gpg-interface.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "config.h"
   4 #include "run-command.h"
   5 #include "strbuf.h"
   6 #include "dir.h"
   7 #include "gpg-interface.h"
   8 #include "sigchain.h"
   9 #include "tempfile.h"
  10 #include "alias.h"
  11
  12 static char *configured_signing_key;
  13 static const char *ssh_default_key_command, *ssh_allowed_signers, *ssh_revocation_file;
  14 static enum signature_trust_level configured_min_trust_level = TRUST_UNDEFINED;
  15
  16 struct gpg_format {
  17         const char *name;
  18         const char *program;
  19         const char **verify_args;
  20         const char **sigs;
  21         int (*verify_signed_buffer)(struct signature_check *sigc,
  22                                     struct gpg_format *fmt,
  23                                     const char *signature,
  24                                     size_t signature_size);
  25         int (*sign_buffer)(struct strbuf *buffer, struct strbuf *signature,
  26                            const char *signing_key);
  27         const char *(*get_default_key)(void);
  28         const char *(*get_key_id)(void);
  29 };
  30
  31 static const char *openpgp_verify_args[] = {
  32         "--keyid-format=long",
  33         NULL
  34 };
  35 static const char *openpgp_sigs[] = {
  36         "-----BEGIN PGP SIGNATURE-----",
  37         "-----BEGIN PGP MESSAGE-----",
  38         NULL
  39 };
  40
  41 static const char *x509_verify_args[] = {
  42         NULL
  43 };
  44 static const char *x509_sigs[] = {
  45         "-----BEGIN SIGNED MESSAGE-----",
  46         NULL
  47 };
  48
  49 static const char *ssh_verify_args[] = { NULL };
  50 static const char *ssh_sigs[] = {
  51         "-----BEGIN SSH SIGNATURE-----",
  52         NULL
  53 };
  54
  55 static int verify_gpg_signed_buffer(struct signature_check *sigc,
  56                                     struct gpg_format *fmt,
  57                                     const char *signature,
  58                                     size_t signature_size);
  59 static int verify_ssh_signed_buffer(struct signature_check *sigc,
  60                                     struct gpg_format *fmt,
  61                                     const char *signature,
  62                                     size_t signature_size);
  63 static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
  64                            const char *signing_key);
  65 static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
  66                            const char *signing_key);
  67
  68 static const char *get_default_ssh_signing_key(void);
  69
  70 static const char *get_ssh_key_id(void);
  71
  72 static struct gpg_format gpg_format[] = {
  73         {
  74                 .name = "openpgp",
  75                 .program = "gpg",
  76                 .verify_args = openpgp_verify_args,
  77                 .sigs = openpgp_sigs,
  78                 .verify_signed_buffer = verify_gpg_signed_buffer,
  79                 .sign_buffer = sign_buffer_gpg,
  80                 .get_default_key = NULL,
  81                 .get_key_id = NULL,
  82         },
  83         {
  84                 .name = "x509",
  85                 .program = "gpgsm",
  86                 .verify_args = x509_verify_args,
  87                 .sigs = x509_sigs,
  88                 .verify_signed_buffer = verify_gpg_signed_buffer,
  89                 .sign_buffer = sign_buffer_gpg,
  90                 .get_default_key = NULL,
  91                 .get_key_id = NULL,
  92         },
  93         {
  94                 .name = "ssh",
  95                 .program = "ssh-keygen",
  96                 .verify_args = ssh_verify_args,
  97                 .sigs = ssh_sigs,
  98                 .verify_signed_buffer = verify_ssh_signed_buffer,
  99                 .sign_buffer = sign_buffer_ssh,
 100                 .get_default_key = get_default_ssh_signing_key,
 101                 .get_key_id = get_ssh_key_id,
 102         },
 103 };
 104
 105 static struct gpg_format *use_format = &gpg_format[0];
 106
 107 static struct gpg_format *get_format_by_name(const char *str)
 108 {
 109         int i;
 110
 111         for (i = 0; i < ARRAY_SIZE(gpg_format); i++)
 112                 if (!strcmp(gpg_format[i].name, str))
 113                         return gpg_format + i;
 114         return NULL;
 115 }
 116
 117 static struct gpg_format *get_format_by_sig(const char *sig)
 118 {
 119         int i, j;
 120
 121         for (i = 0; i < ARRAY_SIZE(gpg_format); i++)
 122                 for (j = 0; gpg_format[i].sigs[j]; j++)
 123                         if (starts_with(sig, gpg_format[i].sigs[j]))
 124                                 return gpg_format + i;
 125         return NULL;
 126 }
 127
 128 void signature_check_clear(struct signature_check *sigc)
 129 {
 130         FREE_AND_NULL(sigc->payload);
 131         FREE_AND_NULL(sigc->output);
 132         FREE_AND_NULL(sigc->gpg_status);
 133         FREE_AND_NULL(sigc->signer);
 134         FREE_AND_NULL(sigc->key);
 135         FREE_AND_NULL(sigc->fingerprint);
 136         FREE_AND_NULL(sigc->primary_key_fingerprint);
 137 }
 138
 139 /* An exclusive status -- only one of them can appear in output */
 140 #define GPG_STATUS_EXCLUSIVE    (1<<0)
 141 /* The status includes key identifier */
 142 #define GPG_STATUS_KEYID        (1<<1)
 143 /* The status includes user identifier */
 144 #define GPG_STATUS_UID          (1<<2)
