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>

4 files changed, 393 insertions, 3 deletions

diff --git a/src/radius/radius.c b/src/radius/radius.c
index 0dd6b12..ed0a9de 100644
--- a/src/radius/radius.c
+++ b/src/radius/radius.c
@@ -1,6 +1,6 @@
 /*
  * RADIUS message processing
- * Copyright (c) 2002-2009, Jouni Malinen <j@w1.fi>
+ * Copyright (c) 2002-2009, 2011-2012, Jouni Malinen <j@w1.fi>
  *
  * This software may be distributed under the terms of the BSD license.
  * See README for more details.
@@ -147,6 +147,12 @@ static const char *radius_code_string(u8 code)
 	case RADIUS_CODE_STATUS_SERVER: return "Status-Server";
 	case RADIUS_CODE_STATUS_CLIENT: return "Status-Client";
 	case RADIUS_CODE_RESERVED: return "Reserved";
+	case RADIUS_CODE_DISCONNECT_REQUEST: return "Disconnect-Request";
+	case RADIUS_CODE_DISCONNECT_ACK: return "Disconnect-ACK";
+	case RADIUS_CODE_DISCONNECT_NAK: return "Disconnect-NAK";
+	case RADIUS_CODE_COA_REQUEST: return "CoA-Request";
+	case RADIUS_CODE_COA_ACK: return "CoA-ACK";
+	case RADIUS_CODE_COA_NAK: return "CoA-NAK";
 	default: return "?Unknown?";
 	}
 }
@@ -225,6 +231,7 @@ static struct radius_attr_type radius_attrs[] =
 	{ RADIUS_ATTR_CHARGEABLE_USER_IDENTITY, "Chargable-User-Identity",
 	  RADIUS_ATTR_TEXT },
 	{ RADIUS_ATTR_NAS_IPV6_ADDRESS, "NAS-IPv6-Address", RADIUS_ATTR_IPV6 },
+	{ RADIUS_ATTR_ERROR_CAUSE, "Error-Cause", RADIUS_ATTR_INT32 }
 };
 #define RADIUS_ATTRS (sizeof(radius_attrs) / sizeof(radius_attrs[0]))
 
@@ -406,6 +413,45 @@ int radius_msg_finish_srv(struct radius_msg *msg, const u8 *secret,
 }
 
 
+int radius_msg_finish_das_resp(struct radius_msg *msg, const u8 *secret,
+			       size_t secret_len,
+			       const struct radius_hdr *req_hdr)
+{
+	const u8 *addr[2];
+	size_t len[2];
+	u8 auth[MD5_MAC_LEN];
+	struct radius_attr_hdr *attr;
+
+	os_memset(auth, 0, MD5_MAC_LEN);
+	attr = radius_msg_add_attr(msg, RADIUS_ATTR_MESSAGE_AUTHENTICATOR,
+				   auth, MD5_MAC_LEN);
+	if (attr == NULL) {
+		wpa_printf(MSG_WARNING, "Could not add Message-Authenticator");
+		return -1;
+	}
+
+	msg->hdr->length = htons(wpabuf_len(msg->buf));
+	os_memcpy(msg->hdr->authenticator, req_hdr->authenticator, 16);
+	hmac_md5(secret, secret_len, wpabuf_head(msg->buf),
+		 wpabuf_len(msg->buf), (u8 *) (attr + 1));
+
+	/* ResponseAuth = MD5(Code+ID+Length+RequestAuth+Attributes+Secret) */
+	addr[0] = wpabuf_head_u8(msg->buf);
+	len[0] = wpabuf_len(msg->buf);
+	addr[1] = secret;
+	len[1] = secret_len;
+	if (md5_vector(2, addr, len, msg->hdr->authenticator) < 0)
+		return -1;
+
+	if (wpabuf_len(msg->buf) > 0xffff) {
+		wpa_printf(MSG_WARNING, "RADIUS: Too long message (%lu)",
+			   (unsigned long) wpabuf_len(msg->buf));
+		return -1;
+	}
+	return 0;
+}
+
+
 void radius_msg_finish_acct(struct radius_msg *msg, const u8 *secret,
 			    size_t secret_len)
 {
@@ -427,6 +473,88 @@ void radius_msg_finish_acct(struct radius_msg *msg, const u8 *secret,
 }
 
