Burp Suite extension for encoding/decoding EVM calldata


  1. Burp Suite
  2. Java 8+
  3. Python 2.7


  1. clone this repository
  2. in Burp, go to Extender->Options
    1. in the Java Environment section add <install_dir>/unblocker/ as “Folder for loading library JAR files”
    2. in the Python Environment section:
    3. add <install_dir>/unblocker/jython-standalone-2.7.2.jar as “Location of Jython standalone JAR file”
    4. add <install_dir>/unblocker/src/lib as “Folder for loading modules”
  3. in Burp, go to Extender->Extensions
    1. click “Add” in the Burp Extensions section and select <install_dir>/unblocker/unblocker.py as “Extension file (.jar)”–Burp will detect the filetype automatically
    2. confirm the installation by approving all subsequent modal windows


Unblocker features ABI-less EVM calldata decoding but you can also provide the ABI yourself if you know it.
Encoding does require you to provide some ABI.

  • ABI has to be provided like so: transfer(address, uint256).
  • Input data (for decoding) can be provided with or without 0x prepended.
  • Input data strings (for encoding) have to be provided like so: "s'hello, world'"
  • Input data bytes (for encoding) have to be provided like so: "b'deadbeef'"
  • Input data structs (for encoding) have to be provided with square brackets instead of parenthesis, like so: ["s'some string'", true, 123]


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