 145 /* The status includes key fingerprints */
 146 #define GPG_STATUS_FINGERPRINT  (1<<3)
 147 /* The status includes trust level */
 148 #define GPG_STATUS_TRUST_LEVEL  (1<<4)
 149
 150 /* Short-hand for standard exclusive *SIG status with keyid & UID */
 151 #define GPG_STATUS_STDSIG       (GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID|GPG_STATUS_UID)
 152
 153 static struct {
 154         char result;
 155         const char *check;
 156         unsigned int flags;
 157 } sigcheck_gpg_status[] = {
 158         { 'G', "GOODSIG ", GPG_STATUS_STDSIG },
 159         { 'B', "BADSIG ", GPG_STATUS_STDSIG },
 160         { 'E', "ERRSIG ", GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID },
 161         { 'X', "EXPSIG ", GPG_STATUS_STDSIG },
 162         { 'Y', "EXPKEYSIG ", GPG_STATUS_STDSIG },
 163         { 'R', "REVKEYSIG ", GPG_STATUS_STDSIG },
 164         { 0, "VALIDSIG ", GPG_STATUS_FINGERPRINT },
 165         { 0, "TRUST_", GPG_STATUS_TRUST_LEVEL },
 166 };
 167
 168 static struct {
 169         const char *key;
 170         enum signature_trust_level value;
 171 } sigcheck_gpg_trust_level[] = {
 172         { "UNDEFINED", TRUST_UNDEFINED },
 173         { "NEVER", TRUST_NEVER },
 174         { "MARGINAL", TRUST_MARGINAL },
 175         { "FULLY", TRUST_FULLY },
 176         { "ULTIMATE", TRUST_ULTIMATE },
 177 };
 178
 179 static void replace_cstring(char **field, const char *line, const char *next)
 180 {
 181         free(*field);
 182
 183         if (line && next)
 184                 *field = xmemdupz(line, next - line);
 185         else
 186                 *field = NULL;
 187 }
 188
 189 static int parse_gpg_trust_level(const char *level,
 190                                  enum signature_trust_level *res)
 191 {
 192         size_t i;
 193
 194         for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_trust_level); i++) {
 195                 if (!strcmp(sigcheck_gpg_trust_level[i].key, level)) {
 196                         *res = sigcheck_gpg_trust_level[i].value;
 197                         return 0;
 198                 }
 199         }
 200         return 1;
 201 }
 202
 203 static void parse_gpg_output(struct signature_check *sigc)
 204 {
 205         const char *buf = sigc->gpg_status;
 206         const char *line, *next;
 207         int i, j;
 208         int seen_exclusive_status = 0;
 209
 210         /* Iterate over all lines */
 211         for (line = buf; *line; line = strchrnul(line+1, '\n')) {
 212                 while (*line == '\n')
 213                         line++;
 214                 if (!*line)
 215                         break;
 216
 217                 /* Skip lines that don't start with GNUPG status */
 218                 if (!skip_prefix(line, "[GNUPG:] ", &line))
 219                         continue;
 220
 221                 /* Iterate over all search strings */
 222                 for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
 223                         if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
 224                                 /*
 225                                  * GOODSIG, BADSIG etc. can occur only once for
 226                                  * each signature.  Therefore, if we had more
 227                                  * than one then we're dealing with multiple
 228                                  * signatures.  We don't support them
 229                                  * currently, and they're rather hard to
 230                                  * create, so something is likely fishy and we
 231                                  * should reject them altogether.
 232                                  */
 233                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
 234                                         if (seen_exclusive_status++)
 235                                                 goto error;
 236                                 }
 237
 238                                 if (sigcheck_gpg_status[i].result)
 239                                         sigc->result = sigcheck_gpg_status[i].result;
 240                                 /* Do we have key information? */
 241                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_KEYID) {
 242                                         next = strchrnul(line, ' ');
 243                                         replace_cstring(&sigc->key, line, next);
 244                                         /* Do we have signer information? */
 245                                         if (*next && (sigcheck_gpg_status[i].flags & GPG_STATUS_UID)) {
 246                                                 line = next + 1;
 247                                                 next = strchrnul(line, '\n');
 248                                                 replace_cstring(&sigc->signer, line, next);
 249                                         }
 250                                 }
 251
 252                                 /* Do we have trust level? */
 253                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_TRUST_LEVEL) {
 254                                         /*
 255                                          * GPG v1 and v2 differs in how the
 256                                          * TRUST_ lines are written.  Some
 257                                          * trust lines contain no additional
 258                                          * space-separated information for v1.
