crypto/cipher/aes_cbc.c - platform/external/srtp - Git at Google

 /*
  * aes_cbc.c
  *
  * AES Cipher Block Chaining Mode
  *
  * David A. McGrew
  * Cisco Systems, Inc.
  */

 /*
  *
  * Copyright (c) 2001-2006, 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 "aes_cbc.h"
 #include "alloc.h"

 debug_module_t mod_aes_cbc = {
   0,                 /* debugging is off by default */
   "aes cbc"          /* printable module name       */
 };


 err_status_t
 aes_cbc_alloc(cipher_t **c, int key_len) {
   extern cipher_type_t aes_cbc;
   uint8_t *pointer;
   int tmp;

   debug_print(mod_aes_cbc,
 	      "allocating cipher with key length %d", key_len);

   if (key_len != 16)
     return err_status_bad_param;

   /* allocate memory a cipher of type aes_icm */
   tmp = (sizeof(aes_cbc_ctx_t) + sizeof(cipher_t));
   pointer = (uint8_t*)crypto_alloc(tmp);
   if (pointer == NULL)
     return err_status_alloc_fail;

   /* set pointers */
   *c = (cipher_t *)pointer;
   (*c)->type = &aes_cbc;
   (*c)->state = pointer + sizeof(cipher_t);

   /* increment ref_count */
   aes_cbc.ref_count++;

   /* set key size        */
   (*c)->key_len = key_len;

   return err_status_ok;
 }

 err_status_t
 aes_cbc_dealloc(cipher_t *c) {
   extern cipher_type_t aes_cbc;

   /* zeroize entire state*/
   octet_string_set_to_zero((uint8_t *)c,
 			   sizeof(aes_cbc_ctx_t) + sizeof(cipher_t));

   /* free memory */
   crypto_free(c);

   /* decrement ref_count */
   aes_cbc.ref_count--;

   return err_status_ok;
 }

 err_status_t
 aes_cbc_context_init(aes_cbc_ctx_t *c, const uint8_t *key,
 		     cipher_direction_t dir) {
   v128_t tmp_key;

   /* set tmp_key (for alignment) */
   v128_copy_octet_string(&tmp_key, key);

   debug_print(mod_aes_cbc,
 	      "key:  %s", v128_hex_string(&tmp_key));

   /* expand key for the appropriate direction */
   switch (dir) {
   case (direction_encrypt):
     aes_expand_encryption_key(&tmp_key, c->expanded_key);
     break;
   case (direction_decrypt):
     aes_expand_decryption_key(&tmp_key, c->expanded_key);
     break;
   default:
     return err_status_bad_param;
   }


   return err_status_ok;
 }


 err_status_t
 aes_cbc_set_iv(aes_cbc_ctx_t *c, void *iv) {
   int i;
 /*   v128_t *input = iv; */
   uint8_t *input = (uint8_t*) iv;

   /* set state and 'previous' block to iv */
   for (i=0; i < 16; i++)
     c->previous.v8[i] = c->state.v8[i] = input[i];

   debug_print(mod_aes_cbc, "setting iv: %s", v128_hex_string(&c->state));

   return err_status_ok;
 }

 err_status_t
 aes_cbc_encrypt(aes_cbc_ctx_t *c,
 		unsigned char *data,
 		unsigned int *bytes_in_data) {
   int i;
   unsigned char *input  = data;   /* pointer to data being read    */
   unsigned char *output = data;   /* pointer to data being written */
   int bytes_to_encr = *bytes_in_data;

   /*
    * verify that we're 16-octet aligned
    */
   if (*bytes_in_data & 0xf)
     return err_status_bad_param;

   /*
    * note that we assume that the initialization vector has already
    * been set, e.g. by calling aes_cbc_set_iv()
    */
   debug_print(mod_aes_cbc, "iv: %s",
 	      v128_hex_string(&c->state));

   /*
    * loop over plaintext blocks, exoring state into plaintext then
    * encrypting and writing to output
    */
   while (bytes_to_encr > 0) {

     /* exor plaintext into state */
     for (i=0; i < 16; i++)
       c->state.v8[i] ^= *input++;

     debug_print(mod_aes_cbc, "inblock:  %s",
 	      v128_hex_string(&c->state));

     aes_encrypt(&c->state, c->expanded_key);

     debug_print(mod_aes_cbc, "outblock: %s",
 	      v128_hex_string(&c->state));

