[BUG] Veryfing signatures in git log fails when language is not english

9 messages, 2 authors, 2016-06-15 · open the first message on its own page

[BUG] Veryfing signatures in git log fails when language is not english

From: XANi <hidden>
Date: 2016-06-15 22:56:09

Hi,

any functionality that depends on exact exit msg of program
 can potentially fail because of that
ᛯ export |grep LANG
declare -x LANG="pl_PL.UTF-8"

ᛯ ~/src/os/git/git log --format="%G? %h" |head -2 
 0d19377
 5b9d7f8

ᛯ unset LANG
ᛯ ~/src/os/git/git log --format="%G? %h" |head -2
G 0d19377
G 5b9d7f8

tested against maint (d32805d) and master (5bf72ed)

maybe git should set up some output-changing variables before calling
external programs? I think setting LC_ALL=C should be enougth.

-- 
Mariusz Gronczewski (XANi) [off-list ref]
GnuPG: 0xEA8ACE64

Re: [BUG] Veryfing signatures in git log fails when language is not english

From: Michael J Gruber <hidden>
Date: 2016-06-15 22:56:09

XANi venit, vidit, dixit 14.02.2013 01:18:
Hi,

any functionality that depends on exact exit msg of program
 can potentially fail because of that
ᛯ export |grep LANG
declare -x LANG="pl_PL.UTF-8"

ᛯ ~/src/os/git/git log --format="%G? %h" |head -2 
 0d19377
 5b9d7f8

ᛯ unset LANG
ᛯ ~/src/os/git/git log --format="%G? %h" |head -2
G 0d19377
G 5b9d7f8

tested against maint (d32805d) and master (5bf72ed)

maybe git should set up some output-changing variables before calling
external programs? I think setting LC_ALL=C should be enougth.
There are really multiple problems here:

1. git calls gpg without setting LANG but expects output in LANG=C

2. git looks at the textual output from gpg to check the validity.

3. In fact, it does so only for %G and the display of signed merge
commits, in all other cases it checks the return code only.

gpg is not supposed to be used like that.

Since the callers of verify_signed_buffer do that craziness there is
some refactoring to be done.

A false hotfix would be to set LANG=C when calling gpg from git, but
that wouldn't solve the real problem. Besides, we do want LANG dependent
output for the user.

I'll have a closer look.

BTW: Thanks for the clear report :)

Michael

Re: [BUG] Veryfing signatures in git log fails when language is not english

From: Mariusz Gronczewski <hidden>
Date: 2016-06-15 22:56:09

2013/2/14 Michael J Gruber [off-list ref]:
XANi venit, vidit, dixit 14.02.2013 01:18:
quoted
Hi,

any functionality that depends on exact exit msg of program
 can potentially fail because of that
ᛯ export |grep LANG
declare -x LANG="pl_PL.UTF-8"

ᛯ ~/src/os/git/git log --format="%G? %h" |head -2
 0d19377
 5b9d7f8

ᛯ unset LANG
ᛯ ~/src/os/git/git log --format="%G? %h" |head -2
G 0d19377
G 5b9d7f8

tested against maint (d32805d) and master (5bf72ed)

maybe git should set up some output-changing variables before calling
external programs? I think setting LC_ALL=C should be enougth.
There are really multiple problems here:

1. git calls gpg without setting LANG but expects output in LANG=C

2. git looks at the textual output from gpg to check the validity.

3. In fact, it does so only for %G and the display of signed merge
commits, in all other cases it checks the return code only.

gpg is not supposed to be used like that.

Since the callers of verify_signed_buffer do that craziness there is
some refactoring to be done.

A false hotfix would be to set LANG=C when calling gpg from git, but
that wouldn't solve the real problem. Besides, we do want LANG dependent
output for the user.

I'll have a closer look.

BTW: Thanks for the clear report :)

Michael
What is really missing is an ability to display used key ID without
hammering git log output with regexps, it would be much easier to
validate incoming commits if there was format option to just display
key ID instead of signer name. %GS isn't really good solution for that
because it will show only one of email addresses used in the key and
script checking signatures would have to always pick "right" one.

