michael@0: /*
michael@0:  * xfm.c
michael@0:  *
michael@0:  * Crypto transform implementation
michael@0:  *
michael@0:  * David A. McGrew
michael@0:  * Cisco Systems, Inc.
michael@0:  */
michael@0: /*
michael@0:  *	
michael@0:  * Copyright (c) 2001-2006, Cisco Systems, Inc.
michael@0:  * All rights reserved.
michael@0:  * 
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  * 
michael@0:  *   Redistributions of source code must retain the above copyright
michael@0:  *   notice, this list of conditions and the following disclaimer.
michael@0:  * 
michael@0:  *   Redistributions in binary form must reproduce the above
michael@0:  *   copyright notice, this list of conditions and the following
michael@0:  *   disclaimer in the documentation and/or other materials provided
michael@0:  *   with the distribution.
michael@0:  * 
michael@0:  *   Neither the name of the Cisco Systems, Inc. nor the names of its
michael@0:  *   contributors may be used to endorse or promote products derived
michael@0:  *   from this software without specific prior written permission.
michael@0:  * 
michael@0:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
michael@0:  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
michael@0:  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
michael@0:  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
michael@0:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
michael@0:  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
michael@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
michael@0:  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
michael@0:  * OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: #include "cryptoalg.h"
michael@0: #include "aes_cbc.h"
michael@0: #include "hmac.h"
michael@0: #include "crypto_kernel.h"   /* for crypto_get_random() */
michael@0: 
michael@0: #define KEY_LEN     16
michael@0: #define ENC_KEY_LEN 16
michael@0: #define MAC_KEY_LEN 16
michael@0: #define IV_LEN      16
michael@0: #define TAG_LEN     12
michael@0: #define MAX_EXPAND  27
michael@0: 
michael@0: err_status_t
michael@0: aes_128_cbc_hmac_sha1_96_func(void *key,            
michael@0: 			      void *clear,          
michael@0: 			      unsigned clear_len,       
michael@0: 			      void *iv,             
michael@0: 			      void *opaque,         
michael@0: 			      unsigned *opaque_len, 
michael@0: 			      void *auth_tag) {
michael@0:   aes_cbc_ctx_t aes_ctx;
michael@0:   hmac_ctx_t hmac_ctx;
michael@0:   unsigned char enc_key[ENC_KEY_LEN];
michael@0:   unsigned char mac_key[MAC_KEY_LEN];
michael@0:   err_status_t status;
michael@0: 
michael@0:   /* check if we're doing authentication only */
michael@0:   if ((iv == NULL) && (opaque == NULL) && (opaque_len == NULL)) {
michael@0:       
michael@0:       /* perform authentication only */
michael@0: 
michael@0:   } else if ((iv == NULL) || (opaque == NULL) || (opaque_len == NULL)) {
michael@0:     
michael@0:     /*
michael@0:      * bad parameter - we expect either all three pointers to be NULL,
michael@0:      * or none of those pointers to be NULL 
michael@0:      */
michael@0:     return err_status_fail;
michael@0: 
michael@0:   } else {
michael@0: 
michael@0:     /* derive encryption and authentication keys from the input key */
michael@0:     status = hmac_init(&hmac_ctx, key, KEY_LEN);
michael@0:     if (status) return status;
michael@0:     status = hmac_compute(&hmac_ctx, "ENC", 3, ENC_KEY_LEN, enc_key);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_init(&hmac_ctx, key, KEY_LEN);
michael@0:     if (status) return status;
michael@0:     status = hmac_compute(&hmac_ctx, "MAC", 3, MAC_KEY_LEN, mac_key);
michael@0:     if (status) return status;
michael@0: 
michael@0: 
