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 init_random_seed_or_die(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         get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
  70         srandom(seed);
  71 }
  72
  73 /** S-expression for the public part of an RSA key. */
  74 #define RSA_PUBKEY_SEXP "(public-key (rsa (n %m) (e %m)))"
  75 /** S-expression for a private RSA key. */
  76 #define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
  77 /** S-expression for decryption. */
  78 #define RSA_DECRYPT_SEXP "(enc-val(flags oaep)(rsa(a %m)))"
  79
  80 struct asymmetric_key {
  81         gcry_sexp_t sexp;
  82         int num_bytes;
  83 };
  84
  85 static const char *gcrypt_strerror(gcry_error_t gret)
  86 {
  87         return gcry_strerror(gcry_err_code(gret));
  88 }
  89
  90 static int decode_key(const char *key_file, const char *header_str,
  91                 const char *footer_str, unsigned char **result)
  92 {
  93         int ret, ret2, i, j;
  94         void *map;
  95         size_t map_size, key_size, blob_size;
  96         unsigned char *blob = NULL;
  97         char *begin, *footer, *key;
  98
  99         ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
 100         if (ret < 0)
 101                 goto out;
 102         ret = -E_KEY_MARKER;
 103         if (strncmp(map, header_str, strlen(header_str)))
 104                 goto unmap;
 105         footer = strstr(map, footer_str);
 106         ret = -E_KEY_MARKER;
 107         if (!footer)
 108                 goto unmap;
 109         begin = map + strlen(header_str);
 110         /* skip whitespace at the beginning */
 111         for (; begin < footer; begin++) {
 112                 if (para_isspace(*begin))
 113                         continue;
 114                 break;
 115         }
 116         ret = -E_KEY_MARKER;
 117         if (begin >= footer)
 118                 goto unmap;
 119
 120         key_size = footer - begin;
 121         key = para_malloc(key_size + 1);
 122         for (i = 0, j = 0; begin + i < footer; i++) {
 123                 if (para_isspace(begin[i]))
 124                         continue;
 125                 key[j++] = begin[i];
 126         }
 127         key[j] = '\0';
 128         ret = base64_decode(key, j, (char **)&blob, &blob_size);
 129         free(key);
 130         if (ret < 0)
 131                 goto free_unmap;
 132         ret = blob_size;
 133         goto unmap;
 134 free_unmap:
 135         free(blob);
 136         blob = NULL;
 137 unmap:
 138         ret2 = para_munmap(map, map_size);
 139         if (ret >= 0 && ret2 < 0)
 140                 ret = ret2;
 141         if (ret < 0) {
 142                 free(blob);
 143                 blob = NULL;
 144         }
 145 out:
 146         *result = blob;
 147         return ret;
 148 }
 149
 150 /** ASN Types and their code. */
 151 enum asn1_types {
 152         /** The next object is an integer. */
 153         ASN1_TYPE_INTEGER = 0x2,
 154         /** Bit string object. */
 155         ASN1_TYPE_BIT_STRING = 0x03,
 156         /** Keys start with one big type sequence. */
 157         ASN1_TYPE_SEQUENCE = 0x30,
 158 };
 159
 160 /* bit 6 has value 0 */
 161 static inline bool is_primitive(unsigned char c)
 162 {
 163         return (c & (1<<6)) == 0;
 164 }
 165
 166 static inline bool is_primitive_integer(unsigned char c)
 167 {
 168         if (!is_primitive(c))
 169                 return false;
 170         return (c & 0x1f) == ASN1_TYPE_INTEGER;
 171 }
 172
 173 /* Bit 8 is zero (and bits 7-1 give the length) */
 174 static inline bool is_short_form(unsigned char c)
 175 {
 176         return (c & 0x80) == 0;
 177 }
 178
 179 static inline int get_short_form_length(unsigned char c)
 180 {
 181         return c & 0x7f;
 182 }
 183
 184 static inline int get_long_form_num_length_bytes(unsigned char c)
 185 {
 186         return c & 0x7f;
 187 }
 188
 189 /*
 190  * Returns: Number of bytes scanned. This may differ from the value returned via
 191  * bn_bytes because the latter does not include the ASN.1 prefix and a leading
 192  * zero is not considered as an additional byte for bn_bytes.
