gcrypt.c

   1 /*
   2  * Copyright (C) 2011-2012 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file gcrypt.c Libgrcypt-based encryption/decryption routines. */
   8
   9 #include <regex.h>
  10 #include <gcrypt.h>
  11
  12 #include "para.h"
  13 #include "error.h"
  14 #include "string.h"
  15 #include "crypt.h"
  16 #include "crypt_backend.h"
  17 #include "fd.h"
  18
  19 //#define GCRYPT_DEBUG 1
  20
  21 static bool libgcrypt_has_oaep;
  22 static const char *rsa_decrypt_sexp;
  23
  24 #ifdef GCRYPT_DEBUG
  25 static void dump_buffer(const char *msg, unsigned char *buf, int len)
  26 {
  27         int i;
  28
  29         fprintf(stderr, "%s (%u bytes): ", msg, len);
  30         for (i = 0; i < len; i++)
  31                 fprintf(stderr, "%02x ", buf[i]);
  32         fprintf(stderr, "\n");
  33 }
  34 #else
  35 /** Empty. Define GCRYPT_DEBUG to dump buffers. */
  36 #define dump_buffer(a, b, c)
  37 #endif
  38
  39 void hash_function(const char *data, unsigned long len, unsigned char *hash)
  40 {
  41         gcry_error_t gret;
  42         gcry_md_hd_t handle;
  43         unsigned char *md;
  44
  45         gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
  46         assert(gret == 0);
  47         gcry_md_write(handle, data, (size_t)len);
  48         gcry_md_final(handle);
  49         md = gcry_md_read(handle, GCRY_MD_SHA1);
  50         assert(md);
  51         memcpy(hash, md, HASH_SIZE);
  52         gcry_md_close(handle);
  53 }
  54
  55 void get_random_bytes_or_die(unsigned char *buf, int num)
  56 {
  57         gcry_randomize(buf, (size_t)num, GCRY_STRONG_RANDOM);
  58 }
  59
  60 /*
  61  * This is called at the beginning of every program that uses libgcrypt. We
  62  * don't have to initialize any random seed here, but we must initialize the
  63  * gcrypt library. This task is performed by gcry_check_version() which can
  64  * also check that the gcrypt library version is at least the minimal required
  65  * version. This function also tells us whether we have to use our own OAEP
  66  * padding code.
  67  */
  68 void init_random_seed_or_die(void)
  69 {
  70         const char *ver, *req_ver;
  71
  72         ver = gcry_check_version(NULL);
  73         req_ver = "1.4.0";
  74         if (!gcry_check_version(req_ver)) {
  75                 PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
  76                         req_ver, ver);
  77                 exit(EXIT_FAILURE);
  78         }
  79         req_ver = "1.5.0";
  80         if (gcry_check_version(req_ver)) {
  81                 libgcrypt_has_oaep = true;
  82                 rsa_decrypt_sexp = "(enc-val(flags oaep)(rsa(a %m)))";
  83         } else {
  84                 libgcrypt_has_oaep = false;
  85                 rsa_decrypt_sexp = "(enc-val(rsa(a %m)))";
  86         }
  87 }
  88
  89 /** S-expression for the public part of an RSA key. */
  90 #define RSA_PUBKEY_SEXP  "(public-key (rsa (n %m) (e %m)))"
  91 /** S-expression for a private RSA key. */
  92 #define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
  93
  94 /* rfc 3447, appendix B.2 */
  95 static void mgf1(unsigned char *seed, size_t seed_len, unsigned result_len,
  96                 unsigned char *result)
  97 {
  98         gcry_error_t gret;
  99         gcry_md_hd_t handle;
 100         size_t n;;
 101         unsigned char *md;
 102         unsigned char octet_string[4], *rp = result, *end = rp + result_len;
 103
 104         assert(result_len / HASH_SIZE < 1ULL << 31);
 105         gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
 106         assert(gret == 0);
 107         for (n = 0; rp < end; n++) {
 108                 gcry_md_write(handle, seed, seed_len);
 109                 octet_string[0] = (unsigned char)((n >> 24) & 255);
 110                 octet_string[1] = (unsigned char)((n >> 16) & 255);
 111                 octet_string[2] = (unsigned char)((n >> 8)) & 255;
 112                 octet_string[3] = (unsigned char)(n & 255);
 113                 gcry_md_write(handle, octet_string, 4);
 114                 gcry_md_final(handle);
 115                 md = gcry_md_read(handle, GCRY_MD_SHA1);
 116                 memcpy(rp, md, PARA_MIN(HASH_SIZE, (int)(end - rp)));
 117                 rp += HASH_SIZE;
 118                 gcry_md_reset(handle);
 119         }
 120         gcry_md_close(handle);
 121 }
 122
