ucert.c

   1 /*
   2  * Copyright (C) 2018 Daniel Golle <daniel@makrotopia.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 3
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #define _GNU_SOURCE
  15
  16 #include <fcntl.h>
  17 #include <dlfcn.h>
  18 #include <stdio.h>
  19 #include <stdbool.h>
  20 #include <stdlib.h>
  21 #include <string.h>
  22 #include <getopt.h>
  23 #include <stdint.h>
  24 #include <unistd.h>
  25 #include <inttypes.h>
  26 #include <sys/stat.h>
  27 #include <sys/wait.h>
  28
  29 #include <json-c/json.h>
  30 #include <libubox/blob.h>
  31 #include <libubox/utils.h>
  32 #include <libubox/list.h>
  33 #include <libubox/vlist.h>
  34 #include <libubox/blobmsg_json.h>
  35
  36 #include "usign.h"
  37
  38 #define CERT_BUF_LEN 4096
  39
  40 static enum {
  41         CMD_APPEND,
  42         CMD_DUMP,
  43         CMD_ISSUE,
  44         CMD_REVOKE,
  45         CMD_VERIFY,
  46         CMD_NONE,
  47 } cmd = CMD_NONE;
  48
  49 static bool quiet;
  50
  51 enum cert_attr {
  52         CERT_ATTR_SIGNATURE,
  53         CERT_ATTR_PAYLOAD,
  54         CERT_ATTR_MAX
  55 };
  56
  57 static const struct blob_attr_info cert_policy[CERT_ATTR_MAX] = {
  58         [CERT_ATTR_SIGNATURE] = { .type = BLOB_ATTR_BINARY },
  59         [CERT_ATTR_PAYLOAD] = { .type = BLOB_ATTR_NESTED },
  60 };
  61
  62 enum cert_cont_attr {
  63         CERT_CT_ATTR_PAYLOAD,
  64         CERT_CT_ATTR_MAX
  65 };
  66
  67 static const struct blobmsg_policy cert_cont_policy[CERT_CT_ATTR_MAX] = {
  68         [CERT_CT_ATTR_PAYLOAD] = { .name = "ucert", .type = BLOBMSG_TYPE_TABLE },
  69 };
  70
  71 enum cert_payload_attr {
  72         CERT_PL_ATTR_CERTTYPE,
  73         CERT_PL_ATTR_CERTID,
  74         CERT_PL_ATTR_VALIDFROMTIME,
  75         CERT_PL_ATTR_EXPIRETIME,
  76         CERT_PL_ATTR_PUBKEY,
  77         CERT_PL_ATTR_KEY_FINGERPRINT,
  78         CERT_PL_ATTR_MAX
  79 };
  80
  81 enum certtype_id {
  82         CERTTYPE_UNSPEC,
  83         CERTTYPE_AUTH,
  84         CERTTYPE_REVOKE
  85 };
  86
  87 static const struct blobmsg_policy cert_payload_policy[CERT_PL_ATTR_MAX] = {
  88         [CERT_PL_ATTR_CERTTYPE] = { .name = "certtype", .type = BLOBMSG_TYPE_INT32 },
  89         [CERT_PL_ATTR_CERTID] = { .name = "certid", .type = BLOBMSG_TYPE_INT32 },
  90         [CERT_PL_ATTR_VALIDFROMTIME] = { .name = "validfrom", .type = BLOBMSG_TYPE_INT64 },
  91         [CERT_PL_ATTR_EXPIRETIME] = { .name = "expiresat", .type = BLOBMSG_TYPE_INT64 },
  92         [CERT_PL_ATTR_PUBKEY] = { .name = "pubkey", .type = BLOBMSG_TYPE_STRING },
  93         [CERT_PL_ATTR_KEY_FINGERPRINT] = { .name = "fingerprint", .type = BLOBMSG_TYPE_STRING },
  94 };
  95
  96 struct cert_object {
  97         struct list_head list;
  98         struct blob_attr *cert[CERT_ATTR_MAX];
  99 };
 100
 101 static int write_file(const char *filename, void *buf, size_t len, bool append) {
 102         FILE *f;
 103         size_t outlen;
 104
 105         f = fopen(filename, append?"a":"w");
 106         if (!f)
 107                 return 1;
 108
 109         outlen = fwrite(buf, 1, len, f);
 110         fclose(f);
 111         return (outlen == len);
 112 }
 113
 114 static int cert_load(const char *certfile, struct list_head *chain) {
 115         FILE *f;
 116         struct blob_attr *certtb[CERT_ATTR_MAX];
 117         struct blob_attr *bufpt;
 118         struct cert_object *cobj;
 119         char filebuf[CERT_BUF_LEN];
 120         int ret = 0, pret = 0;
 121         int len, pos = 0;
 122
 123         f = fopen(certfile, "r");
 124         if (!f)
 125                 return 1;
 126
 127         len = fread(&filebuf, 1, CERT_BUF_LEN - 1, f);
 128         if (len < 64)
 129                 return 1;
 130
