Merge branch 'fs/ssh-signing' into fs/ssh-signing-fix

* fs/ssh-signing:
  ssh signing: test that gpg fails for unknown keys
  ssh signing: tests for logs, tags & push certs
  ssh signing: duplicate t7510 tests for commits
  ssh signing: verify signatures using ssh-keygen
  ssh signing: provide a textual signing_key_id
  ssh signing: retrieve a default key from ssh-agent
  ssh signing: add ssh key format and signing code
  ssh signing: add test prereqs
  ssh signing: preliminary refactoring and clean-up

6 files changed, 739 insertions, 1 deletions

diff --git a/t/lib-gpg.sh b/t/lib-gpg.sh
index 9fc5241228..f99ef3e859 100644
--- a/t/lib-gpg.sh
+++ b/t/lib-gpg.sh
@@ -87,6 +87,34 @@ test_lazy_prereq RFC1991 '
 	echo | gpg --homedir "${GNUPGHOME}" -b --rfc1991 >/dev/null
 '
 
+GPGSSH_KEY_PRIMARY="${GNUPGHOME}/ed25519_ssh_signing_key"
+GPGSSH_KEY_SECONDARY="${GNUPGHOME}/rsa_2048_ssh_signing_key"
+GPGSSH_KEY_UNTRUSTED="${GNUPGHOME}/untrusted_ssh_signing_key"
+GPGSSH_KEY_WITH_PASSPHRASE="${GNUPGHOME}/protected_ssh_signing_key"
+GPGSSH_KEY_PASSPHRASE="super_secret"
+GPGSSH_ALLOWED_SIGNERS="${GNUPGHOME}/ssh.all_valid.allowedSignersFile"
+
+GPGSSH_GOOD_SIGNATURE_TRUSTED='Good "git" signature for'
+GPGSSH_GOOD_SIGNATURE_UNTRUSTED='Good "git" signature with'
+GPGSSH_KEY_NOT_TRUSTED="No principal matched"
+GPGSSH_BAD_SIGNATURE="Signature verification failed"
+
+test_lazy_prereq GPGSSH '
+	ssh_version=$(ssh-keygen -Y find-principals -n "git" 2>&1)
+	test $? != 127 || exit 1
+	echo $ssh_version | grep -q "find-principals:missing signature file"
+	test $? = 0 || exit 1;
+	mkdir -p "${GNUPGHOME}" &&
+	chmod 0700 "${GNUPGHOME}" &&
+	ssh-keygen -t ed25519 -N "" -C "git ed25519 key" -f "${GPGSSH_KEY_PRIMARY}" >/dev/null &&
+	echo "\"principal with number 1\" $(cat "${GPGSSH_KEY_PRIMARY}.pub")" >> "${GPGSSH_ALLOWED_SIGNERS}" &&
+	ssh-keygen -t rsa -b 2048 -N "" -C "git rsa2048 key" -f "${GPGSSH_KEY_SECONDARY}" >/dev/null &&
+	echo "\"principal with number 2\" $(cat "${GPGSSH_KEY_SECONDARY}.pub")" >> "${GPGSSH_ALLOWED_SIGNERS}" &&
+	ssh-keygen -t ed25519 -N "${GPGSSH_KEY_PASSPHRASE}" -C "git ed25519 encrypted key" -f "${GPGSSH_KEY_WITH_PASSPHRASE}" >/dev/null &&
+	echo "\"principal with number 3\" $(cat "${GPGSSH_KEY_WITH_PASSPHRASE}.pub")" >> "${GPGSSH_ALLOWED_SIGNERS}" &&
+	ssh-keygen -t ed25519 -N "" -f "${GPGSSH_KEY_UNTRUSTED}" >/dev/null
+'
+
 sanitize_pgp() {
 	perl -ne '
 		/^-----END PGP/ and $in_pgp = 0;
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index 9dfead936b..6a650dacd6 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -1616,6 +1616,16 @@ test_expect_success GPGSM 'setup signed branch x509' '
 	git commit -S -m signed_commit
 '
 
+test_expect_success GPGSSH 'setup sshkey signed branch' '
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${GPGSSH_KEY_PRIMARY}" &&
+	test_when_finished "git reset --hard && git checkout main" &&
+	git checkout -b signed-ssh main &&
+	echo foo >foo &&
+	git add foo &&
+	git commit -S -m signed_commit
+'
+
