Using openssl from a docker container

Why

Openssl is a great tool to generate and transform all sorts of cryptographic certificates. There isn't an official distribution on Windows, so one has to use some 3rd party version. It can be a hassle to get it installed. But, if you have docker running, you're all set. Fetch a small container, and start running it.

How

You can copy any these functions into your shell profile, the script will fetch openssl when needed, create an image. And run openssl in your current directory. You can remove the cleanup step if you don't want the containers to be deleted after usage. Since we're using docker run a new container will be created every time, we probably don't want them hanging around.

Script for Fish shell

function openssl
    set --local images (docker images -q openssl:latest)
    if test -z "$images"
        echo 'openssl:latest image does not exist, creating it'
        docker run --name openssl alpine apk add --no-cache openssl
        docker commit openssl openssl:latest
        docker rm openssl
    end

    # cleanup the existing containers
    set --local containers (docker ps -a | grep 'openssl:latest' | awk '{ print $1}')
    if test -n "$containers"
        docker rm $containers > /dev/null
    end

    docker run -w /home -v (pwd):/home -it openssl:latest /usr/bin/openssl $argv
end

Script for Bash shell

function openssl {
    images=$(docker images -q openssl:latest)
    if  [ -z "$images" ]; then
        echo 'openssl:latest image does not exist, creating it'
        docker run --name openssl alpine apk add --no-cache openssl
        docker commit openssl openssl:latest
        docker rm openssl
    fi

    # cleanup the existing containers
    containers=$(docker ps -a | grep 'openssl:latest' | awk '{ print $1}')
    if [ -n "$containers" ]; then
        docker rm ${containers} > /dev/null
    fi

    docker run -w /home -v $(pwd):/home -it openssl:latest /usr/bin/openssl $@
}

Script for PowerShell

function openssl {
    $images = $(docker images -q openssl:latest)
    if (-not $images) {
        Write-Host "openssl:latest image does not exist, creating it"
        docker run --name openssl alpine apk add --no-cache openssl
        docker commit openssl openssl:latest
        docker run openssl
    }

    $containers = $(docker ps -a | selec-string 'openssl:latest' | %{ $_.ToString().Split(' ')[0]; })
    if ($containers) {
        docker rm $containers | Out-Null
    }

    docker run -w /home -v ${pwd}:/home -it openssl:latest /usr/bin/openssl $args
}

Then you can run openssl from command line.

> openssl help
Standard commands
asn1parse         ca                ciphers           cms
crl               crl2pkcs7         dgst              dhparam
dsa               dsaparam          ec                ecparam
enc               engine            errstr            gendsa
genpkey           genrsa            help              list
nseq              ocsp              passwd            pkcs12
pkcs7             pkcs8             pkey              pkeyparam
pkeyutl           prime             rand              rehash
req               rsa               rsautl            s_client
s_server          s_time            sess_id           smime
speed             spkac             srp               storeutl
ts                verify            version           x509

Message Digest commands (see the `dgst' command for more details)
blake2b512        blake2s256        gost              md4
md5               rmd160            sha1              sha224
sha256            sha3-224          sha3-256          sha3-384
sha3-512          sha384            sha512            sha512-224
sha512-256        shake128          shake256          sm3

Cipher commands (see the `enc' command for more details)
aes-128-cbc       aes-128-ecb       aes-192-cbc       aes-192-ecb
aes-256-cbc       aes-256-ecb       aria-128-cbc      aria-128-cfb
aria-128-cfb1     aria-128-cfb8     aria-128-ctr      aria-128-ecb
aria-128-ofb      aria-192-cbc      aria-192-cfb      aria-192-cfb1
aria-192-cfb8     aria-192-ctr      aria-192-ecb      aria-192-ofb
aria-256-cbc      aria-256-cfb      aria-256-cfb1     aria-256-cfb8
aria-256-ctr      aria-256-ecb      aria-256-ofb      base64
bf                bf-cbc            bf-cfb            bf-ecb
bf-ofb            camellia-128-cbc  camellia-128-ecb  camellia-192-cbc
camellia-192-ecb  camellia-256-cbc  camellia-256-ecb  cast
cast-cbc          cast5-cbc         cast5-cfb         cast5-ecb
cast5-ofb         des               des-cbc           des-cfb
des-ecb           des-ede           des-ede-cbc       des-ede-cfb
des-ede-ofb       des-ede3          des-ede3-cbc      des-ede3-cfb
des-ede3-ofb      des-ofb           des3              desx
rc2               rc2-40-cbc        rc2-64-cbc        rc2-cbc
rc2-cfb           rc2-ecb           rc2-ofb           rc4
rc4-40

Conclusion

Docker is a good tool to run Linux applications everywhere. Especially if the tool and the base image(in our case Alpine) are small. The scripts above will get you a openssl running locally in no time.