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rsa.c
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/*
* The RSA public-key cryptosystem
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* The following sources were referenced in the design of this implementation
* of the RSA algorithm:
*
* [1] A method for obtaining digital signatures and public-key cryptosystems
* R Rivest, A Shamir, and L Adleman
* http://people.csail.mit.edu/rivest/pubs.html#RSA78
*
* [2] Handbook of Applied Cryptography - 1997, Chapter 8
* Menezes, van Oorschot and Vanstone
*
* [3] Malware Guard Extension: Using SGX to Conceal Cache Attacks
* Michael Schwarz, Samuel Weiser, Daniel Gruss, Clémentine Maurice and
* Stefan Mangard
* https://arxiv.org/abs/1702.08719v2
*
*/
#include "common.h"
#if defined(MBEDTLS_RSA_C)
#include "mbedtls/rsa.h"
#include "mbedtls/rsa_internal.h"
#include "mbedtls/oid.h"
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"
#include "constant_time_internal.h"
#include "mbedtls/constant_time.h"
#include <string.h>
#if defined(MBEDTLS_PKCS1_V21)
#include "mbedtls/md.h"
#endif
#if defined(MBEDTLS_PKCS1_V15) && !defined(__OpenBSD__) && !defined(__NetBSD__)
#include <stdlib.h>
#endif
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#define mbedtls_printf printf
#define mbedtls_calloc calloc
#define mbedtls_free free
#endif
#if !defined(MBEDTLS_RSA_ALT)
/* Parameter validation macros */
#define RSA_VALIDATE_RET( cond ) \
MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_RSA_BAD_INPUT_DATA )
#define RSA_VALIDATE( cond ) \
MBEDTLS_INTERNAL_VALIDATE( cond )
int mbedtls_rsa_import( mbedtls_rsa_context *ctx,
const mbedtls_mpi *N,
const mbedtls_mpi *P, const mbedtls_mpi *Q,
const mbedtls_mpi *D, const mbedtls_mpi *E )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
RSA_VALIDATE_RET( ctx != NULL );
if( ( N != NULL && ( ret = mbedtls_mpi_copy( &ctx->N, N ) ) != 0 ) ||
( P != NULL && ( ret = mbedtls_mpi_copy( &ctx->P, P ) ) != 0 ) ||
( Q != NULL && ( ret = mbedtls_mpi_copy( &ctx->Q, Q ) ) != 0 ) ||
( D != NULL && ( ret = mbedtls_mpi_copy( &ctx->D, D ) ) != 0 ) ||
( E != NULL && ( ret = mbedtls_mpi_copy( &ctx->E, E ) ) != 0 ) )
{
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) );
}
if( N != NULL )
ctx->len = mbedtls_mpi_size( &ctx->N );
return( 0 );
}
int mbedtls_rsa_import_raw( mbedtls_rsa_context *ctx,
unsigned char const *N, size_t N_len,
unsigned char const *P, size_t P_len,
unsigned char const *Q, size_t Q_len,
unsigned char const *D, size_t D_len,
unsigned char const *E, size_t E_len )
{
int ret = 0;
RSA_VALIDATE_RET( ctx != NULL );
if( N != NULL )
{
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->N, N, N_len ) );
ctx->len = mbedtls_mpi_size( &ctx->N );
}
if( P != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->P, P, P_len ) );
if( Q != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->Q, Q, Q_len ) );
if( D != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->D, D, D_len ) );
if( E != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &ctx->E, E, E_len ) );
cleanup:
if( ret != 0 )
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) );
return( 0 );
}
/*
* Checks whether the context fields are set in such a way
* that the RSA primitives will be able to execute without error.
* It does *not* make guarantees for consistency of the parameters.
*/
static int rsa_check_context( mbedtls_rsa_context const *ctx, int is_priv,
int blinding_needed )
{
#if !defined(MBEDTLS_RSA_NO_CRT)
/* blinding_needed is only used for NO_CRT to decide whether
* P,Q need to be present or not. */
((void) blinding_needed);
#endif
if( ctx->len != mbedtls_mpi_size( &ctx->N ) ||
ctx->len > MBEDTLS_MPI_MAX_SIZE )
{
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
/*
* 1. Modular exponentiation needs positive, odd moduli.