 test_expect_success GPGSM 'log x509 fingerprint' '
 	echo "F8BF62E0693D0694816377099909C779FA23FD65 | " >expect &&
 	git log -n1 --format="%GF | %GP" signed-x509 >actual &&
@@ -1628,6 +1638,13 @@ test_expect_success GPGSM 'log OpenPGP fingerprint' '
 	test_cmp expect actual
 '
 
+test_expect_success GPGSSH 'log ssh key fingerprint' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	ssh-keygen -lf  "${GPGSSH_KEY_PRIMARY}" | awk "{print \$2\" | \"}" >expect &&
+	git log -n1 --format="%GF | %GP" signed-ssh >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success GPG 'log --graph --show-signature' '
 	git log --graph --show-signature -n1 signed >actual &&
 	grep "^| gpg: Signature made" actual &&
@@ -1640,6 +1657,12 @@ test_expect_success GPGSM 'log --graph --show-signature x509' '
 	grep "^| gpgsm: Good signature" actual
 '
 
+test_expect_success GPGSSH 'log --graph --show-signature ssh' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git log --graph --show-signature -n1 signed-ssh >actual &&
+	grep "${GOOD_SIGNATURE_TRUSTED}" actual
+'
+
 test_expect_success GPG 'log --graph --show-signature for merged tag' '
 	test_when_finished "git reset --hard && git checkout main" &&
 	git checkout -b plain main &&
diff --git a/t/t5534-push-signed.sh b/t/t5534-push-signed.sh
index bba768f5de..24d374adba 100755
--- a/t/t5534-push-signed.sh
+++ b/t/t5534-push-signed.sh
@@ -137,6 +137,53 @@ test_expect_success GPG 'signed push sends push certificate' '
 	test_cmp expect dst/push-cert-status
 '
 
+test_expect_success GPGSSH 'ssh signed push sends push certificate' '
+	prepare_dst &&
+	mkdir -p dst/.git/hooks &&
+	git -C dst config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git -C dst config receive.certnonceseed sekrit &&
+	write_script dst/.git/hooks/post-receive <<-\EOF &&
+	# discard the update list
+	cat >/dev/null
+	# record the push certificate
+	if test -n "${GIT_PUSH_CERT-}"
+	then
+		git cat-file blob $GIT_PUSH_CERT >../push-cert
+	fi &&
+
+	cat >../push-cert-status <<E_O_F
+	SIGNER=${GIT_PUSH_CERT_SIGNER-nobody}
+	KEY=${GIT_PUSH_CERT_KEY-nokey}
+	STATUS=${GIT_PUSH_CERT_STATUS-nostatus}
+	NONCE_STATUS=${GIT_PUSH_CERT_NONCE_STATUS-nononcestatus}
+	NONCE=${GIT_PUSH_CERT_NONCE-nononce}
+	E_O_F
+
+	EOF
+
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${GPGSSH_KEY_PRIMARY}" &&
+	FINGERPRINT=$(ssh-keygen -lf "${GPGSSH_KEY_PRIMARY}" | awk "{print \$2;}") &&
+	git push --signed dst noop ff +noff &&
+
+	(
+		cat <<-\EOF &&
+		SIGNER=principal with number 1
+		KEY=FINGERPRINT
+		STATUS=G
+		NONCE_STATUS=OK
+		EOF
+		sed -n -e "s/^nonce /NONCE=/p" -e "/^$/q" dst/push-cert
+	) | sed -e "s|FINGERPRINT|$FINGERPRINT|" >expect &&
+
+	noop=$(git rev-parse noop) &&
+	ff=$(git rev-parse ff) &&
+	noff=$(git rev-parse noff) &&
+	grep "$noop $ff refs/heads/ff" dst/push-cert &&
+	grep "$noop $noff refs/heads/noff" dst/push-cert &&
+	test_cmp expect dst/push-cert-status
+'
+
 test_expect_success GPG 'inconsistent push options in signed push not allowed' '
