bookmark_borderCC7F Round 1., during Hacktivity 2021

In a joint project we step to the next level with two rounds of CCTF. Harder challenges and highers prices wait for the players.

You can read more about us in the media:

https://finance.yahoo.com/news/cctf-organizers-awalcon-cryptall-partner-131600682.html

https://markets.businessinsider.com/news/stocks/cctf-organizers-awalcon-and-cryptall-partner-with-ecox-to-host-the-largest-blockchain-hacking-event-so-far-1030838702

bookmark_borderPublic Smart Contract Audit: Next Earth, part 1.

Overview

The Next Earth project requested a smart contract code security audit.

Start date of the audit: 2021.07.06.

Report date: 2021.07.07.

Project website: https://nextearth.io/

Platform: Solidity / Ethereum

Audited commit: 4bac0998cac7e19a3a5370c997551ba71bb82d57

Smart contracts in scope:

  • NFT.sol
  • Payment.sol
  • Presalse.sol
  • PriceFeed.sol

Imported smart contracts:

  • @chainlink/contracts/src/v0.6/interfaces/AggregatorV3Interface.sol
  • @openzeppelin/contracts/access/AccessControl.sol
  • @openzeppelin/contracts/access/Ownable.sol
  • @openzeppelin/contracts/security/Pausable.sol
  • @openzeppelin/contracts/token/ERC721/ERC721.sol
  • @openzeppelin/contracts/token/ERC721/extensions/ERC721Burnable.sol
  • @openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol
  • @openzeppelin/contracts/utils/cryptography/ECDSA.sol

Overall result: pass

Auditor: six ~ PGP 450F 4AC8 0BD8

Objective and methodology

The objective of the security assessment is to gain insight into the security of the smart contracts listed in the scope.

Code review main check items:

  • Line-by-line audit
  • Business logic
  • Data consistency
  • Coding style violations
  • Gas usage
  • Reentrancy

Automated tools:

Further documents incorporated in the methodology:

Audit results

Critical severity

No cricitcal severity issue have been found during the manual code review or by using automated tools.

High severity

No high severity issue have been found during the manual code review or by using automated tools.

Medium severity

No medium severity issue have been found during the manual code review or by using automated tools.

Low severity

Presale.sol | Creation of unintended packs in setPackPrice()

Description and impact

At line61 it is specified that we have packages from 1 to 5, but in the setPackPrice function at line120, it allows to pass zero or any positive number up to 2**32-1 for _type and 2**256-1 for price.

Logic says, that would be also an integer overflow, but from Solidity compiler version 0.8.0, overflowing transactions get reverted automatically.

This vulnerability allows the creation of packages against the intentional logic of the project.

This is only a low level vulnerability as onlyOwner is used and it can’t be exploited by others.

Line 61.:

require(packType >= 1 && packType <= 5, “invalid pack type”); // we have 5 pack types from 1 to 5

Line 120.:

function setPackPrice(uint32 _type, uint256 price) external onlyOwner {

packPrices[_type] = price;

}

Proposed solution

You could use a require statement checking the type (and preferably the price too) before setting the price for a pack.

Presale.sol | Unused code, todo, typo

Description

Payment.sol, line36.

// TODO can we do this pull over push?

Presale.sol, line 88.

// uint256 contractShare = msg.value – charityShare – comissionShare; // not used, need to remove it

NFT.sol, line 42.

// happens against a signle single user…

Presale.sol, multiple lines:

comissionCode” → “commissionCode”

Proposed solution

Update the mentioned points.

NFT.sol | Minting functions can go above gas limit

Description

The issue was acknowledged by the project before the audit.

Function safeMint from line 35. and function safeMintTo() from line 49. can go above the gas limit if tokenIds.length becomes too big.

Proposed solution

Implement limits, don’t let users break themselves.

Lack of README file

Description

The project does not have a README file or documentation.

Proposed solution

Provide a clear documentation and use more comments.

Lack of comments regarding functionality

Description

The smart contracts have comments at some critical points, but not about the functions or general code logic.

It is also recommended to add NatSpec to the code.

