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, const char *payload,
  23                                     size_t payload_size, 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, const char *payload,
  57                                     size_t payload_size, const char *signature,
  58                                     size_t signature_size);
  59 static int verify_ssh_signed_buffer(struct signature_check *sigc,
  60                                     struct gpg_format *fmt, const char *payload,
  61                                     size_t payload_size, 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, const char *payload,
 318                                     size_t payload_size, 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, payload, payload_size, &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->payload = xmemdupz(payload, payload_size);
 354         sigc->output = strbuf_detach(&gpg_stderr, NULL);
 355         sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
 356
 357         parse_gpg_output(sigc);
 358
 359         strbuf_release(&gpg_stdout);
 360         strbuf_release(&gpg_stderr);
 361
 362         return ret;
 363 }
 364
 365 static void parse_ssh_output(struct signature_check *sigc)
 366 {
 367         const char *line, *principal, *search;
 368         char *to_free;
 369         char *key = NULL;
 370
 371         /*
 372          * ssh-keygen output should be:
 373          * Good "git" signature for PRINCIPAL with RSA key SHA256:FINGERPRINT
 374          *
 375          * or for valid but unknown keys:
 376          * Good "git" signature with RSA key SHA256:FINGERPRINT
 377          *
 378          * Note that "PRINCIPAL" can contain whitespace, "RSA" and
 379          * "SHA256" part could be a different token that names of
 380          * the algorithms used, and "FINGERPRINT" is a hexadecimal
 381          * string.  By finding the last occurence of " with ", we can
 382          * reliably parse out the PRINCIPAL.
 383          */
 384         sigc->result = 'B';
 385         sigc->trust_level = TRUST_NEVER;
 386
 387         line = to_free = xmemdupz(sigc->output, strcspn(sigc->output, "\n"));
 388
 389         if (skip_prefix(line, "Good \"git\" signature for ", &line)) {
 390                 /* Valid signature and known principal */
 391                 sigc->result = 'G';
 392                 sigc->trust_level = TRUST_FULLY;
 393
 394                 /* Search for the last "with" to get the full principal */
 395                 principal = line;
 396                 do {
 397                         search = strstr(line, " with ");
 398                         if (search)
 399                                 line = search + 1;
 400                 } while (search != NULL);
 401                 sigc->signer = xmemdupz(principal, line - principal - 1);
 402         } else if (skip_prefix(line, "Good \"git\" signature with ", &line)) {
 403                 /* Valid signature, but key unknown */
 404                 sigc->result = 'G';
 405                 sigc->trust_level = TRUST_UNDEFINED;
 406         } else {
 407                 goto cleanup;
 408         }
 409
 410         key = strstr(line, "key");
 411         if (key) {
 412                 sigc->fingerprint = xstrdup(strstr(line, "key") + 4);
 413                 sigc->key = xstrdup(sigc->fingerprint);
 414         } else {
 415                 /*
 416                  * Output did not match what we expected
 417                  * Treat the signature as bad
 418                  */
 419                 sigc->result = 'B';
 420         }
 421
 422 cleanup:
 423         free(to_free);
 424 }
 425
 426 static int verify_ssh_signed_buffer(struct signature_check *sigc,
 427                                     struct gpg_format *fmt, const char *payload,
 428                                     size_t payload_size, const char *signature,
 429                                     size_t signature_size)
 430 {
 431         struct child_process ssh_keygen = CHILD_PROCESS_INIT;
 432         struct tempfile *buffer_file;
 433         int ret = -1;
 434         const char *line;
 435         size_t trust_size;
 436         char *principal;
 437         struct strbuf ssh_principals_out = STRBUF_INIT;
