cipher.c

srtp-1.3.20 security RTP source

/*
 * cipher.c
 *
 * cipher meta-functions
 *
 * David A. McGrew
 * Cisco Systems, Inc.
 * 
 */

/*
 *	
 * Copyright (c) 2001-2004, Cisco Systems, Inc.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 *   Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * 
 *   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.
 * 
 *   Neither the name of the Cisco Systems, Inc. nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 * 
 * 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 HOLDERS 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 "cipher.h"
#include "alloc.h"              /* for xalloc(), xfree() */
#include <time.h>               /* for clock()           */

debug_module_t mod_cipher = {
  0,                 /* debugging is off by default */
  "cipher"           /* printable module name       */
};

inline err_status_t
cipher_output(cipher_t *c, octet_t *buffer, int num_octets_to_output) {
  
  /* zeroize the buffer */
  octet_string_set_to_zero(buffer, num_octets_to_output);
  
  /* exor keystream into buffer */
  return cipher_encrypt(c, buffer, &num_octets_to_output);
}

/* some bookkeeping functions */

int
cipher_get_key_length(const cipher_t *c) {
  return c->key_len;
}

/* 
 * cipher_type_self_test(ct) tests a cipher of type ct against test cases
 * provided in an array of values of key, salt, xtd_seq_num_t,
 * plaintext, and ciphertext that is known to be good
 */

#define SELF_TEST_BUF_OCTETS 64

err_status_t
cipher_type_self_test(const cipher_type_t *ct) {
  const cipher_test_case_t *test_case = ct->test_data;
  cipher_t *c;
  err_status_t status;
  octet_t buffer[SELF_TEST_BUF_OCTETS];
  unsigned int len;
  int i, case_num = 0;

  debug_print(mod_cipher, "running self-test for cipher %s", 
	      ct->description);
  
  /*
   * check to make sure that we have at least one test case, and
   * return an error if we don't - we need to be paranoid here
   */
  if (test_case == NULL)
    return err_status_cant_check;

  /* loop over all test cases */  
  while (test_case != NULL) {

    /* allocate cipher */
    status = cipher_type_alloc(ct, &c, test_case->key_length_octets);
    if (status)
      return status;
    
    /* initialize cipher */
    status = cipher_init(c, test_case->key);
    if (status) {
      cipher_dealloc(c);
      return status;
    }
    
    /* copy plaintext into test buffer */
    if (test_case->plaintext_length_octets > SELF_TEST_BUF_OCTETS) {
      cipher_dealloc(c);    
      return err_status_bad_param;
    }
    for (i=0; i < test_case->plaintext_length_octets; i++)
      buffer[i] = test_case->plaintext[i];

    debug_print(mod_cipher, "plaintext:    %s",
	     octet_string_hex_string(buffer,
				     test_case->plaintext_length_octets));

    /* set the segment index */
    status = cipher_set_iv(c, test_case->idx);
    if (status) {
      cipher_dealloc(c);
      return status;
    } 
    
    /* encrypt */
    len = test_case->plaintext_length_octets;
    status = cipher_encrypt(c, buffer, &len);
    if (status) {
      cipher_dealloc(c);
      return status;
    }
    
    debug_print(mod_cipher, "ciphertext:   %s",
	     octet_string_hex_string(buffer,
				     test_case->plaintext_length_octets));

    /* compare the resulting ciphertext with that in the test case */
    status = err_status_ok;
    for (i=0; i < test_case->plaintext_length_octets; i++)
      if (buffer[i] != test_case->ciphertext[i]) {
	status = err_status_algo_fail;
	debug_print(mod_cipher, "test case %d failed", case_num);
	debug_print(mod_cipher, "(failure at byte %d)", i);
      }
    if (status) {

      debug_print(mod_cipher, "c computed: %s",
	     octet_string_hex_string(buffer,
		  2*test_case->plaintext_length_octets));
      debug_print(mod_cipher, "c expected: %s",
		  octet_string_hex_string(test_case->ciphertext,
			  2*test_case->plaintext_length_octets));

      cipher_dealloc(c);
      return err_status_algo_fail;
    }

    /* deallocate the cipher */
    status = cipher_dealloc(c);
    if (status)
      return status;
    
    /* 
     * the cipher passed the test case, so move on to the next test
     * case in the list; if NULL, we'll quit and return an OK
     */   
    test_case = test_case->next_test_case;
    ++case_num;
  }
  
  return err_status_ok;
}


/*
 * cipher_bits_per_second(c, l, t) computes (an estimate of) the
 * number of bits that a cipher implementation can encrypt in a second
 * 
 * c is a cipher (which MUST be allocated and initialized already), l
 * is the length in octets of the test data to be encrypted, and t is
 * the number of trials
 *
 * if an error is encountered, the value 0.0 is returned
 */

double
cipher_bits_per_second(cipher_t *c, int octets_in_buffer, int num_trials) {
  int i;
  v128_t nonce;
  clock_t timer;
  unsigned char *enc_buf;
  unsigned int len = octets_in_buffer;

  enc_buf = xalloc(octets_in_buffer);
  if (enc_buf == NULL)
    return 0.0;  /* indicate bad parameters by returning null */
  
  /* time repeated trials */
  v128_set_to_zero(&nonce);
  timer = clock();
  for(i=0; i < num_trials; i++, nonce.v32[3] = i) {
    cipher_set_iv(c, &nonce);
    cipher_encrypt(c, enc_buf, &len);
  }
  timer = clock() - timer;

  xfree(enc_buf);
  
  return (double) CLOCKS_PER_SEC * num_trials
    * 8 * octets_in_buffer / timer;
}