Proposed solution

Follow the Solidity Coding style guide.

https://docs.soliditylang.org/en/latest/style-guide.html

Contact

Awalcon – six

Website: https://awalcon.org/

E-mail:six@awalcon.org

Telegram/Signal: +36 20 256 4090

Git: https://git.hsbp.org/six

PGP: B1F7 B1D6 8838 98B4 2212 1D90 CA71 D1E4 078E 99C5

bookmark_borderCCTF 5 Writeups – Part 1.

RTFM (50 points)

As is the case with all CCTF editions, there’s a quasi-challenge that points people in the direction of the manual, and which is supposed to give an initial feel for how the search for a so-called flag goes. The accepted solution was one of the example flags shown in the manual.

Author: SI

unk (80 points)

A real, entry-level challenge. A file (named “unk”) was presented. It appears to be a damaged Microsoft Word document. A Word document is actually a Zip archive containing things like XML and thumbnail image files. Different Zip implementations work differently on damaged archives; e.g. GNU Zip was able extract the damaged Zip archive to a sufficient extent. The flag was in the thumbnail image. — Sometimes thumbnails are not in sync with the working text of the document, and may contain sensitive data: snapshots of rendered text that was deleted.

Author: SI

CryptoFriend (80 points)

Another entry-level challenge. A file was presented under the name “a_friend.zip”. This was also an invalid Zip archive.

tl;dr: the file turned out to be a concatenation of a Zip archive and a PNG image, where the latter contained the flag. But on to the goose chase leading to this discovery:

E.g. FreeBSD’s Zip implementation extracted a single “a friend.docx” file. This file was a valid Word document which read “i hid my location, come help me”. OK, let’s do this.

No, the thumbnail didn’t contain a flag. According to metadata in the document, the document was prepared by Kevin Chung on 2017-09-11. Let’s find this guy. Searching the internet for his contact information, cryptocurrency addresses, etc, but most importantly, flags, it came to light that he’s behind CTFd, the web application powering the CCTF contest’s portal — the plot thickened. He also runs a blog. One of his blog posts, dated closest to 2017-09-11, really contains a string of the form “FLAG{…}”. Tough luck: wrong answer. In fact, Kevin Chung appeared the same way in the “unk” challenge. So this was a witch hunt.

One other thing was eye-poking: potentially subliminal data in the Word document’s XML attributes, e.g. “paraId="3B2827CE"” — is there real content embedded in these IDs, or is this totally random crap?

The “a_friend.zip” file was actually ~19MiB in size, while the extracted “a friend.docx” was only ~24KiB, so it makes more sense that the flag was to be hidden outside the latter. Inspecting the file (using tools like: strings, hd, etc), one could stumble upon the following:
• There was EXIF data containing latitude–longitude coordinates. However, those pointed to Andromeda, so this lead had to be scrapped as well.
• There was an EXIF user comment with a code of some sort: “FM0 FC000000000:zzzzzz1 f144 078043881a29e1e816c14c0 bac 87152…”. Well, whatever.

Upon further inspection, it was then apparent that the EXIF structure was actually part of a PNG image that appeared without compression in the “a_friend.zip” file.

Author: SI

Vault (100 points)

Given some smart contract — the source code and a deployed instance, displayed by the etherscan.io service —, the task was to determine the correct call to the contract that would exfiltrate the 0.1337 ETH (of the Ropsten test network kind) from the contract.

In the constructor, the `pin` variable was initialized with the value of `block.timestamp % 10000`, and then never changed. And there was the fund retrieval function taking a single number argument, which would compare the number against the `pin` variable. The latter just signifies that we were looking for the value of `block.timestamp` at the time of construction.

There were multiple techniques to tackle this problem:

• A hacky approach was to try to call the contract with every possible value from 0 to 9999, and see which worked — after all, this was on Ropsten, a gas giant.
• There are many tools to interact with deployed contracts, including to read values of global variables. The `pin` variable was private, so if a particular tool didn’t permit reading the value directly, it was conceivable to trick the tool into thinking that the contract’s source code / ABI was slightly different: where the `pin` variable wasn’t private.
• The smart solution was to note the date and time when the contract was created (corresponding to when the block, that included the creating transaction, was mined), and convert it to seconds-since-the-Epoch.