 123 /** The sha1 hash of an empty file. */
 124 static const unsigned char empty_hash[HASH_SIZE] =
 125         "\xda" "\x39" "\xa3" "\xee" "\x5e"
 126         "\x6b" "\x4b" "\x0d" "\x32" "\x55"
 127         "\xbf" "\xef" "\x95" "\x60" "\x18"
 128         "\x90" "\xaf" "\xd8" "\x07" "\x09";
 129
 130 /* rfc3447, section 7.1.1 */
 131 static void pad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
 132                 size_t out_len)
 133 {
 134         size_t ps_len = out_len - in_len - 2 * HASH_SIZE - 2;
 135         size_t n, mask_len = out_len - HASH_SIZE - 1;
 136         unsigned char *seed = out + 1, *db = seed + HASH_SIZE,
 137                 *ps = db + HASH_SIZE, *one = ps + ps_len;
 138         unsigned char *db_mask, seed_mask[HASH_SIZE];
 139
 140         assert(in_len <= out_len - 2 - 2 * HASH_SIZE);
 141         assert(out_len > 2 * HASH_SIZE + 2);
 142         PARA_DEBUG_LOG("padding %zu byte input -> %zu byte output\n",
 143                 in_len, out_len);
 144         dump_buffer("unpadded buffer", in, in_len);
 145
 146         out[0] = '\0';
 147         get_random_bytes_or_die(seed, HASH_SIZE);
 148         memcpy(db, empty_hash, HASH_SIZE);
 149         memset(ps, 0, ps_len);
 150         *one = 0x01;
 151         memcpy(one + 1, in, in_len);
 152         db_mask = para_malloc(mask_len);
 153         mgf1(seed, HASH_SIZE, mask_len, db_mask);
 154         for (n = 0; n < mask_len; n++)
 155                 db[n] ^= db_mask[n];
 156         mgf1(db, mask_len, HASH_SIZE, seed_mask);
 157         for (n = 0; n < HASH_SIZE; n++)
 158                 seed[n] ^= seed_mask[n];
 159         free(db_mask);
 160         dump_buffer("padded buffer", out, out_len);
 161 }
 162
 163 /* rfc 3447, section 7.1.2 */
 164 static int unpad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
 165                 size_t *out_len)
 166 {
 167         unsigned char *masked_seed = in + 1;
 168         unsigned char *db = in + 1 + HASH_SIZE;
 169         unsigned char seed[HASH_SIZE], seed_mask[HASH_SIZE];
 170         unsigned char *db_mask, *p;
 171         size_t n, mask_len = in_len - HASH_SIZE - 1;
 172
 173         mgf1(db, mask_len, HASH_SIZE, seed_mask);
 174         for (n = 0; n < HASH_SIZE; n++)
 175                 seed[n] = masked_seed[n] ^ seed_mask[n];
 176         db_mask = para_malloc(mask_len);
 177         mgf1(seed, HASH_SIZE, mask_len, db_mask);
 178         for (n = 0; n < mask_len; n++)
 179                 db[n] ^= db_mask[n];
 180         free(db_mask);
 181         if (memcmp(db, empty_hash, HASH_SIZE))
 182                 return -E_OEAP;
 183         for (p = db + HASH_SIZE; p < in + in_len - 1; p++)
 184                 if (*p != '\0')
 185                         break;
 186         if (p >= in + in_len - 1)
 187                 return -E_OEAP;
 188         p++;
 189         *out_len = in + in_len - p;
 190         memcpy(out, p, *out_len);
 191         return 1;
 192 }
 193
 194 struct asymmetric_key {
 195         gcry_sexp_t sexp;
 196         int num_bytes;
 197 };
 198
 199 static const char *gcrypt_strerror(gcry_error_t gret)
 200 {
 201         return gcry_strerror(gcry_err_code(gret));
 202 }
 203
 204 static int decode_key(const char *key_file, const char *header_str,
 205                 const char *footer_str, unsigned char **result)
 206 {
 207         int ret, ret2, i, j;
 208         void *map;
 209         size_t map_size, key_size, blob_size;
 210         unsigned char *blob = NULL;
 211         char *begin, *footer, *key;
 212
 213         ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
 214         if (ret < 0)
 215                 return ret;
 216         ret = -E_KEY_MARKER;
 217         if (strncmp(map, header_str, strlen(header_str)))
 218                 goto unmap;
 219         footer = strstr(map, footer_str);
 220         ret = -E_KEY_MARKER;
 221         if (!footer)
 222                 goto unmap;
 223         begin = map + strlen(header_str);
 224         /* skip whitespace at the beginning */
 225         for (; begin < footer; begin++) {
 226                 if (para_isspace(*begin))
 227                         continue;
 228                 break;
 229         }
 230         ret = -E_KEY_MARKER;
 231         if (begin >= footer)
 232                 goto unmap;
 233
 234         key_size = footer - begin;
 235         key = para_malloc(key_size + 1);