*/
/* Modular exponentiation wrt. N is always used for
* RSA public key operations. */
if( mbedtls_mpi_cmp_int( &ctx->N, 0 ) <= 0 ||
mbedtls_mpi_get_bit( &ctx->N, 0 ) == 0 )
{
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
#if !defined(MBEDTLS_RSA_NO_CRT)
/* Modular exponentiation for P and Q is only
* used for private key operations and if CRT
* is used. */
if( is_priv &&
( mbedtls_mpi_cmp_int( &ctx->P, 0 ) <= 0 ||
mbedtls_mpi_get_bit( &ctx->P, 0 ) == 0 ||
mbedtls_mpi_cmp_int( &ctx->Q, 0 ) <= 0 ||
mbedtls_mpi_get_bit( &ctx->Q, 0 ) == 0 ) )
{
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
#endif /* !MBEDTLS_RSA_NO_CRT */
/*
* 2. Exponents must be positive
*/
/* Always need E for public key operations */
if( mbedtls_mpi_cmp_int( &ctx->E, 0 ) <= 0 )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
#if defined(MBEDTLS_RSA_NO_CRT)
/* For private key operations, use D or DP & DQ
* as (unblinded) exponents. */
if( is_priv && mbedtls_mpi_cmp_int( &ctx->D, 0 ) <= 0 )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
#else
if( is_priv &&
( mbedtls_mpi_cmp_int( &ctx->DP, 0 ) <= 0 ||
mbedtls_mpi_cmp_int( &ctx->DQ, 0 ) <= 0 ) )
{
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
#endif /* MBEDTLS_RSA_NO_CRT */
/* Blinding shouldn't make exponents negative either,
* so check that P, Q >= 1 if that hasn't yet been
* done as part of 1. */
#if defined(MBEDTLS_RSA_NO_CRT)
if( is_priv && blinding_needed &&
( mbedtls_mpi_cmp_int( &ctx->P, 0 ) <= 0 ||
mbedtls_mpi_cmp_int( &ctx->Q, 0 ) <= 0 ) )
{
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
#endif
/* It wouldn't lead to an error if it wasn't satisfied,
* but check for QP >= 1 nonetheless. */
#if !defined(MBEDTLS_RSA_NO_CRT)
if( is_priv &&
mbedtls_mpi_cmp_int( &ctx->QP, 0 ) <= 0 )
{
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
#endif
return( 0 );
}
int mbedtls_rsa_complete( mbedtls_rsa_context *ctx )
{
int ret = 0;
int have_N, have_P, have_Q, have_D, have_E;
#if !defined(MBEDTLS_RSA_NO_CRT)
int have_DP, have_DQ, have_QP;
#endif
int n_missing, pq_missing, d_missing, is_pub, is_priv;
RSA_VALIDATE_RET( ctx != NULL );
have_N = ( mbedtls_mpi_cmp_int( &ctx->N, 0 ) != 0 );
have_P = ( mbedtls_mpi_cmp_int( &ctx->P, 0 ) != 0 );
have_Q = ( mbedtls_mpi_cmp_int( &ctx->Q, 0 ) != 0 );
have_D = ( mbedtls_mpi_cmp_int( &ctx->D, 0 ) != 0 );
have_E = ( mbedtls_mpi_cmp_int( &ctx->E, 0 ) != 0 );
#if !defined(MBEDTLS_RSA_NO_CRT)
have_DP = ( mbedtls_mpi_cmp_int( &ctx->DP, 0 ) != 0 );
have_DQ = ( mbedtls_mpi_cmp_int( &ctx->DQ, 0 ) != 0 );
have_QP = ( mbedtls_mpi_cmp_int( &ctx->QP, 0 ) != 0 );
#endif
/*
* Check whether provided parameters are enough
* to deduce all others. The following incomplete
* parameter sets for private keys are supported:
*
* (1) P, Q missing.
* (2) D and potentially N missing.
*
*/
n_missing = have_P && have_Q && have_D && have_E;
pq_missing = have_N && !have_P && !have_Q && have_D && have_E;
d_missing = have_P && have_Q && !have_D && have_E;
is_pub = have_N && !have_P && !have_Q && !have_D && have_E;
/* These three alternatives are mutually exclusive */
is_priv = n_missing || pq_missing || d_missing;
if( !is_priv && !is_pub )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
/*
* Step 1: Deduce N if P, Q are provided.
