Security analysis tool for Ethereum smart contracts
Mythril is a security analysis tool for Ethereum smart contracts. It uses concolic analysis to detect various types of issues. Use it to analyze source code or as a nmap-style black-box blockchain scanner (an “ethermap” if you will).
Installation and setup
Install from Pypi:
$ pip install mythril
Or, clone the GitHub repo to install the newest master branch:
$ git clone https://github.com/b-mueller/mythril/ $ cd mythril $ python setup.py install
Note that Mythril requires Python 3.5 to work.
Whenever you disassemble or analyze binary code, Mythril will try to resolve function names using its local signature database. The database must be provided at ~/.mythril/signatures.json. You can start out with the default file as follows:
$ cd ~/.mythril $ wget https://raw.githubusercontent.com/b-mueller/mythril/master/signatures.json
When you analyze Solidity code, new function signatures are added to the database automatically.
Run myth -x with one of the input options described below to run the analysis. This will run the Python modules in the /analysis/modules directory.
Mythril detects a range of security issues, including integer underflows, owner-overwrite-to-Ether-withdrawal, and others. However, the analysis will not detect business logic issues and is not equivalent to formal verification.
Analyzing Solidity code
In order to work with Solidity source code files, the solc command line compiler needs to be installed and in path. You can then provide the source file(s) as positional arguments, e.g.:
$ myth -x myContract.sol
Alternatively, compile the code on Remix and pass the runtime binary code to Mythril:
$ myth -x -c "0x5060(...)"
If you have multiple interdependent contracts, pass them to Mythril as separate input files. Mythril will map the first contract to address “0x0000(..)”, the second one to “0x1111(…)”, and so forth (make sure that contract addresses are set accordingly in the source). The contract passed in the first argument will be executed as the “main” contract.
$ myth -x myContract.sol myLibrary.sol
Working with on-chain contracts
To analyze contracts on the blockchain you need an Ethereum node. By default, Mythril will query a local node via RPC. Alternatively, you can use INFURA:
$ myth --infura-mainnet -x -a 0x5c436ff914c458983414019195e0f4ecbef9e6dd
If you are planning to do batch operations or use the contract search features, running a go-ethereum node is recommended. Start your local node as follows:
$ geth --rpc --rpcapi eth,debug --syncmode fast
Specify the target contract with the -a option:
$ myth -x -a 0x5c436ff914c458983414019195e0f4ecbef9e6dd -v1
Adding the -l flag will cause Mythril to automatically retrieve dependencies, such as library contracts:
$ myth -x -a 0xEbFD99838cb0c132016B9E117563CB41f2B02264 -l -v1
Control flow graph
The -g FILENAME option generates an interactive jsViz graph:
$ myth -g ./graph.html -a 0xEbFD99838cb0c132016B9E117563CB41f2B02264 -l
[STRIKEOUT:The “bounce” effect, while awesome (and thus enabled by default), sometimes messes up the graph layout.] Try adding the --enable-physics flag for a very entertaining “bounce” effect that unfortunately completely destroys usability.
Mythril builds its own contract database to enable fast search operations. This enables operations like those described in the legendary “Mitch Brenner” blog post in [STRIKEOUT:seconds] minutes instead of days. Unfortunately, the initial sync process is slow. You don’t need to sync the whole blockchain right away though: If you abort the syncing process with ctrl+c, it will be auto-resumed the next time you run the --init-db command.
$ myth --init-db Starting synchronization from latest block: 4323706 Processing block 4323000, 3 individual contracts in database (...)
The default behavior is to only sync contracts with a non-zero balance. You can disable this behavior with the --sync-all flag, but be aware that this will result in a huge (as in: dozens of GB) database.
Searching from the command line
The search feature allows you to find contract instances that contain specific function calls and opcode sequences. It supports simple boolean expressions, such as:
$ myth --search "func#changeMultisig(address)#" $ myth --search "code#PUSH1 0x50,POP#" $ myth --search "func#changeMultisig(address)# and code#PUSH1 0x50#"
Reading contract storage
You can read the contents of storage slots from a deployed contract as follows.
./myth --storage 0 -a "0x76799f77587738bfeef09452df215b63d2cfb08a" 0x0000000000000000000000000000000000000000000000000000000000000003
Use the -d flag to disassemble code. The disassembler accepts a bytecode string or a contract address as its input.
$ myth -d -c "0x6060" 0 PUSH1 0x60
Specifying an address via -a ADDRESS will download the contract code from your node.
$ myth -d -a "0x2a0c0dbecc7e4d658f48e01e3fa353f44050c208" 0 PUSH1 0x60 2 PUSH1 0x40 4 MSTORE (...) 1135 - FUNCTION safeAdd(uint256,uint256) - 1136 CALLVALUE 1137 ISZERO
It is often useful to find other contracts referenced by a particular contract. E.g.:
$ myth --search "code#DELEGATECALL#" Matched contract with code hash 07459966443977122e639cbf7804c446 Address: 0x76799f77587738bfeef09452df215b63d2cfb08a, balance: 1000000000000000 $ myth --xrefs -a 0x76799f77587738bfeef09452df215b63d2cfb08a 5b9e8728e316bbeb692d22daaab74f6cbf2c4691
Calculating function hashes
To print the Keccak hash for a given function signature:
$ myth --hash "setOwner(address)" 0x13af4035