 
+int radius_msg_verify_acct_req(struct radius_msg *msg, const u8 *secret,
+			       size_t secret_len)
+{
+	const u8 *addr[4];
+	size_t len[4];
+	u8 zero[MD5_MAC_LEN];
+	u8 hash[MD5_MAC_LEN];
+
+	os_memset(zero, 0, sizeof(zero));
+	addr[0] = (u8 *) msg->hdr;
+	len[0] = sizeof(struct radius_hdr) - MD5_MAC_LEN;
+	addr[1] = zero;
+	len[1] = MD5_MAC_LEN;
+	addr[2] = (u8 *) (msg->hdr + 1);
+	len[2] = wpabuf_len(msg->buf) - sizeof(struct radius_hdr);
+	addr[3] = secret;
+	len[3] = secret_len;
+	md5_vector(4, addr, len, hash);
+	return os_memcmp(msg->hdr->authenticator, hash, MD5_MAC_LEN) != 0;
+}
+
+
+int radius_msg_verify_das_req(struct radius_msg *msg, const u8 *secret,
+			      size_t secret_len)
+{
+	const u8 *addr[4];
+	size_t len[4];
+	u8 zero[MD5_MAC_LEN];
+	u8 hash[MD5_MAC_LEN];
+	u8 auth[MD5_MAC_LEN], orig[MD5_MAC_LEN];
+	u8 orig_authenticator[16];
+
+	struct radius_attr_hdr *attr = NULL, *tmp;
+	size_t i;
+
+	os_memset(zero, 0, sizeof(zero));
+	addr[0] = (u8 *) msg->hdr;
+	len[0] = sizeof(struct radius_hdr) - MD5_MAC_LEN;
+	addr[1] = zero;
+	len[1] = MD5_MAC_LEN;
+	addr[2] = (u8 *) (msg->hdr + 1);
+	len[2] = wpabuf_len(msg->buf) - sizeof(struct radius_hdr);
+	addr[3] = secret;
+	len[3] = secret_len;
+	md5_vector(4, addr, len, hash);
+	if (os_memcmp(msg->hdr->authenticator, hash, MD5_MAC_LEN) != 0)
+		return 1;
+
+	for (i = 0; i < msg->attr_used; i++) {
+		tmp = radius_get_attr_hdr(msg, i);
+		if (tmp->type == RADIUS_ATTR_MESSAGE_AUTHENTICATOR) {
+			if (attr != NULL) {
+				wpa_printf(MSG_WARNING, "Multiple "
+					   "Message-Authenticator attributes "
+					   "in RADIUS message");
+				return 1;
+			}
+			attr = tmp;
+		}
+	}
+
+	if (attr == NULL) {
+		/* Message-Authenticator is MAY; not required */
+		return 0;
+	}
+
+	os_memcpy(orig, attr + 1, MD5_MAC_LEN);
+	os_memset(attr + 1, 0, MD5_MAC_LEN);
+	os_memcpy(orig_authenticator, msg->hdr->authenticator,
+		  sizeof(orig_authenticator));
+	os_memset(msg->hdr->authenticator, 0,
+		  sizeof(msg->hdr->authenticator));
+	hmac_md5(secret, secret_len, wpabuf_head(msg->buf),
+		 wpabuf_len(msg->buf), auth);
+	os_memcpy(attr + 1, orig, MD5_MAC_LEN);
+	os_memcpy(msg->hdr->authenticator, orig_authenticator,
+		  sizeof(orig_authenticator));
+
+	return os_memcmp(orig, auth, MD5_MAC_LEN) != 0;
+}
+
+
 static int radius_msg_add_attr_to_array(struct radius_msg *msg,
 					struct radius_attr_hdr *attr)
 {
diff --git a/src/radius/radius.h b/src/radius/radius.h
index 44123bd..8cc6113 100644
--- a/src/radius/radius.h
+++ b/src/radius/radius.h
@@ -1,6 +1,6 @@
 /*
  * RADIUS message processing
- * Copyright (c) 2002-2009, Jouni Malinen <j@w1.fi>
+ * Copyright (c) 2002-2009, 2012, Jouni Malinen <j@w1.fi>
  *
  * This software may be distributed under the terms of the BSD license.
  * See README for more details.
@@ -31,6 +31,12 @@ enum { RADIUS_CODE_ACCESS_REQUEST = 1,
        RADIUS_CODE_ACCESS_CHALLENGE = 11,
        RADIUS_CODE_STATUS_SERVER = 12,
        RADIUS_CODE_STATUS_CLIENT = 13,
+       RADIUS_CODE_DISCONNECT_REQUEST = 40,
+       RADIUS_CODE_DISCONNECT_ACK = 41,
+       RADIUS_CODE_DISCONNECT_NAK = 42,
+       RADIUS_CODE_COA_REQUEST = 43,
+       RADIUS_CODE_COA_ACK = 44,
+       RADIUS_CODE_COA_NAK = 45,
        RADIUS_CODE_RESERVED = 255
 };
 
