Diff: mbedtls/source/dhm.c

Revision:

11:cada08fc8a70

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbedtls/source/dhm.c	Thu Jun 09 17:08:36 2016 +0000
@@ -0,0 +1,624 @@
+/*
+ *  Diffie-Hellman-Merkle key exchange
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+/*
+ *  Reference:
+ *
+ *  http://www.cacr.math.uwaterloo.ca/hac/ (chapter 12)
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_DHM_C)
+
+#include "mbedtls/dhm.h"
+
+#include <string.h>
+
+#if defined(MBEDTLS_PEM_PARSE_C)
+#include "mbedtls/pem.h"
+#endif
+
+#if defined(MBEDTLS_ASN1_PARSE_C)
+#include "mbedtls/asn1.h"
+#endif
+
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdlib.h>
+#include <stdio.h>
+#define mbedtls_printf     printf
+#define mbedtls_calloc    calloc
+#define mbedtls_free       free
+#endif
+
+/* Implementation that should never be optimized out by the compiler */
+static void mbedtls_zeroize( void *v, size_t n ) {
+    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
+/*
+ * helper to validate the mbedtls_mpi size and import it
+ */
+static int dhm_read_bignum( mbedtls_mpi *X,
+                            unsigned char **p,
+                            const unsigned char *end )
+{
+    int ret, n;
+
+    if( end - *p < 2 )
+        return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
+
+    n = ( (*p)[0] << 8 ) | (*p)[1];
+    (*p) += 2;
+
+    if( (int)( end - *p ) < n )
+        return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_mpi_read_binary( X, *p, n ) ) != 0 )
+        return( MBEDTLS_ERR_DHM_READ_PARAMS_FAILED + ret );
+
+    (*p) += n;
+
+    return( 0 );
+}
+
+/*
+ * Verify sanity of parameter with regards to P
+ *
+ * Parameter should be: 2 <= public_param <= P - 2
+ *
+ * For more information on the attack, see:
+ *  http://www.cl.cam.ac.uk/~rja14/Papers/psandqs.pdf
+ *  http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2005-2643
+ */
+static int dhm_check_range( const mbedtls_mpi *param, const mbedtls_mpi *P )
+{
+    mbedtls_mpi L, U;
+    int ret = MBEDTLS_ERR_DHM_BAD_INPUT_DATA;
+
+    mbedtls_mpi_init( &L ); mbedtls_mpi_init( &U );
+
+    MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &L, 2 ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &U, P, 2 ) );
+
+    if( mbedtls_mpi_cmp_mpi( param, &L ) >= 0 &&
+        mbedtls_mpi_cmp_mpi( param, &U ) <= 0 )
+    {
+        ret = 0;
+    }
+
+cleanup:
+    mbedtls_mpi_free( &L ); mbedtls_mpi_free( &U );
+    return( ret );
+}
+
+void mbedtls_dhm_init( mbedtls_dhm_context *ctx )
+{
+    memset( ctx, 0, sizeof( mbedtls_dhm_context ) );
+}
+
+/*
+ * Parse the ServerKeyExchange parameters
+ */
+int mbedtls_dhm_read_params( mbedtls_dhm_context *ctx,
+                     unsigned char **p,
+                     const unsigned char *end )
+{
+    int ret;
+
+    if( ( ret = dhm_read_bignum( &ctx->P,  p, end ) ) != 0 ||
+        ( ret = dhm_read_bignum( &ctx->G,  p, end ) ) != 0 ||
+        ( ret = dhm_read_bignum( &ctx->GY, p, end ) ) != 0 )
+        return( ret );
+
+    if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
+        return( ret );
+
+    ctx->len = mbedtls_mpi_size( &ctx->P );
+
+    return( 0 );
+}
+
+/*
+ * Setup and write the ServerKeyExchange parameters
+ */
+int mbedtls_dhm_make_params( mbedtls_dhm_context *ctx, int x_size,
+                     unsigned char *output, size_t *olen,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng )
+{
+    int ret, count = 0;
+    size_t n1, n2, n3;
+    unsigned char *p;
+
+    if( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
+        return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
+
+    /*
+     * Generate X as large as possible ( < P )
+     */
+    do
+    {
+        mbedtls_mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
+
+        while( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
+            MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->X, 1 ) );
+
+        if( count++ > 10 )
+            return( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED );
+    }
+    while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
+
+    /*
+     * Calculate GX = G^X mod P
+     */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
+                          &ctx->P , &ctx->RP ) );
+
+    if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
+        return( ret );
+
+    /*
+     * export P, G, GX
+     */
+#define DHM_MPI_EXPORT(X,n)                     \
