First cut at PBKDF2.

1 files changed, 171 insertions, 0 deletions

diff --git a/pbkdf2.c b/pbkdf2.c
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+/*
+ * pbkdf2.c
+ * --------
+ * PBKDF2 (RFC 2898) on top of HAL interface to Cryptech hash cores.
+ *
+ * Authors: Rob Austein
+ * Copyright (c) 2015, SUNET
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+
+#include "cryptech.h"
+
+/*
+ * Utility to encapsulate the HMAC operations.  May need refactoring
+ * if and when we get clever about reusing HMAC state for speed.
+ */
+
+static hal_error_t do_hmac(const hal_hash_descriptor_t * const d,
+                           const uint8_t * const pw,   const size_t pw_len,
+                           const uint8_t * const data, const size_t data_len,
+                           const uint32_t  block,
+                                 uint8_t * mac,        const size_t mac_len)
+{
+  assert(d != NULL && pw != NULL && data != NULL && mac != NULL);
+
+  uint8_t sb[d->hmac_state_length];
+  hal_hmac_state_t s;
+  hal_error_t err;
+
+  if ((err = hal_hmac_initialize(d, &s, sb, sizeof(sb), pw, pw_len)) != HAL_OK)
+    return err;
+
+  if ((err = hal_hmac_update(s, data, data_len)) != HAL_OK)
+    return err;
+
+  if (block > 0) {
+    uint8_t b[4] = { (block >> 24) & 0xFF, (block >> 16) & 0xFF, (block >> 8) & 0xFF, (block >> 0) & 0xFF };
+    if ((err = hal_hmac_update(s, b, sizeof(b))) != HAL_OK)
+      return err;
+  }
+
+  return hal_hmac_finalize(s, mac, mac_len);
+}
+
+/*
+ * Derive a key from a passphrase using the PBKDF2 algorithm.
+ */
+
+hal_error_t hal_pbkdf2(const hal_hash_descriptor_t * const descriptor,
+                       const uint8_t * const password, const size_t password_length,
+                       const uint8_t * const salt,     const size_t salt_length,
+                       uint8_t       * derived_key,          size_t derived_key_length,
+                       unsigned iterations_desired)
+{
+  uint8_t statebuf[1024];       /* C99 may let us clean this up */
+  uint32_t block_count;
+
+  if (descriptor == NULL || password == NULL || salt == NULL ||
+      derived_key == NULL || derived_key_length == 0 ||
+      iterations_desired == 0)
+    return HAL_ERROR_BAD_ARGUMENTS;
+
+  assert(sizeof(statebuf) >= descriptor->hmac_state_length);
+
+  /* Output length check per RFC 2989 5.2. */
+  if ((uint64_t) derived_key_length > ((uint64_t) 0xFFFFFFFF) * descriptor->block_length)
+    return HAL_ERROR_UNSUPPORTED_KEY;
+
+  /*
+   * We probably should check here to see whether the password is
+   * longer than the HMAC block size, and, if so, we should hash the
+   * password here to avoid having recomputing that every time through
+   * the loops below.  There are other optimizations we'd like to
+   * make, but this one doesn't require being able to save and restore
+   * the hash state.
+   */
+
+  /*
+   * Generate output blocks until we reach the requested length.
+   */
+
+  for (block_count = 1; ; block_count++) {
+
+    uint8_t accumulator[HAL_MAX_HASH_DIGEST_LENGTH], mac[HAL_MAX_HASH_DIGEST_LENGTH];
+    unsigned iteration;
+    hal_error_t err;
+    int i;
+
+    /*
+     * Initialize the accumulator with the HMAC of the salt
+     * concatenated with the block count.
+     */
+
+    if ((err = do_hmac(descriptor, password, password_length, salt, salt_length,
+                       block_count, accumulator, sizeof(accumulator))) != HAL_OK)
+      return err;
+
+    /*
+     * Now iterate however many times the caller requested, XORing the
+     * result back into the accumulator on each iteration.
+     * Initializing the accumulator counts as iteration 1, so we start
+     * with iteration 2.
+     */
+
+    for (iteration = 2; iteration <= iterations_desired; iteration++) {
+
+      if ((err = do_hmac(descriptor, password, password_length,
+                         accumulator, descriptor->digest_length,
+                         0, mac, sizeof(mac))) != HAL_OK)
+        return err;
+
+      for (i = 0; i < descriptor->digest_length; i++)
+        accumulator[i] ^= mac[i];
+    }
+
+    /*
+     * Accumulator holds the generated block.  Save it, then exit or
+     * loop for another block.
+     */
+
+    if (derived_key_length > descriptor->digest_length) {
+      memcpy(derived_key, accumulator, descriptor->digest_length);
+      derived_key        += descriptor->digest_length;
+      derived_key_length -= descriptor->digest_length;
+    }
+    else {
+      memcpy(derived_key, accumulator, derived_key_length);
+      return HAL_OK;
+    }
+  }
+}
+
+/*
+ * Local variables:
+ * indent-tabs-mode: nil
+ * End:
+ */