 131         ret = ferror(f) || !feof(f);
 132         fclose(f);
 133         if (ret)
 134                 return 1;
 135
 136         bufpt = (struct blob_attr *)filebuf;
 137         do {
 138                 pret = blob_parse(bufpt, certtb, cert_policy, CERT_ATTR_MAX);
 139                 if (pret <= 0)
 140                         /* no attributes found */
 141                         break;
 142
 143                 if (pos + blob_pad_len(bufpt) > len)
 144                         /* blob exceeds filebuffer */
 145                         break;
 146                 else
 147                         pos += blob_pad_len(bufpt);
 148
 149                 cobj = calloc(1, sizeof(*cobj));
 150                 memcpy(cobj->cert, &certtb, sizeof(certtb));
 151                 list_add_tail(&cobj->list, chain);
 152                 ret += pret;
 153                 bufpt = blob_next(bufpt);
 154         /* repeat parsing while there is still enough remaining data in buffer */
 155         } while(len > pos + sizeof(struct blob_attr));
 156
 157         return (ret <= 0);
 158 }
 159
 160 static int cert_append(const char *certfile, const char *sigfile) {
 161         FILE *fs;
 162         char filebuf[CERT_BUF_LEN];
 163         struct blob_buf sigbuf;
 164         int len;
 165         int ret;
 166
 167         fs = fopen(sigfile, "r");
 168         if (!fs)
 169                 return 1;
 170
 171         len = fread(&filebuf, 1, CERT_BUF_LEN - 1, fs);
 172         ret = ferror(fs) || !feof(fs) || (len < 64);
 173         fclose(fs);
 174         if (ret)
 175                 return 1;
 176
 177         blob_buf_init(&sigbuf, 0);
 178         blob_put(&sigbuf, CERT_ATTR_SIGNATURE, filebuf, len);
 179         ret = write_file(certfile, sigbuf.head, blob_raw_len(sigbuf.head), true);
 180         blob_buf_free(&sigbuf);
 181         return ret;
 182 }
 183
 184 static int cert_verify_blob(struct blob_attr *cert[CERT_ATTR_MAX],
 185                        const char *pubkeyfile, const char *pubkeydir) {
 186         int i;
 187         char msgfname[256], sigfname[256];
 188         int ret;
 189         char tmpdir[] = "/tmp/ucert-XXXXXX";
 190
 191         if (mkdtemp(tmpdir) == NULL)
 192                 return errno;
 193
 194         snprintf(msgfname, sizeof(msgfname) - 1, "%s/%s", tmpdir, "payload");
 195         snprintf(sigfname, sizeof(sigfname) - 1, "%s/%s", tmpdir, "payload.sig");
 196
 197         for (i = 0; i < CERT_ATTR_MAX; i++) {
 198                 struct blob_attr *v = cert[i];
 199
 200                 if (!v)
 201                         break;
 202
 203                 switch(cert_policy[i].type) {
 204                 case BLOB_ATTR_BINARY:
 205                         write_file(sigfname, blob_data(v), blob_len(v), false);
 206                         break;
 207                 case BLOB_ATTR_NESTED:
 208                         write_file(msgfname, blob_data(v), blob_len(v), false);
 209                         break;
 210                 }
 211         }
 212
 213         ret = usign_v(msgfname, pubkeyfile, pubkeydir, sigfname, quiet);
 214
 215         unlink(msgfname);
 216         unlink(sigfname);
 217         rmdir(tmpdir);
 218
 219         return ret;
 220 }
 221
 222 static int chain_verify(const char *msgfile, const char *pubkeyfile,
 223                         const char *pubkeydir, struct list_head *chain) {
 224         struct cert_object *cobj;
 225         struct blob_attr *containertb[CERT_CT_ATTR_MAX];
 226         struct blob_attr *payloadtb[CERT_PL_ATTR_MAX];
 227         char tmpdir[] = "/tmp/ucert-XXXXXX";
 228         char chainedpubkey[256] = {0};
 229         char extsigfile[256] = {0};
 230         int ret = 1;
 231         int checkmsg = 0;
 232
