gpg-interface.c

   1 #define USE_THE_REPOSITORY_VARIABLE
   2
   3 #include "git-compat-util.h"
   4 #include "commit.h"
   5 #include "config.h"
   6 #include "date.h"
   7 #include "gettext.h"
   8 #include "run-command.h"
   9 #include "strbuf.h"
  10 #include "dir.h"
  11 #include "ident.h"
  12 #include "gpg-interface.h"
  13 #include "path.h"
  14 #include "sigchain.h"
  15 #include "tempfile.h"
  16 #include "alias.h"
  17
  18 static int git_gpg_config(const char *, const char *,
  19                           const struct config_context *, void *);
  20
  21 static void gpg_interface_lazy_init(void)
  22 {
  23         static int done;
  24
  25         if (done)
  26                 return;
  27         done = 1;
  28         git_config(git_gpg_config, NULL);
  29 }
  30
  31 static char *configured_signing_key;
  32 static char *ssh_default_key_command;
  33 static char *ssh_allowed_signers;
  34 static char *ssh_revocation_file;
  35 static enum signature_trust_level configured_min_trust_level = TRUST_UNDEFINED;
  36
  37 struct gpg_format {
  38         const char *name;
  39         const char *program;
  40         const char **verify_args;
  41         const char **sigs;
  42         int (*verify_signed_buffer)(struct signature_check *sigc,
  43                                     struct gpg_format *fmt,
  44                                     const char *signature,
  45                                     size_t signature_size);
  46         int (*sign_buffer)(struct strbuf *buffer, struct strbuf *signature,
  47                            const char *signing_key);
  48         char *(*get_default_key)(void);
  49         char *(*get_key_id)(void);
  50 };
  51
  52 static const char *openpgp_verify_args[] = {
  53         "--keyid-format=long",
  54         NULL
  55 };
  56 static const char *openpgp_sigs[] = {
  57         "-----BEGIN PGP SIGNATURE-----",
  58         "-----BEGIN PGP MESSAGE-----",
  59         NULL
  60 };
  61
  62 static const char *x509_verify_args[] = {
  63         NULL
  64 };
  65 static const char *x509_sigs[] = {
  66         "-----BEGIN SIGNED MESSAGE-----",
  67         NULL
  68 };
  69
  70 static const char *ssh_verify_args[] = { NULL };
  71 static const char *ssh_sigs[] = {
  72         "-----BEGIN SSH SIGNATURE-----",
  73         NULL
  74 };
  75
  76 static int verify_gpg_signed_buffer(struct signature_check *sigc,
  77                                     struct gpg_format *fmt,
  78                                     const char *signature,
  79                                     size_t signature_size);
  80 static int verify_ssh_signed_buffer(struct signature_check *sigc,
  81                                     struct gpg_format *fmt,
  82                                     const char *signature,
  83                                     size_t signature_size);
  84 static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
  85                            const char *signing_key);
  86 static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
  87                            const char *signing_key);
  88
  89 static char *get_default_ssh_signing_key(void);
  90
  91 static char *get_ssh_key_id(void);
  92
  93 static struct gpg_format gpg_format[] = {
  94         {
  95                 .name = "openpgp",
  96                 .program = "gpg",
  97                 .verify_args = openpgp_verify_args,
  98                 .sigs = openpgp_sigs,
  99                 .verify_signed_buffer = verify_gpg_signed_buffer,
 100                 .sign_buffer = sign_buffer_gpg,
 101                 .get_default_key = NULL,
 102                 .get_key_id = NULL,
 103         },
 104         {
 105                 .name = "x509",
 106                 .program = "gpgsm",
 107                 .verify_args = x509_verify_args,
 108                 .sigs = x509_sigs,
 109                 .verify_signed_buffer = verify_gpg_signed_buffer,
 110                 .sign_buffer = sign_buffer_gpg,
 111                 .get_default_key = NULL,
 112                 .get_key_id = NULL,
 113         },
 114         {
 115                 .name = "ssh",
 116                 .program = "ssh-keygen",
 117                 .verify_args = ssh_verify_args,
 118                 .sigs = ssh_sigs,
 119                 .verify_signed_buffer = verify_ssh_signed_buffer,
 120                 .sign_buffer = sign_buffer_ssh,
 121                 .get_default_key = get_default_ssh_signing_key,
 122                 .get_key_id = get_ssh_key_id,
 123         },
 124 };
 125
 126 static struct gpg_format *use_format = &gpg_format[0];
 127
 128 static struct gpg_format *get_format_by_name(const char *str)
 129 {
 130         int i;
 131
 132         for (i = 0; i < ARRAY_SIZE(gpg_format); i++)
 133                 if (!strcmp(gpg_format[i].name, str))
 134                         return gpg_format + i;
 135         return NULL;
 136 }
 137
 138 static struct gpg_format *get_format_by_sig(const char *sig)
 139 {
 140         int i, j;
 141
 142         for (i = 0; i < ARRAY_SIZE(gpg_format); i++)
 143                 for (j = 0; gpg_format[i].sigs[j]; j++)
 144                         if (starts_with(sig, gpg_format[i].sigs[j]))
 145                                 return gpg_format + i;
 146         return NULL;
 147 }
 148
 149 void signature_check_clear(struct signature_check *sigc)
 150 {
 151         FREE_AND_NULL(sigc->payload);
 152         FREE_AND_NULL(sigc->output);
 153         FREE_AND_NULL(sigc->gpg_status);
 154         FREE_AND_NULL(sigc->signer);
 155         FREE_AND_NULL(sigc->key);
 156         FREE_AND_NULL(sigc->fingerprint);
 157         FREE_AND_NULL(sigc->primary_key_fingerprint);
 158 }
 159
 160 /* An exclusive status -- only one of them can appear in output */
 161 #define GPG_STATUS_EXCLUSIVE    (1<<0)
