git/object-file-convert.c
Eric W. Biederman 08a45903cb object-file-convert: convert commits that embed signed tags
As mentioned in the hash function transition plan commit mergetag
lines need to be handled.  The commit mergetag lines embed an entire
tag object in a commit object.

Keep the implementation sane if not fast by unembedding the tag
object, converting the tag object, and embedding the new tag object,
in the new commit object.

In the long run I don't expect any other approach is maintainable, as
tag objects may be extended in ways that require additional
translation.

To keep the implementation of convert_commit_object maintainable I
have modified convert_commit_object to process the lines in any order,
and to fail on unknown lines.  We can't know ahead of time if a new
line might embed something that needs translation or not so it is
better to fail and require the code to be updated instead of silently
mistranslating objects.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-10-02 14:57:39 -07:00

278 lines
8.1 KiB
C

#include "git-compat-util.h"
#include "gettext.h"
#include "strbuf.h"
#include "hex.h"
#include "repository.h"
#include "hash-ll.h"
#include "hash.h"
#include "object.h"
#include "loose.h"
#include "commit.h"
#include "gpg-interface.h"
#include "object-file-convert.h"
int repo_oid_to_algop(struct repository *repo, const struct object_id *src,
const struct git_hash_algo *to, struct object_id *dest)
{
/*
* If the source algorithm is not set, then we're using the
* default hash algorithm for that object.
*/
const struct git_hash_algo *from =
src->algo ? &hash_algos[src->algo] : repo->hash_algo;
if (from == to) {
if (src != dest)
oidcpy(dest, src);
return 0;
}
if (repo_loose_object_map_oid(repo, src, to, dest)) {
/*
* We may have loaded the object map at repo initialization but
* another process (perhaps upstream of a pipe from us) may have
* written a new object into the map. If the object is missing,
* let's reload the map to see if the object has appeared.
*/
repo_read_loose_object_map(repo);
if (repo_loose_object_map_oid(repo, src, to, dest))
return -1;
}
return 0;
}
static int decode_tree_entry_raw(struct object_id *oid, const char **path,
size_t *len, const struct git_hash_algo *algo,
const char *buf, unsigned long size)
{
uint16_t mode;
const unsigned hashsz = algo->rawsz;
if (size < hashsz + 3 || buf[size - (hashsz + 1)]) {
return -1;
}
*path = parse_mode(buf, &mode);
if (!*path || !**path)
return -1;
*len = strlen(*path) + 1;
oidread_algop(oid, (const unsigned char *)*path + *len, algo);
return 0;
}
static int convert_tree_object(struct strbuf *out,
const struct git_hash_algo *from,
const struct git_hash_algo *to,
const char *buffer, size_t size)
{
const char *p = buffer, *end = buffer + size;
while (p < end) {
struct object_id entry_oid, mapped_oid;
const char *path = NULL;
size_t pathlen;
if (decode_tree_entry_raw(&entry_oid, &path, &pathlen, from, p,
end - p))
return error(_("failed to decode tree entry"));
if (repo_oid_to_algop(the_repository, &entry_oid, to, &mapped_oid))
return error(_("failed to map tree entry for %s"), oid_to_hex(&entry_oid));
strbuf_add(out, p, path - p);
strbuf_add(out, path, pathlen);
strbuf_add(out, mapped_oid.hash, to->rawsz);
p = path + pathlen + from->rawsz;
}
return 0;
}
static int convert_tag_object(struct strbuf *out,
const struct git_hash_algo *from,
const struct git_hash_algo *to,
const char *buffer, size_t size)
{
struct strbuf payload = STRBUF_INIT, oursig = STRBUF_INIT, othersig = STRBUF_INIT;
const int entry_len = from->hexsz + 7;
size_t payload_size;
struct object_id oid, mapped_oid;
const char *p;
/* Consume the object line */
if ((entry_len >= size) ||
memcmp(buffer, "object ", 7) || buffer[entry_len] != '\n')
return error("bogus tag object");
if (parse_oid_hex_algop(buffer + 7, &oid, &p, from) < 0)
return error("bad tag object ID");
if (repo_oid_to_algop(the_repository, &oid, to, &mapped_oid))
return error("unable to map tree %s in tag object",
oid_to_hex(&oid));
size -= ((p + 1) - buffer);
buffer = p + 1;
/* Is there a signature for our algorithm? */
payload_size = parse_signed_buffer(buffer, size);
if (payload_size != size) {
/* Yes, there is. */
strbuf_add(&oursig, buffer + payload_size, size - payload_size);
}
/* Now, is there a signature for the other algorithm? */
parse_buffer_signed_by_header(buffer, payload_size, &payload, &othersig, to);