 233         if (mkdtemp(tmpdir) == NULL)
 234                 return errno;
 235
 236         if (msgfile)
 237                 checkmsg = -1;
 238
 239         list_for_each_entry(cobj, chain, list) {
 240                 /* blob has payload, verify that using signature */
 241                 if (cobj->cert[CERT_ATTR_PAYLOAD]) {
 242                         struct timeval tv;
 243                         uint64_t validfrom;
 244                         uint64_t expiresat;
 245                         uint32_t certtype;
 246
 247                         ret = cert_verify_blob(cobj->cert, chainedpubkey[0]?chainedpubkey:pubkeyfile, pubkeydir);
 248                         if (ret)
 249                                 goto clean_and_return;
 250
 251                         blobmsg_parse(cert_cont_policy,
 252                                       ARRAY_SIZE(cert_cont_policy),
 253                                       containertb,
 254                                       blob_data(cobj->cert[CERT_ATTR_PAYLOAD]),
 255                                       blob_len(cobj->cert[CERT_ATTR_PAYLOAD]));
 256                         if (!containertb[CERT_CT_ATTR_PAYLOAD]) {
 257                                 ret = 1;
 258                                 fprintf(stderr, "no ucert in signed payload\n");
 259                                 goto clean_and_return;
 260                         }
 261                         blobmsg_parse(cert_payload_policy,
 262                                       ARRAY_SIZE(cert_payload_policy),
 263                                       payloadtb,
 264                                       blobmsg_data(containertb[CERT_CT_ATTR_PAYLOAD]),
 265                                       blobmsg_data_len(containertb[CERT_CT_ATTR_PAYLOAD]));
 266
 267                         if (!payloadtb[CERT_PL_ATTR_CERTTYPE] ||
 268                             !payloadtb[CERT_PL_ATTR_VALIDFROMTIME] ||
 269                             !payloadtb[CERT_PL_ATTR_EXPIRETIME] ||
 270                             !payloadtb[CERT_PL_ATTR_PUBKEY]) {
 271                                 ret = 1;
 272                                 fprintf(stderr, "missing mandatory ucert attributes\n");
 273                                 goto clean_and_return;
 274                         }
 275                         certtype = blobmsg_get_u32(payloadtb[CERT_PL_ATTR_CERTTYPE]);
 276                         validfrom = blobmsg_get_u64(payloadtb[CERT_PL_ATTR_VALIDFROMTIME]);
 277                         expiresat = blobmsg_get_u64(payloadtb[CERT_PL_ATTR_EXPIRETIME]);
 278
 279                         if (certtype != CERTTYPE_AUTH) {
 280                                 ret = 2;
 281                                 fprintf(stderr, "wrong certificate type\n");
 282                                 goto clean_and_return;
 283                         }
 284
 285                         gettimeofday(&tv, NULL);
 286                         if (tv.tv_sec < validfrom ||
 287                             tv.tv_sec >= expiresat) {
 288                                 ret = 3;
 289                                 fprintf(stderr, "certificate expired\n");
 290                                 goto clean_and_return;
 291                         }
 292
 293                         snprintf(chainedpubkey, sizeof(chainedpubkey) - 1, "%s/%s", tmpdir, "chained-pubkey");
 294                         write_file(chainedpubkey,
 295                                    blobmsg_data(payloadtb[CERT_PL_ATTR_PUBKEY]),
 296                                    blobmsg_data_len(payloadtb[CERT_PL_ATTR_PUBKEY]),
 297                                    false);
 298                 } else {
 299                 /* blob doesn't have payload, verify message using signature */
