Add a generic abstraction for GSM/3G authentication algorithms

Indiidual algorithms can be implemented as plugins.  libosmogsm itself
only provides COMP128v1 via this generic interface.

include/osmocom/crypt/Makefile.am

@@ -1,3 +1,3 @@
-osmocrypt_HEADERS = gprs_cipher.h
+osmocrypt_HEADERS = gprs_cipher.h auth.h
 
 osmocryptdir = $(includedir)/osmocom/crypt

include/osmocom/crypt/auth.h

@@ -0,0 +1,87 @@
+#ifndef _OSMOCRYPTO_AUTH_H
+#define _OSMOCRYPTO_AUTH_H
+
+#include <stdint.h>
+
+#include <osmocom/core/linuxlist.h>
+
+/*! \brief Authentication Type */
+enum osmo_sub_auth_type {
+	OSMO_AUTH_TYPE_NONE	= 0x00,
+	OSMO_AUTH_TYPE_GSM	= 0x01,
+	OSMO_AUTH_TYPE_UMTS	= 0x02,
+};
+
+/*! \brief Authentication Algorithm */
+enum osmo_auth_algo {
+	OSMO_AUTH_ALG_NONE,
+	OSMO_AUTH_ALG_COMP128v1,
+	OSMO_AUTH_ALG_COMP128v2,
+	OSMO_AUTH_ALG_COMP128v3,
+	OSMO_AUTH_ALG_XOR,
+	OSMO_AUTH_ALG_MILENAGE,
+	_OSMO_AUTH_ALG_NUM,
+};
+
+/*! \brief permanent (secret) subscriber auth data */
+struct osmo_sub_auth_data {
+	enum osmo_sub_auth_type type;
+	enum osmo_auth_algo algo;
+	union {
+		struct {
+			uint8_t opc[16];
+			uint8_t k[16];
+			uint8_t amf[2];
+			uint64_t sqn;
+		} umts;
+		struct {
+			uint8_t ki[16];
+		} gsm;
+	};
+};
+
+/* data structure describing a computed auth vector, generated by AuC */
+struct osmo_auth_vector {
+	uint8_t rand[16];
+	uint8_t autn[16];
+	uint8_t ck[16];
+	uint8_t ik[16];
+	uint8_t res[16];
+	uint8_t res_len;
+	uint8_t kc[8];
+	uint8_t sres[4];
+	uint32_t auth_types;	/*!< bitmask of OSMO_AUTH_TYPE_* */
+};
+
+/* \brief An implementation of an authentication algorithm */
+struct osmo_auth_impl {
+	struct llist_head list;
+	enum osmo_auth_algo algo;
+	const char *name;
+	unsigned int priority;
+
+	int (*gen_vec)(struct osmo_auth_vector *vec,
+			struct osmo_sub_auth_data *aud,
+			const uint8_t *_rand);
+
+	int (*gen_vec_auts)(struct osmo_auth_vector *vec,
+			    struct osmo_sub_auth_data *aud,
+			    const uint8_t *rand_auts, const uint8_t *auts,
+			    const uint8_t *_rand);
+};
+
+int osmo_auth_gen_vec(struct osmo_auth_vector *vec,
+		      struct osmo_sub_auth_data *aud, const uint8_t *_rand);
+
+int osmo_auth_gen_vec_auts(struct osmo_auth_vector *vec,
+			   struct osmo_sub_auth_data *aud,
+			   const uint8_t *rand_auts, const uint8_t *auts,
+			   const uint8_t *_rand);
+
+int osmo_auth_register(struct osmo_auth_impl *impl);
+
+int osmo_auth_load(const char *path);
+
+int osmo_auth_supported(enum osmo_auth_algo algo);
+
+#endif /* _OSMOCRYPTO_AUTH_H */

