Source/charon/transforms/hmac.c

   1 /**
   2  * @file hmac.c
   3  *
   4  * @brief Implementation of message authentication
   5  * using cryptographic hash functions (HMAC). See RFC2104.
   6  *
   7  */
   8
   9 /*
  10  * Copyright (C) 2005 Jan Hutter, Martin Willi
  11  * Hochschule fuer Technik Rapperswil
  12  *
  13  * This program is free software; you can redistribute it and/or modify it
  14  * under the terms of the GNU General Public License as published by the
  15  * Free Software Foundation; either version 2 of the License, or (at your
  16  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
  17  *
  18  * This program is distributed in the hope that it will be useful, but
  19  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  20  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  21  * for more details.
  22  */
  23
  24
  25 #include "hmac.h"
  26
  27 #include "../utils/allocator.h"
  28
  29 /**
  30  * Private data of an hmac_t object.
  31  *
  32  */
  33 typedef struct private_hmac_s private_hmac_t;
  34
  35 struct private_hmac_s {
  36         /**
  37          * public hmac_t interface
  38          */
  39         hmac_t public;
  40
  41         /**
  42          * key, as in RFC
  43          */
  44         chunk_t k;
  45
  46         /**
  47          * block size, as in RFC
  48          */
  49         u_int8_t b;
  50
  51         /**
  52          * hash function
  53          */
  54         hasher_t *h;
  55
  56         /**
  57          * previously xor'ed key using opad
  58          */
  59         chunk_t opaded_key;
  60         /**
  61          * previously xor'ed key using ipad
  62          */
  63         chunk_t ipaded_key;
  64 };
  65
  66 /**
  67  * implementation of hmac_t.get_mac
  68  */
  69 static status_t get_mac(private_hmac_t *this, chunk_t data, u_int8_t *out)
  70 {
  71         /* H(K XOR opad, H(K XOR ipad, text)) */
  72         u_int8_t buffer[this->h->get_block_size(this->h)];
  73         chunk_t inner;
  74         inner.ptr = buffer;
  75         inner.len = this->h->get_block_size(this->h);
  76
  77         /* inner */
  78         this->h->get_hash(this->h, this->ipaded_key, NULL);
  79         this->h->get_hash(this->h, data, buffer);
  80
  81         /* outer */
  82         this->h->get_hash(this->h, this->opaded_key, NULL);
  83         this->h->get_hash(this->h, inner, out);
  84
  85         return SUCCESS;
  86 }
  87
  88 /**
  89  * implementation of hmac_t.allocate_mac
  90  */
  91 static status_t allocate_mac(private_hmac_t *this, chunk_t data, chunk_t *out)
  92 {
  93         /* allocate space and use get_mac */
  94         out->len = this->h->get_block_size(this->h);
  95         out->ptr = allocator_alloc(out->len);
  96         if (out->ptr == NULL)
  97         {
  98                 return OUT_OF_RES;
  99         }
 100         this->public.get_mac(&(this->public), data, out->ptr);
 101         return SUCCESS;
 102 }
 103
 104 /**
 105  * implementation of hmac_t.get_block_size
 106  */
 107 static size_t get_block_size(private_hmac_t *this)
 108 {
 109         return this->h->get_block_size(this->h);
 110 }
 111
 112 /**
 113  * implementation of hmac_t.set_key
 114  */
 115 static status_t set_key(private_hmac_t *this, chunk_t key)
 116 {
 117         int i;
 118         u_int8_t buffer[this->b];
 119
 120         memset(buffer, 0, this->b);
 121
 122         if (key.len > this->b)
 123         {
 124                 /* if key is too long, it will be hashed */
 125                 this->h->get_hash(this->h, key, buffer);
 126         }
 127         else
 128         {
 129                 /* if not, just copy it in our pre-padded k */
 130                 memcpy(buffer, key.ptr, key.len);
 131         }
 132
 133         /* apply ipad and opad to key */
 134         for (i = 0; i < this->b; i++)
 135         {
 136                 this->ipaded_key.ptr[i] = buffer[i] ^ 0x36;
 137                 this->opaded_key.ptr[i] = buffer[i] ^ 0x5C;
 138         }
 139
 140         return SUCCESS;;
 141 }
 142
 143 /**
 144  * implementation of hmac_t.destroy
 145  */
 146 static status_t destroy(private_hmac_t *this)
 147 {
 148         this->h->destroy(this->h);
 149         allocator_free(this->k.ptr);
 150         allocator_free(this->opaded_key.ptr);
 151         allocator_free(this->ipaded_key.ptr);
 152         allocator_free(this);
 153         return SUCCESS;
 154 }
 155
 156 /*
 157  * Described in header
 158  */
 159 hmac_t *hmac_create(hash_algorithm_t hash_algorithm)
 160 {
 161         private_hmac_t *this;
 162
 163         this = allocator_alloc_thing(private_hmac_t);
 164         if (this == NULL)
 165         {
 166                 return NULL;
 167         }
 168         /* set public methods */
 169         this->public.get_mac = (size_t (*)(hmac_t *,chunk_t,u_int8_t*))get_mac;
 170         this->public.allocate_mac = (size_t (*)(hmac_t *,chunk_t,chunk_t*))allocate_mac;
 171         this->public.get_block_size = (size_t (*)(hmac_t *))get_block_size;
 172         this->public.set_key = (status_t (*)(hmac_t *,chunk_t))set_key;
 173         this->public.destroy = (status_t (*)(hmac_t *))destroy;
 174
 175         /* set b, according to hasher */
 176         switch (hash_algorithm)
 177         {
 178                 case HASH_SHA1:
 179                         this->b = 64;
 180                         break;
 181                 default:
 182                         allocator_free(this);
 183                         return NULL;
 184         }
 185
 186         /* build the hasher */
 187         this->h = hasher_create(hash_algorithm);
 188         if (this->h == NULL)
 189         {
 190                 allocator_free(this);
 191                 return NULL;
 192         }
 193
 194
 195
 196         /* build ipad and opad */
 197         this->opaded_key.ptr = allocator_alloc(this->b);
 198         this->opaded_key.len = this->b;
 199         if (this->opaded_key.ptr == NULL)
 200         {
 201                 this->h->destroy(this->h);
 202                 allocator_free(this->k.ptr);
 203                 allocator_free(this);
 204                 return NULL;
 205         }
 206         this->ipaded_key.ptr = allocator_alloc(this->b);
 207         this->ipaded_key.len = this->b;
 208         if (this->ipaded_key.ptr == NULL)
 209         {
 210                 this->h->destroy(this->h);
 211                 allocator_free(this->opaded_key.ptr);
 212                 allocator_free(this);
 213                 return NULL;
 214         }
 215
 216
 217         return &(this->public);
 218 }