+    MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, p + 2, n ) ); \
+    *p++ = (unsigned char)( n >> 8 );           \
+    *p++ = (unsigned char)( n      ); p += n;
+
+    n1 = mbedtls_mpi_size( &ctx->P  );
+    n2 = mbedtls_mpi_size( &ctx->G  );
+    n3 = mbedtls_mpi_size( &ctx->GX );
+
+    p = output;
+    DHM_MPI_EXPORT( &ctx->P , n1 );
+    DHM_MPI_EXPORT( &ctx->G , n2 );
+    DHM_MPI_EXPORT( &ctx->GX, n3 );
+
+    *olen  = p - output;
+
+    ctx->len = n1;
+
+cleanup:
+
+    if( ret != 0 )
+        return( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED + ret );
+
+    return( 0 );
+}
+
+/*
+ * Import the peer's public value G^Y
+ */
+int mbedtls_dhm_read_public( mbedtls_dhm_context *ctx,
+                     const unsigned char *input, size_t ilen )
+{
+    int ret;
+
+    if( ctx == NULL || ilen < 1 || ilen > ctx->len )
+        return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_mpi_read_binary( &ctx->GY, input, ilen ) ) != 0 )
+        return( MBEDTLS_ERR_DHM_READ_PUBLIC_FAILED + ret );
+
+    return( 0 );
+}
+
+/*
+ * Create own private value X and export G^X
+ */
+int mbedtls_dhm_make_public( mbedtls_dhm_context *ctx, int x_size,
+                     unsigned char *output, size_t olen,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng )
+{
+    int ret, count = 0;
+
+    if( ctx == NULL || olen < 1 || olen > ctx->len )
+        return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
+
+    if( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
+        return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
+
+    /*
+     * generate X and calculate GX = G^X mod P
+     */
+    do
+    {
+        mbedtls_mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
+
+        while( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
+            MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->X, 1 ) );
+
+        if( count++ > 10 )
+            return( MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED );
+    }
+    while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
+
+    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
+                          &ctx->P , &ctx->RP ) );
+
+    if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
+        return( ret );
+
+    MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->GX, output, olen ) );
+
+cleanup:
+
+    if( ret != 0 )
+        return( MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED + ret );
+
+    return( 0 );
+}
+
+/*
+ * Use the blinding method and optimisation suggested in 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 dhm_update_blinding( mbedtls_dhm_context *ctx,
+                    int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
+{
+    int ret, count;
+
+    /*
+     * Don't use any blinding the first time a particular X is used,
+     * but remember it to use blinding next time.
+     */
+    if( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->pX ) != 0 )
+    {
+        MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &ctx->pX, &ctx->X ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &ctx->Vi, 1 ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &ctx->Vf, 1 ) );
+
+        return( 0 );
+    }
+
+    /*
+     * Ok, we need blinding. Can we re-use existing values?
+     * If yes, just update them by squaring them.
+     */
+    if( mbedtls_mpi_cmp_int( &ctx->Vi, 1 ) != 0 )
+    {
+        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->P ) );
+
+        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->P ) );
+
+        return( 0 );
+    }
+
+    /*
+     * We need to generate blinding values from scratch
+     */
+
+    /* Vi = random( 2, P-1 ) */
+    count = 0;
+    do
+    {
+        mbedtls_mpi_fill_random( &ctx->Vi, mbedtls_mpi_size( &ctx->P ), f_rng, p_rng );
+
+        while( mbedtls_mpi_cmp_mpi( &ctx->Vi, &ctx->P ) >= 0 )
+            MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->Vi, 1 ) );
+
+        if( count++ > 10 )
+            return( MBEDTLS_ERR_MPI_NOT_ACCEPTABLE );
+    }
+    while( mbedtls_mpi_cmp_int( &ctx->Vi, 1 ) <= 0 );
+
+    /* Vf = Vi^-X mod P */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &ctx->Vf, &ctx->Vi, &ctx->P ) );
+    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->Vf, &ctx->Vf, &ctx->X, &ctx->P, &ctx->RP ) );
+
+cleanup:
+    return( ret );
+}
+
+/*
+ * Derive and export the shared secret (G^Y)^X mod P
+ */
+int mbedtls_dhm_calc_secret( mbedtls_dhm_context *ctx,
