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