gcrypt.c

   1 /* Copyright (C) 2011 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
   2
   3 /** \file gcrypt.c Libgrcypt-based encryption/decryption routines. */
   4
   5 #include <regex.h>
   6 #include <gcrypt.h>
   7
   8 #include "para.h"
   9 #include "error.h"
  10 #include "string.h"
  11 #include "crypt.h"
  12 #include "crypt_backend.h"
  13 #include "fd.h"
  14 #include "base64.h"
  15
  16 //#define GCRYPT_DEBUG 1
  17
  18 #ifdef GCRYPT_DEBUG
  19 static void dump_buffer(const char *msg, unsigned char *buf, int len)
  20 {
  21         int i;
  22
  23         fprintf(stderr, "%s (%d bytes): ", msg, len);
  24         for (i = 0; i < len; i++)
  25                 fprintf(stderr, "%02x ", buf[i]);
  26         fprintf(stderr, "\n");
  27 }
  28 #else
  29 /** Empty. Define GCRYPT_DEBUG to dump buffers. */
  30 #define dump_buffer(a, b, c)
  31 #endif
  32
  33 void hash_function(const char *data, unsigned long len, unsigned char *hash)
  34 {
  35         gcry_error_t gret;
  36         gcry_md_hd_t handle;
  37         unsigned char *md;
  38
  39         gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
  40         assert(gret == 0);
  41         gcry_md_write(handle, data, (size_t)len);
  42         gcry_md_final(handle);
  43         md = gcry_md_read(handle, GCRY_MD_SHA1);
  44         assert(md);
  45         memcpy(hash, md, HASH_SIZE);
  46         gcry_md_close(handle);
  47 }
  48
  49 void get_random_bytes_or_die(unsigned char *buf, int num)
  50 {
  51         gcry_randomize(buf, (size_t)num, GCRY_STRONG_RANDOM);
  52 }
  53
  54 /*
  55  * This is called at the beginning of every program that uses libgcrypt. The
  56  * call to gcry_check_version() initializes the gcrypt library and checks that
  57  * we have at least the minimal required version.
  58  */
  59 void crypt_init(void)
  60 {
  61         const char *req_ver = "1.5.0";
  62         int seed;
  63
  64         if (!gcry_check_version(req_ver)) {
  65                 PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
  66                         req_ver, gcry_check_version(NULL));
  67                 exit(EXIT_FAILURE);
  68         }
  69
  70         /*
  71          * Allocate a pool of secure memory. This also drops privileges where
  72          * needed.
  73          */
  74         gcry_control(GCRYCTL_INIT_SECMEM, 65536, 0);
  75
  76         /* Tell Libgcrypt that initialization has completed. */
  77         gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
  78
  79         get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
  80         srandom(seed);
  81 }
  82
  83 void crypt_shutdown(void)
  84 {
  85         /*
  86          * WK does not see a way to apply a patch for the sake of Valgrind, so
  87          * as of 2018 libgrypt has no deinitialization routine to free the
  88          * resources on exit.
  89          */
  90 }
  91
  92 /** S-expression for the public part of an RSA key. */
  93 #define RSA_PUBKEY_SEXP "(public-key (rsa (n %m) (e %m)))"
  94 /** S-expression for a private RSA key. */
  95 #define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
  96 /** S-expression for decryption. */
  97 #define RSA_DECRYPT_SEXP "(enc-val(flags oaep)(rsa(a %m)))"
  98
  99 struct asymmetric_key {
 100         gcry_sexp_t sexp;
 101         int num_bytes;
 102 };
 103
 104 static const char *gcrypt_strerror(gcry_error_t gret)
 105 {
 106         return gcry_strerror(gcry_err_code(gret));
 107 }
 108
 109 /** ASN Types and their code. */
 110 enum asn1_types {
 111         /** The next object is an integer. */
 112         ASN1_TYPE_INTEGER = 0x2,
 113         /** Bit string object. */
 114         ASN1_TYPE_BIT_STRING = 0x03,
 115         /** Keys start with one big type sequence. */
 116         ASN1_TYPE_SEQUENCE = 0x30,
 117 };
 118
 119 /* bit 6 has value 0 */
 120 static inline bool is_primitive(unsigned char c)
 121 {
 122         return (c & (1<<6)) == 0;
 123 }
 124
 125 static inline bool is_primitive_integer(unsigned char c)
 126 {
 127         if (!is_primitive(c))
 128                 return false;
 129         return (c & 0x1f) == ASN1_TYPE_INTEGER;
 130 }
 131
 132 /* Bit 8 is zero (and bits 7-1 give the length) */
 133 static inline bool is_short_form(unsigned char c)
 134 {
 135         return (c & 0x80) == 0;
 136 }
 137
 138 static inline int get_short_form_length(unsigned char c)
 139 {
 140         return c & 0x7f;
 141 }
 142
 143 static inline int get_long_form_num_length_bytes(unsigned char c)
 144 {
 145         return c & 0x7f;
 146 }
 147
 148 /*
 149  * Returns: Number of bytes scanned. This may differ from the value returned via
 150  * bitsp because the latter does not include the ASN.1 prefix and a leading
 151  * zero is not considered as an additional byte for the number of bits.