*/
if( !have_N && have_P && have_Q )
{
if( ( ret = mbedtls_mpi_mul_mpi( &ctx->N, &ctx->P,
&ctx->Q ) ) != 0 )
{
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) );
}
ctx->len = mbedtls_mpi_size( &ctx->N );
}
/*
* Step 2: Deduce and verify all remaining core parameters.
*/
if( pq_missing )
{
ret = mbedtls_rsa_deduce_primes( &ctx->N, &ctx->E, &ctx->D,
&ctx->P, &ctx->Q );
if( ret != 0 )
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) );
}
else if( d_missing )
{
if( ( ret = mbedtls_rsa_deduce_private_exponent( &ctx->P,
&ctx->Q,
&ctx->E,
&ctx->D ) ) != 0 )
{
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) );
}
}
/*
* Step 3: Deduce all additional parameters specific
* to our current RSA implementation.
*/
#if !defined(MBEDTLS_RSA_NO_CRT)
if( is_priv && ! ( have_DP && have_DQ && have_QP ) )
{
ret = mbedtls_rsa_deduce_crt( &ctx->P, &ctx->Q, &ctx->D,
&ctx->DP, &ctx->DQ, &ctx->QP );
if( ret != 0 )
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) );
}
#endif /* MBEDTLS_RSA_NO_CRT */
/*
* Step 3: Basic sanity checks
*/
return( rsa_check_context( ctx, is_priv, 1 ) );
}
int mbedtls_rsa_export_raw( const mbedtls_rsa_context *ctx,
unsigned char *N, size_t N_len,
unsigned char *P, size_t P_len,
unsigned char *Q, size_t Q_len,
unsigned char *D, size_t D_len,
unsigned char *E, size_t E_len )
{
int ret = 0;
int is_priv;
RSA_VALIDATE_RET( ctx != NULL );
/* Check if key is private or public */
is_priv =
mbedtls_mpi_cmp_int( &ctx->N, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->P, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->Q, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->D, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->E, 0 ) != 0;
if( !is_priv )
{
/* If we're trying to export private parameters for a public key,
* something must be wrong. */
if( P != NULL || Q != NULL || D != NULL )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
if( N != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->N, N, N_len ) );
if( P != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->P, P, P_len ) );
if( Q != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->Q, Q, Q_len ) );
if( D != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->D, D, D_len ) );
if( E != NULL )
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->E, E, E_len ) );
cleanup:
return( ret );
}
int mbedtls_rsa_export( const mbedtls_rsa_context *ctx,
mbedtls_mpi *N, mbedtls_mpi *P, mbedtls_mpi *Q,
mbedtls_mpi *D, mbedtls_mpi *E )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
int is_priv;
RSA_VALIDATE_RET( ctx != NULL );
/* Check if key is private or public */
is_priv =
mbedtls_mpi_cmp_int( &ctx->N, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->P, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->Q, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->D, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->E, 0 ) != 0;
if( !is_priv )
{
/* If we're trying to export private parameters for a public key,
* something must be wrong. */
if( P != NULL || Q != NULL || D != NULL )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
/* Export all requested core parameters. */
if( ( N != NULL && ( ret = mbedtls_mpi_copy( N, &ctx->N ) ) != 0 ) ||
( P != NULL && ( ret = mbedtls_mpi_copy( P, &ctx->P ) ) != 0 ) ||
( Q != NULL && ( ret = mbedtls_mpi_copy( Q, &ctx->Q ) ) != 0 ) ||
( D != NULL && ( ret = mbedtls_mpi_copy( D, &ctx->D ) ) != 0 ) ||
( E != NULL && ( ret = mbedtls_mpi_copy( E, &ctx->E ) ) != 0 ) )
{
return( ret );
}
return( 0 );
}
/*
* Export CRT parameters
* This must also be implemented if CRT is not used, for being able to
* write DER encoded RSA keys. The helper function mbedtls_rsa_deduce_crt
* can be used in this case.