     /* copy ciphertext to output */
     for (i=0; i < 16; i++)
       *output++ = c->state.v8[i];

     bytes_to_encr -= 16;
   }

   return err_status_ok;
 }

 err_status_t
 aes_cbc_decrypt(aes_cbc_ctx_t *c,
 		unsigned char *data,
 		unsigned int *bytes_in_data) {
   int i;
   v128_t state, previous;
   unsigned char *input  = data;   /* pointer to data being read    */
   unsigned char *output = data;   /* pointer to data being written */
   int bytes_to_encr = *bytes_in_data;
   uint8_t tmp;

   /*
    * verify that we're 16-octet aligned
    */
   if (*bytes_in_data & 0x0f)
     return err_status_bad_param;

   /* set 'previous' block to iv*/
   for (i=0; i < 16; i++) {
     previous.v8[i] = c->previous.v8[i];
   }

   debug_print(mod_aes_cbc, "iv: %s",
 	      v128_hex_string(&previous));

   /*
    * loop over ciphertext blocks, decrypting then exoring with state
    * then writing plaintext to output
    */
   while (bytes_to_encr > 0) {

     /* set state to ciphertext input block */
     for (i=0; i < 16; i++) {
      state.v8[i] = *input++;
     }

     debug_print(mod_aes_cbc, "inblock:  %s",
 	      v128_hex_string(&state));

     /* decrypt state */
     aes_decrypt(&state, c->expanded_key);

     debug_print(mod_aes_cbc, "outblock: %s",
 	      v128_hex_string(&state));

     /*
      * exor previous ciphertext block out of plaintext, and write new
      * plaintext block to output, while copying old ciphertext block
      * to the 'previous' block
      */
     for (i=0; i < 16; i++) {
       tmp = *output;
       *output++ = state.v8[i] ^ previous.v8[i];
       previous.v8[i] = tmp;
     }

     bytes_to_encr -= 16;
   }

   return err_status_ok;
 }


 err_status_t
 aes_cbc_nist_encrypt(aes_cbc_ctx_t *c,
 		     unsigned char *data,
 		     unsigned int *bytes_in_data) {
   int i;
   unsigned char *pad_start;
   int num_pad_bytes;
   err_status_t status;

   /*
    * determine the number of padding bytes that we need to add -
    * this value is always between 1 and 16, inclusive.
    */
   num_pad_bytes = 16 - (*bytes_in_data & 0xf);
   pad_start = data;
   pad_start += *bytes_in_data;
   *pad_start++ = 0xa0;
   for (i=0; i < num_pad_bytes; i++)
     *pad_start++ = 0x00;

   /*
    * increment the data size
    */
   *bytes_in_data += num_pad_bytes;

   /*
    * now cbc encrypt the padded data
    */
   status = aes_cbc_encrypt(c, data, bytes_in_data);
   if (status)
     return status;

   return err_status_ok;
 }


 err_status_t
 aes_cbc_nist_decrypt(aes_cbc_ctx_t *c,
 		     unsigned char *data,
 		     unsigned int *bytes_in_data) {
   unsigned char *pad_end;
   int num_pad_bytes;
   err_status_t status;

   /*
    * cbc decrypt the padded data
    */
   status = aes_cbc_decrypt(c, data, bytes_in_data);
   if (status)
     return status;

   /*
    * determine the number of padding bytes in the decrypted plaintext
    * - this value is always between 1 and 16, inclusive.
    */
   num_pad_bytes = 1;
   pad_end = data + (*bytes_in_data - 1);
   while (*pad_end != 0xa0) {   /* note: should check padding correctness */
     pad_end--;
     num_pad_bytes++;
   }

   /* decrement data size */
   *bytes_in_data -= num_pad_bytes;

   return err_status_ok;
 }


 char
 aes_cbc_description[] = "aes cipher block chaining (cbc) mode";