 162 /* The status includes key identifier */
 163 #define GPG_STATUS_KEYID        (1<<1)
 164 /* The status includes user identifier */
 165 #define GPG_STATUS_UID          (1<<2)
 166 /* The status includes key fingerprints */
 167 #define GPG_STATUS_FINGERPRINT  (1<<3)
 168 /* The status includes trust level */
 169 #define GPG_STATUS_TRUST_LEVEL  (1<<4)
 170
 171 /* Short-hand for standard exclusive *SIG status with keyid & UID */
 172 #define GPG_STATUS_STDSIG       (GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID|GPG_STATUS_UID)
 173
 174 static struct {
 175         char result;
 176         const char *check;
 177         unsigned int flags;
 178 } sigcheck_gpg_status[] = {
 179         { 'G', "GOODSIG ", GPG_STATUS_STDSIG },
 180         { 'B', "BADSIG ", GPG_STATUS_STDSIG },
 181         { 'E', "ERRSIG ", GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID },
 182         { 'X', "EXPSIG ", GPG_STATUS_STDSIG },
 183         { 'Y', "EXPKEYSIG ", GPG_STATUS_STDSIG },
 184         { 'R', "REVKEYSIG ", GPG_STATUS_STDSIG },
 185         { 0, "VALIDSIG ", GPG_STATUS_FINGERPRINT },
 186         { 0, "TRUST_", GPG_STATUS_TRUST_LEVEL },
 187 };
 188
 189 /* Keep the order same as enum signature_trust_level */
 190 static struct sigcheck_gpg_trust_level {
 191         const char *key;
 192         const char *display_key;
 193         enum signature_trust_level value;
 194 } sigcheck_gpg_trust_level[] = {
 195         { "UNDEFINED", "undefined", TRUST_UNDEFINED },
 196         { "NEVER", "never", TRUST_NEVER },
 197         { "MARGINAL", "marginal", TRUST_MARGINAL },
 198         { "FULLY", "fully", TRUST_FULLY },
 199         { "ULTIMATE", "ultimate", TRUST_ULTIMATE },
 200 };
 201
 202 static void replace_cstring(char **field, const char *line, const char *next)
 203 {
 204         free(*field);
 205
 206         if (line && next)
 207                 *field = xmemdupz(line, next - line);
 208         else
 209                 *field = NULL;
 210 }
 211
 212 static int parse_gpg_trust_level(const char *level,
 213                                  enum signature_trust_level *res)
 214 {
 215         size_t i;
 216
 217         for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_trust_level); i++) {
 218                 if (!strcmp(sigcheck_gpg_trust_level[i].key, level)) {
 219                         *res = sigcheck_gpg_trust_level[i].value;
 220                         return 0;
 221                 }
 222         }
 223         return 1;
 224 }
 225
 226 static void parse_gpg_output(struct signature_check *sigc)
 227 {
 228         const char *buf = sigc->gpg_status;
 229         const char *line, *next;
 230         int i, j;
 231         int seen_exclusive_status = 0;
 232
 233         /* Iterate over all lines */
 234         for (line = buf; *line; line = strchrnul(line+1, '\n')) {
 235                 while (*line == '\n')
 236                         line++;
 237                 if (!*line)
 238                         break;
 239
 240                 /* Skip lines that don't start with GNUPG status */
 241                 if (!skip_prefix(line, "[GNUPG:] ", &line))
 242                         continue;
 243
 244                 /* Iterate over all search strings */
 245                 for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
 246                         if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
 247                                 /*
 248                                  * GOODSIG, BADSIG etc. can occur only once for
 249                                  * each signature.  Therefore, if we had more
 250                                  * than one then we're dealing with multiple
 251                                  * signatures.  We don't support them
 252                                  * currently, and they're rather hard to
 253                                  * create, so something is likely fishy and we
 254                                  * should reject them altogether.
 255                                  */
 256                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
 257                                         if (seen_exclusive_status++)
 258                                                 goto error;
 259                                 }
 260
 261                                 if (sigcheck_gpg_status[i].result)
 262                                         sigc->result = sigcheck_gpg_status[i].result;
 263                                 /* Do we have key information? */
 264                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_KEYID) {
 265                                         next = strchrnul(line, ' ');
 266                                         replace_cstring(&sigc->key, line, next);
 267                                         /* Do we have signer information? */
 268                                         if (*next && (sigcheck_gpg_status[i].flags & GPG_STATUS_UID)) {
 269                                                 line = next + 1;
 270                                                 next = strchrnul(line, '\n');
 271                                                 replace_cstring(&sigc->signer, line, next);
 272                                         }
 273                                 }
 274
 275                                 /* Do we have trust level? */
 276                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_TRUST_LEVEL) {
 277                                         /*
 278                                          * GPG v1 and v2 differs in how the
 279                                          * TRUST_ lines are written.  Some
 280                                          * trust lines contain no additional
 281                                          * space-separated information for v1.