*/
int mbedtls_rsa_export_crt( const mbedtls_rsa_context *ctx,
mbedtls_mpi *DP, mbedtls_mpi *DQ, mbedtls_mpi *QP )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
int is_priv;
RSA_VALIDATE_RET( ctx != NULL );
/* Check if key is private or public */
is_priv =
mbedtls_mpi_cmp_int( &ctx->N, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->P, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->Q, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->D, 0 ) != 0 &&
mbedtls_mpi_cmp_int( &ctx->E, 0 ) != 0;
if( !is_priv )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
#if !defined(MBEDTLS_RSA_NO_CRT)
/* Export all requested blinding parameters. */
if( ( DP != NULL && ( ret = mbedtls_mpi_copy( DP, &ctx->DP ) ) != 0 ) ||
( DQ != NULL && ( ret = mbedtls_mpi_copy( DQ, &ctx->DQ ) ) != 0 ) ||
( QP != NULL && ( ret = mbedtls_mpi_copy( QP, &ctx->QP ) ) != 0 ) )
{
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) );
}
#else
if( ( ret = mbedtls_rsa_deduce_crt( &ctx->P, &ctx->Q, &ctx->D,
DP, DQ, QP ) ) != 0 )
{
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_BAD_INPUT_DATA, ret ) );
}
#endif
return( 0 );
}
/*
* Initialize an RSA context
*/
void mbedtls_rsa_init( mbedtls_rsa_context *ctx,
int padding,
int hash_id )
{
RSA_VALIDATE( ctx != NULL );
RSA_VALIDATE( padding == MBEDTLS_RSA_PKCS_V15 ||
padding == MBEDTLS_RSA_PKCS_V21 );
memset( ctx, 0, sizeof( mbedtls_rsa_context ) );
mbedtls_rsa_set_padding( ctx, padding, hash_id );
#if defined(MBEDTLS_THREADING_C)
/* Set ctx->ver to nonzero to indicate that the mutex has been
* initialized and will need to be freed. */
ctx->ver = 1;
mbedtls_mutex_init( &ctx->mutex );
#endif
}
/*
* Set padding for an existing RSA context
*/
void mbedtls_rsa_set_padding( mbedtls_rsa_context *ctx, int padding,
int hash_id )
{
RSA_VALIDATE( ctx != NULL );
RSA_VALIDATE( padding == MBEDTLS_RSA_PKCS_V15 ||
padding == MBEDTLS_RSA_PKCS_V21 );
ctx->padding = padding;
ctx->hash_id = hash_id;
}
/*
* Get length in bytes of RSA modulus
*/
size_t mbedtls_rsa_get_len( const mbedtls_rsa_context *ctx )
{
return( ctx->len );
}
#if defined(MBEDTLS_GENPRIME)
/*
* Generate an RSA keypair
*
* This generation method follows the RSA key pair generation procedure of
* FIPS 186-4 if 2^16 < exponent < 2^256 and nbits = 2048 or nbits = 3072.
*/
int mbedtls_rsa_gen_key( mbedtls_rsa_context *ctx,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng,
unsigned int nbits, int exponent )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_mpi H, G, L;
int prime_quality = 0;
RSA_VALIDATE_RET( ctx != NULL );
RSA_VALIDATE_RET( f_rng != NULL );
/*
* If the modulus is 1024 bit long or shorter, then the security strength of
* the RSA algorithm is less than or equal to 80 bits and therefore an error
* rate of 2^-80 is sufficient.
