tests: add libFuzzer based fuzzing

LibFuzzer is in-process, coverage-guided, evolutionary fuzzing engine.

LibFuzzer is linked with the library under test, and feeds fuzzed inputs
to the library via a specific fuzzing entrypoint (aka "target
function"); the fuzzer then tracks which areas of the code are reached,
and generates mutations on the corpus of input data in order to maximize
the code coverage.

So lets use libFuzzer to fuzz uci_import for the start.

Ref: https://llvm.org/docs/LibFuzzer.html
Signed-off-by: Petr Štetiar <ynezz@true.cz>

tests/CMakeLists.txt

@@ -1,2 +1,6 @@
 ADD_SUBDIRECTORY(cram)
 ADD_SUBDIRECTORY(shunit2)
+
+IF(CMAKE_C_COMPILER_ID STREQUAL "Clang")
+  ADD_SUBDIRECTORY(fuzz)
+ENDIF()

tests/fuzz/CMakeLists.txt

@@ -0,0 +1,18 @@
+FILE(GLOB test_cases "test-*.c")
+
+MACRO(ADD_FUZZER_TEST name)
+  ADD_EXECUTABLE(${name} ${name}.c)
+  TARGET_COMPILE_OPTIONS(${name} PRIVATE -g -O1 -fno-omit-frame-pointer -fsanitize=fuzzer,address,leak,undefined)
+  TARGET_INCLUDE_DIRECTORIES(${name} PRIVATE ${PROJECT_SOURCE_DIR})
+  TARGET_LINK_OPTIONS(${name} PRIVATE -stdlib=libc++ -fsanitize=fuzzer,address,leak,undefined)
+  TARGET_LINK_LIBRARIES(${name} uci)
+  ADD_TEST(
+    NAME ${name}
+	COMMAND ${name} -max_len=256 -timeout=10 -max_total_time=300 -dict=${CMAKE_CURRENT_SOURCE_DIR}/dict/uci.dict ${CMAKE_CURRENT_SOURCE_DIR}/corpus
+  )
+ENDMACRO(ADD_FUZZER_TEST)
+
+FOREACH(test_case ${test_cases})
+  GET_FILENAME_COMPONENT(test_case ${test_case} NAME_WE)
+  ADD_FUZZER_TEST(${test_case})
+ENDFOREACH(test_case)

tests/fuzz/corpus/51045ac5401085f5727c6d3c1cac5f8cc32a2927

@@ -0,0 +1 @@
+ #

tests/fuzz/corpus/bb589d0621e5472f470fa3425a234c74b1e202e8

@@ -0,0 +1 @@
+'

tests/fuzz/dict/uci.dict

@@ -0,0 +1,18 @@
+"c"
+"config"
+"p"
+"package"
+"o"
+"option"
+"l"
+"list"
+"'"
+"\""
+" "
+"\x00"
+"\x0a"
+"\x0d"
+"\x09"
+"#"
+";"
+"\\"

tests/fuzz/inputs/dhcp

@@ -0,0 +1,49 @@
+
+config dnsmasq
+	option domainneeded '1'
+	option boguspriv '1'
+	option filterwin2k '0'
+	option localise_queries '1'
+	option rebind_protection '1'
+	option rebind_localhost '1'
+	option local '/lan/'
+	option domain 'lan'
+	option expandhosts '1'
+	option nonegcache '0'
+	option authoritative '1'
+	option readethers '1'
+	option leasefile '/tmp/dhcp.leases'
+	option resolvfile '/tmp/resolv.conf.d/resolv.conf.auto'
+	option nonwildcard '1'
+	option localservice '1'
+
+config dhcp 'lan'
+	option interface 'lan'
+	option start '100'
+	option limit '150'
+	option leasetime '12h'
+	option dhcpv6 'server'
+	option ra 'server'
+	option ra_slaac '1'
+	list ra_flags 'managed-config'
+	list ra_flags 'other-config'
+
+config dhcp 'wan'
+	option interface 'wan'
+	option ignore '1'
+
+config odhcpd 'odhcpd'
+	option maindhcp '0'
+	option leasefile '/tmp/hosts/odhcpd'
+	option leasetrigger '/usr/sbin/odhcpd-update'
+	option loglevel '4'
+
+config host
+        option name 'foo'
+        option ip '192.168.1.90'
+        option mac '20:de:ad:be:ef:99'
+
+config host
+        option name 'moo-ap01'
+        option ip '192.168.1.2'
+        option mac '00:dd:8d:f7:e6:6f'

