/* * Implementation of Password-Based Cryptography as per PKCS#5 * Copyright (C) 2002,2003 Simon Josefsson * Copyright (C) 2004 Free Software Foundation * * cryptsetup related changes * Copyright (C) 2012-2024 Red Hat, Inc. All rights reserved. * Copyright (C) 2012-2024 Milan Broz * * This file is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This file is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this file; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. * */ #include #include #include "crypto_backend_internal.h" static int hash_buf(const char *src, size_t src_len, char *dst, size_t dst_len, const char *hash_name) { struct crypt_hash *hd = NULL; int r; if (crypt_hash_init(&hd, hash_name)) return -EINVAL; r = crypt_hash_write(hd, src, src_len); if (!r) r = crypt_hash_final(hd, dst, dst_len); crypt_hash_destroy(hd); return r; } /* * 5.2 PBKDF2 * * PBKDF2 applies a pseudorandom function (see Appendix B.1 for an * example) to derive keys. The length of the derived key is essentially * unbounded. (However, the maximum effective search space for the * derived key may be limited by the structure of the underlying * pseudorandom function. See Appendix B.1 for further discussion.) * PBKDF2 is recommended for new applications. * * PBKDF2 (P, S, c, dkLen) * * Options: PRF underlying pseudorandom function (hLen * denotes the length in octets of the * pseudorandom function output) * * Input: P password, an octet string (ASCII or UTF-8) * S salt, an octet string * c iteration count, a positive integer * dkLen intended length in octets of the derived * key, a positive integer, at most * (2^32 - 1) * hLen * * Output: DK derived key, a dkLen-octet string */ /* * if hash_block_size is not zero, the HMAC key is pre-hashed * inside this function. * This prevents situation when crypto backend doesn't support * long HMAC keys or it tries hash long key in every iteration * (because of crypt_final() cannot do simple key reset. */ #define MAX_PRF_BLOCK_LEN 80 int pkcs5_pbkdf2(const char *hash, const char *P, size_t Plen, const char *S, size_t Slen, unsigned int c, unsigned int dkLen, char *DK, unsigned int hash_block_size) { struct crypt_hmac *hmac; char U[MAX_PRF_BLOCK_LEN]; char T[MAX_PRF_BLOCK_LEN]; char P_hash[MAX_PRF_BLOCK_LEN]; int i, k, rc = -EINVAL; unsigned int u, hLen, l, r; size_t tmplen = Slen + 4; char *tmp; tmp = alloca(tmplen); if (tmp == NULL) return -ENOMEM; hLen = crypt_hmac_size(hash); if (hLen == 0 || hLen > MAX_PRF_BLOCK_LEN) return -EINVAL; if (c == 0) return -EINVAL; if (dkLen == 0) return -EINVAL; /* * * Steps: * * 1. If dkLen > (2^32 - 1) * hLen, output "derived key too long" and * stop. */ if (dkLen > 4294967295U) return -EINVAL; /* * 2. Let l be the number of hLen-octet blocks in the derived key, * rounding up, and let r be the number of octets in the last * block: * * l = CEIL (dkLen / hLen) , * r = dkLen - (l - 1) * hLen . * * Here, CEIL (x) is the "ceiling" function, i.e. the smallest * integer greater than, or equal to, x. */ l = dkLen / hLen; if (dkLen % hLen) l++; r = dkLen - (l - 1) * hLen; /* * 3. For each block of the derived key apply the function F defined * below to the password P, the salt S, the iteration count c, and * the block index to compute the block: * * T_1 = F (P, S, c, 1) , * T_2 = F (P, S, c, 2) , * ... * T_l = F (P, S, c, l) , * * where the function F is defined as the exclusive-or sum of the * first c iterates of the underlying pseudorandom function PRF * applied to the password P and the concatenation of the salt S * and the block index i: * * F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c * * where * * U_1 = PRF (P, S || INT (i)) , * U_2 = PRF (P, U_1) , * ... * U_c = PRF (P, U_{c-1}) . * * Here, INT (i) is a four-octet encoding of the integer i, most * significant octet first. * * 4. Concatenate the blocks and extract the first dkLen octets to * produce a derived key DK: * * DK = T_1 || T_2 || ... || T_l<0..r-1> * * 5. Output the derived key DK. * * Note. The construction of the function F follows a "belt-and- * suspenders" approach. The iterates U_i are computed recursively to * remove a degree of parallelism from an opponent; they are exclusive- * ored together to reduce concerns about the recursion degenerating * into a small set of values. * */ /* If hash_block_size is provided, hash password in advance. */ if (hash_block_size > 0 && Plen > hash_block_size) { if (hash_buf(P, Plen, P_hash, hLen, hash)) return -EINVAL; if (crypt_hmac_init(&hmac, hash, P_hash, hLen)) return -EINVAL; crypt_backend_memzero(P_hash, sizeof(P_hash)); } else { if (crypt_hmac_init(&hmac, hash, P, Plen)) return -EINVAL; } for (i = 1; (unsigned int) i <= l; i++) { memset(T, 0, hLen); for (u = 1; u <= c ; u++) { if (u == 1) { memcpy(tmp, S, Slen); tmp[Slen + 0] = (i & 0xff000000) >> 24; tmp[Slen + 1] = (i & 0x00ff0000) >> 16; tmp[Slen + 2] = (i & 0x0000ff00) >> 8; tmp[Slen + 3] = (i & 0x000000ff) >> 0; if (crypt_hmac_write(hmac, tmp, tmplen)) goto out; } else { if (crypt_hmac_write(hmac, U, hLen)) goto out; } if (crypt_hmac_final(hmac, U, hLen)) goto out; for (k = 0; (unsigned int) k < hLen; k++) T[k] ^= U[k]; } memcpy(DK + (i - 1) * hLen, T, (unsigned int) i == l ? r : hLen); } rc = 0; out: crypt_hmac_destroy(hmac); crypt_backend_memzero(U, sizeof(U)); crypt_backend_memzero(T, sizeof(T)); crypt_backend_memzero(tmp, tmplen); return rc; }