added ECDH with OpenSSL (see RFC 4753)
authorTobias Brunner <tobias@strongswan.org>
Thu, 22 May 2008 11:39:17 +0000 (11:39 -0000)
committerTobias Brunner <tobias@strongswan.org>
Thu, 22 May 2008 11:39:17 +0000 (11:39 -0000)
src/charon/config/proposal.c
src/libstrongswan/crypto/diffie_hellman.c
src/libstrongswan/crypto/diffie_hellman.h
src/libstrongswan/plugins/openssl/Makefile.am
src/libstrongswan/plugins/openssl/openssl_ec_diffie_hellman.c [new file with mode: 0644]
src/libstrongswan/plugins/openssl/openssl_ec_diffie_hellman.h [new file with mode: 0644]
src/libstrongswan/plugins/openssl/openssl_plugin.c

index 71bb3a2..45d0108 100644 (file)
@@ -766,6 +766,18 @@ static status_t add_string_algo(private_proposal_t *this, chunk_t alg)
        {
                add_algorithm(this, DIFFIE_HELLMAN_GROUP, MODP_8192_BIT, 0);
        }
+       else if (strncmp(alg.ptr, "ecp256", alg.len) == 0)
+       {
+               add_algorithm(this, DIFFIE_HELLMAN_GROUP, ECP_256_BIT, 0);
+       }
+       else if (strncmp(alg.ptr, "ecp384", alg.len) == 0)
+       {
+               add_algorithm(this, DIFFIE_HELLMAN_GROUP, ECP_384_BIT, 0);
+       }
+       else if (strncmp(alg.ptr, "ecp521", alg.len) == 0)
+       {
+               add_algorithm(this, DIFFIE_HELLMAN_GROUP, ECP_521_BIT, 0);
+       }
        else
        {
                return FAILED;
index 9227087..a915074 100644 (file)
@@ -24,11 +24,14 @@ ENUM_BEGIN(diffie_hellman_group_names, MODP_NONE, MODP_1024_BIT,
        "MODP_1024_BIT");
 ENUM_NEXT(diffie_hellman_group_names, MODP_1536_BIT, MODP_1536_BIT, MODP_1024_BIT,
        "MODP_1536_BIT");
-ENUM_NEXT(diffie_hellman_group_names, MODP_2048_BIT, MODP_8192_BIT, MODP_1536_BIT,
+ENUM_NEXT(diffie_hellman_group_names, MODP_2048_BIT, ECP_521_BIT, MODP_1536_BIT,
        "MODP_2048_BIT",
        "MODP_3072_BIT",
        "MODP_4096_BIT",
        "MODP_6144_BIT",
-       "MODP_8192_BIT");
-ENUM_END(diffie_hellman_group_names, MODP_8192_BIT);
+       "MODP_8192_BIT"
+       "ECP_256_BIT",
+       "ECP_384_BIT",
+       "ECP_521_BIT");
+ENUM_END(diffie_hellman_group_names, ECP_521_BIT);
 
index 07e475b..53d89c3 100644 (file)
@@ -34,6 +34,8 @@ typedef struct diffie_hellman_t diffie_hellman_t;
  *
  * The modulus (or group) to use for a Diffie-Hellman calculation.
  * See IKEv2 RFC 3.3.2 and RFC 3526.
+ * 
+ * ECP groups are defined in RFC 4753.
  */
 enum diffie_hellman_group_t {
        MODP_NONE = 0,
@@ -44,7 +46,11 @@ enum diffie_hellman_group_t {
        MODP_3072_BIT = 15,
        MODP_4096_BIT = 16,
        MODP_6144_BIT = 17,
-       MODP_8192_BIT = 18
+       MODP_8192_BIT = 18,
+       ECP_256_BIT = 19,
+       ECP_384_BIT = 20,
+       ECP_521_BIT = 21,
+       
 };
 
 /**
index 4f0cb86..b2bb03f 100644 (file)
@@ -10,7 +10,8 @@ libstrongswan_openssl_la_SOURCES = openssl_plugin.h openssl_plugin.c \
        openssl_hasher.c openssl_hasher.h \
        openssl_diffie_hellman.c openssl_diffie_hellman.h \
        openssl_rsa_private_key.c openssl_rsa_private_key.h \
-       openssl_rsa_public_key.c openssl_rsa_public_key.h
+       openssl_rsa_public_key.c openssl_rsa_public_key.h \
+       openssl_ec_diffie_hellman.c openssl_ec_diffie_hellman.h
 
 libstrongswan_openssl_la_LDFLAGS = -module
 libstrongswan_openssl_la_LIBADD  = -lssl
diff --git a/src/libstrongswan/plugins/openssl/openssl_ec_diffie_hellman.c b/src/libstrongswan/plugins/openssl/openssl_ec_diffie_hellman.c
new file mode 100644 (file)
index 0000000..0aeaf6b
--- /dev/null
@@ -0,0 +1,360 @@
+/*
+ * Copyright (C) 2008 Tobias Brunner
+ * Hochschule fuer Technik Rapperswil
+ *
+ * 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.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * 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.