 	# First, invoke receive-pack with dummy input to obtain its preamble.
 	prepare_dst &&
@@ -276,6 +323,60 @@ test_expect_success GPGSM 'fail without key and heed user.signingkey x509' '
 	test_cmp expect dst/push-cert-status
 '
 
+test_expect_success GPGSSH 'fail without key and heed user.signingkey ssh' '
+	test_config gpg.format ssh &&
+	prepare_dst &&
+	mkdir -p dst/.git/hooks &&
+	git -C dst config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git -C dst config receive.certnonceseed sekrit &&
+	write_script dst/.git/hooks/post-receive <<-\EOF &&
+	# discard the update list
+	cat >/dev/null
+	# record the push certificate
+	if test -n "${GIT_PUSH_CERT-}"
+	then
+		git cat-file blob $GIT_PUSH_CERT >../push-cert
+	fi &&
+
+	cat >../push-cert-status <<E_O_F
+	SIGNER=${GIT_PUSH_CERT_SIGNER-nobody}
+	KEY=${GIT_PUSH_CERT_KEY-nokey}
+	STATUS=${GIT_PUSH_CERT_STATUS-nostatus}
+	NONCE_STATUS=${GIT_PUSH_CERT_NONCE_STATUS-nononcestatus}
+	NONCE=${GIT_PUSH_CERT_NONCE-nononce}
+	E_O_F
+
+	EOF
+
+	test_config user.email hasnokey@nowhere.com &&
+	test_config gpg.format ssh &&
+	test_config user.signingkey "" &&
+	(
+		sane_unset GIT_COMMITTER_EMAIL &&
+		test_must_fail git push --signed dst noop ff +noff
+	) &&
+	test_config user.signingkey "${GPGSSH_KEY_PRIMARY}" &&
+	FINGERPRINT=$(ssh-keygen -lf "${GPGSSH_KEY_PRIMARY}" | awk "{print \$2;}") &&
+	git push --signed dst noop ff +noff &&
+
+	(
+		cat <<-\EOF &&
+		SIGNER=principal with number 1
+		KEY=FINGERPRINT
+		STATUS=G
+		NONCE_STATUS=OK
+		EOF
+		sed -n -e "s/^nonce /NONCE=/p" -e "/^$/q" dst/push-cert
+	) | sed -e "s|FINGERPRINT|$FINGERPRINT|" >expect &&
+
+	noop=$(git rev-parse noop) &&
+	ff=$(git rev-parse ff) &&
+	noff=$(git rev-parse noff) &&
+	grep "$noop $ff refs/heads/ff" dst/push-cert &&
+	grep "$noop $noff refs/heads/noff" dst/push-cert &&
+	test_cmp expect dst/push-cert-status
+'
+
 test_expect_success GPG 'failed atomic push does not execute GPG' '
 	prepare_dst &&
 	git -C dst config receive.certnonceseed sekrit &&
diff --git a/t/t7031-verify-tag-signed-ssh.sh b/t/t7031-verify-tag-signed-ssh.sh
new file mode 100755
index 0000000000..06c9dd6c93
--- /dev/null
+++ b/t/t7031-verify-tag-signed-ssh.sh
@@ -0,0 +1,161 @@
+#!/bin/sh
+
+test_description='signed tag tests'
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-gpg.sh"
+
+test_expect_success GPGSSH 'create signed tags ssh' '
+	test_when_finished "test_unconfig commit.gpgsign" &&
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${GPGSSH_KEY_PRIMARY}" &&
+
+	echo 1 >file && git add file &&
+	test_tick && git commit -m initial &&
+	git tag -s -m initial initial &&
+	git branch side &&
+
+	echo 2 >file && test_tick && git commit -a -m second &&
+	git tag -s -m second second &&
+
+	git checkout side &&
+	echo 3 >elif && git add elif &&
+	test_tick && git commit -m "third on side" &&
+
+	git checkout main &&
+	test_tick && git merge -S side &&
+	git tag -s -m merge merge &&
+
+	echo 4 >file && test_tick && git commit -a -S -m "fourth unsigned" &&
+	git tag -a -m fourth-unsigned fourth-unsigned &&
+
+	test_tick && git commit --amend -S -m "fourth signed" &&
+	git tag -s -m fourth fourth-signed &&
+
+	echo 5 >file && test_tick && git commit -a -m "fifth" &&
+	git tag fifth-unsigned &&
+
+	git config commit.gpgsign true &&
+	echo 6 >file && test_tick && git commit -a -m "sixth" &&
+	git tag -a -m sixth sixth-unsigned &&
+
+	test_tick && git rebase -f HEAD^^ && git tag -s -m 6th sixth-signed HEAD^ &&
+	git tag -m seventh -s seventh-signed &&
+
+	echo 8 >file && test_tick && git commit -a -m eighth &&
+	git tag -u"${GPGSSH_KEY_UNTRUSTED}" -m eighth eighth-signed-alt
+'
+
+test_expect_success GPGSSH 'verify and show ssh signatures' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	(
