text: /*
   * aes_icm.c
   *
   * AES Integer Counter Mode
   *
   * David A. McGrew
   * Cisco Systems, Inc.
   */
  
  /*
   *	
   * Copyright (c) 2001-2006,2013 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.
   *
   */
  
  
  #define ALIGN_32 0
  
  #include "aes_icm.h"
  #include "alloc.h"
  
  
  debug_module_t mod_aes_icm = {
    0,                 /* debugging is off by default */
    "aes icm"          /* printable module name       */
  };
  
  /*
   * integer counter mode works as follows:
   *
   * 16 bits
   * <----->
   * +------+------+------+------+------+------+------+------+ 
   * |           nonce           |    pakcet index    |  ctr |---+
   * +------+------+------+------+------+------+------+------+   |
   *                                                             |
   * +------+------+------+------+------+------+------+------+   v
   * |                      salt                      |000000|->(+)
   * +------+------+------+------+------+------+------+------+   |
   *                                                             |
   *                                                        +---------+
   *							  | encrypt |
   *							  +---------+
   *							       | 
   * +------+------+------+------+------+------+------+------+   |
   * |                    keystream block                    |<--+ 
   * +------+------+------+------+------+------+------+------+   
   *
   * All fields are big-endian
   *
   * ctr is the block counter, which increments from zero for
   * each packet (16 bits wide)
   * 
   * packet index is distinct for each packet (48 bits wide)
   *
   * nonce can be distinct across many uses of the same key, or
   * can be a fixed value per key, or can be per-packet randomness
   * (64 bits)
   *
   */
  
  err_status_t
  aes_icm_alloc_ismacryp(cipher_t **c, int key_len, int forIsmacryp) {
    extern cipher_type_t aes_icm;
    uint8_t *pointer;
    int tmp;
  
    debug_print(mod_aes_icm, 
              "allocating cipher with key length %d", key_len);
  
    /*
     * Ismacryp, for example, uses 16 byte key + 8 byte 
     * salt  so this function is called with key_len = 24.
     * The check for key_len = 30/38/46 does not apply. Our usage
     * of aes functions with key_len = values other than 30
     * has not broken anything. Don't know what would be the
     * effect of skipping this check for srtp in general.
     */
    if (!(forIsmacryp && key_len > 16 && key_len < 30) &&
        key_len != 30 && key_len != 38 && key_len != 46)
      return err_status_bad_param;
  
    /* allocate memory a cipher of type aes_icm */
    tmp = (sizeof(aes_icm_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;
    switch (key_len) {
    case 46:
        (*c)->algorithm = AES_256_ICM;
        break;
    case 38:
        (*c)->algorithm = AES_192_ICM;
        break;
    default:
        (*c)->algorithm = AES_128_ICM;
        break;
    }
    (*c)->type = &aes_icm;
    (*c)->state = pointer + sizeof(cipher_t);
  
    /* increment ref_count */
    aes_icm.ref_count++;
  
    /* set key size        */
    (*c)->key_len = key_len;
  
    return err_status_ok;  
  }
  
  err_status_t aes_icm_alloc(cipher_t **c, int key_len, int forIsmacryp) {
    return aes_icm_alloc_ismacryp(c, key_len, 0);
  }
  
  err_status_t
  aes_icm_dealloc(cipher_t *c) {
    extern cipher_type_t aes_icm;
  
    /* zeroize entire state*/
    octet_string_set_to_zero((uint8_t *)c, 
  			   sizeof(aes_icm_ctx_t) + sizeof(cipher_t));
  
    /* free memory */
    crypto_free(c);
  