-- 
Mariusz Gronczewski (XANi) [off-list ref]
GnuPG: 0xEA8ACE64

[PATCH 0/5] gpg_interface: use the status

From: Michael J Gruber <hidden>
Date: 2016-06-15 22:56:09

Currently, we look at the user facing output of gpg, which is LANG dependent as
well as insecure.

After this series, we look at the status output (--status-fd) which is designed
for that purpose. As an additional benefit, we can read off the key which was used
for the signature, which is important for assigning trust.

All existing tests pass with this.

BTW: git branch --set-upstream-to= coredumps when on a detached head.

Michael J Gruber (5):
  gpg-interface: check good signature in a reliable way
  log-tree: rely upon the check in the gpg_interface
  gpg_interface: allow to request status return
  pretty: parse the gpg status lines rather than the output
  pretty: make %GK output the signing key for signed commits

 Documentation/pretty-formats.txt |  1 +
 builtin/fmt-merge-msg.c          |  2 +-
 builtin/verify-tag.c             |  2 +-
 gpg-interface.c                  | 18 +++++++++++++++---
 gpg-interface.h                  |  2 +-
 log-tree.c                       | 27 ++++++++++++---------------
 pretty.c                         | 19 +++++++++++++++----
 7 files changed, 46 insertions(+), 25 deletions(-)

-- 
1.8.1.3.797.ge0260c7

[PATCH 4/5] pretty: parse the gpg status lines rather than the output

From: Michael J Gruber <hidden>
Date: 2016-06-15 22:56:09

Currently, parse_signature_lines() parses the gpg output for strings
which depend on LANG so it fails to recognize good commit signatures
(and thus does not fill in %G? and the like) in most locales.

Make it parse the status lines from gpg instead, which are the proper
machine interface. This fixes the problem described above.

There is a change in behavior for "%GS" which we intentionally do not
work around: "%GS" used to put quotes around the signer's uid (or
rather: it inherited from the gpg user output). We output the uid
without quotes now, just like author and committer names.

Signed-off-by: Michael J Gruber <redacted>
---
 pretty.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/pretty.c b/pretty.c
index 2a1e174..973b912 100644
--- a/pretty.c
+++ b/pretty.c
@@ -759,6 +759,7 @@ struct format_commit_context {
 	unsigned commit_signature_parsed:1;
 	struct {
 		char *gpg_output;
+		char *gpg_status;
 		char good_bad;
 		char *signer;
 	} signature;
@@ -948,13 +949,13 @@ static struct {
 	char result;
 	const char *check;
 } signature_check[] = {
-	{ 'G', ": Good signature from " },
-	{ 'B', ": BAD signature from " },
+	{ 'G', "\n[GNUPG:] GOODSIG " },
+	{ 'B', "\n[GNUPG:] BADSIG " },
 };
 
 static void parse_signature_lines(struct format_commit_context *ctx)
 {
-	const char *buf = ctx->signature.gpg_output;
+	const char *buf = ctx->signature.gpg_status;
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(signature_check); i++) {
@@ -963,7 +964,7 @@ static void parse_signature_lines(struct format_commit_context *ctx)
 		if (!found)
 			continue;
 		ctx->signature.good_bad = signature_check[i].result;
-		found += strlen(signature_check[i].check);
+		found += strlen(signature_check[i].check)+17;
 		next = strchrnul(found, '\n');
 		ctx->signature.signer = xmemdupz(found, next - found);
 		break;
@@ -975,6 +976,7 @@ static void parse_commit_signature(struct format_commit_context *ctx)
 	struct strbuf payload = STRBUF_INIT;
 	struct strbuf signature = STRBUF_INIT;
 	struct strbuf gpg_output = STRBUF_INIT;
+	struct strbuf gpg_status = STRBUF_INIT;
 	int status;
 
