a-h/jwtproxy

A reverse proxy which validates access using JWT.

Reverse Proxy with JWT Authentication

A reverse proxy which rejects incoming requests which:

• Don't have an authorization HTTP header.
• Have an authorization header which doesn't contain a JWT.
• Have an authorization header which contains an expired or invalid JWT.
• Have an authorization header which contains a JWT which has an unrecognised issuer.
• Have an authorization header which could not be validated using the public key corresponding to the issuer.

Usage

• Decide on an issuer (iss) value to use for each API client.
  • This is usually a domain, e.g. example.com.
• Get the API consumer to generate a private RSA key, and send you the public key.
• Setup the proxy to allow requests from the API consumer using environment variables, or command line flags.
• Get the API consumer to send HTTP requests which set an authorization header containing a JWT signed with the private key.

Generating RSA keys

Generate a private key. (example_private.pem).

openssl genrsa -out example_private.pem 2048

Extract the public key. (example_public.pem)

openssl rsa -in example_private.pem -outform PEM -pubout -out example_public.pem

You start the proxy passing it a map of issuers to public keys as environment variables or a file.

Minimal JWT

The JWT passed by the client must meet the following criteria:

Header

The JWT must be signed using the RS256 algorithm.

{
  "alg": "RS256",
  "typ": "JWT"
}

Payload

The payload must contain an issuer agreed between the two parties, and an expiration timestamp.

{
  "iss": "custom_issuer.example.com",
  "exp": "1504282460"
}

Configuration

Configuration can be provided by command line flags (specified by -name) or by environment variables.

JWTPROXY_REMOTE_URL / -remoteURL

The URL to proxy requests to.

JWTPROXY_REMOTE_HOST_HEADER / -remoteHostHeader

The HTTP host header to send to the remote endpoint (useful if the remote endpoint is not using DNS).

JWTPROXY_LISTEN_PORT / -port

The TCP port to open up the proxy on.

JWTPROXY_HEALTHCHECK_URI / -health

The location that the proxy should use to respond to health check HTTP requests (defaults to /health).

JWTPROXY_PREFIX / -prefix

The prefix to strip from incoming requests applied to the remote URL, e.g to make incoming HTTP request /api/user?id=1 map to outgoing HTTP request /user?id=1

JWTPROXY_ISSUER_ / JWTPROXY_PUBLIC_KEY_

It's possible to set issuer to public key maps by using environment variables alone.

To set the issuer "example.com" to a public key, create two environment variables with a matching suffix for the JWTPROXY_ISSUER_ and JWTPROXY_PUBLIC_KEY_ keys, e.g.:

JWTPROXY_ISSUER_0=example.com
JWTPROXY_PUBLIC_KEY_0=-----BEGIN PUBLIC KEY-----MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxFj26fqmulXntc7kCp9tMs6MEQUsk2r16Jd6k+aZSaLBo0dVgP77q1os10gZT4N0gYH6NsbVqP4+wWAUIDiemhpxq986z5mtB/lGvmHmaQcK/bOnEvcLWinHJZIla1m2RF7diN5/WBRNh8CyYMiW+BV/6dngknBtP7bDpnCkYrySaOQtKRvrech1UFRKgQjD8bprrcUmOFWYrmKe2NCxcQs9RhYuACt3Du2Z4VwVWN2xvL5LlZdWK7jLENe3MkOZU5WcwA7n+K/tulqA9uNRv8cRIL/y8BUwUsUoqBiyVZXQUa7BgE82GoTXtv3uqkN/yZxnlEcaJW5BD1nFzuvuyQIDAQAB-----END PUBLIC KEY-----

JWTPROXY_CONFIG / -keys

The location of a JSON file containing a map of issuers to public keys, e.g.:

JWTPROXY_CONFIG=keys.json

JSON does not support newlines, so the public key value will need to have them replaced with \n in JSON, e.g. by cat dev_pub.pem | tr '\n' '_' | sed 's/_/\\n/g' > dev_pub2.pem

