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 /* Keep the order same as enum signature_trust_level */
 169 static struct sigcheck_gpg_trust_level {
 170         const char *key;
 171         const char *display_key;
 172         enum signature_trust_level value;
 173 } sigcheck_gpg_trust_level[] = {
 174         { "UNDEFINED", "undefined", TRUST_UNDEFINED },
 175         { "NEVER", "never", TRUST_NEVER },
 176         { "MARGINAL", "marginal", TRUST_MARGINAL },
 177         { "FULLY", "fully", TRUST_FULLY },
 178         { "ULTIMATE", "ultimate", TRUST_ULTIMATE },
 179 };
 180
 181 static void replace_cstring(char **field, const char *line, const char *next)
 182 {
 183         free(*field);
 184
 185         if (line && next)
 186                 *field = xmemdupz(line, next - line);
 187         else
 188                 *field = NULL;
 189 }
 190
 191 static int parse_gpg_trust_level(const char *level,
 192                                  enum signature_trust_level *res)
 193 {
 194         size_t i;
 195
 196         for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_trust_level); i++) {
 197                 if (!strcmp(sigcheck_gpg_trust_level[i].key, level)) {
 198                         *res = sigcheck_gpg_trust_level[i].value;
 199                         return 0;
 200                 }
 201         }
 202         return 1;
 203 }
 204
 205 static void parse_gpg_output(struct signature_check *sigc)
 206 {
 207         const char *buf = sigc->gpg_status;
 208         const char *line, *next;
 209         int i, j;
 210         int seen_exclusive_status = 0;
 211
 212         /* Iterate over all lines */
 213         for (line = buf; *line; line = strchrnul(line+1, '\n')) {
 214                 while (*line == '\n')
 215                         line++;
 216                 if (!*line)
 217                         break;
 218
 219                 /* Skip lines that don't start with GNUPG status */
 220                 if (!skip_prefix(line, "[GNUPG:] ", &line))
 221                         continue;
 222
 223                 /* Iterate over all search strings */
 224                 for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
 225                         if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
 226                                 /*
 227                                  * GOODSIG, BADSIG etc. can occur only once for
 228                                  * each signature.  Therefore, if we had more
 229                                  * than one then we're dealing with multiple
 230                                  * signatures.  We don't support them
 231                                  * currently, and they're rather hard to
 232                                  * create, so something is likely fishy and we
 233                                  * should reject them altogether.
 234                                  */
 235                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
 236                                         if (seen_exclusive_status++)
 237                                                 goto error;
 238                                 }
 239
 240                                 if (sigcheck_gpg_status[i].result)
 241                                         sigc->result = sigcheck_gpg_status[i].result;
 242                                 /* Do we have key information? */
 243                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_KEYID) {
 244                                         next = strchrnul(line, ' ');
 245                                         replace_cstring(&sigc->key, line, next);
 246                                         /* Do we have signer information? */
 247                                         if (*next && (sigcheck_gpg_status[i].flags & GPG_STATUS_UID)) {
 248                                                 line = next + 1;
 249                                                 next = strchrnul(line, '\n');
 250                                                 replace_cstring(&sigc->signer, line, next);
 251                                         }
 252                                 }
 253
 254                                 /* Do we have trust level? */
 255                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_TRUST_LEVEL) {
 256                                         /*
 257                                          * GPG v1 and v2 differs in how the
 258                                          * TRUST_ lines are written.  Some
 259                                          * trust lines contain no additional
 260                                          * space-separated information for v1.
 261                                          */
 262                                         size_t trust_size = strcspn(line, " \n");
 263                                         char *trust = xmemdupz(line, trust_size);
 264
 265                                         if (parse_gpg_trust_level(trust, &sigc->trust_level)) {
 266                                                 free(trust);
 267                                                 goto error;
 268                                         }
 269                                         free(trust);
 270                                 }
 271
 272                                 /* Do we have fingerprint? */
 273                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
 274                                         const char *limit;
 275                                         char **field;
 276
 277                                         next = strchrnul(line, ' ');
 278                                         replace_cstring(&sigc->fingerprint, line, next);
 279
 280                                         /*
 281                                          * Skip interim fields.  The search is
 282                                          * limited to the same line since only
 283                                          * OpenPGP signatures has a field with
 284                                          * the primary fingerprint.