 236         for (i = 0, j = 0; begin + i < footer; i++) {
 237                 if (para_isspace(begin[i]))
 238                         continue;
 239                 key[j++] = begin[i];
 240         }
 241         key[j] = '\0';
 242         //PARA_CRIT_LOG("key: %s\n", key);
 243         blob_size = key_size * 2;
 244         blob = para_malloc(blob_size);
 245         ret = base64_decode(key, blob, blob_size);
 246         free(key);
 247         if (ret < 0)
 248                 goto free_unmap;
 249         goto unmap;
 250 free_unmap:
 251         free(blob);
 252         blob = NULL;
 253 unmap:
 254         ret2 = para_munmap(map, map_size);
 255         if (ret >= 0 && ret2 < 0)
 256                 ret = ret2;
 257         if (ret < 0) {
 258                 free(blob);
 259                 blob = NULL;
 260         }
 261         *result = blob;
 262         return ret;
 263 }
 264
 265 /** ASN Types and their code. */
 266 enum asn1_types {
 267         /** The next object is an integer. */
 268         ASN1_TYPE_INTEGER = 0x2,
 269         /** Bit string object. */
 270         ASN1_TYPE_BIT_STRING = 0x03,
 271         /** Keys start with one big type sequence. */
 272         ASN1_TYPE_SEQUENCE = 0x30,
 273 };
 274
 275 /* bit 6 has value 0 */
 276 static inline bool is_primitive(unsigned char c)
 277 {
 278         return ((c & (1<<6)) == 0);
 279 }
 280
 281 static inline bool is_primitive_integer(unsigned char c)
 282 {
 283         if (!is_primitive(c))
 284                 return false;
 285         return ((c & 0x1f) == ASN1_TYPE_INTEGER);
 286 }
 287
 288 /* Bit 8 is zero (and bits 7-1 give the length) */
 289 static inline bool is_short_form(unsigned char c)
 290 {
 291         return (c & 0x80) == 0;
 292 }
 293
 294 static inline int get_short_form_length(unsigned char c)
 295 {
 296         return c & 0x7f;
 297 }
 298
 299 static inline int get_long_form_num_length_bytes(unsigned char c)
 300 {
 301         return c & 0x7f;
 302 }
 303
 304 static int find_pubkey_bignum_offset(const unsigned char *data, int len)
 305 {
 306         const unsigned char *p = data, *end = data + len;
 307
 308         /* the whole thing istarts with one sequence */
 309         if (*p != ASN1_TYPE_SEQUENCE)
 310                 return -E_ASN1_PARSE;
 311         p++;
 312         if (p >= end)
 313                 return -E_ASN1_PARSE;
 314         if (is_short_form(*p))
 315                 p++;
 316         else
 317                 p += 1 + get_long_form_num_length_bytes(*p);
 318         if (p >= end)
 319                 return -E_ASN1_PARSE;
 320         /* another sequence containing the object id, skip it */
 321         if (*p != ASN1_TYPE_SEQUENCE)
 322                 return -E_ASN1_PARSE;
 323         p++;
 324         if (p >= end)
 325                 return -E_ASN1_PARSE;
 326         if (!is_short_form(*p))
 327                 return -E_ASN1_PARSE;
 328         p += 1 + get_short_form_length(*p);
 329         if (p >= end)
 330                 return -E_ASN1_PARSE;
 331         /* all numbers are wrapped in a bit string object that follows */
 332         if (*p != ASN1_TYPE_BIT_STRING)
 333                 return -E_ASN1_PARSE;
 334         p++;
 335         if (p >= end)
 336                 return -E_ASN1_PARSE;
 337         if (is_short_form(*p))
 338                 p++;
 339         else
 340                 p += 1 + get_long_form_num_length_bytes(*p);
 341         p++; /* skip number of unused bits in the bit string */
 342         if (p >= end)
 343                 return -E_ASN1_PARSE;
 344
 345         /* next, we have a sequence of two integers (n and e) */
 346         if (*p != ASN1_TYPE_SEQUENCE)
 347                 return -E_ASN1_PARSE;
 348         p++;
 349         if (p >= end)
 350                 return -E_ASN1_PARSE;
 351         if (is_short_form(*p))
 352                 p++;
 353         else
 354                 p += 1 + get_long_form_num_length_bytes(*p);
 355         if (p >= end)
 356                 return -E_ASN1_PARSE;
 357         if (*p != ASN1_TYPE_INTEGER)
 358                 return -E_ASN1_PARSE;
 359         return p - data;
 360 }
 361
 362 /*
 363  * Returns: Number of bytes scanned. This may differ from the value returned via
 364  * bn_bytes because the latter does not include the ASN.1 prefix and a leading
 365  * zero is not considered as an additional byte for bn_bytes.