Author: SI

bookmark_borderEvents in May 2021: Blockchain Budapest 4.0 and CCTF

BDAY is organized again in 2021 with great talks, presentations and the CryptoCurrency (is) The Flag hacker game.

This is another chance to meet the best in the largest cryptocurrency and blockchain gathering of Central Europe. Topics as follow:

  • NFTs and their real values
  • DeFi and its future
  • Largest Hungarian Blockchain projects such as CCTF or ILGON
  • …and the first Satoshi Statue 🙂
Website: https://blockchainbudapest.hu/

The presenters and those who own a VIP ticket will be able to take part in the networking. We hope to see you there!

bookmark_borderCrypto Guide for Beginners: Start playing CCTF

With our partners* and sponsors* we are organizing CCTF for the 7th. Just like at the previous events, we are providing a guide for beginners. This helps you to get started with hacking Ethereum smart contracts.

It is recommended to move step by step. Follow this guide and you will understand the basic logic of cryptocurrencies, blockchain and smart contracts.

CCTF Vol5. registration (finished): https://vol5.cryptoctf.org/

CCTF Vol6. registration (finished): https://vol6.cryptoctf.org/register

CCTF Vol7. registration: https://cc7f.cryptoctf.org/register

Guide intro

Cryptocurrencies such as Bitcoin and Ethereum allow you to handle digital assets on decentralized networks. There is no central authority which can censor or block your account.

Accounts are stored in digital wallets, eg. “ethereum wallet”. If you use “Metamask ethereum wallet”, you have full access your wallet, meaning only you have the private keys that are needed to make transactions. The public part to share from this wallet is only your ethereum address. In fact, when you send 1 Ethereum to another person, to his address (into her/his wallet) what happens is that you sign a transaction with your private key that this 1 Ethereum no longer belongs to you, but to the other address. That’s it. The transaction gets propagated on the Ethereum network and miners verify that transaction.

Here are the screenshots in 3 steps of sending 1 Ethereum to another address:

No central bank or complicated legal processes: you have the power to make transactions anywhere in the world fast and with a few clicks. Also, none can block it. Follow this guide further and we will create your first Ethereum wallet.

But why Ethereum? Because you can do more with transaction: engage with smart contracts. Imagine coding a program that you upload to a decentralized network, it gets stored there and can be called anytime in the future. Or imagine a business that does not have physical contracts, just virtual ones on the blockchain. All these are secure as long as somebody successfully cheats/hacks the network consensus or exploits vulnerabilities in the smart contrats itself. It may sound complicated for the first, but it is not rocket science. Let’s start creating your wallet.

Creating a wallet

Most of the Ethereum hacks (breaking smart contracts, accessing accounts without or with weak authentication, phishing) do not require more than a web browser and a bit of coding skills. For the start, only a FireFox or a Chromium/Chrome web broswer is enough with the MetaMask addon. You can connect this wallet to the Ethereum test networks and play around.

  1. Open your FireFox or Chromium browser and install the MetaMask extension: https://metamask.io/. Currenly, MetaMask is the most commonly used software by end users to interact with Ethereum contracts (these are called “dapps”/”decentralized apps” too).
  2. After installing the extension, it either automatically opens up or you can open it from the top right bar in your browser.
  3. The first step of using MetaMask is to generate your wallet. At this point you are asked to provide a password. Preferably, use a passphrase that is like a sentence, but does not include words from dictionaries (example: “HaxxA11co|ns”). Choose wisely.
  4. Move on and read the phishing warning carefully!
  5. Finally you need to make sure the secret backup words that allows restoring the wallet is secured: of course in a place only you can access and see. For playing you can just use paper, but for real wallets with high balances it is better to write the words on something that can survive even if your house burns down (eg. MyCryptoSeed)
  6. All is set. Now you have an Ethereum wallet and inside: an Ethereum account.

Changing networks and faucets

MetaMask allows you to change between Ethereum networks. Please change to Ropsten Test Network and remember that the game will be played from there.

Faucets provide free Ethereum for you on the test networks. Now it is time to get some from: https://faucet.ropsten.be/ (if it does not work, you can find other Ropsten faucets online or contact the CCTF organizers).