tests/fuzz/inputs/firewall

@@ -0,0 +1,208 @@
+config defaults
+	option syn_flood	1
+	option input		ACCEPT
+	option output		ACCEPT
+	option forward		REJECT
+# Uncomment this line to disable ipv6 rules
+#	option disable_ipv6	1
+
+config zone
+	option name		lan
+	list   network		'lan'
+	option input		ACCEPT
+	option output		ACCEPT
+	option forward		ACCEPT
+
+config zone
+	option name		wan
+	list   network		'wan'
+	list   network		'wan6'
+	option input		REJECT
+	option output		ACCEPT
+	option forward		REJECT
+	option masq		1
+	option mtu_fix		1
+
+config forwarding
+	option src		lan
+	option dest		wan
+
+# We need to accept udp packets on port 68,
+# see https://dev.openwrt.org/ticket/4108
+config rule
+	option name		Allow-DHCP-Renew
+	option src		wan
+	option proto		udp
+	option dest_port	68
+	option target		ACCEPT
+	option family		ipv4
+
+# Allow IPv4 ping
+config rule
+	option name		Allow-Ping
+	option src		wan
+	option proto		icmp
+	option icmp_type	echo-request
+	option family		ipv4
+	option target		ACCEPT
+
+config rule
+	option name		Allow-IGMP
+	option src		wan
+	option proto		igmp
+	option family		ipv4
+	option target		ACCEPT
+
+# Allow DHCPv6 replies
+# see https://dev.openwrt.org/ticket/10381
+config rule
+	option name		Allow-DHCPv6
+	option src		wan
+	option proto		udp
+	option src_ip		fc00::/6
+	option dest_ip		fc00::/6
+	option dest_port	546
+	option family		ipv6
+	option target		ACCEPT
+
+config rule
+	option name		Allow-MLD
+	option src		wan
+	option proto		icmp
+	option src_ip		fe80::/10
+	list icmp_type		'130/0'
+	list icmp_type		'131/0'
+	list icmp_type		'132/0'
+	list icmp_type		'143/0'
+	option family		ipv6
+	option target		ACCEPT
+
+# Allow essential incoming IPv6 ICMP traffic
+config rule
+	option name		Allow-ICMPv6-Input
+	option src		wan
+	option proto	icmp
+	list icmp_type		echo-request
+	list icmp_type		echo-reply
+	list icmp_type		destination-unreachable
+	list icmp_type		packet-too-big
+	list icmp_type		time-exceeded
+	list icmp_type		bad-header
+	list icmp_type		unknown-header-type
+	list icmp_type		router-solicitation
+	list icmp_type		neighbour-solicitation
+	list icmp_type		router-advertisement
+	list icmp_type		neighbour-advertisement
+	option limit		1000/sec
+	option family		ipv6
+	option target		ACCEPT
+
+# Allow essential forwarded IPv6 ICMP traffic
+config rule
+	option name		Allow-ICMPv6-Forward
+	option src		wan
+	option dest		*
+	option proto		icmp
+	list icmp_type		echo-request
+	list icmp_type		echo-reply
+	list icmp_type		destination-unreachable
+	list icmp_type		packet-too-big
+	list icmp_type		time-exceeded
+	list icmp_type		bad-header
+	list icmp_type		unknown-header-type
+	option limit		1000/sec
+	option family		ipv6
+	option target		ACCEPT
+
+config rule
+	option name		Allow-IPSec-ESP
+	option src		wan
+	option dest		lan
+	option proto		esp
+	option target		ACCEPT
+
+config rule
+	option name		Allow-ISAKMP
+	option src		wan
+	option dest		lan
+	option dest_port	500
+	option proto		udp
+	option target		ACCEPT
+
+# allow interoperability with traceroute classic
+# note that traceroute uses a fixed port range, and depends on getting
+# back ICMP Unreachables.  if we're operating in DROP mode, it won't
+# work so we explicitly REJECT packets on these ports.
+config rule
+	option name		Support-UDP-Traceroute
+	option src		wan
+	option dest_port	33434:33689
+	option proto		udp
+	option family		ipv4
+	option target		REJECT
+	option enabled		false
+
+# include a file with users custom iptables rules
+config include
+	option path /etc/firewall.user
+
+
+### EXAMPLE CONFIG SECTIONS
+# do not allow a specific ip to access wan
+#config rule
+#	option src		lan
+#	option src_ip	192.168.45.2
+#	option dest		wan
+#	option proto	tcp
+#	option target	REJECT
+
+# block a specific mac on wan
+#config rule
+#	option dest		wan
+#	option src_mac	00:11:22:33:44:66
+#	option target	REJECT
+
+# block incoming ICMP traffic on a zone
+#config rule
+#	option src		lan
+#	option proto	ICMP
+#	option target	DROP
+
+# port redirect port coming in on wan to lan
+#config redirect
+#	option src			wan
+#	option src_dport	80
+#	option dest			lan
+#	option dest_ip		192.168.16.235
+#	option dest_port	80
+#	option proto		tcp
+
+# port redirect of remapped ssh port (22001) on wan
+#config redirect
+#	option src		wan
+#	option src_dport	22001
+#	option dest		lan
+#	option dest_port	22
+#	option proto		tcp
+
+### FULL CONFIG SECTIONS
+#config rule
+#	option src		lan
+#	option src_ip	192.168.45.2
+#	option src_mac	00:11:22:33:44:55
+#	option src_port	80
+#	option dest		wan
+#	option dest_ip	194.25.2.129
+#	option dest_port	120
+#	option proto	tcp
+#	option target	REJECT
+
+#config redirect
+#	option src		lan
+#	option src_ip	192.168.45.2
+#	option src_mac	00:11:22:33:44:55
+#	option src_port		1024
+#	option src_dport	80
+#	option dest_ip	194.25.2.129
+#	option dest_port	120
+#	option proto	tcp

