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Fix AES XTS mode key size.

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I screwed up the |EVP_CIPHER| parameters for XTS when I first imported
it, and there were no tests to catch it.  (The problem was that
|EVP_CIPH_XTS_MODE| means “the key size is actually twice what it says
here.”)

With these changes, OpenSSL's tests pass.

(Along the way, make a few other things about XTS slightly less
decrepit.)

Change-Id: Icbfbc5e6d532d1c132392ee366f9cab42802d674
Reviewed-on: https://boringssl-review.googlesource.com/6529
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
Matt Braithwaite 2015-11-18 19:27:02 -08:00 committed by Adam Langley
parent 93a5b44296
commit e8fe07fcc4
1 changed files with 23 additions and 61 deletions
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64
decrepit/xts/xts.c
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@ -56,12 +56,6 @@
#include "../crypto/modes/internal.h"
#if defined(OPENSSL_X86_64) || defined(OPENSSL_X86) || defined(OPENSSL_AARCH64)
#define STRICT_ALIGNMENT 0
#else
#define STRICT_ALIGNMENT 1
#endif
typedef struct xts128_context {
void *key1, *key2;
block128_f block1, block2;
@ -70,10 +64,6 @@ typedef struct xts128_context {
static size_t CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx,
const uint8_t iv[16], const uint8_t *inp,
uint8_t *out, size_t len, int enc) {
const union {
long one;
char little;
} is_endian = {1};
union {
uint64_t u[2];
uint32_t d[4];
@ -90,22 +80,22 @@ static size_t CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx,
if (!enc && (len % 16)) len -= 16;
while (len >= 16) {
#if defined(STRICT_ALIGNMENT)
#if STRICT_ALIGNMENT
memcpy(scratch.c, inp, 16);
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
#else
scratch.u[0] = ((unint64_t *)inp)[0] ^ tweak.u[0];
scratch.u[1] = ((unint64_t *)inp)[1] ^ tweak.u[1];
scratch.u[0] = ((uint64_t *)inp)[0] ^ tweak.u[0];
scratch.u[1] = ((uint64_t *)inp)[1] ^ tweak.u[1];
#endif
(*ctx->block1)(scratch.c, scratch.c, ctx->key1);
#if defined(STRICT_ALIGNMENT)
#if STRICT_ALIGNMENT
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
memcpy(out, scratch.c, 16);
#else
((unint64_t *)out)[0] = scratch.u[0] ^= tweak.u[0];
((unint64_t *)out)[1] = scratch.u[1] ^= tweak.u[1];
((uint64_t *)out)[0] = scratch.u[0] ^= tweak.u[0];
((uint64_t *)out)[1] = scratch.u[1] ^= tweak.u[1];
#endif
inp += 16;
out += 16;
@ -113,26 +103,12 @@ static size_t CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx,
if (len == 0) return 1;
if (is_endian.little) {
unsigned int carry, res;
res = 0x87 & (((int)tweak.d[3]) >> 31);
carry = (unsigned int)(tweak.u[0] >> 63);
tweak.u[0] = (tweak.u[0] << 1) ^ res;
tweak.u[1] = (tweak.u[1] << 1) | carry;
} else {
size_t c;
for (c = 0, i = 0; i < 16; ++i) {
/*
* + substitutes for |, because c is 1 bit
*/
c += ((size_t)tweak.c[i]) << 1;
tweak.c[i] = (uint8_t)c;
c = c >> 8;
}
tweak.c[0] ^= (uint8_t)(0x87 & (0 - c));
}
}
if (enc) {
for (i = 0; i < len; ++i) {
@ -152,33 +128,19 @@ static size_t CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx,
uint8_t c[16];
} tweak1;
if (is_endian.little) {
unsigned int carry, res;
res = 0x87 & (((int)tweak.d[3]) >> 31);
carry = (unsigned int)(tweak.u[0] >> 63);
tweak1.u[0] = (tweak.u[0] << 1) ^ res;
tweak1.u[1] = (tweak.u[1] << 1) | carry;
} else {
size_t c;
for (c = 0, i = 0; i < 16; ++i) {
/*
* + substitutes for |, because c is 1 bit
*/
c += ((size_t)tweak.c[i]) << 1;
tweak1.c[i] = (uint8_t)c;
c = c >> 8;
}
tweak1.c[0] ^= (uint8_t)(0x87 & (0 - c));
}
#if defined(STRICT_ALIGNMENT)
#if STRICT_ALIGNMENT
memcpy(scratch.c, inp, 16);
scratch.u[0] ^= tweak1.u[0];
scratch.u[1] ^= tweak1.u[1];
#else
scratch.u[0] = ((unint64_t *)inp)[0] ^ tweak1.u[0];
scratch.u[1] = ((unint64_t *)inp)[1] ^ tweak1.u[1];
scratch.u[0] = ((uint64_t *)inp)[0] ^ tweak1.u[0];
scratch.u[1] = ((uint64_t *)inp)[1] ^ tweak1.u[1];
#endif
(*ctx->block1)(scratch.c, scratch.c, ctx->key1);
scratch.u[0] ^= tweak1.u[0];
@ -192,13 +154,13 @@ static size_t CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx,
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
(*ctx->block1)(scratch.c, scratch.c, ctx->key1);
#if defined(STRICT_ALIGNMENT)
#if STRICT_ALIGNMENT
scratch.u[0] ^= tweak.u[0];
scratch.u[1] ^= tweak.u[1];
memcpy(out, scratch.c, 16);
#else
((unint64_t *)out)[0] = scratch.u[0] ^ tweak.u[0];
((unint64_t *)out)[1] = scratch.u[1] ^ tweak.u[1];
((uint64_t *)out)[0] = scratch.u[0] ^ tweak.u[0];
((uint64_t *)out)[1] = scratch.u[1] ^ tweak.u[1];
#endif
}
@ -286,7 +248,7 @@ static int aes_xts_ctrl(EVP_CIPHER_CTX *c, int type, int arg, void *ptr) {
}
static const EVP_CIPHER aes_256_xts = {
NID_aes_256_xts, 1 /* block_size */, 32 /* key_size */,
NID_aes_256_xts, 1 /* block_size */, 64 /* key_size (2 AES keys) */,
16 /* iv_len */, sizeof(EVP_AES_XTS_CTX),
EVP_CIPH_XTS_MODE | EVP_CIPH_CUSTOM_IV | EVP_CIPH_ALWAYS_CALL_INIT |
EVP_CIPH_CTRL_INIT | EVP_CIPH_CUSTOM_COPY,