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 static int verify_signed_buffer(const char *payload, size_t payload_size,
 260                                 const char *signature, size_t signature_size,
 261                                 struct strbuf *gpg_output,
 262                                 struct strbuf *gpg_status)
 263 {
 264         struct child_process gpg = CHILD_PROCESS_INIT;
 265         struct gpg_format *fmt;
 266         struct tempfile *temp;
 267         int ret;
 268         struct strbuf buf = STRBUF_INIT;
 269
 270         temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 271         if (!temp)
 272                 return error_errno(_("could not create temporary file"));
 273         if (write_in_full(temp->fd, signature, signature_size) < 0 ||
 274             close_tempfile_gently(temp) < 0) {
 275                 error_errno(_("failed writing detached signature to '%s'"),
 276                             temp->filename.buf);
 277                 delete_tempfile(&temp);
 278                 return -1;
 279         }
 280
 281         fmt = get_format_by_sig(signature);
 282         if (!fmt)
 283                 BUG("bad signature '%s'", signature);
 284
 285         strvec_push(&gpg.args, fmt->program);
 286         strvec_pushv(&gpg.args, fmt->verify_args);
 287         strvec_pushl(&gpg.args,
 288                      "--status-fd=1",
 289                      "--verify", temp->filename.buf, "-",
 290                      NULL);
 291
 292         if (!gpg_status)
 293                 gpg_status = &buf;
 294
 295         sigchain_push(SIGPIPE, SIG_IGN);
 296         ret = pipe_command(&gpg, payload, payload_size,
 297                            gpg_status, 0, gpg_output, 0);
 298         sigchain_pop(SIGPIPE);
 299
 300         delete_tempfile(&temp);
 301
 302         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
 303         strbuf_release(&buf); /* no matter it was used or not */
 304
 305         return ret;
 306 }
 307
 308 int check_signature(const char *payload, size_t plen, const char *signature,
 309         size_t slen, struct signature_check *sigc)
 310 {
 311         struct strbuf gpg_output = STRBUF_INIT;
 312         struct strbuf gpg_status = STRBUF_INIT;
 313         int status;
 314
 315         sigc->result = 'N';
 316         sigc->trust_level = -1;
 317
 318         status = verify_signed_buffer(payload, plen, signature, slen,
 319                                       &gpg_output, &gpg_status);
 320         if (status && !gpg_output.len)
 321                 goto out;
 322         sigc->payload = xmemdupz(payload, plen);
 323         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
 324         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
 325         parse_gpg_output(sigc);
 326         status |= sigc->result != 'G';
 327         status |= sigc->trust_level < configured_min_trust_level;
 328
 329  out:
 330         strbuf_release(&gpg_status);
 331         strbuf_release(&gpg_output);
 332
 333         return !!status;
 334 }
 335
 336 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 337 {
 338         const char *output = flags & GPG_VERIFY_RAW ?
 339                 sigc->gpg_status : sigc->gpg_output;
 340
 341         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 342                 fputs(sigc->payload, stdout);
 343
 344         if (output)
 345                 fputs(output, stderr);
 346 }
 347
 348 size_t parse_signature(const char *buf, size_t size)
 349 {
 350         size_t len = 0;
 351         size_t match = size;
 352         while (len < size) {
 353                 const char *eol;
 354
 355                 if (get_format_by_sig(buf + len))
 356                         match = len;
 357
 358                 eol = memchr(buf + len, '\n', size - len);
 359                 len += eol ? eol - (buf + len) + 1 : size - len;
 360         }
 361         return match;
 362 }
 363
 364 void set_signing_key(const char *key)
 365 {
 366         free(configured_signing_key);
 367         configured_signing_key = xstrdup(key);
 368 }
 369
 370 int git_gpg_config(const char *var, const char *value, void *cb)
 371 {
 372         struct gpg_format *fmt = NULL;
 373         char *fmtname = NULL;
 374         char *trust;
 375         int ret;
 376
 377         if (!strcmp(var, "user.signingkey")) {
 378                 if (!value)
 379                         return config_error_nonbool(var);
 380                 set_signing_key(value);
 381                 return 0;
 382         }
 383
 384         if (!strcmp(var, "gpg.format")) {
 385                 if (!value)
 386                         return config_error_nonbool(var);
 387                 fmt = get_format_by_name(value);
 388                 if (!fmt)
 389                         return error("unsupported value for %s: %s",
 390                                      var, value);
 391                 use_format = fmt;
 392                 return 0;
 393         }
 394
 395         if (!strcmp(var, "gpg.mintrustlevel")) {
 396                 if (!value)
 397                         return config_error_nonbool(var);
 398
 399                 trust = xstrdup_toupper(value);
 400                 ret = parse_gpg_trust_level(trust, &configured_min_trust_level);
 401                 free(trust);
 402
 403                 if (ret)
 404                         return error("unsupported value for %s: %s", var,
 405                                      value);
 406                 return 0;
 407         }
 408
 409         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 410                 fmtname = "openpgp";
 411
 412         if (!strcmp(var, "gpg.x509.program"))
 413                 fmtname = "x509";
 414
 415         if (fmtname) {
 416                 fmt = get_format_by_name(fmtname);
 417                 return git_config_string(&fmt->program, var, value);
 418         }
 419
 420         return 0;
 421 }
 422
 423 const char *get_signing_key(void)
 424 {
 425         if (configured_signing_key)
 426                 return configured_signing_key;
 427         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 428 }
 429
 430 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 431 {
 432         struct child_process gpg = CHILD_PROCESS_INIT;
 433         int ret;
 434         size_t i, j, bottom;
 435         struct strbuf gpg_status = STRBUF_INIT;
 436
 437         strvec_pushl(&gpg.args,
 438                      use_format->program,
 439                      "--status-fd=2",
 440                      "-bsau", signing_key,
 441                      NULL);
 442
 443         bottom = signature->len;
 444
 445         /*
 446          * When the username signingkey is bad, program could be terminated
 447          * because gpg exits without reading and then write gets SIGPIPE.
 448          */
 449         sigchain_push(SIGPIPE, SIG_IGN);
 450         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 451                            signature, 1024, &gpg_status, 0);
 452         sigchain_pop(SIGPIPE);
 453
 454         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 455         strbuf_release(&gpg_status);
 456         if (ret)
 457                 return error(_("gpg failed to sign the data"));
 458
 459         /* Strip CR from the line endings, in case we are on Windows. */
 460         for (i = j = bottom; i < signature->len; i++)
 461                 if (signature->buf[i] != '\r') {
 462                         if (i != j)
 463                                 signature->buf[j] = signature->buf[i];
 464                         j++;
 465                 }
 466         strbuf_setlen(signature, j);
 467
 468         return 0;
 469 }