 259                                          */
 260                                         size_t trust_size = strcspn(line, " \n");
 261                                         char *trust = xmemdupz(line, trust_size);
 262
 263                                         if (parse_gpg_trust_level(trust, &sigc->trust_level)) {
 264                                                 free(trust);
 265                                                 goto error;
 266                                         }
 267                                         free(trust);
 268                                 }
 269
 270                                 /* Do we have fingerprint? */
 271                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
 272                                         const char *limit;
 273                                         char **field;
 274
 275                                         next = strchrnul(line, ' ');
 276                                         replace_cstring(&sigc->fingerprint, line, next);
 277
 278                                         /*
 279                                          * Skip interim fields.  The search is
 280                                          * limited to the same line since only
 281                                          * OpenPGP signatures has a field with
 282                                          * the primary fingerprint.
 283                                          */
 284                                         limit = strchrnul(line, '\n');
 285                                         for (j = 9; j > 0; j--) {
 286                                                 if (!*next || limit <= next)
 287                                                         break;
 288                                                 line = next + 1;
 289                                                 next = strchrnul(line, ' ');
 290                                         }
 291
 292                                         field = &sigc->primary_key_fingerprint;
 293                                         if (!j) {
 294                                                 next = strchrnul(line, '\n');
 295                                                 replace_cstring(field, line, next);
 296                                         } else {
 297                                                 replace_cstring(field, NULL, NULL);
 298                                         }
 299                                 }
 300
 301                                 break;
 302                         }
 303                 }
 304         }
 305         return;
 306
 307 error:
 308         sigc->result = 'E';
 309         /* Clear partial data to avoid confusion */
 310         FREE_AND_NULL(sigc->primary_key_fingerprint);
 311         FREE_AND_NULL(sigc->fingerprint);
 312         FREE_AND_NULL(sigc->signer);
 313         FREE_AND_NULL(sigc->key);
 314 }
 315
 316 static int verify_gpg_signed_buffer(struct signature_check *sigc,
 317                                     struct gpg_format *fmt,
 318                                     const char *signature,
 319                                     size_t signature_size)
 320 {
 321         struct child_process gpg = CHILD_PROCESS_INIT;
 322         struct tempfile *temp;
 323         int ret;
 324         struct strbuf gpg_stdout = STRBUF_INIT;
 325         struct strbuf gpg_stderr = STRBUF_INIT;
 326
 327         temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 328         if (!temp)
 329                 return error_errno(_("could not create temporary file"));
 330         if (write_in_full(temp->fd, signature, signature_size) < 0 ||
 331             close_tempfile_gently(temp) < 0) {
 332                 error_errno(_("failed writing detached signature to '%s'"),
 333                             temp->filename.buf);
 334                 delete_tempfile(&temp);
 335                 return -1;
 336         }
 337
 338         strvec_push(&gpg.args, fmt->program);
 339         strvec_pushv(&gpg.args, fmt->verify_args);
 340         strvec_pushl(&gpg.args,
 341                      "--status-fd=1",
 342                      "--verify", temp->filename.buf, "-",
 343                      NULL);
 344
 345         sigchain_push(SIGPIPE, SIG_IGN);
 346         ret = pipe_command(&gpg, sigc->payload, sigc->payload_len, &gpg_stdout, 0,
 347                            &gpg_stderr, 0);
 348         sigchain_pop(SIGPIPE);
 349
 350         delete_tempfile(&temp);
 351
 352         ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
 353         sigc->output = strbuf_detach(&gpg_stderr, NULL);
 354         sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
 355
 356         parse_gpg_output(sigc);
 357
 358         strbuf_release(&gpg_stdout);
 359         strbuf_release(&gpg_stderr);
 360
 361         return ret;
 362 }
 363
 364 static void parse_ssh_output(struct signature_check *sigc)
 365 {
 366         const char *line, *principal, *search;
 367         char *to_free;
 368         char *key = NULL;
 369
 370         /*
 371          * ssh-keygen output should be:
 372          * Good "git" signature for PRINCIPAL with RSA key SHA256:FINGERPRINT
 373          *
 374          * or for valid but unknown keys:
 375          * Good "git" signature with RSA key SHA256:FINGERPRINT
 376          *
 377          * Note that "PRINCIPAL" can contain whitespace, "RSA" and
 378          * "SHA256" part could be a different token that names of
 379          * the algorithms used, and "FINGERPRINT" is a hexadecimal
 380          * string.  By finding the last occurence of " with ", we can
 381          * reliably parse out the PRINCIPAL.