 282                                          */
 283                                         size_t trust_size = strcspn(line, " \n");
 284                                         char *trust = xmemdupz(line, trust_size);
 285
 286                                         if (parse_gpg_trust_level(trust, &sigc->trust_level)) {
 287                                                 free(trust);
 288                                                 goto error;
 289                                         }
 290                                         free(trust);
 291                                 }
 292
 293                                 /* Do we have fingerprint? */
 294                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
 295                                         const char *limit;
 296                                         char **field;
 297
 298                                         next = strchrnul(line, ' ');
 299                                         replace_cstring(&sigc->fingerprint, line, next);
 300
 301                                         /*
 302                                          * Skip interim fields.  The search is
 303                                          * limited to the same line since only
 304                                          * OpenPGP signatures has a field with
 305                                          * the primary fingerprint.
 306                                          */
 307                                         limit = strchrnul(line, '\n');
 308                                         for (j = 9; j > 0; j--) {
 309                                                 if (!*next || limit <= next)
 310                                                         break;
 311                                                 line = next + 1;
 312                                                 next = strchrnul(line, ' ');
 313                                         }
 314
 315                                         field = &sigc->primary_key_fingerprint;
 316                                         if (!j) {
 317                                                 next = strchrnul(line, '\n');
 318                                                 replace_cstring(field, line, next);
 319                                         } else {
 320                                                 replace_cstring(field, NULL, NULL);
 321                                         }
 322                                 }
 323
 324                                 break;
 325                         }
 326                 }
 327         }
 328         return;
 329
 330 error:
 331         sigc->result = 'E';
 332         /* Clear partial data to avoid confusion */
 333         FREE_AND_NULL(sigc->primary_key_fingerprint);
 334         FREE_AND_NULL(sigc->fingerprint);
 335         FREE_AND_NULL(sigc->signer);
 336         FREE_AND_NULL(sigc->key);
 337 }
 338
 339 static int verify_gpg_signed_buffer(struct signature_check *sigc,
 340                                     struct gpg_format *fmt,
 341                                     const char *signature,
 342                                     size_t signature_size)
 343 {
 344         struct child_process gpg = CHILD_PROCESS_INIT;
 345         struct tempfile *temp;
 346         int ret;
 347         struct strbuf gpg_stdout = STRBUF_INIT;
 348         struct strbuf gpg_stderr = STRBUF_INIT;
 349
 350         temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 351         if (!temp)
 352                 return error_errno(_("could not create temporary file"));
 353         if (write_in_full(temp->fd, signature, signature_size) < 0 ||
 354             close_tempfile_gently(temp) < 0) {
 355                 error_errno(_("failed writing detached signature to '%s'"),
 356                             temp->filename.buf);
 357                 delete_tempfile(&temp);
 358                 return -1;
 359         }
 360
 361         strvec_push(&gpg.args, fmt->program);
 362         strvec_pushv(&gpg.args, fmt->verify_args);
 363         strvec_pushl(&gpg.args,
 364                      "--status-fd=1",
 365                      "--verify", temp->filename.buf, "-",
 366                      NULL);
 367
 368         sigchain_push(SIGPIPE, SIG_IGN);
 369         ret = pipe_command(&gpg, sigc->payload, sigc->payload_len, &gpg_stdout, 0,
 370                            &gpg_stderr, 0);
 371         sigchain_pop(SIGPIPE);
 372
 373         delete_tempfile(&temp);
 374
 375         ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
 376         sigc->output = strbuf_detach(&gpg_stderr, NULL);
 377         sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
 378
 379         parse_gpg_output(sigc);
 380
 381         strbuf_release(&gpg_stdout);
 382         strbuf_release(&gpg_stderr);
 383
 384         return ret;
 385 }
 386
 387 static void parse_ssh_output(struct signature_check *sigc)
 388 {
 389         const char *line, *principal, *search;
 390         char *to_free;
 391         char *key = NULL;
 392
 393         /*
 394          * ssh-keygen output should be:
 395          * Good "git" signature for PRINCIPAL with RSA key SHA256:FINGERPRINT
 396          *
 397          * or for valid but unknown keys:
 398          * Good "git" signature with RSA key SHA256:FINGERPRINT
 399          *
 400          * Note that "PRINCIPAL" can contain whitespace, "RSA" and
 401          * "SHA256" part could be a different token that names of
 402          * the algorithms used, and "FINGERPRINT" is a hexadecimal
 403          * string.  By finding the last occurence of " with ", we can
 404          * reliably parse out the PRINCIPAL.