 300                         if (msgfile) {
 301                                 snprintf(extsigfile, sizeof(extsigfile) - 1, "%s/%s", tmpdir, "ext-sig");
 302                                 write_file(extsigfile,
 303                                            blob_data(cobj->cert[CERT_ATTR_SIGNATURE]),
 304                                            blob_len(cobj->cert[CERT_ATTR_SIGNATURE]),
 305                                            false);
 306                                 checkmsg = ret = usign_v(msgfile,
 307                                               chainedpubkey[0]?chainedpubkey:pubkeyfile,
 308                                               pubkeydir, extsigfile, quiet);
 309                                 unlink(extsigfile);
 310                         } else {
 311                                 fprintf(stderr, "stray trailing signature without anything to verify!\n");
 312                                 ret = 1;
 313                         };
 314                 }
 315         }
 316
 317         if (checkmsg == -1)
 318                 fprintf(stderr, "missing signature to verify message!\n");
 319
 320 clean_and_return:
 321         if (chainedpubkey[0])
 322                 unlink(chainedpubkey);
 323         rmdir(tmpdir);
 324         return ret | checkmsg;
 325 }
 326
 327 static void cert_dump_blob(struct blob_attr *cert[CERT_ATTR_MAX]) {
 328         int i;
 329
 330         for (i = 0; i < CERT_ATTR_MAX; i++) {
 331                 struct blob_attr *v = cert[i];
 332
 333                 if (!v)
 334                         continue;
 335
 336                 switch(cert_policy[i].type) {
 337                 case BLOB_ATTR_BINARY:
 338                         fprintf(stdout, "signature:\n---\n%s---\n", (char *) blob_data(v));
 339                         break;
 340                 case BLOB_ATTR_NESTED:
 341                         fprintf(stdout, "payload:\n---\n%s\n---\n", blobmsg_format_json_indent(blob_data(v), false, 0));
 342                         break;
 343                 }
 344         }
 345 }
 346
 347 static int cert_dump(const char *certfile) {
 348         struct cert_object *cobj;
 349         static LIST_HEAD(certchain);
 350         unsigned int count = 0;
 351
 352         if (cert_load(certfile, &certchain)) {
 353                 fprintf(stderr, "cannot parse cert\n");
 354                 return 1;
 355         }
 356
 357         list_for_each_entry(cobj, &certchain, list) {
 358                 fprintf(stderr, "=== CHAIN ELEMENT %02u ===\n", ++count);
 359                 cert_dump_blob(cobj->cert);
 360                 fprintf(stderr, "========================\n");
 361         }
 362
 363         return 0;
 364 }
 365
 366 static int cert_issue(const char *certfile, const char *pubkeyfile, const char *seckeyfile) {
 367         struct blob_buf certbuf;
 368         struct blob_buf payloadbuf;
 369         struct timeval tv;
 370         struct stat st;
 371         int pklen, siglen;
 372         int revoker = 1;
 373         void *c;
 374         FILE *pkf, *sigf;
 375         char pkb[512];
 376         char sigb[512];
 377         char fname[256], sfname[256];
 378         char pkfp[17];
 379         char tmpdir[] = "/tmp/ucert-XXXXXX";
 380
 381         if (stat(certfile, &st) == 0) {
 382                 fprintf(stderr, "certfile %s exists, won't overwrite.\n", certfile);
 383                 return -1;
 384         }
 385
 386         pkf = fopen(pubkeyfile, "r");
 387         if (!pkf)
 388                 return -1;
 389
 390         pklen = fread(pkb, 1, 512, pkf);
 391         pkb[pklen] = '\0';
 392
 393         if (pklen < 32)
 394                 return -1;
 395
 396         fclose(pkf);
 397
