syzkaller/executor/common_bsd.h
Dmitry Vyukov a6e3054436 executor: rename some macros
Rename some macros in preparation for subsequent changes
which will align names across the code base.
2019-11-16 09:58:54 +01:00

407 lines
11 KiB
C

// Copyright 2017 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
// This file is shared between executor and csource package.
#include <unistd.h>
#include <pwd.h>
#include <stdarg.h>
#include <stdbool.h>
#include <string.h>
#include <sys/syscall.h>
#if GOOS_openbsd
#define __syscall syscall
#if SYZ_EXECUTOR || __NR_syz_open_pts
#include <termios.h>
#include <util.h>
static uintptr_t syz_open_pts(void)
{
int master, slave;
if (openpty(&master, &slave, NULL, NULL, NULL) == -1)
return -1;
// Move the master fd up in order to reduce the chances of the fuzzer
// generating a call to close(2) with the same fd.
if (dup2(master, master + 100) != -1)
close(master);
return slave;
}
#endif // SYZ_EXECUTOR || __NR_syz_open_pts
#endif // GOOS_openbsd
#if SYZ_EXECUTOR || SYZ_NET_INJECTION
#include <fcntl.h>
#include <net/if_tun.h>
#include <sys/types.h>
static int tunfd = -1;
#if GOOS_netbsd
// Increased number of tap and tun devices if image script is used
#define MAX_TUN 64
#else
// Maximum number of tun devices in the default install.
#define MAX_TUN 4
#endif
// All patterns are non-expanding given values < MAX_TUN.
#define TUN_IFACE "tap%d"
#define TUN_DEVICE "/dev/tap%d"
#define LOCAL_MAC "aa:aa:aa:aa:aa:aa"
#define REMOTE_MAC "aa:aa:aa:aa:aa:bb"
#define LOCAL_IPV4 "172.20.%d.170"
#define REMOTE_IPV4 "172.20.%d.187"
#define LOCAL_IPV6 "fe80::%02hxaa"
#define REMOTE_IPV6 "fe80::%02hxbb"
static void vsnprintf_check(char* str, size_t size, const char* format, va_list args)
{
int rv;
rv = vsnprintf(str, size, format, args);
if (rv < 0)
fail("vsnprintf failed");
if ((size_t)rv >= size)
fail("vsnprintf: string '%s...' doesn't fit into buffer", str);
}
static void snprintf_check(char* str, size_t size, const char* format, ...)
{
va_list args;
va_start(args, format);
vsnprintf_check(str, size, format, args);
va_end(args);
}
#define COMMAND_MAX_LEN 128
#define PATH_PREFIX "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin "
#define PATH_PREFIX_LEN (sizeof(PATH_PREFIX) - 1)
static void execute_command(bool panic, const char* format, ...)
{
va_list args;
char command[PATH_PREFIX_LEN + COMMAND_MAX_LEN];
int rv;
va_start(args, format);
// Executor process does not have any env, including PATH.
// On some distributions, system/shell adds a minimal PATH, on some it does not.
// Set own standard PATH to make it work across distributions.
memcpy(command, PATH_PREFIX, PATH_PREFIX_LEN);
vsnprintf_check(command + PATH_PREFIX_LEN, COMMAND_MAX_LEN, format, args);
va_end(args);
rv = system(command);
if (rv) {
if (panic)
fail("command '%s' failed: %d", &command[0], rv);
debug("command '%s': %d\n", &command[0], rv);
}
}
static void initialize_tun(int tun_id)
{
#if SYZ_EXECUTOR
if (!flag_net_injection)
return;
#endif // SYZ_EXECUTOR
if (tun_id < 0 || tun_id >= MAX_TUN) {
fail("tun_id out of range %d\n", tun_id);
}
char tun_device[sizeof(TUN_DEVICE)];
snprintf_check(tun_device, sizeof(tun_device), TUN_DEVICE, tun_id);
char tun_iface[sizeof(TUN_IFACE)];
snprintf_check(tun_iface, sizeof(tun_iface), TUN_IFACE, tun_id);
#if GOOS_netbsd
// open(2) doesn't create an new tap/tun interface node
// so we use ifconfig to create the node. Might be casued due to regression
execute_command(0, "ifconfig %s destroy", tun_iface);
execute_command(0, "ifconfig %s create", tun_iface);
#else
execute_command(0, "ifconfig %s destroy", tun_device);
#endif
tunfd = open(tun_device, O_RDWR | O_NONBLOCK);
#if GOOS_freebsd
if ((tunfd < 0) && (errno == ENOENT)) {
execute_command(0, "kldload -q if_tap");
tunfd = open(tun_device, O_RDWR | O_NONBLOCK);
}
#endif
if (tunfd == -1) {
#if SYZ_EXECUTOR
fail("tun: can't open %s\n", tun_device);
#else
printf("tun: can't open %s: errno=%d\n", tun_device, errno);
return;
#endif // SYZ_EXECUTOR
}
// Remap tun onto higher fd number to hide it from fuzzer and to keep
// fd numbers stable regardless of whether tun is opened or not (also see kMaxFd).