 285                                          */
 286                                         limit = strchrnul(line, '\n');
 287                                         for (j = 9; j > 0; j--) {
 288                                                 if (!*next || limit <= next)
 289                                                         break;
 290                                                 line = next + 1;
 291                                                 next = strchrnul(line, ' ');
 292                                         }
 293
 294                                         field = &sigc->primary_key_fingerprint;
 295                                         if (!j) {
 296                                                 next = strchrnul(line, '\n');
 297                                                 replace_cstring(field, line, next);
 298                                         } else {
 299                                                 replace_cstring(field, NULL, NULL);
 300                                         }
 301                                 }
 302
 303                                 break;
 304                         }
 305                 }
 306         }
 307         return;
 308
 309 error:
 310         sigc->result = 'E';
 311         /* Clear partial data to avoid confusion */
 312         FREE_AND_NULL(sigc->primary_key_fingerprint);
 313         FREE_AND_NULL(sigc->fingerprint);
 314         FREE_AND_NULL(sigc->signer);
 315         FREE_AND_NULL(sigc->key);
 316 }
 317
 318 static int verify_gpg_signed_buffer(struct signature_check *sigc,
 319                                     struct gpg_format *fmt,
 320                                     const char *signature,
 321                                     size_t signature_size)
 322 {
 323         struct child_process gpg = CHILD_PROCESS_INIT;
 324         struct tempfile *temp;
 325         int ret;
 326         struct strbuf gpg_stdout = STRBUF_INIT;
 327         struct strbuf gpg_stderr = STRBUF_INIT;
 328
 329         temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 330         if (!temp)
 331                 return error_errno(_("could not create temporary file"));
 332         if (write_in_full(temp->fd, signature, signature_size) < 0 ||
 333             close_tempfile_gently(temp) < 0) {
 334                 error_errno(_("failed writing detached signature to '%s'"),
 335                             temp->filename.buf);
 336                 delete_tempfile(&temp);
 337                 return -1;
 338         }
 339
 340         strvec_push(&gpg.args, fmt->program);
 341         strvec_pushv(&gpg.args, fmt->verify_args);
 342         strvec_pushl(&gpg.args,
 343                      "--status-fd=1",
 344                      "--verify", temp->filename.buf, "-",
 345                      NULL);
 346
 347         sigchain_push(SIGPIPE, SIG_IGN);
 348         ret = pipe_command(&gpg, sigc->payload, sigc->payload_len, &gpg_stdout, 0,
 349                            &gpg_stderr, 0);
 350         sigchain_pop(SIGPIPE);
 351
 352         delete_tempfile(&temp);
 353
 354         ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
 355         sigc->output = strbuf_detach(&gpg_stderr, NULL);
 356         sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
 357
 358         parse_gpg_output(sigc);
 359
 360         strbuf_release(&gpg_stdout);
 361         strbuf_release(&gpg_stderr);
 362
 363         return ret;
 364 }
 365
 366 static void parse_ssh_output(struct signature_check *sigc)
 367 {
 368         const char *line, *principal, *search;
 369         char *to_free;
 370         char *key = NULL;
 371
 372         /*
 373          * ssh-keygen output should be:
 374          * Good "git" signature for PRINCIPAL with RSA key SHA256:FINGERPRINT
 375          *
 376          * or for valid but unknown keys:
 377          * Good "git" signature with RSA key SHA256:FINGERPRINT
 378          *
 379          * Note that "PRINCIPAL" can contain whitespace, "RSA" and
 380          * "SHA256" part could be a different token that names of
 381          * the algorithms used, and "FINGERPRINT" is a hexadecimal
 382          * string.  By finding the last occurence of " with ", we can
 383          * reliably parse out the PRINCIPAL.