Congratulations, you are ready: time to get into code and hacking!

Coding and compiling a smart contract

Let’s compile an example smart contract and interact with it. Open https://remix.ethereum.org/ where you get an example contract written in Solidity language. Remix website has an inbuilt compiler and if you click on “Start to compile” it will compile the code. Now you can swith to the “Run” tab. If you have MetaMask running, then you should see “Injected web3” in the environment.

MetaMask injects the so called web3.js into each website you visit, that way the website can communicate with MetaMask (also think about that: is it a good idea to inject to all sites?).

Deploying a smart contract

Make sure your MetaMask account is unlocked, switched to “Ropsten” and you got a coin from the faucet. Then click on “Deploy”.

MetaMask pops you up a transaction which is actually the deployment of the compiled smart contract to the Ropsten Ethereum test network. Now you may wonder what “gas fee” is? Gas limits the computational efforts of the smart contract, meaning you cannot deploy a computational heavy infinite loop for free. You can only use a smart contract if enough gas is provided. If you are ready, click on “Confirm”.

Wait until the transaction changes from “Pending” state to “Confirmed”. This is indicated in MetaMask. The network needs time to make sure your conract is broadcasted and mined successfully. If you click on the transaction, you have a button “View transaction on Etherscan”: click on it and have a look at what happened.

Interacting with the contract functions

By going back to https://remix.ethereum.org/ you can start playing with the “Deployed Contracts”, under the “Run” tab. You can call the deployed smart contract’s functions one by one. Each call you initiate takes a transaction. The executed code runs on all of the Ropsten Ethereum nodes.

Congratulations, you have compiled your first smart contract and interacted with it.

Congratulations!

You have seen the very basics and it is time to think about what else can go wrong… Weak passwords, MetaMask seeds all over the place, programmers making mistakes in smart contracts that you can call, logic, broken crypto problems and so on.

References, to learn more

Bitcoin white paper

Cryptography tutorial

Ethereum white paper

Ethereum beige paper (a readable version of the yellow paper)

History of Ethereum Security Vulnerabilities, Hacks and Their Fixes (2017 Sept.)

*Partners of CCTF Vol. 5 and 6: Awalcon / CryptAll / H.A.C.K. / BsdiesBUD / BlockchainBudapest

*Sponsors of Vol. 5 and 6: HODLbag / CasperLabs / MyCryptoSeed / ILGON

*Partners of CCTF Vol. 7: Awalcon / CryptAll / ASIS / H.A.C.K. / EcoX / Hacktivity / Olymp

*Sponsors of Vol. 7: HODLbag / LanTo Capital / AsicMinerz / MyCryptoSeed

bookmark_borderUpcoming blockchain CTF games

Cryptocurrency is the hype and we are ready with our partners to publish the next CryptoCurrency is The Flag games. For the 5th and 6th time, paricitpants will have the chance to win real Ethereum and HODLbag tokens while learning about cryptocurrency, information security and hacking.

The upcoming events will be organized online and the participation is open for everyone local or remote. Like last year, a new guide for beginners will be provided, so don’t worry if you are just getting started! You are here to improve yourself!

If you want to have a look at past challenges, you can read the writeups written by previous CCTF participant:

BIPolognese

Don’t be eval

Pwncoin Challenge

Foxy

EVM bytes


CCTF Vol5 is focusing more on beginners, so don’t miss the chance. If you join the conference you will have extended rewards!

Live during BDAY 4.0 || 2021.May.18.

https://blockchainbudapest.hu/


Feel like a 1337 haxor? Prove yourself with the hardest crypto* challenges during BsidesBud and win the local prizes too!

CCTF Vol6 during BsidesBUD 2021 || April 27.

https://2021.bsidesbud.com/


Get ready and HODL yourself!

bookmark_borderBitcoin and Crypto* events in Dubai

Looking for meeting other people who are into crypto*? Wants to find the best place to start your blockchain business? Awalcon and the HODLbag project shares the best places to get started. If you are an enthusiast, already have a project, looking for investors or just a beginner who wants to learn and meet interesting people: this is what you need to know.