const int kTunFd = 240;
if (dup2(tunfd, kTunFd) < 0)
fail("dup2(tunfd, kTunFd) failed");
close(tunfd);
tunfd = kTunFd;
char local_mac[sizeof(LOCAL_MAC)];
snprintf_check(local_mac, sizeof(local_mac), LOCAL_MAC);
// Set the MAC address of the interface to LOCAL_MAC
#if GOOS_openbsd
execute_command(1, "ifconfig %s lladdr %s", tun_iface, local_mac);
#elif GOOS_netbsd
execute_command(1, "ifconfig %s link %s", tun_iface, local_mac);
#else
execute_command(1, "ifconfig %s ether %s", tun_iface, local_mac);
#endif
// Setting up a static ip for the interface
char local_ipv4[sizeof(LOCAL_IPV4)];
snprintf_check(local_ipv4, sizeof(local_ipv4), LOCAL_IPV4, tun_id);
execute_command(1, "ifconfig %s inet %s netmask 255.255.255.0", tun_iface, local_ipv4);
// Creates an ARP table entry for the remote ip and MAC address
char remote_mac[sizeof(REMOTE_MAC)];
char remote_ipv4[sizeof(REMOTE_IPV4)];
snprintf_check(remote_mac, sizeof(remote_mac), REMOTE_MAC);
snprintf_check(remote_ipv4, sizeof(remote_ipv4), REMOTE_IPV4, tun_id);
execute_command(0, "arp -s %s %s", remote_ipv4, remote_mac);
// Set up a static ipv6 address for the interface
char local_ipv6[sizeof(LOCAL_IPV6)];
snprintf_check(local_ipv6, sizeof(local_ipv6), LOCAL_IPV6, tun_id);
execute_command(1, "ifconfig %s inet6 %s", tun_iface, local_ipv6);
// Registers an NDP entry for the remote MAC with the remote ipv6 address
char remote_ipv6[sizeof(REMOTE_IPV6)];
snprintf_check(remote_ipv6, sizeof(remote_ipv6), REMOTE_IPV6, tun_id);
execute_command(0, "ndp -s %s%%%s %s", remote_ipv6, tun_iface, remote_mac);
}
#endif // SYZ_EXECUTOR || SYZ_NET_INJECTION
#if SYZ_EXECUTOR || __NR_syz_emit_ethernet && SYZ_NET_INJECTION
#include <stdbool.h>
#include <sys/uio.h>
static long syz_emit_ethernet(volatile long a0, volatile long a1)
{
// syz_emit_ethernet(len len[packet], packet ptr[in, array[int8]])
if (tunfd < 0)
return (uintptr_t)-1;
size_t length = a0;
const char* data = (char*)a1;
debug_dump_data(data, length);
return write(tunfd, data, length);
}
#endif
#if SYZ_EXECUTOR || SYZ_NET_INJECTION && (__NR_syz_extract_tcp_res || SYZ_REPEAT)
#include <errno.h>
static int read_tun(char* data, int size)
{
if (tunfd < 0)
return -1;
int rv = read(tunfd, data, size);
if (rv < 0) {
if (errno == EAGAIN)
return -1;
fail("tun: read failed with %d", rv);
}
return rv;
}
#endif
#if SYZ_EXECUTOR || __NR_syz_extract_tcp_res && SYZ_NET_INJECTION
struct tcp_resources {
uint32 seq;
uint32 ack;
};
#if GOOS_freebsd
#include <net/ethernet.h>
#else
#include <net/ethertypes.h>
#endif
#include <net/if.h>
#include <net/if_arp.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/tcp.h>
// Include order matters, empty line prevent re-sorting. See a workaround in
// pkg/csource hoistIncludes.
#include <netinet/if_ether.h>
static long syz_extract_tcp_res(volatile long a0, volatile long a1, volatile long a2)
{
// syz_extract_tcp_res(res ptr[out, tcp_resources], seq_inc int32, ack_inc int32)
if (tunfd < 0)
return (uintptr_t)-1;
// We just need this to be large enough to hold headers that we parse (ethernet/ip/tcp).