/*
* Our payload is now in payload and we may have up to two signatrures
* in oursig and othersig.
*/
/* Add some slop for longer signature header in the new algorithm. */
strbuf_grow(out, (7 + to->hexsz + 1) + size + 7);
strbuf_addf(out, "object %s\n", oid_to_hex(&mapped_oid));
strbuf_addbuf(out, &payload);
if (oursig.len)
add_header_signature(out, &oursig, from);
strbuf_addbuf(out, &othersig);
strbuf_release(&payload);
strbuf_release(&othersig);
strbuf_release(&oursig);
return 0;
}
static int convert_commit_object(struct strbuf *out,
const struct git_hash_algo *from,
const struct git_hash_algo *to,
const char *buffer, size_t size)
{
const char *tail = buffer;
const char *bufptr = buffer;
const int tree_entry_len = from->hexsz + 5;
const int parent_entry_len = from->hexsz + 7;
struct object_id oid, mapped_oid;
const char *p, *eol;
tail += size;
while ((bufptr < tail) && (*bufptr != '\n')) {
eol = memchr(bufptr, '\n', tail - bufptr);
if (!eol)
return error(_("bad %s in commit"), "line");
if (((bufptr + 5) < eol) && !memcmp(bufptr, "tree ", 5))
{
if (((bufptr + tree_entry_len) != eol) ||
parse_oid_hex_algop(bufptr + 5, &oid, &p, from) ||
(p != eol))
return error(_("bad %s in commit"), "tree");
if (repo_oid_to_algop(the_repository, &oid, to, &mapped_oid))
return error(_("unable to map %s %s in commit object"),
"tree", oid_to_hex(&oid));
strbuf_addf(out, "tree %s\n", oid_to_hex(&mapped_oid));
}
else if (((bufptr + 7) < eol) && !memcmp(bufptr, "parent ", 7))
{
if (((bufptr + parent_entry_len) != eol) ||
parse_oid_hex_algop(bufptr + 7, &oid, &p, from) ||
(p != eol))
return error(_("bad %s in commit"), "parent");
if (repo_oid_to_algop(the_repository, &oid, to, &mapped_oid))
return error(_("unable to map %s %s in commit object"),
"parent", oid_to_hex(&oid));
strbuf_addf(out, "parent %s\n", oid_to_hex(&mapped_oid));
}
else if (((bufptr + 9) < eol) && !memcmp(bufptr, "mergetag ", 9))
{
struct strbuf tag = STRBUF_INIT, new_tag = STRBUF_INIT;
/* Recover the tag object from the mergetag */
strbuf_add(&tag, bufptr + 9, (eol - (bufptr + 9)) + 1);
bufptr = eol + 1;
while ((bufptr < tail) && (*bufptr == ' ')) {
eol = memchr(bufptr, '\n', tail - bufptr);
if (!eol) {
strbuf_release(&tag);
return error(_("bad %s in commit"), "mergetag continuation");
}
strbuf_add(&tag, bufptr + 1, (eol - (bufptr + 1)) + 1);
bufptr = eol + 1;
}
/* Compute the new tag object */
if (convert_tag_object(&new_tag, from, to, tag.buf, tag.len)) {
strbuf_release(&tag);
strbuf_release(&new_tag);
return -1;
}
/* Write the new mergetag */
strbuf_addstr(out, "mergetag");
strbuf_add_lines(out, " ", new_tag.buf, new_tag.len);
strbuf_release(&tag);
strbuf_release(&new_tag);
}
else if (((bufptr + 7) < tail) && !memcmp(bufptr, "author ", 7))
strbuf_add(out, bufptr, (eol - bufptr) + 1);
else if (((bufptr + 10) < tail) && !memcmp(bufptr, "committer ", 10))
strbuf_add(out, bufptr, (eol - bufptr) + 1);
else if (((bufptr + 9) < tail) && !memcmp(bufptr, "encoding ", 9))
strbuf_add(out, bufptr, (eol - bufptr) + 1);
else if (((bufptr + 6) < tail) && !memcmp(bufptr, "gpgsig", 6))
strbuf_add(out, bufptr, (eol - bufptr) + 1);
else {
/* Unknown line fail it might embed an oid */
return -1;
}
/* Consume any trailing continuation lines */
bufptr = eol + 1;
while ((bufptr < tail) && (*bufptr == ' ')) {
eol = memchr(bufptr, '\n', tail - bufptr);
if (!eol)
return error(_("bad %s in commit"), "continuation");
strbuf_add(out, bufptr, (eol - bufptr) + 1);
bufptr = eol + 1;
}
}
if (bufptr < tail)
strbuf_add(out, bufptr, tail - bufptr);
return 0;
}
int convert_object_file(struct strbuf *outbuf,
const struct git_hash_algo *from,
const struct git_hash_algo *to,
const void *buf, size_t len,
enum object_type type,
int gentle)
{
int ret;
/* Don't call this function when no conversion is necessary */
if ((from == to) || (type == OBJ_BLOB))
BUG("Refusing noop object file conversion");
switch (type) {
case OBJ_COMMIT:
ret = convert_commit_object(outbuf, from, to, buf, len);
break;
case OBJ_TREE:
ret = convert_tree_object(outbuf, from, to, buf, len);
break;
case OBJ_TAG:
ret = convert_tag_object(outbuf, from, to, buf, len);
break;
default:
/* Not implemented yet, so fail. */
ret = -1;
break;
}
if (!ret)
return 0;
if (gentle) {
strbuf_release(outbuf);
return ret;
}
die(_("Failed to convert object from %s to %s"),
from->name, to->name);
}