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 parse_gpg_output(struct signature_check *sigc)
 109 {
 110         const char *buf = sigc->gpg_status;
 111         const char *line, *next;
 112         int i, j;
 113         int seen_exclusive_status = 0;
 114
 115         /* Iterate over all lines */
 116         for (line = buf; *line; line = strchrnul(line+1, '\n')) {
 117                 while (*line == '\n')
 118                         line++;
 119                 if (!*line)
 120                         break;
 121
 122                 /* Skip lines that don't start with GNUPG status */
 123                 if (!skip_prefix(line, "[GNUPG:] ", &line))
 124                         continue;
 125
 126                 /* Iterate over all search strings */
 127                 for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
 128                         if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
 129                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
 130                                         if (seen_exclusive_status++)
 131                                                 goto found_duplicate_status;
 132                                 }
 133
 134                                 if (sigcheck_gpg_status[i].result)
 135                                         sigc->result = sigcheck_gpg_status[i].result;
 136                                 /* Do we have key information? */
 137                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_KEYID) {
 138                                         next = strchrnul(line, ' ');
 139                                         free(sigc->key);
 140                                         sigc->key = xmemdupz(line, next - line);
 141                                         /* Do we have signer information? */
 142                                         if (*next && (sigcheck_gpg_status[i].flags & GPG_STATUS_UID)) {
 143                                                 line = next + 1;
 144                                                 next = strchrnul(line, '\n');
 145                                                 free(sigc->signer);
 146                                                 sigc->signer = xmemdupz(line, next - line);
 147                                         }
 148                                 }
 149                                 /* Do we have fingerprint? */
 150                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
 151                                         next = strchrnul(line, ' ');
 152                                         free(sigc->fingerprint);
 153                                         sigc->fingerprint = xmemdupz(line, next - line);
 154
 155                                         /* Skip interim fields */
 156                                         for (j = 9; j > 0; j--) {
 157                                                 if (!*next)
 158                                                         break;
 159                                                 line = next + 1;
 160                                                 next = strchrnul(line, ' ');
 161                                         }
 162
 163                                         next = strchrnul(line, '\n');
 164                                         free(sigc->primary_key_fingerprint);
 165                                         sigc->primary_key_fingerprint = xmemdupz(line, next - line);
 166                                 }
 167
 168                                 break;
 169                         }
 170                 }
 171         }
 172         return;
 173
 174 found_duplicate_status:
 175         /*
 176          * GOODSIG, BADSIG etc. can occur only once for each signature.
 177          * Therefore, if we had more than one then we're dealing with multiple
 178          * signatures.  We don't support them currently, and they're rather
 179          * hard to create, so something is likely fishy and we should reject
 180          * them altogether.
 181          */
 182         sigc->result = 'E';
 183         /* Clear partial data to avoid confusion */
 184         FREE_AND_NULL(sigc->primary_key_fingerprint);
 185         FREE_AND_NULL(sigc->fingerprint);
 186         FREE_AND_NULL(sigc->signer);
 187         FREE_AND_NULL(sigc->key);
 188 }
 189
 190 int check_signature(const char *payload, size_t plen, const char *signature,
 191         size_t slen, struct signature_check *sigc)
 192 {
 193         struct strbuf gpg_output = STRBUF_INIT;
 194         struct strbuf gpg_status = STRBUF_INIT;
 195         int status;
 196
 197         sigc->result = 'N';
 198
 199         status = verify_signed_buffer(payload, plen, signature, slen,
 200                                       &gpg_output, &gpg_status);
 201         if (status && !gpg_output.len)
 202                 goto out;
 203         sigc->payload = xmemdupz(payload, plen);
 204         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
 205         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
 206         parse_gpg_output(sigc);
 207         status |= sigc->result != 'G' && sigc->result != 'U';
 208
 209  out:
 210         strbuf_release(&gpg_status);
 211         strbuf_release(&gpg_output);
 212
 213         return !!status;
 214 }
 215
 216 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 217 {
 218         const char *output = flags & GPG_VERIFY_RAW ?