 382          */
 383         sigc->result = 'B';
 384         sigc->trust_level = TRUST_NEVER;
 385
 386         line = to_free = xmemdupz(sigc->output, strcspn(sigc->output, "\n"));
 387
 388         if (skip_prefix(line, "Good \"git\" signature for ", &line)) {
 389                 /* Search for the last "with" to get the full principal */
 390                 principal = line;
 391                 do {
 392                         search = strstr(line, " with ");
 393                         if (search)
 394                                 line = search + 1;
 395                 } while (search != NULL);
 396                 if (line == principal)
 397                         goto cleanup;
 398
 399                 /* Valid signature and known principal */
 400                 sigc->result = 'G';
 401                 sigc->trust_level = TRUST_FULLY;
 402                 sigc->signer = xmemdupz(principal, line - principal - 1);
 403         } else if (skip_prefix(line, "Good \"git\" signature with ", &line)) {
 404                 /* Valid signature, but key unknown */
 405                 sigc->result = 'G';
 406                 sigc->trust_level = TRUST_UNDEFINED;
 407         } else {
 408                 goto cleanup;
 409         }
 410
 411         key = strstr(line, "key ");
 412         if (key) {
 413                 sigc->fingerprint = xstrdup(strstr(line, "key ") + 4);
 414                 sigc->key = xstrdup(sigc->fingerprint);
 415         } else {
 416                 /*
 417                  * Output did not match what we expected
 418                  * Treat the signature as bad
 419                  */
 420                 sigc->result = 'B';
 421         }
 422
 423 cleanup:
 424         free(to_free);
 425 }
 426
 427 static int verify_ssh_signed_buffer(struct signature_check *sigc,
 428                                     struct gpg_format *fmt,
 429                                     const char *signature,
 430                                     size_t signature_size)
 431 {
 432         struct child_process ssh_keygen = CHILD_PROCESS_INIT;
 433         struct tempfile *buffer_file;
 434         int ret = -1;
 435         const char *line;
 436         size_t trust_size;
 437         char *principal;
 438         struct strbuf ssh_principals_out = STRBUF_INIT;
 439         struct strbuf ssh_principals_err = STRBUF_INIT;
 440         struct strbuf ssh_keygen_out = STRBUF_INIT;
 441         struct strbuf ssh_keygen_err = STRBUF_INIT;
 442         struct strbuf verify_time = STRBUF_INIT;
 443         const struct date_mode verify_date_mode = {
 444                 .type = DATE_STRFTIME,
 445                 .strftime_fmt = "%Y%m%d%H%M%S",
 446                 /* SSH signing key validity has no timezone information - Use the local timezone */
 447                 .local = 1,
 448         };
 449
 450         if (!ssh_allowed_signers) {
 451                 error(_("gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification"));
 452                 return -1;
 453         }
 454
 455         buffer_file = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 456         if (!buffer_file)
 457                 return error_errno(_("could not create temporary file"));
 458         if (write_in_full(buffer_file->fd, signature, signature_size) < 0 ||
 459             close_tempfile_gently(buffer_file) < 0) {
 460                 error_errno(_("failed writing detached signature to '%s'"),
 461                             buffer_file->filename.buf);
 462                 delete_tempfile(&buffer_file);
 463                 return -1;
 464         }
 465
 466         if (sigc->payload_timestamp)
 467                 strbuf_addf(&verify_time, "-Overify-time=%s",
 468                         show_date(sigc->payload_timestamp, 0, &verify_date_mode));
 469
 470         /* Find the principal from the signers */
 471         strvec_pushl(&ssh_keygen.args, fmt->program,
 472                      "-Y", "find-principals",
 473                      "-f", ssh_allowed_signers,
 474                      "-s", buffer_file->filename.buf,
 475                      verify_time.buf,
 476                      NULL);
 477         ret = pipe_command(&ssh_keygen, NULL, 0, &ssh_principals_out, 0,
 478                            &ssh_principals_err, 0);
 479         if (ret && strstr(ssh_principals_err.buf, "usage:")) {
 480                 error(_("ssh-keygen -Y find-principals/verify is needed for ssh signature verification (available in openssh version 8.2p1+)"));
 481                 goto out;
 482         }
 483         if (ret || !ssh_principals_out.len) {
 484                 /*
 485                  * We did not find a matching principal in the allowedSigners
 486                  * Check without validation
 487                  */
 488                 child_process_init(&ssh_keygen);
 489                 strvec_pushl(&ssh_keygen.args, fmt->program,
 490                              "-Y", "check-novalidate",
 491                              "-n", "git",
 492                              "-s", buffer_file->filename.buf,
 493                              verify_time.buf,
 494                              NULL);