 /*
  * Test case 0 is derived from FIPS 197 Appendix A; it uses an
  * all-zero IV, so that the first block encryption matches the test
  * case in that appendix.  This property provides a check of the base
  * AES encryption and decryption algorithms; if CBC fails on some
  * particular platform, then you should print out AES intermediate
  * data and compare with the detailed info provided in that appendix.
  *
  */


 uint8_t aes_cbc_test_case_0_key[16] = {
   0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
   0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
 };

 uint8_t aes_cbc_test_case_0_plaintext[64] =  {
   0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
   0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff
 };

 uint8_t aes_cbc_test_case_0_ciphertext[80] = {
   0x69, 0xc4, 0xe0, 0xd8, 0x6a, 0x7b, 0x04, 0x30,
   0xd8, 0xcd, 0xb7, 0x80, 0x70, 0xb4, 0xc5, 0x5a,
   0x03, 0x35, 0xed, 0x27, 0x67, 0xf2, 0x6d, 0xf1,
   0x64, 0x83, 0x2e, 0x23, 0x44, 0x38, 0x70, 0x8b

 };

 uint8_t aes_cbc_test_case_0_iv[16] = {
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };


 cipher_test_case_t aes_cbc_test_case_0 = {
   16,                                    /* octets in key            */
   aes_cbc_test_case_0_key,               /* key                      */
   aes_cbc_test_case_0_iv,                /* initialization vector    */
   16,                                    /* octets in plaintext      */
   aes_cbc_test_case_0_plaintext,         /* plaintext                */
   32,                                    /* octets in ciphertext     */
   aes_cbc_test_case_0_ciphertext,        /* ciphertext               */
   NULL                                   /* pointer to next testcase */
 };


 /*
  * this test case is taken directly from Appendix F.2 of NIST Special
  * Publication SP 800-38A
  */

 uint8_t aes_cbc_test_case_1_key[16] = {
   0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6,
   0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c,
 };

 uint8_t aes_cbc_test_case_1_plaintext[64] =  {
   0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96,
   0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
   0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c,
   0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
   0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11,
   0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
   0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17,
   0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10
 };

 uint8_t aes_cbc_test_case_1_ciphertext[80] = {
   0x76, 0x49, 0xab, 0xac, 0x81, 0x19, 0xb2, 0x46,
   0xce, 0xe9, 0x8e, 0x9b, 0x12, 0xe9, 0x19, 0x7d,
   0x50, 0x86, 0xcb, 0x9b, 0x50, 0x72, 0x19, 0xee,
   0x95, 0xdb, 0x11, 0x3a, 0x91, 0x76, 0x78, 0xb2,
   0x73, 0xbe, 0xd6, 0xb8, 0xe3, 0xc1, 0x74, 0x3b,
   0x71, 0x16, 0xe6, 0x9e, 0x22, 0x22, 0x95, 0x16,
   0x3f, 0xf1, 0xca, 0xa1, 0x68, 0x1f, 0xac, 0x09,
   0x12, 0x0e, 0xca, 0x30, 0x75, 0x86, 0xe1, 0xa7,
   0x39, 0x34, 0x07, 0x03, 0x36, 0xd0, 0x77, 0x99,
   0xe0, 0xc4, 0x2f, 0xdd, 0xa8, 0xdf, 0x4c, 0xa3
 };

 uint8_t aes_cbc_test_case_1_iv[16] = {
   0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
   0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
 };

 cipher_test_case_t aes_cbc_test_case_1 = {
   16,                                    /* octets in key            */
   aes_cbc_test_case_1_key,               /* key                      */
   aes_cbc_test_case_1_iv,                /* initialization vector    */
   64,                                    /* octets in plaintext      */
   aes_cbc_test_case_1_plaintext,         /* plaintext                */
   80,                                    /* octets in ciphertext     */
   aes_cbc_test_case_1_ciphertext,        /* ciphertext               */
   &aes_cbc_test_case_0                    /* pointer to next testcase */
 };

 cipher_type_t aes_cbc = {
   (cipher_alloc_func_t)          aes_cbc_alloc,
   (cipher_dealloc_func_t)        aes_cbc_dealloc,
   (cipher_init_func_t)           aes_cbc_context_init,
   (cipher_encrypt_func_t)        aes_cbc_nist_encrypt,
   (cipher_decrypt_func_t)        aes_cbc_nist_decrypt,
   (cipher_set_iv_func_t)         aes_cbc_set_iv,
   (char *)                       aes_cbc_description,
   (int)                          0,   /* instance count */
   (cipher_test_case_t *)        &aes_cbc_test_case_0,
   (debug_module_t *)            &mod_aes_cbc
 };
	/*
	* aes_cbc.c
	*
	* AES Cipher Block Chaining Mode
	*
	* David A. McGrew
	* Cisco Systems, Inc.
	*/

