/*
* Copyright 2014-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <string.h>
#include <openssl/crypto.h>
#include <openssl/err.h>
#include "modes_local.h"
#ifndef OPENSSL_NO_OCB
/*
* Calculate the number of binary trailing zero's in any given number
*/
static u32 ocb_ntz(u64 n)
{
u32 cnt = 0;
/*
* We do a right-to-left simple sequential search. This is surprisingly
* efficient as the distribution of trailing zeros is not uniform,
* e.g. the number of possible inputs with no trailing zeros is equal to
* the number with 1 or more; the number with exactly 1 is equal to the
* number with 2 or more, etc. Checking the last two bits covers 75% of
* all numbers. Checking the last three covers 87.5%
*/
while (!(n & 1)) {
n >>= 1;
cnt++;
}
return cnt;
}
/*
* Shift a block of 16 bytes left by shift bits
*/
static void ocb_block_lshift(const unsigned char *in, size_t shift,
unsigned char *out)
{
int i;
unsigned char carry = 0, carry_next;
for (i = 15; i >= 0; i--) {
carry_next = in[i] >> (8 - shift);
out[i] = (in[i] << shift) | carry;
carry = carry_next;
}
}
/*
* Perform a "double" operation as per OCB spec
*/
static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)
{
unsigned char mask;
/*
* Calculate the mask based on the most significant bit. There are more
* efficient ways to do this - but this way is constant time
*/
mask = in->c[0] & 0x80;
mask >>= 7;
mask = (0 - mask) & 0x87;
ocb_block_lshift(in->c, 1, out->c);
out->c[15] ^= mask;
}
/*
* Perform an xor on in1 and in2 - each of len bytes. Store result in out
*/
static void ocb_block_xor(const unsigned char *in1,
const unsigned char *in2, size_t len,
unsigned char *out)
{
size_t i;
for (i = 0; i < len; i++) {
out[i] = in1[i] ^ in2[i];
}
}
/*
* Lookup L_index in our lookup table. If we haven't already got it we need to
* calculate it
*/
static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT *ctx, size_t idx)
{
size_t l_index = ctx->l_index;
if (idx <= l_index) {
return ctx->l + idx;
}
/* We don't have it - so calculate it */
if (idx >= ctx->max_l_index) {
void *tmp_ptr;
/*
* Each additional entry allows to process almost double as
* much data, so that in linear world the table will need to
* be expanded with smaller and smaller increments. Originally
* it was doubling in size, which was a waste. Growing it
* linearly is not formally optimal, but is simpler to implement.
* We grow table by minimally required 4*n that would accommodate
* the index.
*/
ctx->max_l_index += (idx - ctx->max_l_index + 4) & ~3;
tmp_ptr = OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
if (tmp_ptr == NULL) /* prevent ctx->l from being clobbered */
return NULL;
ctx->l = tmp_ptr;
}
while (l_index < idx) {
ocb_double(ctx->l + l_index, ctx->l + l_index + 1);
l_index++;
}
ctx->l_index = l_index;
return ctx->l + idx;
}
/*
* Create a new OCB128_CONTEXT
*/
OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
block128_f encrypt, block128_f decrypt,
ocb128_f stream)
{
OCB128_CONTEXT *octx;
int ret;
if ((octx = OPENSSL_malloc(sizeof(*octx))) != NULL) {
ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt,
stream);
if (ret)
return octx;
OPENSSL_free(octx);
}
return NULL;
}
/*
* Initialise an existing OCB128_CONTEXT
*/
int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
block128_f encrypt, block128_f decrypt,
ocb128_f stream)
{
memset(ctx, 0, sizeof(*ctx));
ctx->l_index = 0;
ctx->max_l_index = 5;
if ((ctx->l = OPENSSL_malloc(ctx->max_l_index * 16)) == NULL) {
CRYPTOerr(CRYPTO_F_CRYPTO_OCB128_INIT, ERR_R_MALLOC_FAILURE);
return 0;
}
/*
* We set both the encryption and decryption key schedules - decryption
* needs both. Don't really need decryption schedule if only doing
* encryption - but it simplifies things to take it anyway
*/
ctx->encrypt = encrypt;
ctx->decrypt = decrypt;
ctx->stream = stream;
ctx->keyenc = keyenc;
ctx->keydec = keydec;
/* L_* = ENCIPHER(K, zeros(128)) */
ctx->encrypt(ctx->l_star.c, ctx->l_star.c, ctx->keyenc);
/* L_$ = double(L_*) */
ocb_double(&ctx->l_star, &ctx->l_dollar);
/* L_0 = double(L_$) */
ocb_double(&ctx->l_dollar, ctx->l);
/* L_{i} = double(L_{i-1}) */
ocb_double(ctx->l, ctx->l+1);
ocb_double(ctx->l+1, ctx->l+2);
ocb_double(ctx->l+2, ctx->l+3);
ocb_double(ctx->l+3, ctx->l+4);
ctx->l_index = 4; /* enough to process up to 496 bytes */
return 1;
}
/*
* Copy an OCB128_CONTEXT object
*/
int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,
void *keyenc, void *keydec)
{
memcpy(dest, src, sizeof(OCB128_CONTEXT));
if (keyenc)
dest->keyenc = keyenc;
if (keydec)
dest->keydec = keydec;
if (src->l) {
if ((dest->l = OPENSSL_malloc(src->max_l_index * 16)) == NULL) {
CRYPTOerr(CRYPTO_F_CRYPTO_OCB128_COPY_CTX, ERR_R_MALLOC_FAILURE);
return 0;
}
memcpy(dest->l, src->l, (src->l_index + 1) * 16);
}
return 1;
}
/*
* Set the IV to be used for this operation. Must be 1 - 15 bytes.