 438         struct strbuf ssh_principals_err = STRBUF_INIT;
 439         struct strbuf ssh_keygen_out = STRBUF_INIT;
 440         struct strbuf ssh_keygen_err = STRBUF_INIT;
 441
 442         if (!ssh_allowed_signers) {
 443                 error(_("gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification"));
 444                 return -1;
 445         }
 446
 447         buffer_file = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 448         if (!buffer_file)
 449                 return error_errno(_("could not create temporary file"));
 450         if (write_in_full(buffer_file->fd, signature, signature_size) < 0 ||
 451             close_tempfile_gently(buffer_file) < 0) {
 452                 error_errno(_("failed writing detached signature to '%s'"),
 453                             buffer_file->filename.buf);
 454                 delete_tempfile(&buffer_file);
 455                 return -1;
 456         }
 457
 458         /* Find the principal from the signers */
 459         strvec_pushl(&ssh_keygen.args, fmt->program,
 460                      "-Y", "find-principals",
 461                      "-f", ssh_allowed_signers,
 462                      "-s", buffer_file->filename.buf,
 463                      NULL);
 464         ret = pipe_command(&ssh_keygen, NULL, 0, &ssh_principals_out, 0,
 465                            &ssh_principals_err, 0);
 466         if (ret && strstr(ssh_principals_err.buf, "usage:")) {
 467                 error(_("ssh-keygen -Y find-principals/verify is needed for ssh signature verification (available in openssh version 8.2p1+)"));
 468                 goto out;
 469         }
 470         if (ret || !ssh_principals_out.len) {
 471                 /*
 472                  * We did not find a matching principal in the allowedSigners
 473                  * Check without validation
 474                  */
 475                 child_process_init(&ssh_keygen);
 476                 strvec_pushl(&ssh_keygen.args, fmt->program,
 477                              "-Y", "check-novalidate",
 478                              "-n", "git",
 479                              "-s", buffer_file->filename.buf,
 480                              NULL);
 481                 pipe_command(&ssh_keygen, payload, payload_size,
 482                                    &ssh_keygen_out, 0, &ssh_keygen_err, 0);
 483
 484                 /*
 485                  * Fail on unknown keys
 486                  * we still call check-novalidate to display the signature info
 487                  */
 488                 ret = -1;
 489         } else {
 490                 /* Check every principal we found (one per line) */
 491                 for (line = ssh_principals_out.buf; *line;
 492                      line = strchrnul(line + 1, '\n')) {
 493                         while (*line == '\n')
 494                                 line++;
 495                         if (!*line)
 496                                 break;
 497
 498                         trust_size = strcspn(line, "\n");
 499                         principal = xmemdupz(line, trust_size);
 500
 501                         child_process_init(&ssh_keygen);
 502                         strbuf_release(&ssh_keygen_out);
 503                         strbuf_release(&ssh_keygen_err);
 504                         strvec_push(&ssh_keygen.args, fmt->program);
 505                         /*
 506                          * We found principals
 507                          * Try with each until we find a match
 508                          */
 509                         strvec_pushl(&ssh_keygen.args, "-Y", "verify",
 510                                      "-n", "git",
 511                                      "-f", ssh_allowed_signers,
 512                                      "-I", principal,
 513                                      "-s", buffer_file->filename.buf,
 514                                      NULL);
 515
 516                         if (ssh_revocation_file) {
 517                                 if (file_exists(ssh_revocation_file)) {
 518                                         strvec_pushl(&ssh_keygen.args, "-r",
 519                                                      ssh_revocation_file, NULL);
 520                                 } else {
