busybox/networking/tls_aes.c

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/*
* Copyright (C) 2017 Denys Vlasenko
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
/* This AES implementation is derived from tiny-AES128-C code,
* which was put by its author into public domain:
*
* tiny-AES128-C/unlicense.txt, Dec 8, 2014
* """
* This is free and unencumbered software released into the public domain.
*
* Anyone is free to copy, modify, publish, use, compile, sell, or
* distribute this software, either in source code form or as a compiled
* binary, for any purpose, commercial or non-commercial, and by any
* means.
*
* In jurisdictions that recognize copyright laws, the author or authors
* of this software dedicate any and all copyright interest in the
* software to the public domain. We make this dedication for the benefit
* of the public at large and to the detriment of our heirs and
* successors. We intend this dedication to be an overt act of
* relinquishment in perpetuity of all present and future rights to this
* software under copyright law.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
* """
*/
/* Note that only original tiny-AES128-C code is public domain.
* The derived code in this file has been expanded to also implement aes192
* and aes256 and use more efficient word-sized operations in many places,
* and put under GPLv2 license.
*/
#include "tls.h"
// The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
// The numbers below can be computed dynamically trading ROM for RAM -
// This can be useful in (embedded) bootloader applications, where ROM is often limited.
static const uint8_t sbox[] = {
0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
};
static const uint8_t rsbox[] = {
0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d,
0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2,
0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea,
0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20,
0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31,
0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0,
0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26,
0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
};
// SubWord() is a function that takes a four-byte input word and
// applies the S-box to each of the four bytes to produce an output word.
static uint32_t Subword(uint32_t x)
{
return (sbox[(x >> 24) ] << 24)
| (sbox[(x >> 16) & 255] << 16)
| (sbox[(x >> 8 ) & 255] << 8 )
| (sbox[(x ) & 255] );
}
// This function produces Nb(Nr+1) round keys.
// The round keys are used in each round to decrypt the states.
static int KeyExpansion(uint32_t *RoundKey, const void *key, unsigned key_len)
{
// The round constant word array, Rcon[i], contains the values given by
// x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8).
// Note that i starts at 2, not 0.
static const uint8_t Rcon[] = {
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36
//..... 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6,...
// but aes256 only uses values up to 0x36
};
int rounds, words_key, words_RoundKey;
int i, j, k;
// key_len 16: aes128, rounds 10, words_key 4, words_RoundKey 44
// key_len 24: aes192, rounds 12, words_key 6, words_RoundKey 52
// key_len 32: aes256, rounds 14, words_key 8, words_RoundKey 60
words_key = key_len / 4;
rounds = 6 + (key_len / 4);
words_RoundKey = 28 + key_len;
// The first round key is the key itself.
for (i = 0; i < words_key; i++)
RoundKey[i] = get_unaligned_be32((uint32_t*)key + i);
// i == words_key now
// All other round keys are found from the previous round keys.
j = k = 0;
for (; i < words_RoundKey; i++) {
uint32_t tempa;
tempa = RoundKey[i - 1];
if (j == 0) {
// RotWord(): rotates the 4 bytes in a word to the left once.
tempa = (tempa << 8) | (tempa >> 24);
tempa = Subword(tempa);
tempa ^= (uint32_t)Rcon[k] << 24;
} else if (words_key > 6 && j == 4) {
tempa = Subword(tempa);
}
RoundKey[i] = RoundKey[i - words_key] ^ tempa;
j++;
if (j == words_key) {
j = 0;
k++;
}
}
return rounds;
}
// This function adds the round key to state.
// The round key is added to the state by an XOR function.
static void AddRoundKey(unsigned astate[16], const uint32_t *RoundKeys)
{
int i;
for (i = 0; i < 16; i += 4) {
uint32_t n = *RoundKeys++;
astate[i + 0] ^= (n >> 24);
astate[i + 1] ^= (n >> 16) & 255;
astate[i + 2] ^= (n >> 8) & 255;
astate[i + 3] ^= n & 255;
}
}
// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void SubBytes(unsigned astate[16])
{
int i;
for (i = 0; i < 16; i++)
astate[i] = sbox[astate[i]];
}
// Our code actually stores "columns" (in aes encryption terminology)
// of state in rows: first 4 elements are "row 0, col 0", "row 1, col 0".