 193  */
 194 static int read_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
 195                 int *bn_bytes)
 196 {
 197         int i, bn_size;
 198         gcry_error_t gret;
 199         unsigned char *cp = start;
 200
 201         if (!is_primitive_integer(*cp))
 202                 return -E_BAD_PRIVATE_KEY;
 203         cp++;
 204         if (is_short_form(*cp)) {
 205                 bn_size = get_short_form_length(*cp);
 206                 cp++;
 207         } else {
 208                 int num_bytes = get_long_form_num_length_bytes(*cp);
 209                 if (cp + num_bytes > end)
 210                         return -E_BAD_PRIVATE_KEY;
 211                 if (num_bytes > 4) /* nobody has such a large modulus */
 212                         return -E_BAD_PRIVATE_KEY;
 213                 cp++;
 214                 bn_size = 0;
 215                 for (i = 0; i < num_bytes; i++, cp++)
 216                         bn_size = (bn_size << 8) + *cp;
 217         }
 218         PARA_DEBUG_LOG("bn_size %d (0x%x)\n", bn_size, (unsigned)bn_size);
 219         gret = gcry_mpi_scan(bn, GCRYMPI_FMT_STD, cp, bn_size, NULL);
 220         if (gret) {
 221                 PARA_ERROR_LOG("%s while scanning n\n",
 222                         gcry_strerror(gcry_err_code(gret)));
 223                 return-E_MPI_SCAN;
 224         }
 225         /*
 226          * Don't take the first leading zero into account for the size of the
 227          * bignum.
 228          */
 229         if (*cp == '\0') {
 230                 cp++;
 231                 bn_size--;
 232         }
 233         if (bn_bytes)
 234                 *bn_bytes = bn_size;
 235         cp += bn_size;
 236 //      unsigned char *buf;
 237 //      gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
 238 //      PARA_CRIT_LOG("bn: %s\n", buf);
 239         return cp - start;
 240 }
 241
 242 static int find_privkey_bignum_offset(const unsigned char *data, int len)
 243 {
 244         const unsigned char *p = data, *end = data + len;
 245
 246         /* like the public key, the whole thing is contained in a sequence */
 247         if (*p != ASN1_TYPE_SEQUENCE)
 248                 return -E_ASN1_PARSE;
 249         p++;
 250         if (p >= end)
 251                 return -E_ASN1_PARSE;
 252         if (is_short_form(*p))
 253                 p++;
 254         else
 255                 p += 1 + get_long_form_num_length_bytes(*p);
 256         if (p >= end)
 257                 return -E_ASN1_PARSE;
 258
 259         /* skip next integer */
 260         if (*p != ASN1_TYPE_INTEGER)
 261                 return -E_ASN1_PARSE;
 262         p++;
 263         if (p >= end)
 264                 return -E_ASN1_PARSE;
 265         if (is_short_form(*p))
 266                 p += 1 + get_short_form_length(*p);
 267         else
 268                 p += 1 + get_long_form_num_length_bytes(*p);
 269         if (p >= end)
 270                 return -E_ASN1_PARSE;
 271         return p - data;
 272 }
 273
 274 /** Private keys start with this header. */
 275 #define PRIVATE_KEY_HEADER "-----BEGIN RSA PRIVATE KEY-----"
 276 /** Private keys end with this footer. */
 277 #define PRIVATE_KEY_FOOTER "-----END RSA PRIVATE KEY-----"
 278
 279 static int get_private_key(const char *key_file, struct asymmetric_key **result)
 280 {
 281         gcry_mpi_t n = NULL, e = NULL, d = NULL, p = NULL, q = NULL,
 282                 u = NULL;
 283         unsigned char *blob, *cp, *end;
 284         int blob_size, ret, n_size;
 285         gcry_error_t gret;
 286         size_t erroff;
 287         gcry_sexp_t sexp;
 288         struct asymmetric_key *key;
 289
 290         *result = NULL;
 291         ret = decode_key(key_file, PRIVATE_KEY_HEADER, PRIVATE_KEY_FOOTER,
 292                 &blob);
 293         if (ret < 0)
 294                 return ret;
 295         blob_size = ret;
 296         end = blob + blob_size;
 297         ret = find_privkey_bignum_offset(blob, blob_size);
 298         if (ret < 0)
 299                 goto free_blob;
 300         PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
 301         cp = blob + ret;
 302
