import gprs_gsup_message.[ch] from openbsc as gsup.[ch]

Move those routines from OpenBSC to libosmogsm, so they can be
re-used from other programs.  I think it was a mistake to add them only
inside the openbsc repository in the first place.  We need to pay more
attention to this in the future.

10 files changed, 908 insertions, 4 deletions

diff --git a/include/Makefile.am b/include/Makefile.am
index af72bfca..2e58d7e2 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -70,6 +70,7 @@ nobase_include_HEADERS = \
                        osmocom/gsm/gsm48.h \
                        osmocom/gsm/gsm48_ie.h \
                        osmocom/gsm/gsm_utils.h \
+                       osmocom/gsm/gsup.h \
                        osmocom/gsm/ipa.h \
                        osmocom/gsm/lapd_core.h \
                        osmocom/gsm/lapdm.h \
diff --git a/include/osmocom/core/logging.h b/include/osmocom/core/logging.h
index 4b79c054..89d3f948 100644
--- a/include/osmocom/core/logging.h
+++ b/include/osmocom/core/logging.h
@@ -91,7 +91,8 @@ void logp(int subsys, const char *file, int line, int cont, const char *format,
 #define DLCTRL		-8	/*!< Control Interface */
 #define DLGTP		-9	/*!< GTP (GPRS Tunneling Protocol */
 #define DLSTATS		-10	/*!< Statistics */
-#define OSMO_NUM_DLIB	10	/*!< Number of logging sub-systems in libraries */
+#define DLGSUP		11	/*!< Generic Subscriber Update Protocol */
+#define OSMO_NUM_DLIB	11	/*!< Number of logging sub-systems in libraries */
 
 /*! Configuration of singgle log category / sub-system */
 struct log_category {
diff --git a/include/osmocom/gsm/gsup.h b/include/osmocom/gsm/gsup.h
new file mode 100644
index 00000000..d966b2d2
--- /dev/null
+++ b/include/osmocom/gsm/gsup.h
@@ -0,0 +1,139 @@
+/* Osmocom Subscriber Update Protocol message encoder/decoder */
+
+/* (C) 2014 by Sysmocom s.f.m.c. GmbH, Author: Jacob Erlbeck
+ * (C) 2016 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+#pragma once
+
+#include <stdint.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/gsm/protocol/gsm_23_003.h>
+#include <osmocom/gsm/protocol/gsm_04_08_gprs.h>
+#include <osmocom/crypt/auth.h>
+
+/*! Maximum nubmer of PDP inside \ref osmo_gsup_message */
+#define OSMO_GSUP_MAX_NUM_PDP_INFO		10 /* GSM 09.02 limits this to 50 */
+/*! Maximum number of auth info inside \ref osmo_gsup_message */
+#define OSMO_GSUP_MAX_NUM_AUTH_INFO		5
+/*! Maximum number of octets encoding MSISDN in BCD format */
+#define OSMO_GSUP_MAX_MSISDN_LEN		9
+
+#define OSMO_GSUP_PDP_TYPE_SIZE			2
+
+/*! Information Element Identifiers for GSUP IEs */
+enum osmo_gsup_iei {
+	OSMO_GSUP_IMSI_IE			= 0x01,
+	OSMO_GSUP_CAUSE_IE			= 0x02,
+	OSMO_GSUP_AUTH_TUPLE_IE			= 0x03,
+	OSMO_GSUP_PDP_INFO_COMPL_IE		= 0x04,
+	OSMO_GSUP_PDP_INFO_IE			= 0x05,
+	OSMO_GSUP_CANCEL_TYPE_IE		= 0x06,
+	OSMO_GSUP_FREEZE_PTMSI_IE		= 0x07,
+	OSMO_GSUP_MSISDN_IE			= 0x08,
+	OSMO_GSUP_HLR_NUMBER_IE			= 0x09,
+	OSMO_GSUP_PDP_CONTEXT_ID_IE		= 0x10,
+	OSMO_GSUP_PDP_TYPE_IE			= 0x11,
+	OSMO_GSUP_ACCESS_POINT_NAME_IE		= 0x12,
+	OSMO_GSUP_PDP_QOS_IE			= 0x13,
+	OSMO_GSUP_RAND_IE			= 0x20,
+	OSMO_GSUP_SRES_IE			= 0x21,
+	OSMO_GSUP_KC_IE				= 0x22,
+	/* 3G support */
+	OSMO_GSUP_IK_IE				= 0x23,
+	OSMO_GSUP_CK_IE				= 0x24,
+	OSMO_GSUP_AUTN_IE			= 0x25,
+	OSMO_GSUP_AUTS_IE			= 0x26,
+	OSMO_GSUP_RES_IE			= 0x27,
+};
+
+/*! GSUP message type */
+enum osmo_gsup_message_type {
+	OSMO_GSUP_MSGT_UPDATE_LOCATION_REQUEST	= 0b00000100,