*/
if( nbits > 1024 )
prime_quality = MBEDTLS_MPI_GEN_PRIME_FLAG_LOW_ERR;
mbedtls_mpi_init( &H );
mbedtls_mpi_init( &G );
mbedtls_mpi_init( &L );
if( nbits < 128 || exponent < 3 || nbits % 2 != 0 )
{
ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
goto cleanup;
}
/*
* find primes P and Q with Q < P so that:
* 1. |P-Q| > 2^( nbits / 2 - 100 )
* 2. GCD( E, (P-1)*(Q-1) ) == 1
* 3. E^-1 mod LCM(P-1, Q-1) > 2^( nbits / 2 )
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &ctx->E, exponent ) );
do
{
MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->P, nbits >> 1,
prime_quality, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->Q, nbits >> 1,
prime_quality, f_rng, p_rng ) );
/* make sure the difference between p and q is not too small (FIPS 186-4 §B.3.3 step 5.4) */
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &H, &ctx->P, &ctx->Q ) );
if( mbedtls_mpi_bitlen( &H ) <= ( ( nbits >= 200 ) ? ( ( nbits >> 1 ) - 99 ) : 0 ) )
continue;
/* not required by any standards, but some users rely on the fact that P > Q */
if( H.s < 0 )
mbedtls_mpi_swap( &ctx->P, &ctx->Q );
/* Temporarily replace P,Q by P-1, Q-1 */
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &ctx->P, &ctx->P, 1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &ctx->Q, &ctx->Q, 1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &H, &ctx->P, &ctx->Q ) );
/* check GCD( E, (P-1)*(Q-1) ) == 1 (FIPS 186-4 §B.3.1 criterion 2(a)) */
MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( &G, &ctx->E, &H ) );
if( mbedtls_mpi_cmp_int( &G, 1 ) != 0 )
continue;
/* compute smallest possible D = E^-1 mod LCM(P-1, Q-1) (FIPS 186-4 §B.3.1 criterion 3(b)) */
MBEDTLS_MPI_CHK( mbedtls_mpi_gcd( &G, &ctx->P, &ctx->Q ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_div_mpi( &L, NULL, &H, &G ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &ctx->D, &ctx->E, &L ) );
if( mbedtls_mpi_bitlen( &ctx->D ) <= ( ( nbits + 1 ) / 2 ) ) // (FIPS 186-4 §B.3.1 criterion 3(a))
continue;
break;
}
while( 1 );
/* Restore P,Q */
MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( &ctx->P, &ctx->P, 1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( &ctx->Q, &ctx->Q, 1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->N, &ctx->P, &ctx->Q ) );
ctx->len = mbedtls_mpi_size( &ctx->N );
#if !defined(MBEDTLS_RSA_NO_CRT)
/*
* DP = D mod (P - 1)
* DQ = D mod (Q - 1)
* QP = Q^-1 mod P
*/
MBEDTLS_MPI_CHK( mbedtls_rsa_deduce_crt( &ctx->P, &ctx->Q, &ctx->D,
&ctx->DP, &ctx->DQ, &ctx->QP ) );
#endif /* MBEDTLS_RSA_NO_CRT */
/* Double-check */
MBEDTLS_MPI_CHK( mbedtls_rsa_check_privkey( ctx ) );
cleanup:
mbedtls_mpi_free( &H );
mbedtls_mpi_free( &G );
mbedtls_mpi_free( &L );
if( ret != 0 )
{
mbedtls_rsa_free( ctx );
if( ( -ret & ~0x7f ) == 0 )
ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_KEY_GEN_FAILED, ret );
return( ret );
}
return( 0 );
}
#endif /* MBEDTLS_GENPRIME */
/*
* Check a public RSA key
*/
int mbedtls_rsa_check_pubkey( const mbedtls_rsa_context *ctx )
{
RSA_VALIDATE_RET( ctx != NULL );
if( rsa_check_context( ctx, 0 /* public */, 0 /* no blinding */ ) != 0 )
return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED );
if( mbedtls_mpi_bitlen( &ctx->N ) < 128 )
{
return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED );
}
if( mbedtls_mpi_get_bit( &ctx->E, 0 ) == 0 ||
mbedtls_mpi_bitlen( &ctx->E ) < 2 ||
mbedtls_mpi_cmp_mpi( &ctx->E, &ctx->N ) >= 0 )
{
return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED );
}
return( 0 );
}
/*
* Check for the consistency of all fields in an RSA private key context
*/
int mbedtls_rsa_check_privkey( const mbedtls_rsa_context *ctx )
{
RSA_VALIDATE_RET( ctx != NULL );
if( mbedtls_rsa_check_pubkey( ctx ) != 0 ||
rsa_check_context( ctx, 1 /* private */, 1 /* blinding */ ) != 0 )
{
return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED );
}
if( mbedtls_rsa_validate_params( &ctx->N, &ctx->P, &ctx->Q,
&ctx->D, &ctx->E, NULL, NULL ) != 0 )
{
return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED );
}
#if !defined(MBEDTLS_RSA_NO_CRT)
else if( mbedtls_rsa_validate_crt( &ctx->P, &ctx->Q, &ctx->D,
&ctx->DP, &ctx->DQ, &ctx->QP ) != 0 )
{
return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED );
}
#endif
return( 0 );
}
/*
* Check if contexts holding a public and private key match
