package/busybox: udhcp CVE-2018-20679 patch

Patch to resolve CVE-2018-20679 which affects versions prior
to 1.30.0

More information can be found at:
https://nvd.nist.gov/vuln/detail/CVE-2018-20679

This applies to both master and 2019.02

Signed-off-by: Jared Bents <jared.bents@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

diff --git a/package/busybox/0004-udhcpc-check-that-4-byte-options-are-indeed-4-byte-closes-11506.patch b/package/busybox/0004-udhcpc-check-that-4-byte-options-are-indeed-4-byte-closes-11506.patch
new file mode 100644 (file)
index 0000000..bc1a48b
--- /dev/null
+++ b/package/busybox/0004-udhcpc-check-that-4-byte-options-are-indeed-4-byte-closes-11506.patch
@@ -0,0 +1,136 @@
+From 6d3b4bb24da9a07c263f3c1acf8df85382ff562c Mon Sep 17 00:00:00 2001
+From: Denys Vlasenko <vda.linux@googlemail.com>
+Date: Mon, 17 Dec 2018 18:07:18 +0100
+Subject: udhcpc: check that 4-byte options are indeed 4-byte, closes 11506
+
+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>
+---
+ networking/udhcp/common.c | 19 +++++++++++++++++++
+ networking/udhcp/common.h |  4 ++++
+ networking/udhcp/dhcpc.c  |  6 +++---
+ networking/udhcp/dhcpd.c  |  6 +++---
+ 4 files changed, 29 insertions(+), 6 deletions(-)
+
+diff --git a/networking/udhcp/common.c b/networking/udhcp/common.c
+index e5fd74f91..41b05b855 100644
+--- a/networking/udhcp/common.c
++++ b/networking/udhcp/common.c
+@@ -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)
+ {
+diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
+index 7ad603d33..9511152ff 100644
+--- a/networking/udhcp/common.h
++++ b/networking/udhcp/common.h
+@@ -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
+diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
+index 4b23e4d39..5b3fd531c 100644
+--- a/networking/udhcp/dhcpc.c
++++ b/networking/udhcp/dhcpc.c
+@@ -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"
+diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c
+index a8cd3f03b..477856d11 100644
+--- a/networking/udhcp/dhcpd.c
++++ b/networking/udhcp/dhcpd.c
+@@ -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);
+               }
+-- 
+cgit v1.2.1
+