 152  */
 153 static int read_pem_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
 154                 unsigned *bitsp)
 155 {
 156         int i, bn_size;
 157         gcry_error_t gret;
 158         unsigned char *cp = start;
 159
 160         if (!is_primitive_integer(*cp))
 161                 return -E_BAD_PRIVATE_KEY;
 162         cp++;
 163         if (is_short_form(*cp)) {
 164                 bn_size = get_short_form_length(*cp);
 165                 cp++;
 166         } else {
 167                 int num_bytes = get_long_form_num_length_bytes(*cp);
 168                 if (cp + num_bytes > end)
 169                         return -E_BAD_PRIVATE_KEY;
 170                 if (num_bytes > 4) /* nobody has such a large modulus */
 171                         return -E_BAD_PRIVATE_KEY;
 172                 cp++;
 173                 bn_size = 0;
 174                 for (i = 0; i < num_bytes; i++, cp++)
 175                         bn_size = (bn_size << 8) + *cp;
 176         }
 177         PARA_DEBUG_LOG("bn_size %d (0x%x)\n", bn_size, (unsigned)bn_size);
 178         gret = gcry_mpi_scan(bn, GCRYMPI_FMT_STD, cp, bn_size, NULL);
 179         if (gret) {
 180                 PARA_ERROR_LOG("gcry_mpi_scan: %s\n",
 181                         gcry_strerror(gcry_err_code(gret)));
 182                 return-E_MPI_SCAN;
 183         }
 184         /*
 185          * Don't take the first leading zero into account for the size of the
 186          * bignum.
 187          */
 188         if (*cp == '\0') {
 189                 cp++;
 190                 bn_size--;
 191         }
 192         if (bitsp)
 193                 *bitsp = bn_size * 8;
 194         cp += bn_size;
 195 //      unsigned char *buf;
 196 //      gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
 197 //      PARA_CRIT_LOG("bn: %s\n", buf);
 198         return cp - start;
 199 }
 200
 201 struct rsa_params {
 202         gcry_mpi_t n, e, d, p, q, u;
 203 };
 204
 205 static int read_pem_rsa_params(unsigned char *start, unsigned char *end,
 206                 struct rsa_params *p)
 207 {
 208         unsigned char *cp = start;
 209         unsigned bits;
 210         int ret;
 211
 212         ret = read_pem_bignum(cp, end, &p->n, &bits);
 213         if (ret < 0)
 214                 return ret;
 215         cp += ret;
 216         ret = read_pem_bignum(cp, end, &p->e, NULL);
 217         if (ret < 0)
 218                 goto release_n;
 219         cp += ret;
 220         ret = read_pem_bignum(cp, end, &p->d, NULL);
 221         if (ret < 0)
 222                 goto release_e;
 223         cp += ret;
 224         ret = read_pem_bignum(cp, end, &p->p, NULL);
 225         if (ret < 0)
 226                 goto release_d;
 227         cp += ret;
 228         ret = read_pem_bignum(cp, end, &p->q, NULL);
 229         if (ret < 0)
 230                 goto release_p;
 231         cp += ret;
 232         ret = read_pem_bignum(cp, end, &p->u, NULL);
 233         if (ret < 0)
 234                 goto release_q;
 235         return bits;
 236 release_q:
 237         gcry_mpi_release(p->q);
 238 release_p:
 239         gcry_mpi_release(p->p);
 240 release_d:
 241         gcry_mpi_release(p->d);
 242 release_e:
 243         gcry_mpi_release(p->e);
 244 release_n:
 245         gcry_mpi_release(p->n);
 246         return ret;
 247 }
 248
 249 static int find_pem_bignum_offset(const unsigned char *data, int len)
 250 {
 251         const unsigned char *p = data, *end = data + len;
 252
 253         /* like the public key, the whole thing is contained in a sequence */
 254         if (*p != ASN1_TYPE_SEQUENCE)
 255                 return -E_ASN1_PARSE;
 256         p++;
 257         if (p >= end)
 258                 return -E_ASN1_PARSE;
 259         if (is_short_form(*p))
 260                 p++;
 261         else
 262                 p += 1 + get_long_form_num_length_bytes(*p);
 263         if (p >= end)
 264                 return -E_ASN1_PARSE;
 265
 266         /* skip next integer */