 219                 sigc->gpg_status : sigc->gpg_output;
 220
 221         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 222                 fputs(sigc->payload, stdout);
 223
 224         if (output)
 225                 fputs(output, stderr);
 226 }
 227
 228 size_t parse_signature(const char *buf, size_t size)
 229 {
 230         size_t len = 0;
 231         size_t match = size;
 232         while (len < size) {
 233                 const char *eol;
 234
 235                 if (get_format_by_sig(buf + len))
 236                         match = len;
 237
 238                 eol = memchr(buf + len, '\n', size - len);
 239                 len += eol ? eol - (buf + len) + 1 : size - len;
 240         }
 241         return match;
 242 }
 243
 244 void set_signing_key(const char *key)
 245 {
 246         free(configured_signing_key);
 247         configured_signing_key = xstrdup(key);
 248 }
 249
 250 int git_gpg_config(const char *var, const char *value, void *cb)
 251 {
 252         struct gpg_format *fmt = NULL;
 253         char *fmtname = NULL;
 254
 255         if (!strcmp(var, "user.signingkey")) {
 256                 if (!value)
 257                         return config_error_nonbool(var);
 258                 set_signing_key(value);
 259                 return 0;
 260         }
 261
 262         if (!strcmp(var, "gpg.format")) {
 263                 if (!value)
 264                         return config_error_nonbool(var);
 265                 fmt = get_format_by_name(value);
 266                 if (!fmt)
 267                         return error("unsupported value for %s: %s",
 268                                      var, value);
 269                 use_format = fmt;
 270                 return 0;
 271         }
 272
 273         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 274                 fmtname = "openpgp";
 275
 276         if (!strcmp(var, "gpg.x509.program"))
 277                 fmtname = "x509";
 278
 279         if (fmtname) {
 280                 fmt = get_format_by_name(fmtname);
 281                 return git_config_string(&fmt->program, var, value);
 282         }
 283
 284         return 0;
 285 }
 286
 287 const char *get_signing_key(void)
 288 {
 289         if (configured_signing_key)
 290                 return configured_signing_key;
 291         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 292 }
 293
 294 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 295 {
 296         struct child_process gpg = CHILD_PROCESS_INIT;
 297         int ret;
 298         size_t i, j, bottom;
 299         struct strbuf gpg_status = STRBUF_INIT;
 300
 301         argv_array_pushl(&gpg.args,
 302                          use_format->program,
 303                          "--status-fd=2",
 304                          "-bsau", signing_key,
 305                          NULL);
 306
 307         bottom = signature->len;
 308
 309         /*
 310          * When the username signingkey is bad, program could be terminated
 311          * because gpg exits without reading and then write gets SIGPIPE.
 312          */
 313         sigchain_push(SIGPIPE, SIG_IGN);
 314         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 315                            signature, 1024, &gpg_status, 0);
 316         sigchain_pop(SIGPIPE);
 317
 318         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 319         strbuf_release(&gpg_status);
 320         if (ret)
 321                 return error(_("gpg failed to sign the data"));
 322
 323         /* Strip CR from the line endings, in case we are on Windows. */
 324         for (i = j = bottom; i < signature->len; i++)
 325                 if (signature->buf[i] != '\r') {
 326                         if (i != j)
 327                                 signature->buf[j] = signature->buf[i];
 328                         j++;
 329                 }
 330         strbuf_setlen(signature, j);
 331
 332         return 0;
 333 }
 334
 335 int verify_signed_buffer(const char *payload, size_t payload_size,
 336                          const char *signature, size_t signature_size,
 337                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 338 {
 339         struct child_process gpg = CHILD_PROCESS_INIT;
 340         struct gpg_format *fmt;
 341         struct tempfile *temp;
 342         int ret;
 343         struct strbuf buf = STRBUF_INIT;
 344
 345         temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 346         if (!temp)
 347                 return error_errno(_("could not create temporary file"));
 348         if (write_in_full(temp->fd, signature, signature_size) < 0 ||
 349             close_tempfile_gently(temp) < 0) {
 350                 error_errno(_("failed writing detached signature to '%s'"),
 351                             temp->filename.buf);
 352                 delete_tempfile(&temp);
 353                 return -1;
 354         }
 355
 356         fmt = get_format_by_sig(signature);
 357         if (!fmt)
 358                 BUG("bad signature '%s'", signature);
 359
 360         argv_array_push(&gpg.args, fmt->program);
 361         argv_array_pushv(&gpg.args, fmt->verify_args);
 362         argv_array_pushl(&gpg.args,
 363                          "--status-fd=1",
 364                          "--verify", temp->filename.buf, "-",
 365                          NULL);
 366
 367         if (!gpg_status)
 368                 gpg_status = &buf;
 369
 370         sigchain_push(SIGPIPE, SIG_IGN);
 371         ret = pipe_command(&gpg, payload, payload_size,
 372                            gpg_status, 0, gpg_output, 0);
 373         sigchain_pop(SIGPIPE);
 374
 375         delete_tempfile(&temp);
 376
 377         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
 378         strbuf_release(&buf); /* no matter it was used or not */
 379
 380         return ret;
 381 }