dhcp: add upstream security fixes

CVE-2018-5732: The DHCP client incorrectly handled certain malformed
responses. A remote attacker could use this issue to cause the DHCP
client to crash, resulting in a denial of service, or possibly execute
arbitrary code. In the default installation, attackers would be isolated
by the dhclient AppArmor profile.

CVE-2018-5733: The DHCP server incorrectly handled reference counting. A
remote attacker could possibly use this issue to cause the DHCP server
to crash, resulting in a denial of service.

Both issues are fixed in version 4.4.1. But we are close to release, so
backport the fixes instead of bumping version.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/dhcp/0003-Correct-buffer-overrun-in-pretty_print_option.patch

@@ -0,0 +1,59 @@
+From b8c29336bd5401a5f962bc6ddfa4ebb6f0274f3c Mon Sep 17 00:00:00 2001
+From: Thomas Markwalder <tmark@isc.org>
+Date: Sat, 10 Feb 2018 12:15:27 -0500
+Subject: [PATCH 1/2] Correct buffer overrun in pretty_print_option
+
+    Merges in rt47139.
+
+[baruch: drop RELNOTES and test; address CVE-2018-5732]
+Signed-off-by: Baruch Siach <baruch@tkos.co.il>
+---
+Upstream status: backported from commit c5931725b48
+---
+ common/options.c | 15 ++++++++++++---
+ 1 file changed, 12 insertions(+), 3 deletions(-)
+
+diff --git a/common/options.c b/common/options.c
+index 5547287fb6e5..2ed6b16c6412 100644
+--- a/common/options.c
++++ b/common/options.c
+@@ -1758,7 +1758,8 @@ format_min_length(format, oc)
+ 
+ 
+ /* Format the specified option so that a human can easily read it. */
+-
++/* Maximum pretty printed size */
++#define MAX_OUTPUT_SIZE 32*1024
+ const char *pretty_print_option (option, data, len, emit_commas, emit_quotes)
+ 	struct option *option;
+ 	const unsigned char *data;
+@@ -1766,8 +1767,9 @@ const char *pretty_print_option (option, data, len, emit_commas, emit_quotes)
+ 	int emit_commas;
+ 	int emit_quotes;
+ {
+-	static char optbuf [32768]; /* XXX */
+-	static char *endbuf = &optbuf[sizeof(optbuf)];
++	/* We add 128 byte pad so we don't have to add checks everywhere. */
++	static char optbuf [MAX_OUTPUT_SIZE + 128]; /* XXX */
++	static char *endbuf = optbuf + MAX_OUTPUT_SIZE;
+ 	int hunksize = 0;
+ 	int opthunk = 0;
+ 	int hunkinc = 0;
+@@ -2193,7 +2195,14 @@ const char *pretty_print_option (option, data, len, emit_commas, emit_quotes)
+ 				log_error ("Unexpected format code %c",
+ 					   fmtbuf [j]);
+ 			}
++
+ 			op += strlen (op);
++			if (op >= endbuf) {
++				log_error ("Option data exceeds"
++					   " maximum size %d", MAX_OUTPUT_SIZE);
++					   return ("<error>");
++			}
++
+ 			if (dp == data + len)
+ 				break;
+ 			if (j + 1 < numelem && comma != ':')
+-- 
+2.16.1
+

package/dhcp/0004-Corrected-refcnt-loss-in-option-parsing.patch

@@ -0,0 +1,40 @@
+From 93b5b67dd31b9efcbfaabc2df1e1d9d164a5e04a Mon Sep 17 00:00:00 2001
+From: Thomas Markwalder <tmark@isc.org>
+Date: Fri, 9 Feb 2018 14:46:08 -0500
+Subject: [PATCH 2/2] Corrected refcnt loss in option parsing
+
+    Merges in 47140.
+
+[baruch: drop RELNOTES and tests; address CVE-2018-5733]
+Signed-off-by: Baruch Siach <baruch@tkos.co.il>
+---
+Upstream status: backported from commit 197b26f25309
+---
+ common/options.c | 4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+diff --git a/common/options.c b/common/options.c
+index 2ed6b16c6412..25b29a6be7bb 100644
+--- a/common/options.c
++++ b/common/options.c
+@@ -3,7 +3,7 @@
+    DHCP options parsing and reassembly. */
+ 
+ /*
+- * Copyright (c) 2004-2017 by Internet Systems Consortium, Inc. ("ISC")
++ * Copyright (c) 2004-2018 by Internet Systems Consortium, Inc. ("ISC")
+  * Copyright (c) 1995-2003 by Internet Software Consortium
+  *
+  * Permission to use, copy, modify, and distribute this software for any
+@@ -177,6 +177,8 @@ int parse_option_buffer (options, buffer, length, universe)
+ 
+ 		/* If the length is outrageous, the options are bad. */
+ 		if (offset + len > length) {
++			/* Avoid reference count overflow */
++			option_dereference(&option, MDL);
+ 			reason = "option length exceeds option buffer length";
+ 		      bogus:
+ 			log_error("parse_option_buffer: malformed option "
+-- 
+2.16.1
+