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 "gpg-interface.h"
   7 #include "sigchain.h"
   8 #include "tempfile.h"
   9
  10 static char *configured_signing_key;
  11 static enum signature_trust_level configured_min_trust_level = TRUST_UNDEFINED;
  12
  13 struct gpg_format {
  14         const char *name;
  15         const char *program;
  16         const char **verify_args;
  17         const char **sigs;
  18 };
  19
  20 static const char *openpgp_verify_args[] = {
  21         "--keyid-format=long",
  22         NULL
  23 };
  24 static const char *openpgp_sigs[] = {
  25         "-----BEGIN PGP SIGNATURE-----",
  26         "-----BEGIN PGP MESSAGE-----",
  27         NULL
  28 };
  29
  30 static const char *x509_verify_args[] = {
  31         NULL
  32 };
  33 static const char *x509_sigs[] = {
  34         "-----BEGIN SIGNED MESSAGE-----",
  35         NULL
  36 };
  37
  38 static struct gpg_format gpg_format[] = {
  39         { .name = "openpgp", .program = "gpg",
  40           .verify_args = openpgp_verify_args,
  41           .sigs = openpgp_sigs
  42         },
  43         { .name = "x509", .program = "gpgsm",
  44           .verify_args = x509_verify_args,
  45           .sigs = x509_sigs
  46         },
  47 };
  48
  49 static struct gpg_format *use_format = &gpg_format[0];
  50
  51 static struct gpg_format *get_format_by_name(const char *str)
  52 {
  53         int i;
  54
  55         for (i = 0; i < ARRAY_SIZE(gpg_format); i++)
  56                 if (!strcmp(gpg_format[i].name, str))
  57                         return gpg_format + i;
  58         return NULL;
  59 }
  60
  61 static struct gpg_format *get_format_by_sig(const char *sig)
  62 {
  63         int i, j;
  64
  65         for (i = 0; i < ARRAY_SIZE(gpg_format); i++)
  66                 for (j = 0; gpg_format[i].sigs[j]; j++)
  67                         if (starts_with(sig, gpg_format[i].sigs[j]))
  68                                 return gpg_format + i;
  69         return NULL;
  70 }
  71
  72 void signature_check_clear(struct signature_check *sigc)
  73 {
  74         FREE_AND_NULL(sigc->payload);
  75         FREE_AND_NULL(sigc->gpg_output);
  76         FREE_AND_NULL(sigc->gpg_status);
  77         FREE_AND_NULL(sigc->signer);
  78         FREE_AND_NULL(sigc->key);
  79         FREE_AND_NULL(sigc->fingerprint);
  80         FREE_AND_NULL(sigc->primary_key_fingerprint);
  81 }
  82
  83 /* An exclusive status -- only one of them can appear in output */
  84 #define GPG_STATUS_EXCLUSIVE    (1<<0)
  85 /* The status includes key identifier */
  86 #define GPG_STATUS_KEYID        (1<<1)
  87 /* The status includes user identifier */
  88 #define GPG_STATUS_UID          (1<<2)
  89 /* The status includes key fingerprints */
  90 #define GPG_STATUS_FINGERPRINT  (1<<3)
  91 /* The status includes trust level */
  92 #define GPG_STATUS_TRUST_LEVEL  (1<<4)
  93
  94 /* Short-hand for standard exclusive *SIG status with keyid & UID */
  95 #define GPG_STATUS_STDSIG       (GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID|GPG_STATUS_UID)
  96
  97 static struct {
  98         char result;
  99         const char *check;
 100         unsigned int flags;
 101 } sigcheck_gpg_status[] = {
 102         { 'G', "GOODSIG ", GPG_STATUS_STDSIG },
 103         { 'B', "BADSIG ", GPG_STATUS_STDSIG },
 104         { 'E', "ERRSIG ", GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID },
 105         { 'X', "EXPSIG ", GPG_STATUS_STDSIG },
 106         { 'Y', "EXPKEYSIG ", GPG_STATUS_STDSIG },
 107         { 'R', "REVKEYSIG ", GPG_STATUS_STDSIG },
 108         { 0, "VALIDSIG ", GPG_STATUS_FINGERPRINT },
 109         { 0, "TRUST_", GPG_STATUS_TRUST_LEVEL },
 110 };
 111
 112 static struct {
 113         const char *key;
 114         enum signature_trust_level value;
 115 } sigcheck_gpg_trust_level[] = {
 116         { "UNDEFINED", TRUST_UNDEFINED },
 117         { "NEVER", TRUST_NEVER },
 118         { "MARGINAL", TRUST_MARGINAL },
 119         { "FULLY", TRUST_FULLY },
 120         { "ULTIMATE", TRUST_ULTIMATE },
 121 };
 122
 123 static void replace_cstring(char **field, const char *line, const char *next)
 124 {
 125         free(*field);
 126
 127         if (line && next)
 128                 *field = xmemdupz(line, next - line);
 129         else
 130                 *field = NULL;
 131 }
 132
 133 static int parse_gpg_trust_level(const char *level,
 134                                  enum signature_trust_level *res)
 135 {
 136         size_t i;
 137
 138         for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_trust_level); i++) {
 139                 if (!strcmp(sigcheck_gpg_trust_level[i].key, level)) {
 140                         *res = sigcheck_gpg_trust_level[i].value;
 141                         return 0;