 495                 pipe_command(&ssh_keygen, sigc->payload, sigc->payload_len,
 496                                    &ssh_keygen_out, 0, &ssh_keygen_err, 0);
 497
 498                 /*
 499                  * Fail on unknown keys
 500                  * we still call check-novalidate to display the signature info
 501                  */
 502                 ret = -1;
 503         } else {
 504                 /* Check every principal we found (one per line) */
 505                 for (line = ssh_principals_out.buf; *line;
 506                      line = strchrnul(line + 1, '\n')) {
 507                         while (*line == '\n')
 508                                 line++;
 509                         if (!*line)
 510                                 break;
 511
 512                         trust_size = strcspn(line, "\n");
 513                         principal = xmemdupz(line, trust_size);
 514
 515                         child_process_init(&ssh_keygen);
 516                         strbuf_release(&ssh_keygen_out);
 517                         strbuf_release(&ssh_keygen_err);
 518                         strvec_push(&ssh_keygen.args, fmt->program);
 519                         /*
 520                          * We found principals
 521                          * Try with each until we find a match
 522                          */
 523                         strvec_pushl(&ssh_keygen.args, "-Y", "verify",
 524                                      "-n", "git",
 525                                      "-f", ssh_allowed_signers,
 526                                      "-I", principal,
 527                                      "-s", buffer_file->filename.buf,
 528                                      verify_time.buf,
 529                                      NULL);
 530
 531                         if (ssh_revocation_file) {
 532                                 if (file_exists(ssh_revocation_file)) {
 533                                         strvec_pushl(&ssh_keygen.args, "-r",
 534                                                      ssh_revocation_file, NULL);
 535                                 } else {
 536                                         warning(_("ssh signing revocation file configured but not found: %s"),
 537                                                 ssh_revocation_file);
 538                                 }
 539                         }
 540
 541                         sigchain_push(SIGPIPE, SIG_IGN);
 542                         ret = pipe_command(&ssh_keygen, sigc->payload, sigc->payload_len,
 543                                            &ssh_keygen_out, 0, &ssh_keygen_err, 0);
 544                         sigchain_pop(SIGPIPE);
 545
 546                         FREE_AND_NULL(principal);
 547
 548                         if (!ret)
 549                                 ret = !starts_with(ssh_keygen_out.buf, "Good");
 550
 551                         if (!ret)
 552                                 break;
 553                 }
 554         }
 555
 556         strbuf_stripspace(&ssh_keygen_out, 0);
 557         strbuf_stripspace(&ssh_keygen_err, 0);
 558         /* Add stderr outputs to show the user actual ssh-keygen errors */
 559         strbuf_add(&ssh_keygen_out, ssh_principals_err.buf, ssh_principals_err.len);
 560         strbuf_add(&ssh_keygen_out, ssh_keygen_err.buf, ssh_keygen_err.len);
 561         sigc->output = strbuf_detach(&ssh_keygen_out, NULL);
 562         sigc->gpg_status = xstrdup(sigc->output);
 563
 564         parse_ssh_output(sigc);
 565
 566 out:
 567         if (buffer_file)
 568                 delete_tempfile(&buffer_file);
 569         strbuf_release(&ssh_principals_out);
 570         strbuf_release(&ssh_principals_err);
 571         strbuf_release(&ssh_keygen_out);
 572         strbuf_release(&ssh_keygen_err);
 573         strbuf_release(&verify_time);
 574
 575         return ret;
 576 }
 577
 578 static int parse_payload_metadata(struct signature_check *sigc)
 579 {
 580         const char *ident_line = NULL;
 581         size_t ident_len;
 582         struct ident_split ident;
 583         const char *signer_header;
 584
 585         switch (sigc->payload_type) {
 586         case SIGNATURE_PAYLOAD_COMMIT:
 587                 signer_header = "committer";
 588                 break;
 589         case SIGNATURE_PAYLOAD_TAG:
 590                 signer_header = "tagger";
 591                 break;
 592         case SIGNATURE_PAYLOAD_UNDEFINED:
 593         case SIGNATURE_PAYLOAD_PUSH_CERT:
 594                 /* Ignore payloads we don't want to parse */
 595                 return 0;
 596         default:
 597                 BUG("invalid value for sigc->payload_type");
 598         }
 599
 600         ident_line = find_commit_header(sigc->payload, signer_header, &ident_len);
 601         if (!ident_line || !ident_len)
 602                 return 1;
 603
 604         if (split_ident_line(&ident, ident_line, ident_len))
 605                 return 1;
 606
 607         if (!sigc->payload_timestamp && ident.date_begin && ident.date_end)
 608                 sigc->payload_timestamp = parse_timestamp(ident.date_begin, NULL, 10);
 609
 610         return 0;
 611 }
 612
 613 int check_signature(struct signature_check *sigc,
