gdhcp: Avoid reading invalid data in dhcp_get_option

Reference:
https://git.kernel.org/pub/scm/network/connman/connman.git/commit/?id=58d397ba74873384aee449690a9070bacd5676fa

Change-Id: I44c6e1f0448ed8fb5b1955da6458fe67c8ff56cb
Signed-off-by: Niraj Kumar Goit <niraj.g@samsung.com>

4 files changed, 38 insertions, 20 deletions

diff --git a/gdhcp/client.c b/gdhcp/client.c
index 80fdf265..bdaa8821 100755
--- a/gdhcp/client.c
+++ b/gdhcp/client.c
@@ -1672,12 +1672,12 @@ static void start_request(GDHCPClient *dhcp_client)
 							NULL);
 }
 
-static uint32_t get_lease(struct dhcp_packet *packet)
+static uint32_t get_lease(struct dhcp_packet *packet, uint16_t packet_len)
 {
 	uint8_t *option;
 	uint32_t lease_seconds;
 
-	option = dhcp_get_option(packet, DHCP_LEASE_TIME);
+	option = dhcp_get_option(packet, packet_len, DHCP_LEASE_TIME);
 	if (!option)
 		return 3600;
 
@@ -2269,7 +2269,8 @@ static void get_dhcpv6_request(GDHCPClient *dhcp_client,
 	}
 }
 
-static void get_request(GDHCPClient *dhcp_client, struct dhcp_packet *packet)
+static void get_request(GDHCPClient *dhcp_client, struct dhcp_packet *packet,
+		uint16_t packet_len)
 {
 	GDHCPOptionType type;
 	GList *list, *value_list;
@@ -2280,7 +2281,7 @@ static void get_request(GDHCPClient *dhcp_client, struct dhcp_packet *packet)
 	for (list = dhcp_client->request_list; list; list = list->next) {
 		code = (uint8_t) GPOINTER_TO_INT(list->data);
 
-		option = dhcp_get_option(packet, code);
+		option = dhcp_get_option(packet, packet_len, code);
 		if (!option) {
 			g_hash_table_remove(dhcp_client->code_value_hash,
 						GINT_TO_POINTER((int) code));
@@ -2348,6 +2349,7 @@ static gboolean listener_event(GIOChannel *channel, GIOCondition condition,
 		re = dhcp_recv_l2_packet(&packet,
 					dhcp_client->listener_sockfd,
 					&dst_addr);
+		pkt_len = (uint16_t)(unsigned int)re;
 		xid = packet.xid;
 	} else if (dhcp_client->listen_mode == L3) {
 		if (dhcp_client->type == G_DHCP_IPV6) {
@@ -2412,7 +2414,7 @@ static gboolean listener_event(GIOChannel *channel, GIOCondition condition,
 			dhcp_client->status_code = status;
 		}
 	} else {
-		message_type = dhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
+		message_type = dhcp_get_option(&packet, pkt_len, DHCP_MESSAGE_TYPE);
 		if (!message_type)
 			return TRUE;
 	}
@@ -2429,7 +2431,7 @@ static gboolean listener_event(GIOChannel *channel, GIOCondition condition,
 		dhcp_client->timeout = 0;
 		dhcp_client->retry_times = 0;
 
-		option = dhcp_get_option(&packet, DHCP_SERVER_ID);
+		option = dhcp_get_option(&packet, pkt_len, DHCP_SERVER_ID);
 		dhcp_client->server_ip = get_be32(option);
 		dhcp_client->requested_ip = ntohl(packet.yiaddr);
 
@@ -2479,13 +2481,13 @@ static gboolean listener_event(GIOChannel *channel, GIOCondition condition,
 
 			remove_timeouts(dhcp_client);
 
-			dhcp_client->lease_seconds = get_lease(&packet);
+			dhcp_client->lease_seconds = get_lease(&packet, pkt_len);
 
 #if defined TIZEN_EXT
 			dhcp_client->dhcp_lease_seconds = dhcp_client->lease_seconds;
 #endif
 
-			get_request(dhcp_client, &packet);
+			get_request(dhcp_client, &packet, pkt_len);
 
 			switch_listening_mode(dhcp_client, L_NONE);
 
@@ -2493,7 +2495,7 @@ static gboolean listener_event(GIOChannel *channel, GIOCondition condition,
 			dhcp_client->assigned_ip = get_ip(packet.yiaddr);
 
 			if (dhcp_client->state == REBOOTING) {
-				option = dhcp_get_option(&packet,
+				option = dhcp_get_option(&packet, pkt_len,
 							DHCP_SERVER_ID);
 				dhcp_client->server_ip = get_be32(option);
 			}
diff --git a/gdhcp/common.c b/gdhcp/common.c
index 1d667d17..c8916aa8 100755
--- a/gdhcp/common.c
+++ b/gdhcp/common.c
@@ -73,18 +73,21 @@ GDHCPOptionType dhcp_get_code_type(uint8_t code)
 	return OPTION_UNKNOWN;
 }
 