 384          */
 385         sigc->result = 'B';
 386         sigc->trust_level = TRUST_NEVER;
 387
 388         line = to_free = xmemdupz(sigc->output, strcspn(sigc->output, "\n"));
 389
 390         if (skip_prefix(line, "Good \"git\" signature for ", &line)) {
 391                 /* Search for the last "with" to get the full principal */
 392                 principal = line;
 393                 do {
 394                         search = strstr(line, " with ");
 395                         if (search)
 396                                 line = search + 1;
 397                 } while (search != NULL);
 398                 if (line == principal)
 399                         goto cleanup;
 400
 401                 /* Valid signature and known principal */
 402                 sigc->result = 'G';
 403                 sigc->trust_level = TRUST_FULLY;
 404                 sigc->signer = xmemdupz(principal, line - principal - 1);
 405         } else if (skip_prefix(line, "Good \"git\" signature with ", &line)) {
 406                 /* Valid signature, but key unknown */
 407                 sigc->result = 'G';
 408                 sigc->trust_level = TRUST_UNDEFINED;
 409         } else {
 410                 goto cleanup;
 411         }
 412
 413         key = strstr(line, "key ");
 414         if (key) {
 415                 sigc->fingerprint = xstrdup(strstr(line, "key ") + 4);
 416                 sigc->key = xstrdup(sigc->fingerprint);
 417         } else {
 418                 /*
 419                  * Output did not match what we expected
 420                  * Treat the signature as bad
 421                  */
 422                 sigc->result = 'B';
 423         }
 424
 425 cleanup:
 426         free(to_free);
 427 }
 428
 429 static int verify_ssh_signed_buffer(struct signature_check *sigc,
 430                                     struct gpg_format *fmt,
 431                                     const char *signature,
 432                                     size_t signature_size)
 433 {
 434         struct child_process ssh_keygen = CHILD_PROCESS_INIT;
 435         struct tempfile *buffer_file;
 436         int ret = -1;
 437         const char *line;
 438         char *principal;
 439         struct strbuf ssh_principals_out = STRBUF_INIT;
 440         struct strbuf ssh_principals_err = STRBUF_INIT;
 441         struct strbuf ssh_keygen_out = STRBUF_INIT;
 442         struct strbuf ssh_keygen_err = STRBUF_INIT;
 443         struct strbuf verify_time = STRBUF_INIT;
 444         const struct date_mode verify_date_mode = {
 445                 .type = DATE_STRFTIME,
 446                 .strftime_fmt = "%Y%m%d%H%M%S",
 447                 /* SSH signing key validity has no timezone information - Use the local timezone */
 448                 .local = 1,
 449         };
 450
 451         if (!ssh_allowed_signers) {
 452                 error(_("gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification"));
 453                 return -1;
 454         }
 455
 456         buffer_file = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 457         if (!buffer_file)
 458                 return error_errno(_("could not create temporary file"));
 459         if (write_in_full(buffer_file->fd, signature, signature_size) < 0 ||
 460             close_tempfile_gently(buffer_file) < 0) {
 461                 error_errno(_("failed writing detached signature to '%s'"),
 462                             buffer_file->filename.buf);
 463                 delete_tempfile(&buffer_file);
 464                 return -1;
 465         }
 466
 467         if (sigc->payload_timestamp)
 468                 strbuf_addf(&verify_time, "-Overify-time=%s",
 469                         show_date(sigc->payload_timestamp, 0, &verify_date_mode));
 470
 471         /* Find the principal from the signers */
 472         strvec_pushl(&ssh_keygen.args, fmt->program,
 473                      "-Y", "find-principals",
 474                      "-f", ssh_allowed_signers,
 475                      "-s", buffer_file->filename.buf,
 476                      verify_time.buf,
 477                      NULL);
 478         ret = pipe_command(&ssh_keygen, NULL, 0, &ssh_principals_out, 0,
 479                            &ssh_principals_err, 0);
 480         if (ret && strstr(ssh_principals_err.buf, "usage:")) {
 481                 error(_("ssh-keygen -Y find-principals/verify is needed for ssh signature verification (available in openssh version 8.2p1+)"));
 482                 goto out;
 483         }
 484         if (ret || !ssh_principals_out.len) {
 485                 /*
 486                  * We did not find a matching principal in the allowedSigners
 487                  * Check without validation
 488                  */
 489                 child_process_init(&ssh_keygen);
 490                 strvec_pushl(&ssh_keygen.args, fmt->program,
 491                              "-Y", "check-novalidate",
 492                              "-n", "git",