 267         if (*p != ASN1_TYPE_INTEGER)
 268                 return -E_ASN1_PARSE;
 269         p++;
 270         if (p >= end)
 271                 return -E_ASN1_PARSE;
 272         if (is_short_form(*p))
 273                 p += 1 + get_short_form_length(*p);
 274         else
 275                 p += 1 + get_long_form_num_length_bytes(*p);
 276         if (p >= end)
 277                 return -E_ASN1_PARSE;
 278         return p - data;
 279 }
 280
 281 static int read_openssh_bignum(unsigned char *start, unsigned char *end,
 282                 gcry_mpi_t *bn, unsigned *bitsp)
 283 {
 284         gcry_error_t gret;
 285         size_t nscanned;
 286         unsigned bits;
 287
 288         gret = gcry_mpi_scan(bn, GCRYMPI_FMT_SSH, start, end - start, &nscanned);
 289         if (gret) {
 290                 PARA_ERROR_LOG("gcry_mpi_scan: %s\n",
 291                         gcry_strerror(gcry_err_code(gret)));
 292                 return -E_MPI_SCAN;
 293         }
 294         bits = (nscanned - 4 - (start[4] == '\0')) * 8;
 295         if (bitsp)
 296                 *bitsp = bits;
 297         PARA_DEBUG_LOG("scanned %u-bit bignum\n", bits);
 298         return nscanned;
 299 }
 300
 301 static int read_openssh_rsa_params(unsigned char *start, unsigned char *end,
 302                 struct rsa_params *p)
 303 {
 304         unsigned char *cp = start;
 305         unsigned bits;
 306         int ret;
 307
 308         ret = read_openssh_bignum(cp, end, &p->n, &bits);
 309         if (ret < 0)
 310                 return ret;
 311         cp += ret;
 312         ret = read_openssh_bignum(cp, end, &p->e, NULL);
 313         if (ret < 0)
 314                 goto release_n;
 315         cp += ret;
 316         ret = read_openssh_bignum(cp, end, &p->d, NULL);
 317         if (ret < 0)
 318                 goto release_e;
 319         cp += ret;
 320         ret = read_openssh_bignum(cp, end, &p->u, NULL);
 321         if (ret < 0)
 322                 goto release_d;
 323         cp += ret;
 324         ret = read_openssh_bignum(cp, end, &p->p, NULL);
 325         if (ret < 0)
 326                 goto release_u;
 327         cp += ret;
 328         ret = read_openssh_bignum(cp, end, &p->q, NULL);
 329         if (ret < 0)
 330                 goto release_p;
 331         return bits;
 332 release_p:
 333         gcry_mpi_release(p->p);
 334 release_u:
 335         gcry_mpi_release(p->u);
 336 release_d:
 337         gcry_mpi_release(p->d);
 338 release_e:
 339         gcry_mpi_release(p->e);
 340 release_n:
 341         gcry_mpi_release(p->n);
 342         return ret;
 343 }
 344
 345 static int get_private_key(const char *key_file, struct asymmetric_key **result)
 346 {
 347         struct rsa_params params;
 348         unsigned char *blob, *end;
 349         unsigned bits;
 350         int ret, key_type;
 351         gcry_error_t gret;
 352         size_t erroff, blob_size;
 353         gcry_sexp_t sexp;
 354         struct asymmetric_key *key;
 355
 356         *result = NULL;
 357         ret = decode_private_key(key_file, &blob, &blob_size);
 358         if (ret < 0)
 359                 return ret;
 360         key_type = ret;
 361         end = blob + blob_size;
 362         if (key_type == PKT_PEM)
 363                 ret = find_pem_bignum_offset(blob, blob_size);
 364         else
 365                 ret = find_openssh_bignum_offset(blob, blob_size);
 366         if (ret < 0)
 367                 goto free_blob;
 368         PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
 369         if (key_type == PKT_PEM)
 370                 ret = read_pem_rsa_params(blob + ret, end, &params);
 371         else
 372                 ret = read_openssh_rsa_params(blob + ret, end, &params);
 373         if (ret < 0)
 374                 goto free_blob;
 375         bits = ret;
 376         /*
 377          * OpenSSL uses slightly different parameters than gcrypt. To use these
 378          * parameters we need to swap the values of p and q and recompute u.