// "row 2, col 0", "row 3, col 0". The fifth element is "row 0, col 1",
// and so on.
#define ASTATE(col,row) astate[(col)*4 + (row)]
// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
static void ShiftRows(unsigned astate[16])
{
unsigned v;
// Rotate first row 1 columns to left
v = ASTATE(0,1);
ASTATE(0,1) = ASTATE(1,1);
ASTATE(1,1) = ASTATE(2,1);
ASTATE(2,1) = ASTATE(3,1);
ASTATE(3,1) = v;
// Rotate second row 2 columns to left
v = ASTATE(0,2); ASTATE(0,2) = ASTATE(2,2); ASTATE(2,2) = v;
v = ASTATE(1,2); ASTATE(1,2) = ASTATE(3,2); ASTATE(3,2) = v;
// Rotate third row 3 columns to left
v = ASTATE(3,3);
ASTATE(3,3) = ASTATE(2,3);
ASTATE(2,3) = ASTATE(1,3);
ASTATE(1,3) = ASTATE(0,3);
ASTATE(0,3) = v;
}
// MixColumns function mixes the columns of the state matrix
static void MixColumns(unsigned astate[16])
{
int i;
for (i = 0; i < 16; i += 4) {
unsigned a, b, c, d;
unsigned x, y, z, t;
a = astate[i + 0];
b = astate[i + 1];
c = astate[i + 2];
d = astate[i + 3];
x = (a << 1) ^ b ^ (b << 1) ^ c ^ d;
y = a ^ (b << 1) ^ c ^ (c << 1) ^ d;
z = a ^ b ^ (c << 1) ^ d ^ (d << 1);
t = a ^ (a << 1) ^ b ^ c ^ (d << 1);
astate[i + 0] = x ^ ((-(int)(x >> 8)) & 0x11b);
astate[i + 1] = y ^ ((-(int)(y >> 8)) & 0x11b);
astate[i + 2] = z ^ ((-(int)(z >> 8)) & 0x11b);
astate[i + 3] = t ^ ((-(int)(t >> 8)) & 0x11b);
}
}
// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void InvSubBytes(unsigned astate[16])
{
int i;
for (i = 0; i < 16; i++)
astate[i] = rsbox[astate[i]];
}
static void InvShiftRows(unsigned astate[16])
{
unsigned v;
// Rotate first row 1 columns to right
v = ASTATE(3,1);
ASTATE(3,1) = ASTATE(2,1);
ASTATE(2,1) = ASTATE(1,1);
ASTATE(1,1) = ASTATE(0,1);
ASTATE(0,1) = v;
// Rotate second row 2 columns to right
v = ASTATE(0,2); ASTATE(0,2) = ASTATE(2,2); ASTATE(2,2) = v;
v = ASTATE(1,2); ASTATE(1,2) = ASTATE(3,2); ASTATE(3,2) = v;
// Rotate third row 3 columns to right
v = ASTATE(0,3);
ASTATE(0,3) = ASTATE(1,3);
ASTATE(1,3) = ASTATE(2,3);
ASTATE(2,3) = ASTATE(3,3);
ASTATE(3,3) = v;
}
static ALWAYS_INLINE unsigned Multiply(unsigned x)
{
unsigned y;
y = x >> 8;
return (x ^ y ^ (y << 1) ^ (y << 3) ^ (y << 4)) & 255;
}
// MixColumns function mixes the columns of the state matrix.
// The method used to multiply may be difficult to understand for the inexperienced.
// Please use the references to gain more information.
