A simple utility to generate and decode JSON Web Tokens (JWTs) that can be used to authenticate against web applications.

The code is released under the Apache 2 Open Source License.

See JWT-OPA for an example of how JWTs can be used to authenticate/authorize access to protected online resources/applications.

Usage

Use --help (or -h) for a full list of options and their meaning.

To generate a JWT (optionally signed with an empty passphrase), use:

$ echo '{"sub": "marco", "roles": [ "USER" ]}' | ./jwtie.py

eyJ0eXAiOiJKV .... ktOykD4

To decode a JWT that was generated by this or another tool (so long as the JWT is not encrypted), use the -d flag:

echo "eyJ0eXAiOiJKV1 ... ktOykD4" | ./jwtie.py -d
{
  "sub": "marco",
  "roles": [
    "USER"
  ]
}

Optionally, add the --header flag to emit the JWT header too.

Validating Signed JWTs

To use a shared secret, set it in the $JWT_SECRET env var (if you want to use a different variable name, use --secret-env SECRET_ENV):

$ export JWT_SECRET="mypazzfrase"

# If we use the JWT generated earlier, it won't pass validation
$ echo "eyJ0eXAiOiJKV ... ktOykD4" | ./jwtie.py -d -v         
ERROR: could not process JWT: Signature verification failed

# We must use --validate, -v when generating it:
echo '{"sub": "marco", "roles": [ "USER" ]}' | ./jwtie.py -v
eyJ0eXAiO .... mJLKsPkblw  # <<-- note the last part, the signature is different


echo "eyJ0eXAiO ... mJLKsPkblw" | ./jwtie.py -d -v --header
{
  "typ": "JWT",
  "alg": "HS256"
}
{
  "sub": "marco",
  "roles": [
    "USER"
  ]
}

Note how the header carries information about the signature algorithm.

NOTE Still TODO adding support for asymmetric and key-based signature algorithms

Raw output

If the output of jwtie needs to be fed into other utilities, pretty-printing it may be unnecessary or even undesirable; in such cases use --raw to get a simple JSON string:

$ echo "eyJ0eXAiO ... mJLKsPkblw" | ./jwtie.py -d --raw
{"sub": "marco", "roles": ["USER"]}

# This is pointless, really, but proves a point.
$ echo "eyJ0eXAiO ... mJLKsPkblw" | ./jwtie.py -d --raw \
  | cut -d ',' -f 2 | cut -d '}' -f 1

 "roles": ["USER"]

Install

While not available yet, this will soon be made available on PyPi for installation via pip:

$ pip install jwtie