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Make GCM AES faster

Browse source 
13.22% mbedtls_aesni_gcm_mult
    13.03% mbedtls_gcm_update
     9.85% mbedtls_aesni_crypt_ecb

Overhead improvement (perf record)

    10.97% mbedtls_aesni_gcm_mult
    10.59% mbedtls_aesni_crypt_ecb
     2.26% mbedtls_gcm_update
This commit is contained in:
Justine Tunney 2021-07-06 07:07:18 -07:00
parent f8b9bd2b47
commit e51034bab3
10 changed files with 452 additions and 640 deletions
Download patch file Download diff file Expand all files Collapse all files

470
third_party/mbedtls/gcm.c vendored
View file

@ -1,4 +1,7 @@
#include "libc/bits/bits.h"
#include "libc/bits/likely.h"
#include "libc/nexgen32e/x86feature.h"
#include "libc/runtime/runtime.h"
#include "libc/str/str.h"
#include "third_party/mbedtls/aes.h"
#include "third_party/mbedtls/aesni.h"
@ -52,8 +55,16 @@ asm(".include \"libc/disclaimer.inc\"");
#define GCM_VALIDATE( cond ) \
MBEDTLS_INTERNAL_VALIDATE( cond )
/*
* Initialize a context
/**
* \brief This function initializes the specified GCM context,
* to make references valid, and prepares the context
* for mbedtls_gcm_setkey() or mbedtls_gcm_free().
*
* The function does not bind the GCM context to a particular
* cipher, nor set the key. For this purpose, use
* mbedtls_gcm_setkey().
*
* \param ctx The GCM context to initialize. This must not be \c NULL.
*/
void mbedtls_gcm_init( mbedtls_gcm_context *ctx )
{
@ -76,58 +87,60 @@ static int gcm_gen_table( mbedtls_gcm_context *ctx )
uint64_t vl, vh;
unsigned char h[16];
size_t olen = 0;
memset( h, 0, 16 );
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, h, 16, h, &olen ) ) != 0 )
return( ret );
/* pack h as two 64-bits ints, big-endian */
GET_UINT32_BE( hi, h, 0 );
GET_UINT32_BE( lo, h, 4 );
vh = (uint64_t) hi << 32 | lo;
GET_UINT32_BE( hi, h, 8 );
GET_UINT32_BE( lo, h, 12 );
vl = (uint64_t) hi << 32 | lo;
/* 8 = 1000 corresponds to 1 in GF(2^128) */
ctx->HL[8] = vl;
ctx->HH[8] = vh;
vh = READ64BE( h + 0 );
vl = READ64BE( h + 8 );
#if defined(MBEDTLS_AESNI_C) && defined(MBEDTLS_HAVE_X86_64)
/* With CLMUL support, we need only h, not the rest of the table */
if (X86_HAVE(AES) && X86_HAVE(PCLMUL)) return 0;
if (X86_HAVE(AES) && X86_HAVE(PCLMUL)) {
ctx->H8[0] = vl;
ctx->H8[1] = vh;
return 0;
}
#endif
/* 0 corresponds to 0 in GF(2^128) */
ctx->HH[0] = 0;
ctx->HL[0] = 0;
for( i = 4; i > 0; i >>= 1 )
{
/* 8 = 1000 corresponds to 1 in GF(2^128) */
ctx->HL[8] = vl;
ctx->HH[8] = vh;
for( i = 4; i > 0; i >>= 1 ) {
uint32_t T = ( vl & 1 ) * 0xe1000000U;
vl = ( vh << 63 ) | ( vl >> 1 );
vh = ( vh >> 1 ) ^ ( (uint64_t) T << 32);
ctx->HL[i] = vl;
ctx->HH[i] = vh;
}
for( i = 2; i <= 8; i *= 2 )
{
for( i = 2; i <= 8; i *= 2 ) {
uint64_t *HiL = ctx->HL + i, *HiH = ctx->HH + i;
vh = *HiH;
vl = *HiL;
for( j = 1; j < i; j++ )
{
for( j = 1; j < i; j++ ) {
HiH[j] = vh ^ ctx->HH[j];
HiL[j] = vl ^ ctx->HL[j];
}
}
return( 0 );
}
/**
* \brief This function associates a GCM context with a
* cipher algorithm and a key.
