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Whaler is a Go program which is designed to reverse engineer docker images into the Dockerfile that created it. It currently performs the following actions

  • Generates a Dockerfile from an Image
  • Searches added filenames for potential secret files
  • Extracts files that were added by the Docker ADD/COPY Instructions
  • It also displays misc. information such as ports open, the user it runs as and environment variables.

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You can read more about this on my blog Here

How to run it

The easiest way is to run the tool in docker container:

docker pull pegleg/whaler
docker run -t --rm -v /var/run/docker.sock:/var/run/docker.sock:ro pegleg/whaler -sV=1.36 nginx:latest
docker build --rm -t pegleg/whaler .
alias whaler="docker run -t --rm -v /var/run/docker.sock:/var/run/docker.sock:ro pegleg/whaler"
whaler -sV=1.36 nginx:latest

This tool will pull target docker image automatically. Parameter -sV=1.36 is not always required.

How to build it

Git clone the project into your $GOPATH/src directory and perform the following command

go get -u
cd $GOPATH/src/
go build .

How to run it

Usage of ./Whaler:
  -f string
    	File containing images to analyze seperated by line
    	Filters filenames that create noise such as node_modules. Check ignore.go file for more details (default true)
  -sV string
    	Set the docker client ID to a specific version -sV=1.36
  -v	Print all details about the image
  -x	Save layers to current directory