Spoof All Domains Containing ‘d’ in Apple Products [CVE-2018-4277]

During this time I have been researching security issues on the browser front end, and I have found dozens of vulnerabilities in browsers such as Chrome, Safari, and Firefox. Unicode visual security and IDN homograph attack have also been the subject of my research.

Evil U+A771

In my research, I found Latin small letter dum (U+A771) glyph is very similar to Latin small letter D (U+0064) in Apple products. From the glyph standard of Unicode (U+A771), we can see that there should be a small apostrophe after d, but this is completely ignored in Apple products.


Continue reading “Spoof All Domains Containing ‘d’ in Apple Products [CVE-2018-4277]”

Pay attention to the Ethereum hash collision problem from the “Stealing coins” incident

Author : Kai Song(exp-sky) , hearmen , salt , sekaiwu of Tencent Security Xuanwu Lab

“Stealing coins”

On November 6th, we observed that such a contract appeared on Ethereum. After investigation, it was found that a blockchain security vendor issued a contract to let everyone “Stealing coins”.

pragma solidity ^0.4.21;
contract DVPgame {
    ERC20 public token;
    uint256[] map;
    using SafeERC20 for ERC20;
    using SafeMath for uint256;
    constructor(address addr) payable{
        token = ERC20(addr);
    }
    function (){
        if(map.length>=uint256(msg.sender)){
            require(map[uint256(msg.sender)]!=1);
        }
        if(token.balanceOf(this)==0){
            //airdrop is over
            selfdestruct(msg.sender);
        }else{
            token.safeTransfer(msg.sender,100);

            if (map.length <= uint256(msg.sender)) {
                map.length = uint256(msg.sender) + 1;
            }
            map[uint256(msg.sender)] = 1;  

        }
    }
    //Guess the value(param:x) of the keccak256 value modulo 10000 of the future block (param:blockNum)
    function guess(uint256 x,uint256 blockNum) public payable {
        require(msg.value == 0.001 ether || token.allowance(msg.sender,address(this))>=1*(10**18));
        require(blockNum>block.number);
        if(token.allowance(msg.sender,address(this))>0){
            token.safeTransferFrom(msg.sender,address(this),1*(10**18));
        }
        if (map.length <= uint256(msg.sender)+x) {
            map.length = uint256(msg.sender)+x + 1;
        }

        map[uint256(msg.sender)+x] = blockNum;
    }
    //Run a lottery
    function lottery(uint256 x) public {
        require(map[uint256(msg.sender)+x]!=0);
        require(block.number > map[uint256(msg.sender)+x]);
        require(block.blockhash(map[uint256(msg.sender)+x])!=0);
        uint256 answer = uint256(keccak256(block.blockhash(map[uint256(msg.sender)+x])))%10000;
        if (x == answer) {
            token.safeTransfer(msg.sender,token.balanceOf(address(this)));
            selfdestruct(msg.sender);
        }
    }
}

After observing, we found the security issue of an EVM storage we studied earlier in this contract, namely the hash collision problem in EVM storage.

Continue reading “Pay attention to the Ethereum hash collision problem from the “Stealing coins” incident”

Pwning PHP developers

TL;DR
A php programmer who use xdebug’s remote debugging feature may affects RCE when he just access to attacker’s website in modern browsers.

Xdebug is an extension for PHP to assist with debugging and development. PHP programmers or web security researchers always setup a local PHP debugging environments for convenience. If the debugging server can be directly accessed by an attacker, there is a Remote Code Execution vulnerability.

But usually, these servers are in Intranet and some even bind on 127.0.0.1, which makes it hard to be accessed. What if attacking Xdebug using CSRF?

Let’s read the Xdebug’s document first. As in the doc, if xdebug.remote_connect_back is enabled, the xdebug.remote_host setting is ignored and Xdebug will try to connect to the client that made the HTTP request. It checks the $_SERVER['HTTP_X_FORWARDED_FOR'] and $_SERVER['REMOTE_ADDR'] variables to find out which IP address to use.
Continue reading “Pwning PHP developers”

Return Flow Guard

[DannyWei, lywang, FlowerCode] of Tencent Xuanwu Lab

Here is a preliminary documentation of the RFG implementation. We will update it once we have new findings and corrections.

We analyzed the Return Flow Guard introduced in Windows 10 Redstone 2 14942, released on October 7, 2016.