 405          */
 406         sigc->result = 'B';
 407         sigc->trust_level = TRUST_NEVER;
 408
 409         line = to_free = xmemdupz(sigc->output, strcspn(sigc->output, "\n"));
 410
 411         if (skip_prefix(line, "Good \"git\" signature for ", &line)) {
 412                 /* Search for the last "with" to get the full principal */
 413                 principal = line;
 414                 do {
 415                         search = strstr(line, " with ");
 416                         if (search)
 417                                 line = search + 1;
 418                 } while (search != NULL);
 419                 if (line == principal)
 420                         goto cleanup;
 421
 422                 /* Valid signature and known principal */
 423                 sigc->result = 'G';
 424                 sigc->trust_level = TRUST_FULLY;
 425                 sigc->signer = xmemdupz(principal, line - principal - 1);
 426         } else if (skip_prefix(line, "Good \"git\" signature with ", &line)) {
 427                 /* Valid signature, but key unknown */
 428                 sigc->result = 'G';
 429                 sigc->trust_level = TRUST_UNDEFINED;
 430         } else {
 431                 goto cleanup;
 432         }
 433
 434         key = strstr(line, "key ");
 435         if (key) {
 436                 sigc->fingerprint = xstrdup(strstr(line, "key ") + 4);
 437                 sigc->key = xstrdup(sigc->fingerprint);
 438         } else {
 439                 /*
 440                  * Output did not match what we expected
 441                  * Treat the signature as bad
 442                  */
 443                 sigc->result = 'B';
 444         }
 445
 446 cleanup:
 447         free(to_free);
 448 }
 449
 450 static int verify_ssh_signed_buffer(struct signature_check *sigc,
 451                                     struct gpg_format *fmt,
 452                                     const char *signature,
 453                                     size_t signature_size)
 454 {
 455         struct child_process ssh_keygen = CHILD_PROCESS_INIT;
 456         struct tempfile *buffer_file;
 457         int ret = -1;
 458         const char *line;
 459         char *principal;
 460         struct strbuf ssh_principals_out = STRBUF_INIT;
 461         struct strbuf ssh_principals_err = STRBUF_INIT;
 462         struct strbuf ssh_keygen_out = STRBUF_INIT;
 463         struct strbuf ssh_keygen_err = STRBUF_INIT;
 464         struct strbuf verify_time = STRBUF_INIT;
 465         const struct date_mode verify_date_mode = {
 466                 .type = DATE_STRFTIME,
 467                 .strftime_fmt = "%Y%m%d%H%M%S",
 468                 /* SSH signing key validity has no timezone information - Use the local timezone */
 469                 .local = 1,
 470         };
 471
 472         if (!ssh_allowed_signers) {
 473                 error(_("gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification"));
 474                 return -1;
 475         }
 476
 477         buffer_file = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 478         if (!buffer_file)
 479                 return error_errno(_("could not create temporary file"));
 480         if (write_in_full(buffer_file->fd, signature, signature_size) < 0 ||
 481             close_tempfile_gently(buffer_file) < 0) {
 482                 error_errno(_("failed writing detached signature to '%s'"),
 483                             buffer_file->filename.buf);
 484                 delete_tempfile(&buffer_file);
 485                 return -1;
 486         }
 487
 488         if (sigc->payload_timestamp)
 489                 strbuf_addf(&verify_time, "-Overify-time=%s",
 490                         show_date(sigc->payload_timestamp, 0, verify_date_mode));
 491
 492         /* Find the principal from the signers */
 493         strvec_pushl(&ssh_keygen.args, fmt->program,
 494                      "-Y", "find-principals",
 495                      "-f", ssh_allowed_signers,
 496                      "-s", buffer_file->filename.buf,
 497                      verify_time.buf,
 498                      NULL);
 499         ret = pipe_command(&ssh_keygen, NULL, 0, &ssh_principals_out, 0,
 500                            &ssh_principals_err, 0);
 501         if (ret && strstr(ssh_principals_err.buf, "usage:")) {
 502                 error(_("ssh-keygen -Y find-principals/verify is needed for ssh signature verification (available in openssh version 8.2p1+)"));
 503                 goto out;
 504         }
 505         if (ret || !ssh_principals_out.len) {
 506                 /*
 507                  * We did not find a matching principal in the allowedSigners
 508                  * Check without validation
 509                  */
 510                 child_process_init(&ssh_keygen);
 511                 strvec_pushl(&ssh_keygen.args, fmt->program,
 512                              "-Y", "check-novalidate",
 513                              "-n", "git",
 514                              "-s", buffer_file->filename.buf,
 515                              verify_time.buf,
 516                              NULL);
 517                 pipe_command(&ssh_keygen, sigc->payload, sigc->payload_len,
 518                                    &ssh_keygen_out, 0, &ssh_keygen_err, 0);
 519
 520                 /*
 521                  * Fail on unknown keys
 522                  * we still call check-novalidate to display the signature info
 523                  */
 524                 ret = -1;
 525         } else {
 526                 /* Check every principal we found (one per line) */
 527                 const char *next;
 528                 for (line = ssh_principals_out.buf;
 529                      *line;
 530                      line = next) {
 531                         const char *end_of_text;
 532
 533                         next = end_of_text = strchrnul(line, '\n');
 534
