Diff: library/ecdh.c

Revision:

0:cdf462088d13

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/library/ecdh.c	Thu Jan 05 00:18:44 2017 +0000
@@ -0,0 +1,264 @@
+/*
+ *  Elliptic curve Diffie-Hellman
+ *
+ *  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)
+ */
+
+/*
+ * References:
+ *
+ * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
+ * RFC 4492
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_ECDH_C)
+
+#include "mbedtls/ecdh.h"
+
+#include <string.h>
+
+/*
+ * Generate public key: simple wrapper around mbedtls_ecp_gen_keypair
+ */
+int mbedtls_ecdh_gen_public( mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng )
+{
+    return mbedtls_ecp_gen_keypair( grp, d, Q, f_rng, p_rng );
+}
+
+/*
+ * Compute shared secret (SEC1 3.3.1)
+ */
+int mbedtls_ecdh_compute_shared( mbedtls_ecp_group *grp, mbedtls_mpi *z,
+                         const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
+                         int (*f_rng)(void *, unsigned char *, size_t),
+                         void *p_rng )
+{
+    int ret;
+    mbedtls_ecp_point P;
+
+    mbedtls_ecp_point_init( &P );
+
+    /*
+     * Make sure Q is a valid pubkey before using it
+     */
+    MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
+
+    MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, &P, d, Q, f_rng, p_rng ) );
+
+    if( mbedtls_ecp_is_zero( &P ) )
+    {
+        ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
+        goto cleanup;
+    }
+
+    MBEDTLS_MPI_CHK( mbedtls_mpi_copy( z, &P.X ) );
+
+cleanup:
+    mbedtls_ecp_point_free( &P );
+
+    return( ret );
+}
+
+/*
+ * Initialize context
+ */
+void mbedtls_ecdh_init( mbedtls_ecdh_context *ctx )
+{
+    memset( ctx, 0, sizeof( mbedtls_ecdh_context ) );
+}
+
+/*
+ * Free context
+ */
+void mbedtls_ecdh_free( mbedtls_ecdh_context *ctx )
+{
+    if( ctx == NULL )
+        return;
+
+    mbedtls_ecp_group_free( &ctx->grp );
+    mbedtls_ecp_point_free( &ctx->Q   );
+    mbedtls_ecp_point_free( &ctx->Qp  );
+    mbedtls_ecp_point_free( &ctx->Vi  );
+    mbedtls_ecp_point_free( &ctx->Vf  );
+    mbedtls_mpi_free( &ctx->d  );
+    mbedtls_mpi_free( &ctx->z  );
+    mbedtls_mpi_free( &ctx->_d );
+}
+
+/*
+ * Setup and write the ServerKeyExhange parameters (RFC 4492)
+ *      struct {
+ *          ECParameters    curve_params;
+ *          ECPoint         public;
+ *      } ServerECDHParams;
+ */
+int mbedtls_ecdh_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
+                      unsigned char *buf, size_t blen,
+                      int (*f_rng)(void *, unsigned char *, size_t),
+                      void *p_rng )
+{
+    int ret;
+    size_t grp_len, pt_len;
+
+    if( ctx == NULL || ctx->grp.pbits == 0 )
+        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) )
+                != 0 )
+        return( ret );
+
+    if( ( ret = mbedtls_ecp_tls_write_group( &ctx->grp, &grp_len, buf, blen ) )
+                != 0 )
+        return( ret );
+
+    buf += grp_len;
+    blen -= grp_len;
+
+    if( ( ret = mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format,
+                                     &pt_len, buf, blen ) ) != 0 )
+        return( ret );
+
+    *olen = grp_len + pt_len;
+    return( 0 );
+}
+
+/*
+ * Read the ServerKeyExhange parameters (RFC 4492)
+ *      struct {
+ *          ECParameters    curve_params;
+ *          ECPoint         public;
+ *      } ServerECDHParams;
+ */
+int mbedtls_ecdh_read_params( mbedtls_ecdh_context *ctx,
+                      const unsigned char **buf, const unsigned char *end )
+{
+    int ret;
+
+    if( ( ret = mbedtls_ecp_tls_read_group( &ctx->grp, buf, end - *buf ) ) != 0 )
+        return( ret );
+
+    if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, buf, end - *buf ) )
+                != 0 )
+        return( ret );
+
+    return( 0 );
+}
+
+/*
+ * Get parameters from a keypair
+ */
+int mbedtls_ecdh_get_params( mbedtls_ecdh_context *ctx, const mbedtls_ecp_keypair *key,
+                     mbedtls_ecdh_side side )
+{
+    int ret;
+
+    if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 )
+        return( ret );
+
+    /* If it's not our key, just import the public part as Qp */
+    if( side == MBEDTLS_ECDH_THEIRS )
+        return( mbedtls_ecp_copy( &ctx->Qp, &key->Q ) );
+
+    /* Our key: import public (as Q) and private parts */
+    if( side != MBEDTLS_ECDH_OURS )
+        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 ||
+        ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 )
+        return( ret );
+
+    return( 0 );
+}
+
+/*
+ * Setup and export the client public value
+ */
+int mbedtls_ecdh_make_public( mbedtls_ecdh_context *ctx, size_t *olen,
+                      unsigned char *buf, size_t blen,
+                      int (*f_rng)(void *, unsigned char *, size_t),
+                      void *p_rng )
+{
+    int ret;
+
+    if( ctx == NULL || ctx->grp.pbits == 0 )
+        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) )
+                != 0 )
+        return( ret );
+
+    return mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format,
+                                olen, buf, blen );
+}
+
+/*
+ * Parse and import the client's public value
+ */
+int mbedtls_ecdh_read_public( mbedtls_ecdh_context *ctx,
+                      const unsigned char *buf, size_t blen )
+{
+    int ret;
+    const unsigned char *p = buf;
+
+    if( ctx == NULL )
+        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, &p, blen ) ) != 0 )
+        return( ret );
+
+    if( (size_t)( p - buf ) != blen )
+        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+
+    return( 0 );
+}
+
+/*
+ * Derive and export the shared secret
+ */
+int mbedtls_ecdh_calc_secret( mbedtls_ecdh_context *ctx, size_t *olen,
+                      unsigned char *buf, size_t blen,
+                      int (*f_rng)(void *, unsigned char *, size_t),
+                      void *p_rng )
+{
+    int ret;
+
+    if( ctx == NULL )
+        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_ecdh_compute_shared( &ctx->grp, &ctx->z, &ctx->Qp, &ctx->d,
+                                     f_rng, p_rng ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    if( mbedtls_mpi_size( &ctx->z ) > blen )
+        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+
+    *olen = ctx->grp.pbits / 8 + ( ( ctx->grp.pbits % 8 ) != 0 );
+    return mbedtls_mpi_write_binary( &ctx->z, buf, *olen );
+}
+
+#endif /* MBEDTLS_ECDH_C */