@@ -83,7 +89,8 @@ enum { RADIUS_ATTR_USER_NAME = 1,
        RADIUS_ATTR_TUNNEL_PRIVATE_GROUP_ID = 81,
        RADIUS_ATTR_ACCT_INTERIM_INTERVAL = 85,
        RADIUS_ATTR_CHARGEABLE_USER_IDENTITY = 89,
-       RADIUS_ATTR_NAS_IPV6_ADDRESS = 95
+       RADIUS_ATTR_NAS_IPV6_ADDRESS = 95,
+       RADIUS_ATTR_ERROR_CAUSE = 101
 };
 
 
@@ -192,8 +199,15 @@ int radius_msg_finish(struct radius_msg *msg, const u8 *secret,
 		      size_t secret_len);
 int radius_msg_finish_srv(struct radius_msg *msg, const u8 *secret,
 			  size_t secret_len, const u8 *req_authenticator);
+int radius_msg_finish_das_resp(struct radius_msg *msg, const u8 *secret,
+			       size_t secret_len,
+			       const struct radius_hdr *req_hdr);
 void radius_msg_finish_acct(struct radius_msg *msg, const u8 *secret,
 			    size_t secret_len);
+int radius_msg_verify_acct_req(struct radius_msg *msg, const u8 *secret,
+			       size_t secret_len);
+int radius_msg_verify_das_req(struct radius_msg *msg, const u8 *secret,
+			       size_t secret_len);
 struct radius_attr_hdr * radius_msg_add_attr(struct radius_msg *msg, u8 type,
 					     const u8 *data, size_t data_len);
 struct radius_msg * radius_msg_parse(const u8 *data, size_t len);
diff --git a/src/radius/radius_das.c b/src/radius/radius_das.c
new file mode 100644
index 0000000..ae3df89
--- /dev/null
+++ b/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);
+}
diff --git a/src/radius/radius_das.h b/src/radius/radius_das.h
new file mode 100644
index 0000000..4e21c6d
--- /dev/null
+++ b/src/radius/radius_das.h
@@ -0,0 +1,26 @@
+/*
+ * RADIUS Dynamic Authorization Server (DAS)
+ * 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.
+ */
+
+#ifndef RADIUS_DAS_H
+#define RADIUS_DAS_H
+
+struct radius_das_data;
+
+struct radius_das_conf {
+	int port;
+	const u8 *shared_secret;
+	size_t shared_secret_len;
+	const struct hostapd_ip_addr *client_addr;
+};
+
+struct radius_das_data *
+radius_das_init(struct radius_das_conf *conf);
+
+void radius_das_deinit(struct radius_das_data *data);
+
+#endif /* RADIUS_DAS_H */