Metamask – How to Connect Account to Smart Contract

metamasksolidityweb3js

I am learning Solidity. I have managed to create sample dapps with Truffle.

This sample apps are interacting with a smartcontract with web3js.

Each time my dapp calls a smartcontract's function, the metamask popup ask me a confirmation.
Everything works fine.

I have tried uniswap and there is something very strange for me: Uniswap ask me to "connect" my metamask wallet.

Then, i can see my Ethereum wallet's balance directly in uniswap webapp…

How can they do that ? I have looked uniswap soldity files on github and i do not understand where they connect the smartcontract to my metamask account.

Is it a good thing in term of privacy ? When i accept to connect my metamask wallet to uniswap, do i allow them to do what they want with my ether ?

Thanks

Best Answer

Connecting your MetaMask extension to Uniswap, does no provide access to Uniswap to manage your assets ( ETH or any other ERC20 token ). This is the so called Privacy mode of MetaMask which allow a user wallet address to be public only for connected websites. By doing it you're just letting know your MetaMask extension that you wanna use it on this particular website ( Uniswap ) and MetaMask is sharing your wallet address with the website. Everytime you're about to do blockchain action on Uniswap ( exchanging cryptocurrency for another, add or remove liquidity, etc ) then Uniswap is sending request to your MetaMask extension which is showing you the confirmation popup. Only after approving the confirmation request MetaMask is using your account private key to sign and submit transaction.

Related Solutions

[Ethereum] Unable to connect to metamask using web3

The problem here is likely that you are trying to run your page locally, which is explicitly restricted in MetaMask:

🌐 Http(s) - Web Server Required

Due to browser security restrictions, we can't communicate with dapps running on file://. Please use a local server for development.

You will need to publish your code to a local server to test MetaMask functionality.

In the situation where you do not need the MetaMask user context, you can use the HttpProvider fallback using infura.io:

https://github.com/shawntabrizi/ETH-Balance/blob/master/index.html#L13

window.web3 = new Web3(new Web3.providers.HttpProvider("https://mainnet.infura.io/<APIKEY>"));

This should allow you to do basic read operations on the Ethereum blockchain without needing to deploy to a local test server.

Token Approvals – Understanding the Risks in Transactions and Security

Yes, setting approval for your tokens lets whoever you approved spend them as if they were there own. So if you allow 1ETH to uniswap then uniswap could spend that 1ETH on your behalf without requiring you to sign any tx or anything of the sort. As for your question about uniswap getting hacked in theory yes, if the hacker obtained access to the address that you approved your tokens to then they could do what uniswap could, which as stated previously is spend your approved amount without any intervention needed from you.

Yes, only the address you approve from would be compromised and only the address you approved could spend the tokens on your behalf.

As soon as you approve your tokens the person you approved no longer needs any form of validation from you, they can spend whatever amount they are approved for. Regardless of the wallet you are using.

Yes you can change the amount you are approving, when you click approve, in metamask you will see "view full transaction details", when you click this it will say how much the user is proposing you allow and allow you to set a custom amount for allowance

p.s you can check who and what you have allowed here https://etherscan.io/tokenapprovalchecker

Best Answer

Related Solutions

[Ethereum] Unable to connect to metamask using web3

Token Approvals – Understanding the Risks in Transactions and Security

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