Practical Dictionary Attack On IPsec IKE

We found out that in contrast to public knowledge, the Pre-Shared Key (PSK) authentication method in main mode of IKEv1 is susceptible to offline dictionary attacks. This requires only a single active Man-in-the-Middle attack. Thus, if low entropy passwords are used as PSKs, this can easily be broken.

This week at the USENIX Security conference, Dennis Felsch will present our research paper on IPsec attacks: The Dangers of Key Reuse: Practical Attacks on IPsec IKE. [alternative link to the paper]

In his blog post, Dennis showed how to attack the public key encryption based authentication methods of IKEv1 (PKE & RPKE) and how to use this attack against IKEv2 signature based authentication method. In this blog post, I will focus on another interesting finding regarding IKEv1 and the Pre-Shared Key authentication.

IPsec and Internet Key Exchange (IKE)

IPsec enables cryptographic protection of IP packets. It is commonly used to build VPNs (Virtual Private Networks). For key establishment, the IKE protocol is used. IKE exists in two versions, each with different modes, different phases, several authentication methods, and configuration options. Therefore, IKE is one of the most complex cryptographic protocols in use.

In version 1 of IKE (IKEv1), four authentication methods are available for Phase 1, in which initial authenticated keying material is established: Two public key encryption based methods, one signature based method, and a PSK (Pre-Shared Key) based method.

The relationship between IKEv1 Phase 1, Phase 2, and IPsec ESP. Multiple simultaneous Phase 2 connections can be established from a single Phase 1 connection. Grey parts are encrypted, either with IKE derived keys (light grey) or with IPsec keys (dark grey). The numbers at the curly brackets denote the number of messages to be exchanged in the protocol.

Pre-Shared Key authentication

As shown above, Pre-Shared Key authentication is one of three authentication methods in IKEv1. The authentication is based on the knowledge of a shared secret string. In reality, this is probably some sort of password.

The IKEv1 handshake for PSK authentication looks like the following (simplified version):

In the first two messages, the session identifier (inside HDR) and the cryptographic algorithms (proposals) are selected by initiator and responder. 

In messages 3 and 4, they exchange ephemeral Diffie-Hellman shares and nonces. After that, they compute a key k by using their shared secret (PSK) in a PRF function (e.g. HMAC-SHA1) and the previously exchanged nonces. This key is used to derive additional keys (k_a, k_d, k_e). The key k_d is used to compute MAC_I over the session identifier and the shared diffie-hellman secret g^xy. Finally, the key k_e is used to encrypt ID_I (e.g. IPv4 address of the peer) and MAC_I. 

Weaknesses of PSK authentication

It is well known that the aggressive mode of authentication in combination with PSK is insecure and vulnerable against off-line dictionary attacks, by simply eavesedropping the packets. For example, in strongSwan it is necessary to set the following configuration flag in order to use it:

charon.i_dont_care_about_security_and_use_aggressive_mode_psk=yes

For the main mode, we found a similar attack when doing some minor additional work. For that, the attacker needs to waits until a peer A (initiator) tries to connect to another peer B (responder). Then, the attacker acts as a man-in-the middle and behaves like the peer B would, but does not forward the packets to B.

From the picture above it should be clear that an attacker who acts as B can compute (g^xy) and receives the necessary public values session ID, n_I, n_R. However, the attacker does not know the PSK. In order to mount a dictionary attack against this value, he uses the nonces, and computes a candidate for k for every entry in the dictionary. It is necessary to make a key derivation for every k with the values of the session identifiers and shared Diffie-Hellmann secret the possible keys k_a, k_d and k_e. Then, the attacker uses k_e in order to decrypt the encrypted part of message 5. Due to ID_I often being an IP address plus some additional data of the initiator, the attacker can easily determine if the correct PSK has been found.

Who is affected?

This weakness exists in the IKEv1 standard (RFC 2409). Every software or hardware that is compliant to this standard is affected. Therefore, we encourage all vendors, companies, and developers to at least ensure that high-entropy Pre-Shared Keys are used in IKEv1 configurations.

In order to verify the attack, we tested the attack against strongSWAN 5.5.1.

Proof-of-Concept

We have implemented a PoC that runs a dictionary attack against a network capture (pcapng) of a IKEv1 main mode session. As input, it also requires the Diffie-Hellmann secret as described above. You can find the source code at github. We only tested the attack against strongSWAN 5.5.1. If you want to use the PoC against another implementation or session, you have to adjust the idHex value in main.py.

