src/crypto/axtls_aes.c

   1 /*
   2  * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <string.h>
  20 #include <errno.h>
  21 #include <byteswap.h>
  22 #include <gpxe/crypto.h>
  23 #include <gpxe/cbc.h>
  24 #include <gpxe/aes.h>
  25 #include "crypto/axtls/crypto.h"
  26
  27 /** @file
  28  *
  29  * AES algorithm
  30  *
  31  */
  32
  33 /** Basic AES blocksize */
  34 #define AES_BLOCKSIZE 16
  35
  36 /** AES context */
  37 struct aes_context {
  38         /** AES context for AXTLS */
  39         AES_CTX axtls_ctx;
  40         /** Cipher is being used for decrypting */
  41         int decrypting;
  42 };
  43
  44 /**
  45  * Set key
  46  *
  47  * @v ctx               Context
  48  * @v key               Key
  49  * @v keylen            Key length
  50  * @ret rc              Return status code
  51  */
  52 static int aes_setkey ( void *ctx, const void *key, size_t keylen ) {
  53         struct aes_context *aes_ctx = ctx;
  54         AES_MODE mode;
  55         void *iv;
  56
  57         switch ( keylen ) {
  58         case ( 128 / 8 ):
  59                 mode = AES_MODE_128;
  60                 break;
  61         case ( 256 / 8 ):
  62                 mode = AES_MODE_256;
  63                 break;
  64         default:
  65                 return -EINVAL;
  66         }
  67
  68         /* IV is not a relevant concept at this stage; use a dummy
  69          * value that will have no side-effects.
  70          */
  71         iv = &aes_ctx->axtls_ctx.iv;
  72
  73         AES_set_key ( &aes_ctx->axtls_ctx, key, iv, mode );
  74
  75         aes_ctx->decrypting = 0;
  76
  77         return 0;
  78 }
  79
  80 /**
  81  * Set initialisation vector
  82  *
  83  * @v ctx               Context
  84  * @v iv                Initialisation vector
  85  */
  86 static void aes_setiv ( void *ctx __unused, const void *iv __unused ) {
  87         /* Nothing to do */
  88 }
  89
  90 /**
  91  * Call AXTLS' AES_encrypt() or AES_decrypt() functions
  92  *
  93  * @v axtls_ctx         AXTLS AES context
  94  * @v src               Data to process
  95  * @v dst               Buffer for output
  96  * @v func              AXTLS AES function to call
  97  */
  98 static void aes_call_axtls ( AES_CTX *axtls_ctx, const void *src, void *dst,
  99                              void ( * func ) ( const AES_CTX *axtls_ctx,
 100                                                uint32_t *data ) ){
 101         const uint32_t *srcl = src;
 102         uint32_t *dstl = dst;
 103         unsigned int i;
 104
 105         /* AXTLS' AES_encrypt() and AES_decrypt() functions both
 106          * expect to deal with an array of four dwords in host-endian
 107          * order.
 108          */
 109         for ( i = 0 ; i < 4 ; i++ )
 110                 dstl[i] = ntohl ( srcl[i] );
 111         func ( axtls_ctx, dstl );
 112         for ( i = 0 ; i < 4 ; i++ )
 113                 dstl[i] = htonl ( dstl[i] );
 114 }
 115
 116 /**
 117  * Encrypt data
 118  *
 119  * @v ctx               Context
 120  * @v src               Data to encrypt
 121  * @v dst               Buffer for encrypted data
 122  * @v len               Length of data
 123  */
 124 static void aes_encrypt ( void *ctx, const void *src, void *dst,
 125                           size_t len ) {
 126         struct aes_context *aes_ctx = ctx;
 127
 128         assert ( len == AES_BLOCKSIZE );
 129         if ( aes_ctx->decrypting )
 130                 assert ( 0 );
 131         aes_call_axtls ( &aes_ctx->axtls_ctx, src, dst, AES_encrypt );
 132 }
 133
 134 /**
 135  * Decrypt data
 136  *
 137  * @v ctx               Context
 138  * @v src               Data to decrypt
 139  * @v dst               Buffer for decrypted data
 140  * @v len               Length of data
 141  */
 142 static void aes_decrypt ( void *ctx, const void *src, void *dst,
 143                           size_t len ) {
 144         struct aes_context *aes_ctx = ctx;
 145
 146         assert ( len == AES_BLOCKSIZE );
 147         if ( ! aes_ctx->decrypting ) {
 148                 AES_convert_key ( &aes_ctx->axtls_ctx );
 149                 aes_ctx->decrypting = 1;
 150         }
 151         aes_call_axtls ( &aes_ctx->axtls_ctx, src, dst, AES_decrypt );
 152 }
 153
 154 /** Basic AES algorithm */
 155 static struct cipher_algorithm aes_algorithm = {
 156         .name = "aes",
 157         .ctxsize = sizeof ( struct aes_context ),
 158         .blocksize = AES_BLOCKSIZE,
 159         .setkey = aes_setkey,
 160         .setiv = aes_setiv,
 161         .encrypt = aes_encrypt,
 162         .decrypt = aes_decrypt,
 163 };
 164
 165 /* AES with cipher-block chaining */
 166 CBC_CIPHER ( aes_cbc, aes_cbc_algorithm,
 167              aes_algorithm, struct aes_context, AES_BLOCKSIZE );