 614                     const char *signature, size_t slen)
 615 {
 616         struct gpg_format *fmt;
 617         int status;
 618
 619         sigc->result = 'N';
 620         sigc->trust_level = -1;
 621
 622         fmt = get_format_by_sig(signature);
 623         if (!fmt)
 624                 die(_("bad/incompatible signature '%s'"), signature);
 625
 626         if (parse_payload_metadata(sigc))
 627                 return 1;
 628
 629         status = fmt->verify_signed_buffer(sigc, fmt, signature, slen);
 630
 631         if (status && !sigc->output)
 632                 return !!status;
 633
 634         status |= sigc->result != 'G';
 635         status |= sigc->trust_level < configured_min_trust_level;
 636
 637         return !!status;
 638 }
 639
 640 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 641 {
 642         const char *output = flags & GPG_VERIFY_RAW ? sigc->gpg_status :
 643                                                             sigc->output;
 644
 645         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 646                 fwrite(sigc->payload, 1, sigc->payload_len, stdout);
 647
 648         if (output)
 649                 fputs(output, stderr);
 650 }
 651
 652 size_t parse_signed_buffer(const char *buf, size_t size)
 653 {
 654         size_t len = 0;
 655         size_t match = size;
 656         while (len < size) {
 657                 const char *eol;
 658
 659                 if (get_format_by_sig(buf + len))
 660                         match = len;
 661
 662                 eol = memchr(buf + len, '\n', size - len);
 663                 len += eol ? eol - (buf + len) + 1 : size - len;
 664         }
 665         return match;
 666 }
 667
 668 int parse_signature(const char *buf, size_t size, struct strbuf *payload, struct strbuf *signature)
 669 {
 670         size_t match = parse_signed_buffer(buf, size);
 671         if (match != size) {
 672                 strbuf_add(payload, buf, match);
 673                 remove_signature(payload);
 674                 strbuf_add(signature, buf + match, size - match);
 675                 return 1;
 676         }
 677         return 0;
 678 }
 679
 680 void set_signing_key(const char *key)
 681 {
 682         free(configured_signing_key);
 683         configured_signing_key = xstrdup(key);
 684 }
 685
 686 int git_gpg_config(const char *var, const char *value, void *cb)
 687 {
 688         struct gpg_format *fmt = NULL;
 689         char *fmtname = NULL;
 690         char *trust;
 691         int ret;
 692
 693         if (!strcmp(var, "user.signingkey")) {
 694                 if (!value)
 695                         return config_error_nonbool(var);
 696                 set_signing_key(value);
 697                 return 0;
 698         }
 699
 700         if (!strcmp(var, "gpg.format")) {
 701                 if (!value)
 702                         return config_error_nonbool(var);
 703                 fmt = get_format_by_name(value);
 704                 if (!fmt)
 705                         return error("unsupported value for %s: %s",
 706                                      var, value);
 707                 use_format = fmt;
 708                 return 0;
 709         }
 710
 711         if (!strcmp(var, "gpg.mintrustlevel")) {
 712                 if (!value)
 713                         return config_error_nonbool(var);
 714
 715                 trust = xstrdup_toupper(value);
 716                 ret = parse_gpg_trust_level(trust, &configured_min_trust_level);
 717                 free(trust);
 718
 719                 if (ret)
 720                         return error("unsupported value for %s: %s", var,
 721                                      value);
 722                 return 0;
 723         }
 724
 725         if (!strcmp(var, "gpg.ssh.defaultkeycommand")) {
 726                 if (!value)
 727                         return config_error_nonbool(var);
 728                 return git_config_string(&ssh_default_key_command, var, value);
 729         }
 730
 731         if (!strcmp(var, "gpg.ssh.allowedsignersfile")) {
 732                 if (!value)
 733                         return config_error_nonbool(var);
 734                 return git_config_pathname(&ssh_allowed_signers, var, value);
 735         }
 736
 737         if (!strcmp(var, "gpg.ssh.revocationfile")) {
 738                 if (!value)
 739                         return config_error_nonbool(var);
 740                 return git_config_pathname(&ssh_revocation_file, var, value);
 741         }
 742
 743         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 744                 fmtname = "openpgp";
 745
 746         if (!strcmp(var, "gpg.x509.program"))
 747                 fmtname = "x509";
 748
 749         if (!strcmp(var, "gpg.ssh.program"))
 750                 fmtname = "ssh";
 751
 752         if (fmtname) {
 753                 fmt = get_format_by_name(fmtname);
 754                 return git_config_string(&fmt->program, var, value);
 755         }
 756
 757         return 0;
 758 }
 759
 760 /*
 761  * Returns 1 if `string` contains a literal ssh key, 0 otherwise
 762  * `key` will be set to the start of the actual key if a prefix is present.