+	OSMO_GSUP_MSGT_UPDATE_LOCATION_ERROR	= 0b00000101,
+	OSMO_GSUP_MSGT_UPDATE_LOCATION_RESULT	= 0b00000110,
+
+	OSMO_GSUP_MSGT_SEND_AUTH_INFO_REQUEST	= 0b00001000,
+	OSMO_GSUP_MSGT_SEND_AUTH_INFO_ERROR	= 0b00001001,
+	OSMO_GSUP_MSGT_SEND_AUTH_INFO_RESULT	= 0b00001010,
+
+	OSMO_GSUP_MSGT_PURGE_MS_REQUEST		= 0b00001100,
+	OSMO_GSUP_MSGT_PURGE_MS_ERROR		= 0b00001101,
+	OSMO_GSUP_MSGT_PURGE_MS_RESULT		= 0b00001110,
+
+	OSMO_GSUP_MSGT_INSERT_DATA_REQUEST	= 0b00010000,
+	OSMO_GSUP_MSGT_INSERT_DATA_ERROR	= 0b00010001,
+	OSMO_GSUP_MSGT_INSERT_DATA_RESULT	= 0b00010010,
+
+	OSMO_GSUP_MSGT_DELETE_DATA_REQUEST	= 0b00010100,
+	OSMO_GSUP_MSGT_DELETE_DATA_ERROR	= 0b00010101,
+	OSMO_GSUP_MSGT_DELETE_DATA_RESULT	= 0b00010110,
+
+	OSMO_GSUP_MSGT_LOCATION_CANCEL_REQUEST	= 0b00011100,
+	OSMO_GSUP_MSGT_LOCATION_CANCEL_ERROR	= 0b00011101,
+	OSMO_GSUP_MSGT_LOCATION_CANCEL_RESULT	= 0b00011110,
+};
+
+#define OSMO_GSUP_IS_MSGT_REQUEST(msgt) (((msgt) & 0b00000011) == 0b00)
+#define OSMO_GSUP_IS_MSGT_ERROR(msgt)   (((msgt) & 0b00000011) == 0b01)
+#define OSMO_GSUP_TO_MSGT_ERROR(msgt)   (((msgt) & 0b11111100) | 0b01)
+
+enum osmo_gsup_cancel_type {
+	OSMO_GSUP_CANCEL_TYPE_UPDATE		= 1, /* on wire: 0 */
+	OSMO_GSUP_CANCEL_TYPE_WITHDRAW		= 2, /* on wire: 1 */
+};
+
+/*! parsed/decoded PDP context information */
+struct osmo_gsup_pdp_info {
+	unsigned int			context_id;
+	int				have_info;
+	/*! Type of PDP context */
+	uint16_t			pdp_type;
+	/*! APN information, still in encoded form. Can be NULL if no
+	 * APN information included */
+	const uint8_t			*apn_enc;
+	/*! length (in octets) of apn_enc */
+	size_t				apn_enc_len;
+	/*! QoS information, still in encoded form. Can be NULL if no
+	 * QoS information included */
+	const uint8_t			*qos_enc;
+	/*! length (in octets) of qos_enc */
+	size_t				qos_enc_len;
+};
+
+/*! parsed/decoded GSUP protocol message */
+struct osmo_gsup_message {
+	enum osmo_gsup_message_type	message_type;
+	char				imsi[GSM23003_IMSI_MAX_DIGITS+2];
+	enum gsm48_gmm_cause		cause;
+	enum osmo_gsup_cancel_type	cancel_type;
+	int				pdp_info_compl;
+	int				freeze_ptmsi;
+	struct osmo_auth_vector		auth_vectors[OSMO_GSUP_MAX_NUM_AUTH_INFO];
+	size_t				num_auth_vectors;
+	struct osmo_gsup_pdp_info	pdp_infos[OSMO_GSUP_MAX_NUM_PDP_INFO];
+	size_t				num_pdp_infos;
+	const uint8_t			*msisdn_enc;
+	size_t				msisdn_enc_len;
+	const uint8_t			*hlr_enc;
+	size_t				hlr_enc_len;
+	const uint8_t			*auts;
+};
+
+int osmo_gsup_decode(const uint8_t *data, size_t data_len,
+		     struct osmo_gsup_message *gsup_msg);
+void osmo_gsup_encode(struct msgb *msg, const struct osmo_gsup_message *gsup_msg);
diff --git a/src/gsm/Makefile.am b/src/gsm/Makefile.am
index 4326b357..781f153a 100644
--- a/src/gsm/Makefile.am
+++ b/src/gsm/Makefile.am
@@ -26,7 +26,8 @@ libgsmint_la_SOURCES =  a5.c rxlev_stat.c tlv_parser.c comp128.c comp128v23.c \
 			auth_core.c auth_comp128v1.c auth_comp128v23.c \
 			auth_milenage.c milenage/aes-encblock.c \
 			milenage/aes-internal.c milenage/aes-internal-enc.c \
-			milenage/milenage.c gan.c ipa.c gsm0341.c apn.c
+			milenage/milenage.c gan.c ipa.c gsm0341.c apn.c \
+			gsup.c
 libgsmint_la_LDFLAGS = -no-undefined
 libgsmint_la_LIBADD = ../libosmocore.la
 
diff --git a/src/gsm/gsup.c b/src/gsm/gsup.c
new file mode 100644
index 00000000..7a439d48
--- /dev/null
+++ b/src/gsm/gsup.c
@@ -0,0 +1,472 @@
+/* Osmocom Subscriber Update Protocol message encoder/decoder */