 303         ret = read_bignum(cp, end, &n, &n_size);
 304         if (ret < 0)
 305                 goto free_blob;
 306         cp += ret;
 307
 308         ret = read_bignum(cp, end, &e, NULL);
 309         if (ret < 0)
 310                 goto release_n;
 311         cp += ret;
 312
 313         ret = read_bignum(cp, end, &d, NULL);
 314         if (ret < 0)
 315                 goto release_e;
 316         cp += ret;
 317
 318         ret = read_bignum(cp, end, &p, NULL);
 319         if (ret < 0)
 320                 goto release_d;
 321         cp += ret;
 322
 323         ret = read_bignum(cp, end, &q, NULL);
 324         if (ret < 0)
 325                 goto release_p;
 326         cp += ret;
 327         ret = read_bignum(cp, end, &u, NULL);
 328         if (ret < 0)
 329                 goto release_q;
 330         /*
 331          * OpenSSL uses slightly different parameters than gcrypt. To use these
 332          * parameters we need to swap the values of p and q and recompute u.
 333          */
 334         if (gcry_mpi_cmp(p, q) > 0) {
 335                 gcry_mpi_swap(p, q);
 336                 gcry_mpi_invm(u, p, q);
 337         }
 338         gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP,
 339                 n, e, d, p, q, u);
 340
 341         if (gret) {
 342                 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
 343                         gcry_strerror(gcry_err_code(gret)));
 344                 ret = -E_SEXP_BUILD;
 345                 goto release_u;
 346         }
 347         key = para_malloc(sizeof(*key));
 348         key->sexp = sexp;
 349         *result = key;
 350         ret = n_size * 8;
 351         PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
 352 release_u:
 353         gcry_mpi_release(u);
 354 release_q:
 355         gcry_mpi_release(q);
 356 release_p:
 357         gcry_mpi_release(p);
 358 release_d:
 359         gcry_mpi_release(d);
 360 release_e:
 361         gcry_mpi_release(e);
 362 release_n:
 363         gcry_mpi_release(n);
 364 free_blob:
 365         free(blob);
 366         return ret;
 367 }
 368
 369 static int get_ssh_public_key(unsigned char *data, int size, gcry_sexp_t *result)
 370 {
 371         int ret;
 372         gcry_error_t gret;
 373         unsigned char *blob = NULL, *p, *end;
 374         size_t nr_scanned, erroff, decoded_size;
 375         gcry_mpi_t e = NULL, n = NULL;
 376
 377         PARA_DEBUG_LOG("decoding %d byte public rsa-ssh key\n", size);
 378         ret = uudecode((char *)data, size, (char **)&blob, &decoded_size);
 379         if (ret < 0)
 380                 goto free_blob;
 381         end = blob + decoded_size;
 382         dump_buffer("decoded key", blob, decoded_size);
 383         ret = check_ssh_key_header(blob, decoded_size);
 384         if (ret < 0)
 385                 goto free_blob;
 386         p = blob + ret;
 387         ret = -E_SSH_PARSE;
 388         if (p >= end)
 389                 goto free_blob;
 390         PARA_DEBUG_LOG("scanning modulus and public exponent\n");
 391         gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
 392         if (gret) {
 393                 ret = -E_MPI_SCAN;
 394                 PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
 395                 goto free_blob;
 396         }
 397         PARA_DEBUG_LOG("scanned e (%zu bytes)\n", nr_scanned);
 398 //      gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_e);
 399 //      PARA_CRIT_LOG("e: %s\n", buf);
 400         p += nr_scanned;
 401         if (p >= end)
 402                 goto release_e;
 403         gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
 404         if (gret) {
 405                 ret = -E_MPI_SCAN;
 406                 PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
 407                 goto release_e;
 408         }
 409         PARA_DEBUG_LOG("scanned n (%zu bytes)\n", nr_scanned);
 410 //      gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_n);
 411 //      PARA_CRIT_LOG("n: %s\n", buf);
 412         gret = gcry_sexp_build(result, &erroff, RSA_PUBKEY_SEXP, n, e);
 413         if (gret) {
