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Diffstat (limited to 'lib/libutil/bcrypt_pbkdf.c')
| -rw-r--r-- | lib/libutil/bcrypt_pbkdf.c | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/lib/libutil/bcrypt_pbkdf.c b/lib/libutil/bcrypt_pbkdf.c new file mode 100644 index 0000000..e937194 --- /dev/null +++ b/lib/libutil/bcrypt_pbkdf.c @@ -0,0 +1,176 @@ +/* $OpenBSD: bcrypt_pbkdf.c,v 1.15 2019/11/21 16:13:39 tedu Exp $ */ +/* + * Copyright (c) 2013 Ted Unangst <tedu@openbsd.org> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#include <sys/types.h> +#include <sys/cdefs.h> + +#include <stdint.h> +#include <stdlib.h> +#include <blf.h> +#include <sha2.h> +#include <string.h> +#include <util.h> + +#define MINIMUM(a,b) (((a) < (b)) ? (a) : (b)) + +/* + * pkcs #5 pbkdf2 implementation using the "bcrypt" hash + * + * The bcrypt hash function is derived from the bcrypt password hashing + * function with the following modifications: + * 1. The input password and salt are preprocessed with SHA512. + * 2. The output length is expanded to 256 bits. + * 3. Subsequently the magic string to be encrypted is lengthened and modifed + * to "OxychromaticBlowfishSwatDynamite" + * 4. The hash function is defined to perform 64 rounds of initial state + * expansion. (More rounds are performed by iterating the hash.) + * + * Note that this implementation pulls the SHA512 operations into the caller + * as a performance optimization. + * + * One modification from official pbkdf2. Instead of outputting key material + * linearly, we mix it. pbkdf2 has a known weakness where if one uses it to + * generate (e.g.) 512 bits of key material for use as two 256 bit keys, an + * attacker can merely run once through the outer loop, but the user + * always runs it twice. Shuffling output bytes requires computing the + * entirety of the key material to assemble any subkey. This is something a + * wise caller could do; we just do it for you. + */ + +#define BCRYPT_WORDS 8 +#define BCRYPT_HASHSIZE (BCRYPT_WORDS * 4) + +static void +bcrypt_hash(uint8_t *sha2pass, uint8_t *sha2salt, uint8_t *out) +{ + blf_ctx state; + uint8_t ciphertext[BCRYPT_HASHSIZE] = + "OxychromaticBlowfishSwatDynamite"; + uint32_t cdata[BCRYPT_WORDS]; + int i; + uint16_t j; + size_t shalen = SHA512_DIGEST_LENGTH; + + /* key expansion */ + Blowfish_initstate(&state); + Blowfish_expandstate(&state, sha2salt, shalen, sha2pass, shalen); + for (i = 0; i < 64; i++) { + Blowfish_expand0state(&state, sha2salt, shalen); + Blowfish_expand0state(&state, sha2pass, shalen); + } + + /* encryption */ + j = 0; + for (i = 0; i < BCRYPT_WORDS; i++) + cdata[i] = Blowfish_stream2word(ciphertext, sizeof(ciphertext), + &j); + for (i = 0; i < 64; i++) + blf_enc(&state, cdata, sizeof(cdata) / sizeof(uint64_t)); + + /* copy out */ + for (i = 0; i < BCRYPT_WORDS; i++) { + out[4 * i + 3] = (cdata[i] >> 24) & 0xff; + out[4 * i + 2] = (cdata[i] >> 16) & 0xff; + out[4 * i + 1] = (cdata[i] >> 8) & 0xff; + out[4 * i + 0] = cdata[i] & 0xff; + } + + /* zap */ + explicit_bzero(ciphertext, sizeof(ciphertext)); + explicit_bzero(cdata, sizeof(cdata)); + explicit_bzero(&state, sizeof(state)); +} + +int +bcrypt_pbkdf(const char *pass, size_t passlen, const uint8_t *salt, size_t saltlen, + uint8_t *key, size_t keylen, unsigned int rounds) +{ + SHA2_CTX ctx; + uint8_t sha2pass[SHA512_DIGEST_LENGTH]; + uint8_t sha2salt[SHA512_DIGEST_LENGTH]; + uint8_t out[BCRYPT_HASHSIZE]; + uint8_t tmpout[BCRYPT_HASHSIZE]; + uint8_t countsalt[4]; + size_t i, j, amt, stride; + uint32_t count; + size_t origkeylen = keylen; + + /* nothing crazy */ + if (rounds < 1) + goto bad; + if (passlen == 0 || saltlen == 0 || keylen == 0 || + keylen > sizeof(out) * sizeof(out)) + goto bad; + stride = (keylen + sizeof(out) - 1) / sizeof(out); + amt = (keylen + stride - 1) / stride; + + /* collapse password */ + SHA512Init(&ctx); + SHA512Update(&ctx, pass, passlen); + SHA512Final(sha2pass, &ctx); + + + /* generate key, sizeof(out) at a time */ + for (count = 1; keylen > 0; count++) { + countsalt[0] = (count >> 24) & 0xff; + countsalt[1] = (count >> 16) & 0xff; + countsalt[2] = (count >> 8) & 0xff; + countsalt[3] = count & 0xff; + + /* first round, salt is salt */ + SHA512Init(&ctx); + SHA512Update(&ctx, salt, saltlen); + SHA512Update(&ctx, countsalt, sizeof(countsalt)); + SHA512Final(sha2salt, &ctx); + bcrypt_hash(sha2pass, sha2salt, tmpout); + memcpy(out, tmpout, sizeof(out)); + + for (i = 1; i < rounds; i++) { + /* subsequent rounds, salt is previous output */ + SHA512Init(&ctx); + SHA512Update(&ctx, tmpout, sizeof(tmpout)); + SHA512Final(sha2salt, &ctx); + bcrypt_hash(sha2pass, sha2salt, tmpout); + for (j = 0; j < sizeof(out); j++) + out[j] ^= tmpout[j]; + } + + /* + * pbkdf2 deviation: output the key material non-linearly. + */ + amt = MINIMUM(amt, keylen); + for (i = 0; i < amt; i++) { + size_t dest = i * stride + (count - 1); + if (dest >= origkeylen) + break; + key[dest] = out[i]; + } + keylen -= i; + } + + /* zap */ + explicit_bzero(&ctx, sizeof(ctx)); + explicit_bzero(out, sizeof(out)); + explicit_bzero(tmpout, sizeof(tmpout)); + + return 0; + +bad: + /* overwrite with random in case caller doesn't check return code */ + arc4random_buf(key, keylen); + return -1; +} |