+
+/*
+ * (C) 2014 by Sysmocom s.f.m.c. GmbH
+ * (C) 2015 by Holger Hans Peter Freyther
+ * (C) 2016 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * Author: Jacob Erlbeck
+ *
+ * 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/gsm/tlv.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/gsm/gsm48_ie.h>
+#include <osmocom/gsm/gsup.h>
+
+#include <stdint.h>
+
+static int decode_pdp_info(uint8_t *data, size_t data_len,
+			  struct osmo_gsup_pdp_info *pdp_info)
+{
+	int rc;
+	uint8_t tag;
+	uint8_t *value;
+	size_t value_len;
+
+	/* specific parts */
+	while (data_len > 0) {
+		enum osmo_gsup_iei iei;
+
+		rc = osmo_shift_tlv(&data, &data_len, &tag, &value, &value_len);
+		if (rc < 0)
+			return -GMM_CAUSE_PROTO_ERR_UNSPEC;
+
+		iei = tag;
+
+		switch (iei) {
+		case OSMO_GSUP_PDP_CONTEXT_ID_IE:
+			pdp_info->context_id = osmo_decode_big_endian(value, value_len);
+			break;
+
+		case OSMO_GSUP_PDP_TYPE_IE:
+			pdp_info->pdp_type =
+				osmo_decode_big_endian(value, value_len) & 0x0fff;
+			break;
+
+		case OSMO_GSUP_ACCESS_POINT_NAME_IE:
+			pdp_info->apn_enc = value;
+			pdp_info->apn_enc_len = value_len;
+			break;
+
+		case OSMO_GSUP_PDP_QOS_IE:
+			pdp_info->qos_enc = value;
+			pdp_info->qos_enc_len = value_len;
+			break;
+
+		default:
+			LOGP(DLGSUP, LOGL_ERROR,
+			     "GSUP IE type %d not expected in PDP info\n", iei);
+			continue;
+		}
+	}
+
+	return 0;
+}
+
+static int decode_auth_info(uint8_t *data, size_t data_len,
+			   struct osmo_auth_vector *auth_vector)
+{
+	int rc;
+	uint8_t tag;
+	uint8_t *value;
+	size_t value_len;
+	enum osmo_gsup_iei iei;
+	uint8_t presence = 0;
+
+	/* specific parts */
+	while (data_len > 0) {
+		rc = osmo_shift_tlv(&data, &data_len, &tag, &value, &value_len);
+		if (rc < 0)
+			return -GMM_CAUSE_PROTO_ERR_UNSPEC;
+
+		iei = tag;
+
+		switch (iei) {
+		case OSMO_GSUP_RAND_IE:
+			if (value_len != sizeof(auth_vector->rand))
+				goto parse_error;
+
+			memcpy(auth_vector->rand, value, value_len);
+			presence |= (1 << 0);
+			break;
+
+		case OSMO_GSUP_SRES_IE:
+			if (value_len != sizeof(auth_vector->sres))
+				goto parse_error;
+
+			memcpy(auth_vector->sres, value, value_len);
+			presence |= (1 << 1);
+			break;
+
+		case OSMO_GSUP_KC_IE:
+			if (value_len != sizeof(auth_vector->kc))
+				goto parse_error;
+
+			memcpy(auth_vector->kc, value, value_len);
+			presence |= (1 << 2);
+			break;
+
+		case OSMO_GSUP_IK_IE:
+			if (value_len != sizeof(auth_vector->ik))
+				goto parse_error;
+			memcpy(auth_vector->ik, value, value_len);
+			presence |= (1 << 4);
+			break;
+
+		case OSMO_GSUP_CK_IE:
+			if (value_len != sizeof(auth_vector->ck))
+				goto parse_error;
+			memcpy(auth_vector->ck, value, value_len);
+			presence |= (1 << 5);
+			break;
+
+		case OSMO_GSUP_AUTN_IE:
+			if (value_len != sizeof(auth_vector->autn))
+				goto parse_error;
+			memcpy(auth_vector->autn, value, value_len);
+			presence |= (1 << 6);
+			break;
+		case OSMO_GSUP_RES_IE:
+			if (value_len > sizeof(auth_vector->res))
+				goto parse_error;
+			memcpy(auth_vector->res, value, value_len);
+			auth_vector->res_len = value_len;
+			presence |= (1 << 7);
+			break;
+
+		default:
+			LOGP(DLGSUP, LOGL_ERROR,
+			     "GSUP IE type %d not expected in PDP info\n", iei);
+			continue;
+		}
+	}
+
+	if (presence & 0x07)
+		auth_vector->auth_types |= OSMO_AUTH_TYPE_GSM;
+	if (presence & 0xf0)
+		auth_vector->auth_types |= OSMO_AUTH_TYPE_UMTS;