 414                 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
 415                         gcry_strerror(gcry_err_code(gret)));
 416                 ret = -E_SEXP_BUILD;
 417                 goto release_n;
 418         }
 419         ret = nr_scanned / 32 * 32;
 420         PARA_INFO_LOG("successfully read %d bit ssh public key\n", ret * 8);
 421 release_n:
 422         gcry_mpi_release(n);
 423 release_e:
 424         gcry_mpi_release(e);
 425 free_blob:
 426         free(blob);
 427         return ret;
 428 }
 429
 430 int get_public_key(const char *key_file, struct asymmetric_key **result)
 431 {
 432         int ret, ret2;
 433         void *map;
 434         size_t map_size;
 435         unsigned char *start, *end;
 436         gcry_sexp_t sexp;
 437         struct asymmetric_key *key;
 438
 439         ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
 440         if (ret < 0)
 441                 return ret;
 442         ret = is_ssh_rsa_key(map, map_size);
 443         if (!ret) {
 444                 para_munmap(map, map_size);
 445                 return -E_SSH_PARSE;
 446         }
 447         start = map + ret;
 448         end = map + map_size;
 449         ret = -E_SSH_PARSE;
 450         if (start >= end)
 451                 goto unmap;
 452         ret = get_ssh_public_key(start, end - start, &sexp);
 453         if (ret < 0)
 454                 goto unmap;
 455         key = para_malloc(sizeof(*key));
 456         key->num_bytes = ret;
 457         key->sexp = sexp;
 458         *result = key;
 459 unmap:
 460         ret2 = para_munmap(map, map_size);
 461         if (ret >= 0 && ret2 < 0)
 462                 ret = ret2;
 463         return ret;
 464 }
 465
 466 void free_public_key(struct asymmetric_key *key)
 467 {
 468         if (!key)
 469                 return;
 470         gcry_sexp_release(key->sexp);
 471         free(key);
 472 }
 473
 474 static int decode_rsa(gcry_sexp_t sexp, unsigned char *outbuf, size_t *nbytes)
 475 {
 476         const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
 477
 478         if (!p)
 479                 return -E_RSA_DECODE;
 480         memcpy(outbuf, p, *nbytes);
 481         return 1;
 482 }
 483
 484 int priv_decrypt(const char *key_file, unsigned char *outbuf,
 485                 unsigned char *inbuf, int inlen)
 486 {
 487         gcry_error_t gret;
 488         int ret;
 489         struct asymmetric_key *priv;
 490         gcry_mpi_t in_mpi = NULL;
 491         gcry_sexp_t in, out, priv_key;
 492         size_t nbytes;
 493
 494         ret = check_private_key_file(key_file);
 495         if (ret < 0)
 496                 return ret;
 497         PARA_INFO_LOG("decrypting %d byte input\n", inlen);
 498         /* key_file -> asymmetric key priv */
 499         ret = get_private_key(key_file, &priv);
 500         if (ret < 0)
 501                 return ret;
 502
 503         /* asymmetric key priv -> sexp priv_key */
 504         ret = -E_SEXP_FIND;
 505         priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
 506         if (!priv_key)
 507                 goto free_key;
 508
 509         /* inbuf -> in_mpi */
 510         gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
 511                 inlen, NULL);
 512         if (gret) {
 513                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 514                 ret = -E_MPI_SCAN;
 515                 goto key_release;
 516         }
 517         /* in_mpi -> in sexp */
 518         gret = gcry_sexp_build(&in, NULL, RSA_DECRYPT_SEXP, in_mpi);
 519         if (gret) {
 520                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 521                 ret = -E_SEXP_BUILD;
 522                 goto in_mpi_release;
 523         }
 524
 525         /* rsa decryption: in sexp -> out sexp */
 526         gret = gcry_pk_decrypt(&out, in, priv_key);
 527         if (gret) {
 528                 PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
 529                 ret = -E_SEXP_DECRYPT;
 530                 goto in_release;
 531         }
 532         ret = decode_rsa(out, outbuf, &nbytes);
 533         if (ret < 0)
 534                 goto out_release;
