libsimaka provides cryptographic functionality used in EAP-SIM and EAP-AKA

src/libsimaka/Makefile.am

@@ -2,5 +2,6 @@
 INCLUDES = -I$(top_srcdir)/src/libstrongswan -I$(top_srcdir)/src/charon
 
 noinst_LIBRARIES = libsimaka.a
-libsimaka_a_SOURCES = simaka_message.h simaka_message.c
+libsimaka_a_SOURCES = simaka_message.h simaka_message.c \
+  simaka_crypto.h simaka_crypto.c
 

src/libsimaka/simaka_crypto.c

@@ -0,0 +1,178 @@
+/*
+ * Copyright (C) 2009 Martin Willi
+ * 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.
+ */
+
+#include "simaka_crypto.h"
+
+#include <daemon.h>
+
+/** length of the k_encr key */
+#define KENCR_LEN 16
+/** length of the k_auth key */
+#define KAUTH_LEN 16
+/** length of the MSK */
+#define MSK_LEN 64
+/** length of the EMSK */
+#define EMSK_LEN 64
+
+typedef struct private_simaka_crypto_t private_simaka_crypto_t;
+
+/**
+ * Private data of an simaka_crypto_t object.
+ */
+struct private_simaka_crypto_t {
+
+	/**
+	 * Public simaka_crypto_t interface.
+	 */
+	simaka_crypto_t public;
+
+	/**
+	 * signer to create/verify AT_MAC
+	 */
+	signer_t *signer;
+
+	/**
+	 * crypter to encrypt/decrypt AT_ENCR_DATA
+	 */
+	crypter_t *crypter;
+
+	/**
+	 * hasher used in key derivation
+	 */
+	hasher_t *hasher;
+
+	/**
+	 * PRF function used in key derivation
+	 */
+	prf_t *prf;
+
+	/**
+	 * Random number generator to generate nonces
+	 */
+	rng_t *rng;
+
+	/**
+	 * Have k_encr/k_auth been derived?
+	 */
+	bool derived;
+};
+
+/**
+ * Implementation of simaka_crypto_t.get_signer
+ */
+static signer_t* get_signer(private_simaka_crypto_t *this)
+{
+	return this->derived ? this->signer : NULL;
+}
+
+/**
+ * Implementation of simaka_crypto_t.get_crypter
+ */
+static crypter_t* get_crypter(private_simaka_crypto_t *this)
+{
+	return this->derived ? this->crypter : NULL;
+}
+
+/**
+ * Implementation of simaka_crypto_t.get_rng
+ */
+static rng_t* get_rng(private_simaka_crypto_t *this)
+{
+	return this->rng;
+}
+
+/**
+ * Implementation of simaka_crypto_t.derive_keys_full
+ */
+static chunk_t derive_keys_full(private_simaka_crypto_t *this,
+								identification_t *id, chunk_t data)
+{
+
+	char mk[HASH_SIZE_SHA1], k_encr[KENCR_LEN], k_auth[KAUTH_LEN];
+	chunk_t str, msk;
+	int i;
+
+	/* For SIM: MK = SHA1(Identity|n*Kc|NONCE_MT|Version List|Selected Version)
+	 * For AKA: MK = SHA1(Identity|IK|CK) */
+	this->hasher->get_hash(this->hasher, id->get_encoding(id), NULL);
+	this->hasher->get_hash(this->hasher, data, mk);
+	DBG3(DBG_IKE, "MK %b", mk, HASH_SIZE_SHA1);
+
+	/* K_encr | K_auth | MSK | EMSK = prf() | prf() | prf() | prf() */
+	this->prf->set_key(this->prf, chunk_create(mk, HASH_SIZE_SHA1));
+	str = chunk_alloca(this->prf->get_block_size(this->prf) * 3);
+	for (i = 0; i < 3; i++)
+	{
+		this->prf->get_bytes(this->prf, chunk_empty, str.ptr + str.len / 3 * i);
+	}
+
+	memcpy(k_encr, str.ptr, KENCR_LEN);
+	str = chunk_skip(str, KENCR_LEN);
+	memcpy(k_auth, str.ptr, KAUTH_LEN);
+	str = chunk_skip(str, KAUTH_LEN);
+
+	this->signer->set_key(this->signer, chunk_create(k_auth, KAUTH_LEN));
+	this->crypter->set_key(this->crypter, chunk_create(k_encr, KENCR_LEN));
+
+	msk = chunk_clone(chunk_create(str.ptr, MSK_LEN));
+	DBG3(DBG_IKE, "K_encr %b\nK_auth %b\nMSK %B",
+		 k_encr, KENCR_LEN, k_auth, KAUTH_LEN, &msk);
+
+	this->derived = TRUE;
+	return msk;
+}
+
+/**
+ * Implementation of simaka_crypto_t.destroy.
+ */
+static void destroy(private_simaka_crypto_t *this)
+{
+	DESTROY_IF(this->rng);
+	DESTROY_IF(this->hasher);
+	DESTROY_IF(this->prf);
+	DESTROY_IF(this->signer);
+	DESTROY_IF(this->crypter);
+	free(this);
+}
+
+/**
+ * See header
+ */
+simaka_crypto_t *simaka_crypto_create()
+{
+	private_simaka_crypto_t *this = malloc_thing(private_simaka_crypto_t);
+
+	this->public.get_signer = (signer_t*(*)(simaka_crypto_t*))get_signer;
+	this->public.get_crypter = (crypter_t*(*)(simaka_crypto_t*))get_crypter;
+	this->public.get_rng = (rng_t*(*)(simaka_crypto_t*))get_rng;
+	this->public.derive_keys_full = (chunk_t(*)(simaka_crypto_t*, identification_t *id, chunk_t data))derive_keys_full;
+	this->public.destroy = (void(*)(simaka_crypto_t*))destroy;
+
+	this->derived = FALSE;
+	this->rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
+	this->hasher = lib->crypto->create_hasher(lib->crypto, HASH_SHA1);
+	this->prf = lib->crypto->create_prf(lib->crypto, PRF_FIPS_SHA1_160);
+	this->signer = lib->crypto->create_signer(lib->crypto, AUTH_HMAC_SHA1_128);
+	this->crypter = lib->crypto->create_crypter(lib->crypto, ENCR_AES_CBC, 16);
+	if (!this->rng || !this->hasher || !this->prf ||
+		!this->signer || !this->crypter)
+	{
+		DBG1(DBG_IKE, "unable to use EAP-SIM, missing algorithms");
+		destroy(this);
+		return NULL;
+	}
+	return &this->public;
+}
+