	/*
	*
	* Copyright (c) 2001-2006, 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 "aes_cbc.h"
	#include "alloc.h"

	debug_module_t mod_aes_cbc = {
	0, /* debugging is off by default */
	"aes cbc" /* printable module name */
	};



	err_status_t
	aes_cbc_alloc(cipher_t **c, int key_len) {
	extern cipher_type_t aes_cbc;
	uint8_t *pointer;
	int tmp;

	debug_print(mod_aes_cbc,
	"allocating cipher with key length %d", key_len);

	if (key_len != 16)
	return err_status_bad_param;

	/* allocate memory a cipher of type aes_icm */
	tmp = (sizeof(aes_cbc_ctx_t) + sizeof(cipher_t));
	pointer = (uint8_t*)crypto_alloc(tmp);
	if (pointer == NULL)
	return err_status_alloc_fail;

	/* set pointers */
	c = (cipher_t )pointer;
	(*c)->type = &aes_cbc;
	(*c)->state = pointer + sizeof(cipher_t);

	/* increment ref_count */
	aes_cbc.ref_count++;

	/* set key size */
	(*c)->key_len = key_len;

	return err_status_ok;
	}

	err_status_t
	aes_cbc_dealloc(cipher_t *c) {
	extern cipher_type_t aes_cbc;

	/* zeroize entire state*/
	octet_string_set_to_zero((uint8_t *)c,
	sizeof(aes_cbc_ctx_t) + sizeof(cipher_t));

	/* free memory */
	crypto_free(c);

	/* decrement ref_count */
	aes_cbc.ref_count--;

	return err_status_ok;
	}

	err_status_t
	aes_cbc_context_init(aes_cbc_ctx_t c, const uint8_t key,
	cipher_direction_t dir) {
	v128_t tmp_key;

	/* set tmp_key (for alignment) */
	v128_copy_octet_string(&tmp_key, key);

	debug_print(mod_aes_cbc,
	"key: %s", v128_hex_string(&tmp_key));

	/* expand key for the appropriate direction */
	switch (dir) {
	case (direction_encrypt):
	aes_expand_encryption_key(&tmp_key, c->expanded_key);
	break;
	case (direction_decrypt):
	aes_expand_decryption_key(&tmp_key, c->expanded_key);
	break;
	default:
	return err_status_bad_param;
	}


	return err_status_ok;
	}


	err_status_t
	aes_cbc_set_iv(aes_cbc_ctx_t c, void iv) {
	int i;
	/* v128_t input = iv; /
	uint8_t input = (uint8_t) iv;

	/* set state and 'previous' block to iv */
	for (i=0; i < 16; i++)
	c->previous.v8[i] = c->state.v8[i] = input[i];

	debug_print(mod_aes_cbc, "setting iv: %s", v128_hex_string(&c->state));

	return err_status_ok;
	}

	err_status_t
	aes_cbc_encrypt(aes_cbc_ctx_t *c,
	unsigned char *data,
	unsigned int *bytes_in_data) {
	int i;
	unsigned char input = data; / pointer to data being read */
	unsigned char output = data; / pointer to data being written */
	int bytes_to_encr = *bytes_in_data;

	/*
	* verify that we're 16-octet aligned
	*/
	if (*bytes_in_data & 0xf)
	return err_status_bad_param;

	/*
	* note that we assume that the initialization vector has already
	* been set, e.g. by calling aes_cbc_set_iv()
	*/
	debug_print(mod_aes_cbc, "iv: %s",
	v128_hex_string(&c->state));

	/*
	* loop over plaintext blocks, exoring state into plaintext then
	* encrypting and writing to output
	*/
	while (bytes_to_encr > 0) {

	/* exor plaintext into state */
	for (i=0; i < 16; i++)
	c->state.v8[i] ^= *input++;

	debug_print(mod_aes_cbc, "inblock: %s",
	v128_hex_string(&c->state));

	aes_encrypt(&c->state, c->expanded_key);

	debug_print(mod_aes_cbc, "outblock: %s",
	v128_hex_string(&c->state));