 366  */
 367 static int read_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
 368                 int *bn_bytes)
 369 {
 370         int i, bn_size;
 371         gcry_error_t gret;
 372         unsigned char *cp = start;
 373
 374         if (!is_primitive_integer(*cp))
 375                 return -E_BAD_PRIVATE_KEY;
 376         cp++;
 377         if (is_short_form(*cp)) {
 378                 bn_size = get_short_form_length(*cp);
 379                 cp++;
 380         } else {
 381                 int num_bytes = get_long_form_num_length_bytes(*cp);
 382                 if (cp + num_bytes > end)
 383                         return -E_BAD_PRIVATE_KEY;
 384                 if (num_bytes > 4) /* nobody has such a large modulus */
 385                         return -E_BAD_PRIVATE_KEY;
 386                 cp++;
 387                 bn_size = 0;
 388                 for (i = 0; i < num_bytes; i++, cp++)
 389                         bn_size = (bn_size << 8) + *cp;
 390         }
 391         PARA_DEBUG_LOG("bn_size %d (0x%x)\n", bn_size, bn_size);
 392         gret = gcry_mpi_scan(bn, GCRYMPI_FMT_STD, cp, bn_size, NULL);
 393         if (gret) {
 394                 PARA_ERROR_LOG("%s while scanning n\n",
 395                         gcry_strerror(gcry_err_code(gret)));
 396                 return-E_MPI_SCAN;
 397         }
 398         /*
 399          * Don't take the first leading zero into account for the size of the
 400          * bignum.
 401          */
 402         if (*cp == '\0') {
 403                 cp++;
 404                 bn_size--;
 405         }
 406         if (bn_bytes)
 407                 *bn_bytes = bn_size;
 408         cp += bn_size;
 409 //      unsigned char *buf;
 410 //      gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
 411 //      PARA_CRIT_LOG("bn: %s\n", buf);
 412         return cp - start;
 413 }
 414
 415 static int find_privkey_bignum_offset(const unsigned char *data, int len)
 416 {
 417         const unsigned char *p = data, *end = data + len;
 418
 419         /* like the public key, the whole thing is contained in a sequence */
 420         if (*p != ASN1_TYPE_SEQUENCE)
 421                 return -E_ASN1_PARSE;
 422         p++;
 423         if (p >= end)
 424                 return -E_ASN1_PARSE;
 425         if (is_short_form(*p))
 426                 p++;
 427         else
 428                 p += 1 + get_long_form_num_length_bytes(*p);
 429         if (p >= end)
 430                 return -E_ASN1_PARSE;
 431
 432         /* Skip next integer  */
 433         if (*p != ASN1_TYPE_INTEGER)
 434                 return -E_ASN1_PARSE;
 435         p++;
 436         if (p >= end)
 437                 return -E_ASN1_PARSE;
 438         if (is_short_form(*p))
 439                 p += 1 + get_short_form_length(*p);
 440         else
 441                 p += 1 + get_long_form_num_length_bytes(*p);
 442         if (p >= end)
 443                 return -E_ASN1_PARSE;
 444         return p - data;
 445 }
 446
 447 /** Private keys start with this header. */
 448 #define PRIVATE_KEY_HEADER "-----BEGIN RSA PRIVATE KEY-----"
 449 /** Private keys end with this footer. */
 450 #define PRIVATE_KEY_FOOTER "-----END RSA PRIVATE KEY-----"
 451
 452 static int get_private_key(const char *key_file, struct asymmetric_key **result)
 453 {
 454         gcry_mpi_t n = NULL, e = NULL, d = NULL, p = NULL, q = NULL,
 455                 u = NULL;
 456         unsigned char *blob, *cp, *end;
 457         int blob_size, ret, n_size;
 458         gcry_error_t gret;
 459         size_t erroff;
 460         gcry_sexp_t sexp;
 461         struct asymmetric_key *key;
 462
 463         ret = decode_key(key_file, PRIVATE_KEY_HEADER, PRIVATE_KEY_FOOTER,
 464                 &blob);
 465         if (ret < 0)
 466                 return ret;
 467         blob_size = ret;
 468         end = blob + blob_size;
 469         ret = find_privkey_bignum_offset(blob, blob_size);
 470         if (ret < 0)
 471                 goto free_blob;
 472         PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
 473         cp = blob + ret;
 474
 475         ret = read_bignum(cp, end, &n, &n_size);
 476         if (ret < 0)
 477                 goto free_blob;
 478         cp += ret;
 479
 480         ret = read_bignum(cp, end, &e, NULL);
 481         if (ret < 0)
 482                 goto release_n;
 483         cp += ret;
 484
 485         ret = read_bignum(cp, end, &d, NULL);
 486         if (ret < 0)
 487                 goto release_e;
 488         cp += ret;
 489
 490         ret = read_bignum(cp, end, &p, NULL);
 491         if (ret < 0)
 492                 goto release_d;
 493         cp += ret;
 494
 495         ret = read_bignum(cp, end, &q, NULL);
 496         if (ret < 0)
 497                 goto release_p;
 498         cp += ret;
 499         ret = read_bignum(cp, end, &u, NULL);
 500         if (ret < 0)
 501                 goto release_q;
 502         cp += ret;
 503         /*
 504          * OpenSSL uses slightly different parameters than gcrypt. To use these
 505          * parameters we need to swap the values of p and q and recompute u.