-uint8_t *dhcp_get_option(struct dhcp_packet *packet, int code)
+uint8_t *dhcp_get_option(struct dhcp_packet *packet, uint16_t packet_len, int code)
 {
 	int len, rem;
-	uint8_t *optionptr;
+	uint8_t *optionptr, *options_end;
+	size_t options_len;
 	uint8_t overload = 0;
 
 	/* option bytes: [code][len][data1][data2]..[dataLEN] */
 	optionptr = packet->options;
 	rem = sizeof(packet->options);
+	options_len = packet_len - (sizeof(*packet) - sizeof(packet->options));
+	options_end = optionptr + options_len - 1;
 
 	while (1) {
-		if (rem <= 0)
+		if ((rem <= 0) && (optionptr + OPT_CODE > options_end))
 			/* Bad packet, malformed option field */
 			return NULL;
 
@@ -115,14 +118,25 @@ uint8_t *dhcp_get_option(struct dhcp_packet *packet, int code)
 			break;
 		}
 
+		if (optionptr + OPT_LEN > options_end) {
+			/* bad packet, would read length field from OOB */
+			return NULL;
+		}
+
 		len = 2 + optionptr[OPT_LEN];
 
 		rem -= len;
 		if (rem < 0)
 			continue; /* complain and return NULL */
 
-		if (optionptr[OPT_CODE] == code)
-			return optionptr + OPT_DATA;
+		if (optionptr[OPT_CODE] == code) {
+			if (optionptr + len > options_end) {
+				/* bad packet, option length points OOB */
+				return NULL;
+			} else {
+				return optionptr + OPT_DATA;
+			}
+		}
 
 		if (optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD)
 			overload |= optionptr[OPT_DATA];
diff --git a/gdhcp/common.h b/gdhcp/common.h
index 9660231c..8f63fd75 100755
--- a/gdhcp/common.h
+++ b/gdhcp/common.h
@@ -179,7 +179,7 @@ struct in6_pktinfo {
 };
 #endif
 
-uint8_t *dhcp_get_option(struct dhcp_packet *packet, int code);
+uint8_t *dhcp_get_option(struct dhcp_packet *packet, uint16_t packet_len, int code);
 uint8_t *dhcpv6_get_option(struct dhcpv6_packet *packet, uint16_t pkt_len,
 			int code, uint16_t *option_len, int *option_count);
 uint8_t *dhcpv6_get_sub_option(unsigned char *option, uint16_t max_len,
diff --git a/gdhcp/server.c b/gdhcp/server.c
index 85405f19..52ea2a55 100755
--- a/gdhcp/server.c
+++ b/gdhcp/server.c
@@ -413,7 +413,7 @@ error:
 }
 
 
-static uint8_t check_packet_type(struct dhcp_packet *packet)
+static uint8_t check_packet_type(struct dhcp_packet *packet, uint16_t packet_len)
 {
 	uint8_t *type;
 
@@ -423,7 +423,7 @@ static uint8_t check_packet_type(struct dhcp_packet *packet)
 	if (packet->op != BOOTREQUEST)
 		return 0;
 
-	type = dhcp_get_option(packet, DHCP_MESSAGE_TYPE);
+	type = dhcp_get_option(packet, packet_len, DHCP_MESSAGE_TYPE);
 
 	if (!type)
 		return 0;
@@ -651,6 +651,7 @@ static gboolean listener_event(GIOChannel *channel, GIOCondition condition,
 	struct dhcp_lease *lease;
 	uint32_t requested_nip = 0;
 	uint8_t type, *server_id_option, *request_ip_option;
+	uint16_t packet_len;
 	int re;
 
 	if (condition & (G_IO_NVAL | G_IO_ERR | G_IO_HUP)) {
@@ -661,12 +662,13 @@ static gboolean listener_event(GIOChannel *channel, GIOCondition condition,
 	re = dhcp_recv_l3_packet(&packet, dhcp_server->listener_sockfd);
 	if (re < 0)
 		return TRUE;
+	packet_len = (uint16_t)(unsigned int)re;
 
-	type = check_packet_type(&packet);
+	type = check_packet_type(&packet, packet_len);
 	if (type == 0)
 		return TRUE;
 
-	server_id_option = dhcp_get_option(&packet, DHCP_SERVER_ID);
+	server_id_option = dhcp_get_option(&packet, packet_len, DHCP_SERVER_ID);
 	if (server_id_option) {
 		uint32_t server_nid =
 			get_unaligned((const uint32_t *) server_id_option);
@@ -675,7 +677,7 @@ static gboolean listener_event(GIOChannel *channel, GIOCondition condition,
 			return TRUE;
 	}
 
-	request_ip_option = dhcp_get_option(&packet, DHCP_REQUESTED_IP);
+	request_ip_option = dhcp_get_option(&packet, packet_len, DHCP_REQUESTED_IP);
 	if (request_ip_option)
 		requested_nip = get_be32(request_ip_option);