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/*
* 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 "uboot_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 iv[AES_KEY_LENGTH] = {0};
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, iv, 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];
u8 iv[AES_KEY_LENGTH] = {0};
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, iv, 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);
}
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