 535         PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
 536         ret = nbytes;
 537 out_release:
 538         gcry_sexp_release(out);
 539 in_release:
 540         gcry_sexp_release(in);
 541 in_mpi_release:
 542         gcry_mpi_release(in_mpi);
 543 key_release:
 544         gcry_sexp_release(priv_key);
 545 free_key:
 546         gcry_sexp_release(priv->sexp);
 547         free(priv);
 548         return ret;
 549 }
 550
 551 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
 552                 unsigned len, unsigned char *outbuf)
 553 {
 554         gcry_error_t gret;
 555         gcry_sexp_t pub_key, in, out, out_a;
 556         gcry_mpi_t out_mpi = NULL;
 557         size_t nbytes;
 558         int ret;
 559
 560         PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
 561
 562         /* get pub key */
 563         pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
 564         if (!pub_key)
 565                 return -E_SEXP_FIND;
 566         gret = gcry_sexp_build(&in, NULL, "(data(flags oaep)(value %b))", len, inbuf);
 567         if (gret) {
 568                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 569                 ret = -E_SEXP_BUILD;
 570                 goto key_release;
 571         }
 572         /* rsa sexp encryption: in -> out */
 573         gret = gcry_pk_encrypt(&out, in, pub_key);
 574         if (gret) {
 575                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 576                 ret = -E_SEXP_ENCRYPT;
 577                 goto in_release;
 578         }
 579         /* extract a, an MPI with the result of the RSA operation */
 580         ret = -E_SEXP_FIND;
 581         out_a = gcry_sexp_find_token(out, "a", 0);
 582         if (!out_a)
 583                 goto out_release;
 584         /* convert sexp out_a -> out_mpi */
 585         out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
 586         if (!out_mpi) {
 587                 ret = -E_SEXP_FIND;
 588                 goto out_a_release;
 589         }
 590         gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
 591         if (gret) {
 592                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 593                 ret = -E_SEXP_ENCRYPT;
 594                 goto out_mpi_release;
 595         }
 596         PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
 597         dump_buffer("enc buf", outbuf, nbytes);
 598         ret = nbytes;
 599
 600 out_mpi_release:
 601         gcry_mpi_release(out_mpi);
 602 out_a_release:
 603         gcry_sexp_release(out_a);
 604 out_release:
 605         gcry_sexp_release(out);
 606 in_release:
 607         gcry_sexp_release(in);
 608 key_release:
 609         gcry_sexp_release(pub_key);
 610         return ret;
 611 }
 612
 613 struct stream_cipher {
 614         gcry_cipher_hd_t handle;
 615 };
 616
 617 struct stream_cipher *sc_new(const unsigned char *data, int len)
 618 {
 619         gcry_error_t gret;
 620         struct stream_cipher *sc = para_malloc(sizeof(*sc));
 621
 622         assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
 623         gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_AES128,
 624                 GCRY_CIPHER_MODE_CTR, 0);
 625         assert(gret == 0);
 626         gret = gcry_cipher_setkey(sc->handle, data,
 627                 AES_CRT128_BLOCK_SIZE);
 628         assert(gret == 0);
 629         gret = gcry_cipher_setctr(sc->handle,
 630                 data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
 631         assert(gret == 0);
 632         return sc;
 633 }
 634
 635 void sc_free(struct stream_cipher *sc)
 636 {
 637         if (!sc)
 638                 return;
 639         gcry_cipher_close(sc->handle);
 640         free(sc);
 641 }
 642
 643 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
 644 {
 645         gcry_cipher_hd_t handle = sc->handle;
 646         gcry_error_t gret;
 647
 648         /* perform in-place encryption */
 649         *dst = *src;
 650         gret = gcry_cipher_encrypt(handle, src->iov_base, src->iov_len,
 651                 NULL, 0);
 652         assert(gret == 0);
 653 }