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., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19 FILE_LICENCE ( GPL2_OR_LATER );
20
21 #include <stdlib.h>
22 #include <string.h>
23 #include <gpxe/crypto.h>
24 #include <gpxe/aes.h>
25
26 /**
27 * Wrap a key or other data using AES Key Wrap (RFC 3394)
28 *
29 * @v kek Key Encryption Key, 16 bytes
30 * @v src Data to encrypt
31 * @v nblk Number of 8-byte blocks in @a data
32 * @ret dest Encrypted data (8 bytes longer than input)
33 *
34 * The algorithm is implemented such that @a src and @a dest may point
35 * to the same buffer.
36 */
aes_wrap(const void * kek,const void * src,void * dest,int nblk)37 int aes_wrap ( const void *kek, const void *src, void *dest, int nblk )
38 {
39 u8 *A = dest;
40 u8 B[16];
41 u8 *R;
42 int i, j;
43 void *aes_ctx = malloc ( AES_CTX_SIZE );
44
45 if ( ! aes_ctx )
46 return -1;
47
48 cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );
49
50 /* Set up */
51 memset ( A, 0xA6, sizeof ( A ) );
52 memmove ( dest + 8, src, nblk * 8 );
53
54 /* Wrap */
55 for ( j = 0; j < 6; j++ ) {
56 R = dest + 8;
57 for ( i = 1; i <= nblk; i++ ) {
58 memcpy ( B, A, 8 );
59 memcpy ( B + 8, R, 8 );
60 cipher_encrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
61 memcpy ( A, B, 8 );
62 A[7] ^= ( nblk * j ) + i;
63 memcpy ( R, B + 8, 8 );
64 R += 8;
65 }
66 }
67
68 free ( aes_ctx );
69 return 0;
70 }
71
72 /**
73 * Unwrap a key or other data using AES Key Wrap (RFC 3394)
74 *
75 * @v kek Key Encryption Key, 16 bytes
76 * @v src Data to decrypt
77 * @v nblk Number of 8-byte blocks in @e plaintext key
78 * @ret dest Decrypted data (8 bytes shorter than input)
79 * @ret rc Zero on success, nonzero on IV mismatch
80 *
81 * The algorithm is implemented such that @a src and @a dest may point
82 * to the same buffer.
83 */
aes_unwrap(const void * kek,const void * src,void * dest,int nblk)84 int aes_unwrap ( const void *kek, const void *src, void *dest, int nblk )
85 {
86 u8 A[8], B[16];
87 u8 *R;
88 int i, j;
89 void *aes_ctx = malloc ( AES_CTX_SIZE );
90
91 if ( ! aes_ctx )
92 return -1;
93
94 cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );
95
96 /* Set up */
97 memcpy ( A, src, 8 );
98 memmove ( dest, src + 8, nblk * 8 );
99
100 /* Unwrap */
101 for ( j = 5; j >= 0; j-- ) {
102 R = dest + ( nblk - 1 ) * 8;
103 for ( i = nblk; i >= 1; i-- ) {
104 memcpy ( B, A, 8 );
105 memcpy ( B + 8, R, 8 );
106 B[7] ^= ( nblk * j ) + i;
107 cipher_decrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
108 memcpy ( A, B, 8 );
109 memcpy ( R, B + 8, 8 );
110 R -= 8;
111 }
112 }
113
114 free ( aes_ctx );
115
116 /* Check IV */
117 for ( i = 0; i < 8; i++ ) {
118 if ( A[i] != 0xA6 )
119 return -1;
120 }
121
122 return 0;
123 }
124