Welcome to Zeppelin-Solidity¶
Zeppelin is a library for writing secure Smart Contracts on Ethereum.
With Zeppelin, you can build distributed applications, protocols and organizations:
- using Common Contract Security Patterns
- in the Solidity language.
The code is open-source, and available on github.
Getting Started¶
Zeppelin integrates with Truffle, an Ethereum development environment. Please install Truffle and initialize your project with truffle init
:
npm install -g truffle
mkdir myproject && cd myproject
truffle init
To install the Zeppelin library, run:
npm i zeppelin-solidity
After that, you’ll get all the library’s contracts in the contracts/zeppelin folder. You can use the contracts in the library like so:
import "./zeppelin/Ownable.sol";
contract MyContract is Ownable {
...
}
NOTE: The current distribution channel is npm, which is not ideal. We’re looking into providing a better tool for code distribution , and ideas are welcome.
Truffle Beta Support¶
We also support Truffle Beta npm integration. If you’re using Truffle Beta, the contracts in node_modules
will be enough, so feel free to delete the copies at your contracts
folder. If you’re using Truffle Beta, you can use Zeppelin contracts like so:
import "zeppelin-solidity/contracts/Ownable.sol";
contract MyContract is Ownable {
...
}
For more info see the Truffle Beta package management tutorial.
Ownable¶
Base contract with an owner.
Ownable( )¶
Sets the address of the creator of the contract as the owner.
modifier onlyOwner( )¶
Prevents function from running if it is called by anyone other than the owner.
transfer(address newOwner) onlyOwner¶
Transfers ownership of the contract to the passed address.
Killable¶
Base contract that can be killed by owner.
Inherits from contract Ownable.
kill( ) onlyOwner¶
Destroys the contract and sends funds back to the owner.
Claimable¶
Extension for the Ownable contract, where the ownership needs to be claimed
transfer(address newOwner) onlyOwner¶
Sets the passed address as the pending owner.
modifier onlyPendingOwner¶
Function only runs if called by pending owner.
claimOwnership( ) onlyPendingOwner¶
Completes transfer of ownership by setting pending owner as the new owner.
Migrations¶
Base contract that allows for a new instance of itself to be created at a different address.
Inherits from contract Ownable.
upgrade(address new_address) onlyOwner¶
Creates a new instance of the contract at the passed address.
setCompleted(uint completed) onlyOwner**¶
Sets the last time that a migration was completed.
SafeMath¶
Provides functions of mathematical operations with safety checks.
assert(bool assertion) internal¶
Throws an error if the passed result is false. Used in this contract by checking mathematical expressions.
safeMul(uint a, uint b) internal returns (uint)¶
Multiplies two unisgned integers. Asserts that dividing the product by the non-zero multiplicand results in the multiplier.
safeSub(uint a, uint b) internal returns (uint)¶
Checks that b is not greater than a before subtracting.
safeAdd(uint a, uint b) internal returns (uint)¶
Checks that the result is greater than both a and b.
LimitBalance¶
Base contract that provides mechanism for limiting the amount of funds a contract can hold.
LimitBalance(unit _limit)¶
Constructor takes an unisgned integer and sets it as the limit of funds this contract can hold.
modifier limitedPayable()¶
Throws an error if this contract’s balance is already above the limit.
PullPayment¶
Base contract supporting async send for pull payments. Inherit from this contract and use asyncSend instead of send.
asyncSend(address dest, uint amount) internal¶
Adds sent amount to available balance that payee can pull from this contract, called by payer.
withdrawPayments( )¶
Sends designated balance to payee calling the contract. Throws error if designated balance is 0, if contract does not hold enough funds ot pay the payee, or if the send transaction is not successful.