 521                                         warning(_("ssh signing revocation file configured but not found: %s"),
 522                                                 ssh_revocation_file);
 523                                 }
 524                         }
 525
 526                         sigchain_push(SIGPIPE, SIG_IGN);
 527                         ret = pipe_command(&ssh_keygen, payload, payload_size,
 528                                            &ssh_keygen_out, 0, &ssh_keygen_err, 0);
 529                         sigchain_pop(SIGPIPE);
 530
 531                         FREE_AND_NULL(principal);
 532
 533                         if (!ret)
 534                                 ret = !starts_with(ssh_keygen_out.buf, "Good");
 535
 536                         if (!ret)
 537                                 break;
 538                 }
 539         }
 540
 541         sigc->payload = xmemdupz(payload, payload_size);
 542         strbuf_stripspace(&ssh_keygen_out, 0);
 543         strbuf_stripspace(&ssh_keygen_err, 0);
 544         /* Add stderr outputs to show the user actual ssh-keygen errors */
 545         strbuf_add(&ssh_keygen_out, ssh_principals_err.buf, ssh_principals_err.len);
 546         strbuf_add(&ssh_keygen_out, ssh_keygen_err.buf, ssh_keygen_err.len);
 547         sigc->output = strbuf_detach(&ssh_keygen_out, NULL);
 548         sigc->gpg_status = xstrdup(sigc->output);
 549
 550         parse_ssh_output(sigc);
 551
 552 out:
 553         if (buffer_file)
 554                 delete_tempfile(&buffer_file);
 555         strbuf_release(&ssh_principals_out);
 556         strbuf_release(&ssh_principals_err);
 557         strbuf_release(&ssh_keygen_out);
 558         strbuf_release(&ssh_keygen_err);
 559
 560         return ret;
 561 }
 562
 563 int check_signature(const char *payload, size_t plen, const char *signature,
 564         size_t slen, struct signature_check *sigc)
 565 {
 566         struct gpg_format *fmt;
 567         int status;
 568
 569         sigc->result = 'N';
 570         sigc->trust_level = -1;
 571
 572         fmt = get_format_by_sig(signature);
 573         if (!fmt)
 574                 die(_("bad/incompatible signature '%s'"), signature);
 575
 576         status = fmt->verify_signed_buffer(sigc, fmt, payload, plen, signature,
 577                                            slen);
 578
 579         if (status && !sigc->output)
 580                 return !!status;
 581
 582         status |= sigc->result != 'G';
 583         status |= sigc->trust_level < configured_min_trust_level;
 584
 585         return !!status;
 586 }
 587
 588 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 589 {
 590         const char *output = flags & GPG_VERIFY_RAW ? sigc->gpg_status :
 591                                                             sigc->output;
 592
 593         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 594                 fputs(sigc->payload, stdout);
 595
 596         if (output)
 597                 fputs(output, stderr);
 598 }
 599
 600 size_t parse_signed_buffer(const char *buf, size_t size)
 601 {
 602         size_t len = 0;
 603         size_t match = size;
 604         while (len < size) {
 605                 const char *eol;
 606
 607                 if (get_format_by_sig(buf + len))
 608                         match = len;
 609
 610                 eol = memchr(buf + len, '\n', size - len);
 611                 len += eol ? eol - (buf + len) + 1 : size - len;
 612         }
 613         return match;
 614 }
 615
 616 int parse_signature(const char *buf, size_t size, struct strbuf *payload, struct strbuf *signature)
 617 {
 618         size_t match = parse_signed_buffer(buf, size);
 619         if (match != size) {
 620                 strbuf_add(payload, buf, match);
 621                 remove_signature(payload);
 622                 strbuf_add(signature, buf + match, size - match);
 623                 return 1;
 624         }
 625         return 0;
 626 }
 627
 628 void set_signing_key(const char *key)
 629 {
 630         free(configured_signing_key);
 631         configured_signing_key = xstrdup(key);
 632 }
 633
 634 int git_gpg_config(const char *var, const char *value, void *cb)
 635 {
 636         struct gpg_format *fmt = NULL;
 637         char *fmtname = NULL;