 535                          /* Did we find a LF, and did we have CR before it? */
 536                         if (*end_of_text &&
 537                             line < end_of_text &&
 538                             end_of_text[-1] == '\r')
 539                                 end_of_text--;
 540
 541                         /* Unless we hit NUL, skip over the LF we found */
 542                         if (*next)
 543                                 next++;
 544
 545                         /* Not all lines are data.  Skip empty ones */
 546                         if (line == end_of_text)
 547                                 continue;
 548
 549                         /* We now know we have an non-empty line. Process it */
 550                         principal = xmemdupz(line, end_of_text - line);
 551
 552                         child_process_init(&ssh_keygen);
 553                         strbuf_release(&ssh_keygen_out);
 554                         strbuf_release(&ssh_keygen_err);
 555                         strvec_push(&ssh_keygen.args, fmt->program);
 556                         /*
 557                          * We found principals
 558                          * Try with each until we find a match
 559                          */
 560                         strvec_pushl(&ssh_keygen.args, "-Y", "verify",
 561                                      "-n", "git",
 562                                      "-f", ssh_allowed_signers,
 563                                      "-I", principal,
 564                                      "-s", buffer_file->filename.buf,
 565                                      verify_time.buf,
 566                                      NULL);
 567
 568                         if (ssh_revocation_file) {
 569                                 if (file_exists(ssh_revocation_file)) {
 570                                         strvec_pushl(&ssh_keygen.args, "-r",
 571                                                      ssh_revocation_file, NULL);
 572                                 } else {
 573                                         warning(_("ssh signing revocation file configured but not found: %s"),
 574                                                 ssh_revocation_file);
 575                                 }
 576                         }
 577
 578                         sigchain_push(SIGPIPE, SIG_IGN);
 579                         ret = pipe_command(&ssh_keygen, sigc->payload, sigc->payload_len,
 580                                            &ssh_keygen_out, 0, &ssh_keygen_err, 0);
 581                         sigchain_pop(SIGPIPE);
 582
 583                         FREE_AND_NULL(principal);
 584
 585                         if (!ret)
 586                                 ret = !starts_with(ssh_keygen_out.buf, "Good");
 587
 588                         if (!ret)
 589                                 break;
 590                 }
 591         }
 592
 593         strbuf_stripspace(&ssh_keygen_out, NULL);
 594         strbuf_stripspace(&ssh_keygen_err, NULL);
 595         /* Add stderr outputs to show the user actual ssh-keygen errors */
 596         strbuf_add(&ssh_keygen_out, ssh_principals_err.buf, ssh_principals_err.len);
 597         strbuf_add(&ssh_keygen_out, ssh_keygen_err.buf, ssh_keygen_err.len);
 598         sigc->output = strbuf_detach(&ssh_keygen_out, NULL);
 599         sigc->gpg_status = xstrdup(sigc->output);
 600
 601         parse_ssh_output(sigc);
 602
 603 out:
 604         if (buffer_file)
 605                 delete_tempfile(&buffer_file);
 606         strbuf_release(&ssh_principals_out);
 607         strbuf_release(&ssh_principals_err);
 608         strbuf_release(&ssh_keygen_out);
 609         strbuf_release(&ssh_keygen_err);
 610         strbuf_release(&verify_time);
 611
 612         return ret;
 613 }
 614
 615 static int parse_payload_metadata(struct signature_check *sigc)
 616 {
 617         const char *ident_line = NULL;
 618         size_t ident_len;
 619         struct ident_split ident;
 620         const char *signer_header;
 621
 622         switch (sigc->payload_type) {
 623         case SIGNATURE_PAYLOAD_COMMIT:
 624                 signer_header = "committer";
 625                 break;
 626         case SIGNATURE_PAYLOAD_TAG:
 627                 signer_header = "tagger";
 628                 break;
 629         case SIGNATURE_PAYLOAD_UNDEFINED:
 630         case SIGNATURE_PAYLOAD_PUSH_CERT:
 631                 /* Ignore payloads we don't want to parse */
 632                 return 0;
 633         default:
 634                 BUG("invalid value for sigc->payload_type");
 635         }
 636
 637         ident_line = find_commit_header(sigc->payload, signer_header, &ident_len);
 638         if (!ident_line || !ident_len)
 639                 return 1;
 640
 641         if (split_ident_line(&ident, ident_line, ident_len))
 642                 return 1;
 643
 644         if (!sigc->payload_timestamp && ident.date_begin && ident.date_end)
 645                 sigc->payload_timestamp = parse_timestamp(ident.date_begin, NULL, 10);
 646
 647         return 0;
 648 }
 649
 650 int check_signature(struct signature_check *sigc,
 651                     const char *signature, size_t slen)
 652 {
 653         struct gpg_format *fmt;
 654         int status;
 655
 656         gpg_interface_lazy_init();
 657
 658         sigc->result = 'N';
 659         sigc->trust_level = TRUST_UNDEFINED;
 660
 661         fmt = get_format_by_sig(signature);
 662         if (!fmt)
 663                 die(_("bad/incompatible signature '%s'"), signature);
 664
 665         if (parse_payload_metadata(sigc))
 666                 return 1;
 667
 668         status = fmt->verify_signed_buffer(sigc, fmt, signature, slen);
 669
 670         if (status && !sigc->output)
 671                 return !!status;
 672
 673         status |= sigc->result != 'G';
 674         status |= sigc->trust_level < configured_min_trust_level;
