merge/pull: verify GPG signatures of commits being merged

When --verify-signatures is specified on the command-line of git-merge
or git-pull, check whether the commits being merged have good gpg
signatures and abort the merge in case they do not. This allows e.g.
auto-deployment from untrusted repo hosts.

Signed-off-by: Sebastian Götte <jaseg@physik-pool.tu-berlin.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/merge-options.txt b/Documentation/merge-options.txt
index 0bcbe0ac3c474ab12068f468476946b9db5ef3e8..31f106752152ea0a915ceaea148cf4cad555de99 100644 (file)
--- a/Documentation/merge-options.txt
+++ b/Documentation/merge-options.txt
@@ -83,6 +83,11 @@ option can be used to override --squash.
        Pass merge strategy specific option through to the merge
        strategy.
 
+--verify-signatures::
+--no-verify-signatures::
+       Verify that the commits being merged have good GPG signatures and abort the
+       merge in case they do not.
+
 --summary::
 --no-summary::
        Synonyms to --stat and --no-stat; these are deprecated and will be

diff --git a/builtin/merge.c b/builtin/merge.c
index 7c8922c8b0b44307a0dbb43329301ad7d1654a46..e57c42c622b0d92c08bebf8eca8560503fe78b80 100644 (file)
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -49,7 +49,7 @@ static const char * const builtin_merge_usage[] = {
 static int show_diffstat = 1, shortlog_len = -1, squash;
 static int option_commit = 1, allow_fast_forward = 1;
 static int fast_forward_only, option_edit = -1;
-static int allow_trivial = 1, have_message;
+static int allow_trivial = 1, have_message, verify_signatures;
 static int overwrite_ignore = 1;
 static struct strbuf merge_msg = STRBUF_INIT;
 static struct strategy **use_strategies;
@@ -199,6 +199,8 @@ static struct option builtin_merge_options[] = {
        OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
                N_("abort if fast-forward is not possible")),
        OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
+       OPT_BOOL(0, "verify-signatures", &verify_signatures,
+               N_("Verify that the named commit has a valid GPG signature")),
        OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
                N_("merge strategy to use"), option_parse_strategy),
        OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
@@ -1233,6 +1235,36 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
                usage_with_options(builtin_merge_usage,
                        builtin_merge_options);
 
+       if (verify_signatures) {
+               for (p = remoteheads; p; p = p->next) {
+                       struct commit *commit = p->item;
+                       char hex[41];
+                       struct signature_check signature_check;
+                       memset(&signature_check, 0, sizeof(signature_check));
+
+                       check_commit_signature(commit, &signature_check);
+
+                       strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
+                       switch (signature_check.result) {
+                       case 'G':
+                               break;
+                       case 'B':
+                               die(_("Commit %s has a bad GPG signature "
+                                     "allegedly by %s."), hex, signature_check.signer);
+                       default: /* 'N' */
+                               die(_("Commit %s does not have a GPG signature."), hex);
+                       }
+                       if (verbosity >= 0 && signature_check.result == 'G')
+                               printf(_("Commit %s has a good GPG signature by %s\n"),
+                                      hex, signature_check.signer);
+
+                       free(signature_check.gpg_output);
+                       free(signature_check.gpg_status);
+                       free(signature_check.signer);
+                       free(signature_check.key);
+               }
+       }
+
        strbuf_addstr(&buf, "merge");
        for (p = remoteheads; p; p = p->next)
                strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);

diff --git a/git-pull.sh b/git-pull.sh
index 5d97e97bd95fe25d158058af025c48e47f6d241f..638aabb7b347e2afeb9bf327902de9e3702cd9d4 100755 (executable)
--- a/git-pull.sh
+++ b/git-pull.sh
@@ -39,7 +39,7 @@ test -z "$(git ls-files -u)" || die_conflict
 test -f "$GIT_DIR/MERGE_HEAD" && die_merge
 
 strategy_args= diffstat= no_commit= squash= no_ff= ff_only=
-log_arg= verbosity= progress= recurse_submodules=
+log_arg= verbosity= progress= recurse_submodules= verify_signatures=
 merge_args= edit=
 curr_branch=$(git symbolic-ref -q HEAD)
 curr_branch_short="${curr_branch#refs/heads/}"
@@ -125,6 +125,12 @@ do
        --no-recurse-submodules)
                recurse_submodules=--no-recurse-submodules
                ;;
+       --verify-signatures)
+               verify_signatures=--verify-signatures
+               ;;
+       --no-verify-signatures)
+               verify_signatures=--no-verify-signatures
+               ;;
        --d|--dr|--dry|--dry-|--dry-r|--dry-ru|--dry-run)
                dry_run=--dry-run
                ;;
@@ -283,7 +289,7 @@ true)
        eval="$eval --onto $merge_head ${oldremoteref:-$merge_head}"
        ;;
 *)
-       eval="git-merge $diffstat $no_commit $edit $squash $no_ff $ff_only"
+       eval="git-merge $diffstat $no_commit $verify_signatures $edit $squash $no_ff $ff_only"
        eval="$eval  $log_arg $strategy_args $merge_args $verbosity $progress"
        eval="$eval \"\$merge_name\" HEAD $merge_head"
        ;;

diff --git a/t/t7612-merge-verify-signatures.sh b/t/t7612-merge-verify-signatures.sh
new file mode 100755 (executable)
index 0000000..6ccfbf3
--- /dev/null
+++ b/t/t7612-merge-verify-signatures.sh
@@ -0,0 +1,52 @@
+#!/bin/sh
+
+test_description='merge signature verification tests'
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-gpg.sh"
+
+test_expect_success GPG 'create signed commits' '
+       echo 1 >file && git add file &&
+       test_tick && git commit -m initial &&
+       git tag initial &&
+
+       git checkout -b side-signed &&
+       echo 3 >elif && git add elif &&
+       test_tick && git commit -S -m "signed on side" &&
+       git checkout initial &&
+
+       git checkout -b side-unsigned &&
+       echo 3 >foo && git add foo &&
+       test_tick && git commit -m "unsigned on side" &&
+       git checkout initial &&
+
+       git checkout -b side-bad &&
+       echo 3 >bar && git add bar &&
+       test_tick && 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 &&
+       git checkout initial &&
+
+       git checkout master
+'
+
+test_expect_success GPG 'merge unsigned commit with verification' '
+       test_must_fail git merge --ff-only --verify-signatures side-unsigned 2>mergeerror &&
+       test_i18ngrep "does not have a GPG signature" mergeerror
+'
+
+test_expect_success GPG 'merge commit with bad signature with verification' '
+       test_must_fail git merge --ff-only --verify-signatures $(cat forged.commit) 2>mergeerror &&
+       test_i18ngrep "has a bad GPG signature" mergeerror
+'
+
+test_expect_success GPG 'merge signed commit with verification' '
+       git merge --verbose --ff-only --verify-signatures side-signed >mergeoutput &&
+       test_i18ngrep "has a good GPG signature" mergeoutput
+'
+
+test_expect_success GPG 'merge commit with bad signature without verification' '
+       git merge $(cat forged.commit)
+'
+
+test_done