commit --amend -S: strip existing gpgsig headers

Any existing commit signature was made against the contents of the old
commit, including its committer date that is about to change, and will
become invalid by amending it.

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

diff --git a/builtin/commit.c b/builtin/commit.c
index fa41ec8c878a6af63e17b79996148be85dcfccef..970a83662a67a8f1c6cb8a67fd2e6636a5260948 100644 (file)
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1494,7 +1494,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
        }
 
        if (amend) {
-               extra = read_commit_extra_headers(current_head);
+               const char *exclude_gpgsig[2] = { "gpgsig", NULL };
+               extra = read_commit_extra_headers(current_head, exclude_gpgsig);
        } else {
                struct commit_extra_header **tail = &extra;
                append_merge_tag_headers(parents, &tail);

diff --git a/commit.c b/commit.c
index 27c7226abbfd95251bc2831a8a6447a8e35f264b..2162a7c5724c1dcdd42b249c11d1995e66abcd6f 100644 (file)
--- a/commit.c
+++ b/commit.c
@@ -981,14 +981,15 @@ static void add_extra_header(struct strbuf *buffer,
                strbuf_addch(buffer, '\n');
 }
 
-struct commit_extra_header *read_commit_extra_headers(struct commit *commit)
+struct commit_extra_header *read_commit_extra_headers(struct commit *commit,
+                                                     const char **exclude)
 {
        struct commit_extra_header *extra = NULL;
        unsigned long size;
        enum object_type type;
        char *buffer = read_sha1_file(commit->object.sha1, &type, &size);
        if (buffer && type == OBJ_COMMIT)
-               extra = read_commit_extra_header_lines(buffer, size);
+               extra = read_commit_extra_header_lines(buffer, size, exclude);
        free(buffer);
        return extra;
 }
@@ -1002,7 +1003,23 @@ static inline int standard_header_field(const char *field, size_t len)
                (len == 8 && !memcmp(field, "encoding ", 9)));
 }
 
-struct commit_extra_header *read_commit_extra_header_lines(const char *buffer, size_t size)
+static int excluded_header_field(const char *field, size_t len, const char **exclude)
+{
+       if (!exclude)
+               return 0;
+
+       while (*exclude) {
+               size_t xlen = strlen(*exclude);
+               if (len == xlen &&
+                   !memcmp(field, *exclude, xlen) && field[xlen] == ' ')
+                       return 1;
+               exclude++;
+       }
+       return 0;
+}
+
+struct commit_extra_header *read_commit_extra_header_lines(const char *buffer, size_t size,
+                                                          const char **exclude)
 {
        struct commit_extra_header *extra = NULL, **tail = &extra, *it = NULL;
        const char *line, *next, *eof, *eob;
@@ -1028,7 +1045,8 @@ struct commit_extra_header *read_commit_extra_header_lines(const char *buffer, s
                if (next <= eof)
                        eof = next;
 
-               if (standard_header_field(line, eof - line))
+               if (standard_header_field(line, eof - line) ||
+                   excluded_header_field(line, eof - line, exclude))
                        continue;
 
                it = xcalloc(1, sizeof(*it));

diff --git a/commit.h b/commit.h
index 61076486df7de2502344039b62ad60f534807cf6..123aea3a7ccf95821d4b4eb5eff9cf7f384d881d 100644 (file)
--- a/commit.h
+++ b/commit.h
@@ -200,8 +200,8 @@ extern int commit_tree_extended(const char *msg, unsigned char *tree,
                                const char *author, const char *sign_commit,
                                struct commit_extra_header *);
 
-extern struct commit_extra_header *read_commit_extra_headers(struct commit *);
-extern struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len);
+extern struct commit_extra_header *read_commit_extra_headers(struct commit *, const char **);
+extern struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **);
 
 extern void free_commit_extra_headers(struct commit_extra_header *extra);
 

diff --git a/t/t7510-signed-commit.sh b/t/t7510-signed-commit.sh
index 30401ced071c24aed5071442da1a9674bc7b7c7e..1d3c56fe61fa995e9bfe2d3a1e4a9fef2c211387 100755 (executable)
--- a/t/t7510-signed-commit.sh
+++ b/t/t7510-signed-commit.sh
@@ -24,7 +24,8 @@ test_expect_success GPG 'create signed commits' '
        echo 4 >file && test_tick && git commit -a -m "fourth unsigned" &&
        git tag fourth-unsigned &&
 
-       test_tick && git commit --amend -S -m "fourth signed"
+       test_tick && git commit --amend -S -m "fourth signed" &&
+       git tag fourth-signed
 '
 
 test_expect_success GPG 'show signatures' '
@@ -68,4 +69,12 @@ test_expect_success GPG 'detect fudged signature with NUL' '
        ! 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 show -s --show-signature HEAD >actual &&
+       grep "Good signature from" actual &&
+       ! grep "BAD signature from" actual
+'
+
 test_done