 506          */
 507         if (gcry_mpi_cmp(p, q) > 0) {
 508                 gcry_mpi_swap(p, q);
 509                 gcry_mpi_invm(u, p, q);
 510         }
 511         gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP,
 512                 n, e, d, p, q, u);
 513
 514         if (gret) {
 515                 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
 516                         gcry_strerror(gcry_err_code(gret)));
 517                 ret = -E_SEXP_BUILD;
 518                 goto release_u;
 519         }
 520         key = para_malloc(sizeof(*key));
 521         key->sexp = sexp;
 522         *result = key;
 523         ret = n_size * 8;
 524         PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
 525 release_u:
 526         gcry_mpi_release(u);
 527 release_q:
 528         gcry_mpi_release(q);
 529 release_p:
 530         gcry_mpi_release(p);
 531 release_d:
 532         gcry_mpi_release(d);
 533 release_e:
 534         gcry_mpi_release(e);
 535 release_n:
 536         gcry_mpi_release(n);
 537 free_blob:
 538         free(blob);
 539         return ret;
 540 }
 541
 542 /** Public keys start with this header. */
 543 #define PUBLIC_KEY_HEADER "-----BEGIN PUBLIC KEY-----"
 544 /** Public keys end with this footer. */
 545 #define PUBLIC_KEY_FOOTER "-----END PUBLIC KEY-----"
 546
 547 static int get_asn_public_key(const char *key_file, struct asymmetric_key **result)
 548 {
 549         gcry_mpi_t n = NULL, e = NULL;
 550         unsigned char *blob, *cp, *end;
 551         int blob_size, ret, n_size;
 552         gcry_error_t gret;
 553         size_t erroff;
 554         gcry_sexp_t sexp;
 555         struct asymmetric_key *key;
 556
 557         ret = decode_key(key_file, PUBLIC_KEY_HEADER, PUBLIC_KEY_FOOTER,
 558                 &blob);
 559         if (ret < 0)
 560                 return ret;
 561         blob_size = ret;
 562         end = blob + blob_size;
 563         ret = find_pubkey_bignum_offset(blob, blob_size);
 564         if (ret < 0)
 565                 goto free_blob;
 566         PARA_DEBUG_LOG("decoding public RSA params at offset %d\n", ret);
 567         cp = blob + ret;
 568
 569         ret = read_bignum(cp, end, &n, &n_size);
 570         if (ret < 0)
 571                 goto free_blob;
 572         cp += ret;
 573
 574         ret = read_bignum(cp, end, &e, NULL);
 575         if (ret < 0)
 576                 goto release_n;
 577         cp += ret;
 578
 579         gret = gcry_sexp_build(&sexp, &erroff, RSA_PUBKEY_SEXP, n, e);
 580         if (gret) {
 581                 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
 582                         gcry_strerror(gcry_err_code(gret)));
 583                 ret = -E_SEXP_BUILD;
 584                 goto release_e;
 585         }
 586         key = para_malloc(sizeof(*key));
 587         key->sexp = sexp;
 588         *result = key;
 589         ret = n_size;
 590         PARA_INFO_LOG("successfully read %u bit asn public key\n", n_size * 8);
 591
 592 release_e:
 593         gcry_mpi_release(e);
 594 release_n:
 595         gcry_mpi_release(n);
 596 free_blob:
 597         free(blob);
 598         return ret;
 599 }
 600
 601 static int get_ssh_public_key(unsigned char *data, int size, gcry_sexp_t *result)
 602 {
 603         int ret;
 604         gcry_error_t gret;
 605         unsigned char *blob = NULL, *p, *end;
 606         size_t nr_scanned, erroff, decoded_size;
 607         gcry_mpi_t e = NULL, n = NULL;
 608
 609         PARA_DEBUG_LOG("decoding %d byte  public rsa-ssh key\n", size);
 610         if (size > INT_MAX / 4)
 611                 return -ERRNO_TO_PARA_ERROR(EOVERFLOW);
 612         blob = para_malloc(2 * size);
 613         ret = uudecode((char *)data, blob, 2 * size);
 614         if (ret < 0)
 615                 goto free_blob;
 616         decoded_size = ret;
 617         end = blob + decoded_size;
 618         dump_buffer("decoded key", blob, decoded_size);
 619         ret = check_ssh_key_header(blob, decoded_size);
 620         if (ret < 0)
 621                 goto free_blob;
 622         p = blob + ret;
 623         ret = -E_SSH_PARSE;
 624         if (p >= end)
 625                 goto free_blob;
 626         PARA_DEBUG_LOG("scanning modulus and public exponent\n");
 627         gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
 628         if (gret) {
