gpg-interface.c

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