 379          */
 380         if (gcry_mpi_cmp(params.p, params.q) > 0) {
 381                 gcry_mpi_swap(params.p, params.q);
 382                 gcry_mpi_invm(params.u, params.p, params.q);
 383         }
 384         gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP, params.n,
 385                 params.e, params.d, params.p, params.q, params.u);
 386
 387         if (gret) {
 388                 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
 389                         gcry_strerror(gcry_err_code(gret)));
 390                 ret = -E_SEXP_BUILD;
 391                 goto free_params;
 392         }
 393         key = para_malloc(sizeof(*key));
 394         key->sexp = sexp;
 395         *result = key;
 396         ret = bits;
 397         PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
 398 free_params:
 399         gcry_mpi_release(params.n);
 400         gcry_mpi_release(params.e);
 401         gcry_mpi_release(params.d);
 402         gcry_mpi_release(params.u);
 403         gcry_mpi_release(params.p);
 404         gcry_mpi_release(params.q);
 405
 406 free_blob:
 407         free(blob);
 408         return ret;
 409 }
 410
 411 int apc_get_pubkey(const char *key_file, struct asymmetric_key **result)
 412 {
 413         unsigned char *blob, *p, *end;
 414         int ret;
 415         gcry_error_t gret;
 416         size_t erroff, decoded_size;
 417         gcry_mpi_t e, n;
 418         gcry_sexp_t sexp;
 419         struct asymmetric_key *key;
 420         unsigned bits;
 421
 422         ret = decode_public_key(key_file, &blob, &decoded_size);
 423         if (ret < 0)
 424                 return ret;
 425         p = blob + ret;
 426         end = blob + decoded_size;
 427         PARA_DEBUG_LOG("scanning modulus and public exponent\n");
 428         ret = read_openssh_bignum(p, end, &e, NULL);
 429         if (ret < 0)
 430                 goto free_blob;
 431         p += ret;
 432         ret = read_openssh_bignum(p, end, &n, &bits);
 433         if (ret < 0)
 434                 goto release_e;
 435         gret = gcry_sexp_build(&sexp, &erroff, RSA_PUBKEY_SEXP, n, e);
 436         if (gret) {
 437                 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
 438                         gcry_strerror(gcry_err_code(gret)));
 439                 ret = -E_SEXP_BUILD;
 440                 goto release_n;
 441         }
 442         PARA_INFO_LOG("successfully read %u bit ssh public key\n", bits);
 443         key = para_malloc(sizeof(*key));
 444         key->num_bytes = ret;
 445         key->sexp = sexp;
 446         *result = key;
 447         ret = bits;
 448 release_n:
 449         gcry_mpi_release(n);
 450 release_e:
 451         gcry_mpi_release(e);
 452 free_blob:
 453         free(blob);
 454         return ret;
 455 }
 456
 457 void apc_free_pubkey(struct asymmetric_key *key)
 458 {
 459         if (!key)
 460                 return;
 461         gcry_sexp_release(key->sexp);
 462         free(key);
 463 }
 464
 465 static int decode_rsa(gcry_sexp_t sexp, unsigned char *outbuf, size_t *nbytes)
 466 {
 467         const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
 468
 469         if (!p)
 470                 return -E_RSA_DECODE;
 471         memcpy(outbuf, p, *nbytes);
 472         return 1;
 473 }
 474
 475 int apc_priv_decrypt(const char *key_file, unsigned char *outbuf,
 476                 unsigned char *inbuf, int inlen)
 477 {
 478         gcry_error_t gret;
 479         int ret;
 480         struct asymmetric_key *priv;
 481         gcry_mpi_t in_mpi = NULL;
 482         gcry_sexp_t in, out, priv_key;
 483         size_t nbytes;
 484
 485         ret = check_private_key_file(key_file);
 486         if (ret < 0)
 487                 return ret;
 488         PARA_INFO_LOG("decrypting %d byte input\n", inlen);
 489         /* key_file -> asymmetric key priv */
 490         ret = get_private_key(key_file, &priv);
 491         if (ret < 0)
 492                 return ret;
 493
 494         /* asymmetric key priv -> sexp priv_key */
 495         ret = -E_SEXP_FIND;
 496         priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
 497         if (!priv_key)
 498                 goto free_key;
 499
 500         /* inbuf -> in_mpi */
 501         gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
 502                 inlen, NULL);
 503         if (gret) {
 504                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 505                 ret = -E_MPI_SCAN;
 506                 goto key_release;
 507         }
 508         /* in_mpi -> in sexp */
 509         gret = gcry_sexp_build(&in, NULL, RSA_DECRYPT_SEXP, in_mpi);
 510         if (gret) {