+		for tag in initial second merge fourth-signed sixth-signed seventh-signed
+		do
+			git verify-tag $tag 2>actual &&
+			grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $tag OK || exit 1
+		done
+	) &&
+	(
+		for tag in fourth-unsigned fifth-unsigned sixth-unsigned
+		do
+			test_must_fail git verify-tag $tag 2>actual &&
+			! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $tag OK || exit 1
+		done
+	) &&
+	(
+		for tag in eighth-signed-alt
+		do
+			test_must_fail git verify-tag $tag 2>actual &&
+			grep "${GPGSSH_GOOD_SIGNATURE_UNTRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			grep "${GPGSSH_KEY_NOT_TRUSTED}" actual &&
+			echo $tag OK || exit 1
+		done
+	)
+'
+
+test_expect_success GPGSSH 'detect fudged ssh signature' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git cat-file tag seventh-signed >raw &&
+	sed -e "/^tag / s/seventh/7th forged/" raw >forged1 &&
+	git hash-object -w -t tag forged1 >forged1.tag &&
+	test_must_fail git verify-tag $(cat forged1.tag) 2>actual1 &&
+	grep "${GPGSSH_BAD_SIGNATURE}" actual1 &&
+	! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual1 &&
+	! grep "${GPGSSH_GOOD_SIGNATURE_UNTRUSTED}" actual1
+'
+
+test_expect_success GPGSSH 'verify ssh signatures with --raw' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	(
+		for tag in initial second merge fourth-signed sixth-signed seventh-signed
+		do
+			git verify-tag --raw $tag 2>actual &&
+			grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $tag OK || exit 1
+		done
+	) &&
+	(
+		for tag in fourth-unsigned fifth-unsigned sixth-unsigned
+		do
+			test_must_fail git verify-tag --raw $tag 2>actual &&
+			! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $tag OK || exit 1
+		done
+	) &&
+	(
+		for tag in eighth-signed-alt
+		do
+			test_must_fail git verify-tag --raw $tag 2>actual &&
+			grep "${GPGSSH_GOOD_SIGNATURE_UNTRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $tag OK || exit 1
+		done
+	)
+'
+
+test_expect_success GPGSSH 'verify signatures with --raw ssh' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git verify-tag --raw sixth-signed 2>actual &&
+	grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+	! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+	echo sixth-signed OK
+'
+
+test_expect_success GPGSSH 'verify multiple tags ssh' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	tags="seventh-signed sixth-signed" &&
+	for i in $tags
+	do
+		git verify-tag -v --raw $i || return 1
+	done >expect.stdout 2>expect.stderr.1 &&
+	grep "^${GPGSSH_GOOD_SIGNATURE_TRUSTED}" <expect.stderr.1 >expect.stderr &&
+	git verify-tag -v --raw $tags >actual.stdout 2>actual.stderr.1 &&
+	grep "^${GPGSSH_GOOD_SIGNATURE_TRUSTED}" <actual.stderr.1 >actual.stderr &&
+	test_cmp expect.stdout actual.stdout &&
+	test_cmp expect.stderr actual.stderr
+'
+
+test_expect_success GPGSSH 'verifying tag with --format - ssh' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	cat >expect <<-\EOF &&
+	tagname : fourth-signed
+	EOF
+	git verify-tag --format="tagname : %(tag)" "fourth-signed" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'verifying a forged tag with --format should fail silently - ssh' '
+	test_must_fail git verify-tag --format="tagname : %(tag)" $(cat forged1.tag) >actual-forged &&
+	test_must_be_empty actual-forged
+'
+
+test_done
diff --git a/t/t7510-signed-commit.sh b/t/t7510-signed-commit.sh
index 8df5a74f1d..d65a0171f2 100755
--- a/t/t7510-signed-commit.sh
+++ b/t/t7510-signed-commit.sh
@@ -71,7 +71,25 @@ test_expect_success GPG 'create signed commits' '
 	git tag eleventh-signed $(cat oid) &&
 	echo 12 | git commit-tree --gpg-sign=B7227189 HEAD^{tree} >oid &&
 	test_line_count = 1 oid &&