 	ctx->commit_signature_parsed = 1;
@@ -984,13 +986,15 @@ static void parse_commit_signature(struct format_commit_context *ctx)
 		goto out;
 	status = verify_signed_buffer(payload.buf, payload.len,
 				      signature.buf, signature.len,
-				      &gpg_output, NULL);
+				      &gpg_output, &gpg_status);
 	if (status && !gpg_output.len)
 		goto out;
 	ctx->signature.gpg_output = strbuf_detach(&gpg_output, NULL);
+	ctx->signature.gpg_status = strbuf_detach(&gpg_status, NULL);
 	parse_signature_lines(ctx);
 
  out:
+	strbuf_release(&gpg_status);
 	strbuf_release(&gpg_output);
 	strbuf_release(&payload);
 	strbuf_release(&signature);
-- 
1.8.1.3.797.ge0260c7

[PATCH 3/5] gpg_interface: allow to request status return

From: Michael J Gruber <hidden>
Date: 2016-06-15 22:56:09

Currently, verify_signed_buffer() returns the user facing output only.

Allow callers to request the status output also.

Signed-off-by: Michael J Gruber <redacted>
---
 builtin/fmt-merge-msg.c |  2 +-
 builtin/verify-tag.c    |  2 +-
 gpg-interface.c         | 11 +++++++----
 gpg-interface.h         |  2 +-
 log-tree.c              |  4 ++--
 pretty.c                |  2 +-
 6 files changed, 13 insertions(+), 10 deletions(-)
diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index b49612f..265a925 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -492,7 +492,7 @@ 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)) {
+		else if (verify_signed_buffer(buf, len, buf + len, size - len, &sig, NULL)) {
 			if (!sig.len)
 				strbuf_addstr(&sig, "gpg verification failed.\n");
 		}
diff --git a/builtin/verify-tag.c b/builtin/verify-tag.c
index a8eee88..9cdf332 100644
--- a/builtin/verify-tag.c
+++ b/builtin/verify-tag.c
@@ -29,7 +29,7 @@ static int run_gpg_verify(const char *buf, unsigned long size, int verbose)
 	if (size == len)
 		return error("no signature found");
 
-	return verify_signed_buffer(buf, len, buf + len, size - len, NULL);
+	return verify_signed_buffer(buf, len, buf + len, size - len, NULL, NULL);
 }
 
 static int verify_tag(const char *name, int verbose)
diff --git a/gpg-interface.c b/gpg-interface.c
index c582b2e..8b0e874 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -100,13 +100,14 @@ int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *sig
  */
 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_output, struct strbuf *gpg_status)
 {
 	struct child_process gpg;
 	const char *args_gpg[] = {NULL, "--status-fd=1", "--verify", "FILE", "-", NULL};
 	char path[PATH_MAX];
 	int fd, ret;
 	struct strbuf buf = STRBUF_INIT;
+	struct strbuf *pbuf = &buf;
 
 	args_gpg[0] = gpg_program;
 	fd = git_mkstemp(path, PATH_MAX, ".git_vtag_tmpXXXXXX");
@@ -137,15 +138,17 @@ int verify_signed_buffer(const char *payload, size_t payload_size,
 		strbuf_read(gpg_output, gpg.err, 0);
 		close(gpg.err);
 	}
-	strbuf_read(&buf, gpg.out, 0);
+	if (gpg_status)
+		pbuf = gpg_status;
+	strbuf_read(pbuf, gpg.out, 0);
 	close(gpg.out);
 
 	ret = finish_command(&gpg);
 
 	unlink_or_warn(path);
 
