Diff: SSL/library/dhm.c

Revision:

0:796d0f61a05b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SSL/library/dhm.c	Thu Sep 27 06:34:22 2018 +0000
@@ -0,0 +1,589 @@
+/*
+ *  Diffie-Hellman-Merkle key exchange
+ *
+ *  Copyright (C) 2006-2014, Brainspark B.V.
+ *
+ *  This file is part of PolarSSL (http://www.polarssl.org)
+ *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
+ *
+ *  All rights reserved.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+/*
+ *  Reference:
+ *
+ *  http://www.cacr.math.uwaterloo.ca/hac/ (chapter 12)
+ */
+
+#if !defined(POLARSSL_CONFIG_FILE)
+#include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
+
+#if defined(POLARSSL_DHM_C)
+
+#include "polarssl/dhm.h"
+
+#if defined(POLARSSL_PEM_PARSE_C)
+#include "polarssl/pem.h"
+#endif
+
+#if defined(POLARSSL_ASN1_PARSE_C)
+#include "polarssl/asn1.h"
+#endif
+
+#if defined(POLARSSL_PLATFORM_C)
+#include "polarssl/platform.h"
+#else
+#include <stdlib.h>
+#define polarssl_printf     printf
+#define polarssl_malloc     malloc
+#define polarssl_free       free
+#endif
+
+/*
+ * helper to validate the mpi size and import it
+ */
+static int dhm_read_bignum( mpi *X,
+                            unsigned char **p,
+                            const unsigned char *end )
+{
+    int ret, n;
+
+    if( end - *p < 2 )
+        return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
+
+    n = ( (*p)[0] << 8 ) | (*p)[1];
+    (*p) += 2;
+
+    if( (int)( end - *p ) < n )
+        return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
+
+    if( ( ret = mpi_read_binary( X, *p, n ) ) != 0 )
+        return( POLARSSL_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 mpi *param, const mpi *P )
+{
+    mpi L, U;
+    int ret = POLARSSL_ERR_DHM_BAD_INPUT_DATA;
+
+    mpi_init( &L ); mpi_init( &U );
+
+    MPI_CHK( mpi_lset( &L, 2 ) );
+    MPI_CHK( mpi_sub_int( &U, P, 2 ) );
+
+    if( mpi_cmp_mpi( param, &L ) >= 0 &&
+        mpi_cmp_mpi( param, &U ) <= 0 )
+    {
+        ret = 0;
+    }
+
+cleanup:
+    mpi_free( &L ); mpi_free( &U );
+    return( ret );
+}
+
+/*
+ * Parse the ServerKeyExchange parameters
+ */
+int dhm_read_params( dhm_context *ctx,
+                     unsigned char **p,
+                     const unsigned char *end )
+{
+    int ret;
+
+    dhm_free( ctx );
+
+    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 = mpi_size( &ctx->P );
+
+    return( 0 );
+}
+
+/*
+ * Setup and write the ServerKeyExchange parameters
+ */
+int dhm_make_params( 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( mpi_cmp_int( &ctx->P, 0 ) == 0 )
+        return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
+
+    /*
+     * Generate X as large as possible ( < P )
+     */
+    do
+    {
+        mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
+
+        while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
+            MPI_CHK( mpi_shift_r( &ctx->X, 1 ) );
+
+        if( count++ > 10 )
+            return( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED );
+    }
+    while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
+
+    /*
+     * Calculate GX = G^X mod P
+     */
+    MPI_CHK( 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)                     \
+    MPI_CHK( mpi_write_binary( X, p + 2, n ) ); \
+    *p++ = (unsigned char)( n >> 8 );           \
+    *p++ = (unsigned char)( n      ); p += n;
+
+    n1 = mpi_size( &ctx->P  );
+    n2 = mpi_size( &ctx->G  );
+    n3 = 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( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED + ret );
+
+    return( 0 );
+}
+
+/*
+ * Import the peer's public value G^Y
+ */
+int dhm_read_public( dhm_context *ctx,
+                     const unsigned char *input, size_t ilen )
+{
+    int ret;
+
+    if( ctx == NULL || ilen < 1 || ilen > ctx->len )