static void InvMixColumns(unsigned astate[16])
{
int i;
for (i = 0; i < 16; i += 4) {
unsigned a, b, c, d;
unsigned x, y, z, t;
a = astate[i + 0];
b = astate[i + 1];
c = astate[i + 2];
d = astate[i + 3];
x = (a << 1) ^ (a << 2) ^ (a << 3) ^ b ^ (b << 1) ^ (b << 3)
/***/ ^ c ^ (c << 2) ^ (c << 3) ^ d ^ (d << 3);
y = a ^ (a << 3) ^ (b << 1) ^ (b << 2) ^ (b << 3)
/***/ ^ c ^ (c << 1) ^ (c << 3) ^ d ^ (d << 2) ^ (d << 3);
z = a ^ (a << 2) ^ (a << 3) ^ b ^ (b << 3)
/***/ ^ (c << 1) ^ (c << 2) ^ (c << 3) ^ d ^ (d << 1) ^ (d << 3);
t = a ^ (a << 1) ^ (a << 3) ^ b ^ (b << 2) ^ (b << 3)
/***/ ^ c ^ (c << 3) ^ (d << 1) ^ (d << 2) ^ (d << 3);
astate[i + 0] = Multiply(x);
astate[i + 1] = Multiply(y);
astate[i + 2] = Multiply(z);
astate[i + 3] = Multiply(t);
}
}
static void aes_encrypt_1(struct tls_aes *aes, unsigned astate[16])
{
unsigned rounds = aes->rounds;
const uint32_t *RoundKey = aes->key;
for (;;) {
AddRoundKey(astate, RoundKey);
RoundKey += 4;
SubBytes(astate);
ShiftRows(astate);
if (--rounds == 0)
break;
MixColumns(astate);
}
AddRoundKey(astate, RoundKey);
}
void FAST_FUNC aes_setkey(struct tls_aes *aes, const void *key, unsigned key_len)
{
aes->rounds = KeyExpansion(aes->key, key, key_len);
}
void FAST_FUNC aes_encrypt_one_block(struct tls_aes *aes, const void *data, void *dst)
{
unsigned astate[16];
unsigned i;
const uint8_t *pt = data;
uint8_t *ct = dst;
for (i = 0; i < 16; i++)
astate[i] = pt[i];
aes_encrypt_1(aes, astate);
for (i = 0; i < 16; i++)
ct[i] = astate[i];
}
void FAST_FUNC aes_cbc_encrypt(struct tls_aes *aes, void *iv, const void *data, size_t len, void *dst)
{
uint8_t iv2[16];
const uint8_t *pt = data;
uint8_t *ct = dst;
memcpy(iv2, iv, 16);
while (len > 0) {
{
/* almost aes_encrypt_one_block(rounds, RoundKey, pt, ct);
* but xor'ing of IV with plaintext[] is combined
* with plaintext[] -> astate[]
*/
int i;
unsigned astate[16];
for (i = 0; i < 16; i++)
astate[i] = pt[i] ^ iv2[i];
aes_encrypt_1(aes, astate);
for (i = 0; i < 16; i++)
iv2[i] = ct[i] = astate[i];
}
ct += 16;
pt += 16;
len -= 16;
}
}
static void aes_decrypt_1(struct tls_aes *aes, unsigned astate[16])
{
unsigned rounds = aes->rounds;
const uint32_t *RoundKey = aes->key;
RoundKey += rounds * 4;
AddRoundKey(astate, RoundKey);
for (;;) {
InvShiftRows(astate);
InvSubBytes(astate);
RoundKey -= 4;
AddRoundKey(astate, RoundKey);
if (--rounds == 0)
break;
InvMixColumns(astate);
}
}
#if 0 //UNUSED
static void aes_decrypt_one_block(struct tls_aes *aes, const void *data, void *dst)
{
unsigned rounds = aes->rounds;
const uint32_t *RoundKey = aes->key;
unsigned astate[16];
unsigned i;
const uint8_t *ct = data;
uint8_t *pt = dst;
for (i = 0; i < 16; i++)
astate[i] = ct[i];
aes_decrypt_1(aes, astate);
for (i = 0; i < 16; i++)
pt[i] = astate[i];
}
#endif
void FAST_FUNC aes_cbc_decrypt(struct tls_aes *aes, void *iv, const void *data, size_t len, void *dst)
{
uint8_t iv2[16];
uint8_t iv3[16];
uint8_t *ivbuf;
uint8_t *ivnext;
const uint8_t *ct = data;
uint8_t *pt = dst;
ivbuf = memcpy(iv2, iv, 16);
while (len) {
ivnext = (ivbuf==iv2) ? iv3 : iv2;
{
/* almost aes_decrypt_one_block(rounds, RoundKey, ct, pt)
* but xor'ing of ivbuf is combined with astate[] -> plaintext[]
*/
int i;
unsigned astate[16];
for (i = 0; i < 16; i++)
ivnext[i] = astate[i] = ct[i];
aes_decrypt_1(aes, astate);
for (i = 0; i < 16; i++)
pt[i] = astate[i] ^ ivbuf[i];
}
ivbuf = ivnext;
ct += 16;
pt += 16;
len -= 16;
}
}