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.
Closes: OS#3914
Change-Id: I81875f30f9f1497199253497f84718510747f731
diff --git a/ggsn/ggsn.c b/ggsn/ggsn.c
index c559923..e95471a 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@gnumonks.org>
+ * Copyright (C) 2017-2019 by Harald Welte <laforge@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>
@@ -499,6 +500,87 @@
return NULL;
}
+/* RFC 1334, section 3.2. Packet Format */
+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 " PACKAGE_VERSION;
+
+/* 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;
+ uint16_t pap_in_len;
+ uint8_t peer_id_len;
+ const uint8_t *peer_id;
+ unsigned int pap_welcome_len;
+ uint8_t pap_out_size;
+ struct pap_element *pap_out;
+
+ if (pco_in->length < sizeof(struct pap_element))
+ goto ret_broken;
+
+ pap_in_len = osmo_load16be(&pap_in->len);
+ if (pco_in->length < pap_in_len)
+ goto ret_broken;
+ /* "pco_in->length > pap_in_len" is allowed: RFC1334 2.2 states:
+ "Octets outside the range of the Length field should be treated as
+ Data Link Layer padding and should be ignored on reception."
+ */
+
+ switch (pap_in->code) {
+ case PAP_CODE_AUTH_REQ:
+ if (pap_in_len < sizeof(struct pap_element) + 1)
+ goto ret_broken_auth;
+ peer_id_len = pap_in->data[0];
+ if (pap_in_len < sizeof(struct pap_element) + 1 + peer_id_len)
+ goto ret_broken_auth;
+ 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 */
+
+ /* Prepare response, we ACK all of them: */
+ pap_welcome_len = strlen(pap_welcome);
+ /* +1: Length field of pap_welcome Message */
+ pap_out_size = sizeof(struct pap_element) + 1 + pap_welcome_len;
+ pap_out = alloca(pap_out_size);
+ 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_auth:
+ LOGPPDP(LOGL_NOTICE, pdp, "Invalid PAP AuthenticateReq: %s, ignoring\n",
+ osmo_hexdump_nospc((const uint8_t *)pco_in, pco_in->length));
+ 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)
{
@@ -580,6 +662,9 @@
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;