Responsible Disclosure

We reported our findings to the international CERT at July 6th, 2018. We were informed that they contacted over 250 parties about the weakness. The CVE ID for it is CVE-2018-5389 [cert entry].

Credits

On August 10th, 2018, we learned that this attack against IKEv1 main mode with PSKs was previously described by David McGrew in his blog post Great Cipher, But Where Did You Get That Key?. We would like to point out that neither we nor the USENIX reviewers nor the CERT were obviously aware of this.
On August 14th 2018, Graham Bartlett (Cisco) email us that he presented the weakness of PSK in IKEv2 in several public presentations and in his book.
On August 15th 2018, we were informed by Tamir Zegman that John Pliam described the attack on his web page in 1999.

FAQs

• Do you have a name, logo, any merchandising for the attack?
  No.
• Have I been attacked?
  We mentioned above that such an attack would require an active man-in-the-middle attack. In the logs this could look like a failed connection attempt or a session timed out. But this is a rather weak indication and no evidence for an attack. 
• What should I do?
  If you do not have the option to switch to authentication with digital signatures, choose a Pre-Shared Key that resists dictionary attacks. If you want to achieve e.g. 128 bits of security, configure a PSK with at least 19 random ASCII characters. And do not use something that can be found in public databases.
• Am I safe if I use PSKs with IKEv2?
  No, interestingly the standard also mentions that IKEv2 does not prevent against off-line dictionary attacks.
• Where can I learn more?
  You can read the paper. [alternative link to the paper]
• What else does the paper contain?
  The paper contains a lot more details than this blogpost. It explains all authentication methods of IKEv1 and it gives message flow diagrams of the protocol. There, we describe a variant of the attack that uses the Bleichenbacher oracles to forge signatures to target IKEv2. 

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Vulcan DoS Vs Akamai

In the past I had to do several DoS security audits, with múltiples types of tests and intensities. Sometimes several DDoS protections were present like Akamai for static content, and Arbor for absorb part of the bandwith.

One consideration for the DoS/DDoS tools is that probably it will loss the control of the attacker host, and the tool at least has to be able to stop automatically with a timeout, but can also implement remote response checks.

In order to size the minimum mbps needed to flood a service or to retard the response in a significant amount of time, the attacker hosts need a bandwith limiter, that increments in a logarithmic way up to a limit agreed with the customer/isp/cpd.

There are DoS tools that doesn't have this timeouts, and bandwith limit based on mbps, for that reason I have to implement a LD_PRELOAD based solution: bwcontrol

Although there are several good tools for stressing web servers and web aplications like apache ab, or other common tools used for pen-testing, but I also wrote a fast web flooder in c++ named wflood.

As expected the most effective for taking down the web server are the slow-loris, slow-read and derivatives, few host were needed to DoS an online banking. 

Remote attacks to database and highly dynamic web content were discarded, that could be impacted for sure.

I did another tool in c++ for crafting massive tcp/udp/ip malformed packets, that impacted sometimes on load balancers and firewalls, it was vulcan, it freezed even the firewall client software.

The funny thing was that the common attacks against Akamai hosts, where ineffective, and so does the slow-loris family of attacks, because are common, and the Akamai nginx webservers are well tunned. But when tried vulcan, few intensity was enough to crash Akamai hosts.

Another attack vector for static sites was trying to locate the IP of the customer instead of Akamai, if the customer doesn't use the Akamai Shadow service, it's possible to perform a HTTP Host header scan, and direct the attack to that host bypassing Akamai.

And what about Arbor protection? is good for reducing the flood but there are other kind of attacks, and this protection use to be disabled by default and in local holidays can be a mess.

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WHO IS ETHICAL HACKER

Who is hacker?
A hacker is a Creative person and a creative Programmer,who have knowledge about Networking,Operating system,hacking & a best creative social engineer who control anyone's mind he is also a knowledgeable person.

Hacker are the problem solver and tool builder.

                                OR

A hacker is an individual who uses computer, networking and other skills to overcome a technical problem but it often refers to a person who uses his or her abilities to gain unauthorized access to system or networks in  order to commit crimes. 