 675
 676         return !!status;
 677 }
 678
 679 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 680 {
 681         const char *output = flags & GPG_VERIFY_RAW ? sigc->gpg_status :
 682                                                             sigc->output;
 683
 684         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 685                 fwrite(sigc->payload, 1, sigc->payload_len, stdout);
 686
 687         if (output)
 688                 fputs(output, stderr);
 689 }
 690
 691 size_t parse_signed_buffer(const char *buf, size_t size)
 692 {
 693         size_t len = 0;
 694         size_t match = size;
 695         while (len < size) {
 696                 const char *eol;
 697
 698                 if (get_format_by_sig(buf + len))
 699                         match = len;
 700
 701                 eol = memchr(buf + len, '\n', size - len);
 702                 len += eol ? eol - (buf + len) + 1 : size - len;
 703         }
 704         return match;
 705 }
 706
 707 int parse_signature(const char *buf, size_t size, struct strbuf *payload, struct strbuf *signature)
 708 {
 709         size_t match = parse_signed_buffer(buf, size);
 710         if (match != size) {
 711                 strbuf_add(payload, buf, match);
 712                 remove_signature(payload);
 713                 strbuf_add(signature, buf + match, size - match);
 714                 return 1;
 715         }
 716         return 0;
 717 }
 718
 719 void set_signing_key(const char *key)
 720 {
 721         gpg_interface_lazy_init();
 722
 723         free(configured_signing_key);
 724         configured_signing_key = xstrdup(key);
 725 }
 726
 727 static int git_gpg_config(const char *var, const char *value,
 728                           const struct config_context *ctx UNUSED,
 729                           void *cb UNUSED)
 730 {
 731         struct gpg_format *fmt = NULL;
 732         const char *fmtname = NULL;
 733         char *trust;
 734         int ret;
 735
 736         if (!strcmp(var, "user.signingkey")) {
 737                 if (!value)
 738                         return config_error_nonbool(var);
 739                 set_signing_key(value);
 740                 return 0;
 741         }
 742
 743         if (!strcmp(var, "gpg.format")) {
 744                 if (!value)
 745                         return config_error_nonbool(var);
 746                 fmt = get_format_by_name(value);
 747                 if (!fmt)
 748                         return error(_("invalid value for '%s': '%s'"),
 749                                      var, value);
 750                 use_format = fmt;
 751                 return 0;
 752         }
 753
 754         if (!strcmp(var, "gpg.mintrustlevel")) {
 755                 if (!value)
 756                         return config_error_nonbool(var);
 757
 758                 trust = xstrdup_toupper(value);
 759                 ret = parse_gpg_trust_level(trust, &configured_min_trust_level);
 760                 free(trust);
 761
 762                 if (ret)
 763                         return error(_("invalid value for '%s': '%s'"),
 764                                      var, value);
 765                 return 0;
 766         }
 767
 768         if (!strcmp(var, "gpg.ssh.defaultkeycommand"))
 769                 return git_config_string(&ssh_default_key_command, var, value);
 770
 771         if (!strcmp(var, "gpg.ssh.allowedsignersfile"))
 772                 return git_config_pathname(&ssh_allowed_signers, var, value);
 773
 774         if (!strcmp(var, "gpg.ssh.revocationfile"))
 775                 return git_config_pathname(&ssh_revocation_file, var, value);
 776
 777         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 778                 fmtname = "openpgp";
 779
 780         if (!strcmp(var, "gpg.x509.program"))
 781                 fmtname = "x509";
 782
 783         if (!strcmp(var, "gpg.ssh.program"))
 784                 fmtname = "ssh";
 785
 786         if (fmtname) {
 787                 fmt = get_format_by_name(fmtname);
 788                 return git_config_string((char **) &fmt->program, var, value);
 789         }
 790
 791         return 0;
 792 }
 793
 794 /*
 795  * Returns 1 if `string` contains a literal ssh key, 0 otherwise
 796  * `key` will be set to the start of the actual key if a prefix is present.
 797  */
 798 static int is_literal_ssh_key(const char *string, const char **key)
 799 {
 800         if (skip_prefix(string, "key::", key))
 801                 return 1;
 802         if (starts_with(string, "ssh-")) {
 803                 *key = string;
 804                 return 1;
 805         }
 806         return 0;
 807 }
 808
 809 static char *get_ssh_key_fingerprint(const char *signing_key)
 810 {
 811         struct child_process ssh_keygen = CHILD_PROCESS_INIT;
 812         int ret = -1;
 813         struct strbuf fingerprint_stdout = STRBUF_INIT;
 814         struct strbuf **fingerprint;
 815         char *fingerprint_ret;
 816         const char *literal_key = NULL;
 817
 818         /*
 819          * With SSH Signing this can contain a filename or a public key
 820          * For textual representation we usually want a fingerprint
 821          */
 822         if (is_literal_ssh_key(signing_key, &literal_key)) {
 823                 strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf", "-", NULL);
 824                 ret = pipe_command(&ssh_keygen, literal_key,
 825                                    strlen(literal_key), &fingerprint_stdout, 0,
 826                                    NULL, 0);
 827         } else {
 828                 strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf",
 829                              configured_signing_key, NULL);
 830                 ret = pipe_command(&ssh_keygen, NULL, 0, &fingerprint_stdout, 0,
 831                                    NULL, 0);
 832         }
 833
 834         if (!!ret)
