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 int check_signature(const char *payload, size_t plen, const char *signature,
 211         size_t slen, struct signature_check *sigc)
 212 {
 213         struct strbuf gpg_output = STRBUF_INIT;
 214         struct strbuf gpg_status = STRBUF_INIT;
 215         int status;
 216
 217         sigc->result = 'N';
 218
 219         status = verify_signed_buffer(payload, plen, signature, slen,
 220                                       &gpg_output, &gpg_status);
 221         if (status && !gpg_output.len)
 222                 goto out;
 223         sigc->payload = xmemdupz(payload, plen);
 224         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
 225         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
 226         parse_gpg_output(sigc);
 227         status |= sigc->result != 'G' && sigc->result != 'U';
 228
 229  out:
 230         strbuf_release(&gpg_status);
 231         strbuf_release(&gpg_output);
 232
 233         return !!status;
 234 }
 235
 236 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 237 {
 238         const char *output = flags & GPG_VERIFY_RAW ?
 239                 sigc->gpg_status : sigc->gpg_output;
 240
 241         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 242                 fputs(sigc->payload, stdout);
 243
 244         if (output)
 245                 fputs(output, stderr);
 246 }
 247
 248 size_t parse_signature(const char *buf, size_t size)
 249 {
 250         size_t len = 0;
 251         size_t match = size;
 252         while (len < size) {
 253                 const char *eol;
 254
 255                 if (get_format_by_sig(buf + len))
 256                         match = len;
 257
 258                 eol = memchr(buf + len, '\n', size - len);
 259                 len += eol ? eol - (buf + len) + 1 : size - len;
 260         }
 261         return match;
 262 }
 263
 264 void set_signing_key(const char *key)
 265 {
 266         free(configured_signing_key);
 267         configured_signing_key = xstrdup(key);
 268 }
 269
 270 int git_gpg_config(const char *var, const char *value, void *cb)
 271 {
 272         struct gpg_format *fmt = NULL;
 273         char *fmtname = NULL;
 274
 275         if (!strcmp(var, "user.signingkey")) {
 276                 if (!value)
 277                         return config_error_nonbool(var);
 278                 set_signing_key(value);
 279                 return 0;
 280         }
 281
 282         if (!strcmp(var, "gpg.format")) {
 283                 if (!value)
 284                         return config_error_nonbool(var);
 285                 fmt = get_format_by_name(value);
 286                 if (!fmt)
 287                         return error("unsupported value for %s: %s",
 288                                      var, value);
 289                 use_format = fmt;
 290                 return 0;
 291         }
 292
 293         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 294                 fmtname = "openpgp";
 295
 296         if (!strcmp(var, "gpg.x509.program"))
 297                 fmtname = "x509";
 298
 299         if (fmtname) {
 300                 fmt = get_format_by_name(fmtname);
 301                 return git_config_string(&fmt->program, var, value);
 302         }
 303
 304         return 0;
 305 }
 306
 307 const char *get_signing_key(void)
 308 {
 309         if (configured_signing_key)
 310                 return configured_signing_key;
 311         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 312 }
 313
 314 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 315 {
 316         struct child_process gpg = CHILD_PROCESS_INIT;
 317         int ret;
 318         size_t i, j, bottom;
 319         struct strbuf gpg_status = STRBUF_INIT;
 320
 321         argv_array_pushl(&gpg.args,
 322                          use_format->program,
 323                          "--status-fd=2",
 324                          "-bsau", signing_key,
 325                          NULL);
 326
 327         bottom = signature->len;
 328
 329         /*
 330          * When the username signingkey is bad, program could be terminated
 331          * because gpg exits without reading and then write gets SIGPIPE.
 332          */
 333         sigchain_push(SIGPIPE, SIG_IGN);
 334         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 335                            signature, 1024, &gpg_status, 0);
 336         sigchain_pop(SIGPIPE);
 337
 338         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 339         strbuf_release(&gpg_status);
 340         if (ret)
 341                 return error(_("gpg failed to sign the data"));
 342
 343         /* Strip CR from the line endings, in case we are on Windows. */
 344         for (i = j = bottom; i < signature->len; i++)
 345                 if (signature->buf[i] != '\r') {
 346                         if (i != j)
 347                                 signature->buf[j] = signature->buf[i];
 348                         j++;
 349                 }
 350         strbuf_setlen(signature, j);
 351
 352         return 0;
 353 }
 354
 355 int verify_signed_buffer(const char *payload, size_t payload_size,
 356                          const char *signature, size_t signature_size,
 357                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 358 {
 359         struct child_process gpg = CHILD_PROCESS_INIT;
 360         struct gpg_format *fmt;
 361         struct tempfile *temp;
 362         int ret;
 363         struct strbuf buf = STRBUF_INIT;
 364
 365         temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 366         if (!temp)
 367                 return error_errno(_("could not create temporary file"));
 368         if (write_in_full(temp->fd, signature, signature_size) < 0 ||
 369             close_tempfile_gently(temp) < 0) {
 370                 error_errno(_("failed writing detached signature to '%s'"),
 371                             temp->filename.buf);
 372                 delete_tempfile(&temp);
 373                 return -1;
 374         }
 375
 376         fmt = get_format_by_sig(signature);
 377         if (!fmt)
 378                 BUG("bad signature '%s'", signature);
 379
 380         argv_array_push(&gpg.args, fmt->program);
 381         argv_array_pushv(&gpg.args, fmt->verify_args);
 382         argv_array_pushl(&gpg.args,
 383                          "--status-fd=1",
 384                          "--verify", temp->filename.buf, "-",
 385                          NULL);
 386
 387         if (!gpg_status)
 388                 gpg_status = &buf;
 389
 390         sigchain_push(SIGPIPE, SIG_IGN);
 391         ret = pipe_command(&gpg, payload, payload_size,
 392                            gpg_status, 0, gpg_output, 0);
 393         sigchain_pop(SIGPIPE);
 394
 395         delete_tempfile(&temp);
 396
 397         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
 398         strbuf_release(&buf); /* no matter it was used or not */
 399
 400         return ret;
 401 }