 493                              "-s", buffer_file->filename.buf,
 494                              verify_time.buf,
 495                              NULL);
 496                 pipe_command(&ssh_keygen, sigc->payload, sigc->payload_len,
 497                                    &ssh_keygen_out, 0, &ssh_keygen_err, 0);
 498
 499                 /*
 500                  * Fail on unknown keys
 501                  * we still call check-novalidate to display the signature info
 502                  */
 503                 ret = -1;
 504         } else {
 505                 /* Check every principal we found (one per line) */
 506                 const char *next;
 507                 for (line = ssh_principals_out.buf;
 508                      *line;
 509                      line = next) {
 510                         const char *end_of_text;
 511
 512                         next = end_of_text = strchrnul(line, '\n');
 513
 514                          /* Did we find a LF, and did we have CR before it? */
 515                         if (*end_of_text &&
 516                             line < end_of_text &&
 517                             end_of_text[-1] == '\r')
 518                                 end_of_text--;
 519
 520                         /* Unless we hit NUL, skip over the LF we found */
 521                         if (*next)
 522                                 next++;
 523
 524                         /* Not all lines are data.  Skip empty ones */
 525                         if (line == end_of_text)
 526                                 continue;
 527
 528                         /* We now know we have an non-empty line. Process it */
 529                         principal = xmemdupz(line, end_of_text - line);
 530
 531                         child_process_init(&ssh_keygen);
 532                         strbuf_release(&ssh_keygen_out);
 533                         strbuf_release(&ssh_keygen_err);
 534                         strvec_push(&ssh_keygen.args, fmt->program);
 535                         /*
 536                          * We found principals
 537                          * Try with each until we find a match
 538                          */
 539                         strvec_pushl(&ssh_keygen.args, "-Y", "verify",
 540                                      "-n", "git",
 541                                      "-f", ssh_allowed_signers,
 542                                      "-I", principal,
 543                                      "-s", buffer_file->filename.buf,
 544                                      verify_time.buf,
 545                                      NULL);
 546
 547                         if (ssh_revocation_file) {
 548                                 if (file_exists(ssh_revocation_file)) {
 549                                         strvec_pushl(&ssh_keygen.args, "-r",
 550                                                      ssh_revocation_file, NULL);
 551                                 } else {
 552                                         warning(_("ssh signing revocation file configured but not found: %s"),
 553                                                 ssh_revocation_file);
 554                                 }
 555                         }
 556
 557                         sigchain_push(SIGPIPE, SIG_IGN);
 558                         ret = pipe_command(&ssh_keygen, sigc->payload, sigc->payload_len,
 559                                            &ssh_keygen_out, 0, &ssh_keygen_err, 0);
 560                         sigchain_pop(SIGPIPE);
 561
 562                         FREE_AND_NULL(principal);
 563
 564                         if (!ret)
 565                                 ret = !starts_with(ssh_keygen_out.buf, "Good");
 566
 567                         if (!ret)
 568                                 break;
 569                 }
 570         }
 571
 572         strbuf_stripspace(&ssh_keygen_out, 0);
 573         strbuf_stripspace(&ssh_keygen_err, 0);
 574         /* Add stderr outputs to show the user actual ssh-keygen errors */
 575         strbuf_add(&ssh_keygen_out, ssh_principals_err.buf, ssh_principals_err.len);
 576         strbuf_add(&ssh_keygen_out, ssh_keygen_err.buf, ssh_keygen_err.len);
 577         sigc->output = strbuf_detach(&ssh_keygen_out, NULL);
 578         sigc->gpg_status = xstrdup(sigc->output);
 579
 580         parse_ssh_output(sigc);
 581
 582 out:
 583         if (buffer_file)
 584                 delete_tempfile(&buffer_file);
 585         strbuf_release(&ssh_principals_out);
 586         strbuf_release(&ssh_principals_err);
 587         strbuf_release(&ssh_keygen_out);
 588         strbuf_release(&ssh_keygen_err);
 589         strbuf_release(&verify_time);
 590
 591         return ret;
 592 }
 593
 594 static int parse_payload_metadata(struct signature_check *sigc)
 595 {
 596         const char *ident_line = NULL;
 597         size_t ident_len;
 598         struct ident_split ident;
 599         const char *signer_header;
 600
 601         switch (sigc->payload_type) {
