1 files changed, 170 insertions, 0 deletions

diff --git a/openbsd-compat/bcrypt_pbkdf.c b/openbsd-compat/bcrypt_pbkdf.c
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+++ b/openbsd-compat/bcrypt_pbkdf.c
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+/* $OpenBSD: bcrypt_pbkdf.c,v 1.4 2013/07/29 00:55:53 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 "includes.h"
+
+#ifndef HAVE_BCRYPT_PBKDF
+
+#include <sys/types.h>
+#include <sys/param.h>
+
+#ifdef HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+#include <string.h>
+
+#ifdef HAVE_BLF_H
+# include <blf.h>
+#endif
+
+#include "crypto_api.h"
+#define SHA512_DIGEST_LENGTH crypto_hash_sha512_BYTES
+
+/*
+ * 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 (i.e.) 512 bits of key material for use as two 256 bit keys, an
+ * attacker can merely run once through the outer loop below, 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_BLOCKS 8
+#define BCRYPT_HASHSIZE (BCRYPT_BLOCKS * 4)
+
+static void
+bcrypt_hash(u_int8_t *sha2pass, u_int8_t *sha2salt, u_int8_t *out)
+{
+        blf_ctx state;
+        u_int8_t ciphertext[BCRYPT_HASHSIZE] =
+            "OxychromaticBlowfishSwatDynamite";
+        uint32_t cdata[BCRYPT_BLOCKS];
+        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_BLOCKS; 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_BLOCKS; 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 */
+        memset(ciphertext, 0, sizeof(ciphertext));
+        memset(cdata, 0, sizeof(cdata));
+        memset(&state, 0, sizeof(state));
+}
+
+int
+bcrypt_pbkdf(const char *pass, size_t passlen, const u_int8_t *salt, size_t saltlen,
+    u_int8_t *key, size_t keylen, unsigned int rounds)
+{
+        u_int8_t sha2pass[SHA512_DIGEST_LENGTH];
+        u_int8_t sha2salt[SHA512_DIGEST_LENGTH];
+        u_int8_t out[BCRYPT_HASHSIZE];
+        u_int8_t tmpout[BCRYPT_HASHSIZE];
+        u_int8_t *countsalt;
+        size_t i, j, amt, stride;
+        uint32_t count;
+
+        /* nothing crazy */
+        if (rounds < 1)
+                return -1;
+        if (passlen == 0 || saltlen == 0 || keylen == 0 ||
+            keylen > sizeof(out) * sizeof(out) || saltlen > 1<<20)
+                return -1;
+        if ((countsalt = calloc(1, saltlen + 4)) == NULL)
+                return -1;
+        stride = (keylen + sizeof(out) - 1) / sizeof(out);
+        amt = (keylen + stride - 1) / stride;
+
+        memcpy(countsalt, salt, saltlen);
+
+        /* collapse password */
+        crypto_hash_sha512(sha2pass, pass, passlen);
+
+        /* generate key, sizeof(out) at a time */
+        for (count = 1; keylen > 0; count++) {
+                countsalt[saltlen + 0] = (count >> 24) & 0xff;
+                countsalt[saltlen + 1] = (count >> 16) & 0xff;
+                countsalt[saltlen + 2] = (count >> 8) & 0xff;
+                countsalt[saltlen + 3] = count & 0xff;
+
+                /* first round, salt is salt */
+                crypto_hash_sha512(sha2salt, countsalt, saltlen + 4);
+
+                bcrypt_hash(sha2pass, sha2salt, tmpout);
+                memcpy(out, tmpout, sizeof(out));
+
+                for (i = 1; i < rounds; i++) {
+                        /* subsequent rounds, salt is previous output */
+                        crypto_hash_sha512(sha2salt, tmpout, sizeof(tmpout));
+                        bcrypt_hash(sha2pass, sha2salt, tmpout);
+                        for (j = 0; j < sizeof(out); j++)
+                                out[j] ^= tmpout[j];
+                }
+
+                /*
+                 * pbkdf2 deviation: ouput the key material non-linearly.
+                 */
+                amt = MIN(amt, keylen);
+                for (i = 0; i < amt; i++)
+                        key[i * stride + (count - 1)] = out[i];
+                keylen -= amt;
+        }
+
+        /* zap */
+        memset(out, 0, sizeof(out));
+        memset(countsalt, 0, saltlen + 4);
+        free(countsalt);
+
+        return 0;
+}
+#endif /* HAVE_BCRYPT_PBKDF */