 511                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 512                 ret = -E_SEXP_BUILD;
 513                 goto in_mpi_release;
 514         }
 515
 516         /* rsa decryption: in sexp -> out sexp */
 517         gret = gcry_pk_decrypt(&out, in, priv_key);
 518         if (gret) {
 519                 PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
 520                 ret = -E_SEXP_DECRYPT;
 521                 goto in_release;
 522         }
 523         ret = decode_rsa(out, outbuf, &nbytes);
 524         if (ret < 0)
 525                 goto out_release;
 526         PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
 527         ret = nbytes;
 528 out_release:
 529         gcry_sexp_release(out);
 530 in_release:
 531         gcry_sexp_release(in);
 532 in_mpi_release:
 533         gcry_mpi_release(in_mpi);
 534 key_release:
 535         gcry_sexp_release(priv_key);
 536 free_key:
 537         gcry_sexp_release(priv->sexp);
 538         free(priv);
 539         return ret;
 540 }
 541
 542 int apc_pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
 543                 unsigned len, unsigned char *outbuf)
 544 {
 545         gcry_error_t gret;
 546         gcry_sexp_t pub_key, in, out, out_a;
 547         gcry_mpi_t out_mpi = NULL;
 548         size_t nbytes;
 549         int ret;
 550
 551         PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
 552
 553         /* get pub key */
 554         pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
 555         if (!pub_key)
 556                 return -E_SEXP_FIND;
 557         gret = gcry_sexp_build(&in, NULL, "(data(flags oaep)(value %b))", len, inbuf);
 558         if (gret) {
 559                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 560                 ret = -E_SEXP_BUILD;
 561                 goto key_release;
 562         }
 563         /* rsa sexp encryption: in -> out */
 564         gret = gcry_pk_encrypt(&out, in, pub_key);
 565         if (gret) {
 566                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 567                 ret = -E_SEXP_ENCRYPT;
 568                 goto in_release;
 569         }
 570         /* extract a, an MPI with the result of the RSA operation */
 571         ret = -E_SEXP_FIND;
 572         out_a = gcry_sexp_find_token(out, "a", 0);
 573         if (!out_a)
 574                 goto out_release;
 575         /* convert sexp out_a -> out_mpi */
 576         out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
 577         if (!out_mpi) {
 578                 ret = -E_SEXP_FIND;
 579                 goto out_a_release;
 580         }
 581         gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
 582         if (gret) {
 583                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 584                 ret = -E_SEXP_ENCRYPT;
 585                 goto out_mpi_release;
 586         }
 587         PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
 588         dump_buffer("enc buf", outbuf, nbytes);
 589         ret = nbytes;
 590
 591 out_mpi_release:
 592         gcry_mpi_release(out_mpi);
 593 out_a_release:
 594         gcry_sexp_release(out_a);
 595 out_release:
 596         gcry_sexp_release(out);
 597 in_release:
 598         gcry_sexp_release(in);
 599 key_release:
 600         gcry_sexp_release(pub_key);
 601         return ret;
 602 }
 603
 604 struct stream_cipher {
 605         gcry_cipher_hd_t handle;
 606 };
 607
 608 struct stream_cipher *sc_new(const unsigned char *data, int len)
 609 {
 610         gcry_error_t gret;
 611         struct stream_cipher *sc = para_malloc(sizeof(*sc));
 612
 613         assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
 614         gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_AES128,
 615                 GCRY_CIPHER_MODE_CTR, 0);
 616         assert(gret == 0);
 617         gret = gcry_cipher_setkey(sc->handle, data,
 618                 AES_CRT128_BLOCK_SIZE);
 619         assert(gret == 0);
 620         gret = gcry_cipher_setctr(sc->handle,
 621                 data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
 622         assert(gret == 0);
 623         return sc;
 624 }
 625
 626 void sc_free(struct stream_cipher *sc)
 627 {
 628         if (!sc)
 629                 return;
 630         gcry_cipher_close(sc->handle);
 631         free(sc);
 632 }
 633
 634 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
 635 {
 636         gcry_cipher_hd_t handle = sc->handle;
 637         gcry_error_t gret;
 638
 639         /* perform in-place encryption */
 640         *dst = *src;
 641         gret = gcry_cipher_encrypt(handle, src->iov_base, src->iov_len,
 642                 NULL, 0);
 643         assert(gret == 0);
 644 }