 602         case SIGNATURE_PAYLOAD_COMMIT:
 603                 signer_header = "committer";
 604                 break;
 605         case SIGNATURE_PAYLOAD_TAG:
 606                 signer_header = "tagger";
 607                 break;
 608         case SIGNATURE_PAYLOAD_UNDEFINED:
 609         case SIGNATURE_PAYLOAD_PUSH_CERT:
 610                 /* Ignore payloads we don't want to parse */
 611                 return 0;
 612         default:
 613                 BUG("invalid value for sigc->payload_type");
 614         }
 615
 616         ident_line = find_commit_header(sigc->payload, signer_header, &ident_len);
 617         if (!ident_line || !ident_len)
 618                 return 1;
 619
 620         if (split_ident_line(&ident, ident_line, ident_len))
 621                 return 1;
 622
 623         if (!sigc->payload_timestamp && ident.date_begin && ident.date_end)
 624                 sigc->payload_timestamp = parse_timestamp(ident.date_begin, NULL, 10);
 625
 626         return 0;
 627 }
 628
 629 int check_signature(struct signature_check *sigc,
 630                     const char *signature, size_t slen)
 631 {
 632         struct gpg_format *fmt;
 633         int status;
 634
 635         sigc->result = 'N';
 636         sigc->trust_level = -1;
 637
 638         fmt = get_format_by_sig(signature);
 639         if (!fmt)
 640                 die(_("bad/incompatible signature '%s'"), signature);
 641
 642         if (parse_payload_metadata(sigc))
 643                 return 1;
 644
 645         status = fmt->verify_signed_buffer(sigc, fmt, signature, slen);
 646
 647         if (status && !sigc->output)
 648                 return !!status;
 649
 650         status |= sigc->result != 'G';
 651         status |= sigc->trust_level < configured_min_trust_level;
 652
 653         return !!status;
 654 }
 655
 656 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 657 {
 658         const char *output = flags & GPG_VERIFY_RAW ? sigc->gpg_status :
 659                                                             sigc->output;
 660
 661         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 662                 fwrite(sigc->payload, 1, sigc->payload_len, stdout);
 663
 664         if (output)
 665                 fputs(output, stderr);
 666 }
 667
 668 size_t parse_signed_buffer(const char *buf, size_t size)
 669 {
 670         size_t len = 0;
 671         size_t match = size;
 672         while (len < size) {
 673                 const char *eol;
 674
 675                 if (get_format_by_sig(buf + len))
 676                         match = len;
 677
 678                 eol = memchr(buf + len, '\n', size - len);
 679                 len += eol ? eol - (buf + len) + 1 : size - len;
 680         }
 681         return match;
 682 }
 683
 684 int parse_signature(const char *buf, size_t size, struct strbuf *payload, struct strbuf *signature)
 685 {
 686         size_t match = parse_signed_buffer(buf, size);
 687         if (match != size) {
 688                 strbuf_add(payload, buf, match);
 689                 remove_signature(payload);
 690                 strbuf_add(signature, buf + match, size - match);
 691                 return 1;
 692         }
 693         return 0;
 694 }
 695
 696 void set_signing_key(const char *key)
 697 {
 698         free(configured_signing_key);
 699         configured_signing_key = xstrdup(key);
 700 }
 701
 702 int git_gpg_config(const char *var, const char *value, void *cb UNUSED)
 703 {
 704         struct gpg_format *fmt = NULL;
 705         char *fmtname = NULL;
 706         char *trust;
 707         int ret;
 708
 709         if (!strcmp(var, "user.signingkey")) {
 710                 if (!value)
 711                         return config_error_nonbool(var);
 712                 set_signing_key(value);
 713                 return 0;
 714         }
 715
 716         if (!strcmp(var, "gpg.format")) {
 717                 if (!value)
 718                         return config_error_nonbool(var);
 719                 fmt = get_format_by_name(value);
 720                 if (!fmt)
 721                         return error(_("invalid value for '%s': '%s'"),
 722                                      var, value);
 723                 use_format = fmt;
 724                 return 0;
 725         }
 726
 727         if (!strcmp(var, "gpg.mintrustlevel")) {
 728                 if (!value)
 729                         return config_error_nonbool(var);
 730
 731                 trust = xstrdup_toupper(value);
 732                 ret = parse_gpg_trust_level(trust, &configured_min_trust_level);
 733                 free(trust);
 734
 735                 if (ret)
 736                         return error(_("invalid value for '%s': '%s'"),
 737                                      var, value);
 738                 return 0;
 739         }
 740
 741         if (!strcmp(var, "gpg.ssh.defaultkeycommand")) {
 742                 if (!value)
 743                         return config_error_nonbool(var);