 763  */
 764 static int is_literal_ssh_key(const char *string, const char **key)
 765 {
 766         if (skip_prefix(string, "key::", key))
 767                 return 1;
 768         if (starts_with(string, "ssh-")) {
 769                 *key = string;
 770                 return 1;
 771         }
 772         return 0;
 773 }
 774
 775 static char *get_ssh_key_fingerprint(const char *signing_key)
 776 {
 777         struct child_process ssh_keygen = CHILD_PROCESS_INIT;
 778         int ret = -1;
 779         struct strbuf fingerprint_stdout = STRBUF_INIT;
 780         struct strbuf **fingerprint;
 781         char *fingerprint_ret;
 782         const char *literal_key = NULL;
 783
 784         /*
 785          * With SSH Signing this can contain a filename or a public key
 786          * For textual representation we usually want a fingerprint
 787          */
 788         if (is_literal_ssh_key(signing_key, &literal_key)) {
 789                 strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf", "-", NULL);
 790                 ret = pipe_command(&ssh_keygen, literal_key,
 791                                    strlen(literal_key), &fingerprint_stdout, 0,
 792                                    NULL, 0);
 793         } else {
 794                 strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf",
 795                              configured_signing_key, NULL);
 796                 ret = pipe_command(&ssh_keygen, NULL, 0, &fingerprint_stdout, 0,
 797                                    NULL, 0);
 798         }
 799
 800         if (!!ret)
 801                 die_errno(_("failed to get the ssh fingerprint for key '%s'"),
 802                           signing_key);
 803
 804         fingerprint = strbuf_split_max(&fingerprint_stdout, ' ', 3);
 805         if (!fingerprint[1])
 806                 die_errno(_("failed to get the ssh fingerprint for key '%s'"),
 807                           signing_key);
 808
 809         fingerprint_ret = strbuf_detach(fingerprint[1], NULL);
 810         strbuf_list_free(fingerprint);
 811         strbuf_release(&fingerprint_stdout);
 812         return fingerprint_ret;
 813 }
 814
 815 /* Returns the first public key from an ssh-agent to use for signing */
 816 static const char *get_default_ssh_signing_key(void)
 817 {
 818         struct child_process ssh_default_key = CHILD_PROCESS_INIT;
 819         int ret = -1;
 820         struct strbuf key_stdout = STRBUF_INIT, key_stderr = STRBUF_INIT;
 821         struct strbuf **keys;
 822         char *key_command = NULL;
 823         const char **argv;
 824         int n;
 825         char *default_key = NULL;
 826         const char *literal_key = NULL;
 827
 828         if (!ssh_default_key_command)
 829                 die(_("either user.signingkey or gpg.ssh.defaultKeyCommand needs to be configured"));
 830
 831         key_command = xstrdup(ssh_default_key_command);
 832         n = split_cmdline(key_command, &argv);
 833
 834         if (n < 0)
 835                 die("malformed build-time gpg.ssh.defaultKeyCommand: %s",
 836                     split_cmdline_strerror(n));
 837
 838         strvec_pushv(&ssh_default_key.args, argv);
 839         ret = pipe_command(&ssh_default_key, NULL, 0, &key_stdout, 0,
 840                            &key_stderr, 0);
 841
 842         if (!ret) {
 843                 keys = strbuf_split_max(&key_stdout, '\n', 2);
 844                 if (keys[0] && is_literal_ssh_key(keys[0]->buf, &literal_key)) {
 845                         /*
 846                          * We only use `is_literal_ssh_key` here to check validity
 847                          * The prefix will be stripped when the key is used.
 848                          */
 849                         default_key = strbuf_detach(keys[0], NULL);
 850                 } else {
 851                         warning(_("gpg.ssh.defaultKeyCommand succeeded but returned no keys: %s %s"),
 852                                 key_stderr.buf, key_stdout.buf);
 853                 }
 854
 855                 strbuf_list_free(keys);
 856         } else {
 857                 warning(_("gpg.ssh.defaultKeyCommand failed: %s %s"),
 858                         key_stderr.buf, key_stdout.buf);
 859         }
 860
 861         free(key_command);
 862         free(argv);
 863         strbuf_release(&key_stdout);
 864
 865         return default_key;
 866 }
 867
 868 static const char *get_ssh_key_id(void) {
 869         return get_ssh_key_fingerprint(get_signing_key());
 870 }
 871
 872 /* Returns a textual but unique representation of the signing key */
 873 const char *get_signing_key_id(void)
 874 {
 875         if (use_format->get_key_id) {
 876                 return use_format->get_key_id();
 877         }
 878
 879         /* GPG/GPGSM only store a key id on this variable */
 880         return get_signing_key();
 881 }
 882
 883 const char *get_signing_key(void)
 884 {
 885         if (configured_signing_key)
 886                 return configured_signing_key;
 887         if (use_format->get_default_key) {
 888                 return use_format->get_default_key();
 889         }
 890
 891         return git_committer_info(IDENT_STRICT | IDENT_NO_DATE);
 892 }
 893
 894 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 895 {
 896         return use_format->sign_buffer(buffer, signature, signing_key);
 897 }
 898
 899 /*
 900  * Strip CR from the line endings, in case we are on Windows.