    /* decrement ref_count */
    aes_icm.ref_count--;
    
    return err_status_ok;  
  }
  
  
  /*
   * aes_icm_context_init(...) initializes the aes_icm_context
   * using the value in key[].
   *
   * the key is the secret key 
   *
   * the salt is unpredictable (but not necessarily secret) data which
   * randomizes the starting point in the keystream
   */
  
  err_status_t
  aes_icm_context_init(aes_icm_ctx_t *c, const uint8_t *key, int key_len) {
    err_status_t status;
    int base_key_len, copy_len;
  
    if (key_len > 16 && key_len < 30) /* Ismacryp */
      base_key_len = 16;
    else if (key_len == 30 || key_len == 38 || key_len == 46)
      base_key_len = key_len - 14;
    else
      return err_status_bad_param;
  
    /*
     * set counter and initial values to 'offset' value, being careful not to
     * go past the end of the key buffer
     */
    v128_set_to_zero(&c->counter);
    v128_set_to_zero(&c->offset);
  
    copy_len = key_len - base_key_len;
    /* force last two octets of the offset to be left zero (for srtp compatibility) */
    if (copy_len > 14)
      copy_len = 14;
  
    memcpy(&c->counter, key + base_key_len, copy_len);
    memcpy(&c->offset, key + base_key_len, copy_len);
  
    debug_print(mod_aes_icm, 
  	      "key:  %s", octet_string_hex_string(key, base_key_len)); 
    debug_print(mod_aes_icm, 
  	      "offset: %s", v128_hex_string(&c->offset)); 
  
    /* expand key */
    status = aes_expand_encryption_key(key, base_key_len, &c->expanded_key);
    if (status) {
      v128_set_to_zero(&c->counter);
      v128_set_to_zero(&c->offset);
      return status;
    }
  
    /* indicate that the keystream_buffer is empty */
    c->bytes_in_buffer = 0;
  
    return err_status_ok;
  }
  
  /*
   * aes_icm_set_octet(c, i) sets the counter of the context which it is
   * passed so that the next octet of keystream that will be generated
   * is the ith octet
   */
  
  err_status_t
  aes_icm_set_octet(aes_icm_ctx_t *c,
  		  uint64_t octet_num) {
  
  #ifdef NO_64BIT_MATH
    int tail_num       = low32(octet_num) & 0x0f;
    /* 64-bit right-shift 4 */
    uint64_t block_num = make64(high32(octet_num) >> 4,
  							  ((high32(octet_num) & 0x0f)<<(32-4)) |
  							   (low32(octet_num) >> 4));
  #else
    int tail_num       = (int)(octet_num % 16);
    uint64_t block_num = octet_num / 16;
  #endif
    
  
    /* set counter value */
    /* FIX - There's no way this is correct */
    c->counter.v64[0] = c->offset.v64[0];
  #ifdef NO_64BIT_MATH
    c->counter.v64[0] = make64(high32(c->offset.v64[0]) ^ high32(block_num),
  							 low32(c->offset.v64[0])  ^ low32(block_num));
  #else
    c->counter.v64[0] = c->offset.v64[0] ^ block_num;
  #endif
  
    debug_print(mod_aes_icm, 
  	      "set_octet: %s", v128_hex_string(&c->counter)); 
  
    /* fill keystream buffer, if needed */
    if (tail_num) {
      v128_copy(&c->keystream_buffer, &c->counter);
      aes_encrypt(&c->keystream_buffer, &c->expanded_key);
      c->bytes_in_buffer = sizeof(v128_t);
  
      debug_print(mod_aes_icm, "counter:    %s", 
  	      v128_hex_string(&c->counter));
      debug_print(mod_aes_icm, "ciphertext: %s", 
  	      v128_hex_string(&c->keystream_buffer));    
      
      /*  indicate number of bytes in keystream_buffer  */
      c->bytes_in_buffer = sizeof(v128_t) - tail_num;
    
    } else {
      
      /* indicate that keystream_buffer is empty */
      c->bytes_in_buffer = 0;
    }
  
    return err_status_ok;
  }
  
  /*
   * aes_icm_set_iv(c, iv) sets the counter value to the exor of iv with
   * the offset
   */
  
  err_status_t
  aes_icm_set_iv(aes_icm_ctx_t *c, void *iv, int direction) {
    v128_t nonce;
  
