Add new kitchen sink openbsc/utils.h and libcommon/utils.c to make three so far static functions public (so I can use them in the upcoming OAP code). A place to put them could have been the gprs_utils.h, but all general functions in there have a gprs_ prefix, and todo markings to move them away. All other libcommon headers are too specific, so I opened up this kitchen sink header. Apply the change in Makefiles and C files. --- openbsc/include/openbsc/Makefile.am | 2 +- openbsc/include/openbsc/utils.h | 17 ++++++++++ openbsc/src/gprs/gprs_gsup_messages.c | 30 +--------------- openbsc/src/libcommon/Makefile.am | 2 +- openbsc/src/libcommon/utils.c | 64 +++++++++++++++++++++++++++++++++++ openbsc/src/osmo-bsc_nat/bsc_nat.c | 12 +------ openbsc/tests/gprs/Makefile.am | 3 +- 7 files changed, 87 insertions(+), 43 deletions(-) create mode 100644 openbsc/include/openbsc/utils.h create mode 100644 openbsc/src/libcommon/utils.c diff --git a/openbsc/include/openbsc/Makefile.am b/openbsc/include/openbsc/Makefile.am index 254f43d..828f5bd 100644 --- a/openbsc/include/openbsc/Makefile.am +++ b/openbsc/include/openbsc/Makefile.am @@ -14,7 +14,7 @@ noinst_HEADERS = abis_nm.h abis_rsl.h db.h gsm_04_08.h gsm_data.h \ osmo_msc_data.h osmo_bsc_grace.h sms_queue.h abis_om2000.h \ bss.h gsm_data_shared.h ipaccess.h mncc_int.h \ arfcn_range_encode.h nat_rewrite_trie.h bsc_nat_callstats.h \ - osmux.h mgcp_transcode.h gprs_utils.h \ + osmux.h mgcp_transcode.h gprs_utils.h utils.h \ gprs_gb_parse.h smpp.h meas_feed.h gprs_gsup_messages.h \ gprs_gsup_client.h bsc_msg_filter.h diff --git a/openbsc/include/openbsc/utils.h b/openbsc/include/openbsc/utils.h new file mode 100644 index 0000000..739b7a3 --- /dev/null +++ b/openbsc/include/openbsc/utils.h @@ -0,0 +1,17 @@ +/* OpenBSC kitchen sink */ + +#pragma once + +#include <stdint.h> +#include <stdlib.h> + +/* Compare count bytes of exp to rel. Return 0 if they are identical, 1 + * otherwise. Do not return a mismatch on the first mismatching byte, + * but always compare all bytes, regardless. The idea is that the amount of + * matching bytes cannot be inferred from the time the comparison took.*/ +int constant_time_cmp(const uint8_t *exp, const uint8_t *rel, const int count); + +uint64_t decode_big_endian(const uint8_t *data, size_t data_len); +uint8_t *encode_big_endian(uint64_t value, size_t data_len); + + diff --git a/openbsc/src/gprs/gprs_gsup_messages.c b/openbsc/src/gprs/gprs_gsup_messages.c index bdcff5f..07485f7 100644 --- a/openbsc/src/gprs/gprs_gsup_messages.c +++ b/openbsc/src/gprs/gprs_gsup_messages.c @@ -26,41 +26,13 @@ #include <openbsc/debug.h> #include <openbsc/gprs_utils.h> +#include <openbsc/utils.h> #include <osmocom/gsm/tlv.h> #include <osmocom/core/msgb.h> #include <stdint.h> - -static uint64_t decode_big_endian(const uint8_t *data, size_t data_len) -{ - uint64_t value = 0; - - while (data_len > 0) { - value = (value << 8) + *data; - data += 1; - data_len -= 1; - } - - return value; -} - -static uint8_t *encode_big_endian(uint64_t value, size_t data_len) -{ - static uint8_t buf[sizeof(uint64_t)]; - int idx; - - OSMO_ASSERT(data_len <= ARRAY_SIZE(buf)); - - for (idx = data_len - 1; idx >= 0; idx--) { - buf[idx] = (uint8_t)value; - value = value >> 8; - } - - return buf; -} - static int decode_pdp_info(uint8_t *data, size_t data_len, struct gprs_gsup_pdp_info *pdp_info) { diff --git a/openbsc/src/libcommon/Makefile.am b/openbsc/src/libcommon/Makefile.am index 75f40ee..84c7544 100644 --- a/openbsc/src/libcommon/Makefile.am +++ b/openbsc/src/libcommon/Makefile.am @@ -6,4 +6,4 @@ noinst_LIBRARIES = libcommon.a libcommon_a_SOURCES = bsc_version.c common_vty.c debug.c gsm_data.c \ gsm_data_shared.c socket.c talloc_ctx.c \ - gsm_subscriber_base.c + gsm_subscriber_base.c utils.c diff --git a/openbsc/src/libcommon/utils.c b/openbsc/src/libcommon/utils.c new file mode 100644 index 0000000..615eba9 --- /dev/null +++ b/openbsc/src/libcommon/utils.c @@ -0,0 +1,64 @@ +/* OpenBSC kitchen sink */ + +/* (C) 2015 by sysmocom s.m.f.c &lt;info(a)sysmocom.de&gt; + * All Rights Reserved + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License as published by + * the Free Software Foundation; either version 3 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 Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + */ + +#include <openbsc/utils.h> +#include <osmocom/core/utils.h> + +/* Wishful thinking to generate a constant time compare */ +int constant_time_cmp(const uint8_t *exp, const uint8_t *rel, const int count) +{ + int x = 0, i; + + for (i = 0; i < count; ++i) + x |= exp[i] ^ rel[i]; + + /* if x is zero, all data was identical */ + return x? 1 : 0; +} + + +uint64_t decode_big_endian(const uint8_t *data, size_t data_len) +{ + uint64_t value = 0; + + while (data_len > 0) { + value = (value << 8) + *data; + data += 1; + data_len -= 1; + } + + return value; +} + +uint8_t *encode_big_endian(uint64_t value, size_t data_len) +{ + static uint8_t buf[sizeof(uint64_t)]; + int idx; + + OSMO_ASSERT(data_len <= ARRAY_SIZE(buf)); + + for (idx = data_len - 1; idx >= 0; idx--) { + buf[idx] = (uint8_t)value; + value = value >> 8; + } + + return buf; +} + diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat.c b/openbsc/src/osmo-bsc_nat/bsc_nat.c index 56c6286..18343dd 100644 --- a/openbsc/src/osmo-bsc_nat/bsc_nat.c +++ b/openbsc/src/osmo-bsc_nat/bsc_nat.c @@ -47,6 +47,7 @@ #include <openbsc/abis_nm.h> #include <openbsc/socket.h> #include <openbsc/vty.h> +#include <openbsc/utils.h> #include <osmocom/ctrl/control_cmd.h> #include <osmocom/ctrl/control_if.h> @@ -987,17 +988,6 @@ static void ipaccess_close_bsc(void *data) bsc_close_connection(conn); } -/* Wishful thinking to generate a constant time compare */ -static int constant_time_cmp(const uint8_t *exp, const uint8_t *rel, const int count) -{ - int x = 0, i; - - for (i = 0; i < count; ++i) - x |= exp[i] ^ rel[i]; - - return x != 0; -} - static int verify_key(struct bsc_connection *conn, struct bsc_config *conf, const uint8_t *key, const int keylen) { struct osmo_auth_vector vec; diff --git a/openbsc/tests/gprs/Makefile.am b/openbsc/tests/gprs/Makefile.am index 633c362..b57977b 100644 --- a/openbsc/tests/gprs/Makefile.am +++ b/openbsc/tests/gprs/Makefile.am @@ -6,6 +6,7 @@ EXTRA_DIST = gprs_test.ok noinst_PROGRAMS = gprs_test gprs_test_SOURCES = gprs_test.c $(top_srcdir)/src/gprs/gprs_utils.c \ - $(top_srcdir)/src/gprs/gprs_gsup_messages.c + $(top_srcdir)/src/gprs/gprs_gsup_messages.c \ + $(top_srcdir)/src/libcommon/utils.c gprs_test_LDADD = $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) -- 2.1.4

Move IPA header composition and sending to new static gsup_client_send() (so I can use it in the upcoming OAP code). Sponsored-by: On-Waves ehf --- openbsc/src/gprs/gprs_gsup_client.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/openbsc/src/gprs/gprs_gsup_client.c b/openbsc/src/gprs/gprs_gsup_client.c index 807b0c1..1f9e34c 100644 --- a/openbsc/src/gprs/gprs_gsup_client.c +++ b/openbsc/src/gprs/gprs_gsup_client.c @@ -100,6 +100,14 @@ static void connect_timer_cb(void *gsupc_) gsup_client_connect(gsupc); } +static void gsup_client_send(struct gprs_gsup_client *gsupc, int proto_ext, struct msgb *msg_tx) +{ + ipa_prepend_header_ext(msg_tx, proto_ext); + ipa_msg_push_header(msg_tx, IPAC_PROTO_OSMO); + ipa_client_conn_send(gsupc->link, msg_tx); + /* msg_tx is now queued and will be freed. */ +} + static void gsup_client_updown_cb(struct ipa_client_conn *link, int up) { struct gprs_gsup_client *gsupc = link->data; @@ -275,9 +283,7 @@ int gprs_gsup_client_send(struct gprs_gsup_client *gsupc, struct msgb *msg) return -EAGAIN; } - ipa_prepend_header_ext(msg, IPAC_PROTO_EXT_GSUP); - ipa_msg_push_header(msg, IPAC_PROTO_OSMO); - ipa_client_conn_send(gsupc->link, msg); + gsup_client_send(gsupc, IPAC_PROTO_EXT_GSUP, msg); return 0; } -- 2.1.4

Sponsored-by: On-Waves ehf --- openbsc/doc/osmocom-authn-protocol.txt | 250 +++++++++++++++++++++++++++++++++ 1 file changed, 250 insertions(+) create mode 100644 openbsc/doc/osmocom-authn-protocol.txt diff --git a/openbsc/doc/osmocom-authn-protocol.txt b/openbsc/doc/osmocom-authn-protocol.txt new file mode 100644 index 0000000..1b6794e --- /dev/null +++ b/openbsc/doc/osmocom-authn-protocol.txt @@ -0,0 +1,250 @@ + + Osmocom Authentication Protocol (OAP) + +1. General + +The Osmocom Authentication Protocol employs mutual authentication to register a +client with a server over an IPA connection. Milenage is used as the +authentication algorithm, where client and server have a shared secret. + +For example, an SGSN, as OAP client, may use its SGSN ID to register with a MAP +proxy, an OAP server. + +1.1. Connection + +The protocol expects that a reliable, ordered, packet boundaries preserving +connection is used (e.g. IPA over TCP). + +1.2. Using IPA + +By default, the following identifiers should be used: + - IPA protocol: 0xee (OSMO) + - IPA OSMO protocol extension: 0x06 (OAP) + +2. Procedures + +Ideal communication sequence: + + Client Server + | | + | Register (ID) | + |----------------------------------->| + | | + | Challenge (RAND+AUTN) | + |<-----------------------------------| + | | + | Challenge Result (XRES) | + |----------------------------------->| + | | + | Register Result | + |<-----------------------------------| + +Variation "test setup": + + Client Server + | | + | Register (ID) | + |----------------------------------->| + | | + | Register Result | + |<-----------------------------------| + +Variation "invalid sequence nr": + + Client Server + | | + | Register (ID) | + |----------------------------------->| + | | + | Challenge (RAND+AUTN) | + |<-----------------------------------| + | | + | Sync Request (AUTS) | + |----------------------------------->| + | | + | Challenge (RAND'+AUTN') | + |<-----------------------------------| + | | + | Challenge Result (XRES) | + |----------------------------------->| + | | + | Register Result | + |<-----------------------------------| + +2.1. Register + +The client sends a REGISTER_REQ message containing an identifier number. + +2.2. Challenge + +The OAP server (optionally) sends back a CHALLENGE_REQ, containing random bytes +and a milenage authentication token generated from these random bytes, using a +shared secret, to authenticate itself to the OAP client. The server may omit +this challenge entirely, based on its configuration, and immediately reply with +a Register Result response. If the client cannot be registered (e.g. id is +invalid), the server sends a REGISTER_ERR response. + +2.3. Challenge Result + +When the client has received a Challenge, it may verify the server's +authenticity and validity of the sequence number (included in AUTN), and, if +valid, reply with a CHALLENGE_RES message. This shall contain an XRES +authentication token generated by milenage from the same random bytes received +from the server and the same shared secet. If the client decides to cancel the +registration (e.g. invalid AUTN), it shall not reply to the CHALLENGE_REQ; a +CHALLENGE_ERR message may be sent, but is not mandatory. For example, the +client may directly start with a new REGISTER_REQ message. + +2.4. Sync Request + +When the client has received a Challenge but sees an invalid sequence number +(embedded in AUTN, according to the milenage algorithm), the client may send a +SYNC_REQ message containing an AUTS synchronisation token. + +2.5. Sync Result + +If the server has received a valid Sync Request, it shall answer by directly +sending another Challenge (see 2.2.). If an invalid Sync Request is received, +the server shall reply with a REGISTER_ERR message. + +2.6. Register Result + +The server sends a REGISTER_RES message to indicate that registration has been +successful. If the server cannot register the client (e.g. invalid challenge +response), it shall send a REGISTER_ERR message. + +3. Message Format + +3.1. General + +Every message is based on the following message format + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + +The receiver shall be able to receive IEs in any order. Unknown IEs shall be +ignored. + +3.2.1. Register Request + +Client -> Server + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + 30 Client ID big endian int (2 oct) M TLV 4 + +3.2.2. Register Error + +Server -> Client + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + 02 Cause GMM cause, M TLV 3 + 04.08: 10.5.5.14 + +3.2.6. Register Result + +Server -> Client + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + +3.2.3. Challenge + +Server -> Client + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + 20 RAND octet string (16) M TLV 18 + 23 AUTN octet string (16) M TLV 18 + +3.2.4. Challenge Error + +Client -> Server + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + 02 Cause GMM cause, M TLV 3 + 04.08: 10.5.5.14 + +3.2.5. Challenge Result + +Client -> Server + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + 21 XRES octet string (8) M TLV 10 + +3.2.3. Sync Request + +Client -> Server + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + 20 AUTS octet string (16) M TLV 18 + +3.2.4. Sync Error + +Server -> Client + + IEI Info Element Type Pres. Format Length + Message type 4.2.1 M V 1 + 02 Cause GMM cause, M TLV 3 + 04.08: 10.5.5.14 + +4. Information Elements + +4.1. General + +[...] + +4.2.1. Message Type + + +---------------------------------------------------+ + | 8 7 6 5 4 3 2 1 | + | | + | 0 0 0 0 0 1 0 0 - Register Request | + | 0 0 0 0 0 1 0 1 - Register Error | + | 0 0 0 0 0 1 1 0 - Register Result | + | | + | 0 0 0 0 1 0 0 0 - Challenge Request | + | 0 0 0 0 1 0 0 1 - Challenge Error | + | 0 0 0 0 1 0 1 0 - Challenge Result | + | | + | 0 0 0 0 1 1 0 0 - Sync Request | + | 0 0 0 0 1 1 0 1 - Sync Error (not used) | + | 0 0 0 0 1 1 1 0 - Sync Result (not used) | + | | + +---------------------------------------------------+ + +4.2.2. IE Identifier (informational) + +These are the standard values for the IEI. + + +---------------------------------------------------------+ + | IEI Info Element Type | + | | + | 0x02 Cause GMM cause, 04.08: 10.5.5.14 | + | 0x20 RAND octet string | + | 0x23 AUTN octet string | + | 0x24 XRES octet string | + | 0x25 AUTS octet string | + | 0x30 Client ID big endian int (2 octets) | + +---------------------------------------------------------+ + +4.2.3. Client ID + + 8 7 6 5 4 3 2 1 + +-----------------------------------------------------+ + | | Client ID IEI | octet 1 + +-----------------------------------------------------+ + | Length of Client ID IE contents (2) | octet 2 + +-----------------------------------------------------+ + | Client ID number, most significant byte | octet 3 + +-----------------------------------------------------+ + | Client ID number, least significant byte | octet 4 + +-----------------------------------------------------+ + +The Client ID number shall be interpreted as an unsigned 16bit integer, where 0 +indicates an invalid / unset ID. + -- 2.1.4