+        return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
+
+    if( ( ret = mpi_read_binary( &ctx->GY, input, ilen ) ) != 0 )
+        return( POLARSSL_ERR_DHM_READ_PUBLIC_FAILED + ret );
+
+    return( 0 );
+}
+
+/*
+ * Create own private value X and export G^X
+ */
+int dhm_make_public( 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( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
+
+    if( mpi_cmp_int( &ctx->P, 0 ) == 0 )
+        return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
+
+    /*
+     * generate X and calculate GX = G^X mod P
+     */
+    do
+    {
+        mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
+
+        while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
+            MPI_CHK( mpi_shift_r( &ctx->X, 1 ) );
+
+        if( count++ > 10 )
+            return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED );
+    }
+    while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
+
+    MPI_CHK( 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 );
+
+    MPI_CHK( mpi_write_binary( &ctx->GX, output, olen ) );
+
+cleanup:
+
+    if( ret != 0 )
+        return( POLARSSL_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( 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( mpi_cmp_mpi( &ctx->X, &ctx->pX ) != 0 )
+    {
+        MPI_CHK( mpi_copy( &ctx->pX, &ctx->X ) );
+        MPI_CHK( mpi_lset( &ctx->Vi, 1 ) );
+        MPI_CHK( 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( mpi_cmp_int( &ctx->Vi, 1 ) != 0 )
+    {
+        MPI_CHK( mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
+        MPI_CHK( mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->P ) );
+
+        MPI_CHK( mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
+        MPI_CHK( 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
+    {
+        mpi_fill_random( &ctx->Vi, mpi_size( &ctx->P ), f_rng, p_rng );
+
+        while( mpi_cmp_mpi( &ctx->Vi, &ctx->P ) >= 0 )
+            MPI_CHK( mpi_shift_r( &ctx->Vi, 1 ) );
+
+        if( count++ > 10 )
+            return( POLARSSL_ERR_MPI_NOT_ACCEPTABLE );
+    }
+    while( mpi_cmp_int( &ctx->Vi, 1 ) <= 0 );
+
+    /* Vf = Vi^-X mod P */
+    MPI_CHK( mpi_inv_mod( &ctx->Vf, &ctx->Vi, &ctx->P ) );
+    MPI_CHK( 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 dhm_calc_secret( dhm_context *ctx,
+                     unsigned char *output, size_t *olen,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng )
+{
+    int ret;
+    mpi GYb;
+
+    if( ctx == NULL || *olen < ctx->len )
+        return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
+
+    if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
+        return( ret );
+
+    mpi_init( &GYb );
+
+    /* Blind peer's value */
+    if( f_rng != NULL )
+    {
+        MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) );
+        MPI_CHK( mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) );
+        MPI_CHK( mpi_mod_mpi( &GYb, &GYb, &ctx->P ) );
+    }
+    else
+        MPI_CHK( mpi_copy( &GYb, &ctx->GY ) );
+
+    /* Do modular exponentiation */
+    MPI_CHK( mpi_exp_mod( &ctx->K, &GYb, &ctx->X,
+                          &ctx->P, &ctx->RP ) );
+
+    /* Unblind secret value */
+    if( f_rng != NULL )
+    {
+        MPI_CHK( mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) );
+        MPI_CHK( mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) );
+    }
+
+    *olen = mpi_size( &ctx->K );
+
+    MPI_CHK( mpi_write_binary( &ctx->K, output, *olen ) );
+
+cleanup:
+    mpi_free( &GYb );
+
+    if( ret != 0 )
+        return( POLARSSL_ERR_DHM_CALC_SECRET_FAILED + ret );
+
+    return( 0 );
+}
+
+/*
+ * Free the components of a DHM key
+ */
+void dhm_free( dhm_context *ctx )
+{
+    mpi_free( &ctx->pX); mpi_free( &ctx->Vf ); mpi_free( &ctx->Vi );
+    mpi_free( &ctx->RP ); mpi_free( &ctx->K ); mpi_free( &ctx->GY );