 638         char *trust;
 639         int ret;
 640
 641         if (!strcmp(var, "user.signingkey")) {
 642                 if (!value)
 643                         return config_error_nonbool(var);
 644                 set_signing_key(value);
 645                 return 0;
 646         }
 647
 648         if (!strcmp(var, "gpg.format")) {
 649                 if (!value)
 650                         return config_error_nonbool(var);
 651                 fmt = get_format_by_name(value);
 652                 if (!fmt)
 653                         return error("unsupported value for %s: %s",
 654                                      var, value);
 655                 use_format = fmt;
 656                 return 0;
 657         }
 658
 659         if (!strcmp(var, "gpg.mintrustlevel")) {
 660                 if (!value)
 661                         return config_error_nonbool(var);
 662
 663                 trust = xstrdup_toupper(value);
 664                 ret = parse_gpg_trust_level(trust, &configured_min_trust_level);
 665                 free(trust);
 666
 667                 if (ret)
 668                         return error("unsupported value for %s: %s", var,
 669                                      value);
 670                 return 0;
 671         }
 672
 673         if (!strcmp(var, "gpg.ssh.defaultkeycommand")) {
 674                 if (!value)
 675                         return config_error_nonbool(var);
 676                 return git_config_string(&ssh_default_key_command, var, value);
 677         }
 678
 679         if (!strcmp(var, "gpg.ssh.allowedsignersfile")) {
 680                 if (!value)
 681                         return config_error_nonbool(var);
 682                 return git_config_pathname(&ssh_allowed_signers, var, value);
 683         }
 684
 685         if (!strcmp(var, "gpg.ssh.revocationfile")) {
 686                 if (!value)
 687                         return config_error_nonbool(var);
 688                 return git_config_pathname(&ssh_revocation_file, var, value);
 689         }
 690
 691         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 692                 fmtname = "openpgp";
 693
 694         if (!strcmp(var, "gpg.x509.program"))
 695                 fmtname = "x509";
 696
 697         if (!strcmp(var, "gpg.ssh.program"))
 698                 fmtname = "ssh";
 699
 700         if (fmtname) {
 701                 fmt = get_format_by_name(fmtname);
 702                 return git_config_string(&fmt->program, var, value);
 703         }
 704
 705         return 0;
 706 }
 707
 708 static char *get_ssh_key_fingerprint(const char *signing_key)
 709 {
 710         struct child_process ssh_keygen = CHILD_PROCESS_INIT;
 711         int ret = -1;
 712         struct strbuf fingerprint_stdout = STRBUF_INIT;
 713         struct strbuf **fingerprint;
 714         char *fingerprint_ret;
 715
 716         /*
 717          * With SSH Signing this can contain a filename or a public key
 718          * For textual representation we usually want a fingerprint
 719          */
 720         if (starts_with(signing_key, "ssh-")) {
 721                 strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf", "-", NULL);
 722                 ret = pipe_command(&ssh_keygen, signing_key,
 723                                    strlen(signing_key), &fingerprint_stdout, 0,
 724                                    NULL, 0);
 725         } else {
 726                 strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf",
 727                              configured_signing_key, NULL);
 728                 ret = pipe_command(&ssh_keygen, NULL, 0, &fingerprint_stdout, 0,
 729                                    NULL, 0);
 730         }
 731
 732         if (!!ret)
 733                 die_errno(_("failed to get the ssh fingerprint for key '%s'"),
 734                           signing_key);
 735
 736         fingerprint = strbuf_split_max(&fingerprint_stdout, ' ', 3);
 737         if (!fingerprint[1])
 738                 die_errno(_("failed to get the ssh fingerprint for key '%s'"),
 739                           signing_key);
 740
 741         fingerprint_ret = strbuf_detach(fingerprint[1], NULL);
 742         strbuf_list_free(fingerprint);
 743         strbuf_release(&fingerprint_stdout);
