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 }
  78
  79 /* An exclusive status -- only one of them can appear in output */
  80 #define GPG_STATUS_EXCLUSIVE    (1<<0)
  81 /* The status includes key identifier */
  82 #define GPG_STATUS_KEYID        (1<<1)
  83 /* The status includes user identifier */
  84 #define GPG_STATUS_UID          (1<<2)
  85 /* The status includes key fingerprints */
  86 #define GPG_STATUS_FINGERPRINT  (1<<3)
  87
  88 /* Short-hand for standard exclusive *SIG status with keyid & UID */
  89 #define GPG_STATUS_STDSIG       (GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID|GPG_STATUS_UID)
  90
  91 static struct {
  92         char result;
  93         const char *check;
  94         unsigned int flags;
  95 } sigcheck_gpg_status[] = {
  96         { 'G', "GOODSIG ", GPG_STATUS_STDSIG },
  97         { 'B', "BADSIG ", GPG_STATUS_STDSIG },
  98         { 'U', "TRUST_NEVER", 0 },
  99         { 'U', "TRUST_UNDEFINED", 0 },
 100         { 'E', "ERRSIG ", GPG_STATUS_EXCLUSIVE|GPG_STATUS_KEYID },
 101         { 'X', "EXPSIG ", GPG_STATUS_STDSIG },
 102         { 'Y', "EXPKEYSIG ", GPG_STATUS_STDSIG },
 103         { 'R', "REVKEYSIG ", GPG_STATUS_STDSIG },
 104         { 0, "VALIDSIG ", GPG_STATUS_FINGERPRINT },
 105 };
 106
 107 static void parse_gpg_output(struct signature_check *sigc)
 108 {
 109         const char *buf = sigc->gpg_status;
 110         const char *line, *next;
 111         int i;
 112         int seen_exclusive_status = 0;
 113
 114         /* Iterate over all lines */
 115         for (line = buf; *line; line = strchrnul(line+1, '\n')) {
 116                 while (*line == '\n')
 117                         line++;
 118                 /* Skip lines that don't start with GNUPG status */
 119                 if (!skip_prefix(line, "[GNUPG:] ", &line))
 120                         continue;
 121
 122                 /* Iterate over all search strings */
 123                 for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
 124                         if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
 125                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
 126                                         if (++seen_exclusive_status > 1)
 127                                                 goto found_duplicate_status;
 128                                 }
 129
 130                                 if (sigcheck_gpg_status[i].result)
 131                                         sigc->result = sigcheck_gpg_status[i].result;
 132                                 /* Do we have key information? */
 133                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_KEYID) {
 134                                         next = strchrnul(line, ' ');
 135                                         free(sigc->key);
 136                                         sigc->key = xmemdupz(line, next - line);
 137                                         /* Do we have signer information? */
 138                                         if (*next && (sigcheck_gpg_status[i].flags & GPG_STATUS_UID)) {
 139                                                 line = next + 1;
 140                                                 next = strchrnul(line, '\n');
 141                                                 free(sigc->signer);
 142                                                 sigc->signer = xmemdupz(line, next - line);
 143                                         }
 144                                 }
 145                                 /* Do we have fingerprint? */
 146                                 if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
 147                                         next = strchrnul(line, ' ');
 148                                         free(sigc->fingerprint);
 149                                         sigc->fingerprint = xmemdupz(line, next - line);
 150                                 }
 151
 152                                 break;
 153                         }
 154                 }
 155         }
 156         return;
 157
 158 found_duplicate_status:
 159         /*
 160          * GOODSIG, BADSIG etc. can occur only once for each signature.
 161          * Therefore, if we had more than one then we're dealing with multiple
 162          * signatures.  We don't support them currently, and they're rather
 163          * hard to create, so something is likely fishy and we should reject
 164          * them altogether.
 165          */
 166         sigc->result = 'E';
 167         /* Clear partial data to avoid confusion */
 168         FREE_AND_NULL(sigc->fingerprint);
 169         FREE_AND_NULL(sigc->signer);
 170         FREE_AND_NULL(sigc->key);
 171 }
 172
 173 int check_signature(const char *payload, size_t plen, const char *signature,
 174         size_t slen, struct signature_check *sigc)
 175 {
 176         struct strbuf gpg_output = STRBUF_INIT;
 177         struct strbuf gpg_status = STRBUF_INIT;
 178         int status;
 179
 180         sigc->result = 'N';
 181
 182         status = verify_signed_buffer(payload, plen, signature, slen,
 183                                       &gpg_output, &gpg_status);
 184         if (status && !gpg_output.len)
 185                 goto out;
 186         sigc->payload = xmemdupz(payload, plen);
 187         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
 188         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
 189         parse_gpg_output(sigc);
 190         status |= sigc->result != 'G' && sigc->result != 'U';
 191
 192  out:
 193         strbuf_release(&gpg_status);
 194         strbuf_release(&gpg_output);
 195
 196         return !!status;
 197 }
 198
 199 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 200 {
 201         const char *output = flags & GPG_VERIFY_RAW ?
