Change in osmo-ggsn[master]: ggsn: Add minimalistic PAP support

[Harald Welte]

Harald Welte has uploaded this change for review. ( https://gerrit.osmocom.org/13608


Change subject: ggsn: Add minimalistic PAP support
......................................................................

ggsn: Add minimalistic PAP support

Some modems are configured to use PAP as an additional authentication
mechanism beyond the GSM authentication that's part of GMM.  Let's
handle such PAP authentication requests by simply acknowledging them
all, without actually checking any credentials database.

This is the most sane thing we can do for now, without adding external
requirements / interfaces like radius servers or the like.

Change-Id: I81875f30f9f1497199253497f84718510747f731
---
M ggsn/ggsn.c
1 file changed, 63 insertions(+), 1 deletion(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-ggsn refs/changes/08/13608/1

diff --git a/ggsn/ggsn.c b/ggsn/ggsn.c
index f46436f..d079efe 100644
--- a/ggsn/ggsn.c
+++ b/ggsn/ggsn.c
@@ -1,7 +1,7 @@
 /*
  * OsmoGGSN - Gateway GPRS Support Node
  * Copyright (C) 2002, 2003, 2004 Mondru AB.
- * Copyright (C) 2017 by Harald Welte <laforge at gnumonks.org>
+ * Copyright (C) 2017-2019 by Harald Welte <laforge at gnumonks.org>
  *
  * The contents of this file may be used under the terms of the GNU
  * General Public License Version 2, provided that the above copyright
@@ -47,6 +47,7 @@
 #include <osmocom/core/stats.h>
 #include <osmocom/core/rate_ctr.h>
 #include <osmocom/core/timer.h>
+#include <osmocom/core/utils.h>
 #include <osmocom/ctrl/control_if.h>
 #include <osmocom/ctrl/control_cmd.h>
 #include <osmocom/ctrl/control_vty.h>
@@ -494,6 +495,64 @@
 	return NULL;
 }
 
+struct pap_element {
+	uint8_t code;
+	uint8_t id;
+	uint16_t len; /* length including header */
+	uint8_t data[0];
+} __attribute__((packed));
+
+enum pap_code {
+	PAP_CODE_AUTH_REQ = 1,
+	PAP_CODE_AUTH_ACK = 2,
+	PAP_CODE_AUTH_NAK = 3,
+};
+
+static const char *pap_welcome = "Welcome to OsmoGGSN";
+
+/* Handle PAP protocol according to RFC 1334 */
+static void process_pco_element_pap(const struct pco_element *pco_in, struct msgb *resp,
+				    const struct apn_ctx *apn, struct pdp_t *pdp)
+{
+	const struct pap_element *pap_in = (const struct pap_element *) pco_in->data;
+	unsigned int pap_welcome_len = strlen(pap_welcome);
+	uint8_t pap_out_size = sizeof(struct pap_element) + 1 + pap_welcome_len;
+	struct pap_element *pap_out = alloca(pap_out_size);
+	uint8_t peer_id_len;
+	const uint8_t *peer_id;
+
+	if (sizeof(*pap_in) > pco_in->length)
+		goto ret_broken;
+	if (htons(pap_in->len) > pco_in->length)
+		goto ret_broken;
+
+	switch (pap_in->code) {
+	case PAP_CODE_AUTH_REQ:
+		peer_id_len = pap_in->data[0];
+		peer_id = &pap_in->data[1];
+		LOGPPDP(LOGL_DEBUG, pdp, "PCO PAP PeerId = %s, ACKing\n",
+			osmo_quote_str((const char *)peer_id, peer_id_len));
+		/* Password-Length + Password following here, but we don't care */
+		pap_out->code = PAP_CODE_AUTH_ACK;
+		pap_out->id = pap_in->id;
+		pap_out->len = htons(pap_out_size);
+		pap_out->data[0] = pap_welcome_len;
+		memcpy(pap_out->data+1, pap_welcome, pap_welcome_len);
+		msgb_t16lv_put(resp, PCO_P_PAP, pap_out_size, (uint8_t *) pap_out);
+		break;
+	case PAP_CODE_AUTH_ACK:
+	case PAP_CODE_AUTH_NAK:
+	default:
+		LOGPPDP(LOGL_NOTICE, pdp, "Unsupported PAP PCO Code %u, ignoring\n", pap_in->code);
+		break;
+	}
+	return;
+
+ret_broken:
+	LOGPPDP(LOGL_NOTICE, pdp, "Invalid PAP PCO Length: %s, ignoring\n",
+		osmo_hexdump_nospc((const uint8_t *)pco_in, pco_in->length));
+}
+
 static void process_pco_element_ipcp(const struct pco_element *pco_elem, struct msgb *resp,
 				     const struct apn_ctx *apn, struct pdp_t *pdp)
 {
@@ -575,6 +634,9 @@
 				const struct apn_ctx *apn, struct pdp_t *pdp)
 {
 	switch (ntohs(pco_elem->protocol_id)) {
+	case PCO_P_PAP:
+		process_pco_element_pap(pco_elem, resp, apn, pdp);
+		break;
 	case PCO_P_IPCP:
 		process_pco_element_ipcp(pco_elem, resp, apn, pdp);
 		break;

-- 
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Gerrit-Project: osmo-ggsn
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I81875f30f9f1497199253497f84718510747f731
Gerrit-Change-Number: 13608
Gerrit-PatchSet: 1
Gerrit-Owner: Harald Welte <laforge at gnumonks.org>
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