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![brian m. carlson](/assets/img/avatar_default.png)
When we have a multiply signed commit, we need to remove the signature in the header before verifying the object, since the trailing signature will not be over both pieces of data. Do so, and verify that we validate the signature appropriately. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
483 lines
12 KiB
C
483 lines
12 KiB
C
#include "cache.h"
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#include "commit.h"
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#include "config.h"
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#include "run-command.h"
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#include "strbuf.h"
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#include "gpg-interface.h"
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#include "sigchain.h"
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#include "tempfile.h"
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static char *configured_signing_key;
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static enum signature_trust_level configured_min_trust_level = TRUST_UNDEFINED;
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struct gpg_format {
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const char *name;
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const char *program;
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const char **verify_args;
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const char **sigs;
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};
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static const char *openpgp_verify_args[] = {
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"--keyid-format=long",
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NULL
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};
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static const char *openpgp_sigs[] = {
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"-----BEGIN PGP SIGNATURE-----",
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"-----BEGIN PGP MESSAGE-----",
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NULL
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};
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static const char *x509_verify_args[] = {
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NULL
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};
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static const char *x509_sigs[] = {
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"-----BEGIN SIGNED MESSAGE-----",
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NULL
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};
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static struct gpg_format gpg_format[] = {
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{ .name = "openpgp", .program = "gpg",
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.verify_args = openpgp_verify_args,
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.sigs = openpgp_sigs
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},
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{ .name = "x509", .program = "gpgsm",
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.verify_args = x509_verify_args,
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.sigs = x509_sigs
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},
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};
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static struct gpg_format *use_format = &gpg_format[0];
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static struct gpg_format *get_format_by_name(const char *str)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(gpg_format); i++)
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if (!strcmp(gpg_format[i].name, str))
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return gpg_format + i;
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return NULL;
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}
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static struct gpg_format *get_format_by_sig(const char *sig)
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{
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int i, j;
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for (i = 0; i < ARRAY_SIZE(gpg_format); i++)
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for (j = 0; gpg_format[i].sigs[j]; j++)
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if (starts_with(sig, gpg_format[i].sigs[j]))
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return gpg_format + i;
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return NULL;
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}
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void signature_check_clear(struct signature_check *sigc)
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{
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FREE_AND_NULL(sigc->payload);
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FREE_AND_NULL(sigc->gpg_output);
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FREE_AND_NULL(sigc->gpg_status);
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FREE_AND_NULL(sigc->signer);
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FREE_AND_NULL(sigc->key);
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FREE_AND_NULL(sigc->fingerprint);
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FREE_AND_NULL(sigc->primary_key_fingerprint);
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}
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/* An exclusive status -- only one of them can appear in output */
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#define GPG_STATUS_EXCLUSIVE (1<<0)
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/* The status includes key identifier */
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#define GPG_STATUS_KEYID (1<<1)
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/* The status includes user identifier */
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#define GPG_STATUS_UID (1<<2)
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/* The status includes key fingerprints */
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#define GPG_STATUS_FINGERPRINT (1<<3)
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/* The status includes trust level */
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#define GPG_STATUS_TRUST_LEVEL (1<<4)
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/* Short-hand for standard exclusive *SIG status with keyid & UID */
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#define GPG_STATUS_STDSIG (GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID|GPG_STATUS_UID)
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static struct {
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char result;
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const char *check;
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unsigned int flags;
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} sigcheck_gpg_status[] = {
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{ 'G', "GOODSIG ", GPG_STATUS_STDSIG },
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{ 'B', "BADSIG ", GPG_STATUS_STDSIG },
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{ 'E', "ERRSIG ", GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID },
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{ 'X', "EXPSIG ", GPG_STATUS_STDSIG },
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{ 'Y', "EXPKEYSIG ", GPG_STATUS_STDSIG },
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{ 'R', "REVKEYSIG ", GPG_STATUS_STDSIG },
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{ 0, "VALIDSIG ", GPG_STATUS_FINGERPRINT },
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{ 0, "TRUST_", GPG_STATUS_TRUST_LEVEL },
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};
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static struct {
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const char *key;
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enum signature_trust_level value;
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} sigcheck_gpg_trust_level[] = {
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{ "UNDEFINED", TRUST_UNDEFINED },
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{ "NEVER", TRUST_NEVER },
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{ "MARGINAL", TRUST_MARGINAL },
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{ "FULLY", TRUST_FULLY },
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{ "ULTIMATE", TRUST_ULTIMATE },
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};
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static void replace_cstring(char **field, const char *line, const char *next)
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{
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free(*field);
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if (line && next)
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*field = xmemdupz(line, next - line);
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else
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*field = NULL;
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}
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static int parse_gpg_trust_level(const char *level,
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enum signature_trust_level *res)
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{
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size_t i;
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for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_trust_level); i++) {
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if (!strcmp(sigcheck_gpg_trust_level[i].key, level)) {
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*res = sigcheck_gpg_trust_level[i].value;
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return 0;
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}
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}
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return 1;
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}
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static void parse_gpg_output(struct signature_check *sigc)
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{
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const char *buf = sigc->gpg_status;
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const char *line, *next;
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int i, j;
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int seen_exclusive_status = 0;
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/* Iterate over all lines */
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for (line = buf; *line; line = strchrnul(line+1, '\n')) {
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while (*line == '\n')
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line++;
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if (!*line)
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break;
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/* Skip lines that don't start with GNUPG status */
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if (!skip_prefix(line, "[GNUPG:] ", &line))
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continue;
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/* Iterate over all search strings */
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for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
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if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
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/*
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* GOODSIG, BADSIG etc. can occur only once for
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* each signature. Therefore, if we had more
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* than one then we're dealing with multiple
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* signatures. We don't support them
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* currently, and they're rather hard to
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* create, so something is likely fishy and we
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* should reject them altogether.