 835                 die_errno(_("failed to get the ssh fingerprint for key '%s'"),
 836                           signing_key);
 837
 838         fingerprint = strbuf_split_max(&fingerprint_stdout, ' ', 3);
 839         if (!fingerprint[1])
 840                 die_errno(_("failed to get the ssh fingerprint for key '%s'"),
 841                           signing_key);
 842
 843         fingerprint_ret = strbuf_detach(fingerprint[1], NULL);
 844         strbuf_list_free(fingerprint);
 845         strbuf_release(&fingerprint_stdout);
 846         return fingerprint_ret;
 847 }
 848
 849 /* Returns the first public key from an ssh-agent to use for signing */
 850 static char *get_default_ssh_signing_key(void)
 851 {
 852         struct child_process ssh_default_key = CHILD_PROCESS_INIT;
 853         int ret = -1;
 854         struct strbuf key_stdout = STRBUF_INIT, key_stderr = STRBUF_INIT;
 855         struct strbuf **keys;
 856         char *key_command = NULL;
 857         const char **argv;
 858         int n;
 859         char *default_key = NULL;
 860         const char *literal_key = NULL;
 861
 862         if (!ssh_default_key_command)
 863                 die(_("either user.signingkey or gpg.ssh.defaultKeyCommand needs to be configured"));
 864
 865         key_command = xstrdup(ssh_default_key_command);
 866         n = split_cmdline(key_command, &argv);
 867
 868         if (n < 0)
 869                 die("malformed build-time gpg.ssh.defaultKeyCommand: %s",
 870                     split_cmdline_strerror(n));
 871
 872         strvec_pushv(&ssh_default_key.args, argv);
 873         ret = pipe_command(&ssh_default_key, NULL, 0, &key_stdout, 0,
 874                            &key_stderr, 0);
 875
 876         if (!ret) {
 877                 keys = strbuf_split_max(&key_stdout, '\n', 2);
 878                 if (keys[0] && is_literal_ssh_key(keys[0]->buf, &literal_key)) {
 879                         /*
 880                          * We only use `is_literal_ssh_key` here to check validity
 881                          * The prefix will be stripped when the key is used.
 882                          */
 883                         default_key = strbuf_detach(keys[0], NULL);
 884                 } else {
 885                         warning(_("gpg.ssh.defaultKeyCommand succeeded but returned no keys: %s %s"),
 886                                 key_stderr.buf, key_stdout.buf);
 887                 }
 888
 889                 strbuf_list_free(keys);
 890         } else {
 891                 warning(_("gpg.ssh.defaultKeyCommand failed: %s %s"),
 892                         key_stderr.buf, key_stdout.buf);
 893         }
 894
 895         free(key_command);
 896         free(argv);
 897         strbuf_release(&key_stdout);
 898
 899         return default_key;
 900 }
 901
 902 static char *get_ssh_key_id(void)
 903 {
 904         char *signing_key = get_signing_key();
 905         char *key_id = get_ssh_key_fingerprint(signing_key);
 906         free(signing_key);
 907         return key_id;
 908 }
 909
 910 /* Returns a textual but unique representation of the signing key */
 911 char *get_signing_key_id(void)
 912 {
 913         gpg_interface_lazy_init();
 914
 915         if (use_format->get_key_id) {
 916                 return use_format->get_key_id();
 917         }
 918
 919         /* GPG/GPGSM only store a key id on this variable */
 920         return get_signing_key();
 921 }
 922
 923 char *get_signing_key(void)
 924 {
 925         gpg_interface_lazy_init();
 926
 927         if (configured_signing_key)
 928                 return xstrdup(configured_signing_key);
 929         if (use_format->get_default_key) {
 930                 return use_format->get_default_key();
 931         }
 932
 933         return xstrdup(git_committer_info(IDENT_STRICT | IDENT_NO_DATE));
 934 }
 935
 936 const char *gpg_trust_level_to_str(enum signature_trust_level level)
 937 {
 938         struct sigcheck_gpg_trust_level *trust;
 939
 940         if (level < 0 || level >= ARRAY_SIZE(sigcheck_gpg_trust_level))
 941                 BUG("invalid trust level requested %d", level);
 942
 943         trust = &sigcheck_gpg_trust_level[level];
 944         if (trust->value != level)
 945                 BUG("sigcheck_gpg_trust_level[] unsorted");
 946
 947         return sigcheck_gpg_trust_level[level].display_key;
 948 }
 949
 950 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 951 {
 952         gpg_interface_lazy_init();
 953
 954         return use_format->sign_buffer(buffer, signature, signing_key);
 955 }
 956
 957 /*
 958  * Strip CR from the line endings, in case we are on Windows.
 959  * NEEDSWORK: make it trim only CRs before LFs and rename
 960  */
 961 static void remove_cr_after(struct strbuf *buffer, size_t offset)
 962 {
 963         size_t i, j;
 964
 965         for (i = j = offset; i < buffer->len; i++) {
 966                 if (buffer->buf[i] != '\r') {
 967                         if (i != j)
 968                                 buffer->buf[j] = buffer->buf[i];
 969                         j++;
 970                 }
 971         }
 972         strbuf_setlen(buffer, j);
 973 }
 974
 975 static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
 976                           const char *signing_key)
 977 {
 978         struct child_process gpg = CHILD_PROCESS_INIT;
 979         int ret;
 980         size_t bottom;
 981         const char *cp;
 982         struct strbuf gpg_status = STRBUF_INIT;
 983
 984         strvec_pushl(&gpg.args,
 985                      use_format->program,
 986                      "--status-fd=2",
 987                      "-bsau", signing_key,
 988                      NULL);
 989
 990         bottom = signature->len;
 991
 992         /*
 993          * When the username signingkey is bad, program could be terminated
 994          * because gpg exits without reading and then write gets SIGPIPE.