 202                 sigc->gpg_status : sigc->gpg_output;
 203
 204         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 205                 fputs(sigc->payload, stdout);
 206
 207         if (output)
 208                 fputs(output, stderr);
 209 }
 210
 211 size_t parse_signature(const char *buf, size_t size)
 212 {
 213         size_t len = 0;
 214         size_t match = size;
 215         while (len < size) {
 216                 const char *eol;
 217
 218                 if (get_format_by_sig(buf + len))
 219                         match = len;
 220
 221                 eol = memchr(buf + len, '\n', size - len);
 222                 len += eol ? eol - (buf + len) + 1 : size - len;
 223         }
 224         return match;
 225 }
 226
 227 void set_signing_key(const char *key)
 228 {
 229         free(configured_signing_key);
 230         configured_signing_key = xstrdup(key);
 231 }
 232
 233 int git_gpg_config(const char *var, const char *value, void *cb)
 234 {
 235         struct gpg_format *fmt = NULL;
 236         char *fmtname = NULL;
 237
 238         if (!strcmp(var, "user.signingkey")) {
 239                 if (!value)
 240                         return config_error_nonbool(var);
 241                 set_signing_key(value);
 242                 return 0;
 243         }
 244
 245         if (!strcmp(var, "gpg.format")) {
 246                 if (!value)
 247                         return config_error_nonbool(var);
 248                 fmt = get_format_by_name(value);
 249                 if (!fmt)
 250                         return error("unsupported value for %s: %s",
 251                                      var, value);
 252                 use_format = fmt;
 253                 return 0;
 254         }
 255
 256         if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
 257                 fmtname = "openpgp";
 258
 259         if (!strcmp(var, "gpg.x509.program"))
 260                 fmtname = "x509";
 261
 262         if (fmtname) {
 263                 fmt = get_format_by_name(fmtname);
 264                 return git_config_string(&fmt->program, var, value);
 265         }
 266
 267         return 0;
 268 }
 269
 270 const char *get_signing_key(void)
 271 {
 272         if (configured_signing_key)
 273                 return configured_signing_key;
 274         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 275 }
 276
 277 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 278 {
 279         struct child_process gpg = CHILD_PROCESS_INIT;
 280         int ret;
 281         size_t i, j, bottom;
 282         struct strbuf gpg_status = STRBUF_INIT;
 283
 284         argv_array_pushl(&gpg.args,
 285                          use_format->program,
 286                          "--status-fd=2",
 287                          "-bsau", signing_key,
 288                          NULL);
 289
 290         bottom = signature->len;
 291
 292         /*
 293          * When the username signingkey is bad, program could be terminated
 294          * because gpg exits without reading and then write gets SIGPIPE.
 295          */
 296         sigchain_push(SIGPIPE, SIG_IGN);
 297         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 298                            signature, 1024, &gpg_status, 0);
 299         sigchain_pop(SIGPIPE);
 300
 301         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 302         strbuf_release(&gpg_status);
 303         if (ret)
 304                 return error(_("gpg failed to sign the data"));
 305
 306         /* Strip CR from the line endings, in case we are on Windows. */
 307         for (i = j = bottom; i < signature->len; i++)
 308                 if (signature->buf[i] != '\r') {
 309                         if (i != j)
 310                                 signature->buf[j] = signature->buf[i];
 311                         j++;
 312                 }
 313         strbuf_setlen(signature, j);
 314
 315         return 0;
 316 }
 317
 318 int verify_signed_buffer(const char *payload, size_t payload_size,
 319                          const char *signature, size_t signature_size,
 320                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 321 {
 322         struct child_process gpg = CHILD_PROCESS_INIT;
 323         struct gpg_format *fmt;
 324         struct tempfile *temp;
 325         int ret;
 326         struct strbuf buf = STRBUF_INIT;
 327
 328         temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
 329         if (!temp)
 330                 return error_errno(_("could not create temporary file"));
 331         if (write_in_full(temp->fd, signature, signature_size) < 0 ||
 332             close_tempfile_gently(temp) < 0) {
 333                 error_errno(_("failed writing detached signature to '%s'"),
 334                             temp->filename.buf);
 335                 delete_tempfile(&temp);
 336                 return -1;
 337         }
 338
 339         fmt = get_format_by_sig(signature);
 340         if (!fmt)
 341                 BUG("bad signature '%s'", signature);
 342
 343         argv_array_push(&gpg.args, fmt->program);
 344         argv_array_pushv(&gpg.args, fmt->verify_args);
 345         argv_array_pushl(&gpg.args,
 346                          "--status-fd=1",
 347                          "--verify", temp->filename.buf, "-",
 348                          NULL);
 349
 350         if (!gpg_status)
 351                 gpg_status = &buf;
 352
 353         sigchain_push(SIGPIPE, SIG_IGN);
 354         ret = pipe_command(&gpg, payload, payload_size,
 355                            gpg_status, 0, gpg_output, 0);
 356         sigchain_pop(SIGPIPE);
 357
 358         delete_tempfile(&temp);
 359
 360         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
 361         strbuf_release(&buf); /* no matter it was used or not */
 362
 363         return ret;
 364 }