michael@0:     /* perform encryption and authentication */
michael@0: 
michael@0:     /* set aes key */
michael@0:     status = aes_cbc_context_init(&aes_ctx, key, ENC_KEY_LEN, direction_encrypt);
michael@0:     if (status) return status;
michael@0: 
michael@0:     /* set iv */
michael@0:     status = crypto_get_random(iv, IV_LEN);  
michael@0:     if (status) return status; 
michael@0:     status = aes_cbc_set_iv(&aes_ctx, iv);
michael@0:     
michael@0:     /* encrypt the opaque data  */
michael@0:     status = aes_cbc_nist_encrypt(&aes_ctx, opaque, opaque_len);
michael@0:     if (status) return status;
michael@0: 
michael@0:     /* authenticate clear and opaque data */
michael@0:     status = hmac_init(&hmac_ctx, mac_key, MAC_KEY_LEN);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_start(&hmac_ctx);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_update(&hmac_ctx, clear, clear_len);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_compute(&hmac_ctx, opaque, *opaque_len, TAG_LEN, auth_tag);
michael@0:     if (status) return status;
michael@0: 
michael@0:   }
michael@0: 
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: err_status_t
michael@0: aes_128_cbc_hmac_sha1_96_inv(void *key,            
michael@0: 			     void *clear,          
michael@0: 			     unsigned clear_len,       
michael@0: 			     void *iv,             
michael@0: 			     void *opaque,         
michael@0: 			     unsigned *opaque_len, 
michael@0: 			     void *auth_tag) {
michael@0:   aes_cbc_ctx_t aes_ctx;
michael@0:   hmac_ctx_t hmac_ctx;
michael@0:   unsigned char enc_key[ENC_KEY_LEN];
michael@0:   unsigned char mac_key[MAC_KEY_LEN];
michael@0:   unsigned char tmp_tag[TAG_LEN];
michael@0:   unsigned char *tag = auth_tag;
michael@0:   err_status_t status;
michael@0:   int i;
michael@0:   
michael@0:   /* check if we're doing authentication only */
michael@0:   if ((iv == NULL) && (opaque == NULL) && (opaque_len == NULL)) {
michael@0:       
michael@0:       /* perform authentication only */
michael@0: 
michael@0:   } else if ((iv == NULL) || (opaque == NULL) || (opaque_len == NULL)) {
michael@0:     
michael@0:     /*
michael@0:      * bad parameter - we expect either all three pointers to be NULL,
michael@0:      * or none of those pointers to be NULL 
michael@0:      */
michael@0:     return err_status_fail;
michael@0: 
michael@0:   } else {
michael@0: 
michael@0:     /* derive encryption and authentication keys from the input key */
michael@0:     status = hmac_init(&hmac_ctx, key, KEY_LEN);
michael@0:     if (status) return status;
michael@0:     status = hmac_compute(&hmac_ctx, "ENC", 3, ENC_KEY_LEN, enc_key);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_init(&hmac_ctx, key, KEY_LEN);
michael@0:     if (status) return status;
michael@0:     status = hmac_compute(&hmac_ctx, "MAC", 3, MAC_KEY_LEN, mac_key);
michael@0:     if (status) return status;
michael@0: 
michael@0:     /* perform encryption and authentication */
michael@0: 
michael@0:     /* set aes key */
michael@0:     status = aes_cbc_context_init(&aes_ctx, key, ENC_KEY_LEN, direction_decrypt);
michael@0:     if (status) return status;
michael@0: 
michael@0:     /* set iv */
michael@0:     status = rand_source_get_octet_string(iv, IV_LEN);  
michael@0:     if (status) return status; 
michael@0:     status = aes_cbc_set_iv(&aes_ctx, iv);
michael@0:     
michael@0:     /* encrypt the opaque data  */
michael@0:     status = aes_cbc_nist_decrypt(&aes_ctx, opaque, opaque_len);
michael@0:     if (status) return status;
michael@0: 
michael@0:     /* authenticate clear and opaque data */
