@@ -494,6 +494,7 @@ static void fmt_merge_msg_sigs(struct strbuf *out)
enum object_type type;
unsigned long size, len;
char *buf = read_object_file(oid, &type, &size);
+ struct signature_check sigc = { 0 };
struct strbuf sig = STRBUF_INIT;
if (!buf || type != OBJ_TAG)
@@ -502,10 +503,12 @@ static void fmt_merge_msg_sigs(struct strbuf *out)
if (size == len)
; /* merely annotated */
- else if (verify_signed_buffer(buf, len, buf + len, size - len, &sig, NULL)) {
- if (!sig.len)
- strbuf_addstr(&sig, "gpg verification failed.\n");
- }
+ else if (check_signature(buf, len, buf + len, size - len, &sigc) &&
+ !sigc.gpg_output)
+ strbuf_addstr(&sig, "gpg verification failed.\n");
+ else
+ strbuf_addstr(&sig, sigc.gpg_output);
+ signature_check_clear(&sigc);
if (!tag_number++) {
fmt_tag_signature(&tagbuf, &sig, buf, len);
@@ -256,6 +256,55 @@ static void parse_gpg_output(struct signature_check *sigc)
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)
{
@@ -418,51 +467,3 @@ 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;
-}
@@ -54,15 +54,6 @@ size_t parse_signature(const char *buf, size_t size);
int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
const char *signing_key);
-/*
- * Run "gpg" to see if the payload matches the detached signature.
- * gpg_output, when set, receives the diagnostic output from GPG.
- * gpg_status, when set, receives the status output from GPG.
- */
-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);
-
int git_gpg_config(const char *, const char *, void *);
void set_signing_key(const char *);
const char *get_signing_key(void);
@@ -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 */
}
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> --- builtin/fmt-merge-msg.c | 11 +++-- gpg-interface.c | 97 +++++++++++++++++++++-------------------- gpg-interface.h | 9 ---- log-tree.c | 34 +++++++-------- 4 files changed, 73 insertions(+), 78 deletions(-)