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author | Hans Jerry Illikainen <hji@dyntopia.com> | 2020-03-04 11:48:04 +0000 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2020-03-15 09:46:28 -0700 |
commit | 67948981983b336eab2fa7e6a0e125d529391dfc (patch) | |
tree | 6365d127be157a4ae8061186e0a156cce7497014 /log-tree.c | |
parent | f1e3df316992d32b17ee27385e4c644ef7b66cc1 (diff) | |
download | git-67948981983b336eab2fa7e6a0e125d529391dfc.tar.gz |
gpg-interface: prefer check_signature() for GPG verification
This commit refactors the use of verify_signed_buffer() outside of
gpg-interface.c to use check_signature() instead. It also turns
verify_signed_buffer() into a file-local function since it's now only
invoked internally by check_signature().
There were previously two globally scoped functions used in different
parts of Git to perform GPG signature verification:
verify_signed_buffer() and check_signature(). Now only
check_signature() is used.
The verify_signed_buffer() function doesn't guard against duplicate
signatures as described by Michał Górny [1]. Instead it only ensures a
non-erroneous exit code from GPG and the presence of at least one
GOODSIG status field. This stands in contrast with check_signature()
that returns an error if more than one signature is encountered.
The lower degree of verification makes the use of verify_signed_buffer()
problematic if callers don't parse and validate the various parts of the
GPG status message themselves. And processing these messages seems like
a task that should be reserved to gpg-interface.c with the function
check_signature().
Furthermore, the use of verify_signed_buffer() makes it difficult to
introduce new functionality that relies on the content of the GPG status
lines.
Now all operations that does signature verification share a single entry
point to gpg-interface.c. This makes it easier to propagate changed or
additional functionality in GPG signature verification to all parts of
Git, without having odd edge-cases that don't perform the same degree of
verification.
[1] https://dev.gentoo.org/~mgorny/articles/attack-on-git-signature-verification.html
Signed-off-by: Hans Jerry Illikainen <hji@dyntopia.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'log-tree.c')
-rw-r--r-- | log-tree.c | 34 |
1 files changed, 17 insertions, 17 deletions
diff --git a/log-tree.c b/log-tree.c index 5425ae931f..f1ac5a68d9 100644 --- a/log-tree.c +++ b/log-tree.c @@ -449,22 +449,21 @@ static void show_signature(struct rev_info *opt, struct commit *commit) { struct strbuf payload = STRBUF_INIT; struct strbuf signature = STRBUF_INIT; - struct strbuf gpg_output = STRBUF_INIT; + struct signature_check sigc = { 0 }; int status; if (parse_signed_commit(commit, &payload, &signature) <= 0) goto out; - status = verify_signed_buffer(payload.buf, payload.len, - signature.buf, signature.len, - &gpg_output, NULL); - if (status && !gpg_output.len) - strbuf_addstr(&gpg_output, "No signature\n"); - - show_sig_lines(opt, status, gpg_output.buf); + status = check_signature(payload.buf, payload.len, signature.buf, + signature.len, &sigc); + if (status && !sigc.gpg_output) + show_sig_lines(opt, status, "No signature\n"); + else + show_sig_lines(opt, status, sigc.gpg_output); + signature_check_clear(&sigc); out: - strbuf_release(&gpg_output); strbuf_release(&payload); strbuf_release(&signature); } @@ -497,8 +496,9 @@ static int show_one_mergetag(struct commit *commit, struct object_id oid; struct tag *tag; struct strbuf verify_message; + struct signature_check sigc = { 0 }; int status, nth; - size_t payload_size, gpg_message_offset; + size_t payload_size; hash_object_file(the_hash_algo, extra->value, extra->len, type_name(OBJ_TAG), &oid); @@ -520,19 +520,19 @@ static int show_one_mergetag(struct commit *commit, else strbuf_addf(&verify_message, "parent #%d, tagged '%s'\n", nth + 1, tag->tag); - gpg_message_offset = verify_message.len; payload_size = parse_signature(extra->value, extra->len); status = -1; if (extra->len > payload_size) { /* could have a good signature */ - if (!verify_signed_buffer(extra->value, payload_size, - extra->value + payload_size, - extra->len - payload_size, - &verify_message, NULL)) - status = 0; /* good */ - else if (verify_message.len <= gpg_message_offset) + status = check_signature(extra->value, payload_size, + extra->value + payload_size, + extra->len - payload_size, &sigc); + if (sigc.gpg_output) + strbuf_addstr(&verify_message, sigc.gpg_output); + else strbuf_addstr(&verify_message, "No signature\n"); + signature_check_clear(&sigc); /* otherwise we couldn't verify, which is shown as bad */ } |