    /* set nonce (for alignment) */
    v128_copy_octet_string(&nonce, iv);
  
    debug_print(mod_aes_icm, 
  	      "setting iv: %s", v128_hex_string(&nonce)); 
   
    v128_xor(&c->counter, &c->offset, &nonce);
    
    debug_print(mod_aes_icm, 
  	      "set_counter: %s", v128_hex_string(&c->counter)); 
  
    /* indicate that the keystream_buffer is empty */
    c->bytes_in_buffer = 0;
  
    return err_status_ok;
  }
  
  
  
  /*
   * aes_icm_advance(...) refills the keystream_buffer and
   * advances the block index of the sicm_context forward by one
   *
   * this is an internal, hopefully inlined function
   */
    
  static inline void
  aes_icm_advance_ismacryp(aes_icm_ctx_t *c, uint8_t forIsmacryp) {
    /* fill buffer with new keystream */
    v128_copy(&c->keystream_buffer, &c->counter);
    aes_encrypt(&c->keystream_buffer, &c->expanded_key);
    c->bytes_in_buffer = sizeof(v128_t);
  
    debug_print(mod_aes_icm, "counter:    %s", 
  	      v128_hex_string(&c->counter));
    debug_print(mod_aes_icm, "ciphertext: %s", 
  	      v128_hex_string(&c->keystream_buffer));    
    
    /* clock counter forward */
  
    if (forIsmacryp) {
      uint32_t temp;    
      //alex's clock counter forward
      temp = ntohl(c->counter.v32[3]);
      c->counter.v32[3] = htonl(++temp);
    } else {
      if (!++(c->counter.v8[15])) 
        ++(c->counter.v8[14]);
    }
  }
  
  static inline void aes_icm_advance(aes_icm_ctx_t *c) {
    aes_icm_advance_ismacryp(c, 0);
  }
  
  
  /*e
   * icm_encrypt deals with the following cases:
   *
   * bytes_to_encr < bytes_in_buffer
   *  - add keystream into data
   *
   * bytes_to_encr > bytes_in_buffer
   *  - add keystream into data until keystream_buffer is depleted
   *  - loop over blocks, filling keystream_buffer and then
   *    adding keystream into data
   *  - fill buffer then add in remaining (< 16) bytes of keystream 
   */
  
  err_status_t
  aes_icm_encrypt_ismacryp(aes_icm_ctx_t *c,
                unsigned char *buf, unsigned int *enc_len, 
                int forIsmacryp) {
    unsigned int bytes_to_encr = *enc_len;
    unsigned int i;
    uint32_t *b;
  
    /* check that there's enough segment left but not for ismacryp*/
    if (!forIsmacryp && (bytes_to_encr + htons(c->counter.v16[7])) > 0xffff)
      return err_status_terminus;
  
   debug_print(mod_aes_icm, "block index: %d", 
             htons(c->counter.v16[7]));
    if (bytes_to_encr <= (unsigned int)c->bytes_in_buffer) {
      
      /* deal with odd case of small bytes_to_encr */
      for (i = (sizeof(v128_t) - c->bytes_in_buffer);
  		 i < (sizeof(v128_t) - c->bytes_in_buffer + bytes_to_encr); i++) 
  	{
        *buf++ ^= c->keystream_buffer.v8[i];
  	}
  
      c->bytes_in_buffer -= bytes_to_encr;
  
      /* return now to avoid the main loop */
      return err_status_ok;
  
    } else {
      
      /* encrypt bytes until the remaining data is 16-byte aligned */    
      for (i=(sizeof(v128_t) - c->bytes_in_buffer); i < sizeof(v128_t); i++) 
        *buf++ ^= c->keystream_buffer.v8[i];
  
      bytes_to_encr -= c->bytes_in_buffer;
      c->bytes_in_buffer = 0;
  
