git-commit-vandalism/t/t7510-signed-commit.sh
Michał Górny da6cf1b336 gpg-interface.c: detect and reject multiple signatures on commits
GnuPG supports creating signatures consisting of multiple signature
packets.  If such a signature is verified, it outputs all the status
messages for each signature separately.  However, git currently does not
account for such scenario and gets terribly confused over getting
multiple *SIG statuses.

For example, if a malicious party alters a signed commit and appends
a new untrusted signature, git is going to ignore the original bad
signature and report untrusted commit instead.  However, %GK and %GS
format strings may still expand to the data corresponding
to the original signature, potentially tricking the scripts into
trusting the malicious commit.

Given that the use of multiple signatures is quite rare, git does not
support creating them without jumping through a few hoops, and finally
supporting them properly would require extensive API improvement, it
seems reasonable to just reject them at the moment.

Signed-off-by: Michał Górny <mgorny@gentoo.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-10-22 12:42:30 +09:00

264 lines
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Executable File

#!/bin/sh
test_description='signed commit tests'
. ./test-lib.sh
GNUPGHOME_NOT_USED=$GNUPGHOME
. "$TEST_DIRECTORY/lib-gpg.sh"
test_expect_success GPG 'create signed commits' '
test_when_finished "test_unconfig commit.gpgsign" &&
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 master &&
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 -SB7227189 &&
git tag eighth-signed-alt &&
# commit.gpgsign is still on but this must not be signed
git tag ninth-unsigned $(echo 9 | git commit-tree HEAD^{tree}) &&
# explicit -S of course must sign.
git tag tenth-signed $(echo 9 | git commit-tree -S HEAD^{tree})
'
test_expect_success GPG 'verify and show signatures' '
(
for commit in initial second merge fourth-signed \
fifth-signed sixth-signed seventh-signed tenth-signed
do
git verify-commit $commit &&
git show --pretty=short --show-signature $commit >actual &&
grep "Good signature from" actual &&
! grep "BAD signature from" 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 "Good signature from" actual &&
! grep "BAD signature from" actual &&
echo $commit OK || exit 1
done
) &&
(
for commit in eighth-signed-alt
do
git show --pretty=short --show-signature $commit >actual &&
grep "Good signature from" actual &&
! grep "BAD signature from" actual &&
grep "not certified" actual &&
echo $commit OK || exit 1
done
)
'
test_expect_success GPG 'verify-commit exits success on untrusted signature' '
git verify-commit eighth-signed-alt 2>actual &&
grep "Good signature from" actual &&
! grep "BAD signature from" actual &&
grep "not certified" actual
'
test_expect_success GPG 'verify signatures with --raw' '
(
for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
do
git verify-commit --raw $commit 2>actual &&
grep "GOODSIG" actual &&
! grep "BADSIG" 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 "GOODSIG" actual &&
! grep "BADSIG" actual &&
echo $commit OK || exit 1
done
) &&
(
for commit in eighth-signed-alt
do
git verify-commit --raw $commit 2>actual &&
grep "GOODSIG" actual &&
! grep "BADSIG" actual &&
grep "TRUST_UNDEFINED" actual &&
echo $commit OK || exit 1
done
)
'
test_expect_success GPG 'show signed commit with signature' '
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 "gpg: " -e "Warning: " show >show.commit &&
grep -e "gpg: " -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 GPG 'detect fudged signature' '
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 "BAD signature from" actual1 &&
! grep "Good signature from" actual1
'
test_expect_success GPG 'detect fudged signature with NUL' '
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 "BAD signature from" actual2 &&
! grep "Good signature from" actual2
'
test_expect_success GPG 'amending already signed commit' '
git checkout fourth-signed^0 &&
git commit --amend -S --no-edit &&
git verify-commit HEAD &&
git show -s --show-signature HEAD >actual &&
grep "Good signature from" actual &&
! grep "BAD signature from" actual
'
test_expect_success GPG 'show good signature with custom format' '
cat >expect <<-\EOF &&
G
13B6F51ECDDE430D
C O Mitter <committer@example.com>
EOF
git log -1 --format="%G?%n%GK%n%GS" sixth-signed >actual &&
test_cmp expect actual
'
test_expect_success GPG 'show bad signature with custom format' '
cat >expect <<-\EOF &&
B
13B6F51ECDDE430D
C O Mitter <committer@example.com>
EOF
git log -1 --format="%G?%n%GK%n%GS" $(cat forged1.commit) >actual &&
test_cmp expect actual
'
test_expect_success GPG 'show untrusted signature with custom format' '
cat >expect <<-\EOF &&
U
61092E85B7227189
Eris Discordia <discord@example.net>
EOF
git log -1 --format="%G?%n%GK%n%GS" eighth-signed-alt >actual &&
test_cmp expect actual
'
test_expect_success GPG 'show unknown signature with custom format' '
cat >expect <<-\EOF &&
E
61092E85B7227189
EOF
GNUPGHOME="$GNUPGHOME_NOT_USED" git log -1 --format="%G?%n%GK%n%GS" eighth-signed-alt >actual &&
test_cmp expect actual
'
test_expect_success GPG 'show lack of signature with custom format' '
cat >expect <<-\EOF &&
N
EOF
git log -1 --format="%G?%n%GK%n%GS" seventh-unsigned >actual &&
test_cmp expect actual
'
test_expect_success GPG 'log.showsignature behaves like --show-signature' '
test_config log.showsignature true &&
git show initial >actual &&
grep "gpg: Signature made" actual &&
grep "gpg: Good signature" actual
'
test_expect_success GPG 'check config gpg.format values' '
test_config gpg.format openpgp &&
git commit -S --amend -m "success" &&
test_config gpg.format OpEnPgP &&
test_must_fail git commit -S --amend -m "fail"
'
test_expect_success GPG 'detect fudged commit with double signature' '
sed -e "/gpgsig/,/END PGP/d" forged1 >double-base &&
sed -n -e "/gpgsig/,/END PGP/p" forged1 | \
sed -e "s/^gpgsig//;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/^/gpgsig /;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_success GPG 'show double signature with custom format' '
cat >expect <<-\EOF &&
E
EOF
git log -1 --format="%G?%n%GK%n%GS" $(cat double-commit.commit) >actual &&
test_cmp expect actual
'
test_done