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

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function                                             old     new   delta
udhcp_get_option32                                     -      27     +27
udhcp_get_option                                     231     248     +17
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/0 up/down: 44/0)               Total: 44 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2018-12-17 18:07:18 +01:00
parent 4b72aebe80
commit 6d3b4bb24d
4 changed files with 29 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
networking/udhcp/common.c
View File

@ -272,6 +272,15 @@ uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
goto complain; /* complain and return NULL */ goto complain; /* complain and return NULL */
if (optionptr[OPT_CODE] == code) { 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); log_option("option found", optionptr);
return optionptr + OPT_DATA; return optionptr + OPT_DATA;
} }
@ -289,6 +298,16 @@ uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
return NULL; 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) */ /* Return the position of the 'end' option (no bounds checking) */
int FAST_FUNC udhcp_end_option(uint8_t *optionptr) int FAST_FUNC udhcp_end_option(uint8_t *optionptr)
{ {

4
networking/udhcp/common.h
View File

@ -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); 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; 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; int udhcp_end_option(uint8_t *optionptr) FAST_FUNC;
void udhcp_add_binary_option(struct dhcp_packet *packet, uint8_t *addopt) FAST_FUNC; void udhcp_add_binary_option(struct dhcp_packet *packet, uint8_t *addopt) FAST_FUNC;
#if ENABLE_UDHCPC || ENABLE_UDHCPD #if ENABLE_UDHCPC || ENABLE_UDHCPD

6
networking/udhcp/dhcpc.c
View File

@ -1691,7 +1691,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
* They say ISC DHCP client supports this case. * They say ISC DHCP client supports this case.
*/ */
server_addr = 0; server_addr = 0;
temp = udhcp_get_option(&packet, DHCP_SERVER_ID); temp = udhcp_get_option32(&packet, DHCP_SERVER_ID);
if (!temp) { if (!temp) {
bb_error_msg("no server ID, using 0.0.0.0"); bb_error_msg("no server ID, using 0.0.0.0");
} else { } else {
@ -1718,7 +1718,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
struct in_addr temp_addr; struct in_addr temp_addr;
uint8_t *temp; uint8_t *temp;
temp = udhcp_get_option(&packet, DHCP_LEASE_TIME); temp = udhcp_get_option32(&packet, DHCP_LEASE_TIME);
if (!temp) { if (!temp) {
bb_error_msg("no lease time with ACK, using 1 hour lease"); bb_error_msg("no lease time with ACK, using 1 hour lease");
lease_seconds = 60 * 60; lease_seconds = 60 * 60;
@ -1813,7 +1813,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
uint32_t svid; uint32_t svid;
uint8_t *temp; uint8_t *temp;
temp = udhcp_get_option(&packet, DHCP_SERVER_ID); temp = udhcp_get_option32(&packet, DHCP_SERVER_ID);
if (!temp) { if (!temp) {
non_matching_svid: non_matching_svid:
log1("received DHCP NAK with wrong" log1("received DHCP NAK with wrong"

6
networking/udhcp/dhcpd.c
View File

@ -640,7 +640,7 @@ static void add_server_options(struct dhcp_packet *packet)
static uint32_t select_lease_time(struct dhcp_packet *packet) static uint32_t select_lease_time(struct dhcp_packet *packet)
{ {
uint32_t lease_time_sec = server_config.max_lease_sec; 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) { if (lease_time_opt) {
move_from_unaligned32(lease_time_sec, lease_time_opt); move_from_unaligned32(lease_time_sec, lease_time_opt);
lease_time_sec = ntohl(lease_time_sec); 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 */ /* 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) { if (server_id_opt) {
uint32_t server_id_network_order; uint32_t server_id_network_order;
move_from_unaligned32(server_id_network_order, server_id_opt); 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 */ /* 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) { if (requested_ip_opt) {
move_from_unaligned32(requested_nip, requested_ip_opt); move_from_unaligned32(requested_nip, requested_ip_opt);
} }