*
* \param ctx The GCM context. This must be initialized.
* \param cipher The 128-bit block cipher to use.
* \param key The encryption key. This must be a readable buffer of at
* least \p keybits bits.
* \param keybits The key size in bits. Valid options are:
* <ul><li>128 bits</li>
* <li>192 bits</li>
* <li>256 bits</li></ul>
*
* \return \c 0 on success.
* \return A cipher-specific error code on failure.
*/
int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
mbedtls_cipher_id_t cipher,
const unsigned char *key,
@ -135,33 +148,24 @@ int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
const mbedtls_cipher_info_t *cipher_info;
GCM_VALIDATE_RET( ctx != NULL );
GCM_VALIDATE_RET( key != NULL );
GCM_VALIDATE_RET( keybits == 128 || keybits == 192 || keybits == 256 );
cipher_info = mbedtls_cipher_info_from_values( cipher, keybits,
MBEDTLS_MODE_ECB );
if( cipher_info == NULL )
return( MBEDTLS_ERR_GCM_BAD_INPUT );
if( cipher_info->block_size != 16 )
return( MBEDTLS_ERR_GCM_BAD_INPUT );
mbedtls_cipher_free( &ctx->cipher_ctx );
if( ( ret = mbedtls_cipher_setup( &ctx->cipher_ctx, cipher_info ) ) != 0 )
return( ret );
if( ( ret = mbedtls_cipher_setkey( &ctx->cipher_ctx, key, keybits,
MBEDTLS_ENCRYPT ) ) != 0 )
{
MBEDTLS_ENCRYPT ) ) != 0 ) {
return( ret );
}
if( ( ret = gcm_gen_table( ctx ) ) != 0 )
return( ret );
return( 0 );
}
@ -182,48 +186,31 @@ static const uint64_t last4[16] =
* Sets output to x times H using the precomputed tables.
* x and output are seen as elements of GF(2^128) as in [MGV].
*/
static void gcm_mult( mbedtls_gcm_context *ctx, const unsigned char x[16],
unsigned char output[16] )
static void gcm_mult( mbedtls_gcm_context *ctx, unsigned char x[16] )
{
int i = 0;
unsigned char lo, hi, rem;
int i;
uint64_t zh, zl;
unsigned char lo, hi, rem;
#if defined(MBEDTLS_AESNI_C) && defined(MBEDTLS_HAVE_X86_64)
if (X86_HAVE(AES) && X86_HAVE(PCLMUL)) {
unsigned char h[16];
PUT_UINT32_BE( ctx->HH[8] >> 32, h, 0 );
PUT_UINT32_BE( ctx->HH[8], h, 4 );
PUT_UINT32_BE( ctx->HL[8] >> 32, h, 8 );
PUT_UINT32_BE( ctx->HL[8], h, 12 );
mbedtls_aesni_gcm_mult( output, x, h );
if (LIKELY(X86_HAVE(AES) && X86_HAVE(PCLMUL))) {
mbedtls_aesni_gcm_mult( x, ctx->H8 );
return;
}
#endif /* MBEDTLS_AESNI_C && MBEDTLS_HAVE_X86_64 */
lo = x[15] & 0xf;
zh = ctx->HH[lo];
zl = ctx->HL[lo];
for( i = 15; i >= 0; i-- )
{
for( i = 15; i >= 0; i-- ) {
lo = x[i] & 0xf;
hi = ( x[i] >> 4 ) & 0xf;
if( i != 15 )
{
if( i != 15 ) {
rem = (unsigned char) zl & 0xf;
zl = ( zh << 60 ) | ( zl >> 4 );
zh = ( zh >> 4 );
zh ^= (uint64_t) last4[rem] << 48;
zh ^= ctx->HH[lo];
zl ^= ctx->HL[lo];
}
rem = (unsigned char) zl & 0xf;
zl = ( zh << 60 ) | ( zl >> 4 );
zh = ( zh >> 4 );
@ -231,13 +218,27 @@ static void gcm_mult( mbedtls_gcm_context *ctx, const unsigned char x[16],
zh ^= ctx->HH[hi];
zl ^= ctx->HL[hi];
}
PUT_UINT32_BE( zh >> 32, output, 0 );
PUT_UINT32_BE( zh, output, 4 );
PUT_UINT32_BE( zl >> 32, output, 8 );
PUT_UINT32_BE( zl, output, 12 );
PUT_UINT64_BE( zh, x, 0 );
PUT_UINT64_BE( zl, x, 8 );
}
/**
* \brief This function starts a GCM encryption or decryption
* operation.