    }
    
    /* now loop over entire 16-byte blocks of keystream */
    for (i=0; i < (bytes_to_encr/sizeof(v128_t)); i++) {
  
      /* fill buffer with new keystream */
      aes_icm_advance_ismacryp(c, forIsmacryp);
  
      /*
       * add keystream into the data buffer (this would be a lot faster
       * if we could assume 32-bit alignment!)
       */
  
  #if ALIGN_32
      b = (uint32_t *)buf;
      *b++ ^= c->keystream_buffer.v32[0];
      *b++ ^= c->keystream_buffer.v32[1];
      *b++ ^= c->keystream_buffer.v32[2];
      *b++ ^= c->keystream_buffer.v32[3];
      buf = (uint8_t *)b;
  #else    
      if ((((unsigned long) buf) & 0x03) != 0) {
        *buf++ ^= c->keystream_buffer.v8[0];
        *buf++ ^= c->keystream_buffer.v8[1];
        *buf++ ^= c->keystream_buffer.v8[2];
        *buf++ ^= c->keystream_buffer.v8[3];
        *buf++ ^= c->keystream_buffer.v8[4];
        *buf++ ^= c->keystream_buffer.v8[5];
        *buf++ ^= c->keystream_buffer.v8[6];
        *buf++ ^= c->keystream_buffer.v8[7];
        *buf++ ^= c->keystream_buffer.v8[8];
        *buf++ ^= c->keystream_buffer.v8[9];
        *buf++ ^= c->keystream_buffer.v8[10];
        *buf++ ^= c->keystream_buffer.v8[11];
        *buf++ ^= c->keystream_buffer.v8[12];
        *buf++ ^= c->keystream_buffer.v8[13];
        *buf++ ^= c->keystream_buffer.v8[14];
        *buf++ ^= c->keystream_buffer.v8[15];
      } else {
        b = (uint32_t *)buf;
        *b++ ^= c->keystream_buffer.v32[0];
        *b++ ^= c->keystream_buffer.v32[1];
        *b++ ^= c->keystream_buffer.v32[2];
        *b++ ^= c->keystream_buffer.v32[3];
        buf = (uint8_t *)b;
      }
  #endif /* #if ALIGN_32 */
  
    }
    
    /* if there is a tail end of the data, process it */
    if ((bytes_to_encr & 0xf) != 0) {
      
      /* fill buffer with new keystream */
      aes_icm_advance_ismacryp(c, forIsmacryp);
      
      for (i=0; i < (bytes_to_encr & 0xf); i++)
        *buf++ ^= c->keystream_buffer.v8[i];
      
      /* reset the keystream buffer size to right value */
      c->bytes_in_buffer = sizeof(v128_t) - i;  
    } else {
  
      /* no tail, so just reset the keystream buffer size to zero */
      c->bytes_in_buffer = 0;
  
    }
  
    return err_status_ok;
  }
  
  err_status_t
  aes_icm_encrypt(aes_icm_ctx_t *c, unsigned char *buf, unsigned int *enc_len) {
    return aes_icm_encrypt_ismacryp(c, buf, enc_len, 0);
  }
  
  err_status_t
  aes_icm_output(aes_icm_ctx_t *c, uint8_t *buffer, int num_octets_to_output) {
    unsigned int len = num_octets_to_output;
    
    /* zeroize the buffer */
    octet_string_set_to_zero(buffer, num_octets_to_output);
    