StandardToken¶
Based on code by FirstBlood: Link FirstBloodToken.sol
Inherits from contract SafeMath. Implementation of abstract contract ERC20 (see https://github.com/ethereum/EIPs/issues/20)
approve(address _spender, uint _value) returns (bool success)¶
Sets the amount of the sender’s token balance that the passed address is approved to use.
allowance(address _owner, address _spender) constant returns (uint remaining)¶
Returns the approved amount of the owner’s balance that the spender can use.
balanceOf(address _owner) constant returns (uint balance)¶
Returns the token balance of the passed address.
transferFrom(address _from, address _to, uint _value) returns (bool success)¶
Transfers tokens from an account that the sender is approved to transfer from. Amount must not be greater than the approved amount or the account’s balance.
function transfer(address _to, uint _value) returns (bool success)¶
Transfers tokens from sender’s account. Amount must not be greater than sender’s balance.
BasicToken¶
Simpler version of StandardToken, with no allowances
balanceOf(address _owner) constant returns (uint balance)¶
Returns the token balance of the passed address.
function transfer(address _to, uint _value) returns (bool success)¶
Transfers tokens from sender’s account. Amount must not be greater than sender’s balance.
CrowdsaleToken¶
Simple ERC20 Token example, with crowdsale token creation.
Inherits from contract StandardToken.
createTokens(address recipient) payable¶
Creates tokens based on message value and credits to the recipient.
getPrice() constant returns (uint result)¶
Returns the amount of tokens per 1 ether.
Bounty¶
To create a bounty for your contract, inherit from the base Bounty contract and provide an implementation for `deployContract()`
returning the new contract address.:
import {Bounty, Target} from "./zeppelin/Bounty.sol";
import "./YourContract.sol";
contract YourBounty is Bounty {
function deployContract() internal returns(address) {
return new YourContract()
}
}
Next, implement invariant logic into your smart contract. Your main contract should inherit from the Target class and implement the checkInvariant method. This is a function that should check everything your contract assumes to be true all the time. If this function returns false, it means your contract was broken in some way and is in an inconsistent state. This is what security researchers will try to acomplish when trying to get the bounty.
At contracts/YourContract.sol:
import {Bounty, Target} from "./zeppelin/Bounty.sol";
contract YourContract is Target {
function checkInvariant() returns(bool) {
// Implement your logic to make sure that none of the invariants are broken.
}
}
Next, deploy your bounty contract along with your main contract to the network.
At `migrations/2_deploy_contracts.js`
:
module.exports = function(deployer) {
deployer.deploy(YourContract);
deployer.deploy(YourBounty);
};
Next, add a reward to the bounty contract
After deploying the contract, send reward funds into the bounty contract.
From `truffle console`
:
bounty = YourBounty.deployed();
address = 0xb9f68f96cde3b895cc9f6b14b856081b41cb96f1; // your account address
reward = 5; // reward to pay to a researcher who breaks your contract
web3.eth.sendTransaction({
from: address,
to: bounty.address,
value: web3.toWei(reward, "ether")
})
If researchers break the contract, they can claim their reward.
For each researcher who wants to hack the contract and claims the reward, refer to our Test for the detail.
Finally, if you manage to protect your contract from security researchers, you can reclaim the bounty funds. To end the bounty, kill the contract so that all the rewards go back to the owner.:
bounty.kill();
Common Contract Security Patterns¶
Zeppelin smart contracts are developed using industry standard contract security patterns and best practices. To learn more, please see Onward with Ethereum Smart Contract Security.
Developer Resources¶
Building a distributed application, protocol or organization with Zeppelin?
Ask for help and follow progress at: https://zeppelin-slackin.herokuapp.com/
Interested in contributing to Zeppelin?
- Framework proposal and roadmap: https://medium.com/zeppelin-blog/zeppelin-framework-proposal-and-development-roadmap-fdfa9a3a32ab#.iain47pak
- Issue tracker: https://github.com/OpenZeppelin/zeppelin-solidity/issues
- Contribution guidelines: https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/CONTRIBUTING.md
The MIT License (MIT)¶
Copyright (c) 2016 Smart Contract Solutions, Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
TODO¶
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