+
+	return 0;
+
+parse_error:
+	LOGP(DLGSUP, LOGL_ERROR,
+	     "GSUP IE type %d, length %zu invalid in PDP info\n", iei, value_len);
+
+	return -1;
+}
+
+/*! Decode (parse) a GSUP message
+ *  \param[in] const_data input data to be parsed
+ *  \param[in] data_len length of input (\a const_data)
+ *  \param[out] gsup_msg callee-allocated output data structure
+ *  \returns 0 on success; negative otherwise
+ */
+int osmo_gsup_decode(const uint8_t *const_data, size_t data_len,
+		     struct osmo_gsup_message *gsup_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;
+	static const struct osmo_gsup_pdp_info empty_pdp_info = {0};
+	static const struct osmo_auth_vector empty_auth_info = {0};
+	static const struct osmo_gsup_message empty_gsup_message = {0};
+
+	*gsup_msg = empty_gsup_message;
+
+	/* generic part */
+	rc = osmo_shift_v_fixed(&data, &data_len, 1, &value);
+	if (rc < 0)
+		return -GMM_CAUSE_INV_MAND_INFO;
+
+	gsup_msg->message_type = osmo_decode_big_endian(value, 1);
+
+	rc = osmo_match_shift_tlv(&data, &data_len, OSMO_GSUP_IMSI_IE,
+			    &value, &value_len);
+
+	if (rc <= 0)
+		return -GMM_CAUSE_INV_MAND_INFO;
+
+	if (value_len * 2 + 1 > sizeof(gsup_msg->imsi))
+		return -GMM_CAUSE_INV_MAND_INFO;
+
+	/* Note that gsm48_decode_bcd_number expects the number of encoded IMSI
+	 * octets in the first octet. By coincidence (the TLV encoding) the byte
+	 * before the value part already contains this length so we can use it
+	 * here.
+	 */
+	OSMO_ASSERT(value[-1] == value_len);
+	gsm48_decode_bcd_number(gsup_msg->imsi, sizeof(gsup_msg->imsi),
+				value - 1, 0);
+
+	/* specific parts */
+	while (data_len > 0) {
+		enum osmo_gsup_iei iei;
+		struct osmo_gsup_pdp_info pdp_info;
+		struct osmo_auth_vector auth_info;
+
+		rc = osmo_shift_tlv(&data, &data_len, &tag, &value, &value_len);
+		if (rc < 0)
+			return -GMM_CAUSE_PROTO_ERR_UNSPEC;
+
+		iei = tag;
+
+		switch (iei) {
+		case OSMO_GSUP_IMSI_IE:
+		case OSMO_GSUP_PDP_TYPE_IE:
+		case OSMO_GSUP_ACCESS_POINT_NAME_IE:
+		case OSMO_GSUP_RAND_IE:
+		case OSMO_GSUP_SRES_IE:
+		case OSMO_GSUP_KC_IE:
+			LOGP(DLGSUP, LOGL_NOTICE,
+			     "GSUP IE type %d not expected (ignored)\n", iei);
+			continue;
+
+		case OSMO_GSUP_CAUSE_IE:
+			gsup_msg->cause = osmo_decode_big_endian(value, value_len);
+			break;
+
+		case OSMO_GSUP_CANCEL_TYPE_IE:
+			gsup_msg->cancel_type =
+				osmo_decode_big_endian(value, value_len) + 1;
+			break;
+
+		case OSMO_GSUP_PDP_INFO_COMPL_IE:
+			gsup_msg->pdp_info_compl = 1;
+			break;
+
+		case OSMO_GSUP_FREEZE_PTMSI_IE:
+			gsup_msg->freeze_ptmsi = 1;
+			break;
+
+		case OSMO_GSUP_PDP_CONTEXT_ID_IE:
+			/* When these IE appear in the top-level part of the
+			 * message, they are used by Delete Subscr Info to delete
+			 * single entries. We don't have an extra list for
+			 * these but use the PDP info list instead */
+
+			/* fall through */
+
+		case OSMO_GSUP_PDP_INFO_IE:
+			if (gsup_msg->num_pdp_infos >= OSMO_GSUP_MAX_NUM_PDP_INFO) {
+				LOGP(DLGSUP, LOGL_ERROR,
+				     "GSUP IE type %d (PDP_INFO) max exceeded\n",
+				     iei);
+				return -GMM_CAUSE_COND_IE_ERR;
+			}
+
+			pdp_info = empty_pdp_info;
+
+			if (iei == OSMO_GSUP_PDP_INFO_IE) {
+				rc = decode_pdp_info(value, value_len, &pdp_info);
+				if (rc < 0)
+					return rc;
+				pdp_info.have_info = 1;
+			} else {
+				pdp_info.context_id =
+					osmo_decode_big_endian(value, value_len);
+			}
