Add "tag" objects that can be used to sign other objects.

You use "git-mktag" to create them, and fsck-cache knows how to parse them.

diff --git a/Makefile b/Makefile
index 022af9b..953e880 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,7 @@ AR=ar
 PROG=   update-cache show-diff init-db write-tree read-tree commit-tree \
        cat-file fsck-cache checkout-cache diff-tree rev-tree show-files \
        check-files ls-tree merge-base merge-cache unpack-file git-export \
-       diff-cache convert-cache http-pull rpush rpull rev-list
+       diff-cache convert-cache http-pull rpush rpull rev-list git-mktag
 
 all: $(PROG)
 

diff --git a/fsck-cache.c b/fsck-cache.c
index e3c41d4..12443b1 100644 (file)
--- a/fsck-cache.c
+++ b/fsck-cache.c
@@ -69,6 +69,42 @@ static int fsck_blob(unsigned char *sha1, void *data, unsigned long size)
        return 0;
 }
 
+static int fsck_tag(unsigned char *sha1, void *data, unsigned long size)
+{
+       int typelen, taglen;
+       unsigned char object[20];
+       const char *type_line, *tag_line, *sig_line;
+
+       if (size < 64)
+               return -1;
+       if (memcmp("object ", data, 7) || get_sha1_hex(data + 7, object))
+               return -1;
+
+       type_line = data + 48;
+       if (memcmp("\ntype ", type_line-1, 6))
+               return -1;
+
+       tag_line = strchr(type_line, '\n');
+       if (!tag_line || memcmp("tag ", ++tag_line, 4))
+               return -1;
+
+       sig_line = strchr(tag_line, '\n');
+       if (!sig_line)
+               return -1;
+       sig_line++;
+
+       typelen = tag_line - type_line - strlen("type \n");
+       if (typelen >= 20)
+               return -1;
+       taglen = sig_line - tag_line - strlen("tag \n");
+
+       printf("tagged %.*s %s (%.*s)\n",
+               typelen, type_line + 5,
+               sha1_to_hex(object),
+               taglen, tag_line + 4);
+       return 0;
+}
+
 static int fsck_entry(unsigned char *sha1, char *tag, void *data, 
                      unsigned long size)
 {
@@ -81,6 +117,9 @@ static int fsck_entry(unsigned char *sha1, char *tag, void *data,
        } else if (!strcmp(tag, "commit")) {
                if (fsck_commit(sha1, data, size) < 0)
                        return -1;
+       } else if (!strcmp(tag, "tag")) {
+               if (fsck_tag(sha1, data, size) < 0)
+                       return -1;
        } else
                return -1;
        return 0;

diff --git a/git-mktag.c b/git-mktag.c
new file mode 100644 (file)
index 0000000..5d2830d
--- /dev/null
+++ b/git-mktag.c
@@ -0,0 +1,125 @@
+#include "cache.h"
+
+/*
+ * A signature file has a very simple fixed format: three lines
+ * of "object <sha1>" + "type <typename>" + "tag <tagname>",
+ * followed by some free-form signature that git itself doesn't
+ * care about, but that can be verified with gpg or similar.
+ *
+ * The first three lines are guaranteed to be at least 63 bytes:
+ * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
+ * shortest possible type-line, and "tag .\n" at 6 bytes is the
+ * shortest single-character-tag line. 
+ *
+ * We also artificially limit the size of the full object to 8kB.
+ * Just because I'm a lazy bastard, and if you can't fit a signature
+ * in that size, you're doing something wrong.
+ */
+
+// Some random size
+#define MAXSIZE (8192)
+
+/*
+ * We refuse to tag something we can't verify. Just because.
+ */
+static int verify_object(unsigned char *sha1, const char *expected_type)
+{
+       int ret = -1;
+       unsigned long mapsize;
+       void *map = map_sha1_file(sha1, &mapsize);
+
+       if (map) {
+               char type[100];
+               unsigned long size;
+               void *buffer = unpack_sha1_file(map, mapsize, type, &size);
+
+               if (buffer) {
+                       if (!strcmp(type, expected_type))
+                               ret = check_sha1_signature(sha1, buffer, size, type);
+                       free(buffer);
+               }
+               munmap(map, mapsize);
+       }
+       return ret;
+}
+
+static int verify_tag(char *buffer, unsigned long size)
+{
+       int typelen;
+       char type[20];
+       unsigned char sha1[20];
+       const char *object, *type_line, *tag_line;
+
+       if (size < 64 || size > MAXSIZE-1)
+               return -1;
+       buffer[size] = 0;
+
+       /* Verify object line */
+       object = buffer;
+       if (memcmp(object, "object ", 7))
+               return -1;
+       if (get_sha1_hex(object + 7, sha1))
+               return -1;
+
+       /* Verify type line */
+       type_line = object + 48;
+       if (memcmp(type_line - 1, "\ntype ", 6))
+               return -1;
+
+       /* Verify tag-line */
+       tag_line = strchr(type_line, '\n');
+       if (!tag_line)
+               return -1;
+       tag_line++;
+       if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
+               return -1;
+
+       /* Get the actual type */
+       typelen = tag_line - type_line - strlen("type \n");
+       if (typelen >= sizeof(type))
+               return -1;
+       memcpy(type, type_line+5, typelen);
+       type[typelen] = 0;
+
+       /* Verify that the object matches */
+       if (get_sha1_hex(object + 7, sha1))
+               return -1;
+       if (verify_object(sha1, type))
+               return -1;
+
+       /* Verify the tag-name: we don't allow control characters or spaces in it */
+       tag_line += 4;
+       for (;;) {
+               unsigned char c = *tag_line++;
+               if (c == '\n')
+                       break;
+               if (c > ' ')
+                       continue;
+               return -1;
+       }
+
+       /* The actual stuff afterwards we don't care about.. */
+       return 0;
+}
+
+int main(int argc, char **argv)
+{
+       unsigned long size;
+       char buffer[MAXSIZE];
+       unsigned char result_sha1[20];
+
+       if (argc != 1)
+               usage("cat <signaturefile> | git-mktag");
+
+       // Read the signature
+       size = read(0, buffer, MAXSIZE);
+
+       // Verify it for some basic sanity: it needs to start with "object <sha1>\ntag "
+       if (verify_tag(buffer, size) < 0)
+               die("invalid tag signature file");
+
+       if (write_sha1_file(buffer, size, "tag", result_sha1) < 0)
+               die("unable to write tag file");
+       printf("%s\n", sha1_to_hex(result_sha1));
+       return 0;
+}