• keys.json

{
    "example.com": "-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxFj26fqmulXntc7kCp9t\nMs6MEQUsk2r16Jd6k+aZSaLBo0dVgP77q1os10gZT4N0gYH6NsbVqP4+wWAUIDie\nmhpxq986z5mtB/lGvmHmaQcK/bOnEvcLWinHJZIla1m2RF7diN5/WBRNh8CyYMiW\n+BV/6dngknBtP7bDpnCkYrySaOQtKRvrech1UFRKgQjD8bprrcUmOFWYrmKe2NCx\ncQs9RhYuACt3Du2Z4VwVWN2xvL5LlZdWK7jLENe3MkOZU5WcwA7n+K/tulqA9uNR\nv8cRIL/y8BUwUsUoqBiyVZXQUa7BgE82GoTXtv3uqkN/yZxnlEcaJW5BD1nFzuvu\nyQIDAQAB\n-----END PUBLIC KEY-----"
}

Running it

Command line

jwtproxy -remoteURL http://example.com:8080 -keys keys.json

Docker

Or you can run the Docker container, using environment variables to pass in required data. In this case, exposing the linked container 'hopeful_pike'.

docker run --link hopeful_pike -p 9090:9090/tcp --rm -e "JWTPROXY_LISTEN_PORT=9090" -e "JWTPROXY_REMOTE_URL=http://hopeful_pike:8080" -v /users/me/keys.json:/keys.json -e "JWTPROXY_CONFIG=keys.json" adrianhesketh/jwtproxy

Usage

Use curl to access your local proxy.

curl -H "Authorization: Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpYXQiOiIxNDg2MzkyMjAwIiwiZXhwIjoiMTU4NjM5MjIwMCIsImlzcyI6ImV4YW1wbGUuY29tIn0.McHwUVbe96y-vaTOExPjANm8e8p0v6I7puPf74SV7Jn-QYprrhLlklnBP4MEF77v0LIBUFKgzpOMfldCONId3ktOFOf0117x9iWG3J-Zf6Ni3HinhA9U1pPU7_OhTtkXacmgats8tLWAqmOz46NeyAmHS_dkvodUUPpcHY-AqQtzM4ql6RZpMDstz5dFJWZh9P0_prPknoI-argt2jn-KGajCOIghcGxNarylq5oX62rT9AavavyWGnJW0zLnP9qtIuChzigU542Nbg7y6_E7FaVA2cPICPuiPehn6vVTKuVil0o2SJgFD2J2HQfxa0iDrc8HzbubMGJcw7Vlpkk0w" http://localhost:9090

Testing

Generate a JWT with an appropriate payload at [jwt.io], or using a library:

• iat
  • issued at time: The time when the JWT was generated as a Unix timestamp.
• exp
  • expiry time: The time when the JWT expires, may be rejected by the server if the difference between exp and iat is too long.
• iss
  • the issuer, used to look up the correct public key to use to validate the JWT signature.

{
  "iat": "1486392200",
  "exp": "1586392200",
  "iss": "example.com"
}

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpYXQiOiIxNDg2MzkyMjAwIiwiZXhwIjoiMTU4NjM5MjIwMCIsIm5hbWUiOiJBZHJpYW4gSGVza2V0aCJ9.d45Or2h-lApJ4FK2pKj0ZIRdDTULsNl1z-V3LfQFvno

To sign and validate using the command line (to compare against the Go implementation):

# SHA256 hash the data.
openssl dgst -sha256 -binary data.json > hash.bin
# base64 encode the hash so that it should match the value of the X-Sha256hash HTTP header.
openssl base64 -e -in hash.bin -out hash.b64

# Sign the hash.
openssl rsautl -in hash.bin -inkey private_test.pem -sign -out signature.bin
# base64 encode the signature so that it should match the value of the X-Signature HTTP header.
openssl base64 -e -in signature.bin -out signature.b64

# Verify the signature.
openssl rsautl -in signature.bin -verify -inkey public_test.pem -pubin > verified.bin
openssl base64 -e -in verified.bin -out verified.b64

# Compare the original hash to the hash created by the verification routine.
# The two files should be equal.
cat hash.b64
cat verified.b64

jwtproxy's Issues

Ensure hardening according to https://blog.cloudflare.com/exposing-go-on-the-internet/

Logs lack detail

Would like to log:

• Whether the request was successfully authenticated using JWT and the issuer which was used
• HTTP response code, size and other data from the remote endpoint
• Time taken for the remote endpoint

Support URLs in iss

Right now, this is almost perfect for what I want to achieve, except that the JWT I'm using has an iss field of https://subdomain.auth0.com.

As it's auth0, I can't change this.

If I set JWTPROXY_ISSUER_0=subdomain.auth0.com then I get iss not valid, because it's not an exact match.

I'll use a library in my app now, but something like this repo, logically separated seems ideal 👍