+
+			gsup_msg->pdp_infos[gsup_msg->num_pdp_infos++] =
+				pdp_info;
+			break;
+
+		case OSMO_GSUP_AUTH_TUPLE_IE:
+			if (gsup_msg->num_auth_vectors >= OSMO_GSUP_MAX_NUM_AUTH_INFO) {
+				LOGP(DLGSUP, LOGL_ERROR,
+				     "GSUP IE type %d (AUTH_INFO) max exceeded\n",
+				     iei);
+				return -GMM_CAUSE_INV_MAND_INFO;
+			}
+
+			auth_info = empty_auth_info;
+
+			rc = decode_auth_info(value, value_len, &auth_info);
+			if (rc < 0)
+				return rc;
+
+			gsup_msg->auth_vectors[gsup_msg->num_auth_vectors++] =
+				auth_info;
+			break;
+
+		case OSMO_GSUP_AUTS_IE:
+			if (value_len != 16) {
+				LOGP(DLGSUP, LOGL_ERROR,
+					"AUTS length != 16 received\n");
+				return -GMM_CAUSE_COND_IE_ERR;
+			}
+			gsup_msg->auts = value;
+			break;
+
+		case OSMO_GSUP_MSISDN_IE:
+			gsup_msg->msisdn_enc = value;
+			gsup_msg->msisdn_enc_len = value_len;
+			break;
+
+		case OSMO_GSUP_HLR_NUMBER_IE:
+			gsup_msg->hlr_enc = value;
+			gsup_msg->hlr_enc_len = value_len;
+			break;
+
+		default:
+			LOGP(DLGSUP, LOGL_NOTICE,
+			     "GSUP IE type %d unknown\n", iei);
+			continue;
+		}
+	}
+
+	return 0;
+}
+
+static void encode_pdp_info(struct msgb *msg, enum osmo_gsup_iei iei,
+			    const struct osmo_gsup_pdp_info *pdp_info)
+{
+	uint8_t *len_field;
+	size_t old_len;
+	uint8_t u8;
+
+	len_field = msgb_tlv_put(msg, iei, 0, NULL) - 1;
+	old_len = msgb_length(msg);
+
+	u8 = pdp_info->context_id;
+	msgb_tlv_put(msg, OSMO_GSUP_PDP_CONTEXT_ID_IE, sizeof(u8), &u8);
+
+	if (pdp_info->pdp_type) {
+		msgb_tlv_put(msg, OSMO_GSUP_PDP_TYPE_IE,
+			     OSMO_GSUP_PDP_TYPE_SIZE,
+			     osmo_encode_big_endian(pdp_info->pdp_type | 0xf000,
+					       OSMO_GSUP_PDP_TYPE_SIZE));
+	}
+
+	if (pdp_info->apn_enc) {
+		msgb_tlv_put(msg, OSMO_GSUP_ACCESS_POINT_NAME_IE,
+			     pdp_info->apn_enc_len, pdp_info->apn_enc);
+	}
+
+	if (pdp_info->qos_enc) {
+		msgb_tlv_put(msg, OSMO_GSUP_PDP_QOS_IE,
+				pdp_info->qos_enc_len, pdp_info->qos_enc);
+	}
+
+	/* Update length field */
+	*len_field = msgb_length(msg) - old_len;
+}
+
+static void encode_auth_info(struct msgb *msg, enum osmo_gsup_iei iei,
+			     const struct osmo_auth_vector *auth_vector)
+{
+	uint8_t *len_field;
+	size_t old_len;
+
+	len_field = msgb_tlv_put(msg, iei, 0, NULL) - 1;
+	old_len = msgb_length(msg);
+
+	msgb_tlv_put(msg, OSMO_GSUP_RAND_IE,
+		     sizeof(auth_vector->rand), auth_vector->rand);
+
+	msgb_tlv_put(msg, OSMO_GSUP_SRES_IE,
+		     sizeof(auth_vector->sres), auth_vector->sres);
+
+	msgb_tlv_put(msg, OSMO_GSUP_KC_IE,
+		     sizeof(auth_vector->kc), auth_vector->kc);
+
+	/* Update length field */
+	*len_field = msgb_length(msg) - old_len;
+}
+
+/*! Encode a GSUP message
+ *  \param[out] msg message buffer to which encoded message is written
+ *  \param[in] gsup_msg \ref osmo_gsup_message data to be encoded
+ */
+void osmo_gsup_encode(struct msgb *msg, const struct osmo_gsup_message *gsup_msg)
+{
+	uint8_t u8;
+	int idx;
+	uint8_t bcd_buf[GSM48_MI_SIZE] = {0};
+	size_t bcd_len;
+
+	/* generic part */
+	OSMO_ASSERT(gsup_msg->message_type);
+	msgb_v_put(msg, gsup_msg->message_type);
+
+	bcd_len = gsm48_encode_bcd_number(bcd_buf, sizeof(bcd_buf), 0,
+					  gsup_msg->imsi);
+
+	OSMO_ASSERT(bcd_len > 1);
+
+	/* Note that gsm48_encode_bcd_number puts the length into the first
+	 * octet. Since msgb_tlv_put will add this length byte, we'll have to
+	 * skip it */
+	msgb_tlv_put(msg, OSMO_GSUP_IMSI_IE, bcd_len - 1, &bcd_buf[1]);