*
* \param ctx The GCM context. This must be initialized.
* \param mode The operation to perform: #MBEDTLS_GCM_ENCRYPT or
* #MBEDTLS_GCM_DECRYPT.
* \param iv The initialization vector. This must be a readable buffer of
* at least \p iv_len Bytes.
* \param iv_len The length of the IV.
* \param add The buffer holding the additional data, or \c NULL
* if \p add_len is \c 0.
* \param add_len The length of the additional data. If \c 0,
* \p add may be \c NULL.
*
* \return \c 0 on success.
*/
int mbedtls_gcm_starts( mbedtls_gcm_context *ctx,
int mode,
const unsigned char *iv,
@ -245,190 +246,277 @@ int mbedtls_gcm_starts( mbedtls_gcm_context *ctx,
const unsigned char *add,
size_t add_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char work_buf[16];
size_t i;
const unsigned char *p;
size_t use_len, olen = 0;
unsigned char work_buf[16];
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
GCM_VALIDATE_RET( ctx != NULL );
GCM_VALIDATE_RET( iv != NULL );
GCM_VALIDATE_RET( add_len == 0 || add != NULL );
/* IV and AD are limited to 2^64 bits, so 2^61 bytes */
/* IV is not allowed to be zero length */
if( iv_len == 0 ||
( (uint64_t) iv_len ) >> 61 != 0 ||
( (uint64_t) add_len ) >> 61 != 0 )
{
( (uint64_t) add_len ) >> 61 != 0 ) {
return( MBEDTLS_ERR_GCM_BAD_INPUT );
}
memset( ctx->y, 0x00, sizeof(ctx->y) );
memset( ctx->buf, 0x00, sizeof(ctx->buf) );
ctx->mode = mode;
ctx->len = 0;
ctx->add_len = 0;
if( iv_len == 12 )
{
if( iv_len == 12 ) {
memcpy( ctx->y, iv, iv_len );
ctx->y[15] = 1;
}
else
{
} else {
memset( work_buf, 0x00, 16 );
PUT_UINT32_BE( iv_len * 8, work_buf, 12 );
p = iv;
while( iv_len > 0 )
{
while( iv_len > 0 ) {
use_len = ( iv_len < 16 ) ? iv_len : 16;
for( i = 0; i < use_len; i++ )
ctx->y[i] ^= p[i];
gcm_mult( ctx, ctx->y, ctx->y );
gcm_mult( ctx, ctx->y );
iv_len -= use_len;
p += use_len;
}
for( i = 0; i < 16; i++ )
ctx->y[i] ^= work_buf[i];
gcm_mult( ctx, ctx->y, ctx->y );
gcm_mult( ctx, ctx->y );
}
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctx->y, 16,
ctx->base_ectr, &olen ) ) != 0 )
{
ctx->base_ectr, &olen ) ) != 0 ) {
return( ret );
}
ctx->add_len = add_len;
p = add;
while( add_len > 0 )
{
while( add_len > 0 ) {
use_len = ( add_len < 16 ) ? add_len : 16;
for( i = 0; i < use_len; i++ )
ctx->buf[i] ^= p[i];
gcm_mult( ctx, ctx->buf, ctx->buf );
gcm_mult( ctx, ctx->buf );
add_len -= use_len;
p += use_len;
}
return( 0 );
}
/**
* \brief This function feeds an input buffer into an ongoing GCM
* encryption or decryption operation.
*
* The function expects input to be a multiple of 16
* Bytes. Only the last call before calling
* mbedtls_gcm_finish() can be less than 16 Bytes.
*
* \note For decryption, the output buffer cannot be the same as
* input buffer. If the buffers overlap, the output buffer
* must trail at least 8 Bytes behind the input buffer.
*
* \param ctx The GCM context. This must be initialized.
* \param length The length of the input data. This must be a multiple of
* 16 except in the last call before mbedtls_gcm_finish().
* \param input The buffer holding the input data. If \p length is greater
* than zero, this must be a readable buffer of at least that
* size in Bytes.