// Rest of the packet (if any) will be silently truncated which is fine.
char data[1000];
int rv = read_tun(&data[0], sizeof(data));
if (rv == -1)
return (uintptr_t)-1;
size_t length = rv;
debug_dump_data(data, length);
struct tcphdr* tcphdr;
if (length < sizeof(struct ether_header))
return (uintptr_t)-1;
struct ether_header* ethhdr = (struct ether_header*)&data[0];
if (ethhdr->ether_type == htons(ETHERTYPE_IP)) {
if (length < sizeof(struct ether_header) + sizeof(struct ip))
return (uintptr_t)-1;
struct ip* iphdr = (struct ip*)&data[sizeof(struct ether_header)];
if (iphdr->ip_p != IPPROTO_TCP)
return (uintptr_t)-1;
if (length < sizeof(struct ether_header) + iphdr->ip_hl * 4 + sizeof(struct tcphdr))
return (uintptr_t)-1;
tcphdr = (struct tcphdr*)&data[sizeof(struct ether_header) + iphdr->ip_hl * 4];
} else {
if (length < sizeof(struct ether_header) + sizeof(struct ip6_hdr))
return (uintptr_t)-1;
struct ip6_hdr* ipv6hdr = (struct ip6_hdr*)&data[sizeof(struct ether_header)];
// TODO: parse and skip extension headers.
if (ipv6hdr->ip6_nxt != IPPROTO_TCP)
return (uintptr_t)-1;
if (length < sizeof(struct ether_header) + sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
return (uintptr_t)-1;
tcphdr = (struct tcphdr*)&data[sizeof(struct ether_header) + sizeof(struct ip6_hdr)];
}
struct tcp_resources* res = (struct tcp_resources*)a0;
NONFAILING(res->seq = htonl((ntohl(tcphdr->th_seq) + (uint32)a1)));
NONFAILING(res->ack = htonl((ntohl(tcphdr->th_ack) + (uint32)a2)));
debug("extracted seq: %08x\n", res->seq);
debug("extracted ack: %08x\n", res->ack);
return 0;
}
#endif
#if SYZ_EXECUTOR || SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NONE
#include <sys/resource.h>
#include <unistd.h>
static void sandbox_common()
{
if (setsid() == -1)
fail("setsid failed");
// Some minimal sandboxing.
struct rlimit rlim;
#ifdef GOOS_freebsd
// Documented bug in OpenBSD.
// This causes frequent random aborts. Reason unknown.
// This also causes ENOMEM on NetBSD during early init.
rlim.rlim_cur = rlim.rlim_max = 128 << 20;
setrlimit(RLIMIT_AS, &rlim);
#endif
rlim.rlim_cur = rlim.rlim_max = 8 << 20;
setrlimit(RLIMIT_MEMLOCK, &rlim);
rlim.rlim_cur = rlim.rlim_max = 1 << 20;
setrlimit(RLIMIT_FSIZE, &rlim);
rlim.rlim_cur = rlim.rlim_max = 1 << 20;
setrlimit(RLIMIT_STACK, &rlim);
rlim.rlim_cur = rlim.rlim_max = 0;
setrlimit(RLIMIT_CORE, &rlim);
rlim.rlim_cur = rlim.rlim_max = 256; // see kMaxFd
setrlimit(RLIMIT_NOFILE, &rlim);
}
#endif // SYZ_EXECUTOR || SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NONE
#if SYZ_EXECUTOR || SYZ_SANDBOX_NONE
static void loop();
static int do_sandbox_none(void)
{
sandbox_common();
#if SYZ_EXECUTOR || SYZ_NET_INJECTION
initialize_tun(procid);
#endif
loop();
return 0;
}
#endif // SYZ_EXECUTOR || SYZ_SANDBOX_NONE
#if SYZ_EXECUTOR || SYZ_SANDBOX_SETUID
#include <sys/resource.h>
#include <sys/wait.h>
#include <unistd.h>
static void loop();
static int wait_for_loop(int pid)
{
if (pid < 0)
fail("sandbox fork failed");
debug("spawned loop pid %d\n", pid);
int status = 0;
while (waitpid(-1, &status, WUNTRACED) != pid) {
}
return WEXITSTATUS(status);
}
#define SYZ_HAVE_SANDBOX_SETUID 1
static int do_sandbox_setuid(void)
{
int pid = fork();
if (pid != 0)
return wait_for_loop(pid);
sandbox_common();
#if SYZ_EXECUTOR || SYZ_NET_INJECTION
initialize_tun(procid);
#endif
char pwbuf[1024];
struct passwd *pw, pwres;
if (getpwnam_r("nobody", &pwres, pwbuf, sizeof(pwbuf), &pw) != 0 || !pw)
fail("getpwnam_r(\"nobody\") failed");
if (setgroups(0, NULL))
fail("failed to setgroups");
if (setgid(pw->pw_gid))
fail("failed to setgid");
if (setuid(pw->pw_uid))
fail("failed to setuid");
loop();
doexit(1);
}
#endif // SYZ_EXECUTOR || SYZ_SANDBOX_SETUID