-	git tag twelfth-signed-alt $(cat oid)
+	git tag twelfth-signed-alt $(cat oid) &&
+
+	cat >keydetails <<-\EOF &&
+	Key-Type: RSA
+	Key-Length: 2048
+	Subkey-Type: RSA
+	Subkey-Length: 2048
+	Name-Real: Unknown User
+	Name-Email: unknown@git.com
+	Expire-Date: 0
+	%no-ask-passphrase
+	%no-protection
+	EOF
+	gpg --batch --gen-key keydetails &&
+	echo 13 >file && git commit -a -S"unknown@git.com" -m thirteenth &&
+	git tag thirteenth-signed &&
+	DELETE_FINGERPRINT=$(gpg -K --with-colons --fingerprint --batch unknown@git.com | grep "^fpr" | head -n 1 | awk -F ":" "{print \$10;}") &&
+	gpg --batch --yes --delete-secret-keys $DELETE_FINGERPRINT &&
+	gpg --batch --yes --delete-keys unknown@git.com
 '
 
 test_expect_success GPG 'verify and show signatures' '
@@ -110,6 +128,13 @@ test_expect_success GPG 'verify and show signatures' '
 	)
 '
 
+test_expect_success GPG 'verify-commit exits failure on unknown signature' '
+	test_must_fail git verify-commit thirteenth-signed 2>actual &&
+	! grep "Good signature from" actual &&
+	! grep "BAD signature from" actual &&
+	grep -q -F -e "No public key" -e "public key not found" actual
+'
+
 test_expect_success GPG 'verify-commit exits success on untrusted signature' '
 	git verify-commit eighth-signed-alt 2>actual &&
 	grep "Good signature from" actual &&
@@ -338,6 +363,8 @@ test_expect_success GPG 'show double signature with custom format' '
 '
 
 
+# NEEDSWORK: This test relies on the test_tick commit/author dates from the first
+# 'create signed commits' test even though it creates its own
 test_expect_success GPG 'verify-commit verifies multiply signed commits' '
 	git init multiply-signed &&
 	cd multiply-signed &&
diff --git a/t/t7528-signed-commit-ssh.sh b/t/t7528-signed-commit-ssh.sh
new file mode 100755
index 0000000000..badf3ed320
--- /dev/null
+++ b/t/t7528-signed-commit-ssh.sh
@@ -0,0 +1,398 @@
+#!/bin/sh
+
+test_description='ssh signed commit tests'
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+. ./test-lib.sh
+GNUPGHOME_NOT_USED=$GNUPGHOME
+. "$TEST_DIRECTORY/lib-gpg.sh"
+
+test_expect_success GPGSSH 'create signed commits' '
+	test_oid_cache <<-\EOF &&
+	header sha1:gpgsig
+	header sha256:gpgsig-sha256
+	EOF
+
+	test_when_finished "test_unconfig commit.gpgsign" &&
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${GPGSSH_KEY_PRIMARY}" &&
+
+	echo 1 >file && git add file &&
+	test_tick && git commit -S -m initial &&
+	git tag initial &&
+	git branch side &&
+
+	echo 2 >file && test_tick && git commit -a -S -m second &&
+	git tag second &&
+
+	git checkout side &&
+	echo 3 >elif && git add elif &&
+	test_tick && git commit -m "third on side" &&
+
+	git checkout main &&
+	test_tick && git merge -S side &&
+	git tag merge &&
+
+	echo 4 >file && test_tick && git commit -a -m "fourth unsigned" &&
+	git tag fourth-unsigned &&
+
+	test_tick && git commit --amend -S -m "fourth signed" &&
+	git tag fourth-signed &&
+
+	git config commit.gpgsign true &&
+	echo 5 >file && test_tick && git commit -a -m "fifth signed" &&
+	git tag fifth-signed &&
+
+	git config commit.gpgsign false &&
+	echo 6 >file && test_tick && git commit -a -m "sixth" &&
+	git tag sixth-unsigned &&
+
+	git config commit.gpgsign true &&
+	echo 7 >file && test_tick && git commit -a -m "seventh" --no-gpg-sign &&
+	git tag seventh-unsigned &&
+
+	test_tick && git rebase -f HEAD^^ && git tag sixth-signed HEAD^ &&
+	git tag seventh-signed &&
+
+	echo 8 >file && test_tick && git commit -a -m eighth -S"${GPGSSH_KEY_UNTRUSTED}" &&
+	git tag eighth-signed-alt &&
+
+	# commit.gpgsign is still on but this must not be signed
+	echo 9 | git commit-tree HEAD^{tree} >oid &&
+	test_line_count = 1 oid &&
+	git tag ninth-unsigned $(cat oid) &&
+	# explicit -S of course must sign.