 142                 }
 143         }
 144         return 1;
 145 }
 146
 147 static void parse_gpg_output(struct signature_check *sigc)
 148 {
 149         const char *buf = sigc->gpg_status;
 150         const char *line, *next;
 151         int i, j;
 152         int seen_exclusive_status = 0;
 153
 154         /* Iterate over all lines */
 155         for (line = buf; *line; line = strchrnul(line+1, '\n')) {
 156                 while (*line == '\n')
 157                         line++;
 158                 if (!*line)
 159                         break;
 160
 161                 /* Skip lines that don't start with GNUPG status */
 162                 if (!skip_prefix(line, "[GNUPG:] ", &line))
 163                         continue;
 164
 165                 /* Iterate over all search strings */
 166                 for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
 167                         if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
 168                                 /*
 169                                  * GOODSIG, BADSIG etc. can occur only once for
 170                                  * each signature.  Therefore, if we had more
 171                                  * than one then we're dealing with multiple
 172                                  * signatures.  We don't support them
 173                                  * currently, and they're rather hard to
 174                                  * create, so something is likely fishy and we
 175                                  * should reject them altogether.
 176                                  */
 177                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
 178                                         if (seen_exclusive_status++)
 179                                                 goto error;
 180                                 }
 181
 182                                 if (sigcheck_gpg_status[i].result)
 183                                         sigc->result = sigcheck_gpg_status[i].result;
 184                                 /* Do we have key information? */
 185                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_KEYID) {
 186                                         next = strchrnul(line, ' ');
 187                                         replace_cstring(&sigc->key, line, next);
 188                                         /* Do we have signer information? */
 189                                         if (*next && (sigcheck_gpg_status[i].flags & GPG_STATUS_UID)) {
 190                                                 line = next + 1;
 191                                                 next = strchrnul(line, '\n');
 192                                                 replace_cstring(&sigc->signer, line, next);
 193                                         }
 194                                 }
 195
 196                                 /* Do we have trust level? */
 197                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_TRUST_LEVEL) {
 198                                         /*
 199                                          * GPG v1 and v2 differs in how the
 200                                          * TRUST_ lines are written.  Some
 201                                          * trust lines contain no additional
 202                                          * space-separated information for v1.
 203                                          */
 204                                         size_t trust_size = strcspn(line, " \n");
 205                                         char *trust = xmemdupz(line, trust_size);
 206
 207                                         if (parse_gpg_trust_level(trust, &sigc->trust_level)) {
 208                                                 free(trust);
 209                                                 goto error;
 210                                         }
 211                                         free(trust);
 212                                 }
 213
 214                                 /* Do we have fingerprint? */
 215                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
 216                                         const char *limit;
 217                                         char **field;
 218
 219                                         next = strchrnul(line, ' ');
 220                                         replace_cstring(&sigc->fingerprint, line, next);
 221
 222                                         /*
 223                                          * Skip interim fields.  The search is
 224                                          * limited to the same line since only
 225                                          * OpenPGP signatures has a field with
 226                                          * the primary fingerprint.