+ *
+ * $Id$
+ */
+
+#include <openssl/ec.h>
+#include <openssl/objects.h>
+
+#include "openssl_ec_diffie_hellman.h"
+
+#include <debug.h>
+
+#define COORD_LEN(group) ((EC_GROUP_get_degree(group) + 7) / 8)
+
+typedef struct private_openssl_ec_diffie_hellman_t private_openssl_ec_diffie_hellman_t;
+
+/**
+ * Private data of an openssl_ec_diffie_hellman_t object.
+ */
+struct private_openssl_ec_diffie_hellman_t {
+       /**
+        * Public openssl_ec_diffie_hellman_t interface.
+        */
+       openssl_ec_diffie_hellman_t public;
+       
+       /**
+        * Diffie Hellman group number.
+        */
+       u_int16_t group;
+       
+       /**
+        * EC private (public) key
+        */
+       EC_KEY *key;
+       
+       /**
+        * EC group
+        */
+       const EC_GROUP *ec_group;
+       
+       /**
+        * Other public key
+        */
+       EC_POINT *pub_key;
+       
+       /**
+        * Shared secret
+        */
+       chunk_t shared_secret;
+
+       /**
+        * True if shared secret is computed
+        */
+       bool computed;
+};
+
+/**
+ * Convert a chunk to an EC_POINT (which must already exist). The x and y
+ * coordinates of the point have to be concatenated in the chunk.
+ */
+static bool chunk2ecp(const EC_GROUP *group, chunk_t chunk, EC_POINT *point)
+{
+       BN_CTX *ctx;
+       BIGNUM *x, *y;
+       int coord_len;
+       bool ret = FALSE;
+       
+       ctx = BN_CTX_new();
+       if (!ctx)
+       {
+               return FALSE;
+       }
+       
+       BN_CTX_start(ctx);
+       x = BN_CTX_get(ctx);
+       y = BN_CTX_get(ctx);
+       if (!x || !y)
+       {
+               goto error;
+       }
+       
+       coord_len = COORD_LEN(group);
+       if (chunk.len != coord_len * 2)
+       {
+               goto error;
+       }
+       
+       if (!BN_bin2bn(chunk.ptr, coord_len, x) ||
+               !BN_bin2bn(chunk.ptr + coord_len, coord_len, y))
+       {
+               goto error;
+       }
+       
+       if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx))
+       {
+               goto error;
+       }
+       
+       ret = TRUE;
+error:
+       BN_CTX_end(ctx);
+       BN_CTX_free(ctx);
+       return ret;
+}
+
+/**
+ * Convert an EC_POINT to a chunk by concatenating the x and y coordinates of
+ * the point. This function allocates memory for the chunk.
+ */
+static bool ecp2chunk(const EC_GROUP *group, const EC_POINT *point, chunk_t *chunk)
+{
+       BN_CTX *ctx;
+       BIGNUM *x, *y;
+       int coord_len, offset;
+       bool ret = FALSE;
+       
+       ctx = BN_CTX_new();
+       if (!ctx)
+       {
+               return FALSE;
+       }
+       
+       BN_CTX_start(ctx);
+       x = BN_CTX_get(ctx);
+       y = BN_CTX_get(ctx);
+       if (!x || !y)
+       {
+               goto error;
+       }
+       
+       if (!EC_POINT_get_affine_coordinates_GFp(group, point, x, y, ctx))
+       {
+               goto error;
+       }
+       
+       coord_len = COORD_LEN(group);
+       chunk->len = coord_len * 2;
+       chunk->ptr = malloc(chunk->len);
+       memset(chunk->ptr, 0, chunk->len);
+       
+       offset = coord_len - BN_num_bytes(x);
+       if (!BN_bn2bin(x, chunk->ptr + offset))
+       {
+               chunk_free(chunk);
+               goto error;
+       }
+       
+       offset = coord_len - BN_num_bytes(y);
+       if (!BN_bn2bin(y, chunk->ptr + coord_len + offset))
+       {
+               chunk_free(chunk);
+               goto error;
+       }
+       
+       ret = TRUE;
+error:
+       BN_CTX_end(ctx);
+       BN_CTX_free(ctx);
+       return ret;
+}
+
+/**
+ * Compute the shared secret.