 744                 return git_config_string(&ssh_default_key_command, var, value);
 745         }
 746
 747         if (!strcmp(var, "gpg.ssh.allowedsignersfile")) {
 748                 if (!value)
 749                         return config_error_nonbool(var);
 750                 return git_config_pathname(&ssh_allowed_signers, var, value);
 751         }
 752
 753         if (!strcmp(var, "gpg.ssh.revocationfile")) {
 754                 if (!value)
 755                         return config_error_nonbool(var);
 756                 return git_config_pathname(&ssh_revocation_file, var, value);
 757         }
 758
 759         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 760                 fmtname = "openpgp";
 761
 762         if (!strcmp(var, "gpg.x509.program"))
 763                 fmtname = "x509";
 764
 765         if (!strcmp(var, "gpg.ssh.program"))
 766                 fmtname = "ssh";
 767
 768         if (fmtname) {
 769                 fmt = get_format_by_name(fmtname);
 770                 return git_config_string(&fmt->program, var, value);
 771         }
 772
 773         return 0;
 774 }
 775
 776 /*
 777  * Returns 1 if `string` contains a literal ssh key, 0 otherwise
 778  * `key` will be set to the start of the actual key if a prefix is present.
 779  */
 780 static int is_literal_ssh_key(const char *string, const char **key)
 781 {
 782         if (skip_prefix(string, "key::", key))
 783                 return 1;
 784         if (starts_with(string, "ssh-")) {
 785                 *key = string;
 786                 return 1;
 787         }
 788         return 0;
 789 }
 790
 791 static char *get_ssh_key_fingerprint(const char *signing_key)
 792 {
 793         struct child_process ssh_keygen = CHILD_PROCESS_INIT;
 794         int ret = -1;
 795         struct strbuf fingerprint_stdout = STRBUF_INIT;
 796         struct strbuf **fingerprint;
 797         char *fingerprint_ret;
 798         const char *literal_key = NULL;
 799
 800         /*
 801          * With SSH Signing this can contain a filename or a public key
 802          * For textual representation we usually want a fingerprint
 803          */
 804         if (is_literal_ssh_key(signing_key, &literal_key)) {
 805                 strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf", "-", NULL);
 806                 ret = pipe_command(&ssh_keygen, literal_key,
 807                                    strlen(literal_key), &fingerprint_stdout, 0,
 808                                    NULL, 0);
 809         } else {
 810                 strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf",
 811                              configured_signing_key, NULL);
 812                 ret = pipe_command(&ssh_keygen, NULL, 0, &fingerprint_stdout, 0,
 813                                    NULL, 0);
 814         }
 815
 816         if (!!ret)
 817                 die_errno(_("failed to get the ssh fingerprint for key '%s'"),
 818                           signing_key);
 819
 820         fingerprint = strbuf_split_max(&fingerprint_stdout, ' ', 3);
 821         if (!fingerprint[1])
 822                 die_errno(_("failed to get the ssh fingerprint for key '%s'"),
 823                           signing_key);
 824
 825         fingerprint_ret = strbuf_detach(fingerprint[1], NULL);
 826         strbuf_list_free(fingerprint);
 827         strbuf_release(&fingerprint_stdout);
 828         return fingerprint_ret;
 829 }
 830
 831 /* Returns the first public key from an ssh-agent to use for signing */
 832 static const char *get_default_ssh_signing_key(void)
 833 {
 834         struct child_process ssh_default_key = CHILD_PROCESS_INIT;
 835         int ret = -1;
 836         struct strbuf key_stdout = STRBUF_INIT, key_stderr = STRBUF_INIT;
 837         struct strbuf **keys;
 838         char *key_command = NULL;
 839         const char **argv;
 840         int n;
 841         char *default_key = NULL;
 842         const char *literal_key = NULL;
 843
 844         if (!ssh_default_key_command)
 845                 die(_("either user.signingkey or gpg.ssh.defaultKeyCommand needs to be configured"));
 846
 847         key_command = xstrdup(ssh_default_key_command);
 848         n = split_cmdline(key_command, &argv);
 849
 850         if (n < 0)
 851                 die("malformed build-time gpg.ssh.defaultKeyCommand: %s",
 852                     split_cmdline_strerror(n));
 853
 854         strvec_pushv(&ssh_default_key.args, argv);
 855         ret = pipe_command(&ssh_default_key, NULL, 0, &key_stdout, 0,
 856                            &key_stderr, 0);
 857
 858         if (!ret) {
 859                 keys = strbuf_split_max(&key_stdout, '\n', 2);
 860                 if (keys[0] && is_literal_ssh_key(keys[0]->buf, &literal_key)) {
 861                         /*
 862                          * We only use `is_literal_ssh_key` here to check validity
 863                          * The prefix will be stripped when the key is used.