+	echo 10 | git commit-tree -S HEAD^{tree} >oid &&
+	test_line_count = 1 oid &&
+	git tag tenth-signed $(cat oid) &&
+
+	# --gpg-sign[=<key-id>] must sign.
+	echo 11 | git commit-tree --gpg-sign HEAD^{tree} >oid &&
+	test_line_count = 1 oid &&
+	git tag eleventh-signed $(cat oid) &&
+	echo 12 | git commit-tree --gpg-sign="${GPGSSH_KEY_UNTRUSTED}" HEAD^{tree} >oid &&
+	test_line_count = 1 oid &&
+	git tag twelfth-signed-alt $(cat oid)
+'
+
+test_expect_success GPGSSH 'verify and show signatures' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	test_config gpg.mintrustlevel UNDEFINED &&
+	(
+		for commit in initial second merge fourth-signed \
+			fifth-signed sixth-signed seventh-signed tenth-signed \
+			eleventh-signed
+		do
+			git verify-commit $commit &&
+			git show --pretty=short --show-signature $commit >actual &&
+			grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in merge^2 fourth-unsigned sixth-unsigned \
+			seventh-unsigned ninth-unsigned
+		do
+			test_must_fail git verify-commit $commit &&
+			git show --pretty=short --show-signature $commit >actual &&
+			! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in eighth-signed-alt twelfth-signed-alt
+		do
+			git show --pretty=short --show-signature $commit >actual &&
+			grep "${GPGSSH_GOOD_SIGNATURE_UNTRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			grep "${GPGSSH_KEY_NOT_TRUSTED}" actual &&
+			echo $commit OK || exit 1
+		done
+	)
+'
+
+test_expect_success GPGSSH 'verify-commit exits failure on untrusted signature' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	test_must_fail git verify-commit eighth-signed-alt 2>actual &&
+	grep "${GPGSSH_GOOD_SIGNATURE_UNTRUSTED}" actual &&
+	! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+	grep "${GPGSSH_KEY_NOT_TRUSTED}" actual
+'
+
+test_expect_success GPGSSH 'verify-commit exits success with matching minTrustLevel' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	test_config gpg.minTrustLevel fully &&
+	git verify-commit sixth-signed
+'
+
+test_expect_success GPGSSH 'verify-commit exits success with low minTrustLevel' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	test_config gpg.minTrustLevel marginal &&
+	git verify-commit sixth-signed
+'
+
+test_expect_success GPGSSH 'verify-commit exits failure with high minTrustLevel' '
+	test_config gpg.minTrustLevel ultimate &&
+	test_must_fail git verify-commit eighth-signed-alt
+'
+
+test_expect_success GPGSSH 'verify signatures with --raw' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	(
+		for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
+		do
+			git verify-commit --raw $commit 2>actual &&
+			grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in merge^2 fourth-unsigned sixth-unsigned seventh-unsigned
+		do
+			test_must_fail git verify-commit --raw $commit 2>actual &&
+			! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in eighth-signed-alt
+		do
+			test_must_fail git verify-commit --raw $commit 2>actual &&
+			grep "${GPGSSH_GOOD_SIGNATURE_UNTRUSTED}" actual &&
+			! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	)
+'
+
+test_expect_success GPGSSH 'proper header is used for hash algorithm' '
+	git cat-file commit fourth-signed >output &&
+	grep "^$(test_oid header) -----BEGIN SSH SIGNATURE-----" output
+'
+
+test_expect_success GPGSSH 'show signed commit with signature' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git show -s initial >commit &&
+	git show -s --show-signature initial >show &&
+	git verify-commit -v initial >verify.1 2>verify.2 &&
