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