* \param output The buffer for holding the output data. If \p length is
* greater than zero, this must be a writable buffer of at
* least that size in Bytes.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure.
*/
int mbedtls_gcm_update( mbedtls_gcm_context *ctx,
size_t length,
const unsigned char *input,
unsigned char *output )
{
size_t i, j;
uint64_t a, b;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char ectr[16];
size_t i;
const unsigned char *p;
unsigned char *out_p = output;
size_t use_len, olen = 0;
unsigned char *q, *out_p = output;
size_t olen = 0;
GCM_VALIDATE_RET( ctx != NULL );
GCM_VALIDATE_RET( length == 0 || input != NULL );
GCM_VALIDATE_RET( length == 0 || output != NULL );
if( output > input && (size_t) ( output - input ) < length )
return( MBEDTLS_ERR_GCM_BAD_INPUT );
/* Total length is restricted to 2^39 - 256 bits, ie 2^36 - 2^5 bytes
* Also check for possible overflow */
if( ctx->len + length < ctx->len ||
(uint64_t) ctx->len + length > 0xFFFFFFFE0ull )
{
(uint64_t) ctx->len + length > 0xFFFFFFFE0ull ) {
return( MBEDTLS_ERR_GCM_BAD_INPUT );
}
ctx->len += length;
p = input;
while( length > 0 )
{
use_len = ( length < 16 ) ? length : 16;
q = ctx->buf;
for( j = 0; j + 16 <= length; j += 16 ){
for( i = 16; i > 12; i-- )
if( ++ctx->y[i - 1] != 0 )
break;
if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctx->y, 16, ectr,
&olen ) ) != 0 )
{
if( !( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctx->y, 16,
ectr, &olen ) ) ) {
if( ctx->mode == MBEDTLS_GCM_DECRYPT ) {
__builtin_memcpy(&a, p+j, 8);
__builtin_memcpy(&b, q, 8);
b ^= a;
__builtin_memcpy(q, &b, 8);
__builtin_memcpy(&b, ectr, 8);
b ^= a;
__builtin_memcpy(out_p+j, &b, 8);
__builtin_memcpy(&a, p+j+8, 8);
__builtin_memcpy(&b, q+8, 8);
b ^= a;
__builtin_memcpy(q+8, &b, 8);
__builtin_memcpy(&b, ectr+8, 8);
b ^= a;
__builtin_memcpy(out_p+j+8, &b, 8);
/* for( i = 0; i < 16; i++ ) ctx->buf[i] ^= p[i]; */
/* for( i = 0; i < 16; i++ ) out_p[i] = ectr[i] ^ p[i]; */
} else {
__builtin_memcpy(&a, ectr, 8);
__builtin_memcpy(&b, p+j, 8);
b ^= a;
__builtin_memcpy(out_p+j, &b, 8);
__builtin_memcpy(&a, q, 8);
b ^= a;
__builtin_memcpy(q, &b, 8);
__builtin_memcpy(&a, ectr+8, 8);
__builtin_memcpy(&b, p+j+8, 8);
b ^= a;
__builtin_memcpy(out_p+j+8, &b, 8);
__builtin_memcpy(&a, q+8, 8);
b ^= a;
__builtin_memcpy(q+8, &b, 8);
/* for( i = 0; i < 16; i++ ) out_p[i] = ectr[i] ^ p[i]; */
/* for( i = 0; i < 16; i++ ) ctx->buf[i] ^= out_p[i]; */
}
gcm_mult( ctx, q );
} else {
return( ret );
}
}
length -= j;
out_p += j;
p += j;
if( length ) {
for( i = 16; i > 12; i-- )
if( ++ctx->y[i - 1] != 0 )
break;
if( !( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctx->y, 16, ectr,
&olen ) ) ) {
if( ctx->mode == MBEDTLS_GCM_DECRYPT ) {
for( i = 0; i < length; i++ ){
q[i] ^= p[i];
out_p[i] = ectr[i] ^ p[i];
}
} else {
for( i = 0; i < length; i++ ){
out_p[i] = ectr[i] ^ p[i];
q[i] ^= out_p[i];
}
}
gcm_mult( ctx, q );
} else {
return( ret );
}
for( i = 0; i < use_len; i++ )
{
if( ctx->mode == MBEDTLS_GCM_DECRYPT )
ctx->buf[i] ^= p[i];
out_p[i] = ectr[i] ^ p[i];
if( ctx->mode == MBEDTLS_GCM_ENCRYPT )
ctx->buf[i] ^= out_p[i];
}
gcm_mult( ctx, ctx->buf, ctx->buf );
length -= use_len;
p += use_len;
out_p += use_len;
}
return( 0 );
}
/**
* \brief This function finishes the GCM operation and generates
* the authentication tag.