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Blockchain Exploitation Labs - Part 2 Hacking Blockchain Authorization

Bypassing Blockchain Authorization via Unsecured Functions

Note: Since the first part of this series I have also uploaded some further videos on remediation of reentrancy and dealing with compiler versions when working with this hacking blockchain series.  Head to the console cowboys YouTube account to check those out.  Haha as mentioned before I always forget to post blogs when I get excited making videos and just move on to my next project… So make sure to subscribe to the YouTube if you are waiting for any continuation of a video series.. It may show up there way before here. 

Note 2:  You WILL run into issues when dealing with Ethereum hacking, and you will have to google them as versions and functionality changes often... Be cognizant of versions used hopefully you will not run into to many hard to fix issues. 

In the second part of this lab series we are going to take a look at privacy issues on the blockchain which can result in a vulnerably a traditional system may  not face. Since typically blockchain projects are open source and also sometimes viewable within blockchain explorers but traditional application business logic is not usually available to us. With traditional applications we might not find these issues due to lack of knowledge of internal functionality or inability to read private values on a remote server side script.  After we review some issues we are going to exploit an authorization issues by writing web3.js code to directly bypass vertical authorization restrictions.

Blockchain projects are usually open source projects which allow you to browse their code and see what's going on under the hood.  This is fantastic for a lot of reasons but a developer can run into trouble with this if bad business logic decisions are deployed to the immutable blockchain.  In the first part of this series I mentioned that all uploaded code on the blockchain is immutable. Meaning that if you find a vulnerability it cannot be patched. So let's think about things that can go wrong..

A few things that can go wrong:

• Randomization functions that use values we can predict if we know the algorithm
• Hard-coded values such as passwords and private variables you can't change.
• Publicly called functions which offer hidden functionality
• Race conditions based on how requirements are calculated

Since this will be rather technical, require some setup and a lot of moving parts we will follow this blog via the video series below posting videos for relevant sections with a brief description of each.  I posted these a little bit ago but have not gotten a chance to post the blog associated with it.  Also note this series is turning into a full lab based blockchain exploitation course so keep a lookout for that.

In this first video you will see how data about your project is readily available on the blockchain in multiple formats for example:

• ABI data that allows you to interact with methods.
• Actual application code.
• Byte code and assembly code.
• Contract addresses and other data.

 Lab Video Part 1: Blockchain OSINT: 

Once you have the data you need to interact with a contract on the blockchain via some OSINT how do you actually interface with it? That's the question we are going to answer in this second video. We will take the ABI contract array and use it to interact with methods on the blockchain via Web3.js and then show how this correlates to its usage in an HTML file

Lab Video Part 2: Connecting to a Smart Contract: 

Time to Exploit an Application:

Exploit lab time, I created an vulnerable application you can use to follow along in the next video. Lab files can be downloaded from the same location as the last blog located below. Grab the AuthorizationLab.zip file:

Lab file downloads:

https://github.com/cclabsInc/BlockChainExploitation

Ok so you can see what's running on the blockchain, you can connect to it, now what?   Now we need to find a vulnerability and show how to exploit it. Since we are talking about privacy in this blog and using it to bypass issues. Lets take a look at a simple authorization bypass we can exploit by viewing an authorization coding error and taking advantage of it to bypass restrictions set in the Smart Contract.  You will also learn how to setup a local blockchain for testing purposes and you can download a hackable application to follow along with the exercises in the video..

Lab Video Part 3:  Finding and hacking a Smart Contract Authorization Issue: 

Summary:

In this part of the series you learned a lot, you learned how to transfer your OSINT skills to the blockchain. Leverage the information found to connect to that Smart Contract. You also learned how to interact with methods and search for issues that you can exploit. Finally you used your browsers developer console as a means to attack the blockchain application for privilege escalation.

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TERMINOLOGIES OF ETHICAL HACKING

What is the terminologies in ethical hacking?

Here are a few key terms that you will hear in discussion about hackers and what they do:

1-Backdoor-A secret pathway a hacker uses to gain entry to a computer system.

2-Adware-It is the softw-are designed to force pre-chosen ads to display on your system.

3-Attack-That action performs by a attacker on a system to gain unauthorized access.

4-Buffer Overflow-It is the process of attack where the hacker delivers malicious commands to a system by overrunning an application buffer.