*/
int mbedtls_rsa_check_pub_priv( const mbedtls_rsa_context *pub,
const mbedtls_rsa_context *prv )
{
RSA_VALIDATE_RET( pub != NULL );
RSA_VALIDATE_RET( prv != NULL );
if( mbedtls_rsa_check_pubkey( pub ) != 0 ||
mbedtls_rsa_check_privkey( prv ) != 0 )
{
return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED );
}
if( mbedtls_mpi_cmp_mpi( &pub->N, &prv->N ) != 0 ||
mbedtls_mpi_cmp_mpi( &pub->E, &prv->E ) != 0 )
{
return( MBEDTLS_ERR_RSA_KEY_CHECK_FAILED );
}
return( 0 );
}
/*
* Do an RSA public key operation
*/
int mbedtls_rsa_public( mbedtls_rsa_context *ctx,
const unsigned char *input,
unsigned char *output )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t olen;
mbedtls_mpi T;
RSA_VALIDATE_RET( ctx != NULL );
RSA_VALIDATE_RET( input != NULL );
RSA_VALIDATE_RET( output != NULL );
if( rsa_check_context( ctx, 0 /* public */, 0 /* no blinding */ ) )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
mbedtls_mpi_init( &T );
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &T, input, ctx->len ) );
if( mbedtls_mpi_cmp_mpi( &T, &ctx->N ) >= 0 )
{
ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
goto cleanup;
}
olen = ctx->len;
MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &T, &T, &ctx->E, &ctx->N, &ctx->RN ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &T, output, olen ) );
cleanup:
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
mbedtls_mpi_free( &T );
if( ret != 0 )
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_RSA_PUBLIC_FAILED, ret ) );
return( 0 );
}
/*
* Generate or update blinding values, see section 10 of:
* KOCHER, Paul C. Timing attacks on implementations of Diffie-Hellman, RSA,
* DSS, and other systems. In : Advances in Cryptology-CRYPTO'96. Springer
* Berlin Heidelberg, 1996. p. 104-113.
*/
static int rsa_prepare_blinding( mbedtls_rsa_context *ctx,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
{
int ret, count = 0;
mbedtls_mpi R;
mbedtls_mpi_init( &R );
if( ctx->Vf.p != NULL )
{
/* We already have blinding values, just update them by squaring */
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vf, &ctx->Vf, &ctx->N ) );
goto cleanup;
}
/* Unblinding value: Vf = random number, invertible mod N */
do {
if( count++ > 10 )
{
ret = MBEDTLS_ERR_RSA_RNG_FAILED;
goto cleanup;
}
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &ctx->Vf, ctx->len - 1, f_rng, p_rng ) );
/* Compute Vf^-1 as R * (R Vf)^-1 to avoid leaks from inv_mod. */
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &R, ctx->len - 1, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vf, &R ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) );
/* At this point, Vi is invertible mod N if and only if both Vf and R
* are invertible mod N. If one of them isn't, we don't need to know
* which one, we just loop and choose new values for both of them.
* (Each iteration succeeds with overwhelming probability.) */
ret = mbedtls_mpi_inv_mod( &ctx->Vi, &ctx->Vi, &ctx->N );
if( ret != 0 && ret != MBEDTLS_ERR_MPI_NOT_ACCEPTABLE )
goto cleanup;
} while( ret == MBEDTLS_ERR_MPI_NOT_ACCEPTABLE );
/* Finish the computation of Vf^-1 = R * (R Vf)^-1 */
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &R ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) );
/* Blinding value: Vi = Vf^(-e) mod N
* (Vi already contains Vf^-1 at this point) */
MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->Vi, &ctx->Vi, &ctx->E, &ctx->N, &ctx->RN ) );
cleanup:
mbedtls_mpi_free( &R );
return( ret );
}
/*
* Exponent blinding supposed to prevent side-channel attacks using multiple
* traces of measurements to recover the RSA key. The more collisions are there,
* the more bits of the key can be recovered. See [3].
*
* Collecting n collisions with m bit long blinding value requires 2^(m-m/n)
* observations on avarage.
*
* For example with 28 byte blinding to achieve 2 collisions the adversary has
* to make 2^112 observations on avarage.
*
* (With the currently (as of 2017 April) known best algorithms breaking 2048
* bit RSA requires approximately as much time as trying out 2^112 random keys.
* Thus in this sense with 28 byte blinding the security is not reduced by
* side-channel attacks like the one in [3])
*
* This countermeasure does not help if the key recovery is possible with a
* single trace.
