This commit introduces command line options for git tag to allow adding trusted
time-stamps from a Time Stamping Authority according to RFC3161.
The SHA-1 has used for a time-stamp signature is generated from the header data
and the tag message, if present. After obtaining the time-stamp signature, it is
inserted into the object header under the `timesig`-key in a custom PEM-like
format. If the tag is also GPG-signed, the GPG signature includes the time-stamp
signature to prevent attackers from altering the time-stamp signature or
replacing it.
However, it is still possible to create tags with only a GPG signature or only a
time-stamp, although it is recommended to additionally GPG-sign time-stamp
signatures for the reasons stated above.
In contrast to the GPG signature, the time-stamp signatures are part of
the header, emulating the way GPG signatures of signed commits are stored. This
facilitates implementing RFC3161 time-stamps for commits eventually.
Signed-off-by: Anton Würfel <anton.wuer...@fau.de>
Signed-off-by: Phillip Raffeck <phillip.raff...@fau.de>
---
builtin/tag.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 52 insertions(+), 3 deletions(-)
diff --git a/builtin/tag.c b/builtin/tag.c
index 1705c94..9b3d2a1 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -18,9 +18,10 @@
#include "sha1-array.h"
#include "column.h"
#include "ref-filter.h"
+#include "rfc3161.h"
static const char * const git_tag_usage[] = {
- N_("git tag [-a | -s | -u <key-id>] [-f] [-m <msg> | -F <file>]
<tagname> [<head>]"),
+ N_("git tag [-a | -s | -u <key-id> | -t] [-f] [-m <msg> | -F <file>]
<tagname> [<head>]"),
N_("git tag -d <tagname>..."),
N_("git tag -l [-n[<num>]] [--contains <commit>] [--points-at <object>]"
"\n\t\t[--format=<format>] [--[no-]merged [<commit>]]
[<pattern>...]"),
@@ -118,6 +119,39 @@ static int do_sign(struct strbuf *buffer)
return sign_buffer(buffer, buffer, get_signing_key());
}
+static int do_timesig(struct strbuf *buffer)
+{
+ struct strbuf sig = STRBUF_INIT;
+ int inspos, copypos;
+
+ /* find the end of the header */
+ inspos = strstr(buffer->buf, "\n\n") - buffer->buf + 1;
+
+ if (create_time_signature(buffer, &sig)) {
+ strbuf_release(&sig);
+ return -1;
+ }
+
+ for (copypos = 0; sig.buf[copypos]; ) {
+ const char *bol = sig.buf + copypos;
+ const char *eol = strchrnul(bol, '\n');
+ int len = (eol - bol) + !!*eol;
+
+ if (!copypos) {
+ strbuf_insert(buffer, inspos, time_sig_header,
+ time_sig_header_len);
+ inspos += time_sig_header_len;
+ }
+ strbuf_insert(buffer, inspos++, " ", 1);
+ strbuf_insert(buffer, inspos, bol, len);
+ inspos += len;
+ copypos += len;
+ }
+ strbuf_release(&sig);
+
+ return 0;
+}
+
static const char tag_template[] =
N_("\nWrite a message for tag:\n %s\n"
"Lines starting with '%c' will be ignored.\n");
@@ -193,8 +227,11 @@ static void write_tag_body(int fd, const unsigned char
*sha1)
free(buf);
}
-static int build_tag_object(struct strbuf *buf, int sign, unsigned char
*result)
+static int build_tag_object(struct strbuf *buf, int sign, int timesig,
+ unsigned char *result)
{
+ if (timesig && do_timesig(buf) < 0)
+ return error(_("unable to generate time-stamp signature"));
if (sign && do_sign(buf) < 0)
return error(_("unable to sign the tag"));
if (write_sha1_file(buf->buf, buf->len, tag_type, result) < 0)
@@ -205,6 +242,7 @@ static int build_tag_object(struct strbuf *buf, int sign,
unsigned char *result)
struct create_tag_options {
unsigned int message_given:1;
unsigned int sign;
+ unsigned int timesig;
enum {
CLEANUP_NONE,
CLEANUP_SPACE,
@@ -276,7 +314,7 @@ static void create_tag(const unsigned char *object, const
char *tag,
strbuf_insert(buf, 0, header_buf, header_len);
- if (build_tag_object(buf, opt->sign, result) < 0) {
+ if (build_tag_object(buf, opt->sign, opt->timesig, result) < 0) {
if (path)
fprintf(stderr, _("The tag message has been left in
%s\n"),
path);
@@ -350,6 +388,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
N_("tag message"), parse_msg_arg),
OPT_FILENAME('F', "file", &msgfile, N_("read message from
file")),
OPT_BOOL('s', "sign", &opt.sign, N_("annotated and GPG-signed
tag")),
+ OPT_BOOL('t', "timestamp", &opt.timesig, N_("add trusted
RFC3161 time-stamp")),
OPT_STRING(0, "cleanup", &cleanup_arg, N_("mode"),
N_("how to strip spaces and #comments from message")),
OPT_STRING('u', "local-user", &keyid, N_("key-id"),
@@ -387,6 +426,16 @@ int cmd_tag(int argc, const char **argv, const char
*prefix)
}
if (opt.sign)
annotate = 1;
+
+#if defined(NO_CURL) || defined(NO_OPENSSL)
+ if (opt.timesig)
+ return error("git has been compiled without RFC3161 time-stamp
support. "
+ "NO_CURL and NO_OPENSSL must not be defined");
+#else
+ if (opt.timesig)
+ annotate = 1;
+#endif
+
if (argc == 0 && !cmdmode)
cmdmode = 'l';
--
2.8.0.rc0.62.gfc8aefa.dirty
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