 995          */
 996         sigchain_push(SIGPIPE, SIG_IGN);
 997         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 998                            signature, 1024, &gpg_status, 0);
 999         sigchain_pop(SIGPIPE);
1000
1001         for (cp = gpg_status.buf;
1002              cp && (cp = strstr(cp, "[GNUPG:] SIG_CREATED "));
1003              cp++) {
1004                 if (cp == gpg_status.buf || cp[-1] == '\n')
1005                         break; /* found */
1006         }
1007         ret |= !cp;
1008         if (ret) {
1009                 error(_("gpg failed to sign the data:\n%s"),
1010                       gpg_status.len ? gpg_status.buf : "(no gpg output)");
1011                 strbuf_release(&gpg_status);
1012                 return -1;
1013         }
1014         strbuf_release(&gpg_status);
1015
1016         /* Strip CR from the line endings, in case we are on Windows. */
1017         remove_cr_after(signature, bottom);
1018
1019         return 0;
1020 }
1021
1022 static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
1023                            const char *signing_key)
1024 {
1025         struct child_process signer = CHILD_PROCESS_INIT;
1026         int ret = -1;
1027         size_t bottom, keylen;
1028         struct strbuf signer_stderr = STRBUF_INIT;
1029         struct tempfile *key_file = NULL, *buffer_file = NULL;
1030         char *ssh_signing_key_file = NULL;
1031         struct strbuf ssh_signature_filename = STRBUF_INIT;
1032         const char *literal_key = NULL;
1033         int literal_ssh_key = 0;
1034
1035         if (!signing_key || signing_key[0] == '\0')
1036                 return error(
1037                         _("user.signingKey needs to be set for ssh signing"));
1038
1039         if (is_literal_ssh_key(signing_key, &literal_key)) {
1040                 /* A literal ssh key */
1041                 literal_ssh_key = 1;
1042                 key_file = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
1043                 if (!key_file)
1044                         return error_errno(
1045                                 _("could not create temporary file"));
1046                 keylen = strlen(literal_key);
1047                 if (write_in_full(key_file->fd, literal_key, keylen) < 0 ||
1048                     close_tempfile_gently(key_file) < 0) {
1049                         error_errno(_("failed writing ssh signing key to '%s'"),
1050                                     key_file->filename.buf);
1051                         goto out;
1052                 }
1053                 ssh_signing_key_file = strbuf_detach(&key_file->filename, NULL);
1054         } else {
1055                 /* We assume a file */
1056                 ssh_signing_key_file = interpolate_path(signing_key, 1);
1057         }
1058
1059         buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
1060         if (!buffer_file) {
1061                 error_errno(_("could not create temporary file"));
1062                 goto out;
1063         }
1064
1065         if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
1066             close_tempfile_gently(buffer_file) < 0) {
1067                 error_errno(_("failed writing ssh signing key buffer to '%s'"),
1068                             buffer_file->filename.buf);
1069                 goto out;
1070         }
1071
1072         strvec_pushl(&signer.args, use_format->program,
1073                      "-Y", "sign",
1074                      "-n", "git",
1075                      "-f", ssh_signing_key_file,
1076                      NULL);
1077         if (literal_ssh_key)
1078                 strvec_push(&signer.args, "-U");
1079         strvec_push(&signer.args, buffer_file->filename.buf);
1080
1081         sigchain_push(SIGPIPE, SIG_IGN);
1082         ret = pipe_command(&signer, NULL, 0, NULL, 0, &signer_stderr, 0);
1083         sigchain_pop(SIGPIPE);
1084
1085         if (ret) {
1086                 if (strstr(signer_stderr.buf, "usage:"))
1087                         error(_("ssh-keygen -Y sign is needed for ssh signing (available in openssh version 8.2p1+)"));
1088
1089                 ret = error("%s", signer_stderr.buf);
1090                 goto out;
1091         }
1092
1093         bottom = signature->len;
1094
1095         strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
1096         strbuf_addstr(&ssh_signature_filename, ".sig");
1097         if (strbuf_read_file(signature, ssh_signature_filename.buf, 0) < 0) {
1098                 ret = error_errno(
1099                         _("failed reading ssh signing data buffer from '%s'"),
1100                         ssh_signature_filename.buf);
1101                 goto out;
1102         }
1103         /* Strip CR from the line endings, in case we are on Windows. */
1104         remove_cr_after(signature, bottom);
1105
1106 out:
1107         if (key_file)
1108                 delete_tempfile(&key_file);
1109         if (buffer_file)
1110                 delete_tempfile(&buffer_file);
1111         if (ssh_signature_filename.len)
1112                 unlink_or_warn(ssh_signature_filename.buf);
1113         strbuf_release(&signer_stderr);
1114         strbuf_release(&ssh_signature_filename);
1115         FREE_AND_NULL(ssh_signing_key_file);
1116         return ret;
1117 }