5-Denial-of-Service attack (DOS)-A attack designed to cripple the victim's system by preventing it from handling its normal traffic,usally by flooding it with false traffic.

6-Email Warm-A virus-laden script or mini-program sent to an unsuspecting victim through a normal-looking email message.

7-Bruteforce Attack-It is an automated and simplest kind of method to gain access to a system or website. It tries different combination of usernames and passwords,again & again until it gets in from bruteforce dictionary.

8-Root Access-The highest level of access to a computer system,which can give them complete control over the system.

9-Root Kit-A set of tools used by an intruder to expand and disguise his control of the system.It is the stealthy type of software used for gain access to a computer system.

10-Session Hijacking- When a hacker is able to insert malicious data packets right into an actual data transmission over the internet connection.

11-Phreaker-Phreakers are considered the original computer hackers who break into the telephone network illegally, typically to make free longdistance phone calls or to tap lines.

12-Trojan Horse-It is a malicious program that tricks the computer user into opening it.There designed with an intention to destroy files,alter information,steal password or other information.

13-Virus-It is piece of code or malicious program which is capable of copying itself has a detrimental effect such as corrupting the system od destroying data. Antivirus is used to protect the system from viruses.

14-Worms-It is a self reflicating virus that does not alter  files but resides in the active memory and duplicate itself.

15-Vulnerability-It is a weakness which allows a hacker to compromise the security of a computer or network system to gain unauthorized access.

16-Threat-A threat is a possible danger that can exploit an existing bug or vulnerability to comprise the security of a computer or network system. Threat is of two types-physical & non physical.

17-Cross-site Scripting-(XSS) It is a type of computer security vulnerability found in web application.It enables attacker to inject client side script into web pages viwed by other users.

18-Botnet-It is also known as Zombie Army is a group of computers controlled without their owner's knowledge.It is used to send spam or make denial of service attacks.

19-Bot- A bot is a program that automates an action so that it can be done repeatedly at a much higher rate for a period than a human operator could do it.Example-Sending HTTP, FTP oe Telnet at a higer rate or calling script to creat objects at a higher rate.

20-Firewall-It is a designed to keep unwanted intruder outside a computer system or network for safe communication b/w system and users on the inside of the firewall.

21-Spam-A spam is unsolicited email or junk email sent to a large numbers of receipients without their consent.

22-Zombie Drone-It is defined as a hi-jacked computer that is being used anonymously as a soldier or drone for malicious activity.ExDistributing Unwanted Spam Emails.

23-Logic Bomb-It is a type of virus upload in to a system that triggers a malicious action when certain conditions are met.The most common version is Time Bomb.

24-Shrink Wrap code-The process of attack for exploiting the holes in unpatched or poorly configured software.

25-Malware-It is an umbrella term used to refer a variety of intrusive software, including computer viruses,worms,Trojan Horses,Ransomeware,spyware,adware, scareware and other malicious program.

Follow me on instagram-anoymous_adi

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Security Onion - Linux Distro For IDS, NSM, And Log Management

Security Onion is a free and open source Linux distribution for intrusion detection, enterprise security monitoring, and log management. It includes Elasticsearch, Logstash, Kibana, Snort, Suricata, Bro, OSSEC, Sguil, Squert, NetworkMiner, and many other security tools. The easy-to-use Setup wizard allows you to build an army of distributed sensors for your enterprise in minutes!

Security-onion project

This repo contains the ISO image, Wiki, and Roadmap for Security Onion.

Looking for documentation?

Please proceed to the Wiki.

Screenshots

Download Security-Onion

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How To Install And Config Modlishka Tool - Most Advance Reverse Proxy Phishing

Continue reading

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Hacktronian: All In One Hacking Tools Installer For Linux And Android

Hacktronian Installation
   Termux users must install Python and Git first: pkg install git python
   Then enter these commands:   You can watch the full installation tutorial here:

Hacktronian Menu:

• Information Gathering
• Password Attacks
• Wireless Testing
• Exploitation Tools
• Sniffing & Spoofing
• Web Hacking
• Private Web Hacking
• Post Exploitation
• Install The HACKTRONIAN

Information Gathering menu:

• Nmap
• SEToolkit
• Port Scanning
• Host To IP
• wordpress user
• CMS scanner
• XSStrike Dork - Google Dorks Passive Vulnerability Auditor
• Scan A server's Users Crips