 629                 ret = -E_MPI_SCAN;
 630                 PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
 631                 goto free_blob;
 632         }
 633         PARA_DEBUG_LOG("scanned e (%zu bytes)\n", nr_scanned);
 634 //      gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_e);
 635 //      PARA_CRIT_LOG("e: %s\n", buf);
 636         p += nr_scanned;
 637         if (p >= end)
 638                 goto release_e;
 639         gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
 640         if (gret) {
 641                 ret = -E_MPI_SCAN;
 642                 PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
 643                 goto release_e;
 644         }
 645         PARA_DEBUG_LOG("scanned n (%zu bytes)\n", nr_scanned);
 646 //      gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_n);
 647 //      PARA_CRIT_LOG("n: %s\n", buf);
 648         gret = gcry_sexp_build(result, &erroff, RSA_PUBKEY_SEXP, n, e);
 649         if (gret) {
 650                 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
 651                         gcry_strerror(gcry_err_code(gret)));
 652                 ret = -E_SEXP_BUILD;
 653                 goto release_n;
 654         }
 655         ret = nr_scanned / 32 * 32;
 656         PARA_INFO_LOG("successfully read %u bit ssh public key\n", ret * 8);
 657 release_n:
 658         gcry_mpi_release(n);
 659 release_e:
 660         gcry_mpi_release(e);
 661 free_blob:
 662         free(blob);
 663         return ret;
 664 }
 665
 666 int get_asymmetric_key(const char *key_file, int private,
 667                 struct asymmetric_key **result)
 668 {
 669         int ret, ret2;
 670         void *map;
 671         size_t map_size;
 672         unsigned char *start, *end;
 673         gcry_sexp_t sexp;
 674         struct asymmetric_key *key;
 675
 676         if (private)
 677                 return get_private_key(key_file, result);
 678         ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
 679         if (ret < 0)
 680                 return ret;
 681         ret = is_ssh_rsa_key(map, map_size);
 682         if (!ret) {
 683                 ret = para_munmap(map, map_size);
 684                 if (ret < 0)
 685                         return ret;
 686                 return get_asn_public_key(key_file, result);
 687         }
 688         start = map + ret;
 689         end = map + map_size;
 690         ret = -E_SSH_PARSE;
 691         if (start >= end)
 692                 goto unmap;
 693         ret = get_ssh_public_key(start, end - start, &sexp);
 694         if (ret < 0)
 695                 goto unmap;
 696         key = para_malloc(sizeof(*key));
 697         key->num_bytes = ret;
 698         key->sexp = sexp;
 699         *result = key;
 700         ret = key->num_bytes;
 701 unmap:
 702         ret2 = para_munmap(map, map_size);
 703         if (ret >= 0 && ret2 < 0)
 704                 ret = ret2;
 705         return ret;
 706 }
 707
 708 void free_asymmetric_key(struct asymmetric_key *key)
 709 {
 710         if (!key)
 711                 return;
 712         gcry_sexp_release(key->sexp);
 713         free(key);
 714 }
 715
 716 static int decode_rsa(gcry_sexp_t sexp, int key_size, unsigned char *outbuf,
 717                 size_t *nbytes)
 718 {
 719         int ret;
 720         gcry_error_t gret;
 721         unsigned char oaep_buf[512];
 722         gcry_mpi_t out_mpi;
 723
 724         if (libgcrypt_has_oaep) {
 725                 const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
 726
 727                 if (!p) {
 728                         PARA_ERROR_LOG("could not get data from list\n");
 729                         return -E_OEAP;
 730                 }
 731                 memcpy(outbuf, p, *nbytes);
 732                 return 1;
 733         }
 734         out_mpi = gcry_sexp_nth_mpi(sexp, 0, GCRYMPI_FMT_USG);
 735         if (!out_mpi)
 736                 return -E_SEXP_FIND;
 737         gret = gcry_mpi_print(GCRYMPI_FMT_USG, oaep_buf, sizeof(oaep_buf),
 738                 nbytes, out_mpi);
 739         if (gret) {
 740                 PARA_ERROR_LOG("mpi_print: %s\n", gcrypt_strerror(gret));
 741                 ret = -E_MPI_PRINT;
 742                 goto out_mpi_release;
 743         }
 744         /*
 745          * An oaep-encoded buffer always starts with at least one zero byte.