 227                                          */
 228                                         limit = strchrnul(line, '\n');
 229                                         for (j = 9; j > 0; j--) {
 230                                                 if (!*next || limit <= next)
 231                                                         break;
 232                                                 line = next + 1;
 233                                                 next = strchrnul(line, ' ');
 234                                         }
 235
 236                                         field = &sigc->primary_key_fingerprint;
 237                                         if (!j) {
 238                                                 next = strchrnul(line, '\n');
 239                                                 replace_cstring(field, line, next);
 240                                         } else {
 241                                                 replace_cstring(field, NULL, NULL);
 242                                         }
 243                                 }
 244
 245                                 break;
 246                         }
 247                 }
 248         }
 249         return;
 250
 251 error:
 252         sigc->result = 'E';
 253         /* Clear partial data to avoid confusion */
 254         FREE_AND_NULL(sigc->primary_key_fingerprint);
 255         FREE_AND_NULL(sigc->fingerprint);
 256         FREE_AND_NULL(sigc->signer);
 257         FREE_AND_NULL(sigc->key);
 258 }
 259
 260 static int verify_signed_buffer(const char *payload, size_t payload_size,
 261                                 const char *signature, size_t signature_size,
 262                                 struct strbuf *gpg_output,
 263                                 struct strbuf *gpg_status)
 264 {
 265         struct child_process gpg = CHILD_PROCESS_INIT;
 266         struct gpg_format *fmt;
 267         struct tempfile *temp;
 268         int ret;
 269         struct strbuf buf = STRBUF_INIT;
 270
 271         temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 272         if (!temp)
 273                 return error_errno(_("could not create temporary file"));
 274         if (write_in_full(temp->fd, signature, signature_size) < 0 ||
 275             close_tempfile_gently(temp) < 0) {
 276                 error_errno(_("failed writing detached signature to '%s'"),
 277                             temp->filename.buf);
 278                 delete_tempfile(&temp);
 279                 return -1;
 280         }
 281
 282         fmt = get_format_by_sig(signature);
 283         if (!fmt)
 284                 BUG("bad signature '%s'", signature);
 285
 286         strvec_push(&gpg.args, fmt->program);
 287         strvec_pushv(&gpg.args, fmt->verify_args);
 288         strvec_pushl(&gpg.args,
 289                      "--status-fd=1",
 290                      "--verify", temp->filename.buf, "-",
 291                      NULL);
 292
 293         if (!gpg_status)
 294                 gpg_status = &buf;
 295
 296         sigchain_push(SIGPIPE, SIG_IGN);
 297         ret = pipe_command(&gpg, payload, payload_size,
 298                            gpg_status, 0, gpg_output, 0);
 299         sigchain_pop(SIGPIPE);
 300
 301         delete_tempfile(&temp);
 302
 303         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
 304         strbuf_release(&buf); /* no matter it was used or not */
 305
 306         return ret;
 307 }
 308
 309 int check_signature(const char *payload, size_t plen, const char *signature,
 310         size_t slen, struct signature_check *sigc)
 311 {
 312         struct strbuf gpg_output = STRBUF_INIT;
 313         struct strbuf gpg_status = STRBUF_INIT;
 314         int status;
 315
 316         sigc->result = 'N';
 317         sigc->trust_level = -1;
 318
 319         status = verify_signed_buffer(payload, plen, signature, slen,
 320                                       &gpg_output, &gpg_status);
 321         if (status && !gpg_output.len)
 322                 goto out;
 323         sigc->payload = xmemdupz(payload, plen);
 324         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
 325         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
 326         parse_gpg_output(sigc);
 327         status |= sigc->result != 'G';
 328         status |= sigc->trust_level < configured_min_trust_level;
 329
 330  out:
 331         strbuf_release(&gpg_status);
 332         strbuf_release(&gpg_output);
 333
 334         return !!status;
 335 }
 336
 337 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 338 {
 339         const char *output = flags & GPG_VERIFY_RAW ?