+	git cat-file commit initial >cat &&
+	grep -v -e "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" -e "Warning: " show >show.commit &&
+	grep -e "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" -e "Warning: " show >show.gpg &&
+	grep -v "^ " cat | grep -v "^gpgsig.* " >cat.commit &&
+	test_cmp show.commit commit &&
+	test_cmp show.gpg verify.2 &&
+	test_cmp cat.commit verify.1
+'
+
+test_expect_success GPGSSH 'detect fudged signature' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git cat-file commit seventh-signed >raw &&
+	sed -e "s/^seventh/7th forged/" raw >forged1 &&
+	git hash-object -w -t commit forged1 >forged1.commit &&
+	test_must_fail git verify-commit $(cat forged1.commit) &&
+	git show --pretty=short --show-signature $(cat forged1.commit) >actual1 &&
+	grep "${GPGSSH_BAD_SIGNATURE}" actual1 &&
+	! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual1 &&
+	! grep "${GPGSSH_GOOD_SIGNATURE_UNTRUSTED}" actual1
+'
+
+test_expect_success GPGSSH 'detect fudged signature with NUL' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git cat-file commit seventh-signed >raw &&
+	cat raw >forged2 &&
+	echo Qwik | tr "Q" "\000" >>forged2 &&
+	git hash-object -w -t commit forged2 >forged2.commit &&
+	test_must_fail git verify-commit $(cat forged2.commit) &&
+	git show --pretty=short --show-signature $(cat forged2.commit) >actual2 &&
+	grep "${GPGSSH_BAD_SIGNATURE}" actual2 &&
+	! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual2
+'
+
+test_expect_success GPGSSH 'amending already signed commit' '
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${GPGSSH_KEY_PRIMARY}" &&
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git checkout fourth-signed^0 &&
+	git commit --amend -S --no-edit &&
+	git verify-commit HEAD &&
+	git show -s --show-signature HEAD >actual &&
+	grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+	! grep "${GPGSSH_BAD_SIGNATURE}" actual
+'
+
+test_expect_success GPGSSH 'show good signature with custom format' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	FINGERPRINT=$(ssh-keygen -lf "${GPGSSH_KEY_PRIMARY}" | awk "{print \$2;}") &&
+	cat >expect.tmpl <<-\EOF &&
+	G
+	FINGERPRINT
+	principal with number 1
+	FINGERPRINT
+
+	EOF
+	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" sixth-signed >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show bad signature with custom format' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	cat >expect <<-\EOF &&
+	B
+
+
+
+
+	EOF
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" $(cat forged1.commit) >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show untrusted signature with custom format' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	cat >expect.tmpl <<-\EOF &&
+	U
+	FINGERPRINT
+
+	FINGERPRINT
+
+	EOF
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" eighth-signed-alt >actual &&
+	FINGERPRINT=$(ssh-keygen -lf "${GPGSSH_KEY_UNTRUSTED}" | awk "{print \$2;}") &&
+	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show untrusted signature with undefined trust level' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	cat >expect.tmpl <<-\EOF &&
+	undefined
+	FINGERPRINT
+
+	FINGERPRINT
+
+	EOF
+	git log -1 --format="%GT%n%GK%n%GS%n%GF%n%GP" eighth-signed-alt >actual &&
+	FINGERPRINT=$(ssh-keygen -lf "${GPGSSH_KEY_UNTRUSTED}" | awk "{print \$2;}") &&
+	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show untrusted signature with ultimate trust level' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	cat >expect.tmpl <<-\EOF &&
+	fully
+	FINGERPRINT