1 PROTECTION METHODS

Microsoft introduced Control Flow Guard in Windows 8.1 to protect against malicious modification of indirect call function pointers. CFG checks the target function pointer before each indirect call. However, CFG cannot detect modification of the return address on stack, or Return Oriented Programming.
The newly added RFG effectively stops these kind of attacks by saving the return address to fs:[rsp] at the entry of each function, and compare it with the return address on stack before returning.
Enabling RFG require both compiler and operating system support. During compilation, the compiler instruments the file by reserving a certain number of instruction spaces in the form of nop instructions.
When the target executable runs on a supported operating system, the reserved spaces are dynamically replaced with RFG instructions to check function return addresses. Otherwise, these nop instructions will not interfere with normal execution flow of the program.
The difference between RFG and GS (Buffer Security Check) is that the stack cookie can be obtained by using information leak or brute forcing, the RFG return address is written to the Thread Control Stack out of reach of attackers. This significantly increased the difficulty of the attack.
Continue reading “Return Flow Guard”

BadTunnel – A New Hope


This article purposes a new attack model to hijack TCP/IP broadcast protocol across different network segment, named “BadTunnel”.

With this method, NetBIOS Name Service Spoofing can be achieved, regardless of the attacker and the victim is on the same or different network, the firewalls and NAT devices in between. All it need is the victim navigate to a malicious web page with IE or Edge, or open a specially crafted document, and the attacker can hijack the victim’s NetBIOS name query to spoof as print server or file server in the local network.

By hijacking the WAPD name, the attacker can hijack all network communications, including but not limited to usual web accesses, Windows Update service and Microsoft Crypto API Certificate revocation list updates. Once the hijack is successful, it is easy to achieve arbitrary execution of program on the target system by using Evilgrade [1].

This method is effective on all Windows versions before the June 2016 patch, and can be exploited through all Internet Explorer, Microsoft Edge, and Microsoft Office versions, and can also be exploited through third-party applications. In fact, BadTunnel attack can be conducted on anywhere that a file URI scheme or UNC path can be embedded. For example, if a shortcut’s icon path is pointed to the malicious file URI scheme or UNC path, the BadTunnel attack can be triggered at the moment the user sees it in the Windows Explorer, which means BadTunnel can also be exploited through web pages, emails, USB flash drives and many other ways. It can even impact Web servers and SQL servers [2].

(This article does not include all contents covered by the BadTunnel research, the remaining part will be released in my presentation “BadTunnel: How do I get Big Brother power” on BlackHat US 2016.)
Continue reading “BadTunnel – A New Hope”

Exceptions in Exceptions – Abusing Special Cases in System Exception Handling to Achieve Unbelievable Vulnerability Exploitation


Memory Read / Write / Execute attributes are one of the most important part of system security. Usually it is mandatory to have writable attribute set before overwriting a block of memory, and executable attribute set before executing code in a block of memory, otherwise an exception is generated. However, there are some special cases in the Windows exception handling procedure that we can take advantage of. By abusing such exceptions, we could write to the unwritable, and execute the unexecutable.
Continue reading “Exceptions in Exceptions – Abusing Special Cases in System Exception Handling to Achieve Unbelievable Vulnerability Exploitation”

Use Chakra engine again to bypass CFG


This post is initially inspired by a talk with @TK, during which I learned the process and detail on how to successfully bypass CFG (reference: use Chakra JIT to bypass DEP and CFG). Due to my interest in its technology, I spent some time reading related materials and found another position to bypass CFG. I would like to thanks @TK for enlightening me on the ideas and techniques mentioned in this post.

There are plenty of articles that focus on the analysis of CFG, if you are interested, you may refer to my previous speech on HitCon 2015(《spartan 0day & exploit》). To be clear, this post is the part that is not revealed in my speech. At this point, the method to implement arbitrary code execution on edge through a write to memory is completely revealed.

Continue reading “Use Chakra engine again to bypass CFG”

Drag & Drop Security Policy of IE Sandbox


There is a kind of vulnerability that uses the flaw of whitelist applications in ElevationPolicy settings to accomplish sandbox bypass. A DragDrop policy setting similar to ElevationPolicy in the IE registry attracts our attention. In this post, the writer will try every possible means to break IE sandbox from the perspective of an attacker by analyzing all obstacles ahead to detail the drag drop security policy of IE sandbox.

Continue reading “Drag & Drop Security Policy of IE Sandbox”

Bypass DEP and CFG using JIT compiler in Chakra engine


JIT Spray is a popular exploitation technique first appeared in 2010. It embeds shellcode as immediate value into the executable code the JIT compiler generates. Currently, all major JIT engine, including Chakra, already have many mitigations in place against this technique, such as random NOP instruction insertion, constant blinding, etc.

This article points out two weaknesses in Chakra’s JIT Spray mitigation (in Windows 8.1 and older operating systems, and Windows 10, respectively), allowing attackers to use JIT Spray to execute shellcode, bypassing DEP. I will also discuss a method to bypass CFG using Chakra’s JIT compiler.

Continue reading “Bypass DEP and CFG using JIT compiler in Chakra engine”