-	ret |= !strstr(buf.buf, "\n[GNUPG:] GOODSIG ");
-	strbuf_release(&buf);
+	ret |= !strstr(pbuf->buf, "\n[GNUPG:] GOODSIG ");
+	strbuf_release(&buf); /* no matter it was used or not */
 
 	return ret;
 }
diff --git a/gpg-interface.h b/gpg-interface.h
index b9c3608..cf99021 100644
--- a/gpg-interface.h
+++ b/gpg-interface.h
@@ -2,7 +2,7 @@
 #define GPG_INTERFACE_H
 
 extern int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key);
-extern int verify_signed_buffer(const char *payload, size_t payload_size, const char *signature, size_t signature_size, struct strbuf *gpg_output);
+extern 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);
 extern int git_gpg_config(const char *, const char *, void *);
 extern void set_signing_key(const char *);
 extern const char *get_signing_key(void);
diff --git a/log-tree.c b/log-tree.c
index 912fe08..3d88823 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -444,7 +444,7 @@ static void show_signature(struct rev_info *opt, struct commit *commit)
 
 	status = verify_signed_buffer(payload.buf, payload.len,
 				      signature.buf, signature.len,
-				      &gpg_output);
+				      &gpg_output, NULL);
 	if (status && !gpg_output.len)
 		strbuf_addstr(&gpg_output, "No signature\n");
 
@@ -513,7 +513,7 @@ static void show_one_mergetag(struct rev_info *opt,
 		if (verify_signed_buffer(extra->value, payload_size,
 					 extra->value + payload_size,
 					 extra->len - payload_size,
-					 &verify_message)) {
+					 &verify_message, NULL)) {
 			if (verify_message.len <= gpg_message_offset)
 				strbuf_addstr(&verify_message, "No signature\n");
 			else
diff --git a/pretty.c b/pretty.c
index eae57ad..2a1e174 100644
--- a/pretty.c
+++ b/pretty.c
@@ -984,7 +984,7 @@ static void parse_commit_signature(struct format_commit_context *ctx)
 		goto out;
 	status = verify_signed_buffer(payload.buf, payload.len,
 				      signature.buf, signature.len,
-				      &gpg_output);
+				      &gpg_output, NULL);
 	if (status && !gpg_output.len)
 		goto out;
 	ctx->signature.gpg_output = strbuf_detach(&gpg_output, NULL);
-- 
1.8.1.3.797.ge0260c7

[PATCH 2/5] log-tree: rely upon the check in the gpg_interface

From: Michael J Gruber <hidden>
Date: 2016-06-15 22:56:09

It's just so much betterer.

Signed-off-by: Michael J Gruber <redacted>
---
 log-tree.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)
diff --git a/log-tree.c b/log-tree.c
index 5dc45c4..912fe08 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -508,20 +508,17 @@ static void show_one_mergetag(struct rev_info *opt,
 	gpg_message_offset = verify_message.len;
 
 	payload_size = parse_signature(extra->value, extra->len);
-	if ((extra->len <= payload_size) ||
-	    (verify_signed_buffer(extra->value, payload_size,
-				  extra->value + payload_size,
-				  extra->len - payload_size,
-				  &verify_message) &&
-	     verify_message.len <= gpg_message_offset)) {
-		strbuf_addstr(&verify_message, "No signature\n");
-		status = -1;
-	}
-	else if (strstr(verify_message.buf + gpg_message_offset,
-			": Good signature from "))
-		status = 0;
-	else
-		status = -1;
+	status = -1;
+	if (extra->len > payload_size)
+		if (verify_signed_buffer(extra->value, payload_size,
+					 extra->value + payload_size,
+					 extra->len - payload_size,
+					 &verify_message)) {
+			if (verify_message.len <= gpg_message_offset)
+				strbuf_addstr(&verify_message, "No signature\n");
+			else
+				status = 0;
+		}
 
 	show_sig_lines(opt, status, verify_message.buf);
 	strbuf_release(&verify_message);
-- 
1.8.1.3.797.ge0260c7

[PATCH 1/5] gpg-interface: check good signature in a reliable way

From: Michael J Gruber <hidden>
Date: 2016-06-15 22:56:09

Currently, verify_signed_buffer() only checks the return code of gpg,
and some callers implement additional unreliable checks for "Good
signature" in the gpg output meant for the user.

Use the status output instead and parse for a line beinning with
"[GNUPG:] GOODSIG ". This is the only reliable way of checking for a
good gpg signature.

If needed we can change this easily to "[GNUPG:] VALIDSIG " if we want
to take into account the trust model.