*/
#define RSA_EXPONENT_BLINDING 28
/*
* Do an RSA private key operation
*/
int mbedtls_rsa_private( mbedtls_rsa_context *ctx,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng,
const unsigned char *input,
unsigned char *output )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t olen;
/* Temporary holding the result */
mbedtls_mpi T;
/* Temporaries holding P-1, Q-1 and the
* exponent blinding factor, respectively. */
mbedtls_mpi P1, Q1, R;
#if !defined(MBEDTLS_RSA_NO_CRT)
/* Temporaries holding the results mod p resp. mod q. */
mbedtls_mpi TP, TQ;
/* Temporaries holding the blinded exponents for
* the mod p resp. mod q computation (if used). */
mbedtls_mpi DP_blind, DQ_blind;
/* Pointers to actual exponents to be used - either the unblinded
* or the blinded ones, depending on the presence of a PRNG. */
mbedtls_mpi *DP = &ctx->DP;
mbedtls_mpi *DQ = &ctx->DQ;
#else
/* Temporary holding the blinded exponent (if used). */
mbedtls_mpi D_blind;
/* Pointer to actual exponent to be used - either the unblinded
* or the blinded one, depending on the presence of a PRNG. */
mbedtls_mpi *D = &ctx->D;
#endif /* MBEDTLS_RSA_NO_CRT */
/* Temporaries holding the initial input and the double
* checked result; should be the same in the end. */
mbedtls_mpi I, C;
RSA_VALIDATE_RET( ctx != NULL );
RSA_VALIDATE_RET( input != NULL );
RSA_VALIDATE_RET( output != NULL );
if( rsa_check_context( ctx, 1 /* private key checks */,
f_rng != NULL /* blinding y/n */ ) != 0 )
{
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
}
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
/* MPI Initialization */
mbedtls_mpi_init( &T );
mbedtls_mpi_init( &P1 );
mbedtls_mpi_init( &Q1 );
mbedtls_mpi_init( &R );
if( f_rng != NULL )
{
#if defined(MBEDTLS_RSA_NO_CRT)
mbedtls_mpi_init( &D_blind );
#else
mbedtls_mpi_init( &DP_blind );
mbedtls_mpi_init( &DQ_blind );
#endif
}
#if !defined(MBEDTLS_RSA_NO_CRT)
mbedtls_mpi_init( &TP ); mbedtls_mpi_init( &TQ );
#endif
mbedtls_mpi_init( &I );
mbedtls_mpi_init( &C );
/* End of MPI initialization */
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &T, input, ctx->len ) );
if( mbedtls_mpi_cmp_mpi( &T, &ctx->N ) >= 0 )
{
ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
goto cleanup;
}
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &I, &T ) );
if( f_rng != NULL )
{
/*
* Blinding
* T = T * Vi mod N
*/
MBEDTLS_MPI_CHK( rsa_prepare_blinding( ctx, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T, &T, &ctx->Vi ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &T, &ctx->N ) );
/*
* Exponent blinding
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &P1, &ctx->P, 1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &Q1, &ctx->Q, 1 ) );
#if defined(MBEDTLS_RSA_NO_CRT)
/*
* D_blind = ( P - 1 ) * ( Q - 1 ) * R + D
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &R, RSA_EXPONENT_BLINDING,
f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &D_blind, &P1, &Q1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &D_blind, &D_blind, &R ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &D_blind, &D_blind, &ctx->D ) );
D = &D_blind;
#else
/*
* DP_blind = ( P - 1 ) * R + DP
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &R, RSA_EXPONENT_BLINDING,
f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &DP_blind, &P1, &R ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &DP_blind, &DP_blind,
&ctx->DP ) );
DP = &DP_blind;
/*
* DQ_blind = ( Q - 1 ) * R + DQ
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &R, RSA_EXPONENT_BLINDING,
f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &DQ_blind, &Q1, &R ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &DQ_blind, &DQ_blind,
&ctx->DQ ) );
DQ = &DQ_blind;
#endif /* MBEDTLS_RSA_NO_CRT */
}
#if defined(MBEDTLS_RSA_NO_CRT)
MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &T, &T, D, &ctx->N, &ctx->RN ) );
#else
/*
* Faster decryption using the CRT