src/libstrongswan/plugins/cmac/cmac_signer.c

   1 /*
   2  * Copyright (C) 2012 Tobias Brunner
   3  * Hochschule fuer Technik Rapperswil
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the
   7  * Free Software Foundation; either version 2 of the License, or (at your
   8  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  12  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * for more details.
  14  */
  15
  16 #include <string.h>
  17
  18 #include "cmac_signer.h"
  19 #include "cmac.h"
  20
  21 typedef struct private_cmac_signer_t private_cmac_signer_t;
  22
  23 /**
  24  * Private data structure with signing context.
  25  */
  26 struct private_cmac_signer_t {
  27
  28         /**
  29          * Public interface.
  30          */
  31         cmac_signer_t public;
  32
  33         /**
  34          * Assigned cmac function.
  35          */
  36         cmac_t *cmac;
  37
  38         /**
  39          * Block size (truncation of CMAC MAC)
  40          */
  41         size_t block_size;
  42 };
  43
  44 METHOD(signer_t, get_signature, void,
  45         private_cmac_signer_t *this, chunk_t data, u_int8_t *buffer)
  46 {
  47         if (buffer == NULL)
  48         {       /* append mode */
  49                 this->cmac->get_mac(this->cmac, data, NULL);
  50         }
  51         else
  52         {
  53                 u_int8_t mac[this->cmac->get_block_size(this->cmac)];
  54
  55                 this->cmac->get_mac(this->cmac, data, mac);
  56                 memcpy(buffer, mac, this->block_size);
  57         }
  58 }
  59
  60 METHOD(signer_t, allocate_signature, void,
  61         private_cmac_signer_t *this, chunk_t data, chunk_t *chunk)
  62 {
  63         if (chunk == NULL)
  64         {       /* append mode */
  65                 this->cmac->get_mac(this->cmac, data, NULL);
  66         }
  67         else
  68         {
  69                 u_int8_t mac[this->cmac->get_block_size(this->cmac)];
  70
  71                 this->cmac->get_mac(this->cmac, data, mac);
  72
  73                 chunk->ptr = malloc(this->block_size);
  74                 chunk->len = this->block_size;
  75
  76                 memcpy(chunk->ptr, mac, this->block_size);
  77         }
  78 }
  79
  80 METHOD(signer_t, verify_signature, bool,
  81         private_cmac_signer_t *this, chunk_t data, chunk_t signature)
  82 {
  83         u_int8_t mac[this->cmac->get_block_size(this->cmac)];
  84
  85         if (signature.len != this->block_size)
  86         {
  87                 return FALSE;
  88         }
  89
  90         this->cmac->get_mac(this->cmac, data, mac);
  91         return memeq(signature.ptr, mac, this->block_size);
  92 }
  93
  94 METHOD(signer_t, get_key_size, size_t,
  95         private_cmac_signer_t *this)
  96 {
  97         return this->cmac->get_block_size(this->cmac);
  98 }
  99
 100 METHOD(signer_t, get_block_size, size_t,
 101         private_cmac_signer_t *this)
 102 {
 103         return this->block_size;
 104 }
 105
 106 METHOD(signer_t, set_key, void,
 107         private_cmac_signer_t *this, chunk_t key)
 108 {
 109         this->cmac->set_key(this->cmac, key);
 110 }
 111
 112 METHOD(signer_t, destroy, void,
 113         private_cmac_signer_t *this)
 114 {
 115         this->cmac->destroy(this->cmac);
 116         free(this);
 117 }
 118
 119 /*
 120  * Described in header
 121  */
 122 cmac_signer_t *cmac_signer_create(integrity_algorithm_t algo)
 123 {
 124         private_cmac_signer_t *this;
 125         size_t truncation;
 126         cmac_t *cmac;
 127
 128         switch (algo)
 129         {
 130                 case AUTH_AES_CMAC_96:
 131                         cmac = cmac_create(ENCR_AES_CBC, 16);
 132                         truncation = 12;
 133                         break;
 134                 default:
 135                         return NULL;
 136         }
 137         if (cmac == NULL)
 138         {
 139                 return NULL;
 140         }
 141
 142         INIT(this,
 143                 .public = {
 144                         .signer = {
 145                                 .get_signature = _get_signature,
 146                                 .allocate_signature = _allocate_signature,
 147                                 .verify_signature = _verify_signature,
 148                                 .get_key_size = _get_key_size,
 149                                 .get_block_size = _get_block_size,
 150                                 .set_key = _set_key,
 151                                 .destroy = _destroy,
 152                         },
 153                 },
 154                 .cmac = cmac,
 155                 .block_size = min(truncation, cmac->get_block_size(cmac)),
 156         );
 157
 158         return &this->public;
 159 }