	/* copy ciphertext to output */
	for (i=0; i < 16; i++)
	*output++ = c->state.v8[i];

	bytes_to_encr -= 16;
	}

	return err_status_ok;
	}

	err_status_t
	aes_cbc_decrypt(aes_cbc_ctx_t *c,
	unsigned char *data,
	unsigned int *bytes_in_data) {
	int i;
	v128_t state, previous;
	unsigned char input = data; / pointer to data being read */
	unsigned char output = data; / pointer to data being written */
	int bytes_to_encr = *bytes_in_data;
	uint8_t tmp;

	/*
	* verify that we're 16-octet aligned
	*/
	if (*bytes_in_data & 0x0f)
	return err_status_bad_param;

	/* set 'previous' block to iv*/
	for (i=0; i < 16; i++) {
	previous.v8[i] = c->previous.v8[i];
	}

	debug_print(mod_aes_cbc, "iv: %s",
	v128_hex_string(&previous));

	/*
	* loop over ciphertext blocks, decrypting then exoring with state
	* then writing plaintext to output
	*/
	while (bytes_to_encr > 0) {

	/* set state to ciphertext input block */
	for (i=0; i < 16; i++) {
	state.v8[i] = *input++;
	}

	debug_print(mod_aes_cbc, "inblock: %s",
	v128_hex_string(&state));

	/* decrypt state */
	aes_decrypt(&state, c->expanded_key);

	debug_print(mod_aes_cbc, "outblock: %s",
	v128_hex_string(&state));

	/*
	* exor previous ciphertext block out of plaintext, and write new
	* plaintext block to output, while copying old ciphertext block
	* to the 'previous' block
	*/
	for (i=0; i < 16; i++) {
	tmp = *output;
	*output++ = state.v8[i] ^ previous.v8[i];
	previous.v8[i] = tmp;
	}

	bytes_to_encr -= 16;
	}

	return err_status_ok;
	}


	err_status_t
	aes_cbc_nist_encrypt(aes_cbc_ctx_t *c,
	unsigned char *data,
	unsigned int *bytes_in_data) {
	int i;
	unsigned char *pad_start;
	int num_pad_bytes;
	err_status_t status;

	/*
	* determine the number of padding bytes that we need to add -
	* this value is always between 1 and 16, inclusive.
	*/
	num_pad_bytes = 16 - (*bytes_in_data & 0xf);
	pad_start = data;
	pad_start += *bytes_in_data;
	*pad_start++ = 0xa0;
	for (i=0; i < num_pad_bytes; i++)
	*pad_start++ = 0x00;

	/*
	* increment the data size
	*/
	*bytes_in_data += num_pad_bytes;

	/*
	* now cbc encrypt the padded data
	*/
	status = aes_cbc_encrypt(c, data, bytes_in_data);
	if (status)
	return status;

	return err_status_ok;
	}


	err_status_t
	aes_cbc_nist_decrypt(aes_cbc_ctx_t *c,
	unsigned char *data,
	unsigned int *bytes_in_data) {
	unsigned char *pad_end;
	int num_pad_bytes;
	err_status_t status;

	/*
	* cbc decrypt the padded data
	*/
	status = aes_cbc_decrypt(c, data, bytes_in_data);
	if (status)
	return status;

	/*
	* determine the number of padding bytes in the decrypted plaintext
	* - this value is always between 1 and 16, inclusive.
	*/
	num_pad_bytes = 1;
	pad_end = data + (*bytes_in_data - 1);
	while (pad_end != 0xa0) { / note: should check padding correctness */
	pad_end--;
	num_pad_bytes++;
	}

	/* decrement data size */
	*bytes_in_data -= num_pad_bytes;

	return err_status_ok;
	}


	char
	aes_cbc_description[] = "aes cipher block chaining (cbc) mode";