Add oap.[hc] and oap_messages.[hc]. Sponsored-by: On-Waves ehf --- openbsc/include/openbsc/Makefile.am | 3 +- openbsc/include/openbsc/oap.h | 77 ++++++++++ openbsc/include/openbsc/oap_messages.h | 70 +++++++++ openbsc/src/gprs/Makefile.am | 3 +- openbsc/src/gprs/oap.c | 254 +++++++++++++++++++++++++++++++++ openbsc/src/gprs/oap_messages.c | 178 +++++++++++++++++++++++ 6 files changed, 583 insertions(+), 2 deletions(-) create mode 100644 openbsc/include/openbsc/oap.h create mode 100644 openbsc/include/openbsc/oap_messages.h create mode 100644 openbsc/src/gprs/oap.c create mode 100644 openbsc/src/gprs/oap_messages.c diff --git a/openbsc/include/openbsc/Makefile.am b/openbsc/include/openbsc/Makefile.am index 828f5bd..8a074c2 100644 --- a/openbsc/include/openbsc/Makefile.am +++ b/openbsc/include/openbsc/Makefile.am @@ -16,7 +16,8 @@ noinst_HEADERS = abis_nm.h abis_rsl.h db.h gsm_04_08.h gsm_data.h \ arfcn_range_encode.h nat_rewrite_trie.h bsc_nat_callstats.h \ osmux.h mgcp_transcode.h gprs_utils.h utils.h \ gprs_gb_parse.h smpp.h meas_feed.h gprs_gsup_messages.h \ - gprs_gsup_client.h bsc_msg_filter.h + gprs_gsup_client.h bsc_msg_filter.h \ + oap.h oap_messages.h openbsc_HEADERS = gsm_04_08.h meas_rep.h bsc_api.h openbscdir = $(includedir)/openbsc diff --git a/openbsc/include/openbsc/oap.h b/openbsc/include/openbsc/oap.h new file mode 100644 index 0000000..d106118 --- /dev/null +++ b/openbsc/include/openbsc/oap.h @@ -0,0 +1,77 @@ +/* Osmocom Authentication Protocol API */ + +/* (C) 2015 by Sysmocom s.f.m.c. GmbH + * All Rights Reserved + * + * Author: Neels Hofmeyr + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License as published by + * the Free Software Foundation; either version 3 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 Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + */ + +#pragma once + +#include <stdint.h> + +struct msgb; +struct oap_message; + +/* This is the config part for vty. It is essentially copied in oap_state, + * where values are copied over once the config is considered valid. */ +struct oap_config { + uint16_t client_id; + int secret_k_present; + uint8_t secret_k[16]; + int secret_opc_present; + uint8_t secret_opc[16]; +}; + +/* The runtime state of the OAP client. client_id and the secrets are in fact + * duplicated from oap_config, so that a separate validation of the config data + * is possible, and so that only a struct oap_state* is passed around. */ +struct oap_state { + enum { + OAP_UNINITIALIZED = 0, // just allocated. + OAP_DISABLED, // disabled by config. + OAP_INITIALIZED, // shared_secret valid. + OAP_REQUESTED_CHALLENGE, + OAP_SENT_CHALLENGE_RESULT, + OAP_REGISTERED + } state; + uint16_t client_id; + uint8_t secret_k[16]; + uint8_t secret_opc[16]; + int registration_failures; +}; + +/* From config, initialize state. Return 0 on success. */ +int oap_init(struct oap_config *config, struct oap_state *state); + +/* Construct an OAP registration message and return in *msg_tx. Use + * state->client_id and update state->state. + * Return 0 on success, or a negative value on error. + * If an error is returned, *msg_tx is guaranteed to be NULL. */ +int oap_register(struct oap_state *state, struct msgb **msg_tx); + +/* Decode and act on a received OAP message msg_rx. Update state->state. If a + * non-NULL pointer is returned in *msg_tx, that msgb should be sent to the OAP + * server (and freed) by the caller. The received msg_rx is not freed. + * Return 0 on success, or a negative value on error. + * If an error is returned, *msg_tx is guaranteed to be NULL. */ +int oap_handle(struct oap_state *state, const struct msgb *msg_rx, struct msgb **msg_tx); + +/* Allocate a msgb and in it, return the encoded oap_msg. Return NULL on + * error. (Like oap_encode(), but also allocates a msgb.) */ +struct msgb *oap_encoded(const struct oap_message *oap_msg); + diff --git a/openbsc/include/openbsc/oap_messages.h b/openbsc/include/openbsc/oap_messages.h new file mode 100644 index 0000000..a7a254c --- /dev/null +++ b/openbsc/include/openbsc/oap_messages.h @@ -0,0 +1,70 @@ +/* Osmocom Authentication Protocol message encoder/decoder */ + +/* (C) 2015 by Sysmocom s.f.m.c. GmbH + * All Rights Reserved + * + * Author: Neels Hofmeyr + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License as published by + * the Free Software Foundation; either