+                     unsigned char *output, size_t output_size, size_t *olen,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng )
+{
+    int ret;
+    mbedtls_mpi GYb;
+
+    if( ctx == NULL || output_size < ctx->len )
+        return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
+
+    if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
+        return( ret );
+
+    mbedtls_mpi_init( &GYb );
+
+    /* Blind peer's value */
+    if( f_rng != NULL )
+    {
+        MBEDTLS_MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &GYb, &GYb, &ctx->P ) );
+    }
+    else
+        MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &GYb, &ctx->GY ) );
+
+    /* Do modular exponentiation */
+    MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->K, &GYb, &ctx->X,
+                          &ctx->P, &ctx->RP ) );
+
+    /* Unblind secret value */
+    if( f_rng != NULL )
+    {
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) );
+    }
+
+    *olen = mbedtls_mpi_size( &ctx->K );
+
+    MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->K, output, *olen ) );
+
+cleanup:
+    mbedtls_mpi_free( &GYb );
+
+    if( ret != 0 )
+        return( MBEDTLS_ERR_DHM_CALC_SECRET_FAILED + ret );
+
+    return( 0 );
+}
+
+/*
+ * Free the components of a DHM key
+ */
+void mbedtls_dhm_free( mbedtls_dhm_context *ctx )
+{
+    mbedtls_mpi_free( &ctx->pX); mbedtls_mpi_free( &ctx->Vf ); mbedtls_mpi_free( &ctx->Vi );
+    mbedtls_mpi_free( &ctx->RP ); mbedtls_mpi_free( &ctx->K ); mbedtls_mpi_free( &ctx->GY );
+    mbedtls_mpi_free( &ctx->GX ); mbedtls_mpi_free( &ctx->X ); mbedtls_mpi_free( &ctx->G );
+    mbedtls_mpi_free( &ctx->P );
+
+    mbedtls_zeroize( ctx, sizeof( mbedtls_dhm_context ) );
+}
+
+#if defined(MBEDTLS_ASN1_PARSE_C)
+/*
+ * Parse DHM parameters
+ */
+int mbedtls_dhm_parse_dhm( mbedtls_dhm_context *dhm, const unsigned char *dhmin,
+                   size_t dhminlen )
+{
+    int ret;
+    size_t len;
+    unsigned char *p, *end;
+#if defined(MBEDTLS_PEM_PARSE_C)
+    mbedtls_pem_context pem;
+
+    mbedtls_pem_init( &pem );
+
+    /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
+    if( dhminlen == 0 || dhmin[dhminlen - 1] != '\0' )
+        ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
+    else
+        ret = mbedtls_pem_read_buffer( &pem,
+                               "-----BEGIN DH PARAMETERS-----",
+                               "-----END DH PARAMETERS-----",
+                               dhmin, NULL, 0, &dhminlen );
+
+    if( ret == 0 )
+    {
+        /*
+         * Was PEM encoded
+         */
+        dhminlen = pem.buflen;
+    }
+    else if( ret != MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT )
+        goto exit;
+
+    p = ( ret == 0 ) ? pem.buf : (unsigned char *) dhmin;
+#else
+    p = (unsigned char *) dhmin;
+#endif /* MBEDTLS_PEM_PARSE_C */
+    end = p + dhminlen;
+
+    /*
+     *  DHParams ::= SEQUENCE {
+     *      prime              INTEGER,  -- P
+     *      generator          INTEGER,  -- g
+     *      privateValueLength INTEGER OPTIONAL
+     *  }
+     */
+    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
+            MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
+    {
+        ret = MBEDTLS_ERR_DHM_INVALID_FORMAT + ret;
+        goto exit;
+    }
+
+    end = p + len;
+
+    if( ( ret = mbedtls_asn1_get_mpi( &p, end, &dhm->P  ) ) != 0 ||
+        ( ret = mbedtls_asn1_get_mpi( &p, end, &dhm->G ) ) != 0 )
+    {
+        ret = MBEDTLS_ERR_DHM_INVALID_FORMAT + ret;
+        goto exit;
+    }
+
+    if( p != end )
+    {
+        /* This might be the optional privateValueLength.
+         * If so, we can cleanly discard it */
+        mbedtls_mpi rec;
+        mbedtls_mpi_init( &rec );
+        ret = mbedtls_asn1_get_mpi( &p, end, &rec );
+        mbedtls_mpi_free( &rec );
+        if ( ret != 0 )
+        {
+            ret = MBEDTLS_ERR_DHM_INVALID_FORMAT + ret;
+            goto exit;
+        }
+        if ( p != end )
+        {
+            ret = MBEDTLS_ERR_DHM_INVALID_FORMAT +
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
+            goto exit;
+        }
+    }
+
+    ret = 0;
+
+    dhm->len = mbedtls_mpi_size( &dhm->P );
+
+exit:
+#if defined(MBEDTLS_PEM_PARSE_C)
+    mbedtls_pem_free( &pem );
+#endif
+    if( ret != 0 )
+        mbedtls_dhm_free( dhm );
+
+    return( ret );
+}
+
+#if defined(MBEDTLS_FS_IO)
+/*
+ * Load all data from a file into a given buffer.