 864                          */
 865                         default_key = strbuf_detach(keys[0], NULL);
 866                 } else {
 867                         warning(_("gpg.ssh.defaultKeyCommand succeeded but returned no keys: %s %s"),
 868                                 key_stderr.buf, key_stdout.buf);
 869                 }
 870
 871                 strbuf_list_free(keys);
 872         } else {
 873                 warning(_("gpg.ssh.defaultKeyCommand failed: %s %s"),
 874                         key_stderr.buf, key_stdout.buf);
 875         }
 876
 877         free(key_command);
 878         free(argv);
 879         strbuf_release(&key_stdout);
 880
 881         return default_key;
 882 }
 883
 884 static const char *get_ssh_key_id(void) {
 885         return get_ssh_key_fingerprint(get_signing_key());
 886 }
 887
 888 /* Returns a textual but unique representation of the signing key */
 889 const char *get_signing_key_id(void)
 890 {
 891         if (use_format->get_key_id) {
 892                 return use_format->get_key_id();
 893         }
 894
 895         /* GPG/GPGSM only store a key id on this variable */
 896         return get_signing_key();
 897 }
 898
 899 const char *get_signing_key(void)
 900 {
 901         if (configured_signing_key)
 902                 return configured_signing_key;
 903         if (use_format->get_default_key) {
 904                 return use_format->get_default_key();
 905         }
 906
 907         return git_committer_info(IDENT_STRICT | IDENT_NO_DATE);
 908 }
 909
 910 const char *gpg_trust_level_to_str(enum signature_trust_level level)
 911 {
 912         struct sigcheck_gpg_trust_level *trust;
 913
 914         if (level < 0 || level >= ARRAY_SIZE(sigcheck_gpg_trust_level))
 915                 BUG("invalid trust level requested %d", level);
 916
 917         trust = &sigcheck_gpg_trust_level[level];
 918         if (trust->value != level)
 919                 BUG("sigcheck_gpg_trust_level[] unsorted");
 920
 921         return sigcheck_gpg_trust_level[level].display_key;
 922 }
 923
 924 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 925 {
 926         return use_format->sign_buffer(buffer, signature, signing_key);
 927 }
 928
 929 /*
 930  * Strip CR from the line endings, in case we are on Windows.
 931  * NEEDSWORK: make it trim only CRs before LFs and rename
 932  */
 933 static void remove_cr_after(struct strbuf *buffer, size_t offset)
 934 {
 935         size_t i, j;
 936
 937         for (i = j = offset; i < buffer->len; i++) {
 938                 if (buffer->buf[i] != '\r') {
 939                         if (i != j)
 940                                 buffer->buf[j] = buffer->buf[i];
 941                         j++;
 942                 }
 943         }
 944         strbuf_setlen(buffer, j);
 945 }
 946
 947 static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
 948                           const char *signing_key)
 949 {
 950         struct child_process gpg = CHILD_PROCESS_INIT;
 951         int ret;
 952         size_t bottom;
 953         const char *cp;
 954         struct strbuf gpg_status = STRBUF_INIT;
 955
 956         strvec_pushl(&gpg.args,
 957                      use_format->program,
 958                      "--status-fd=2",
 959                      "-bsau", signing_key,
 960                      NULL);
 961
 962         bottom = signature->len;
 963
 964         /*
 965          * When the username signingkey is bad, program could be terminated
 966          * because gpg exits without reading and then write gets SIGPIPE.