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*/
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if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
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if (seen_exclusive_status++)
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goto error;
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}
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if (sigcheck_gpg_status[i].result)
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sigc->result = sigcheck_gpg_status[i].result;
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/* Do we have key information? */
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if (sigcheck_gpg_status[i].flags & GPG_STATUS_KEYID) {
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next = strchrnul(line, ' ');
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replace_cstring(&sigc->key, line, next);
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/* Do we have signer information? */
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if (*next && (sigcheck_gpg_status[i].flags & GPG_STATUS_UID)) {
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line = next + 1;
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next = strchrnul(line, '\n');
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replace_cstring(&sigc->signer, line, next);
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}
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}
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/* Do we have trust level? */
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if (sigcheck_gpg_status[i].flags & GPG_STATUS_TRUST_LEVEL) {
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/*
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* GPG v1 and v2 differs in how the
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* TRUST_ lines are written. Some
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* trust lines contain no additional
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* space-separated information for v1.
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*/
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size_t trust_size = strcspn(line, " \n");
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char *trust = xmemdupz(line, trust_size);
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if (parse_gpg_trust_level(trust, &sigc->trust_level)) {
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free(trust);
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goto error;
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}
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free(trust);
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}
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/* Do we have fingerprint? */
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if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
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const char *limit;
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char **field;
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next = strchrnul(line, ' ');
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replace_cstring(&sigc->fingerprint, line, next);
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/*
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* Skip interim fields. The search is
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* limited to the same line since only
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* OpenPGP signatures has a field with
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* the primary fingerprint.
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*/
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limit = strchrnul(line, '\n');
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for (j = 9; j > 0; j--) {
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if (!*next || limit <= next)
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break;
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line = next + 1;
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next = strchrnul(line, ' ');
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}
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field = &sigc->primary_key_fingerprint;
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if (!j) {
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next = strchrnul(line, '\n');
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replace_cstring(field, line, next);
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} else {
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replace_cstring(field, NULL, NULL);
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}
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}
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break;
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}
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}
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}
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return;
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error:
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sigc->result = 'E';
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/* Clear partial data to avoid confusion */
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FREE_AND_NULL(sigc->primary_key_fingerprint);
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FREE_AND_NULL(sigc->fingerprint);
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FREE_AND_NULL(sigc->signer);
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FREE_AND_NULL(sigc->key);
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}
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static int verify_signed_buffer(const char *payload, size_t payload_size,
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const char *signature, size_t signature_size,
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struct strbuf *gpg_output,
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struct strbuf *gpg_status)
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{
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struct child_process gpg = CHILD_PROCESS_INIT;
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struct gpg_format *fmt;
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struct tempfile *temp;
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int ret;
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struct strbuf buf = STRBUF_INIT;
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temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
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if (!temp)
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return error_errno(_("could not create temporary file"));
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if (write_in_full(temp->fd, signature, signature_size) < 0 ||
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close_tempfile_gently(temp) < 0) {
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error_errno(_("failed writing detached signature to '%s'"),
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temp->filename.buf);
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delete_tempfile(&temp);
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return -1;
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}
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fmt = get_format_by_sig(signature);
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if (!fmt)
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BUG("bad signature '%s'", signature);
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strvec_push(&gpg.args, fmt->program);
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strvec_pushv(&gpg.args, fmt->verify_args);
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strvec_pushl(&gpg.args,
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"--status-fd=1",
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"--verify", temp->filename.buf, "-",
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NULL);
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if (!gpg_status)
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gpg_status = &buf;
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sigchain_push(SIGPIPE, SIG_IGN);
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ret = pipe_command(&gpg, payload, payload_size,
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gpg_status, 0, gpg_output, 0);
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sigchain_pop(SIGPIPE);
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delete_tempfile(&temp);
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ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
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strbuf_release(&buf); /* no matter it was used or not */
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return ret;
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}
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int check_signature(const char *payload, size_t plen, const char *signature,
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size_t slen, struct signature_check *sigc)
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{
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struct strbuf gpg_output = STRBUF_INIT;
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struct strbuf gpg_status = STRBUF_INIT;
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int status;
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sigc->result = 'N';
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sigc->trust_level = -1;
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status = verify_signed_buffer(payload, plen, signature, slen,
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&gpg_output, &gpg_status);
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if (status && !gpg_output.len)
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goto out;
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sigc->payload = xmemdupz(payload, plen);
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sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
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sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
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parse_gpg_output(sigc);
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status |= sigc->result != 'G';
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status |= sigc->trust_level < configured_min_trust_level;
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out:
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strbuf_release(&gpg_status);
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strbuf_release(&gpg_output);
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return !!status;
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}
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void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
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{
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const char *output = flags & GPG_VERIFY_RAW ?