+ *
+ * The file is expected to contain either PEM or DER encoded data.
+ * A terminating null byte is always appended. It is included in the announced
+ * length only if the data looks like it is PEM encoded.
+ */
+static int load_file( const char *path, unsigned char **buf, size_t *n )
+{
+    FILE *f;
+    long size;
+
+    if( ( f = fopen( path, "rb" ) ) == NULL )
+        return( MBEDTLS_ERR_DHM_FILE_IO_ERROR );
+
+    fseek( f, 0, SEEK_END );
+    if( ( size = ftell( f ) ) == -1 )
+    {
+        fclose( f );
+        return( MBEDTLS_ERR_DHM_FILE_IO_ERROR );
+    }
+    fseek( f, 0, SEEK_SET );
+
+    *n = (size_t) size;
+
+    if( *n + 1 == 0 ||
+        ( *buf = mbedtls_calloc( 1, *n + 1 ) ) == NULL )
+    {
+        fclose( f );
+        return( MBEDTLS_ERR_DHM_ALLOC_FAILED );
+    }
+
+    if( fread( *buf, 1, *n, f ) != *n )
+    {
+        fclose( f );
+        mbedtls_free( *buf );
+        return( MBEDTLS_ERR_DHM_FILE_IO_ERROR );
+    }
+
+    fclose( f );
+
+    (*buf)[*n] = '\0';
+
+    if( strstr( (const char *) *buf, "-----BEGIN " ) != NULL )
+        ++*n;
+
+    return( 0 );
+}
+
+/*
+ * Load and parse DHM parameters
+ */
+int mbedtls_dhm_parse_dhmfile( mbedtls_dhm_context *dhm, const char *path )
+{
+    int ret;
+    size_t n;
+    unsigned char *buf;
+
+    if( ( ret = load_file( path, &buf, &n ) ) != 0 )
+        return( ret );
+
+    ret = mbedtls_dhm_parse_dhm( dhm, buf, n );
+
+    mbedtls_zeroize( buf, n );
+    mbedtls_free( buf );
+
+    return( ret );
+}
+#endif /* MBEDTLS_FS_IO */
+#endif /* MBEDTLS_ASN1_PARSE_C */
+
+#if defined(MBEDTLS_SELF_TEST)
+
+static const char mbedtls_test_dhm_params[] =
+"-----BEGIN DH PARAMETERS-----\r\n"
+"MIGHAoGBAJ419DBEOgmQTzo5qXl5fQcN9TN455wkOL7052HzxxRVMyhYmwQcgJvh\r\n"
+"1sa18fyfR9OiVEMYglOpkqVoGLN7qd5aQNNi5W7/C+VBdHTBJcGZJyyP5B3qcz32\r\n"
+"9mLJKudlVudV0Qxk5qUJaPZ/xupz0NyoVpviuiBOI1gNi8ovSXWzAgEC\r\n"
+"-----END DH PARAMETERS-----\r\n";
+
+static const size_t mbedtls_test_dhm_params_len = sizeof( mbedtls_test_dhm_params );
+
+/*
+ * Checkup routine
+ */
+int mbedtls_dhm_self_test( int verbose )
+{
+    int ret;
+    mbedtls_dhm_context dhm;
+
+    mbedtls_dhm_init( &dhm );
+
+    if( verbose != 0 )
+        mbedtls_printf( "  DHM parameter load: " );
+
+    if( ( ret = mbedtls_dhm_parse_dhm( &dhm,
+                    (const unsigned char *) mbedtls_test_dhm_params,
+                    mbedtls_test_dhm_params_len ) ) != 0 )
+    {
+        if( verbose != 0 )
+            mbedtls_printf( "failed\n" );
+
+        ret = 1;
+        goto exit;
+    }
+
+    if( verbose != 0 )
+        mbedtls_printf( "passed\n\n" );
+
+exit:
+    mbedtls_dhm_free( &dhm );
+
+    return( ret );
+}
+
+#endif /* MBEDTLS_SELF_TEST */
+
+#endif /* MBEDTLS_DHM_C */