1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
/*
* Copyright (c) 2011 The Chromium OS Authors.
* (C) Copyright 2010 - 2011 NVIDIA Corporation <www.nvidia.com>
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <common.h>
#include <linux/errno.h>
#include "crypto.h"
#include "aes.h"
static u8 zero_key[16];
#define AES_CMAC_CONST_RB 0x87 /* from RFC 4493, Figure 2.2 */
enum security_op {
SECURITY_SIGN = 1 << 0, /* Sign the data */
SECURITY_ENCRYPT = 1 << 1, /* Encrypt the data */
};
/**
* Shift a vector left by one bit
*
* \param in Input vector
* \param out Output vector
* \param size Length of vector in bytes
*/
static void left_shift_vector(u8 *in, u8 *out, int size)
{
int carry = 0;
int i;
for (i = size - 1; i >= 0; i--) {
out[i] = (in[i] << 1) | carry;
carry = in[i] >> 7; /* get most significant bit */
}
}
/**
* Sign a block of data, putting the result into dst.
*
* \param key Input AES key, length AES_KEY_LENGTH
* \param key_schedule Expanded key to use
* \param src Source data of length 'num_aes_blocks' blocks
* \param dst Destination buffer, length AES_KEY_LENGTH
* \param num_aes_blocks Number of AES blocks to encrypt
*/
static void sign_object(u8 *key, u8 *key_schedule, u8 *src, u8 *dst,
u32 num_aes_blocks)
{
u8 tmp_data[AES_KEY_LENGTH];
u8 left[AES_KEY_LENGTH];
u8 k1[AES_KEY_LENGTH];
u8 *cbc_chain_data;
unsigned i;
cbc_chain_data = zero_key; /* Convenient array of 0's for IV */
/* compute K1 constant needed by AES-CMAC calculation */
for (i = 0; i < AES_KEY_LENGTH; i++)
tmp_data[i] = 0;
aes_cbc_encrypt_blocks(key_schedule, tmp_data, left, 1);
left_shift_vector(left, k1, sizeof(left));
if ((left[0] >> 7) != 0) /* get MSB of L */
k1[AES_KEY_LENGTH-1] ^= AES_CMAC_CONST_RB;
/* compute the AES-CMAC value */
for (i = 0; i < num_aes_blocks; i++) {
/* Apply the chain data */
aes_apply_cbc_chain_data(cbc_chain_data, src, tmp_data);
/* for the final block, XOR K1 into the IV */
if (i == num_aes_blocks - 1)
aes_apply_cbc_chain_data(tmp_data, k1, tmp_data);
/* encrypt the AES block */
aes_encrypt(tmp_data, key_schedule, dst);
debug("sign_obj: block %d of %d\n", i, num_aes_blocks);
/* Update pointers for next loop. */
cbc_chain_data = dst;
src += AES_KEY_LENGTH;
}
}
/**
* Encrypt and sign a block of data (depending on security mode).
*
* \param key Input AES key, length AES_KEY_LENGTH
* \param oper Security operations mask to perform (enum security_op)
* \param src Source data
* \param length Size of source data
* \param sig_dst Destination address for signature, AES_KEY_LENGTH bytes
*/
static int encrypt_and_sign(u8 *key, enum security_op oper, u8 *src,
u32 length, u8 *sig_dst)
{
u32 num_aes_blocks;
u8 key_schedule[AES_EXPAND_KEY_LENGTH];
debug("encrypt_and_sign: length = %d\n", length);
/*
* The only need for a key is for signing/checksum purposes, so
* if not encrypting, expand a key of 0s.
*/
aes_expand_key(oper & SECURITY_ENCRYPT ? key : zero_key, key_schedule);
num_aes_blocks = (length + AES_KEY_LENGTH - 1) / AES_KEY_LENGTH;
if (oper & SECURITY_ENCRYPT) {
/* Perform this in place, resulting in src being encrypted. */
debug("encrypt_and_sign: begin encryption\n");
aes_cbc_encrypt_blocks(key_schedule, src, src, num_aes_blocks);
debug("encrypt_and_sign: end encryption\n");
}
if (oper & SECURITY_SIGN) {
/* encrypt the data, overwriting the result in signature. */
debug("encrypt_and_sign: begin signing\n");
sign_object(key, key_schedule, src, sig_dst, num_aes_blocks);
debug("encrypt_and_sign: end signing\n");
}
return 0;
}
int sign_data_block(u8 *source, unsigned length, u8 *signature)
{
return encrypt_and_sign(zero_key, SECURITY_SIGN, source,
length, signature);
}
|
