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