 398         if (usign_f_pubkey(pkfp, pubkeyfile))
 399                 return -1;
 400
 401         gettimeofday(&tv, NULL);
 402
 403         if (mkdtemp(tmpdir) == NULL)
 404                 return errno;
 405
 406         while (revoker >= 0) {
 407                 blob_buf_init(&payloadbuf, 0);
 408                 c = blobmsg_open_table(&payloadbuf, "ucert");
 409                 blobmsg_add_u32(&payloadbuf, "certtype", revoker?CERTTYPE_REVOKE:CERTTYPE_AUTH);
 410                 blobmsg_add_u64(&payloadbuf, "validfrom", tv.tv_sec);
 411                 if (!revoker) {
 412                         blobmsg_add_u64(&payloadbuf, "expiresat", tv.tv_sec + 60 * 60 * 24 * 365);
 413                         blobmsg_add_string(&payloadbuf, "pubkey", pkb);
 414                 } else {
 415                         blobmsg_add_string(&payloadbuf, "fingerprint", pkfp);
 416                 }
 417
 418                 blobmsg_close_table(&payloadbuf, c);
 419
 420                 snprintf(fname, sizeof(fname) - 1, "%s/%s", tmpdir, revoker?"revoker":"payload");
 421                 write_file(fname, blob_data(payloadbuf.head), blob_len(payloadbuf.head), false);
 422
 423                 snprintf(sfname, sizeof(sfname) - 1, "%s/%s", tmpdir, revoker?"revoker.sig":"payload.sig");
 424                 if (usign_s(fname, seckeyfile, sfname, quiet))
 425                         return 1;
 426
 427                 sigf = fopen(sfname, "r");
 428                 if (!sigf)
 429                         return 1;
 430
 431                 siglen = fread(sigb, 1, 1024, sigf);
 432                 if (siglen < 1)
 433                         return 1;
 434
 435                 sigb[siglen] = '\0';
 436                 fclose(sigf);
 437
 438                 unlink(fname);
 439                 unlink(sfname);
 440
 441                 blob_buf_init(&certbuf, 0);
 442                 blob_put(&certbuf, CERT_ATTR_SIGNATURE, sigb, siglen);
 443                 blob_put(&certbuf, CERT_ATTR_PAYLOAD, blob_data(payloadbuf.head), blob_len(payloadbuf.head));
 444                 snprintf(fname, sizeof(fname) - 1, "%s%s", certfile, revoker?".revoke":"");
 445                 write_file(fname, certbuf.head, blob_raw_len(certbuf.head), false);
 446                 blob_buf_free(&certbuf);
 447                 blob_buf_free(&payloadbuf);
 448
 449                 revoker--;
 450         }
 451
 452         rmdir(tmpdir);
 453
 454         return 0;
 455 }
 456
 457 static int cert_process_revoker(const char *certfile) {
 458         fprintf(stderr, "not implemented\n");
 459         return 1;
 460 }
 461
 462 static int cert_verify(const char *certfile, const char *pubkeyfile, const char *pubkeydir, const char *msgfile) {
 463         static LIST_HEAD(certchain);
 464
 465         if (cert_load(certfile, &certchain)) {
 466                 fprintf(stderr, "cannot parse cert\n");
 467                 return 1;
 468         }
 469
 470         return chain_verify(msgfile, pubkeyfile, pubkeydir, &certchain);
 471 }
 472
 473 static int usage(const char *cmd)
 474 {
 475         fprintf(stderr,
 476                 "Usage: %s <command> <options>\n"
 477                 "Commands:\n"
 478                 "  -A:                  append signature (needs -c and -x)\n"
 479                 "  -D:                  dump\n"
 480                 "  -I:                  issue cert and revoker (needs -c and -p and -s)\n"
 481                 "  -R:                  process revoker certificate (needs -c)\n"
 482                 "  -V:                  verify (needs -c and -p|-P)\n"
 483                 "Options:\n"
 484                 "  -c <file>:           certificate file\n"
 485                 "  -m <file>:           message file (verify only)\n"
