import oap message parsing / encoding from openbsc.git; AGPL->GPL

In the process, also:
* Change the license from AGPLv3 to GPLv2-or-later;
* correct spelling of 'sysmocom' to lowercase;
* add '2016' to the copyright;
* rename to osmo_*;
* add API docs;
* add logging category DLOAP: define id and add to internal_cat;
* redirect all oap.c logging to DLOAP.

A unit test will follow in a subsequent patch, since it needs a minor tweak for
decoding of boolean values.

The related openbsc change-id is I2f06aaa6eb54eafa860cfed8e72e41d82ff1c4cf.

Tweaked-by: Neels Hofmeyr
Change-Id: If5099e60681a215e798b6675f21813f26769c253

4 files changed, 193 insertions, 1 deletions

diff --git a/src/gsm/Makefile.am b/src/gsm/Makefile.am
index 3877f78a..4ea55e1d 100644
--- a/src/gsm/Makefile.am
+++ b/src/gsm/Makefile.am
@@ -22,7 +22,7 @@ libgsmint_la_SOURCES =  a5.c rxlev_stat.c tlv_parser.c comp128.c comp128v23.c \
 			auth_milenage.c milenage/aes-encblock.c gea.c \
 			milenage/aes-internal.c milenage/aes-internal-enc.c \
 			milenage/milenage.c gan.c ipa.c gsm0341.c apn.c \
-			gsup.c gprs_gea.c gsm0503_conv.c
+			gsup.c gprs_gea.c gsm0503_conv.c oap.c
 libgsmint_la_LDFLAGS = -no-undefined
 libgsmint_la_LIBADD = $(top_builddir)/src/libosmocore.la
 
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 3e7333cc..a3d224f1 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -356,5 +356,8 @@ osmo_apn_from_str;
 osmo_gsup_encode;
 osmo_gsup_decode;
 
+osmo_oap_encode;
+osmo_oap_decode;
+
 local: *;
 };
diff --git a/src/gsm/oap.c b/src/gsm/oap.c
new file mode 100644
index 00000000..979bde65
--- /dev/null
+++ b/src/gsm/oap.c
@@ -0,0 +1,184 @@
+/* Osmocom Authentication Protocol message encoder/decoder */
+
+/* (C) 2015-2016 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 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/>.
+ *
+ */
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/gsm/tlv.h>
+#include <osmocom/gsm/oap.h>
+
+#include <stdint.h>
+
+/*! \brief Decode OAP message data.
+ * \param[out] oap_msg  Parsed data is written to this instance.
+ * \param[in] data  Pointer to the data buffer containing the OAP message.
+ * \param[in] data_len  Length of the OAP message data.
+ * \returns 0 on success, a negative cause value on failure.
+ */
+int osmo_oap_decode(struct osmo_oap_message *oap_msg,
+		    const uint8_t *const_data, size_t data_len)
+{
+	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 = osmo_shift_v_fixed(&data, &data_len, 1, &value);
+	if (rc < 0)
+		return -GMM_CAUSE_INV_MAND_INFO;
+	oap_msg->message_type = osmo_decode_big_endian(value, 1);
+
+	/* specific parts */
+	while (data_len > 0) {
+		enum osmo_oap_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 OAP_CLIENT_ID_IE:
+			if (value_len != 2) {
+				LOGP(DLOAP, 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 = osmo_decode_big_endian(value, value_len);
+
+			if (oap_msg->client_id == 0) {
+				LOGP(DLOAP, 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(DLOAP, 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(DLOAP, 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(DLOAP, 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(DLOAP, 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(DLOAP, 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(DLOAP, LOGL_NOTICE,
+			     "OAP IE type %d unknown\n", iei);
+			continue;
+		}
+	}
+
+	return 0;
+}
+
+/*! \brief Compose OAP message data.
+ * \param[out] msg  OAP message data is appended to this message buffer.
+ * \param[in] oap_msg  Elements to encode in the message data.
+ */
+void osmo_oap_encode(struct msgb *msg, const struct osmo_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),
+			     osmo_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;
+}
diff --git a/src/logging.c b/src/logging.c
index 30d0b8da..92852c9c 100644
--- a/src/logging.c
+++ b/src/logging.c
@@ -128,6 +128,11 @@ static const struct log_info_cat internal_cat[OSMO_NUM_DLIB] = {
 		.description = "Generic Subscriber Update Protocol",
 		.enabled = 1, .loglevel = LOGL_NOTICE,
 	},
+	[INT2IDX(DLOAP)] = {
+		.name = "DLOAP",
+		.description = "Osmocom Authentication Protocol",
+		.enabled = 1, .loglevel = LOGL_NOTICE,
+	},
 };
 
 /*! \brief descriptive string for each log level */