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Diffstat (limited to 'src/sshagent/bcrypt_pbkdf.cpp')
| -rw-r--r-- | src/sshagent/bcrypt_pbkdf.cpp | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/src/sshagent/bcrypt_pbkdf.cpp b/src/sshagent/bcrypt_pbkdf.cpp new file mode 100644 index 000000000..fed4cdb29 --- /dev/null +++ b/src/sshagent/bcrypt_pbkdf.cpp @@ -0,0 +1,172 @@ +/* $OpenBSD: bcrypt_pbkdf.c,v 1.13 2015/01/12 03:20:04 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 <QtCore> + +extern "C" { +#include "blf.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) +#define SHA512_DIGEST_LENGTH 64 + +// FIXME: explicit_bzero exists to ensure bzero is not optimized out +#define explicit_bzero bzero + +static void +bcrypt_hash(const quint8* sha2pass, const quint8* sha2salt, quint8* out) +{ + blf_ctx state; + quint8 ciphertext[BCRYPT_HASHSIZE] = // "OxychromaticBlowfishSwatDynamite" + { 0x4f, 0x78, 0x79, 0x63, 0x68, 0x72, 0x6f, 0x6d, + 0x61, 0x74, 0x69, 0x63, 0x42, 0x6c, 0x6f, 0x77, + 0x66, 0x69, 0x73, 0x68, 0x53, 0x77, 0x61, 0x74, + 0x44, 0x79, 0x6e, 0x61, 0x6d, 0x69, 0x74, 0x65 }; + quint32 cdata[BCRYPT_WORDS]; + int i; + quint16 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 QByteArray& pass, const QByteArray& salt, QByteArray& key, quint32 rounds) +{ + QCryptographicHash ctx(QCryptographicHash::Sha512); + QByteArray sha2pass; + QByteArray sha2salt; + quint8 out[BCRYPT_HASHSIZE]; + quint8 tmpout[BCRYPT_HASHSIZE]; + quint8 countsalt[4]; + + /* nothing crazy */ + if (rounds < 1) { + return -1; + } + + if (pass.isEmpty() || salt.isEmpty() || key.isEmpty() || + static_cast<quint32>(key.length()) > sizeof(out) * sizeof(out)) { + return -1; + } + + quint32 stride = (key.length() + sizeof(out) - 1) / sizeof(out); + quint32 amt = (key.length() + stride - 1) / stride; + + /* collapse password */ + ctx.reset(); + ctx.addData(pass); + sha2pass = ctx.result(); + + /* generate key, sizeof(out) at a time */ + for (quint32 count = 1, keylen = key.length(); 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 */ + ctx.reset(); + ctx.addData(salt); + ctx.addData(reinterpret_cast<char *>(countsalt), sizeof(countsalt)); + sha2salt = ctx.result(); + + bcrypt_hash(reinterpret_cast<quint8 *>(sha2pass.data()), reinterpret_cast<quint8 *>(sha2salt.data()), tmpout); + memcpy(out, tmpout, sizeof(out)); + + for (quint32 i = 1; i < rounds; i++) { + /* subsequent rounds, salt is previous output */ + ctx.reset(); + ctx.addData(reinterpret_cast<char *>(tmpout), sizeof(tmpout)); + sha2salt = ctx.result(); + bcrypt_hash(reinterpret_cast<quint8 *>(sha2pass.data()), reinterpret_cast<quint8 *>(sha2salt.data()), tmpout); + for (quint32 j = 0; j < sizeof(out); j++) + out[j] ^= tmpout[j]; + } + + /* + * pbkdf2 deviation: output the key material non-linearly. + */ + amt = MINIMUM(amt, keylen); + quint32 i; + for (i = 0; i < amt; i++) { + int dest = i * stride + (count - 1); + if (dest >= key.length()) + break; + key.data()[dest] = out[i]; + } + keylen -= i; + } + + /* zap */ + explicit_bzero(out, sizeof(out)); + + return 0; +} |