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sigc->gpg_status : sigc->gpg_output;
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if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
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fputs(sigc->payload, stdout);
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if (output)
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fputs(output, stderr);
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}
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size_t parse_signed_buffer(const char *buf, size_t size)
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{
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size_t len = 0;
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size_t match = size;
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while (len < size) {
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const char *eol;
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if (get_format_by_sig(buf + len))
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match = len;
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eol = memchr(buf + len, '\n', size - len);
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len += eol ? eol - (buf + len) + 1 : size - len;
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}
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return match;
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}
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int parse_signature(const char *buf, size_t size, struct strbuf *payload, struct strbuf *signature)
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{
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size_t match = parse_signed_buffer(buf, size);
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if (match != size) {
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strbuf_add(payload, buf, match);
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remove_signature(payload);
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strbuf_add(signature, buf + match, size - match);
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return 1;
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}
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return 0;
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}
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void set_signing_key(const char *key)
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{
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free(configured_signing_key);
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configured_signing_key = xstrdup(key);
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}
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int git_gpg_config(const char *var, const char *value, void *cb)
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{
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struct gpg_format *fmt = NULL;
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char *fmtname = NULL;
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char *trust;
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int ret;
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if (!strcmp(var, "user.signingkey")) {
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if (!value)
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return config_error_nonbool(var);
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set_signing_key(value);
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return 0;
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}
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if (!strcmp(var, "gpg.format")) {
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if (!value)
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return config_error_nonbool(var);
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fmt = get_format_by_name(value);
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if (!fmt)
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return error("unsupported value for %s: %s",
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var, value);
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use_format = fmt;
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return 0;
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}
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if (!strcmp(var, "gpg.mintrustlevel")) {
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if (!value)
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return config_error_nonbool(var);
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trust = xstrdup_toupper(value);
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ret = parse_gpg_trust_level(trust, &configured_min_trust_level);
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free(trust);
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if (ret)
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return error("unsupported value for %s: %s", var,
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value);
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return 0;
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}
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if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
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fmtname = "openpgp";
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if (!strcmp(var, "gpg.x509.program"))
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fmtname = "x509";
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if (fmtname) {
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fmt = get_format_by_name(fmtname);
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return git_config_string(&fmt->program, var, value);
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}
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return 0;
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}
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const char *get_signing_key(void)
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{
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if (configured_signing_key)
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return configured_signing_key;
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return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
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}
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int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
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{
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struct child_process gpg = CHILD_PROCESS_INIT;
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int ret;
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size_t i, j, bottom;
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struct strbuf gpg_status = STRBUF_INIT;
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strvec_pushl(&gpg.args,
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use_format->program,
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"--status-fd=2",
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"-bsau", signing_key,
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NULL);
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bottom = signature->len;
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/*
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* When the username signingkey is bad, program could be terminated
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* because gpg exits without reading and then write gets SIGPIPE.
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*/
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sigchain_push(SIGPIPE, SIG_IGN);
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ret = pipe_command(&gpg, buffer->buf, buffer->len,
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signature, 1024, &gpg_status, 0);
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sigchain_pop(SIGPIPE);
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ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
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strbuf_release(&gpg_status);
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if (ret)
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return error(_("gpg failed to sign the data"));
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/* Strip CR from the line endings, in case we are on Windows. */
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for (i = j = bottom; i < signature->len; i++)
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if (signature->buf[i] != '\r') {
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if (i != j)
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signature->buf[j] = signature->buf[i];
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j++;
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}
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strbuf_setlen(signature, j);
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return 0;
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}
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