gcrypt.c

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