src/libsimaka/simaka_crypto.h

@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2009 Martin Willi
+ * 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 simaka_crypto simaka_crypto
+ * @{ @ingroup libsimaka
+ */
+
+#ifndef SIMAKA_CRYPTO_H_
+#define SIMAKA_CRYPTO_H_
+
+#include <library.h>
+
+typedef struct simaka_crypto_t simaka_crypto_t;
+
+/**
+ * EAP-SIM/AKA crypto helper and key derivation class.
+ */
+struct simaka_crypto_t {
+
+	/**
+	 * Get the signer to use for AT_MAC calculation/verification.
+	 *
+	 * @return		signer reference, NULL if no keys have been derived
+	 */
+	signer_t* (*get_signer)(simaka_crypto_t *this);
+
+	/**
+	 * Get the signer to use for AT_ENCR_DATA encryption/decryption.
+	 *
+	 * @return		crypter reference, NULL if no keys have been derived
+	 */
+	crypter_t* (*get_crypter)(simaka_crypto_t *this);
+
+	/**
+	 * Get the random number generator.
+	 *
+	 * @return		rng reference
+	 */
+	rng_t* (*get_rng)(simaka_crypto_t *this);
+
+	/**
+	 * Derive keys after full authentication.
+	 *
+	 * This methods derives the k_encr/k_auth keys and loads them into the
+	 * internal crypter/signer instances. The passed data is method specific:
+	 * For EAP-SIM, it is "n*Kc|NONCE_MT|Version List|Selected Version", for
+	 * EAP-AKA it is "IK|CK".
+	 *
+	 * @param id	peer identity
+	 * @param data	method specific data
+	 * @return		allocated MSK value
+	 */
+	chunk_t (*derive_keys_full)(simaka_crypto_t *this, identification_t *id,
+								chunk_t data);
+
+	/**
+	 * Destroy a simaka_crypto_t.
+	 */
+	void (*destroy)(simaka_crypto_t *this);
+};
+
+/**
+ * Create a simaka_crypto instance.
+ *
+ * @return		EAP-SIM/AKA crypto instance, NULL if algorithms missing
+ */
+simaka_crypto_t *simaka_crypto_create();
+
+#endif /* SIMAKA_CRYPTO_ @}*/