EcoX Networking Events

Every Tuesday, you have the chance to meet people from different backgrounds, many of them are into crypto*. Just get there and be brave to start discussions with people you do not know yet!

Find the flyers on Instagram: https://www.instagram.com/ecoxdubai/

Website: https://www.ecox.pro/

Crypto Mondays

Crypto* people in the space! Mostly for beginner, but you can meet some big names there. Last Monday, we had Tone Vayes and Gary Sheynkman with us.

For the next meetup, make sure to follow: https://twitter.com/CryptoMondaysSJ

You can also join the cryptoDubai group on Signal where we keep posting about the events. Contact: https://linktr.ee/awalcon

Dubai allows crypto businesses to set up in free zone

Just as the heading says, things are moving on in the free zone.

An economic free zone in Dubai has opened for businesses that are offering, issuing, listing and trading crypto assets. The Dubai Multi Commodities Center (DMCC) signed the initial agreement with the Securities and Commodities Authority (SCA) to allow licensing for firms that deal with crypto assets.

Find more details on this link:

https://www.arabnews.com/node/1828681/business-economy

bookmark_border4 Microsoft Exchange Server vulnerabilites

March is not a good month for Microsoft in 2021. At the beginning of March, Microsoft has given out warnings about critical unpatched Exchange Server vulnerabilities.

These vulnerabilities can infect tens of thousands of businesses, government entities in the U.S., in Asia, and in Europe. In addition, the number of targeted attacks have increased.

Outside of U.S, the malware also infected services in Norway, the Czech Republic, and the Netherlands. Attackers scan offensively Microsoft’s email servers, which represent high-value. This time the numbers of attacks were higher compared to last December’s SolarWinds hacking spree. The vulnerability allows breaking into Microsoft Exchange Servers and allows the installation of unauthorized web-based backdoors to facilitate long-term access.

Awalcon recommends updating or disconnecting the affected Exchange Servers immediately.

The vulnerability CVE-2021-26855 allows the bypass of authentication of an on-premises Microsoft Exchange Server that’s able to receive untrusted connections from an external source on port 443. The next vulnerabilities are CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065: these allow malicious parties to gain remote access to the vulnerable systems. It is an interesting fact that both CVE-2021-26855 and CVE-2021-27065 were reported in October 2020.

On March 12, 2021 Microsoft released an emergency patch for all the four security issues. As always, the bad news for the affected businesses: installing the patches is not enough if you have already been backdoored.

bookmark_borderGoogle Chrome zero-day vulnerability

Google has introduced an update to the Chrome browser and released a second patch within a month that fixes five vulnerabilities, including a zero-day vulnerability. One of the most important bugs can be traced as CVE-2021-21193 and affects the Windows, Linux, OS X versions of the browser.

This vulnerability was detected by an anonymous user, and through this bug an attacker can execute arbitrary code on the target system. The measuring of this error is  8.8 out of 10 on the CVSS scale. To avoid this security issue, update your Google Chrome browser at Settings -> Help -> About.

Why the browsers?
Browsers tend to evolve faster in many organizations than other applications, and browsers are a great way to reap the benefits, and attackers continue to target them because they continue to be excellent entry points for endpoint threats within the organization. In addition, the extensions are usually updated less frequently and require hardening to prevent further attacks.

What is a zero-day vulnerability?
Timing is most important here. The moment the flaw becomes known, hackers around the world can try to exploit it. Overall, programmers have zero days to find a solution to the issue, henceforth the term “zero-day vulnerability”.

This can take almost any form, such as missing data encryption, buffer overflows, missing permissions, SQL injection, broken algorithms, URL redirects, errors, or password security issues.

How protect yourself?
Here are some tips to help protect your business from these types of attacks:

Be informed: pay attention to software vendor spending, it may be time to take advantage of security measures or respond to threats before taking advantage of them

Take additional security measures: consider seeking the assistance of an experienced professional, as the safety measures mentioned above are not sufficient to fully protect you.

Keep your system up to date: make sure your software platforms are up to date. The best solution is to allow automatic updates so that the software is updated regularly without any manual intervention.