version 3 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 Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + */ +#pragma once + +#include <stdint.h> +#include <openbsc/gsm_04_08_gprs.h> +#include <openbsc/gsm_data.h> + +/* Some numbers are out of sequence because (so far) they match gprs_gsup_iei. + */ +enum oap_iei { + OAP_CAUSE_IE = 0x02, + OAP_RAND_IE = 0x20, + OAP_AUTN_IE = 0x23, + OAP_XRES_IE = 0x24, + OAP_AUTS_IE = 0x25, + OAP_CLIENT_ID_IE = 0x30, +}; + +enum oap_message_type { + OAP_MSGT_REGISTER_REQUEST = 0b00000100, + OAP_MSGT_REGISTER_ERROR = 0b00000101, + OAP_MSGT_REGISTER_RESULT = 0b00000110, + + OAP_MSGT_CHALLENGE_REQUEST = 0b00001000, + OAP_MSGT_CHALLENGE_ERROR = 0b00001001, + OAP_MSGT_CHALLENGE_RESULT = 0b00001010, + + OAP_MSGT_SYNC_REQUEST = 0b00001100, + OAP_MSGT_SYNC_ERROR = 0b00001101, + OAP_MSGT_SYNC_RESULT = 0b00001110, +}; + +struct oap_message { + enum oap_message_type message_type; + enum gsm48_gmm_cause cause; + uint16_t client_id; + int rand_present; + uint8_t rand[16]; + int autn_present; + uint8_t autn[16]; + int xres_present; + uint8_t xres[8]; + int auts_present; + uint8_t auts[16]; +}; + +int oap_decode(const uint8_t *data, size_t data_len, + struct oap_message *oap_msg); +void oap_encode(struct msgb *msg, const struct oap_message *oap_msg); + diff --git a/openbsc/src/gprs/Makefile.am b/openbsc/src/gprs/Makefile.am index f46a402..0952d41 100644 --- a/openbsc/src/gprs/Makefile.am +++ b/openbsc/src/gprs/Makefile.am @@ -27,7 +27,8 @@ osmo_sgsn_SOURCES = gprs_gmm.c gprs_sgsn.c gprs_sndcp.c gprs_sndcp_vty.c \ gprs_llc.c gprs_llc_parse.c gprs_llc_vty.c crc24.c \ sgsn_ctrl.c sgsn_auth.c gprs_subscriber.c \ gprs_gsup_messages.c gprs_utils.c gprs_gsup_client.c \ - gsm_04_08_gprs.c sgsn_cdr.c sgsn_ares.c + gsm_04_08_gprs.c sgsn_cdr.c sgsn_ares.c \ + oap.c oap_messages.c osmo_sgsn_LDADD = \ $(top_builddir)/src/libcommon/libcommon.a \ -lgtp $(OSMO_LIBS) $(LIBOSMOABIS_LIBS) $(LIBCARES_LIBS) -lrt diff --git a/openbsc/src/gprs/oap.c b/openbsc/src/gprs/oap.c new file mode 100644 index 0000000..2c17d04 --- /dev/null +++ b/openbsc/src/gprs/oap.c @@ -0,0 +1,254 @@ +/* Osmocom Authentication Protocol API */ + +/* (C) 2015 by Sysmocom s.f.m.c. GmbH + * All Rights Reserved + * + * Author: Neels Hofmeyr + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License as published by + * the Free Software Foundation; either version 3 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 Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + */ + +#include <osmocom/crypt/auth.h> + +#include <openbsc/oap.h> +#include <openbsc/utils.h> +#include <openbsc/debug.h> +#include <openbsc/oap_messages.h> + +int oap_init(struct oap_config *config, struct oap_state *state) +{ + OSMO_ASSERT(state->state == OAP_UNINITIALIZED); + + if (config->client_id == 0) + goto disable; + + if (config->secret_k_present == 0) { + LOGP(DGPRS, LOGL_NOTICE, "OAP: client ID set, but secret K missing.\n"); + goto disable; + } + + if (config->secret_opc_present == 0) { + LOGP(DGPRS, LOGL_NOTICE, "OAP: client ID set, but secret OPC missing.\n"); + goto disable; + } + + state->client_id = config->client_id; + memcpy(state->secret_k, config->secret_k, sizeof(state->secret_k)); + memcpy(state->secret_opc, config->secret_opc, sizeof(state->secret_opc)); + state->state = OAP_INITIALIZED; + return 0; + +disable: + state->state = OAP_DISABLED; + return 0; +} + +/* From the given state and received RAND and AUTN octets, validate the + * server's authenticity and formulate the matching milenage reply octets in + * *tx_xres. The state is not modified. + * On success, and if tx_res is not NULL, exactly 8 octets will be written to + * *tx_res. If not NULL, tx_res must point at allocated memory of at least 8 + * octets. The caller will want to send XRES back to the server in a challenge + * response message and update the state. + * Return 0 on success; -1 if OAP is disabled; -2 if rx_random and rx_autn fail + * the authentication check; -3 for any other errors. */ +static int oap_evaluate_challenge(const struct oap_state *state, + const uint8_t *rx_random, + const uint8_t *rx_autn, + uint8_t *tx_xres) +{ + switch(state->state) { + case OAP_UNINITIALIZED: + case OAP_DISABLED: + return -1; + default: + break; + } + + struct osmo_auth_vector vec; + + struct osmo_sub_auth_data auth = { + .type = OSMO_AUTH_TYPE_UMTS, + .algo = OSMO_AUTH_ALG_MILENAGE, + }; + + OSMO_ASSERT(sizeof(auth.u.umts.k) == sizeof(state->secret_k)); + OSMO_ASSERT(sizeof(auth.u.umts.opc) == sizeof(state->secret_opc)); + + memcpy(auth.u.umts.k, state->secret_k, sizeof(auth.u.umts.k)); + memcpy(auth.u.umts.opc, state->secret_opc, sizeof(auth.u.umts.opc)); + memset(auth.u.umts.amf, 0, 2); + auth.u.umts.sqn = 42; /* TODO */ + + memset(&vec, 0, sizeof(vec)); + osmo_auth_gen_vec(&vec, &auth, rx_random); + + if (vec.res_len != 8) { + LOGP(DGPRS, LOGL_ERROR, "OAP: Expected XRES to be 8 octets, got %d\n", + vec.res_len); + return -3; + } + + if (constant_time_cmp(vec.autn, rx_autn, sizeof(vec.autn)) != 0) { + LOGP(DGPRS, LOGL_ERROR, "OAP: AUTN mismatch!