src/gsm/Makefile.am

@@ -11,7 +11,7 @@ libosmogsm_la_SOURCES = a5.c rxlev_stat.c tlv_parser.c comp128.c gsm_utils.c \
                         rsl.c gsm48.c gsm48_ie.c gsm0808.c sysinfo.c \
 			gprs_cipher_core.c gsm0480.c abis_nm.c gsm0502.c \
 			gsm0411_utils.c gsm0411_smc.c gsm0411_smr.c \
-			lapd_core.c lapdm.c
+			lapd_core.c lapdm.c auth_core.c auth_comp128v1.c
 
 libosmogsm_la_LDFLAGS = -version-info $(LIBVERSION)
 libosmogsm_la_LIBADD = $(top_builddir)/src/libosmocore.la

src/gsm/auth_comp128v1.c

@@ -0,0 +1,47 @@
+
+/* GSM/GPRS/3G authentication core infrastructure */
+
+/* (C) 2010-2011 by Harald Welte <laforge@gnumonks.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.
+ *
+ */
+
+#include <osmocom/crypt/auth.h>
+#include <osmocom/gsm/comp128.h>
+
+static int c128v1_gen_vec(struct osmo_auth_vector *vec,
+			  struct osmo_sub_auth_data *aud,
+			  const uint8_t *_rand)
+{
+	comp128(aud->gsm.ki, _rand, vec->sres, vec->kc);
+	vec->auth_types = OSMO_AUTH_TYPE_GSM;
+
+	return 0;
+}
+
+static struct osmo_auth_impl c128v1_alg = {
+	.algo = OSMO_AUTH_ALG_COMP128v1,
+	.name = "COMP128v1 (libosmogsm built-in)",
+	.priority = 1000,
+	.gen_vec = &c128v1_gen_vec,
+};
+
+static __attribute__((constructor)) void on_dso_load_c128(void)
+{
+	osmo_auth_register(&c128v1_alg);
+}

src/gsm/auth_core.c

@@ -0,0 +1,93 @@
+/* GSM/GPRS/3G authentication core infrastructure */
+
+/* (C) 2010-2011 by Harald Welte <laforge@gnumonks.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.
+ *
+ */
+
+#include <errno.h>
+#include <stdint.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/plugin.h>
+
+#include <osmocom/crypt/auth.h>
+
+static LLIST_HEAD(osmo_auths);
+
+static struct osmo_auth_impl *selected_auths[_OSMO_AUTH_ALG_NUM];
+
+/* register a cipher with the core */
+int osmo_auth_register(struct osmo_auth_impl *impl)
+{
+	if (impl->algo >= ARRAY_SIZE(selected_auths))
+		return -ERANGE;
+
+	llist_add_tail(&impl->list, &osmo_auths);
+
+	/* check if we want to select this implementation over others */
+	if (!selected_auths[impl->algo] ||
+	    (selected_auths[impl->algo]->priority > impl->priority))
+		selected_auths[impl->algo] = impl;
+
+	return 0;
+}
+
+/* load all available GPRS cipher plugins */
+int osmo_auth_load(const char *path)
+{
+	/* load all plugins available from path */
+	return osmo_plugin_load_all(path);
+}
+
+int osmo_auth_supported(enum osmo_auth_algo algo)
+{
+	if (algo >= ARRAY_SIZE(selected_auths))
+		return -ERANGE;
+
+	if (selected_auths[algo])
+		return 1;
+
+	return 0;
+}
+
+int osmo_auth_gen_vec(struct osmo_auth_vector *vec,
+		      struct osmo_sub_auth_data *aud,
+		      const uint8_t *_rand)
+{
+	struct osmo_auth_impl *impl = selected_auths[aud->type];
+
+	if (!impl)
+		return -ENOENT;
+
+	return impl->gen_vec(vec, aud, _rand);
+}
+
+int osmo_auth_gen_vec_auts(struct osmo_auth_vector *vec,
+			   struct osmo_sub_auth_data *aud,
+			   const uint8_t *rand_auts, const uint8_t *auts,
+			   const uint8_t *_rand)
+{
+	struct osmo_auth_impl *impl = selected_auths[aud->type];
+
+	if (!impl || !impl->gen_vec_auts)
+		return -ENOENT;
+
+	return impl->gen_vec_auts(vec, aud, rand_auts, auts, _rand);
+}