michael@0:     status = hmac_init(&hmac_ctx, mac_key, MAC_KEY_LEN);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_start(&hmac_ctx);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_update(&hmac_ctx, clear, clear_len);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_compute(&hmac_ctx, opaque, *opaque_len, TAG_LEN, tmp_tag);
michael@0:     if (status) return status;
michael@0: 
michael@0:     /* compare the computed tag with the one provided as input */
michael@0:     for (i=0; i < TAG_LEN; i++)
michael@0:       if (tmp_tag[i] != tag[i]) 
michael@0: 	return err_status_auth_fail; 
michael@0: 
michael@0:   }
michael@0: 
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: 
michael@0: #define ENC 1
michael@0: 
michael@0: #define DEBUG 0
michael@0: 
michael@0: err_status_t
michael@0: aes_128_cbc_hmac_sha1_96_enc(void *key,            
michael@0: 			     const void *clear,          
michael@0: 			     unsigned clear_len,       
michael@0: 			     void *iv,             
michael@0: 			     void *opaque,         
michael@0: 			     unsigned *opaque_len) {
michael@0:   aes_cbc_ctx_t aes_ctx;
michael@0:   hmac_ctx_t hmac_ctx;
michael@0:   unsigned char enc_key[ENC_KEY_LEN];
michael@0:   unsigned char mac_key[MAC_KEY_LEN];
michael@0:   unsigned char *auth_tag;
michael@0:   err_status_t status;
michael@0: 
michael@0:   /* check if we're doing authentication only */
michael@0:   if ((iv == NULL) && (opaque == NULL) && (opaque_len == NULL)) {
michael@0:       
michael@0:       /* perform authentication only */
michael@0: 
michael@0:   } else if ((iv == NULL) || (opaque == NULL) || (opaque_len == NULL)) {
michael@0:     
michael@0:     /*
michael@0:      * bad parameter - we expect either all three pointers to be NULL,
michael@0:      * or none of those pointers to be NULL 
michael@0:      */
michael@0:     return err_status_fail;
michael@0: 
michael@0:   } else {
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("ENC using key %s\n", octet_string_hex_string(key, KEY_LEN));
michael@0: #endif
michael@0: 
michael@0:     /* derive encryption and authentication keys from the input key */
michael@0:     status = hmac_init(&hmac_ctx, key, KEY_LEN);
michael@0:     if (status) return status;
michael@0:     status = hmac_compute(&hmac_ctx, "ENC", 3, ENC_KEY_LEN, enc_key);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_init(&hmac_ctx, key, KEY_LEN);
michael@0:     if (status) return status;
michael@0:     status = hmac_compute(&hmac_ctx, "MAC", 3, MAC_KEY_LEN, mac_key);
michael@0:     if (status) return status;
michael@0: 
michael@0: 
michael@0:     /* perform encryption and authentication */
michael@0: 
michael@0:     /* set aes key */
michael@0:     status = aes_cbc_context_init(&aes_ctx, key, ENC_KEY_LEN, direction_encrypt);
michael@0:     if (status) return status;
michael@0: 
michael@0:     /* set iv */
michael@0:     status = rand_source_get_octet_string(iv, IV_LEN);  
michael@0:     if (status) return status; 
michael@0:     status = aes_cbc_set_iv(&aes_ctx, iv);
michael@0:     if (status) return status;
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("plaintext len:  %d\n", *opaque_len);
michael@0:     printf("iv:         %s\n", octet_string_hex_string(iv, IV_LEN));
michael@0:     printf("plaintext:  %s\n", octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0: 
michael@0: #if ENC    
michael@0:     /* encrypt the opaque data  */
michael@0:     status = aes_cbc_nist_encrypt(&aes_ctx, opaque, opaque_len);
michael@0:     if (status) return status;
michael@0: #endif
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("ciphertext len: %d\n", *opaque_len);
michael@0:     printf("ciphertext: %s\n", octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0: 
michael@0:     /*
michael@0:      * authenticate clear and opaque data, then write the
michael@0:      * authentication tag to the location immediately following the