Password Attacks menu:

• Cupp
• Ncrack

Wireless Testing menu:

• Reaver
• PixieWPS
• Fluxion

Exploitation Tools menu:

• ATSCAN
• SQLMap
• Shellnoob
• commix
• FTP Auto Bypass
• jboss-autopwn

Sniffing and Spoofing menu:

• SEToolkit
• SSLtrip
• pyPISHER
• SMTP Mailer

Web Hacking menu:

• Drupal Hacking
• Inurlbr
• Wordpress & Joomla Scanner
• Gravity Form Scanner
• File Upload Checker
• Wordpress Exploit Scanner
• Wordpress Plugins Scanner
• Shell and Directory Finder
• Joomla! 1.5 - 3.4.5 remote code execution
• Vbulletin 5.X remote code execution
• BruteX - Automatically brute force all services running on a target
• Arachni - Web Application Security Scanner Framework

Private Web Hacking:

• Get all websites
• Get joomla websites
• Get wordpress websites
• Control Panel Finder
• Zip Files Finder
• Upload File Finder
• Get server users
• SQli Scanner
• Ports Scan (range of ports)
• ports Scan (common ports)
• Get server Info
• Bypass Cloudflare

Post Exploitation:

• Shell Checker
• POET
• Weeman

Hacktronian's License: MIT Licence

That's It... If You Like This Repo. Please Share This With Your Friends. And Don't Forget To Follow The Author At Twitter, Instagram, Github & SUBSCRIBE His YouTube Channel!!!

Thank you. Keep Visiting.. Enjoy.!!! :)

Download Hacktronian

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Reversing C++ String And QString

After the rust string overview of its internal substructures, let's see if c++ QString storage is more light, but first we'r going to take a look to the c++ standard string object:

At first sight we can see the allocation and deallocation created by the clang++ compiler, and the DAT_00400d34 is the string.

If we use same algorithm than the rust code but in c++:

We have a different decompilation layout. Note that the Ghidra scans very fast the c++ binaries, and with rust binaries gets crazy for a while.
Locating main is also very simple in a c++ compiled binary, indeed is more  low-level than rust.

The byte array is initialized with a simply move instruction:
        00400c4b 48 b8 68        MOV        RAX,0x6f77206f6c6c6568

And basic_string generates the string, in the case of rust this was carazy endless set of calls, detected by ghidra as a runtime, but nevertheless the basic_string is an external imported function not included on the binary.

(gdb) x/x 0x7fffffffe1d0
0x7fffffffe1d0: 0xffffe1e0            low str ptr
0x7fffffffe1d4: 0x00007fff           hight str ptr
0x7fffffffe1d8: 0x0000000b        sz
0x7fffffffe1dc: 0x00000000
0x7fffffffe1e0: 0x6c6c6568         "hello world"
0x7fffffffe1e4: 0x6f77206f
0x7fffffffe1e8: 0x00646c72
0x7fffffffe1ec: 0x00000000        null terminated
(gdb) x/s 0x7fffffffe1e0
0x7fffffffe1e0: "hello world"

The string is on the stack, and it's very curious to see what happens if there are two followed strings like these:

  auto s = string(cstr);

  string s2 = "test";

Clang puts toguether both stack strings:
[ptr1][sz1][string1][null][string2][null][ptr2][sz2]

C++ QString datatype

Let's see the great and featured QString object defined on qstring.cpp and qstring.h

Some QString methods use the QCharRef class whose definition is below:

class Q_EXPORT QCharRef {
    friend class QString;
    QString& s;
    uint p;

Searching for the properties on the QString class I've realized that one improvement that rust and golang does is the separation from properties and methods, so in the large QString class the methods are  hidden among the hundreds of methods, but basically the storage is a QStringData *;

After removing the methods of QStringData class definition we have this:

struct Q_EXPORT QStringData : public QShared {
    QChar *unicode;
    char *ascii;
#ifdef Q_OS_MAC9
    uint len;
#else
    uint len : 30;

Leo's Noob

I would like to send a salve to my friend noob at Rivendel in Brazilian company hahaha

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Gridcoin - The Bad

In this post we will show why Gridcoin is insecure and probably will never achieve better security. Therefore, we are going to explain two critical implementation vulnerabilities and our experience with the core developer in the process of the responsible disclosure. 

