Add preliminary RADIUS dynamic authorization server (RFC 5176)

This adds the basic DAS mechanism to enable hostapd to be configured
to request dynamic authorization requests (Disconnect-Request and
CoA-Request). This commit does not add actual processing of the
requests, i.e., this will only receive and authenticate the requests
and NAK them regardless of what operation is requested.

Signed-hostap: Jouni Malinen <j@w1.fi>

src/radius/radius_das.c

@@ -0,0 +1,222 @@
+/*
+ * RADIUS Dynamic Authorization Server (DAS) (RFC 5176)
+ * Copyright (c) 2012, Jouni Malinen <j@w1.fi>
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+#include "includes.h"
+#include <net/if.h>
+
+#include "utils/common.h"
+#include "utils/eloop.h"
+#include "utils/ip_addr.h"
+#include "radius.h"
+#include "radius_das.h"
+
+
+extern int wpa_debug_level;
+
+
+struct radius_das_data {
+	int sock;
+	u8 *shared_secret;
+	size_t shared_secret_len;
+	struct hostapd_ip_addr client_addr;
+};
+
+
+static void radius_das_receive(int sock, void *eloop_ctx, void *sock_ctx)
+{
+	struct radius_das_data *das = eloop_ctx;
+	u8 buf[1500];
+	union {
+		struct sockaddr_storage ss;
+		struct sockaddr_in sin;
+#ifdef CONFIG_IPV6
+		struct sockaddr_in6 sin6;
+#endif /* CONFIG_IPV6 */
+	} from;
+	char abuf[50];
+	int from_port = 0;
+	socklen_t fromlen;
+	int len;
+	struct radius_msg *msg, *reply = NULL;
+	struct radius_hdr *hdr;
+	struct wpabuf *rbuf;
+
+	fromlen = sizeof(from);
+	len = recvfrom(sock, buf, sizeof(buf), 0,
+		       (struct sockaddr *) &from.ss, &fromlen);
+	if (len < 0) {
+		wpa_printf(MSG_ERROR, "DAS: recvfrom: %s", strerror(errno));
+		return;
+	}
+
+	os_strlcpy(abuf, inet_ntoa(from.sin.sin_addr), sizeof(abuf));
+	from_port = ntohs(from.sin.sin_port);
+
+	wpa_printf(MSG_DEBUG, "DAS: Received %d bytes from %s:%d",
+		   len, abuf, from_port);
+	if (das->client_addr.u.v4.s_addr != from.sin.sin_addr.s_addr) {
+		wpa_printf(MSG_DEBUG, "DAS: Drop message from unknown client");
+		return;
+	}
+
+	msg = radius_msg_parse(buf, len);
+	if (msg == NULL) {
+		wpa_printf(MSG_DEBUG, "DAS: Parsing incoming RADIUS packet "
+			   "from %s:%d failed", abuf, from_port);
+		return;
+	}
+
+	if (wpa_debug_level <= MSG_MSGDUMP)
+		radius_msg_dump(msg);
+
+	if (radius_msg_verify_das_req(msg, das->shared_secret,
+				       das->shared_secret_len)) {
+		wpa_printf(MSG_DEBUG, "DAS: Invalid authenticator in packet "
+			   "from %s:%d - drop", abuf, from_port);
+		goto fail;
+	}
+
+	hdr = radius_msg_get_hdr(msg);
+
+	switch (hdr->code) {
+	case RADIUS_CODE_DISCONNECT_REQUEST:
+		/* TODO */
+		reply = radius_msg_new(RADIUS_CODE_DISCONNECT_NAK,
+				       hdr->identifier);
+		if (reply == NULL)
+			break;
+
+		radius_msg_add_attr_int32(reply, RADIUS_ATTR_ERROR_CAUSE, 405);
+		break;
+	case RADIUS_CODE_COA_REQUEST:
+		/* TODO */
+		reply = radius_msg_new(RADIUS_CODE_COA_NAK,
+				       hdr->identifier);
+		if (reply == NULL)
+			break;
+
+		/* Unsupported Service */
+		radius_msg_add_attr_int32(reply, RADIUS_ATTR_ERROR_CAUSE, 405);
+		break;
+	default:
+		wpa_printf(MSG_DEBUG, "DAS: Unexpected RADIUS code %u in "
+			   "packet from %s:%d",
+			   hdr->code, abuf, from_port);
+	}
+
+	if (reply) {
+		int res;
+
+		wpa_printf(MSG_DEBUG, "DAS: Reply to %s:%d", abuf, from_port);
+
+		if (radius_msg_finish_das_resp(reply, das->shared_secret,
+					       das->shared_secret_len, hdr) <
+		    0) {
+			wpa_printf(MSG_DEBUG, "DAS: Failed to add "
+				   "Message-Authenticator attribute");
+		}
+
+		if (wpa_debug_level <= MSG_MSGDUMP)
+			radius_msg_dump(reply);
+
+		rbuf = radius_msg_get_buf(reply);
+		res = sendto(das->sock, wpabuf_head(rbuf),
+			     wpabuf_len(rbuf), 0,
+			     (struct sockaddr *) &from.ss, fromlen);
+		if (res < 0) {
+			wpa_printf(MSG_ERROR, "DAS: sendto(to %s:%d): %s",
+				   abuf, from_port, strerror(errno));
+		}
+	}
+
+fail:
+	radius_msg_free(msg);
+	radius_msg_free(reply);
+}
+
+
+static int radius_das_open_socket(int port)
+{
+	int s;
+	struct sockaddr_in addr;
+
+	s = socket(PF_INET, SOCK_DGRAM, 0);
+	if (s < 0) {
+		perror("socket");
+		return -1;
+	}
+
+	os_memset(&addr, 0, sizeof(addr));
+	addr.sin_family = AF_INET;
+	addr.sin_port = htons(port);
+	if (bind(s, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
+		perror("bind");
+		close(s);
+		return -1;
+	}
+
+	return s;
+}
+
+
+struct radius_das_data *
+radius_das_init(struct radius_das_conf *conf)
+{
+	struct radius_das_data *das;
+
+	if (conf->port == 0 || conf->shared_secret == NULL ||
+	    conf->client_addr == NULL)
+		return NULL;
+
+	das = os_zalloc(sizeof(*das));
+	if (das == NULL)
+		return NULL;
+
+	os_memcpy(&das->client_addr, conf->client_addr,
+		  sizeof(das->client_addr));
+
+	das->shared_secret = os_malloc(conf->shared_secret_len);
+	if (das->shared_secret == NULL) {
+		radius_das_deinit(das);
+		return NULL;
+	}
+	os_memcpy(das->shared_secret, conf->shared_secret,
+		  conf->shared_secret_len);
+	das->shared_secret_len = conf->shared_secret_len;
+
+	das->sock = radius_das_open_socket(conf->port);
+	if (das->sock < 0) {
+		wpa_printf(MSG_ERROR, "Failed to open UDP socket for RADIUS "
+			   "DAS");
+		radius_das_deinit(das);
+		return NULL;
+	}
+
+	if (eloop_register_read_sock(das->sock, radius_das_receive, das, NULL))
+	{
+		radius_das_deinit(das);
+		return NULL;
+	}
+
+	return das;
+}
+
+
+void radius_das_deinit(struct radius_das_data *das)
+{
+	if (das == NULL)
+		return;
+
+	if (das->sock >= 0) {
+		eloop_unregister_read_sock(das->sock);
+		close(das->sock);
+	}
+
+	os_free(das->shared_secret);
+	os_free(das);
+}