michael@0:      * ciphertext
michael@0:      */
michael@0:     status = hmac_init(&hmac_ctx, mac_key, MAC_KEY_LEN);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_start(&hmac_ctx);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_update(&hmac_ctx, clear, clear_len);
michael@0:     if (status) return status;
michael@0: #if DEBUG
michael@0:     printf("hmac input: %s\n", 
michael@0: 	   octet_string_hex_string(clear, clear_len));
michael@0: #endif
michael@0:     auth_tag = (unsigned char *)opaque;
michael@0:     auth_tag += *opaque_len;    
michael@0:     status = hmac_compute(&hmac_ctx, opaque, *opaque_len, TAG_LEN, auth_tag);
michael@0:     if (status) return status;
michael@0: #if DEBUG
michael@0:     printf("hmac input: %s\n", 
michael@0: 	   octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0:     /* bump up the opaque_len to reflect the authentication tag */
michael@0:     *opaque_len += TAG_LEN;
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("prot data len:  %d\n", *opaque_len);
michael@0:     printf("prot data: %s\n", octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0:   }
michael@0: 
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: err_status_t
michael@0: aes_128_cbc_hmac_sha1_96_dec(void *key,            
michael@0: 			     const void *clear,          
michael@0: 			     unsigned clear_len,       
michael@0: 			     void *iv,             
michael@0: 			     void *opaque,         
michael@0: 			     unsigned *opaque_len) {
michael@0:   aes_cbc_ctx_t aes_ctx;
michael@0:   hmac_ctx_t hmac_ctx;
michael@0:   unsigned char enc_key[ENC_KEY_LEN];
michael@0:   unsigned char mac_key[MAC_KEY_LEN];
michael@0:   unsigned char tmp_tag[TAG_LEN];
michael@0:   unsigned char *auth_tag;
michael@0:   unsigned ciphertext_len;
michael@0:   err_status_t status;
michael@0:   int i;
michael@0:   
michael@0:   /* check if we're doing authentication only */
michael@0:   if ((iv == NULL) && (opaque == NULL) && (opaque_len == NULL)) {
michael@0:       
michael@0:       /* perform authentication only */
michael@0: 
michael@0:   } else if ((iv == NULL) || (opaque == NULL) || (opaque_len == NULL)) {
michael@0:     
michael@0:     /*
michael@0:      * bad parameter - we expect either all three pointers to be NULL,
michael@0:      * or none of those pointers to be NULL 
michael@0:      */
michael@0:     return err_status_fail;
michael@0: 
michael@0:   } else {
michael@0: #if DEBUG
michael@0:     printf("DEC using key %s\n", octet_string_hex_string(key, KEY_LEN));
michael@0: #endif
michael@0: 
michael@0:     /* derive encryption and authentication keys from the input key */
michael@0:     status = hmac_init(&hmac_ctx, key, KEY_LEN);
michael@0:     if (status) return status;
michael@0:     status = hmac_compute(&hmac_ctx, "ENC", 3, ENC_KEY_LEN, enc_key);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_init(&hmac_ctx, key, KEY_LEN);
michael@0:     if (status) return status;
michael@0:     status = hmac_compute(&hmac_ctx, "MAC", 3, MAC_KEY_LEN, mac_key);
michael@0:     if (status) return status;
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("prot data len:  %d\n", *opaque_len);
michael@0:     printf("prot data: %s\n", octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0: 
michael@0:     /* 
michael@0:      * set the protected data length to that of the ciphertext, by
michael@0:      * subtracting out the length of the authentication tag 
michael@0:      */
michael@0:     ciphertext_len = *opaque_len - TAG_LEN;
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("ciphertext len: %d\n", ciphertext_len);
michael@0: #endif    
michael@0:     /* verify the authentication tag */
michael@0: 
michael@0:     /* 
michael@0:      * compute the authentication tag for the clear and opaque data,