+
+	/* specific parts */
+	if (gsup_msg->msisdn_enc)
+		msgb_tlv_put(msg, OSMO_GSUP_MSISDN_IE,
+				gsup_msg->msisdn_enc_len, gsup_msg->msisdn_enc);
+	if (gsup_msg->hlr_enc)
+		msgb_tlv_put(msg, OSMO_GSUP_HLR_NUMBER_IE,
+				gsup_msg->hlr_enc_len, gsup_msg->hlr_enc);
+
+	if ((u8 = gsup_msg->cause))
+		msgb_tlv_put(msg, OSMO_GSUP_CAUSE_IE, sizeof(u8), &u8);
+
+	if ((u8 = gsup_msg->cancel_type)) {
+		u8 -= 1;
+		msgb_tlv_put(msg, OSMO_GSUP_CANCEL_TYPE_IE, sizeof(u8), &u8);
+	}
+
+	if (gsup_msg->pdp_info_compl)
+		msgb_tlv_put(msg, OSMO_GSUP_PDP_INFO_COMPL_IE, 0, &u8);
+
+	if (gsup_msg->freeze_ptmsi)
+		msgb_tlv_put(msg, OSMO_GSUP_FREEZE_PTMSI_IE, 0, &u8);
+
+	for (idx = 0; idx < gsup_msg->num_pdp_infos; idx++) {
+		const struct osmo_gsup_pdp_info *pdp_info;
+
+		pdp_info = &gsup_msg->pdp_infos[idx];
+
+		if (pdp_info->context_id == 0)
+			continue;
+
+		if (pdp_info->have_info) {
+			encode_pdp_info(msg, OSMO_GSUP_PDP_INFO_IE, pdp_info);
+		} else {
+			u8 = pdp_info->context_id;
+			msgb_tlv_put(msg, OSMO_GSUP_PDP_CONTEXT_ID_IE,
+				     sizeof(u8), &u8);
+		}
+	}
+
+	for (idx = 0; idx < gsup_msg->num_auth_vectors; idx++) {
+		const struct osmo_auth_vector *auth_vector;
+
+		auth_vector = &gsup_msg->auth_vectors[idx];
+
+		encode_auth_info(msg, OSMO_GSUP_AUTH_TUPLE_IE, auth_vector);
+	}
+
+	if (gsup_msg->auts)
+		msgb_tlv_put(msg, OSMO_GSUP_AUTS_IE, 16, gsup_msg->auts);
+}
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 8bd0dbfe..e0d9dcbd 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -309,5 +309,8 @@ osmo_apn_qualify_from_imsi;
 osmo_apn_to_str;
 osmo_apn_from_str;
 
+osmo_gsup_encode;
+osmo_gsup_decode;
+
 local: *;
 };
diff --git a/tests/Makefile.am b/tests/Makefile.am
index fa814c72..6c9929b9 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -13,7 +13,7 @@ check_PROGRAMS = timer/timer_test sms/sms_test ussd/ussd_test		\
 		 vty/vty_test comp128/comp128_test utils/utils_test	\
 		 smscb/gsm0341_test stats/stats_test			\
 		 bitvec/bitvec_test msgb/msgb_test bits/bitcomp_test	\
-		 sim/sim_test tlv/tlv_test
+		 sim/sim_test tlv/tlv_test gsup/gsup_test
 
 if ENABLE_MSGFILE
 check_PROGRAMS += msgfile/msgfile_test
@@ -112,6 +112,9 @@ sim_sim_test_LDADD = $(top_builddir)/src/sim/libosmosim.la $(top_builddir)/src/l
 tlv_tlv_test_SOURCES = tlv/tlv_test.c
 tlv_tlv_test_LDADD = $(top_builddir)/src/gsm/libosmogsm.la $(top_builddir)/src/libosmocore.la
 
+gsup_gsup_test_SOURCES = gsup/gsup_test.c
+gsup_gsup_test_LDADD = $(top_builddir)/src/gsm/libosmogsm.la $(top_builddir)/src/libosmocore.la
+
 # The `:;' works around a Bash 3.2 bug when the output is not writeable.
 $(srcdir)/package.m4: $(top_srcdir)/configure.ac
 	:;{ \
@@ -146,7 +149,7 @@ EXTRA_DIST = testsuite.at $(srcdir)/package.m4 $(TESTSUITE)		\
 	     vty/vty_test.ok comp128/comp128_test.ok			\
 	     utils/utils_test.ok stats/stats_test.ok			\
 	     bitvec/bitvec_test.ok msgb/msgb_test.ok bits/bitcomp_test.ok \
-	     sim/sim_test.ok tlv/tlv_test.ok
+	     sim/sim_test.ok tlv/tlv_test.ok gsup/gsup_test.ok
 
 DISTCLEANFILES = atconfig
 
diff --git a/tests/gsup/gsup_test.c b/tests/gsup/gsup_test.c
new file mode 100644
index 00000000..2b0a2938
--- /dev/null
+++ b/tests/gsup/gsup_test.c
@@ -0,0 +1,264 @@
+#include <string.h>
+
+#include <osmocom/core/logging.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/application.h>
+#include <osmocom/gsm/gsup.h>
+
+#define VERBOSE_FPRINTF(...)