 746          * However, leading zeroes in an mpi are omitted in the output of
 747          * gcry_mpi_print() when using the GCRYMPI_FMT_USG format. The
 748          * alternative, GCRYMPI_FMT_STD, does not work either because here the
 749          * leading zero(es) might also be omitted, depending on the value of
 750          * the second byte.
 751          *
 752          * To circumvent this, we shift the oaep buffer to the right. But first
 753          * we check that the buffer actually started with a zero byte, i.e. that
 754          * nbytes < key_size. Otherwise a decoding error occurred.
 755          */
 756         ret = -E_SEXP_DECRYPT;
 757         if (*nbytes >= key_size)
 758                 goto out_mpi_release;
 759         memmove(oaep_buf + key_size - *nbytes, oaep_buf, *nbytes);
 760         memset(oaep_buf, 0, key_size - *nbytes);
 761
 762         PARA_DEBUG_LOG("decrypted buffer before unpad (%d bytes):\n",
 763                 key_size);
 764         dump_buffer("non-unpadded decrypted buffer", oaep_buf, key_size);;
 765         ret = unpad_oaep(oaep_buf, key_size, outbuf, nbytes);
 766         if (ret < 0)
 767                 goto out_mpi_release;
 768         PARA_DEBUG_LOG("decrypted buffer after unpad (%zu bytes):\n",
 769                 *nbytes);
 770         dump_buffer("unpadded decrypted buffer", outbuf, *nbytes);;
 771         ret = 1;
 772 out_mpi_release:
 773         gcry_mpi_release(out_mpi);
 774         return ret;
 775 }
 776
 777 int priv_decrypt(const char *key_file, unsigned char *outbuf,
 778                 unsigned char *inbuf, int inlen)
 779 {
 780         gcry_error_t gret;
 781         int ret, key_size;
 782         struct asymmetric_key *priv;
 783         gcry_mpi_t in_mpi = NULL;
 784         gcry_sexp_t in, out, priv_key;
 785         size_t nbytes;
 786
 787         PARA_INFO_LOG("decrypting %d byte input\n", inlen);
 788         /* key_file -> asymmetric key priv */
 789         ret = get_private_key(key_file, &priv);
 790         if (ret < 0)
 791                 return ret;
 792         key_size = ret / 8;
 793
 794         /* asymmetric key priv -> sexp priv_key */
 795         ret = -E_SEXP_FIND;
 796         priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
 797         if (!priv_key)
 798                 goto free_key;
 799
 800         /* inbuf -> in_mpi */
 801         gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
 802                 inlen, NULL);
 803         if (gret) {
 804                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 805                 ret = -E_MPI_SCAN;
 806                 goto key_release;
 807         }
 808         /* in_mpi -> in sexp */
 809         gret = gcry_sexp_build(&in, NULL, rsa_decrypt_sexp, in_mpi);
 810         if (gret) {
 811                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 812                 ret = -E_SEXP_BUILD;
 813                 goto in_mpi_release;
 814         }
 815
 816         /* rsa decryption: in sexp -> out sexp */
 817         gret = gcry_pk_decrypt(&out, in, priv_key);
 818         if (gret) {
 819                 PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
 820                 ret = -E_SEXP_DECRYPT;
 821                 goto in_release;
 822         }
 823         ret = decode_rsa(out, key_size, outbuf, &nbytes);
 824         if (ret < 0)
 825                 goto out_release;
 826         PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
 827         ret = nbytes;
 828 out_release:
 829         gcry_sexp_release(out);
 830 in_release:
 831         gcry_sexp_release(in);
 832 in_mpi_release:
 833         gcry_mpi_release(in_mpi);
 834 key_release:
 835         gcry_sexp_release(priv_key);
 836 free_key:
 837         free_asymmetric_key(priv);
 838         return ret;
 839 }
 840
 841 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
 842                 unsigned len, unsigned char *outbuf)
 843 {
 844         gcry_error_t gret;
 845         gcry_sexp_t pub_key, in, out, out_a;
 846         gcry_mpi_t out_mpi = NULL;
 847         size_t nbytes;
 848         int ret;
 849
 850         PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
 851
 852         /* get pub key */
 853         pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
 854         if (!pub_key)