 744         return fingerprint_ret;
 745 }
 746
 747 /* Returns the first public key from an ssh-agent to use for signing */
 748 static const char *get_default_ssh_signing_key(void)
 749 {
 750         struct child_process ssh_default_key = CHILD_PROCESS_INIT;
 751         int ret = -1;
 752         struct strbuf key_stdout = STRBUF_INIT, key_stderr = STRBUF_INIT;
 753         struct strbuf **keys;
 754         char *key_command = NULL;
 755         const char **argv;
 756         int n;
 757         char *default_key = NULL;
 758
 759         if (!ssh_default_key_command)
 760                 die(_("either user.signingkey or gpg.ssh.defaultKeyCommand needs to be configured"));
 761
 762         key_command = xstrdup(ssh_default_key_command);
 763         n = split_cmdline(key_command, &argv);
 764
 765         if (n < 0)
 766                 die("malformed build-time gpg.ssh.defaultKeyCommand: %s",
 767                     split_cmdline_strerror(n));
 768
 769         strvec_pushv(&ssh_default_key.args, argv);
 770         ret = pipe_command(&ssh_default_key, NULL, 0, &key_stdout, 0,
 771                            &key_stderr, 0);
 772
 773         if (!ret) {
 774                 keys = strbuf_split_max(&key_stdout, '\n', 2);
 775                 if (keys[0] && starts_with(keys[0]->buf, "ssh-")) {
 776                         default_key = strbuf_detach(keys[0], NULL);
 777                 } else {
 778                         warning(_("gpg.ssh.defaultKeycommand succeeded but returned no keys: %s %s"),
 779                                 key_stderr.buf, key_stdout.buf);
 780                 }
 781
 782                 strbuf_list_free(keys);
 783         } else {
 784                 warning(_("gpg.ssh.defaultKeyCommand failed: %s %s"),
 785                         key_stderr.buf, key_stdout.buf);
 786         }
 787
 788         free(key_command);
 789         free(argv);
 790         strbuf_release(&key_stdout);
 791
 792         return default_key;
 793 }
 794
 795 static const char *get_ssh_key_id(void) {
 796         return get_ssh_key_fingerprint(get_signing_key());
 797 }
 798
 799 /* Returns a textual but unique representation of the signing key */
 800 const char *get_signing_key_id(void)
 801 {
 802         if (use_format->get_key_id) {
 803                 return use_format->get_key_id();
 804         }
 805
 806         /* GPG/GPGSM only store a key id on this variable */
 807         return get_signing_key();
 808 }
 809
 810 const char *get_signing_key(void)
 811 {
 812         if (configured_signing_key)
 813                 return configured_signing_key;
 814         if (use_format->get_default_key) {
 815                 return use_format->get_default_key();
 816         }
 817
 818         return git_committer_info(IDENT_STRICT | IDENT_NO_DATE);
 819 }
 820
 821 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 822 {
 823         return use_format->sign_buffer(buffer, signature, signing_key);
 824 }
 825
 826 /*
 827  * Strip CR from the line endings, in case we are on Windows.
 828  * NEEDSWORK: make it trim only CRs before LFs and rename
 829  */
 830 static void remove_cr_after(struct strbuf *buffer, size_t offset)
 831 {
 832         size_t i, j;
 833
 834         for (i = j = offset; i < buffer->len; i++) {
 835                 if (buffer->buf[i] != '\r') {
 836                         if (i != j)
 837                                 buffer->buf[j] = buffer->buf[i];
 838                         j++;
 839                 }
 840         }
 841         strbuf_setlen(buffer, j);
 842 }
 843
 844 static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
 845                           const char *signing_key)
 846 {
 847         struct child_process gpg = CHILD_PROCESS_INIT;
 848         int ret;
 849         size_t bottom;
 850         struct strbuf gpg_status = STRBUF_INIT;
 851
 852         strvec_pushl(&gpg.args,
 853                      use_format->program,
 854                      "--status-fd=2",
 855                      "-bsau", signing_key,
 856                      NULL);
 857
 858         bottom = signature->len;
 859
 860         /*
 861          * When the username signingkey is bad, program could be terminated
 862          * because gpg exits without reading and then write gets SIGPIPE.