michael@0:      * and write it to a temporary location
michael@0:      */
michael@0:     status = hmac_init(&hmac_ctx, mac_key, MAC_KEY_LEN);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_start(&hmac_ctx);
michael@0:     if (status) return status;
michael@0: 
michael@0:     status = hmac_update(&hmac_ctx, clear, clear_len);
michael@0:     if (status) return status;
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("hmac input: %s\n", 
michael@0: 	   octet_string_hex_string(clear, clear_len));
michael@0: #endif
michael@0: 
michael@0:     status = hmac_compute(&hmac_ctx, opaque, ciphertext_len, TAG_LEN, tmp_tag);
michael@0:     if (status) return status;
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("hmac input: %s\n", 
michael@0: 	   octet_string_hex_string(opaque, ciphertext_len));
michael@0: #endif
michael@0: 
michael@0:     /* 
michael@0:      * compare the computed tag with the one provided as input (which
michael@0:      * immediately follows the ciphertext)
michael@0:      */
michael@0:     auth_tag = (unsigned char *)opaque;
michael@0:     auth_tag += ciphertext_len;  
michael@0: #if DEBUG
michael@0:     printf("auth_tag: %s\n", octet_string_hex_string(auth_tag, TAG_LEN));
michael@0:     printf("tmp_tag:  %s\n", octet_string_hex_string(tmp_tag, TAG_LEN));
michael@0: #endif
michael@0:     for (i=0; i < TAG_LEN; i++) {
michael@0:       if (tmp_tag[i] != auth_tag[i]) 
michael@0: 	return err_status_auth_fail; 
michael@0:     }
michael@0: 
michael@0:     /* bump down the opaque_len to reflect the authentication tag */
michael@0:     *opaque_len -= TAG_LEN;
michael@0: 
michael@0:     /* decrypt the confidential data */
michael@0:     status = aes_cbc_context_init(&aes_ctx, key, ENC_KEY_LEN, direction_decrypt);
michael@0:     if (status) return status;
michael@0:     status = aes_cbc_set_iv(&aes_ctx, iv);
michael@0:     if (status) return status;
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("ciphertext: %s\n", octet_string_hex_string(opaque, *opaque_len));
michael@0:     printf("iv:         %s\n", octet_string_hex_string(iv, IV_LEN));
michael@0: #endif
michael@0: 
michael@0: #if ENC
michael@0:     status = aes_cbc_nist_decrypt(&aes_ctx, opaque, &ciphertext_len);
michael@0:     if (status) return status;
michael@0: #endif
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("plaintext len:  %d\n", ciphertext_len);
michael@0:     printf("plaintext:  %s\n", 
michael@0: 	   octet_string_hex_string(opaque, ciphertext_len));
michael@0: #endif
michael@0: 
michael@0:     /* indicate the length of the plaintext  */
michael@0:     *opaque_len = ciphertext_len;
michael@0:   }
michael@0: 
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: cryptoalg_ctx_t cryptoalg_ctx = {
michael@0:   aes_128_cbc_hmac_sha1_96_enc,
michael@0:   aes_128_cbc_hmac_sha1_96_dec,
michael@0:   KEY_LEN,
michael@0:   IV_LEN,
michael@0:   TAG_LEN,
michael@0:   MAX_EXPAND,
michael@0: };
michael@0: 
michael@0: cryptoalg_t cryptoalg = &cryptoalg_ctx;
michael@0: 
michael@0: #define NULL_TAG_LEN 12
michael@0: 
michael@0: err_status_t
michael@0: null_enc(void *key,            
michael@0: 	 const void *clear,          
michael@0: 	 unsigned clear_len,       
michael@0: 	 void *iv,             
michael@0: 	 void *opaque,         
michael@0: 	 unsigned *opaque_len) {
michael@0:   int i;
michael@0:   unsigned char *auth_tag;
michael@0:   unsigned char *init_vec = iv;
michael@0: 
michael@0:   /* check if we're doing authentication only */
michael@0:   if ((iv == NULL) && (opaque == NULL) && (opaque_len == NULL)) {
michael@0:       
michael@0:       /* perform authentication only */
michael@0: 
michael@0:   } else if ((iv == NULL) || (opaque == NULL) || (opaque_len == NULL)) {