 486                 "  -p <file>:           public key file\n"
 487                 "  -P <path>:           public key directory (verify only)\n"
 488                 "  -q:                  quiet (do not print verification result, use return code only)\n"
 489                 "  -s <file>:           secret key file (issue only)\n"
 490                 "  -x <file>:           signature file\n"
 491                 "\n",
 492                 cmd);
 493         return 1;
 494 }
 495
 496 int main(int argc, char *argv[]) {
 497         int ch;
 498         const char *msgfile = NULL;
 499         const char *sigfile = NULL;
 500         const char *pubkeyfile = NULL;
 501         const char *pubkeydir = NULL;
 502         const char *certfile = NULL;
 503         const char *seckeyfile = NULL;
 504
 505         quiet = false;
 506         while ((ch = getopt(argc, argv, "ADIRVc:m:p:P:qs:x:")) != -1) {
 507                 switch (ch) {
 508                 case 'A':
 509                         cmd = CMD_APPEND;
 510                         break;
 511                 case 'D':
 512                         cmd = CMD_DUMP;
 513                         break;
 514                 case 'I':
 515                         cmd = CMD_ISSUE;
 516                         break;
 517                 case 'R':
 518                         cmd = CMD_REVOKE;
 519                         break;
 520                 case 'V':
 521                         cmd = CMD_VERIFY;
 522                         break;
 523                 case 'c':
 524                         certfile = optarg;
 525                         break;
 526                 case 'm':
 527                         msgfile = optarg;
 528                         break;
 529                 case 'p':
 530                         pubkeyfile = optarg;
 531                         break;
 532                 case 'P':
 533                         pubkeydir = optarg;
 534                         break;
 535                 case 'q':
 536                         quiet = true;
 537                         break;
 538                 case 's':
 539                         seckeyfile = optarg;
 540                         break;
 541                 case 'x':
 542                         sigfile = optarg;
 543                         break;
 544                 default:
 545                         return usage(argv[0]);
 546                 }
 547         }
 548
 549         switch (cmd) {
 550         case CMD_APPEND:
 551                 if (certfile && sigfile)
 552                         return cert_append(certfile, sigfile);
 553                 else
 554                         return usage(argv[0]);
 555         case CMD_DUMP:
 556                 if (certfile)
 557                         return cert_dump(certfile);
 558                 else
 559                         return usage(argv[0]);
 560         case CMD_ISSUE:
 561                 if (certfile && pubkeyfile && seckeyfile)
 562                         return cert_issue(certfile, pubkeyfile, seckeyfile);
 563                 else
 564                         return usage(argv[0]);
 565         case CMD_REVOKE:
 566                 if (certfile)
 567                         return cert_process_revoker(certfile);
 568                 else
 569                         return usage(argv[0]);
 570         case CMD_VERIFY:
 571                 if (certfile && (pubkeyfile || pubkeydir))
 572                         return cert_verify(certfile, pubkeyfile, pubkeydir, msgfile);
 573                 else
 574                         return usage(argv[0]);
 575         case CMD_NONE:
 576                 return usage(argv[0]);
 577         }
 578
 579         /* unreachable */
 580         return usage(argv[0]);
 581 }