*/
int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,
size_t len, size_t taglen)
{
unsigned char ktop[16], tmp[16], mask;
unsigned char stretch[24], nonce[16];
size_t bottom, shift;
/*
* Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
* We don't support this at this stage
*/
if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
return -1;
}
/* Reset nonce-dependent variables */
memset(&ctx->sess, 0, sizeof(ctx->sess));
/* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
nonce[0] = ((taglen * 8) % 128) << 1;
memset(nonce + 1, 0, 15);
memcpy(nonce + 16 - len, iv, len);
nonce[15 - len] |= 1;
/* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
memcpy(tmp, nonce, 16);
tmp[15] &= 0xc0;
ctx->encrypt(tmp, ktop, ctx->keyenc);
/* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
memcpy(stretch, ktop, 16);
ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
/* bottom = str2num(Nonce[123..128]) */
bottom = nonce[15] & 0x3f;
/* Offset_0 = Stretch[1+bottom..128+bottom] */
shift = bottom % 8;
ocb_block_lshift(stretch + (bottom / 8), shift, ctx->sess.offset.c);
mask = 0xff;
mask <<= 8 - shift;
ctx->sess.offset.c[15] |=
(*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
return 1;
}
/*
* Provide any AAD. This can be called multiple times. Only the final time can
* have a partial block
*/
int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
size_t len)
{
u64 i, all_num_blocks;
size_t num_blocks, last_len;
OCB_BLOCK tmp;
/* Calculate the number of blocks of AAD provided now, and so far */
num_blocks = len / 16;
all_num_blocks = num_blocks + ctx->sess.blocks_hashed;
/* Loop through all full blocks of AAD */
for (i = ctx->sess.blocks_hashed + 1; i <= all_num_blocks; i++) {
OCB_BLOCK *lookup;
/* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
lookup = ocb_lookup_l(ctx, ocb_ntz(i));
if (lookup == NULL)
return 0;
ocb_block16_xor(&ctx->sess.offset_aad, lookup, &ctx->sess.offset_aad);
memcpy(tmp.c, aad, 16);
aad += 16;
/* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
ocb_block16_xor(&ctx->sess.offset_aad, &tmp, &tmp);
ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
ocb_block16_xor(&tmp, &ctx->sess.sum, &ctx->sess.sum);
}
/*
* Check if we have any partial blocks left over. This is only valid in the
* last call to this function
*/
last_len = len % 16;
if (last_len > 0) {
/* Offset_* = Offset_m xor L_* */
ocb_block16_xor(&ctx->sess.offset_aad, &ctx->l_star,
&ctx->sess.offset_aad);
/* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
memset(tmp.c, 0, 16);
memcpy(tmp.c, aad, last_len);
tmp.c[last_len] = 0x80;
ocb_block16_xor(&ctx->sess.offset_aad, &tmp, &tmp);
/* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
ocb_block16_xor(&tmp, &ctx->sess.sum, &ctx->sess.sum);
}
ctx->sess.blocks_hashed = all_num_blocks;
return 1;
}
/*
* Provide any data to be encrypted. This can be called multiple times. Only
* the final time can have a partial block
*/
int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
const unsigned char *in, unsigned char *out,
size_t len)
{
u64 i, all_num_blocks;
size_t num_blocks, last_len;
/*
* Calculate the number of blocks of data to be encrypted provided now, and
* so far
*/
num_blocks = len / 16;
all_num_blocks = num_blocks + ctx->sess.blocks_processed;
if (num_blocks && all_num_blocks == (size_t)all_num_blocks
&& ctx->stream != NULL) {
size_t max_idx = 0, top = (size_t)all_num_blocks;
/*
* See how many L_{i} entries we need to process data at hand
* and pre-compute missing entries in the table [if any]...