michael@0:     
michael@0:     /*
michael@0:      * bad parameter - we expect either all three pointers to be NULL,
michael@0:      * or none of those pointers to be NULL 
michael@0:      */
michael@0:     return err_status_fail;
michael@0: 
michael@0:   } else {
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("NULL ENC using key %s\n", octet_string_hex_string(key, KEY_LEN));
michael@0:     printf("NULL_TAG_LEN:  %d\n", NULL_TAG_LEN);
michael@0:     printf("plaintext len:  %d\n", *opaque_len);
michael@0: #endif
michael@0:     for (i=0; i < IV_LEN; i++)
michael@0:       init_vec[i] = i + (i * 16);
michael@0: #if DEBUG
michael@0:     printf("iv:                %s\n", 
michael@0: 	   octet_string_hex_string(iv, IV_LEN));
michael@0:     printf("plaintext:         %s\n", 
michael@0: 	   octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0:     auth_tag = opaque;
michael@0:     auth_tag += *opaque_len;
michael@0:     for (i=0; i < NULL_TAG_LEN; i++)
michael@0:       auth_tag[i] = i + (i * 16);
michael@0:     *opaque_len += NULL_TAG_LEN;
michael@0: #if DEBUG
michael@0:     printf("protected data len: %d\n", *opaque_len);
michael@0:     printf("protected data:    %s\n", 
michael@0: 	   octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0: 
michael@0:   }
michael@0: 
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: err_status_t
michael@0: null_dec(void *key,            
michael@0: 	 const void *clear,          
michael@0: 	 unsigned clear_len,       
michael@0: 	 void *iv,             
michael@0: 	 void *opaque,         
michael@0: 	 unsigned *opaque_len) {
michael@0:   unsigned char *auth_tag;
michael@0:   
michael@0:   /* check if we're doing authentication only */
michael@0:   if ((iv == NULL) && (opaque == NULL) && (opaque_len == NULL)) {
michael@0:       
michael@0:       /* perform authentication only */
michael@0: 
michael@0:   } else if ((iv == NULL) || (opaque == NULL) || (opaque_len == NULL)) {
michael@0:     
michael@0:     /*
michael@0:      * bad parameter - we expect either all three pointers to be NULL,
michael@0:      * or none of those pointers to be NULL 
michael@0:      */
michael@0:     return err_status_fail;
michael@0: 
michael@0:   } else {
michael@0: 
michael@0: #if DEBUG
michael@0:     printf("NULL DEC using key %s\n", octet_string_hex_string(key, KEY_LEN));
michael@0: 
michael@0:     printf("protected data len: %d\n", *opaque_len);
michael@0:     printf("protected data:    %s\n", 
michael@0: 	   octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0:     auth_tag = opaque;
michael@0:     auth_tag += (*opaque_len - NULL_TAG_LEN);
michael@0: #if DEBUG
michael@0:     printf("iv:         %s\n", octet_string_hex_string(iv, IV_LEN));
michael@0: #endif
michael@0:     *opaque_len -= NULL_TAG_LEN;
michael@0: #if DEBUG
michael@0:     printf("plaintext len:  %d\n", *opaque_len);
michael@0:     printf("plaintext:  %s\n", 
michael@0: 	   octet_string_hex_string(opaque, *opaque_len));
michael@0: #endif
michael@0:   }
michael@0: 
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: cryptoalg_ctx_t null_cryptoalg_ctx = {
michael@0:   null_enc,
michael@0:   null_dec,
michael@0:   KEY_LEN,
michael@0:   IV_LEN,
michael@0:   NULL_TAG_LEN,
michael@0:   MAX_EXPAND,
michael@0: };
michael@0: 
michael@0: cryptoalg_t null_cryptoalg = &null_cryptoalg_ctx;
michael@0: 
michael@0: int
michael@0: cryptoalg_get_id(cryptoalg_t c) {
michael@0:   if (c == cryptoalg)
michael@0:     return 1;
michael@0:   return 0;
michael@0: }
michael@0: 
michael@0: cryptoalg_t 
michael@0: cryptoalg_find_by_id(int id) {
michael@0:   switch(id) {
michael@0:   case 1:
michael@0:     return cryptoalg;
michael@0:   default:
michael@0:     break;
michael@0:   }
michael@0:   return 0;
michael@0: }