src/crypto/aes_wrap.c

   1 /*
   2  * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
   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., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  */
  19
  20 FILE_LICENCE ( GPL2_OR_LATER );
  21
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <ipxe/crypto.h>
  25 #include <ipxe/aes.h>
  26
  27 /**
  28  * Wrap a key or other data using AES Key Wrap (RFC 3394)
  29  *
  30  * @v kek       Key Encryption Key, 16 bytes
  31  * @v src       Data to encrypt
  32  * @v nblk      Number of 8-byte blocks in @a data
  33  * @ret dest    Encrypted data (8 bytes longer than input)
  34  *
  35  * The algorithm is implemented such that @a src and @a dest may point
  36  * to the same buffer.
  37  */
  38 int aes_wrap ( const void *kek, const void *src, void *dest, int nblk )
  39 {
  40         u8 *A = dest;
  41         u8 B[16];
  42         u8 *R;
  43         int i, j;
  44         void *aes_ctx = malloc ( AES_CTX_SIZE );
  45
  46         if ( ! aes_ctx )
  47                 return -1;
  48
  49         cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );
  50
  51         /* Set up */
  52         memset ( A, 0xA6, 8 );
  53         memmove ( dest + 8, src, nblk * 8 );
  54
  55         /* Wrap */
  56         for ( j = 0; j < 6; j++ ) {
  57                 R = dest + 8;
  58                 for ( i = 1; i <= nblk; i++ ) {
  59                         memcpy ( B, A, 8 );
  60                         memcpy ( B + 8, R, 8 );
  61                         cipher_encrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
  62                         memcpy ( A, B, 8 );
  63                         A[7] ^= ( nblk * j ) + i;
  64                         memcpy ( R, B + 8, 8 );
  65                         R += 8;
  66                 }
  67         }
  68
  69         free ( aes_ctx );
  70         return 0;
  71 }
  72
  73 /**
  74  * Unwrap a key or other data using AES Key Wrap (RFC 3394)
  75  *
  76  * @v kek       Key Encryption Key, 16 bytes
  77  * @v src       Data to decrypt
  78  * @v nblk      Number of 8-byte blocks in @e plaintext key
  79  * @ret dest    Decrypted data (8 bytes shorter than input)
  80  * @ret rc      Zero on success, nonzero on IV mismatch
  81  *
  82  * The algorithm is implemented such that @a src and @a dest may point
  83  * to the same buffer.
  84  */
  85 int aes_unwrap ( const void *kek, const void *src, void *dest, int nblk )
  86 {
  87         u8 A[8], B[16];
  88         u8 *R;
  89         int i, j;
  90         void *aes_ctx = malloc ( AES_CTX_SIZE );
  91
  92         if ( ! aes_ctx )
  93                 return -1;
  94
  95         cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );
  96
  97         /* Set up */
  98         memcpy ( A, src, 8 );
  99         memmove ( dest, src + 8, nblk * 8 );
 100
 101         /* Unwrap */
 102         for ( j = 5; j >= 0; j-- ) {
 103                 R = dest + ( nblk - 1 ) * 8;
 104                 for ( i = nblk; i >= 1; i-- ) {
 105                         memcpy ( B, A, 8 );
 106                         memcpy ( B + 8, R, 8 );
 107                         B[7] ^= ( nblk * j ) + i;
 108                         cipher_decrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
 109                         memcpy ( A, B, 8 );
 110                         memcpy ( R, B + 8, 8 );
 111                         R -= 8;
 112                 }
 113         }
 114
 115         free ( aes_ctx );
 116
 117         /* Check IV */
 118         for ( i = 0; i < 8; i++ ) {
 119                 if ( A[i] != 0xA6 )
 120                         return -1;
 121         }
 122
 123         return 0;
 124 }