 967          */
 968         sigchain_push(SIGPIPE, SIG_IGN);
 969         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 970                            signature, 1024, &gpg_status, 0);
 971         sigchain_pop(SIGPIPE);
 972
 973         for (cp = gpg_status.buf;
 974              cp && (cp = strstr(cp, "[GNUPG:] SIG_CREATED "));
 975              cp++) {
 976                 if (cp == gpg_status.buf || cp[-1] == '\n')
 977                         break; /* found */
 978         }
 979         ret |= !cp;
 980         strbuf_release(&gpg_status);
 981         if (ret)
 982                 return error(_("gpg failed to sign the data"));
 983
 984         /* Strip CR from the line endings, in case we are on Windows. */
 985         remove_cr_after(signature, bottom);
 986
 987         return 0;
 988 }
 989
 990 static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
 991                            const char *signing_key)
 992 {
 993         struct child_process signer = CHILD_PROCESS_INIT;
 994         int ret = -1;
 995         size_t bottom, keylen;
 996         struct strbuf signer_stderr = STRBUF_INIT;
 997         struct tempfile *key_file = NULL, *buffer_file = NULL;
 998         char *ssh_signing_key_file = NULL;
 999         struct strbuf ssh_signature_filename = STRBUF_INIT;
1000         const char *literal_key = NULL;
1001
1002         if (!signing_key || signing_key[0] == '\0')
1003                 return error(
1004                         _("user.signingKey needs to be set for ssh signing"));
1005
1006         if (is_literal_ssh_key(signing_key, &literal_key)) {
1007                 /* A literal ssh key */
1008                 key_file = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
1009                 if (!key_file)
1010                         return error_errno(
1011                                 _("could not create temporary file"));
1012                 keylen = strlen(literal_key);
1013                 if (write_in_full(key_file->fd, literal_key, keylen) < 0 ||
1014                     close_tempfile_gently(key_file) < 0) {
1015                         error_errno(_("failed writing ssh signing key to '%s'"),
1016                                     key_file->filename.buf);
1017                         goto out;
1018                 }
1019                 ssh_signing_key_file = strbuf_detach(&key_file->filename, NULL);
1020         } else {
1021                 /* We assume a file */
1022                 ssh_signing_key_file = expand_user_path(signing_key, 1);
1023         }
1024
1025         buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
1026         if (!buffer_file) {
1027                 error_errno(_("could not create temporary file"));
1028                 goto out;
1029         }
1030
1031         if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
1032             close_tempfile_gently(buffer_file) < 0) {
1033                 error_errno(_("failed writing ssh signing key buffer to '%s'"),
1034                             buffer_file->filename.buf);
1035                 goto out;
1036         }
1037
1038         strvec_pushl(&signer.args, use_format->program,
1039                      "-Y", "sign",
1040                      "-n", "git",
1041                      "-f", ssh_signing_key_file,
1042                      buffer_file->filename.buf,
1043                      NULL);
1044
1045         sigchain_push(SIGPIPE, SIG_IGN);
1046         ret = pipe_command(&signer, NULL, 0, NULL, 0, &signer_stderr, 0);
1047         sigchain_pop(SIGPIPE);
1048
1049         if (ret) {
1050                 if (strstr(signer_stderr.buf, "usage:"))
1051                         error(_("ssh-keygen -Y sign is needed for ssh signing (available in openssh version 8.2p1+)"));
1052
1053                 error("%s", signer_stderr.buf);
1054                 goto out;
1055         }
1056
1057         bottom = signature->len;
1058
1059         strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
1060         strbuf_addstr(&ssh_signature_filename, ".sig");
1061         if (strbuf_read_file(signature, ssh_signature_filename.buf, 0) < 0) {
1062                 ret = error_errno(
1063                         _("failed reading ssh signing data buffer from '%s'"),
1064                         ssh_signature_filename.buf);
1065                 goto out;
1066         }
1067         /* Strip CR from the line endings, in case we are on Windows. */
1068         remove_cr_after(signature, bottom);
1069
1070 out:
1071         if (key_file)
1072                 delete_tempfile(&key_file);
1073         if (buffer_file)
1074                 delete_tempfile(&buffer_file);
1075         if (ssh_signature_filename.len)
1076                 unlink_or_warn(ssh_signature_filename.buf);
1077         strbuf_release(&signer_stderr);
1078         strbuf_release(&ssh_signature_filename);
1079         FREE_AND_NULL(ssh_signing_key_file);
1080         return ret;
1081 }