diff options
author | Hans Jerry Illikainen <hji@dyntopia.com> | 2019-11-27 20:48:21 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2019-12-01 00:52:35 +0300 |
commit | 72b006f4bfd30b7c5037c163efaf279ab65bea9c (patch) | |
tree | 50fdf5a566469f65c1b496efaaee77961775322e /gpg-interface.c | |
parent | 67a6ea63008bcee32a239934ad29eb5c5a554509 (diff) |
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 'gpg-interface.c')
-rw-r--r-- | gpg-interface.c | 97 |
1 files changed, 49 insertions, 48 deletions
diff --git a/gpg-interface.c b/gpg-interface.c index 131e7d529e9..5134ce27806 100644 --- a/gpg-interface.c +++ b/gpg-interface.c @@ -207,6 +207,55 @@ found_duplicate_status: FREE_AND_NULL(sigc->key); } +static int verify_signed_buffer(const char *payload, size_t payload_size, + const char *signature, size_t signature_size, + struct strbuf *gpg_output, + struct strbuf *gpg_status) +{ + struct child_process gpg = CHILD_PROCESS_INIT; + struct gpg_format *fmt; + struct tempfile *temp; + int ret; + struct strbuf buf = STRBUF_INIT; + + temp = mks_tempfile_t(".git_vtag_tmpXXXXXX"); + if (!temp) + return error_errno(_("could not create temporary file")); + if (write_in_full(temp->fd, signature, signature_size) < 0 || + close_tempfile_gently(temp) < 0) { + error_errno(_("failed writing detached signature to '%s'"), + temp->filename.buf); + delete_tempfile(&temp); + return -1; + } + + fmt = get_format_by_sig(signature); + if (!fmt) + BUG("bad signature '%s'", signature); + + argv_array_push(&gpg.args, fmt->program); + argv_array_pushv(&gpg.args, fmt->verify_args); + argv_array_pushl(&gpg.args, + "--status-fd=1", + "--verify", temp->filename.buf, "-", + NULL); + + if (!gpg_status) + gpg_status = &buf; + + sigchain_push(SIGPIPE, SIG_IGN); + ret = pipe_command(&gpg, payload, payload_size, + gpg_status, 0, gpg_output, 0); + sigchain_pop(SIGPIPE); + + delete_tempfile(&temp); + + ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG "); + strbuf_release(&buf); /* no matter it was used or not */ + + return ret; +} + int check_signature(const char *payload, size_t plen, const char *signature, size_t slen, struct signature_check *sigc) { @@ -351,51 +400,3 @@ int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *sig return 0; } - -int verify_signed_buffer(const char *payload, size_t payload_size, - const char *signature, size_t signature_size, - struct strbuf *gpg_output, struct strbuf *gpg_status) -{ - struct child_process gpg = CHILD_PROCESS_INIT; - struct gpg_format *fmt; - struct tempfile *temp; - int ret; - struct strbuf buf = STRBUF_INIT; - - temp = mks_tempfile_t(".git_vtag_tmpXXXXXX"); - if (!temp) - return error_errno(_("could not create temporary file")); - if (write_in_full(temp->fd, signature, signature_size) < 0 || - close_tempfile_gently(temp) < 0) { - error_errno(_("failed writing detached signature to '%s'"), - temp->filename.buf); - delete_tempfile(&temp); - return -1; - } - - fmt = get_format_by_sig(signature); - if (!fmt) - BUG("bad signature '%s'", signature); - - argv_array_push(&gpg.args, fmt->program); - argv_array_pushv(&gpg.args, fmt->verify_args); - argv_array_pushl(&gpg.args, - "--status-fd=1", - "--verify", temp->filename.buf, "-", - NULL); - - if (!gpg_status) - gpg_status = &buf; - - sigchain_push(SIGPIPE, SIG_IGN); - ret = pipe_command(&gpg, payload, payload_size, - gpg_status, 0, gpg_output, 0); - sigchain_pop(SIGPIPE); - - delete_tempfile(&temp); - - ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG "); - strbuf_release(&buf); /* no matter it was used or not */ - - return ret; -} |