 901  * NEEDSWORK: make it trim only CRs before LFs and rename
 902  */
 903 static void remove_cr_after(struct strbuf *buffer, size_t offset)
 904 {
 905         size_t i, j;
 906
 907         for (i = j = offset; i < buffer->len; i++) {
 908                 if (buffer->buf[i] != '\r') {
 909                         if (i != j)
 910                                 buffer->buf[j] = buffer->buf[i];
 911                         j++;
 912                 }
 913         }
 914         strbuf_setlen(buffer, j);
 915 }
 916
 917 static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
 918                           const char *signing_key)
 919 {
 920         struct child_process gpg = CHILD_PROCESS_INIT;
 921         int ret;
 922         size_t bottom;
 923         struct strbuf gpg_status = STRBUF_INIT;
 924
 925         strvec_pushl(&gpg.args,
 926                      use_format->program,
 927                      "--status-fd=2",
 928                      "-bsau", signing_key,
 929                      NULL);
 930
 931         bottom = signature->len;
 932
 933         /*
 934          * When the username signingkey is bad, program could be terminated
 935          * because gpg exits without reading and then write gets SIGPIPE.
 936          */
 937         sigchain_push(SIGPIPE, SIG_IGN);
 938         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 939                            signature, 1024, &gpg_status, 0);
 940         sigchain_pop(SIGPIPE);
 941
 942         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 943         strbuf_release(&gpg_status);
 944         if (ret)
 945                 return error(_("gpg failed to sign the data"));
 946
 947         /* Strip CR from the line endings, in case we are on Windows. */
 948         remove_cr_after(signature, bottom);
 949
 950         return 0;
 951 }
 952
 953 static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
 954                            const char *signing_key)
 955 {
 956         struct child_process signer = CHILD_PROCESS_INIT;
 957         int ret = -1;
 958         size_t bottom, keylen;
 959         struct strbuf signer_stderr = STRBUF_INIT;
 960         struct tempfile *key_file = NULL, *buffer_file = NULL;
 961         char *ssh_signing_key_file = NULL;
 962         struct strbuf ssh_signature_filename = STRBUF_INIT;
 963         const char *literal_key = NULL;
 964
 965         if (!signing_key || signing_key[0] == '\0')
 966                 return error(
 967                         _("user.signingkey needs to be set for ssh signing"));
 968
 969         if (is_literal_ssh_key(signing_key, &literal_key)) {
 970                 /* A literal ssh key */
 971                 key_file = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
 972                 if (!key_file)
 973                         return error_errno(
 974                                 _("could not create temporary file"));
 975                 keylen = strlen(literal_key);
 976                 if (write_in_full(key_file->fd, literal_key, keylen) < 0 ||
 977                     close_tempfile_gently(key_file) < 0) {
 978                         error_errno(_("failed writing ssh signing key to '%s'"),
 979                                     key_file->filename.buf);
 980                         goto out;
 981                 }
 982                 ssh_signing_key_file = strbuf_detach(&key_file->filename, NULL);
 983         } else {
 984                 /* We assume a file */
 985                 ssh_signing_key_file = expand_user_path(signing_key, 1);
 986         }
 987
 988         buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
 989         if (!buffer_file) {
 990                 error_errno(_("could not create temporary file"));
 991                 goto out;
 992         }
 993
 994         if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
 995             close_tempfile_gently(buffer_file) < 0) {
 996                 error_errno(_("failed writing ssh signing key buffer to '%s'"),
 997                             buffer_file->filename.buf);
 998                 goto out;
 999         }
1000
1001         strvec_pushl(&signer.args, use_format->program,
1002                      "-Y", "sign",
1003                      "-n", "git",
1004                      "-f", ssh_signing_key_file,
1005                      buffer_file->filename.buf,
1006                      NULL);
1007
1008         sigchain_push(SIGPIPE, SIG_IGN);
1009         ret = pipe_command(&signer, NULL, 0, NULL, 0, &signer_stderr, 0);
1010         sigchain_pop(SIGPIPE);
1011
1012         if (ret) {
1013                 if (strstr(signer_stderr.buf, "usage:"))
1014                         error(_("ssh-keygen -Y sign is needed for ssh signing (available in openssh version 8.2p1+)"));
1015
1016                 error("%s", signer_stderr.buf);
1017                 goto out;
1018         }
1019
1020         bottom = signature->len;
1021
1022         strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
1023         strbuf_addstr(&ssh_signature_filename, ".sig");
1024         if (strbuf_read_file(signature, ssh_signature_filename.buf, 0) < 0) {
1025                 error_errno(
1026                         _("failed reading ssh signing data buffer from '%s'"),
1027                         ssh_signature_filename.buf);
1028         }
1029         unlink_or_warn(ssh_signature_filename.buf);
1030
1031         /* Strip CR from the line endings, in case we are on Windows. */
1032         remove_cr_after(signature, bottom);
1033
1034 out:
1035         if (key_file)
1036                 delete_tempfile(&key_file);
1037         if (buffer_file)
1038                 delete_tempfile(&buffer_file);
1039         strbuf_release(&signer_stderr);
1040         strbuf_release(&ssh_signature_filename);
1041         FREE_AND_NULL(ssh_signing_key_file);
1042         return ret;
1043 }