6d3b4bb24

Denys Vlasenko

2018-12-17

SUCCESS Duration: 153s

Subject

udhcpc: check that 4-byte options are indeed 4-byte, closes 11506

No binary (build failed)

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

(log yok)

networking/udhcp/common.c+19 -0

@@ -272,6 +272,15 @@ uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
	goto complain; /* complain and return NULL */

	if (optionptr[OPT_CODE] == code) {
+	if (optionptr[OPT_LEN] == 0) {
+	/* So far no valid option with length 0 known.
+	* Having this check means that searching
+	* for DHCP_MESSAGE_TYPE need not worry
+	* that returned pointer might be unsafe
+	* to dereference.
+	*/
+	goto complain; /* complain and return NULL */
+	}
	log_option("option found", optionptr);
	return optionptr + OPT_DATA;
	}
@@ -289,6 +298,16 @@ uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
	return NULL;
	}

+	uint8_t* FAST_FUNC udhcp_get_option32(struct dhcp_packet *packet, int code)
+	{
+	uint8_t *r = udhcp_get_option(packet, code);
+	if (r) {
+	if (r[-1] != 4)
+	r = NULL;
+	}
+	return r;
+	}
+
	/* Return the position of the 'end' option (no bounds checking) */
	int FAST_FUNC udhcp_end_option(uint8_t *optionptr)
	{

networking/udhcp/common.h+4 -0

@@ -205,6 +205,10 @@ extern const uint8_t dhcp_option_lengths[] ALIGN1;
	unsigned FAST_FUNC udhcp_option_idx(const char name, const char option_strings);

	uint8_t udhcp_get_option(struct dhcp_packet packet, int code) FAST_FUNC;
+	/* Same as above + ensures that option length is 4 bytes
+	* (returns NULL if size is different)
+	*/
+	uint8_t udhcp_get_option32(struct dhcp_packet packet, int code) FAST_FUNC;
	int udhcp_end_option(uint8_t *optionptr) FAST_FUNC;
	void udhcp_add_binary_option(struct dhcp_packet packet, uint8_t addopt) FAST_FUNC;
	#if ENABLE_UDHCPC \|\| ENABLE_UDHCPD

networking/udhcp/dhcpc.c+3 -3

@@ -1691,7 +1691,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
	* They say ISC DHCP client supports this case.
	*/
	server_addr = 0;
-	temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
+	temp = udhcp_get_option32(&packet, DHCP_SERVER_ID);
	if (!temp) {
	bb_error_msg("no server ID, using 0.0.0.0");
	} else {
@@ -1718,7 +1718,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
	struct in_addr temp_addr;
	uint8_t *temp;

-	temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
+	temp = udhcp_get_option32(&packet, DHCP_LEASE_TIME);
	if (!temp) {
	bb_error_msg("no lease time with ACK, using 1 hour lease");
	lease_seconds = 60 * 60;
@@ -1813,7 +1813,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
	uint32_t svid;
	uint8_t *temp;

-	temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
+	temp = udhcp_get_option32(&packet, DHCP_SERVER_ID);
	if (!temp) {
	non_matching_svid:
	log1("received DHCP NAK with wrong"

networking/udhcp/dhcpd.c+3 -3

@@ -640,7 +640,7 @@ static void add_server_options(struct dhcp_packet *packet)
	static uint32_t select_lease_time(struct dhcp_packet *packet)
	{
	uint32_t lease_time_sec = server_config.max_lease_sec;
-	uint8_t *lease_time_opt = udhcp_get_option(packet, DHCP_LEASE_TIME);
+	uint8_t *lease_time_opt = udhcp_get_option32(packet, DHCP_LEASE_TIME);
	if (lease_time_opt) {
	move_from_unaligned32(lease_time_sec, lease_time_opt);
	lease_time_sec = ntohl(lease_time_sec);
@@ -987,7 +987,7 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
	}

	/* Get SERVER_ID if present */
-	server_id_opt = udhcp_get_option(&packet, DHCP_SERVER_ID);
+	server_id_opt = udhcp_get_option32(&packet, DHCP_SERVER_ID);
	if (server_id_opt) {
	uint32_t server_id_network_order;
	move_from_unaligned32(server_id_network_order, server_id_opt);
@@ -1011,7 +1011,7 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
	}

	/* Get REQUESTED_IP if present */
-	requested_ip_opt = udhcp_get_option(&packet, DHCP_REQUESTED_IP);
+	requested_ip_opt = udhcp_get_option32(&packet, DHCP_REQUESTED_IP);
	if (requested_ip_opt) {
	move_from_unaligned32(requested_nip, requested_ip_opt);
	}