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Random code addresses (#5)

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* Enable random addresses for generated code

* Enable custom stack in sandbox

* Triggering CI?

* Update exploit to work in release mode.
This commit is contained in:
Maier Johannes
2024-01-25 01:24:31 +01:00
committed by GitHub
parent b3e3b7b049
commit 01934af8be
2 changed files with 28 additions and 8 deletions
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27
vuln.c
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@@ -158,8 +158,25 @@ int init_seccomp() {
return prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) || prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
}
size_t gen_random_address() {
int rand_fd = open("/dev/random", O_RDONLY);
size_t random_addr;
read(rand_fd, &random_addr, sizeof(random_addr));
close(rand_fd);
return random_addr & 0xFFFFFFFF000;
}
void exec_code(uint8_t *code) {
exec_func_t exec_func = (exec_func_t)code;
register exec_func_t exec_func = (exec_func_t)code;
// allocate a new stack at a random address => no stale addresses left (remember: stack grows down!)
void *custom_stack_addr = (void *)gen_random_address() + 0x1000;
if (mmap(custom_stack_addr - 0x1000, 0x1000, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) == MAP_FAILED) {
puts("Cannot allocate custom stack!");
exit(EXIT_FAILURE);
}
close(0);
close(1);
close(2);
@@ -167,6 +184,7 @@ void exec_code(uint8_t *code) {
puts("Cannot enable seccomp jail!");
exit(EXIT_FAILURE);
}
__asm__ __volatile__("mov %0, %%rsp" : : "r"(custom_stack_addr) : /*"rsp"*/);
uint8_t res = exec_func();
_exit(res);
}
@@ -260,10 +278,11 @@ uint8_t run_jit(Instruction *program, size_t len) {
// page alignment
size_t allocated_code_len = (expected_code_len + 0xFFF) & ~0xFFF;
// TODO: maybe randomly choose address to make exploitation harder
size_t random_addr = gen_random_address();
// allocate memory for context and code
uint8_t *code = (uint8_t *)mmap(NULL, allocated_code_len, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (code == (void *)-1) {
uint8_t *code = (uint8_t *)mmap((void *)random_addr, allocated_code_len, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
if (code == MAP_FAILED) {
puts("Cannot mmap memory for code.");
exit(EXIT_FAILURE);
}