\n"); + LOGP(DGPRS, LOGL_INFO, "OAP: AUTN from server: %s\n", + osmo_hexdump_nospc(rx_autn, sizeof(vec.autn))); + LOGP(DGPRS, LOGL_INFO, "OAP: AUTN expected: %s\n", + osmo_hexdump_nospc(vec.autn, sizeof(vec.autn))); + return -2; + } + + if (tx_xres != NULL) + memcpy(tx_xres, vec.res, 8); + return 0; +} + +struct msgb *oap_encoded(const struct oap_message *oap_msg) +{ + struct msgb *msg = msgb_alloc_headroom(1000, 64, __func__); + OSMO_ASSERT(msg); + oap_encode(msg, oap_msg); + return msg; +} + +/* Create a new msgb containing an OAP registration message. + * On error, return NULL. */ +static struct msgb* oap_msg_register(uint16_t client_id) +{ + if (client_id < 1) { + LOGP(DGPRS, LOGL_ERROR, "OAP: Invalid client ID: %d\n", client_id); + return NULL; + } + + struct oap_message oap_msg = {0}; + oap_msg.message_type = OAP_MSGT_REGISTER_REQUEST; + oap_msg.client_id = client_id; + return oap_encoded(&oap_msg); +} + +int oap_register(struct oap_state *state, struct msgb **msg_tx) +{ + *msg_tx = oap_msg_register(state->client_id); + if (!(*msg_tx)) + return -1; + + state->state = OAP_REQUESTED_CHALLENGE; + return 0; +} + +/* Create a new msgb containing an OAP challenge response message. + * xres must point at 8 octets to return as challenge response. + * On error, return NULL. */ +static struct msgb* oap_msg_challenge_response(uint8_t *xres) +{ + struct oap_message oap_reply = {0}; + + oap_reply.message_type = OAP_MSGT_CHALLENGE_RESULT; + memcpy(oap_reply.xres, xres, sizeof(oap_reply.xres)); + oap_reply.xres_present = 1; + return oap_encoded(&oap_reply); +} + +static int handle_challenge(struct oap_state *state, + struct oap_message *oap_rx, + struct msgb **msg_tx) +{ + int rc; + if (!(oap_rx->rand_present && oap_rx->autn_present)) { + LOGP(DGPRS, LOGL_ERROR, + "OAP challenge incomplete (rand_present: %d, autn_present: %d)\n", + oap_rx->rand_present, oap_rx->autn_present); + rc = -2; + goto failure; + } + + uint8_t xres[8]; + rc = oap_evaluate_challenge(state, + oap_rx->rand, + oap_rx->autn, + xres); + if (rc < 0) + goto failure; + + *msg_tx = oap_msg_challenge_response(xres); + if ((*msg_tx) == NULL) { + rc = -1; + goto failure; + } + + state->state = OAP_SENT_CHALLENGE_RESULT; + return 0; + +failure: + OSMO_ASSERT(rc < 0); + state->state = OAP_INITIALIZED; + return rc; +} + +int oap_handle(struct oap_state *state, const struct msgb *msg_rx, struct msgb **msg_tx) +{ + *msg_tx = NULL; + + uint8_t *data = msgb_l2(msg_rx); + size_t data_len = msgb_l2len(msg_rx); + int rc = 0; + + struct oap_message oap_msg = {0}; + + OSMO_ASSERT(data); + + rc = oap_decode(data, data_len, &oap_msg); + if (rc < 0) { + LOGP(DGPRS, LOGL_ERROR, + "Decoding OAP message failed with error '%s' (%d)\n", + get_value_string(gsm48_gmm_cause_names, -rc), -rc); + return -10; + } + + switch (oap_msg.message_type) { + case OAP_MSGT_CHALLENGE_REQUEST: + return handle_challenge(state, &oap_msg, msg_tx); + + case OAP_MSGT_REGISTER_RESULT: + // successfully registered! + state->state = OAP_REGISTERED; + break; + + case OAP_MSGT_REGISTER_ERROR: + LOGP(DGPRS, LOGL_ERROR, + "OAP registration failed\n"); + state->state = OAP_INITIALIZED; + if (state->registration_failures < 3) { + state->registration_failures ++; + return oap_register(state, msg_tx); + } + return -11; + + case OAP_MSGT_REGISTER_REQUEST: + case OAP_MSGT_CHALLENGE_RESULT: + LOGP(DGPRS, LOGL_ERROR, + "Received invalid OAP message type for OAP client side: %d\n", + (int)oap_msg.message_type); + return -12; + + default: + LOGP(DGPRS, LOGL_ERROR, + "Unknown OAP message type: %d\n", + (int)oap_msg.message_type); + return -13; + } + + return 0; +} diff --git a/openbsc/src/gprs/oap_messages.c b/openbsc/src/gprs/oap_messages.c new file mode 100644 index 0000000..eb52053 --- /dev/null +++ b/openbsc/src/gprs/oap_messages.c @@ -0,0 +1,178 @@ +/* Osmocom Authentication Protocol message encoder/decoder */ + +/* (C) 2015 by Sysmocom s.f.m.c. GmbH + * All Rights Reserved + * + * Author: Neels Hofmeyr + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License as published by + * the Free Software Foundation; either version 3 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 Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + */ + +#include <openbsc/oap_messages.h> + +#include <openbsc/debug.h> +#include <openbsc/gprs_utils.h> +#include <openbsc/utils.h> + +#include <osmocom/gsm/tlv.h> +#include <osmocom/core/msgb.h> + +#include <stdint.h> + + +int oap_decode(const uint8_t *const_data, size_t data_len, + struct oap_message *oap_msg) +{ + int rc; + uint8_t tag; + /* the shift/match functions