164 lines
4.1 KiB
C
164 lines
4.1 KiB
C
#include "aes_core.h"
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#define DEBUG(format, ...) \
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printf("[%s]:%d: " format "\n", __func__, __LINE__, ##__VA_ARGS__)
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static int aes_xts128_encrypt(const RK_AES_KEY *key1, const RK_AES_KEY *key2,
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const unsigned char iv[16],
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const unsigned char *inp, unsigned char *out,
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unsigned long len, int enc) {
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const union {
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long one;
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char little;
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} is_endian = {1};
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union {
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u64 u[2];
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u32 d[4];
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u8 c[16];
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} tweak, scratch;
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unsigned int i;
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if (len < 16)
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return -1;
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memcpy(tweak.c, iv, 16);
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rk_aes_encrypt(tweak.c, tweak.c, key2);
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if (!enc && (len % 16))
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len -= 16;
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while (len >= 16) {
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memcpy(scratch.c, inp, 16);
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scratch.u[0] ^= tweak.u[0];
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scratch.u[1] ^= tweak.u[1];
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if (enc)
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rk_aes_encrypt(scratch.c, scratch.c, key1);
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else
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rk_aes_decrypt(scratch.c, scratch.c, key1);
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scratch.u[0] ^= tweak.u[0];
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scratch.u[1] ^= tweak.u[1];
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memcpy(out, scratch.c, 16);
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inp += 16;
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out += 16;
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len -= 16;
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if (len == 0)
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return 0;
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if (is_endian.little) {
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unsigned int carry, res;
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res = 0x87 & (((int)tweak.d[3]) >> 31);
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carry = (unsigned int)(tweak.u[0] >> 63);
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tweak.u[0] = (tweak.u[0] << 1) ^ res;
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tweak.u[1] = (tweak.u[1] << 1) | carry;
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} else {
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size_t c;
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for (c = 0, i = 0; i < 16; ++i) {
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/*+ substitutes for |, because c is 1 bit */
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c += ((size_t)tweak.c[i]) << 1;
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tweak.c[i] = (u8)c;
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c = c >> 8;
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}
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tweak.c[0] ^= (u8)(0x87 & (0 - c));
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}
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}
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if (enc) {
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for (i = 0; i < len; ++i) {
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u8 c = inp[i];
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out[i] = scratch.c[i];
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scratch.c[i] = c;
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}
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scratch.u[0] ^= tweak.u[0];
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scratch.u[1] ^= tweak.u[1];
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rk_aes_encrypt(scratch.c, scratch.c, key1);
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scratch.u[0] ^= tweak.u[0];
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scratch.u[1] ^= tweak.u[1];
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memcpy(out - 16, scratch.c, 16);
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} else {
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union {
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u64 u[2];
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u8 c[16];
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} tweak1;
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if (is_endian.little) {
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unsigned int carry, res;
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res = 0x87 & (((int)tweak.d[3]) >> 31);
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carry = (unsigned int)(tweak.u[0] >> 63);
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tweak1.u[0] = (tweak.u[0] << 1) ^ res;
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tweak1.u[1] = (tweak.u[1] << 1) | carry;
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} else {
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size_t c;
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for (c = 0, i = 0; i < 16; ++i) {
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/*+ substitutes for |, because c is 1 bit */
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c += ((size_t)tweak.c[i]) << 1;
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tweak1.c[i] = (u8)c;
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c = c >> 8;
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}
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tweak1.c[0] ^= (u8)(0x87 & (0 - c));
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}
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memcpy(scratch.c, inp, 16);
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scratch.u[0] ^= tweak1.u[0];
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scratch.u[1] ^= tweak1.u[1];
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rk_aes_decrypt(scratch.c, scratch.c, key1);
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scratch.u[0] ^= tweak1.u[0];
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scratch.u[1] ^= tweak1.u[1];
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for (i = 0; i < len; ++i) {
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u8 c = inp[16 + i];
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out[16 + i] = scratch.c[i];
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scratch.c[i] = c;
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}
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scratch.u[0] ^= tweak.u[0];
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scratch.u[1] ^= tweak.u[1];
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rk_aes_decrypt(scratch.c, scratch.c, key1);
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scratch.u[0] ^= tweak.u[0];
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scratch.u[1] ^= tweak.u[1];
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memcpy(out, scratch.c, 16);
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}
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return 0;
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}
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/* XTS makes use of two different keys, usually generated by splitting
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* the supplied block cipher's key in half.
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* Because of the splitting, users wanting AES 256 and AES 128 encryption
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* will need to choose key sizes of 512 bits and 256 bits respectively.
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*/
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int rk_aes_xts_encrypt(const unsigned char *in, unsigned char *out,
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unsigned long length, const unsigned char *key,
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const int key_len, unsigned char *ivec, const int enc) {
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int ret;
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RK_AES_KEY ks1, ks2;
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if (key_len != 32 && key_len != 48 && key_len != 64)
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return -1;
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if (enc) {
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ret = rk_aes_set_encrypt_key(key, key_len * 4, &ks1);
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} else {
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ret = rk_aes_set_decrypt_key(key, key_len * 4, &ks1);
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}
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ret = rk_aes_set_encrypt_key(key + key_len / 2, key_len * 4, &ks2);
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if (ret != 0)
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return ret;
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return aes_xts128_encrypt(&ks1, &ks2, ivec, in, out, length, enc);
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}
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