tests/fuzz/test-fuzz.c

@@ -0,0 +1,60 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "uci.h"
+
+static void fuzz_uci_import(const uint8_t *input, size_t size)
+{
+	int r;
+	int fd;
+	FILE *fs = NULL;
+	struct uci_context *ctx = NULL;
+	struct uci_package *package = NULL;
+
+	fd = open("/dev/shm", O_TMPFILE | O_RDWR, S_IRUSR | S_IWUSR);
+	if (fd < 0) {
+		perror("unable to create temp file");
+		exit(-1);
+	}
+
+	r = write(fd, input, size);
+	if (r < 0) {
+		perror("unable to write()");
+		exit(-1);
+	}
+
+	fs = fdopen(fd, "r");
+	if (fs == NULL) {
+		perror("unable to fdopen()");
+		exit(-1);
+	}
+
+	fseek(fs, 0L, SEEK_SET);
+
+	ctx = uci_alloc_context();
+	if (ctx == NULL) {
+		perror("unable to uci_alloc_context()");
+		exit(-1);
+	}
+
+	uci_import(ctx, fs, NULL, &package, false);
+	uci_free_context(ctx);
+	close(fd);
+	fclose(fs);
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *input, size_t size)
+{
+	fuzz_uci_import(input, size);
+	return 0;
+}