expect non-const pointers, but we'll + * either copy the data or cast pointers back to const before returning + * them + */ + uint8_t *data = (uint8_t *)const_data; + uint8_t *value; + size_t value_len; + + memset(oap_msg, 0, sizeof(*oap_msg)); + + /* message type */ + rc = gprs_shift_v_fixed(&data, &data_len, 1, &value); + if (rc < 0) + return -GMM_CAUSE_INV_MAND_INFO; + oap_msg->message_type = decode_big_endian(value, 1); + + /* specific parts */ + while (data_len > 0) { + enum oap_iei iei; + + rc = gprs_shift_tlv(&data, &data_len, &tag, &value, &value_len); + if (rc < 0) + return -GMM_CAUSE_PROTO_ERR_UNSPEC; + + iei = tag; + + switch (iei) { + case OAP_CLIENT_ID_IE: + if (value_len != 2) { + LOGP(DGPRS, LOGL_NOTICE, + "OAP IE type client ID (%d) should be 2 octets, but has %d\n", + (int)iei, (int)value_len); + return -GMM_CAUSE_PROTO_ERR_UNSPEC; + } + + oap_msg->client_id = decode_big_endian(value, value_len); + + if (oap_msg->client_id == 0) { + LOGP(DGPRS, LOGL_NOTICE, + "OAP IE type client ID (%d): client ID must be nonzero.\n", + (int)iei); + return -GMM_CAUSE_PROTO_ERR_UNSPEC; + } + break; + + case OAP_AUTN_IE: + if (value_len != sizeof(oap_msg->autn)) { + LOGP(DGPRS, LOGL_NOTICE, + "OAP IE type AUTN (%d) should be %d octets, but has %d\n", + (int)iei, (int)sizeof(oap_msg->autn), (int)value_len); + return -GMM_CAUSE_PROTO_ERR_UNSPEC; + } + memcpy(oap_msg->autn, value, value_len); + oap_msg->autn_present = value_len; + break; + + case OAP_RAND_IE: + if (value_len != sizeof(oap_msg->rand)) { + LOGP(DGPRS, LOGL_NOTICE, + "OAP IE type RAND (%d) should be %d octets, but has %d\n", + (int)iei, (int)sizeof(oap_msg->rand), (int)value_len); + return -GMM_CAUSE_PROTO_ERR_UNSPEC; + } + memcpy(oap_msg->rand, value, value_len); + oap_msg->rand_present = value_len; + break; + + case OAP_XRES_IE: + if (value_len != sizeof(oap_msg->xres)) { + LOGP(DGPRS, LOGL_NOTICE, + "OAP IE type XRES (%d) should be %d octets, but has %d\n", + (int)iei, (int)sizeof(oap_msg->xres), (int)value_len); + return -GMM_CAUSE_PROTO_ERR_UNSPEC; + } + memcpy(oap_msg->xres, value, value_len); + oap_msg->xres_present = value_len; + break; + + case OAP_AUTS_IE: + if (value_len != sizeof(oap_msg->auts)) { + LOGP(DGPRS, LOGL_NOTICE, + "OAP IE type AUTS (%d) should be %d octets, but has %d\n", + (int)iei, (int)sizeof(oap_msg->auts), (int)value_len); + return -GMM_CAUSE_PROTO_ERR_UNSPEC; + } + memcpy(oap_msg->auts, value, value_len); + oap_msg->auts_present = value_len; + break; + + case OAP_CAUSE_IE: + if (value_len > 1) { + LOGP(DGPRS, LOGL_ERROR, + "OAP cause may not exceed one octet, is %d", (int)value_len); + return -GMM_CAUSE_PROTO_ERR_UNSPEC; + } + oap_msg->cause = *value; + break; + + default: + LOGP(DGPRS, LOGL_NOTICE, + "OAP IE type %d unknown\n", iei); + continue; + } + } + + return 0; +} + +void oap_encode(struct msgb *msg, const struct oap_message *oap_msg) +{ + uint8_t u8; + + /* generic part */ + OSMO_ASSERT(oap_msg->message_type); + msgb_v_put(msg, (uint8_t)oap_msg->message_type); + + /* specific parts */ + if ((u8 = oap_msg->cause)) + msgb_tlv_put(msg, OAP_CAUSE_IE, sizeof(u8), &u8); + + if (oap_msg->client_id > 0) + msgb_tlv_put(msg, OAP_CLIENT_ID_IE, sizeof(oap_msg->client_id), + encode_big_endian(oap_msg->client_id, sizeof(oap_msg->client_id))); + + if (oap_msg->rand_present) + msgb_tlv_put(msg, OAP_RAND_IE, sizeof(oap_msg->rand), oap_msg->rand); + + if (oap_msg->autn_present) + msgb_tlv_put(msg, OAP_AUTN_IE, sizeof(oap_msg->autn), oap_msg->autn); + + if (oap_msg->auts_present) + msgb_tlv_put(msg, OAP_AUTS_IE, sizeof(oap_msg->auts), oap_msg->auts); + + if (oap_msg->xres_present) + msgb_tlv_put(msg, OAP_XRES_IE, sizeof(oap_msg->xres), oap_msg->xres); + + msg->l2h = msg->data; +} + -- 2.1.4

Trigger an OAP registration upon IPA connect. Feed incoming OAP messages to oap_handle() and send replies returned by it. Add oap_config to sgsn_config (todo: vty). Sponsored-by: On-Waves ehf --- openbsc/include/openbsc/gprs_gsup_client.h | 7 +++- openbsc/include/openbsc/sgsn.h | 3 ++ openbsc/src/gprs/gprs_gsup_client.c | 58 ++++++++++++++++++++++++++---- openbsc/src/gprs/gprs_subscriber.c | 3 +- openbsc/tests/sgsn/Makefile.am | 2 ++ 5 files changed, 65 insertions(+), 8 deletions(-) diff --git a/openbsc/include/openbsc/gprs_gsup_client.h b/openbsc/include/openbsc/gprs_gsup_client.h index 9537db4..ccfa388 100644 --- a/openbsc/include/openbsc/gprs_gsup_client.h +++ b/openbsc/include/openbsc/gprs_gsup_client.h @@ -23,6 +23,8 @@ #include <osmocom/core/timer.h> +#include <openbsc/oap.h> + #define GPRS_GSUP_RECONNECT_INTERVAL 10 #define GPRS_GSUP_PING_INTERVAL 20 @@ -38,6 +40,8 @@ struct gprs_gsup_client { gprs_gsup_read_cb_t read_cb; void *data; + struct oap_state oap_state; + struct osmo_timer_list ping_timer; struct osmo_timer_list connect_timer; int is_connected; @@ -46,7 +50,8 @@ struct gprs_gsup_client { struct gprs_gsup_client *gprs_gsup_client_create(const char *ip_addr, unsigned int tcp_port, - gprs_gsup_read_cb_t read_cb); + gprs_gsup_read_cb_t read_cb, + struct oap_config *oap_config); void gprs_gsup_client_destroy(struct gprs_gsup_client *gsupc); int gprs_gsup_client_send(struct gprs_gsup_client *gsupc, struct msgb *msg); diff --git a/openbsc/include/openbsc/sgsn.h b/openbsc/include/openbsc/sgsn.h index d4f9913..2b1b97c 100644 --- a/openbsc/include/openbsc/sgsn.h +++ b/openbsc/include/openbsc/sgsn.h @@ -6,6 +6,7 @@ #include <osmocom/gprs/gprs_ns.h> #include <openbsc/gprs_sgsn.h> +#include <openbsc/oap.h> #include <ares.h> @@ -61,6 +62,8 @@ struct sgsn_config { } timers; int dynamic_lookup; + + struct oap_config oap; }; struct sgsn_instance { diff --git a/openbsc/src/gprs/gprs_gsup_client.c b/openbsc/src/gprs/gprs_gsup_client.c index 1f9e34c..a332fa7 100644 --- a/openbsc/src/gprs/gprs_gsup_client.c +++ b/openbsc/src/gprs/gprs_gsup_client.c @@ -108,6 +108,20 @@ static void gsup_client_send(struct gprs_gsup_client *gsupc, int proto_ext, stru /* msg_tx is now queued and will be freed. */ } +static void gsup_client_oap_register(struct gprs_gsup_client *gsupc) +{ + struct msgb *msg_tx; + int rc; + rc = oap_register(&gsupc->oap_state, &msg_tx); + + if ((rc < 0) || (!msg_tx)) { + LOGP(DGPRS, LOGL_ERROR, "GSUP OAP set up, but cannot register.\n"); + return; + } + + gsup_client_send(gsupc, IPAC_PROTO_EXT_OAP, msg_tx); +} + static void gsup_client_updown_cb(struct ipa_client_conn *link, int up) { struct gprs_gsup_client *gsupc = link->data; @@ -120,6 +134,9 @@ static void gsup_client_updown_cb(struct ipa_client_conn *link, int up) if (up) { start_test_procedure(gsupc); + if (gsupc->oap_state.state == OAP_INITIALIZED) + gsup_client_oap_register(gsupc); + osmo_timer_del(&gsupc->connect_timer); } else { osmo_timer_del(&gsupc->ping_timer); @@ -129,6 +146,22 @@ static void gsup_client_updown_cb(struct ipa_client_conn *link, int up) } } +static int gsup_client_oap_handle(struct gprs_gsup_client *gsupc, struct msgb *msg_rx) +{ + int rc; + struct msgb *msg_tx; + + rc = oap_handle(&gsupc->oap_state, msg_rx, &msg_tx); + msgb_free(msg_rx); + if (rc < 0) + return rc; + + if (msg_tx) + gsup_client_send(gsupc, IPAC_PROTO_EXT_OAP, msg_tx); + + return 0; +} + static int gsup_client_read_cb(struct ipa_client_conn *link, struct msgb *msg) { struct ipaccess_head *hh = (struct ipaccess_head *) msg->data; @@ -168,16 +201,24 @@ static int gsup_client_read_cb(struct ipa_client_conn *link, struct msgb *msg) if (hh->proto != IPAC_PROTO_OSMO) goto invalid; - if (!he || msgb_l2len(msg) < sizeof(*he) || - he->proto != IPAC_PROTO_EXT_GSUP) + if (!he || msgb_l2len(msg) < sizeof(*he)) goto invalid; msg->l2h = &he->data[0]; - OSMO_ASSERT(gsupc->read_cb != NULL); - gsupc->read_cb(gsupc, msg); + if (he->proto == IPAC_PROTO_EXT_GSUP) { + OSMO_ASSERT(gsupc->read_cb != NULL); + gsupc->read_cb(gsupc, msg); + /* expecting read_cb() to free msg */ + } + else + if (he->proto == IPAC_PROTO_EXT_OAP) { + return gsup_client_oap_handle(gsupc, msg); + /* gsup_client_oap_handle frees msg */ + } + else + goto invalid; - /* Not freeing msg here, because that must be done by the read_cb. */ return 0; invalid: @@ -222,7 +263,8 @@ static void start_test_procedure(struct gprs_gsup_client *gsupc) struct gprs_gsup_client *gprs_gsup_client_create(const char *ip_addr, unsigned int tcp_port, - gprs_gsup_read_cb_t read_cb) + gprs_gsup_read_cb_t read_cb, + struct oap_config *oap_config) { struct gprs_gsup_client *gsupc; int rc; @@ -230,6 +272,10 @@ struct gprs_gsup_client *gprs_gsup_client_create(const char *ip_addr, gsupc = talloc_zero(tall_bsc_ctx, struct gprs_gsup_client); OSMO_ASSERT(gsupc); + rc = oap_init(oap_config, &gsupc->oap_state); + if (rc != 0) + goto failed; + gsupc->link = ipa_client_conn_create(gsupc, /* no e1inp */ NULL, 0, diff --git a/openbsc/src/gprs/gprs_subscriber.c b/openbsc/src/gprs/gprs_subscriber.c index 8231e8c..3467293 100644 --- a/openbsc/src/gprs/gprs_subscriber.c +++ b/openbsc/src/gprs/gprs_subscriber.c @@ -63,7 +63,8 @@ int gprs_subscr_init(struct sgsn_instance *sgi) sgi->gsup_client = gprs_gsup_client_create( addr_str, sgi->cfg.gsup_server_port, - &gsup_read_cb); + &gsup_read_cb, + &sgi->cfg.oap); if (!sgi->gsup_client) return -1; diff --git a/openbsc/tests/sgsn/Makefile.am b/openbsc/tests/sgsn/Makefile.am index 3c202dd..24504c2 100644 --- a/openbsc/tests/sgsn/Makefile.am +++ b/openbsc/tests/sgsn/Makefile.am @@ -28,6 +28,8 @@ sgsn_test_LDADD = \ $(top_builddir)/src/gprs/gprs_utils.o \ $(top_builddir)/src/gprs/gprs_subscriber.o \ $(top_builddir)/src/gprs/gsm_04_08_gprs.o \ + $(top_builddir)/src/gprs/oap.o \ + $(top_builddir)/src/gprs/oap_messages.o \ $(top_builddir)/src/libcommon/libcommon.a \ $(LIBOSMOABIS_LIBS) \ $(LIBOSMOCORE_LIBS) \ -- 2.1.4