    /* exor keystream into buffer */
    return aes_icm_encrypt(c, buffer, &len);
  }
  
  uint16_t
  aes_icm_bytes_encrypted(aes_icm_ctx_t *c) {
      return htons(c->counter.v16[7]);
  }
  
  char 
  aes_icm_description[] = "aes integer counter mode";
  
  uint8_t aes_icm_test_case_0_key[30] = {
    0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6,
    0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c,
    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
    0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd
  };
  
  uint8_t aes_icm_test_case_0_nonce[16] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
  };
  
  uint8_t aes_icm_test_case_0_plaintext[32] =  {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
  };
  
  uint8_t aes_icm_test_case_0_ciphertext[32] = {
    0xe0, 0x3e, 0xad, 0x09, 0x35, 0xc9, 0x5e, 0x80,
    0xe1, 0x66, 0xb1, 0x6d, 0xd9, 0x2b, 0x4e, 0xb4,
    0xd2, 0x35, 0x13, 0x16, 0x2b, 0x02, 0xd0, 0xf7,
    0x2a, 0x43, 0xa2, 0xfe, 0x4a, 0x5f, 0x97, 0xab
  };
  
  cipher_test_case_t aes_icm_test_case_0 = {
    30,                                    /* octets in key            */
    aes_icm_test_case_0_key,               /* key                      */
    aes_icm_test_case_0_nonce,             /* packet index             */
    32,                                    /* octets in plaintext      */
    aes_icm_test_case_0_plaintext,         /* plaintext                */
    32,                                    /* octets in ciphertext     */
    aes_icm_test_case_0_ciphertext,        /* ciphertext               */
    0,
    NULL,
    0,
    NULL                                   /* pointer to next testcase */
  };
  
  uint8_t aes_icm_test_case_1_key[46] = {
    0x57, 0xf8, 0x2f, 0xe3, 0x61, 0x3f, 0xd1, 0x70,
    0xa8, 0x5e, 0xc9, 0x3c, 0x40, 0xb1, 0xf0, 0x92,
    0x2e, 0xc4, 0xcb, 0x0d, 0xc0, 0x25, 0xb5, 0x82,
    0x72, 0x14, 0x7c, 0xc4, 0x38, 0x94, 0x4a, 0x98,
    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
    0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd
  };
  
  uint8_t aes_icm_test_case_1_nonce[16] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
  };
  
  uint8_t aes_icm_test_case_1_plaintext[32] =  {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
  };
  
  uint8_t aes_icm_test_case_1_ciphertext[32] = {
    0x92, 0xbd, 0xd2, 0x8a, 0x93, 0xc3, 0xf5, 0x25,
    0x11, 0xc6, 0x77, 0xd0, 0x8b, 0x55, 0x15, 0xa4,
    0x9d, 0xa7, 0x1b, 0x23, 0x78, 0xa8, 0x54, 0xf6,
    0x70, 0x50, 0x75, 0x6d, 0xed, 0x16, 0x5b, 0xac
  };
  
  cipher_test_case_t aes_icm_test_case_1 = {
    46,                                    /* octets in key            */
    aes_icm_test_case_1_key,               /* key                      */
    aes_icm_test_case_1_nonce,             /* packet index             */
    32,                                    /* octets in plaintext      */
    aes_icm_test_case_1_plaintext,         /* plaintext                */
    32,                                    /* octets in ciphertext     */
    aes_icm_test_case_1_ciphertext,        /* ciphertext               */
    0,
    NULL,
    0,
    &aes_icm_test_case_0                   /* pointer to next testcase */
  };
  
  
  
  /*
   * note: the encrypt function is identical to the decrypt function
   */
  
  cipher_type_t aes_icm = {
    (cipher_alloc_func_t)          aes_icm_alloc,
    (cipher_dealloc_func_t)        aes_icm_dealloc,  
    (cipher_init_func_t)           aes_icm_context_init,
    (cipher_set_aad_func_t)        0,
    (cipher_encrypt_func_t)        aes_icm_encrypt,
    (cipher_decrypt_func_t)        aes_icm_encrypt,
    (cipher_set_iv_func_t)         aes_icm_set_iv,
    (cipher_get_tag_func_t)        0,
    (char *)                       aes_icm_description,
    (int)                          0,   /* instance count */
    (cipher_test_case_t *)        &aes_icm_test_case_1,
    (debug_module_t *)            &mod_aes_icm,
    (cipher_type_id_t)             AES_ICM
  };
  
  