 340                 sigc->gpg_status : sigc->gpg_output;
 341
 342         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 343                 fputs(sigc->payload, stdout);
 344
 345         if (output)
 346                 fputs(output, stderr);
 347 }
 348
 349 size_t parse_signed_buffer(const char *buf, size_t size)
 350 {
 351         size_t len = 0;
 352         size_t match = size;
 353         while (len < size) {
 354                 const char *eol;
 355
 356                 if (get_format_by_sig(buf + len))
 357                         match = len;
 358
 359                 eol = memchr(buf + len, '\n', size - len);
 360                 len += eol ? eol - (buf + len) + 1 : size - len;
 361         }
 362         return match;
 363 }
 364
 365 int parse_signature(const char *buf, size_t size, struct strbuf *payload, struct strbuf *signature)
 366 {
 367         size_t match = parse_signed_buffer(buf, size);
 368         if (match != size) {
 369                 strbuf_add(payload, buf, match);
 370                 remove_signature(payload);
 371                 strbuf_add(signature, buf + match, size - match);
 372                 return 1;
 373         }
 374         return 0;
 375 }
 376
 377 void set_signing_key(const char *key)
 378 {
 379         free(configured_signing_key);
 380         configured_signing_key = xstrdup(key);
 381 }
 382
 383 int git_gpg_config(const char *var, const char *value, void *cb)
 384 {
 385         struct gpg_format *fmt = NULL;
 386         char *fmtname = NULL;
 387         char *trust;
 388         int ret;
 389
 390         if (!strcmp(var, "user.signingkey")) {
 391                 if (!value)
 392                         return config_error_nonbool(var);
 393                 set_signing_key(value);
 394                 return 0;
 395         }
 396
 397         if (!strcmp(var, "gpg.format")) {
 398                 if (!value)
 399                         return config_error_nonbool(var);
 400                 fmt = get_format_by_name(value);
 401                 if (!fmt)
 402                         return error("unsupported value for %s: %s",
 403                                      var, value);
 404                 use_format = fmt;
 405                 return 0;
 406         }
 407
 408         if (!strcmp(var, "gpg.mintrustlevel")) {
 409                 if (!value)
 410                         return config_error_nonbool(var);
 411
 412                 trust = xstrdup_toupper(value);
 413                 ret = parse_gpg_trust_level(trust, &configured_min_trust_level);
 414                 free(trust);
 415
 416                 if (ret)
 417                         return error("unsupported value for %s: %s", var,
 418                                      value);
 419                 return 0;
 420         }
 421
 422         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 423                 fmtname = "openpgp";
 424
 425         if (!strcmp(var, "gpg.x509.program"))
 426                 fmtname = "x509";
 427
 428         if (fmtname) {
 429                 fmt = get_format_by_name(fmtname);
 430                 return git_config_string(&fmt->program, var, value);
 431         }
 432
 433         return 0;
 434 }
 435
 436 const char *get_signing_key(void)
 437 {
 438         if (configured_signing_key)
 439                 return configured_signing_key;
 440         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 441 }
 442
 443 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 444 {
 445         struct child_process gpg = CHILD_PROCESS_INIT;
 446         int ret;
 447         size_t i, j, bottom;
 448         struct strbuf gpg_status = STRBUF_INIT;
 449
 450         strvec_pushl(&gpg.args,
 451                      use_format->program,
 452                      "--status-fd=2",
 453                      "-bsau", signing_key,
 454                      NULL);
 455
 456         bottom = signature->len;
 457
 458         /*
 459          * When the username signingkey is bad, program could be terminated
 460          * because gpg exits without reading and then write gets SIGPIPE.
 461          */
 462         sigchain_push(SIGPIPE, SIG_IGN);
 463         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 464                            signature, 1024, &gpg_status, 0);
 465         sigchain_pop(SIGPIPE);
 466
 467         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 468         strbuf_release(&gpg_status);
 469         if (ret)
 470                 return error(_("gpg failed to sign the data"));
 471
 472         /* Strip CR from the line endings, in case we are on Windows. */
 473         for (i = j = bottom; i < signature->len; i++)
 474                 if (signature->buf[i] != '\r') {
 475                         if (i != j)
 476                                 signature->buf[j] = signature->buf[i];
 477                         j++;
 478                 }
 479         strbuf_setlen(signature, j);
 480
 481         return 0;
 482 }