
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/* The actual stuff afterwards we don't care about.. */
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return 0;
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}
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int main(int argc, char **argv)
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{
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unsigned long size;
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char buffer[MAXSIZE];
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unsigned char result_sha1[20];
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if (argc != 1)
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usage("cat <signaturefile> | git-mktag");
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// Read the signature
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size = 0;
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for (;;) {
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int ret = read(0, buffer + size, MAXSIZE - size);
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if (!ret)
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break;
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if (ret < 0) {
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if (errno == EAGAIN)
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continue;
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break;
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}
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size += ret;
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}
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// Verify it for some basic sanity: it needs to start with "object <sha1>\ntype "
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if (verify_tag(buffer, size) < 0)
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die("invalid tag signature file");
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if (write_sha1_file(buffer, size, "tag", result_sha1) < 0)
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die("unable to write tag file");
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printf("%s\n", sha1_to_hex(result_sha1));
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return 0;
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}
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