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git/t/t7510-signed-commit.sh
SZEDER Gábor 2f3cbcd8c5 tests: make forging GPG signed commits and tags more robust
A couple of test scripts create forged GPG signed commits or tags to
check that such forgery can't fool various git commands' signature
verification.  All but one of those test scripts are prone to
occasional failures because the forgery creates a bogus GPG signature,
and git commands error out with an unexpected error message, e.g.
"Commit deadbeef does not have a GPG signature" instead of "...  has a
bad GPG signature".

't5573-pull-verify-signatures.sh', 't7510-signed-commit.sh' and
't7612-merge-verify-signatures.sh' create forged signed commits like
this:

  git commit -S -m "bad on side" &&
  git cat-file commit side-bad >raw &&
  sed -e "s/bad/forged bad/" raw >forged &&
  git hash-object -w -t commit forged >forged.commit

On rare occasions the given pattern occurs not only in the commit
message but in the GPG signature as well, and after it's replaced in
the signature the resulting signature becomes invalid, GPG will report
CRC error and that it couldn't find any signature, which will then
ultimately cause the test failure.

Since in all three cases the pattern to be replaced during the forgery
is the first word of the commit message's subject line, and since the
GPG signature in the commit object is indented by a space, let's just
anchor those patterns to the beginning of the line to prevent this
issue.

The test script 't7030-verify-tag.sh' creates a forged signed tag
object in a similar way by replacing the pattern "seventh", but the
GPG signature in tag objects is not indented by a space, so the above
solution is not applicable in this case.  However, in the tag object
in question the pattern "seventh" occurs not only in the tag message
but in the 'tag' header as well.  To create a forged tag object it's
sufficient to replace only one of the two occurences, so modify the
sed script to limit the pattern to the 'tag' header (i.e. a line
beginning with "tag ", which, because of the space character, can
never occur in the base64-encoded GPG signature).

Note that the forgery in 't7004-tag.sh' is not affected by this issue:
while 't7004' does create a forged signed tag kind of the same way,
it replaces "signed-tag" in the tag object, which, because of the '-'
character, can never occur in the base64-encoded GPG signarute.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-06-11 10:19:03 -07:00

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#!/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_done