2 * Copyright (c) 2011 The Chromium OS Authors.
3 * (C) Copyright 2010 - 2011 NVIDIA Corporation <www.nvidia.com>
5 * SPDX-License-Identifier: GPL-2.0+
13 static u8 zero_key[16];
15 #define AES_CMAC_CONST_RB 0x87 /* from RFC 4493, Figure 2.2 */
18 SECURITY_SIGN = 1 << 0, /* Sign the data */
19 SECURITY_ENCRYPT = 1 << 1, /* Encrypt the data */
23 * Shift a vector left by one bit
25 * \param in Input vector
26 * \param out Output vector
27 * \param size Length of vector in bytes
29 static void left_shift_vector(u8 *in, u8 *out, int size)
34 for (i = size - 1; i >= 0; i--) {
35 out[i] = (in[i] << 1) | carry;
36 carry = in[i] >> 7; /* get most significant bit */
41 * Sign a block of data, putting the result into dst.
43 * \param key Input AES key, length AES_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 AES_KEY_LENGTH
47 * \param num_aes_blocks Number of AES blocks to encrypt
49 static void sign_object(u8 *key, u8 *key_schedule, u8 *src, u8 *dst,
52 u8 tmp_data[AES_KEY_LENGTH];
53 u8 left[AES_KEY_LENGTH];
54 u8 k1[AES_KEY_LENGTH];
58 cbc_chain_data = zero_key; /* Convenient array of 0's for IV */
60 /* compute K1 constant needed by AES-CMAC calculation */
61 for (i = 0; i < AES_KEY_LENGTH; i++)
64 aes_cbc_encrypt_blocks(key_schedule, tmp_data, left, 1);
65 debug_print_vector("AES(key, nonce)", AES_KEY_LENGTH, left);
67 left_shift_vector(left, k1, sizeof(left));
68 debug_print_vector("L", AES_KEY_LENGTH, left);
70 if ((left[0] >> 7) != 0) /* get MSB of L */
71 k1[AES_KEY_LENGTH-1] ^= AES_CMAC_CONST_RB;
72 debug_print_vector("K1", AES_KEY_LENGTH, k1);
74 /* compute the AES-CMAC value */
75 for (i = 0; i < num_aes_blocks; i++) {
76 /* Apply the chain data */
77 apply_cbc_chain_data(cbc_chain_data, src, tmp_data);
79 /* for the final block, XOR K1 into the IV */
80 if (i == num_aes_blocks - 1)
81 apply_cbc_chain_data(tmp_data, k1, tmp_data);
83 /* encrypt the AES block */
84 aes_encrypt(tmp_data, key_schedule, dst);
86 debug("sign_obj: block %d of %d\n", i, num_aes_blocks);
87 debug_print_vector("AES-CMAC Src", AES_KEY_LENGTH, src);
88 debug_print_vector("AES-CMAC Xor", AES_KEY_LENGTH, tmp_data);
89 debug_print_vector("AES-CMAC Dst", AES_KEY_LENGTH, dst);
91 /* Update pointers for next loop. */
93 src += AES_KEY_LENGTH;
96 debug_print_vector("AES-CMAC Hash", AES_KEY_LENGTH, dst);
100 * Encrypt and sign a block of data (depending on security mode).
102 * \param key Input AES key, length AES_KEY_LENGTH
103 * \param oper Security operations mask to perform (enum security_op)
104 * \param src Source data
105 * \param length Size of source data
106 * \param sig_dst Destination address for signature, AES_KEY_LENGTH bytes
108 static int encrypt_and_sign(u8 *key, enum security_op oper, u8 *src,
109 u32 length, u8 *sig_dst)
112 u8 key_schedule[AES_EXPAND_KEY_LENGTH];
114 debug("encrypt_and_sign: length = %d\n", length);
115 debug_print_vector("AES key", AES_KEY_LENGTH, key);
118 * The only need for a key is for signing/checksum purposes, so
119 * if not encrypting, expand a key of 0s.
121 aes_expand_key(oper & SECURITY_ENCRYPT ? key : zero_key, key_schedule);
123 num_aes_blocks = (length + AES_KEY_LENGTH - 1) / AES_KEY_LENGTH;
125 if (oper & SECURITY_ENCRYPT) {
126 /* Perform this in place, resulting in src being encrypted. */
127 debug("encrypt_and_sign: begin encryption\n");
128 aes_cbc_encrypt_blocks(key_schedule, src, src, num_aes_blocks);
129 debug("encrypt_and_sign: end encryption\n");
132 if (oper & SECURITY_SIGN) {
133 /* encrypt the data, overwriting the result in signature. */
134 debug("encrypt_and_sign: begin signing\n");
135 sign_object(key, key_schedule, src, sig_dst, num_aes_blocks);
136 debug("encrypt_and_sign: end signing\n");
142 int sign_data_block(u8 *source, unsigned length, u8 *signature)
144 return encrypt_and_sign(zero_key, SECURITY_SIGN, source,