 855                 return -E_SEXP_FIND;
 856         if (libgcrypt_has_oaep) {
 857                 gret = gcry_sexp_build(&in, NULL,
 858                         "(data(flags oaep)(value %b))", len, inbuf);
 859         } else {
 860                 unsigned char padded_input[256];
 861                 const size_t pad_size = 256;
 862                 /* inbuf -> padded inbuf */
 863                 pad_oaep(inbuf, len, padded_input, pad_size);
 864                 /* padded inbuf -> in sexp */
 865                 gret = gcry_sexp_build(&in, NULL,
 866                         "(data(flags raw)(value %b))", pad_size, padded_input);
 867         }
 868         if (gret) {
 869                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 870                 ret = -E_SEXP_BUILD;
 871                 goto key_release;
 872         }
 873         /* rsa sexp encryption: in -> out */
 874         gret = gcry_pk_encrypt(&out, in, pub_key);
 875         if (gret) {
 876                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 877                 ret = -E_SEXP_ENCRYPT;
 878                 goto in_release;
 879         }
 880         /* extract a, an MPI with the result of the RSA operation */
 881         ret = -E_SEXP_FIND;
 882         out_a = gcry_sexp_find_token(out, "a", 0);
 883         if (!out_a)
 884                 goto out_release;
 885         /* convert sexp out_a -> out_mpi */
 886         out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
 887         if (!out_mpi) {
 888                 ret = -E_SEXP_FIND;
 889                 goto out_a_release;
 890         }
 891         gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
 892         if (gret) {
 893                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 894                 ret = -E_SEXP_ENCRYPT;
 895                 goto out_mpi_release;
 896         }
 897         PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
 898         dump_buffer("enc buf", outbuf, nbytes);
 899         ret = nbytes;
 900
 901 out_mpi_release:
 902         gcry_mpi_release(out_mpi);
 903 out_a_release:
 904         gcry_sexp_release(out_a);
 905 out_release:
 906         gcry_sexp_release(out);
 907 in_release:
 908         gcry_sexp_release(in);
 909 key_release:
 910         gcry_sexp_release(pub_key);
 911         return ret;
 912 }
 913
 914 struct stream_cipher {
 915         gcry_cipher_hd_t handle;
 916 };
 917
 918 struct stream_cipher *sc_new(const unsigned char *data, int len)
 919 {
 920         gcry_error_t gret;
 921
 922         struct stream_cipher *sc = para_malloc(sizeof(*sc));
 923         gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_ARCFOUR,
 924                 GCRY_CIPHER_MODE_STREAM, 0);
 925         if (gret) {
 926                 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 927                 free(sc);
 928                 return NULL;
 929         }
 930         gret = gcry_cipher_setkey(sc->handle, data, (size_t)len);
 931         assert(gret == 0);
 932         return sc;
 933 }
 934
 935 void sc_free(struct stream_cipher *sc)
 936 {
 937         if (!sc)
 938                 return;
 939         gcry_cipher_close(sc->handle);
 940         free(sc);
 941 }
 942
 943 int sc_send_bin_buffer(struct stream_cipher_context *scc, char *buf,
 944                 size_t size)
 945 {
 946         gcry_error_t gret;
 947         int ret;
 948         unsigned char *tmp = para_malloc(size);
 949
 950         assert(size);
 951         gret = gcry_cipher_encrypt(scc->send->handle, tmp, size,
 952                 (unsigned char *)buf, size);
 953         assert(gret == 0);
 954         ret = write_all(scc->fd, (char *)tmp, &size);
 955         free(tmp);
 956         return ret;
 957 }
 958
 959 int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
 960                 size_t size)
 961 {
 962         gcry_error_t gret;
 963         ssize_t ret = recv(scc->fd, buf, size, 0);
 964
 965         if (ret < 0)
 966                 ret = -ERRNO_TO_PARA_ERROR(errno);
 967         if (ret <= 0)
 968                 return ret;
 969         /* perform in-place encryption */
 970         gret = gcry_cipher_encrypt(scc->recv->handle, (unsigned char *)buf, ret,
 971                 NULL, 0);
 972         assert(gret == 0);
 973         return ret;
 974 }