*
* It wraps up the GCM stream, and generates the
* tag. The tag can have a maximum length of 16 Bytes.
*
* \param ctx The GCM context. This must be initialized.
* \param tag The buffer for holding the tag. This must be a writable
* buffer of at least \p tag_len Bytes.
* \param tag_len The length of the tag to generate. This must be at least
* four.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure.
*/
int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
unsigned char *tag,
size_t tag_len )
{
unsigned char work_buf[16];
size_t i;
uint64_t orig_len;
uint64_t orig_add_len;
GCM_VALIDATE_RET( ctx != NULL );
GCM_VALIDATE_RET( tag != NULL );
orig_len = ctx->len * 8;
orig_add_len = ctx->add_len * 8;
if( tag_len > 16 || tag_len < 4 )
return( MBEDTLS_ERR_GCM_BAD_INPUT );
memcpy( tag, ctx->base_ectr, tag_len );
if( orig_len || orig_add_len )
{
memset( work_buf, 0x00, 16 );
PUT_UINT32_BE( ( orig_add_len >> 32 ), work_buf, 0 );
PUT_UINT32_BE( ( orig_add_len ), work_buf, 4 );
PUT_UINT32_BE( ( orig_len >> 32 ), work_buf, 8 );
PUT_UINT32_BE( ( orig_len ), work_buf, 12 );
for( i = 0; i < 16; i++ )
ctx->buf[i] ^= work_buf[i];
gcm_mult( ctx, ctx->buf, ctx->buf );
for( i = 0; i < tag_len; i++ )
tag[i] ^= ctx->buf[i];
if( orig_len || orig_add_len ) {
Write64be( ctx->buf + 0, READ64BE( ctx->buf + 0 ) ^ orig_add_len );
Write64be( ctx->buf + 8, READ64BE( ctx->buf + 8 ) ^ orig_len );
gcm_mult( ctx, ctx->buf );
for( i = 0; i < tag_len; i++ ) tag[i] ^= ctx->buf[i];
}
return( 0 );
}
/**
* \brief This function performs GCM encryption or decryption of a buffer.
*
* \note For encryption, the output buffer can be the same as the
* input buffer. For decryption, the output buffer cannot be
* the same as input buffer. If the buffers overlap, the output
* buffer must trail at least 8 Bytes behind the input buffer.
*
* \warning When this function performs a decryption, it outputs the
* authentication tag and does not verify that the data is
* authentic. You should use this function to perform encryption
* only. For decryption, use mbedtls_gcm_auth_decrypt() instead.
*
* \param ctx The GCM context to use for encryption or decryption. This
* must be initialized.
* \param mode The operation to perform:
* - #MBEDTLS_GCM_ENCRYPT to perform authenticated encryption.
* The ciphertext is written to \p output and the
* authentication tag is written to \p tag.
* - #MBEDTLS_GCM_DECRYPT to perform decryption.
* The plaintext is written to \p output and the
* authentication tag is written to \p tag.
* Note that this mode is not recommended, because it does
* not verify the authenticity of the data. For this reason,
* you should use mbedtls_gcm_auth_decrypt() instead of
* calling this function in decryption mode.
* \param length The length of the input data, which is equal to the length
* of the output data.
* \param iv The initialization vector. This must be a readable buffer of
* at least \p iv_len Bytes.
* \param iv_len The length of the IV.
* \param add The buffer holding the additional data. This must be of at
* least that size in Bytes.
* \param add_len The length of the additional data.
* \param input The buffer holding the input data. If \p length is greater
* than zero, this must be a readable buffer of at least that
* size in Bytes.
* \param output The buffer for holding the output data. If \p length is greater
* than zero, this must be a writable buffer of at least that
* size in Bytes.
* \param tag_len The length of the tag to generate.
* \param tag The buffer for holding the tag. This must be a writable
* buffer of at least \p tag_len Bytes.