+
+/* Tests for osmo_gsup_messages.c */
+
+#define TEST_IMSI_IE 0x01, 0x08, 0x21, 0x43, 0x65, 0x87, 0x09, 0x21, 0x43, 0xf5
+#define TEST_IMSI_STR "123456789012345"
+
+static void test_gsup_messages_dec_enc(void)
+{
+	int test_idx;
+	int rc;
+	uint8_t buf[1024];
+
+	static const uint8_t send_auth_info_req[] = {
+		0x08,
+		TEST_IMSI_IE
+	};
+
+	static const uint8_t send_auth_info_err[] = {
+		0x09,
+		TEST_IMSI_IE,
+		0x02, 0x01, 0x07 /* GPRS no allowed */
+	};
+
+	static const uint8_t send_auth_info_res[] = {
+		0x0a,
+		TEST_IMSI_IE,
+		0x03, 0x22, /* Auth tuple */
+			0x20, 0x10,
+				0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+				0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10,
+			0x21, 0x04,
+				0x21, 0x22, 0x23, 0x24,
+			0x22, 0x08,
+				0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+		0x03, 0x22, /* Auth tuple */
+			0x20, 0x10,
+				0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88,
+				0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, 0x90,
+			0x21, 0x04,
+				0xa1, 0xa2, 0xa3, 0xa4,
+			0x22, 0x08,
+				0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8,
+	};
+
+	static const uint8_t update_location_req[] = {
+		0x04,
+		TEST_IMSI_IE,
+	};
+
+	static const uint8_t update_location_err[] = {
+		0x05,
+		TEST_IMSI_IE,
+		0x02, 0x01, 0x07 /* GPRS no allowed */
+	};
+
+	static const uint8_t update_location_res[] = {
+		0x06,
+		TEST_IMSI_IE,
+		0x08, 0x07, /* MSISDN of the subscriber */
+			0x91, 0x94, 0x61, 0x46, 0x32, 0x24, 0x43,
+		0x09, 0x07, /* HLR-Number of the subscriber */
+			0x91, 0x83, 0x52, 0x38, 0x48, 0x83, 0x93,
+		0x04, 0x00, /* PDP info complete */
+		0x05, 0x15,
+			0x10, 0x01, 0x01,
+			0x11, 0x02, 0xf1, 0x21, /* IPv4 */
+			0x12, 0x09, 0x04, 't', 'e', 's', 't', 0x03, 'a', 'p', 'n',
+			0x13, 0x01, 0x02,
+		0x05, 0x11,
+			0x10, 0x01, 0x02,
+			0x11, 0x02, 0xf1, 0x21, /* IPv4 */
+			0x12, 0x08, 0x03, 'f', 'o', 'o', 0x03, 'a', 'p', 'n',
+	};
+
+	static const uint8_t location_cancellation_req[] = {
+		0x1c,
+		TEST_IMSI_IE,
+		0x06, 0x01, 0x00,
+	};
+
+	static const uint8_t location_cancellation_err[] = {
+		0x1d,
+		TEST_IMSI_IE,
+		0x02, 0x01, 0x03 /* Illegal MS */
+	};
+
+	static const uint8_t location_cancellation_res[] = {
+		0x1e,
+		TEST_IMSI_IE,
+	};
+
+	static const uint8_t purge_ms_req[] = {
+		0x0c,
+		TEST_IMSI_IE,
+	};
+
+	static const uint8_t purge_ms_err[] = {
+		0x0d,
+		TEST_IMSI_IE,
+		0x02, 0x01, 0x03, /* Illegal MS */
+	};
+
+	static const uint8_t purge_ms_res[] = {
+		0x0e,
+		TEST_IMSI_IE,
+		0x07, 0x00,
+	};
+
+	static const struct test {
+		char *name;
+		const uint8_t *data;
+		size_t data_len;
+	} test_messages[] = {
+		{"Send Authentication Info Request",
+			send_auth_info_req, sizeof(send_auth_info_req)},
+		{"Send Authentication Info Error",
+			send_auth_info_err, sizeof(send_auth_info_err)},
+		{"Send Authentication Info Result",
+			send_auth_info_res, sizeof(send_auth_info_res)},
+		{"Update Location Request",
+			update_location_req, sizeof(update_location_req)},
+		{"Update Location Error",
+			update_location_err, sizeof(update_location_err)},
+		{"Update Location Result",
+			update_location_res, sizeof(update_location_res)},
+		{"Location Cancellation Request",
+			location_cancellation_req, sizeof(location_cancellation_req)},
+		{"Location Cancellation Error",
+			location_cancellation_err, sizeof(location_cancellation_err)},
+		{"Location Cancellation Result",
+			location_cancellation_res, sizeof(location_cancellation_res)},
+		{"Purge MS Request",
+			purge_ms_req, sizeof(purge_ms_req)},
+		{"Purge MS Error",
+			purge_ms_err, sizeof(purge_ms_err)},
+		{"Purge MS Result",
+			purge_ms_res, sizeof(purge_ms_res)},
+	};
+
+	printf("Test GSUP message decoding/encoding\n");
+
+	for (test_idx = 0; test_idx < ARRAY_SIZE(test_messages); test_idx++) {
+		const struct test *t = &test_messages[test_idx];
+		struct osmo_gsup_message gm = {0};
+		struct msgb *msg = msgb_alloc(4096, "gsup_test");
+
+		printf("  Testing %s\n", t->name);
