[PATCH v6 17/23] receive-pack: GPG-validate push certificates

From

Junio C Hamano <gitster@pobox.com>

Date

Sep 17, 2014, 22:45 UTC

Message-ID

<1410993958-32394-18-git-send-email-gitster@pobox.com>

In-Reply-To

<1410993958-32394-1-git-send-email-gitster@pobox.com>

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Unchanged since v5.

 Documentation/git-receive-pack.txt | 24 +++++++++++++++++++-----
 builtin/receive-pack.c             | 31 +++++++++++++++++++++++++++++++
 t/t5534-push-signed.sh             | 18 ++++++++++++++++--
 3 files changed, 66 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-receive-pack.txt b/Documentation/git-receive-pack.txt
index a2dd743..e6df234 100644
--- a/Documentation/git-receive-pack.txt
+++ b/Documentation/git-receive-pack.txt
@@ -56,7 +56,21 @@ sha1-old and sha1-new should be valid objects in the repository.
 When accepting a signed push (see linkgit:git-push[1]), the signed
 push certificate is stored in a blob and an environment variable
 `GIT_PUSH_CERT` can be consulted for its object name.  See the
-description of `post-receive` hook for an example.
+description of `post-receive` hook for an example.  In addition, the
+certificate is verified using GPG and the result is exported with
+the following environment variables:
+
+`GIT_PUSH_CERT_SIGNER`::
+	The name and the e-mail address of the owner of the key that
+	signed the push certificate.
+
+`GIT_PUSH_CERT_KEY`::
+	The GPG key ID of the key that signed the push certificate.
+
+`GIT_PUSH_CERT_STATUS`::
+	The status of GPG verification of the push certificate,
+	using the same mnemonic as used in `%G?` format of `git log`
+	family of commands (see linkgit:git-log[1]).
 
 This hook is called before any refname is updated and before any
 fast-forward checks are performed.
@@ -106,13 +120,13 @@ the update.  Refs that were created will have sha1-old equal to
 0\{40}, otherwise sha1-old and sha1-new should be valid objects in
 the repository.
 
-The `GIT_PUSH_CERT` environment variable can be inspected, just as
+The `GIT_PUSH_CERT*` environment variables can be inspected, just as
 in `pre-receive` hook, after accepting a signed push.
 
 Using this hook, it is easy to generate mails describing the updates
 to the repository.  This example script sends one mail message per
 ref listing the commits pushed to the repository, and logs the push
-certificates of signed pushes to a logger
+certificates of signed pushes with good signatures to a logger
 service:
 
 	#!/bin/sh
@@ -130,11 +144,11 @@ service:
 		mail -s "Changes to ref $ref" commit-list@mydomain
 	done
 	# log signed push certificate, if any
-	if test -n "${GIT_PUSH_CERT-}"
+	if test -n "${GIT_PUSH_CERT-}" && test ${GIT_PUSH_CERT_STATUS} = G
 	then
 		(
 			git cat-file blob ${GIT_PUSH_CERT}
-		) | mail -s "push certificate" push-log@mydomain
+		) | mail -s "push certificate from $GIT_PUSH_CERT_SIGNER" push-log@mydomain
 	fi
 	exit 0
 
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 610b085..c0a3189 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -15,6 +15,8 @@
 #include "connected.h"
 #include "argv-array.h"
 #include "version.h"
+#include "tag.h"
+#include "gpg-interface.h"
 
 static const char receive_pack_usage[] = "git receive-pack <git-dir>";
 
@@ -49,6 +51,7 @@ static const char *alt_shallow_file;
 static int accept_push_cert = 1;
 static struct strbuf push_cert = STRBUF_INIT;
 static unsigned char push_cert_sha1[20];
+static struct signature_check sigcheck;
 
 static enum deny_action parse_deny_action(const char *var, const char *value)
 {
@@ -277,12 +280,40 @@ static void prepare_push_cert_sha1(struct child_process *proc)
 		return;
 
 	if (!already_done) {
+		struct strbuf gpg_output = STRBUF_INIT;
+		struct strbuf gpg_status = STRBUF_INIT;
+		int bogs /* beginning_of_gpg_sig */;
+
 		already_done = 1;
 		if (write_sha1_file(push_cert.buf, push_cert.len, "blob", push_cert_sha1))
 			hashclr(push_cert_sha1);
+
+		memset(&sigcheck, '\0', sizeof(sigcheck));
+		sigcheck.result = 'N';
+
+		bogs = parse_signature(push_cert.buf, push_cert.len);
+		if (verify_signed_buffer(push_cert.buf, bogs,
+					 push_cert.buf + bogs, push_cert.len - bogs,
+					 &gpg_output, &gpg_status) < 0) {
+			; /* error running gpg */
+		} else {
+			sigcheck.payload = push_cert.buf;
+			sigcheck.gpg_output = gpg_output.buf;
+			sigcheck.gpg_status = gpg_status.buf;
+			parse_gpg_output(&sigcheck);
+		}
+
+		strbuf_release(&gpg_output);
+		strbuf_release(&gpg_status);
 	}
 	if (!is_null_sha1(push_cert_sha1)) {
 		argv_array_pushf(&env, "GIT_PUSH_CERT=%s", sha1_to_hex(push_cert_sha1));
+		argv_array_pushf(&env, "GIT_PUSH_CERT_SIGNER=%s",
+				 sigcheck.signer ? sigcheck.signer : "");
+		argv_array_pushf(&env, "GIT_PUSH_CERT_KEY=%s",
+				 sigcheck.key ? sigcheck.key : "");
+		argv_array_pushf(&env, "GIT_PUSH_CERT_STATUS=%c", sigcheck.result);
+
 		proc->env = env.argv;
 	}
 }
diff --git a/t/t5534-push-signed.sh b/t/t5534-push-signed.sh
index 019ac71..4198b6a 100755
--- a/t/t5534-push-signed.sh
+++ b/t/t5534-push-signed.sh
@@ -83,12 +83,26 @@ test_expect_success GPG 'signed push sends push certificate' '
 	if test -n "${GIT_PUSH_CERT-}"
 	then
 		git cat-file blob $GIT_PUSH_CERT >../push-cert
-	fi
+	fi &&
+
+	cat >../push-cert-status <<E_O_F
+	SIGNER=${GIT_PUSH_CERT_SIGNER-nobody}
+	KEY=${GIT_PUSH_CERT_KEY-nokey}
+	STATUS=${GIT_PUSH_CERT_STATUS-nostatus}
+	E_O_F
+
+	EOF
+
+	cat >expect <<-\EOF &&
+	SIGNER=C O Mitter <committer@example.com>
+	KEY=13B6F51ECDDE430D
+	STATUS=G
 	EOF
 
 	git push --signed dst noop ff +noff &&
 	grep "$(git rev-parse noop ff) refs/heads/ff" dst/push-cert &&
-	grep "$(git rev-parse noop noff) refs/heads/noff" dst/push-cert
+	grep "$(git rev-parse noop noff) refs/heads/noff" dst/push-cert &&
+	test_cmp expect dst/push-cert-status
 '
 
 test_done

-- 
2.1.0-403-g099cf47