+ * 
+ * We cannot use the function ECDH_compute_key() because that returns only the
+ * x coordinate of the shared secret point (which is defined, for instance, in
+ * 'NIST SP 800-56A').
+ * However, we need both coordinates as RFC 4753 says: "The Diffie-Hellman
+ *   public value is obtained by concatenating the x and y values. The format
+ *   of the Diffie-Hellman shared secret value is the same as that of the
+ *   Diffie-Hellman public value."
+ */
+static bool compute_shared_key(private_openssl_ec_diffie_hellman_t *this, chunk_t *shared_secret)
+{
+       const BIGNUM *priv_key;
+       EC_POINT *secret;
+       bool ret = FALSE;
+       
+       priv_key = EC_KEY_get0_private_key(this->key);
+       if (!priv_key)
+       {
+               goto error;
+       }
+       
+       secret = EC_POINT_new(this->ec_group);
+       if (!secret)
+       {
+               goto error;
+       }
+
+       if (!EC_POINT_mul(this->ec_group, secret, NULL, this->pub_key, priv_key, NULL))
+       {
+               goto error;
+       }
+       
+       if (!ecp2chunk(this->ec_group, secret, shared_secret))
+       {
+               goto error;
+       }
+       
+       ret = TRUE;
+error:
+       if (secret)
+       {
+               EC_POINT_clear_free(secret);
+       }
+       return ret;
+}
+
+/**
+ * Implementation of openssl_ec_diffie_hellman_t.set_other_public_value.
+ */
+static void set_other_public_value(private_openssl_ec_diffie_hellman_t *this, chunk_t value)
+{
+       if (!chunk2ecp(this->ec_group, value, this->pub_key))
+       {
+               DBG1("ECDH public value is malformed");
+               return;
+       }
+       
+       chunk_free(&this->shared_secret);
+       
+       if (!compute_shared_key(this, &this->shared_secret)) {
+               DBG1("ECDH shared secret computation failed");
+               return;
+       }
+       
+       this->computed = TRUE;
+}
+
+/**
+ * Implementation of openssl_ec_diffie_hellman_t.get_other_public_value.
+ */
+static status_t get_other_public_value(private_openssl_ec_diffie_hellman_t *this, 
+                                                                          chunk_t *value)
+{
+       if (!this->computed)
+       {
+               return FAILED;
+       }
+       
+       if (!ecp2chunk(this->ec_group, this->pub_key, value))
+       {
+               return FAILED;
+       }
+       return SUCCESS;
+}
+
+/**
+ * Implementation of openssl_ec_diffie_hellman_t.get_my_public_value.
+ */
+static void get_my_public_value(private_openssl_ec_diffie_hellman_t *this,chunk_t *value)
+{
+       ecp2chunk(this->ec_group, EC_KEY_get0_public_key(this->key), value);
+}
+
+/**
+ * Implementation of openssl_ec_diffie_hellman_t.get_shared_secret.
+ */
+static status_t get_shared_secret(private_openssl_ec_diffie_hellman_t *this, chunk_t *secret)
+{
+       if (!this->computed)
+       {
+               return FAILED;
+       }
+       *secret = chunk_clone(this->shared_secret);
+       return SUCCESS;
+}
+
+/**
+ * Implementation of openssl_ec_diffie_hellman_t.get_dh_group.
+ */
+static diffie_hellman_group_t get_dh_group(private_openssl_ec_diffie_hellman_t *this)
+{
+       return this->group;
+}
+
+/**
+ * Implementation of openssl_ec_diffie_hellman_t.destroy.
+ */
+static void destroy(private_openssl_ec_diffie_hellman_t *this)
+{
+       EC_POINT_clear_free(this->pub_key);
+       EC_KEY_free(this->key);
+       chunk_free(&this->shared_secret);
+       free(this);
+}
+
+/*
+ * Described in header.