+
+		rc = osmo_gsup_decode(t->data, t->data_len, &gm);
+		OSMO_ASSERT(rc >= 0);
+
+		osmo_gsup_encode(msg, &gm);
+
+		fprintf(stderr, "  generated message: %s\n", msgb_hexdump(msg));
+		fprintf(stderr, "  original message:  %s\n", osmo_hexdump(t->data, t->data_len));
+		fprintf(stderr, "  IMSI:              %s\n", gm.imsi);
+		OSMO_ASSERT(strcmp(gm.imsi, TEST_IMSI_STR) == 0);
+		OSMO_ASSERT(msgb_length(msg) == t->data_len);
+		OSMO_ASSERT(memcmp(msgb_data(msg), t->data, t->data_len) == 0);
+
+		msgb_free(msg);
+	}
+
+	/* simple truncation test */
+	for (test_idx = 0; test_idx < ARRAY_SIZE(test_messages); test_idx++) {
+		int j;
+		const struct test *t = &test_messages[test_idx];
+		int ie_end = t->data_len;
+		struct osmo_gsup_message gm = {0};
+		int counter = 0;
+		int parse_err = 0;
+
+		for (j = t->data_len - 1; j >= 0; --j) {
+			rc = osmo_gsup_decode(t->data, j, &gm);
+			counter += 1;
+
+			VERBOSE_FPRINTF(stderr,
+				"  partial message decoding: "
+				"orig_len = %d, trunc = %d, rc = %d, ie_end = %d\n",
+				t->data_len, j, rc, ie_end);
+			if (rc >= 0) {
+				VERBOSE_FPRINTF(stderr,
+					"    remaing partial message: %s\n",
+					osmo_hexdump(t->data + j, ie_end - j));
+
+				OSMO_ASSERT(j <= ie_end - 2);
+				OSMO_ASSERT(t->data[j+0] <= OSMO_GSUP_KC_IE);
+				OSMO_ASSERT(t->data[j+1] <= ie_end - j - 2);
+
+				ie_end = j;
+			} else {
+				parse_err += 1;
+			}
+		}
+
+		fprintf(stderr,
+			"  message %d: tested %d truncations, %d parse failures\n",
+			test_idx, counter, parse_err);
+	}
+
+	/* message modification test (relies on ASAN or valgrind being used) */
+	for (test_idx = 0; test_idx < ARRAY_SIZE(test_messages); test_idx++) {
+		int j;
+		const struct test *t = &test_messages[test_idx];
+		struct osmo_gsup_message gm = {0};
+		uint8_t val;
+		int counter = 0;
+		int parse_err = 0;
+
+		OSMO_ASSERT(sizeof(buf) >= t->data_len);
+
+		for (j = t->data_len - 1; j >= 0; --j) {
+			memcpy(buf, t->data, t->data_len);
+			val = 0;
+			do {
+				VERBOSE_FPRINTF(stderr,
+					"t = %d, len = %d, val = %d\n",
+					test_idx, j, val);
+				buf[j] = val;
+				rc = osmo_gsup_decode(buf, t->data_len, &gm);
+				counter += 1;
+				if (rc < 0)
+					parse_err += 1;
+
+				val += 1;
+			} while (val != (uint8_t)256);
+		}
+
+		fprintf(stderr,
+			"  message %d: tested %d modifications, %d parse failures\n",
+			test_idx, counter, parse_err);
+	}
+}
+
+const struct log_info_cat default_categories[] = {
+	[DLGSUP] = {
+		.name = "DLGSUP",
+		.description = "Generic Subscriber Update Protocol",
+		.enabled = 0, .loglevel = LOGL_DEBUG,
+	},
+};
+
+static struct log_info info = {
+	.cat = default_categories,
+	.num_cat = ARRAY_SIZE(default_categories),
+};
+
+int main(int argc, char **argv)
+{
+	osmo_init_logging(&info);
+
+	test_gsup_messages_dec_enc();
+
+	printf("Done.\n");
+	return EXIT_SUCCESS;
+}
diff --git a/tests/gsup/gsup_test.ok b/tests/gsup/gsup_test.ok
new file mode 100644
index 00000000..1285897c
--- /dev/null
+++ b/tests/gsup/gsup_test.ok
@@ -0,0 +1,14 @@
+Test GSUP message decoding/encoding
+  Testing Send Authentication Info Request
+  Testing Send Authentication Info Error
+  Testing Send Authentication Info Result
+  Testing Update Location Request
+  Testing Update Location Error
+  Testing Update Location Result
+  Testing Location Cancellation Request
+  Testing Location Cancellation Error
+  Testing Location Cancellation Result
+  Testing Purge MS Request
+  Testing Purge MS Error
+  Testing Purge MS Result
+Done.
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 762b10a0..aa269afb 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -190,3 +190,9 @@ AT_KEYWORDS([tlv])
 cat $abs_srcdir/tlv/tlv_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/tlv/tlv_test], [0], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([gsup])
+AT_KEYWORDS([gsup])
+cat $abs_srcdir/gsup/gsup_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/gsup/gsup_test], [0], [expout], [ignore])
+AT_CLEANUP