*/
while (top >>= 1)
max_idx++;
if (ocb_lookup_l(ctx, max_idx) == NULL)
return 0;
ctx->stream(in, out, num_blocks, ctx->keyenc,
(size_t)ctx->sess.blocks_processed + 1, ctx->sess.offset.c,
(const unsigned char (*)[16])ctx->l, ctx->sess.checksum.c);
} else {
/* Loop through all full blocks to be encrypted */
for (i = ctx->sess.blocks_processed + 1; i <= all_num_blocks; i++) {
OCB_BLOCK *lookup;
OCB_BLOCK tmp;
/* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
lookup = ocb_lookup_l(ctx, ocb_ntz(i));
if (lookup == NULL)
return 0;
ocb_block16_xor(&ctx->sess.offset, lookup, &ctx->sess.offset);
memcpy(tmp.c, in, 16);
in += 16;
/* Checksum_i = Checksum_{i-1} xor P_i */
ocb_block16_xor(&tmp, &ctx->sess.checksum, &ctx->sess.checksum);
/* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
memcpy(out, tmp.c, 16);
out += 16;
}
}
/*
* Check if we have any partial blocks left over. This is only valid in the
* last call to this function
*/
last_len = len % 16;
if (last_len > 0) {
OCB_BLOCK pad;
/* Offset_* = Offset_m xor L_* */
ocb_block16_xor(&ctx->sess.offset, &ctx->l_star, &ctx->sess.offset);
/* Pad = ENCIPHER(K, Offset_*) */
ctx->encrypt(ctx->sess.offset.c, pad.c, ctx->keyenc);
/* C_* = P_* xor Pad[1..bitlen(P_*)] */
ocb_block_xor(in, pad.c, last_len, out);
/* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
memset(pad.c, 0, 16); /* borrow pad */
memcpy(pad.c, in, last_len);
pad.c[last_len] = 0x80;
ocb_block16_xor(&pad, &ctx->sess.checksum, &ctx->sess.checksum);
}
ctx->sess.blocks_processed = all_num_blocks;
return 1;
}
/*
* Provide any data to be decrypted. This can be called multiple times. Only
* the final time can have a partial block
*/
int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
const unsigned char *in, unsigned char *out,
size_t len)
{
u64 i, all_num_blocks;
size_t num_blocks, last_len;
/*
* Calculate the number of blocks of data to be decrypted provided now, and
* so far
*/
num_blocks = len / 16;
all_num_blocks = num_blocks + ctx->sess.blocks_processed;
if (num_blocks && all_num_blocks == (size_t)all_num_blocks
&& ctx->stream != NULL) {
size_t max_idx = 0, top = (size_t)all_num_blocks;
/*
* See how many L_{i} entries we need to process data at hand
* and pre-compute missing entries in the table [if any]...
*/
while (top >>= 1)
max_idx++;
if (ocb_lookup_l(ctx, max_idx) == NULL)
return 0;
ctx->stream(in, out, num_blocks, ctx->keydec,
(size_t)ctx->sess.blocks_processed + 1, ctx->sess.offset.c,
(const unsigned char (*)[16])ctx->l, ctx->sess.checksum.c);
} else {
OCB_BLOCK tmp;
/* Loop through all full blocks to be decrypted */
for (i = ctx->sess.blocks_processed + 1; i <= all_num_blocks; i++) {
/* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
if (lookup == NULL)
return 0;
ocb_block16_xor(&ctx->sess.offset, lookup, &ctx->sess.offset);
memcpy(tmp.c, in, 16);
in += 16;
/* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
ctx->decrypt(tmp.c, tmp.c, ctx->keydec);
ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);
/* Checksum_i = Checksum_{i-1} xor P_i */
ocb_block16_xor(&tmp, &ctx->sess.checksum, &ctx->sess.checksum);
memcpy(out, tmp.c, 16);
out += 16;
}
}
/*
* Check if we have any partial blocks left over. This is only valid in the
* last call to this function
*/
last_len = len % 16;
if (last_len > 0) {
OCB_BLOCK pad;
/* Offset_* = Offset_m xor L_* */
ocb_block16_xor(&ctx->sess.offset, &ctx->l_star, &ctx->sess.offset);
/* Pad = ENCIPHER(K, Offset_*) */
ctx->encrypt(ctx->sess.offset.c, pad.c, ctx->keyenc);
/* P_* = C_* xor Pad[1..bitlen(C_*)] */
ocb_block_xor(in, pad.c, last_len, out);
/* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
memset(pad.c, 0, 16); /* borrow pad */
memcpy(pad.c, out, last_len);
pad.c[last_len] = 0x80;
ocb_block16_xor(&pad, &ctx->sess.checksum, &ctx->sess.checksum);
}
ctx->sess.blocks_processed = all_num_blocks;
return 1;
}
static int ocb_finish(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len,
int write)
{
OCB_BLOCK tmp;
if (len > 16 || len < 1) {
return -1;
}
/*
* Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
*/
ocb_block16_xor(&ctx->sess.checksum, &ctx->sess.offset, &tmp);
ocb_block16_xor(&ctx->l_dollar, &tmp, &tmp);
ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);
ocb_block16_xor(&tmp, &ctx->sess.sum, &tmp);
if (write) {
memcpy(tag, &tmp, len);
return 1;
} else {
return CRYPTO_memcmp(&tmp, tag, len);
}
}
/*
* Calculate the tag and verify it against the supplied tag
*/
int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
size_t len)
{
return ocb_finish(ctx, (unsigned char*)tag, len, 0);
}
/*
* Retrieve the calculated tag
*/
int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
{
return ocb_finish(ctx, tag, len, 1);
}
/*
* Release all resources
*/
void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
{
if (ctx) {
OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
OPENSSL_cleanse(ctx, sizeof(*ctx));
}
}
#endif /* OPENSSL_NO_OCB */