1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (c) 2011 The Chromium OS Authors.
4 * (C) Copyright 2010 - 2011 NVIDIA Corporation <www.nvidia.com>
5 */
6
7 #include <common.h>
8 #include <log.h>
9 #include <linux/errno.h>
10 #include "crypto.h"
11 #include "uboot_aes.h"
12
13 static u8 zero_key[16];
14
15 #define AES_CMAC_CONST_RB 0x87 /* from RFC 4493, Figure 2.2 */
16
17 enum security_op {
18 SECURITY_SIGN = 1 << 0, /* Sign the data */
19 SECURITY_ENCRYPT = 1 << 1, /* Encrypt the data */
20 };
21
22 /**
23 * Shift a vector left by one bit
24 *
25 * \param in Input vector
26 * \param out Output vector
27 * \param size Length of vector in bytes
28 */
left_shift_vector(u8 * in,u8 * out,int size)29 static void left_shift_vector(u8 *in, u8 *out, int size)
30 {
31 int carry = 0;
32 int i;
33
34 for (i = size - 1; i >= 0; i--) {
35 out[i] = (in[i] << 1) | carry;
36 carry = in[i] >> 7; /* get most significant bit */
37 }
38 }
39
40 /**
41 * Sign a block of data, putting the result into dst.
42 *
43 * \param key Input AES key, length AES128_KEY_LENGTH
44 * \param key_schedule Expanded key to use
45 * \param src Source data of length 'num_aes_blocks' blocks
46 * \param dst Destination buffer, length AES128_KEY_LENGTH
47 * \param num_aes_blocks Number of AES blocks to encrypt
48 */
sign_object(u8 * key,u8 * key_schedule,u8 * src,u8 * dst,u32 num_aes_blocks)49 static void sign_object(u8 *key, u8 *key_schedule, u8 *src, u8 *dst,
50 u32 num_aes_blocks)
51 {
52 u8 tmp_data[AES128_KEY_LENGTH];
53 u8 iv[AES128_KEY_LENGTH] = {0};
54 u8 left[AES128_KEY_LENGTH];
55 u8 k1[AES128_KEY_LENGTH];
56 u8 *cbc_chain_data;
57 unsigned i;
58
59 cbc_chain_data = zero_key; /* Convenient array of 0's for IV */
60
61 /* compute K1 constant needed by AES-CMAC calculation */
62 for (i = 0; i < AES128_KEY_LENGTH; i++)
63 tmp_data[i] = 0;
64
65 aes_cbc_encrypt_blocks(AES128_KEY_LENGTH, key_schedule, iv,
66 tmp_data, left, 1);
67
68 left_shift_vector(left, k1, sizeof(left));
69
70 if ((left[0] >> 7) != 0) /* get MSB of L */
71 k1[AES128_KEY_LENGTH - 1] ^= AES_CMAC_CONST_RB;
72
73 /* compute the AES-CMAC value */
74 for (i = 0; i < num_aes_blocks; i++) {
75 /* Apply the chain data */
76 aes_apply_cbc_chain_data(cbc_chain_data, src, tmp_data);
77
78 /* for the final block, XOR K1 into the IV */
79 if (i == num_aes_blocks - 1)
80 aes_apply_cbc_chain_data(tmp_data, k1, tmp_data);
81
82 /* encrypt the AES block */
83 aes_encrypt(AES128_KEY_LENGTH, tmp_data,
84 key_schedule, dst);
85
86 debug("sign_obj: block %d of %d\n", i, num_aes_blocks);
87
88 /* Update pointers for next loop. */
89 cbc_chain_data = dst;
90 src += AES128_KEY_LENGTH;
91 }
92 }
93
94 /**
95 * Encrypt and sign a block of data (depending on security mode).
96 *
97 * \param key Input AES key, length AES128_KEY_LENGTH
98 * \param oper Security operations mask to perform (enum security_op)
99 * \param src Source data
100 * \param length Size of source data
101 * \param sig_dst Destination address for signature, AES128_KEY_LENGTH bytes
102 */
encrypt_and_sign(u8 * key,enum security_op oper,u8 * src,u32 length,u8 * sig_dst)103 static int encrypt_and_sign(u8 *key, enum security_op oper, u8 *src,
104 u32 length, u8 *sig_dst)
105 {
106 u32 num_aes_blocks;
107 u8 key_schedule[AES128_EXPAND_KEY_LENGTH];
108 u8 iv[AES128_KEY_LENGTH] = {0};
109
110 debug("encrypt_and_sign: length = %d\n", length);
111
112 /*
113 * The only need for a key is for signing/checksum purposes, so
114 * if not encrypting, expand a key of 0s.
115 */
116 aes_expand_key(oper & SECURITY_ENCRYPT ? key : zero_key,
117 AES128_KEY_LENGTH, key_schedule);
118
119 num_aes_blocks = (length + AES128_KEY_LENGTH - 1) / AES128_KEY_LENGTH;
120
121 if (oper & SECURITY_ENCRYPT) {
122 /* Perform this in place, resulting in src being encrypted. */
123 debug("encrypt_and_sign: begin encryption\n");
124 aes_cbc_encrypt_blocks(AES128_KEY_LENGTH, key_schedule, iv, src,
125 src, num_aes_blocks);
126 debug("encrypt_and_sign: end encryption\n");
127 }
128
129 if (oper & SECURITY_SIGN) {
130 /* encrypt the data, overwriting the result in signature. */
131 debug("encrypt_and_sign: begin signing\n");
132 sign_object(key, key_schedule, src, sig_dst, num_aes_blocks);
133 debug("encrypt_and_sign: end signing\n");
134 }
135
136 return 0;
137 }
138
sign_data_block(u8 * source,unsigned length,u8 * signature)139 int sign_data_block(u8 *source, unsigned length, u8 *signature)
140 {
141 return encrypt_and_sign(zero_key, SECURITY_SIGN, source,
142 length, signature);
143 }
144