	/*
	* Test case 0 is derived from FIPS 197 Appendix A; it uses an
	* all-zero IV, so that the first block encryption matches the test
	* case in that appendix. This property provides a check of the base
	* AES encryption and decryption algorithms; if CBC fails on some
	* particular platform, then you should print out AES intermediate
	* data and compare with the detailed info provided in that appendix.
	*
	*/


	uint8_t aes_cbc_test_case_0_key[16] = {
	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
	};

	uint8_t aes_cbc_test_case_0_plaintext[64] = {
	0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
	0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff
	};

	uint8_t aes_cbc_test_case_0_ciphertext[80] = {
	0x69, 0xc4, 0xe0, 0xd8, 0x6a, 0x7b, 0x04, 0x30,
	0xd8, 0xcd, 0xb7, 0x80, 0x70, 0xb4, 0xc5, 0x5a,
	0x03, 0x35, 0xed, 0x27, 0x67, 0xf2, 0x6d, 0xf1,
	0x64, 0x83, 0x2e, 0x23, 0x44, 0x38, 0x70, 0x8b

	};

	uint8_t aes_cbc_test_case_0_iv[16] = {
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
	};


	cipher_test_case_t aes_cbc_test_case_0 = {
	16, /* octets in key */
	aes_cbc_test_case_0_key, /* key */
	aes_cbc_test_case_0_iv, /* initialization vector */
	16, /* octets in plaintext */
	aes_cbc_test_case_0_plaintext, /* plaintext */
	32, /* octets in ciphertext */
	aes_cbc_test_case_0_ciphertext, /* ciphertext */
	NULL /* pointer to next testcase */
	};


	/*
	* this test case is taken directly from Appendix F.2 of NIST Special
	* Publication SP 800-38A
	*/

	uint8_t aes_cbc_test_case_1_key[16] = {
	0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6,
	0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c,
	};

	uint8_t aes_cbc_test_case_1_plaintext[64] = {
	0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96,
	0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
	0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c,
	0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
	0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11,
	0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
	0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17,
	0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10
	};

	uint8_t aes_cbc_test_case_1_ciphertext[80] = {
	0x76, 0x49, 0xab, 0xac, 0x81, 0x19, 0xb2, 0x46,
	0xce, 0xe9, 0x8e, 0x9b, 0x12, 0xe9, 0x19, 0x7d,
	0x50, 0x86, 0xcb, 0x9b, 0x50, 0x72, 0x19, 0xee,
	0x95, 0xdb, 0x11, 0x3a, 0x91, 0x76, 0x78, 0xb2,
	0x73, 0xbe, 0xd6, 0xb8, 0xe3, 0xc1, 0x74, 0x3b,
	0x71, 0x16, 0xe6, 0x9e, 0x22, 0x22, 0x95, 0x16,
	0x3f, 0xf1, 0xca, 0xa1, 0x68, 0x1f, 0xac, 0x09,
	0x12, 0x0e, 0xca, 0x30, 0x75, 0x86, 0xe1, 0xa7,
	0x39, 0x34, 0x07, 0x03, 0x36, 0xd0, 0x77, 0x99,
	0xe0, 0xc4, 0x2f, 0xdd, 0xa8, 0xdf, 0x4c, 0xa3
	};

	uint8_t aes_cbc_test_case_1_iv[16] = {
	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
	};

	cipher_test_case_t aes_cbc_test_case_1 = {
	16, /* octets in key */
	aes_cbc_test_case_1_key, /* key */
	aes_cbc_test_case_1_iv, /* initialization vector */
	64, /* octets in plaintext */
	aes_cbc_test_case_1_plaintext, /* plaintext */
	80, /* octets in ciphertext */
	aes_cbc_test_case_1_ciphertext, /* ciphertext */
	&aes_cbc_test_case_0 /* pointer to next testcase */
	};

	cipher_type_t aes_cbc = {
	(cipher_alloc_func_t) aes_cbc_alloc,
	(cipher_dealloc_func_t) aes_cbc_dealloc,
	(cipher_init_func_t) aes_cbc_context_init,
	(cipher_encrypt_func_t) aes_cbc_nist_encrypt,
	(cipher_decrypt_func_t) aes_cbc_nist_decrypt,
	(cipher_set_iv_func_t) aes_cbc_set_iv,
	(char *) aes_cbc_description,
	(int) 0, /* instance count */
	(cipher_test_case_t *) &aes_cbc_test_case_0,
	(debug_module_t *) &mod_aes_cbc
	};