+ */
+openssl_ec_diffie_hellman_t *openssl_ec_diffie_hellman_create(diffie_hellman_group_t group)
+{
+       private_openssl_ec_diffie_hellman_t *this = malloc_thing(private_openssl_ec_diffie_hellman_t);
+       
+       this->public.dh.get_shared_secret = (status_t (*)(diffie_hellman_t *, chunk_t *)) get_shared_secret;
+       this->public.dh.set_other_public_value = (void (*)(diffie_hellman_t *, chunk_t )) set_other_public_value;
+       this->public.dh.get_other_public_value = (status_t (*)(diffie_hellman_t *, chunk_t *)) get_other_public_value;
+       this->public.dh.get_my_public_value = (void (*)(diffie_hellman_t *, chunk_t *)) get_my_public_value;
+       this->public.dh.get_dh_group = (diffie_hellman_group_t (*)(diffie_hellman_t *)) get_dh_group;
+       this->public.dh.destroy = (void (*)(diffie_hellman_t *)) destroy;
+       
+       switch (group)
+       {
+               case ECP_256_BIT:
+                       this->key = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
+                       break;
+               case ECP_384_BIT:
+                       this->key = EC_KEY_new_by_curve_name(NID_secp384r1);
+                       break;
+               case ECP_521_BIT:
+                       this->key = EC_KEY_new_by_curve_name(NID_secp521r1);
+                       break;
+               default:
+                       this->key = NULL;
+                       break;
+       }
+       
+       if (!this->key)
+       {
+               free(this);
+               return NULL;
+       }
+       
+       /* caching the EC group */
+       this->ec_group = EC_KEY_get0_group(this->key);
+       
+       this->pub_key = EC_POINT_new(this->ec_group);
+       if (!this->pub_key)
+       {
+               free(this);
+               return NULL;
+       }
+       
+       /* generate an EC private (public) key */
+       if (!EC_KEY_generate_key(this->key))
+       {
+               free(this);
+               return NULL;
+       }
+       
+       this->group = group;
+       this->computed = FALSE;
+       
+       this->shared_secret = chunk_empty;
+       
+       return &this->public;
+}
diff --git a/src/libstrongswan/plugins/openssl/openssl_ec_diffie_hellman.h b/src/libstrongswan/plugins/openssl/openssl_ec_diffie_hellman.h
new file mode 100644 (file)
index 0000000..69d60c6
--- /dev/null
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2008 Tobias Brunner
+ * Hochschule fuer Technik Rapperswil
+ *
+ * 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.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * 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.
+ */
+
+/**
+ * @defgroup openssl_ec_diffie_hellman openssl_ec_diffie_hellman
+ * @{ @ingroup openssl_p
+ */
+
+#ifndef OPENSSL_EC_DIFFIE_HELLMAN_H_
+#define OPENSSL_EC_DIFFIE_HELLMAN_H_
+
+typedef struct openssl_ec_diffie_hellman_t openssl_ec_diffie_hellman_t;
+
+#include <library.h>
+
+/**
+ * Implementation of the EC Diffie-Hellman algorithm using OpenSSL.
+ */
+struct openssl_ec_diffie_hellman_t {
+       
+       /**
+        * Implements diffie_hellman_t interface.
+        */
+       diffie_hellman_t dh;
+};
+
+/**
+ * Creates a new openssl_ec_diffie_hellman_t object.
+ * 
+ * @param group                        EC Diffie Hellman group number to use
+ * @return                             openssl_ec_diffie_hellman_t object, NULL if not supported
+ */
+openssl_ec_diffie_hellman_t *openssl_ec_diffie_hellman_create(diffie_hellman_group_t group);
+
+#endif /*OPENSSL_EC_DIFFIE_HELLMAN_H_ @}*/
+
index c888c2f..7e57c7a 100644 (file)
@@ -23,6 +23,7 @@
 #include "openssl_crypter.h"
 #include "openssl_hasher.h"
 #include "openssl_diffie_hellman.h"
+#include "openssl_ec_diffie_hellman.h"
 #include "openssl_rsa_private_key.h"
 #include "openssl_rsa_public_key.h"
 
@@ -50,6 +51,8 @@ static void destroy(private_openssl_plugin_t *this)
                                        (hasher_constructor_t)openssl_hasher_create);
        lib->crypto->remove_dh(lib->crypto, 
                                        (dh_constructor_t)openssl_diffie_hellman_create);
+       lib->crypto->remove_dh(lib->crypto, 
+                                       (dh_constructor_t)openssl_ec_diffie_hellman_create);
        lib->creds->remove_builder(lib->creds,
                                        (builder_constructor_t)openssl_rsa_private_key_builder);
        lib->creds->remove_builder(lib->creds,
@@ -121,6 +124,14 @@ plugin_t *plugin_create()
        lib->crypto->add_dh(lib->crypto, MODP_8192_BIT, 
                                                (dh_constructor_t)openssl_diffie_hellman_create);
        
+       /* ec diffie hellman */
+       lib->crypto->add_dh(lib->crypto, ECP_256_BIT,
+                                               (dh_constructor_t)openssl_ec_diffie_hellman_create);
+       lib->crypto->add_dh(lib->crypto, ECP_384_BIT,
+                                               (dh_constructor_t)openssl_ec_diffie_hellman_create);
+       lib->crypto->add_dh(lib->crypto, ECP_521_BIT,
+                                               (dh_constructor_t)openssl_ec_diffie_hellman_create);
+       
        /* rsa */
        lib->creds->add_builder(lib->creds, CRED_PRIVATE_KEY, KEY_RSA,
                                                (builder_constructor_t)openssl_rsa_private_key_builder);