In our last blog post we described the Gridcoin architecture and the design vulnerability we found and fixed (the good). Now we come to the process of responsibly disclosing our findings and try to fix the two implementation vulnerabilities (the bad).

Update (15.08.2017):
After the talk at WOOT'17 serveral other developers of Gridcoin quickly reached out to us and told us that there was a change in responsibility internally in the Gridcoin-Dev team. Thus, we are going to wait for their response and then change this blog post accordingly. So stay tuned :)

Update (16.08.2017):
We are currently in touch with the whole dev team of Gridcoin and it seems that they are going to fix the vulnerabilities with the next release.


TL;DR
The whole Gridcoin currency is seriously insecure against attacks and should not be trusted anymore; unless some developers are in place, which have a profound background in protocol and application security.

What is Gridcoin?

Gridcoin is an altcoin, which is in active development since 2013. It claims to provide a high sustainability, as it has very low energy requirements in comparison to Bitcoin. It rewards users for contributing computation power to scientific projects, published on the BOINC project platform. Although Gridcoin is not as widespread as Bitcoin, its draft is very appealing as it attempts to  eliminate Bitcoin's core problems. It possesses a market capitalization of $13,530,738 as of August the 4th 2017 and its users contributed approximately 5% of the total scientific BOINC work done before October 2016.

A detailed description of the Gridcoin architecture and technical terms used in this blog post are explained in our last blog post.

The Issues

Currently there are 2 implementation vulnerabilities in the source code, and we can mount the following attacks against Gridcoin:

1. We can steal the block creation reward from many Gridcoin minters
2. We can efficiently prevent many Gridcoin minters from claiming their block creation reward (DoS attack)

So why do we not just open up an issue online explaining the problems?

Because we already fixed a critical design issue in Gridcoin last year and tried to help them to fix the new issues. Unfortunately, they do not seem to have an interest in securing Gridcoin and thus leave us no other choice than fully disclosing the findings.

In order to explain the vulnerabilities we will take a look at the current Gridcoin source code (version 3.5.9.8).

WARNING: Due to the high number of source code lines in the source files, it can take a while until your browser shows the right line.

Stealing the BOINC block reward

The developer implemented our countermeasures in order to prevent our attack from the last blog post. Unfortunately, they did not look at their implementation from an attacker's perspective. Otherwise, they would have found out that they conduct not check, if the signature over the last block hash really is done over the last block hash. But we come to that in a minute. First lets take a look at the code flow:

In the figure the called-by-graph can be seen for the function VerifyCPIDSignature.

1. CheckBlock → DeserializeBoincBlock [Source]
• Here we deserialize the BOINC data structure from the first transaction
2. CheckBlock → IsCPIDValidv2 [Source]
• Then we call a function to verify the CPID used in the block. Due to the massive changes over the last years, there are 3 possible verify functions. We are interested in the last one (VerifyCPIDSignature), for the reason that it is the current verification function.
3. IsCPIDValidv2 → VerifyCPIDSignature [Source]
4. VerifyCPIDSignature → CheckMessageSignature [Source, Source]

In the last function the real signature verification is conducted [Source]. When we closely take a look at the function parameter, we see the message (std::string sMsg)  and the signature (std::string sSig) variables, which are checked. But where does this values come from?

If we go backwards in the function call graph we see that in VerifyCPIDSignature the sMsg is the string sConcatMessage, which is a concatenation of the sCPID and the sBlockHash.
We are interested where the sBlockHash value comes from, due to the fact that this one is the only changing value in the signature generation.
When we go backwards, we see that the value originate from the deserialization of the BOINC structure (MiningCPID& mc) and is the variable mc.lastblockhash [Source, Source]. But wait a second, is this value ever checked whether it contains the real last block hash?

No, it is not....

So they just look if the stored values there end up in a valid signature.

Thus, we just need to wait for one valid block from a researcher and copy the signature, the last block hash value, the CPID and adjust every other dynamic value, like the RAC. Consequently, we are able to claim the reward of other BOINC users. This simple bug allows us again to steal the reward of every Gridcoin researcher, like there was never a countermeasure.

Lock out Gridcoin researcher
The following vulnerability allows an attacker under specific circumstances to register a key pair for a CPID, even if the CPID was previously tied to another key pair. Thus, the attacker locks out a legit researcher and prevent him from claiming BOINC reward in his minted blocks.