Signed-off-by: Michael J Gruber <redacted>
---
 gpg-interface.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/gpg-interface.c b/gpg-interface.c
index 4559033..c582b2e 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -96,15 +96,17 @@ int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *sig
 /*
  * 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 child_process gpg;
-	const char *args_gpg[] = {NULL, "--verify", "FILE", "-", NULL};
+	const char *args_gpg[] = {NULL, "--status-fd=1", "--verify", "FILE", "-", NULL};
 	char path[PATH_MAX];
 	int fd, ret;
+	struct strbuf buf = STRBUF_INIT;
 
 	args_gpg[0] = gpg_program;
 	fd = git_mkstemp(path, PATH_MAX, ".git_vtag_tmpXXXXXX");
@@ -119,9 +121,10 @@ int verify_signed_buffer(const char *payload, size_t payload_size,
 	memset(&gpg, 0, sizeof(gpg));
 	gpg.argv = args_gpg;
 	gpg.in = -1;
+	gpg.out = -1;
 	if (gpg_output)
 		gpg.err = -1;
-	args_gpg[2] = path;
+	args_gpg[3] = path;
 	if (start_command(&gpg)) {
 		unlink(path);
 		return error(_("could not run gpg."));
@@ -134,9 +137,15 @@ int verify_signed_buffer(const char *payload, size_t payload_size,
 		strbuf_read(gpg_output, gpg.err, 0);
 		close(gpg.err);
 	}
+	strbuf_read(&buf, gpg.out, 0);
+	close(gpg.out);
+
 	ret = finish_command(&gpg);
 
 	unlink_or_warn(path);
 
+	ret |= !strstr(buf.buf, "\n[GNUPG:] GOODSIG ");
+	strbuf_release(&buf);
+
 	return ret;
 }
-- 
1.8.1.3.797.ge0260c7

[PATCH 5/5] pretty: make %GK output the signing key for signed commits

From: Michael J Gruber <hidden>
Date: 2016-06-15 22:56:09

Because we can.

No, really: In order to employ signed keys in an automated way it is
absolutely necessary to check which keys the signatures come from. Now
you can.

Signed-off-by: Michael J Gruber <redacted>
---
 Documentation/pretty-formats.txt | 1 +
 pretty.c                         | 9 ++++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 105f18a..2939655 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -133,6 +133,7 @@ The placeholders are:
 - '%GG': raw verification message from GPG for a signed commit
 - '%G?': show either "G" for Good or "B" for Bad for a signed commit
 - '%GS': show the name of the signer for a signed commit
+- '%GK': show the key used to sign a signed commit
 - '%gD': reflog selector, e.g., `refs/stash@{1}`
 - '%gd': shortened reflog selector, e.g., `stash@{1}`
 - '%gn': reflog identity name
diff --git a/pretty.c b/pretty.c
index 973b912..b57adef 100644
--- a/pretty.c
+++ b/pretty.c
@@ -762,6 +762,7 @@ struct format_commit_context {
 		char *gpg_status;
 		char good_bad;
 		char *signer;
+		char *key;
 	} signature;
 	char *message;
 	size_t width, indent1, indent2;
@@ -964,7 +965,9 @@ static void parse_signature_lines(struct format_commit_context *ctx)
 		if (!found)
 			continue;
 		ctx->signature.good_bad = signature_check[i].result;
-		found += strlen(signature_check[i].check)+17;
+		found += strlen(signature_check[i].check);
+		ctx->signature.key = xmemdupz(found, 16);
+		found += 17;
 		next = strchrnul(found, '\n');
 		ctx->signature.signer = xmemdupz(found, next - found);
 		break;
@@ -1204,6 +1207,10 @@ static size_t format_commit_one(struct strbuf *sb, const char *placeholder,
 			if (c->signature.signer)
 				strbuf_addstr(sb, c->signature.signer);
 			break;
+		case 'K':
+			if (c->signature.key)
+				strbuf_addstr(sb, c->signature.key);
+			break;
 		}
 		return 2;
 	}
-- 
1.8.1.3.797.ge0260c7
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