 863          */
 864         sigchain_push(SIGPIPE, SIG_IGN);
 865         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 866                            signature, 1024, &gpg_status, 0);
 867         sigchain_pop(SIGPIPE);
 868
 869         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 870         strbuf_release(&gpg_status);
 871         if (ret)
 872                 return error(_("gpg failed to sign the data"));
 873
 874         /* Strip CR from the line endings, in case we are on Windows. */
 875         remove_cr_after(signature, bottom);
 876
 877         return 0;
 878 }
 879
 880 static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
 881                            const char *signing_key)
 882 {
 883         struct child_process signer = CHILD_PROCESS_INIT;
 884         int ret = -1;
 885         size_t bottom, keylen;
 886         struct strbuf signer_stderr = STRBUF_INIT;
 887         struct tempfile *key_file = NULL, *buffer_file = NULL;
 888         char *ssh_signing_key_file = NULL;
 889         struct strbuf ssh_signature_filename = STRBUF_INIT;
 890
 891         if (!signing_key || signing_key[0] == '\0')
 892                 return error(
 893                         _("user.signingkey needs to be set for ssh signing"));
 894
 895         if (starts_with(signing_key, "ssh-")) {
 896                 /* A literal ssh key */
 897                 key_file = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
 898                 if (!key_file)
 899                         return error_errno(
 900                                 _("could not create temporary file"));
 901                 keylen = strlen(signing_key);
 902                 if (write_in_full(key_file->fd, signing_key, keylen) < 0 ||
 903                     close_tempfile_gently(key_file) < 0) {
 904                         error_errno(_("failed writing ssh signing key to '%s'"),
 905                                     key_file->filename.buf);
 906                         goto out;
 907                 }
 908                 ssh_signing_key_file = strbuf_detach(&key_file->filename, NULL);
 909         } else {
 910                 /* We assume a file */
 911                 ssh_signing_key_file = expand_user_path(signing_key, 1);
 912         }
 913
 914         buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
 915         if (!buffer_file) {
 916                 error_errno(_("could not create temporary file"));
 917                 goto out;
 918         }
 919
 920         if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
 921             close_tempfile_gently(buffer_file) < 0) {
 922                 error_errno(_("failed writing ssh signing key buffer to '%s'"),
 923                             buffer_file->filename.buf);
 924                 goto out;
 925         }
 926
 927         strvec_pushl(&signer.args, use_format->program,
 928                      "-Y", "sign",
 929                      "-n", "git",
 930                      "-f", ssh_signing_key_file,
 931                      buffer_file->filename.buf,
 932                      NULL);
 933
 934         sigchain_push(SIGPIPE, SIG_IGN);
 935         ret = pipe_command(&signer, NULL, 0, NULL, 0, &signer_stderr, 0);
 936         sigchain_pop(SIGPIPE);
 937
 938         if (ret) {
 939                 if (strstr(signer_stderr.buf, "usage:"))
 940                         error(_("ssh-keygen -Y sign is needed for ssh signing (available in openssh version 8.2p1+)"));
 941
 942                 error("%s", signer_stderr.buf);
 943                 goto out;
 944         }
 945
 946         bottom = signature->len;
 947
 948         strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
 949         strbuf_addstr(&ssh_signature_filename, ".sig");
 950         if (strbuf_read_file(signature, ssh_signature_filename.buf, 0) < 0) {
 951                 error_errno(
 952                         _("failed reading ssh signing data buffer from '%s'"),
 953                         ssh_signature_filename.buf);
 954         }
 955         unlink_or_warn(ssh_signature_filename.buf);
 956
 957         /* Strip CR from the line endings, in case we are on Windows. */
 958         remove_cr_after(signature, bottom);
 959
 960 out:
 961         if (key_file)
 962                 delete_tempfile(&key_file);
 963         if (buffer_file)
 964                 delete_tempfile(&buffer_file);
 965         strbuf_release(&signer_stderr);
 966         strbuf_release(&ssh_signature_filename);
 967         FREE_AND_NULL(ssh_signing_key_file);
 968         return ret;
 969 }