+	principal with number 1
+	FINGERPRINT
+
+	EOF
+	git log -1 --format="%GT%n%GK%n%GS%n%GF%n%GP" sixth-signed >actual &&
+	FINGERPRINT=$(ssh-keygen -lf "${GPGSSH_KEY_PRIMARY}" | awk "{print \$2;}") &&
+	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show lack of signature with custom format' '
+	cat >expect <<-\EOF &&
+	N
+
+
+
+
+	EOF
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" seventh-unsigned >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'log.showsignature behaves like --show-signature' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	test_config log.showsignature true &&
+	git show initial >actual &&
+	grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual
+'
+
+test_expect_success GPGSSH 'check config gpg.format values' '
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${GPGSSH_KEY_PRIMARY}" &&
+	test_config gpg.format ssh &&
+	git commit -S --amend -m "success" &&
+	test_config gpg.format OpEnPgP &&
+	test_must_fail git commit -S --amend -m "fail"
+'
+
+test_expect_failure GPGSSH 'detect fudged commit with double signature (TODO)' '
+	sed -e "/gpgsig/,/END PGP/d" forged1 >double-base &&
+	sed -n -e "/gpgsig/,/END PGP/p" forged1 | \
+		sed -e "s/^$(test_oid header)//;s/^ //" | gpg --dearmor >double-sig1.sig &&
+	gpg -o double-sig2.sig -u 29472784 --detach-sign double-base &&
+	cat double-sig1.sig double-sig2.sig | gpg --enarmor >double-combined.asc &&
+	sed -e "s/^\(-.*\)ARMORED FILE/\1SIGNATURE/;1s/^/$(test_oid header) /;2,\$s/^/ /" \
+		double-combined.asc > double-gpgsig &&
+	sed -e "/committer/r double-gpgsig" double-base >double-commit &&
+	git hash-object -w -t commit double-commit >double-commit.commit &&
+	test_must_fail git verify-commit $(cat double-commit.commit) &&
+	git show --pretty=short --show-signature $(cat double-commit.commit) >double-actual &&
+	grep "BAD signature from" double-actual &&
+	grep "Good signature from" double-actual
+'
+
+test_expect_failure GPGSSH 'show double signature with custom format (TODO)' '
+	cat >expect <<-\EOF &&
+	E
+
+
+
+
+	EOF
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" $(cat double-commit.commit) >actual &&
+	test_cmp expect actual
+'
+
+
+test_expect_failure GPGSSH 'verify-commit verifies multiply signed commits (TODO)' '
+	git init multiply-signed &&
+	cd multiply-signed &&
+	test_commit first &&
+	echo 1 >second &&
+	git add second &&
+	tree=$(git write-tree) &&
+	parent=$(git rev-parse HEAD^{commit}) &&
+	git commit --gpg-sign -m second &&
+	git cat-file commit HEAD &&
+	# Avoid trailing whitespace.
+	sed -e "s/^Q//" -e "s/^Z/ /" >commit <<-EOF &&
+	Qtree $tree
+	Qparent $parent
+	Qauthor A U Thor <author@example.com> 1112912653 -0700
+	Qcommitter C O Mitter <committer@example.com> 1112912653 -0700
+	Qgpgsig -----BEGIN PGP SIGNATURE-----
+	QZ
+	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBDRYcY29tbWl0dGVy
+	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMNd+8AoK1I8mhLHviPH+q2I5fIVgPsEtYC
+	Q AKCTqBh+VabJceXcGIZuF0Ry+udbBQ==
+	Q =tQ0N
+	Q -----END PGP SIGNATURE-----
+	Qgpgsig-sha256 -----BEGIN PGP SIGNATURE-----
+	QZ
+	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBIBYcY29tbWl0dGVy
+	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMN/NEAn0XO9RYSBj2dFyozi0JKSbssYMtO
+	Q AJwKCQ1BQOtuwz//IjU8TiS+6S4iUw==
+	Q =pIwP
+	Q -----END PGP SIGNATURE-----
+	Q
+	Qsecond
+	EOF
+	head=$(git hash-object -t commit -w commit) &&
+	git reset --hard $head &&
+	git verify-commit $head 2>actual &&
+	grep "Good signature from" actual &&
+	! grep "BAD signature from" actual
+'
+
+test_done