Reminder: A beacon is valid for 5 months, afterwards a new beacon must be sent with the same public key and CPID.

Therefore, we need to take a look at the functions, which process the beacon information. Every time there is a block, which contains beacon information, it is processed the following way (click image for higher resolution):

In the figure the called-by-graph can be seen for the function GetBeaconPublicKey.

We now show the source code path:

• ProcessBlock → CheckBlock [Source]
• CheckBlock → LoadAdminMessages [Source]
• LoadAdminMessages → MemorizeMessages [Source]
• MemorizeMessages → GetBeaconPublicKey [Source]

In the last function GetBeaconPublicKey there are different paths to process a beacon depending on the public key, the CPID, and the time since both were associated to each other.
For the following explanation we assume that we have an existing association (bound) between a CPID A and a public key pubK_A for 4 months.

1. First public key for a CPID received [Source]
• The initial situation, when pubK_A was sent and bind to CPID  A (4 months ago)
2. Existing public key for a CPID was sent [Source]
• The case that pubK_A was resent for a CPID A, before the 5 months are passed by
3. Other public key for a CPID was sent [Source]
• The case, if a different public key pubK_B for the CPID A was sent via beacon.
4. The existing public key for the CPID is expired
• After 5 months a refresh for the association between A and pubK_A is required.

When an incoming beacon is processed, a look up is made, if there already exists a public key for the CPID used in the beacon. If yes, it is compared to the public key used in the beacon (case 2 and 3).
If no public key exists (case 1) the new public key is bound to the CPID.

If a public key exists, but it was not refreshed directly 12.960.000 seconds (5 months [Source]) after the last beacon advertisement of the public key and CPID, it is handled as no public key would exist [Source].

Thus, case 1 and 4 are treated identical, if the public key is expired, allowing an attacker to register his public key for an arbitrary CPID with expired public key. In practice this allows an attacker to lock out a Gridcoin user from the minting process of new blocks and further allows the attacker to claim reward for BOINC work he never did.

There is a countermeasure, which allows a user to delete his last beacon (identified by the CPID) . Therefore, the user sends 1 GRC to a special address (SAuJGrxn724SVmpYNxb8gsi3tDgnFhTES9) from an GRC address associated to this CPID [Source]. We did not look into this mechanism in more detail, because it only can be used to remove our attack beacon, but does not prevent the attack.

The responsible disclosure process

As part of our work as researchers we all have had the pleasure to responsible disclose the findings to developer or companies.

For the reasons that we wanted to give the developer some time to fix the design vulnerabilities, described in the last blog post, we did not issue a ticket at the Gridcoin Github project. Instead we contacted the developer at September the 14th 2016 via email and got a response one day later (2016/09/15). They proposed a variation of our countermeasure and dropped the signature in the advertising beacon, which would result in further security issues. We sent another email (2016/09/15) explained to them, why it is not wise to change our countermeasures and drop the signature in the advertising beacon.
Unfortunately, we did not receive a response. We tried it again on October the 31th 2016. They again did not respond, but we saw in the source code that they made some promising changes. Due to some other projects we did not look into the code until May 2017. At this point we found the two implementation vulnerabilities. We contacted the developer twice via email (5th and 16th of May 2017) again, but never received a response. Thus, we decided to wait for the WOOT notification to pass by and then fully disclose the findings. We thus have no other choice then to say that:

The whole Gridcoin cryptocurrency is seriously insecure against attacks and should not be trusted anymore; unless some developers are in place, which have a profound background in protocol and application security.

Further Reading

A more detailed description of the Gridcoin architecture, the old design issue and the fix will be presented at WOOT'17. Some days after the conference the paper will be available online.

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Here you will find privilege escalation tools for Windows and Linux/Unix* (in some near future also for Mac).
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Let's improve PEASS together
If you want to add something and have any cool idea related to this project, please let me know it in the telegram group https://t.me/peass or using github issues and we will update the master version.

Advisory
All the scripts/binaries of the PEAS suite should be used for authorized penetration testing and/or educational purposes only. Any misuse of this software will not be the responsibility of the author or of any other collaborator. Use it at your own networks and/or with the network owner's permission.

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This article is the property of Tenochtitlan Offensive Security. Verlo Completo --> https://tenochtitlan-sec.blogspot.com

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