*
* \return \c 0 if the encryption or decryption was performed
* successfully. Note that in #MBEDTLS_GCM_DECRYPT mode,
* this does not indicate that the data is authentic.
* \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
* not valid or a cipher-specific error code if the encryption
* or decryption failed.
*/
int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
int mode,
size_t length,
@ -442,26 +530,54 @@ int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
unsigned char *tag )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
GCM_VALIDATE_RET( ctx != NULL );
GCM_VALIDATE_RET( iv != NULL );
GCM_VALIDATE_RET( add_len == 0 || add != NULL );
GCM_VALIDATE_RET( length == 0 || input != NULL );
GCM_VALIDATE_RET( length == 0 || output != NULL );
GCM_VALIDATE_RET( tag != NULL );
if( ( ret = mbedtls_gcm_starts( ctx, mode, iv, iv_len, add, add_len ) ) != 0 )
return( ret );
if( ( ret = mbedtls_gcm_update( ctx, length, input, output ) ) != 0 )
return( ret );
if( ( ret = mbedtls_gcm_finish( ctx, tag, tag_len ) ) != 0 )
return( ret );
return( 0 );
}
/**
* \brief This function performs a GCM authenticated decryption of a
* buffer.
*
* \note For decryption, the output buffer cannot be the same as
* input buffer. If the buffers overlap, the output buffer
* must trail at least 8 Bytes behind the input buffer.
*
* \param ctx The GCM context. This must be initialized.
* \param length The length of the ciphertext to decrypt, which is also
* the length of the decrypted plaintext.
* \param iv The initialization vector. This must be a readable buffer
* of at least \p iv_len Bytes.
* \param iv_len The length of the IV.
* \param add The buffer holding the additional data. This must be of at
* least that size in Bytes.
* \param add_len The length of the additional data.
* \param tag The buffer holding the tag to verify. This must be a
* readable buffer of at least \p tag_len Bytes.
* \param tag_len The length of the tag to verify.
* \param input The buffer holding the ciphertext. If \p length is greater
* than zero, this must be a readable buffer of at least that
* size.
* \param output The buffer for holding the decrypted plaintext. If \p length
* is greater than zero, this must be a writable buffer of at
* least that size.
*
* \return \c 0 if successful and authenticated.
* \return #MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match.
* \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
* not valid or a cipher-specific error code if the decryption
* failed.
*/
int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
size_t length,
const unsigned char *iv,
@ -477,34 +593,34 @@ int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
unsigned char check_tag[16];
size_t i;
int diff;
GCM_VALIDATE_RET( ctx != NULL );
GCM_VALIDATE_RET( iv != NULL );
GCM_VALIDATE_RET( add_len == 0 || add != NULL );
GCM_VALIDATE_RET( tag != NULL );
GCM_VALIDATE_RET( length == 0 || input != NULL );
GCM_VALIDATE_RET( length == 0 || output != NULL );
if( ( ret = mbedtls_gcm_crypt_and_tag( ctx, MBEDTLS_GCM_DECRYPT, length,
iv, iv_len, add, add_len,
input, output, tag_len, check_tag ) ) != 0 )
{
input, output, tag_len, check_tag ) ) != 0 ) {
return( ret );
}
/* Check tag in "constant-time" */
for( diff = 0, i = 0; i < tag_len; i++ )
diff |= tag[i] ^ check_tag[i];
if( diff != 0 )
{
if( diff != 0 ) {
mbedtls_platform_zeroize( output, length );
return( MBEDTLS_ERR_GCM_AUTH_FAILED );
}
return( 0 );
}
/**
* \brief This function clears a GCM context and the underlying
* cipher sub-context.
*
* \param ctx The GCM context to clear. If this is \c NULL, the call has
* no effect. Otherwise, this must be initialized.
*/
void mbedtls_gcm_free( mbedtls_gcm_context *ctx )
{
if( ctx == NULL )
@ -743,6 +859,12 @@ static const unsigned char tag_test_data[MAX_TESTS * 3][16] =
0xc8, 0xb5, 0xd4, 0xcf, 0x5a, 0xe9, 0xf1, 0x9a },
};
/**
* \brief The GCM checkup routine.
*
* \return \c 0 on success.
* \return \c 1 on failure.
*/
int mbedtls_gcm_self_test( int verbose )
{
mbedtls_gcm_context ctx;