+    mpi_free( &ctx->GX ); mpi_free( &ctx->X ); mpi_free( &ctx->G );
+    mpi_free( &ctx->P );
+
+    memset( ctx, 0, sizeof( dhm_context ) );
+}
+
+#if defined(POLARSSL_ASN1_PARSE_C)
+/*
+ * Parse DHM parameters
+ */
+int dhm_parse_dhm( dhm_context *dhm, const unsigned char *dhmin,
+                   size_t dhminlen )
+{
+    int ret;
+    size_t len;
+    unsigned char *p, *end;
+#if defined(POLARSSL_PEM_PARSE_C)
+    pem_context pem;
+
+    pem_init( &pem );
+    memset( dhm, 0, sizeof( dhm_context ) );
+
+    ret = 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 != POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT )
+        goto exit;
+
+    p = ( ret == 0 ) ? pem.buf : (unsigned char *) dhmin;
+#else
+    p = (unsigned char *) dhmin;
+#endif /* POLARSSL_PEM_PARSE_C */
+    end = p + dhminlen;
+
+    /*
+     *  DHParams ::= SEQUENCE {
+     *      prime            INTEGER,  -- P
+     *      generator        INTEGER,  -- g
+     *  }
+     */
+    if( ( ret = asn1_get_tag( &p, end, &len,
+            ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
+    {
+        ret = POLARSSL_ERR_DHM_INVALID_FORMAT + ret;
+        goto exit;
+    }
+
+    end = p + len;
+
+    if( ( ret = asn1_get_mpi( &p, end, &dhm->P  ) ) != 0 ||
+        ( ret = asn1_get_mpi( &p, end, &dhm->G ) ) != 0 )
+    {
+        ret = POLARSSL_ERR_DHM_INVALID_FORMAT + ret;
+        goto exit;
+    }
+
+    if( p != end )
+    {
+        ret = POLARSSL_ERR_DHM_INVALID_FORMAT +
+              POLARSSL_ERR_ASN1_LENGTH_MISMATCH;
+        goto exit;
+    }
+
+    ret = 0;
+
+    dhm->len = mpi_size( &dhm->P );
+
+exit:
+#if defined(POLARSSL_PEM_PARSE_C)
+    pem_free( &pem );
+#endif
+    if( ret != 0 )
+        dhm_free( dhm );
+
+    return( ret );
+}
+
+#if defined(POLARSSL_FS_IO)
+/*
+ * Load all data from a file into a given buffer.
+ */
+static int load_file( const char *path, unsigned char **buf, size_t *n )
+{
+    FILE *f;
+    long size;
+
+    if( ( f = fopen( path, "rb" ) ) == NULL )
+        return( POLARSSL_ERR_DHM_FILE_IO_ERROR );
+
+    fseek( f, 0, SEEK_END );
+    if( ( size = ftell( f ) ) == -1 )
+    {
+        fclose( f );
+        return( POLARSSL_ERR_DHM_FILE_IO_ERROR );
+    }
+    fseek( f, 0, SEEK_SET );
+
+    *n = (size_t) size;
+
+    if( *n + 1 == 0 ||
+        ( *buf = (unsigned char *) polarssl_malloc( *n + 1 ) ) == NULL )
+    {
+        fclose( f );
+        return( POLARSSL_ERR_DHM_MALLOC_FAILED );
+    }
+
+    if( fread( *buf, 1, *n, f ) != *n )
+    {
+        fclose( f );
+        polarssl_free( *buf );
+        return( POLARSSL_ERR_DHM_FILE_IO_ERROR );
+    }
+
+    fclose( f );
+
+    (*buf)[*n] = '\0';
+
+    return( 0 );
+}
+
+/*
+ * Load and parse DHM parameters
+ */
+int dhm_parse_dhmfile( 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 = dhm_parse_dhm( dhm, buf, n );
+
+    memset( buf, 0, n + 1 );
+    polarssl_free( buf );
+
+    return( ret );
+}
+#endif /* POLARSSL_FS_IO */
+#endif /* POLARSSL_ASN1_PARSE_C */
+
+#if defined(POLARSSL_SELF_TEST)
+
+#include "polarssl/certs.h"
+
+/*
+ * Checkup routine
+ */
+int dhm_self_test( int verbose )
+{
+#if defined(POLARSSL_CERTS_C)
+    int ret;
+    dhm_context dhm;
+
+    if( verbose != 0 )
+        polarssl_printf( "  DHM parameter load: " );
+
+    if( ( ret = dhm_parse_dhm( &dhm, (const unsigned char *) test_dhm_params,
+                               strlen( test_dhm_params ) ) ) != 0 )
+    {
+        if( verbose != 0 )
+            polarssl_printf( "failed\n" );
+
+        return( ret );
+    }
+
+    if( verbose != 0 )
+        polarssl_printf( "passed\n\n" );
+
+    dhm_free( &dhm );
+
+    return( 0 );
+#else
+    if( verbose != 0 )
+        polarssl_printf( "  DHM parameter load: skipped\n" );
+
+    return( 0 );
+#endif /* POLARSSL_CERTS_C */
+}
+
+#endif /* POLARSSL_SELF_TEST */
+
+#endif /* POLARSSL_DHM_C */
+
+