Secure an api with jwt verifiers

A Jwt verifier is the guard that verifies the signature of tokens in requests.

A verifier can obvisouly verify or generate.

Before you start

If you already have an up and running otoroshi instance, you can skip the following instructions

curl -L -o otoroshi.jar 'https://github.com/MAIF/otoroshi/releases/download/v17.9.2/otoroshi.jar'

java -Dotoroshi.adminPassword=password -jar otoroshi.jar 

curl -X POST 'http://otoroshi-api.oto.tools:8080/api/routes' \
-H "Content-type: application/json" \
-u admin-api-apikey-id:admin-api-apikey-secret \
-d @- <<'EOF'
{
  "name": "my-service",
  "frontend": {
    "domains": ["myservice.oto.tools"]
  },
  "backend": {
    "targets": [
      {
        "hostname": "request.otoroshi.io",
        "port": 443,
        "tls": true
      }
    ]
  }
}
EOF

Your first jwt verifier

Let’s start by validating all incoming request tokens tokens on our simple route created in the Before you start section.

1. Navigate to the simple route
2. Search in the list of plugins and add the Jwt verification only plugin on the flow
3. Click on Start by select or create a JWT Verifier
4. Create a new JWT verifier
5. Set simple-jwt-verifier as Name
6. Select Hmac + SHA as Algo (for this example, we expect tokens with a symetric signature), 512 as SHA size and otoroshi as HMAC secret
7. Confirm the creation

Save your route and try to call it

curl -X GET 'http://myservice.oto.tools:8080/' --include

This should output :

{
    "Otoroshi-Error": "error.expected.token.not.found"
}

A simple way to generate a token is to use jwt.io. Once navigate, define HS512 as alg in header section and insert otoroshi as verify signature secret.

Once created, copy-paste the token from jwt.io to the Authorization header and call our service.

# replace xxxx by the generated token
curl -X GET \
  -H "X-JWT-Token: xxxx" \
  'http://myservice.oto.tools:8080'

This should output a json with X-JWT-Token in headers field. Its value is exactly the same as the passed token.

{
  "method": "GET",
  "path": "/",
  "headers": {
    "host": "request.otoroshi.io",
    "X-JWT-Token": "eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.ipDFgkww51mSaSg_199BMRj4gK20LGz_czozu3u8rCFFO1X20MwcabSqEzUc0q4qQ4rjTxjoR4HeUDVcw8BxoQ",
    ...
  }
}

Verify and generate a new token

An other feature is to verify the incomings tokens and generate new ones, with a different signature and claims.

Let’s start by extending the previous verifier.

1. Jump to the Verif Strategy field and select Verify and re-sign JWT token.
2. Edit the name with jwt-verify-and-resign
3. Remove the default field in Verify token fields array
4. Change the second Hmac secret in Re-sign settings section with otoroshi-internal-secret
5. Save your verifier.

Note : the name of the verifier doesn’t impact the identifier. So you can save the changes of your verifier without modifying the identifier used in your call.

# replace xxxx by the generated token
curl -X GET \
  -H "Authorization: xxxx" \
  'http://myservice.oto.tools:8080'

This should output a json with authorization in headers field. This time, the value are different and you can check his signature on jwt.io (the expected secret of the generated token is otoroshi-internal-secret)

Verify, transform and generate a new token

The most advanced verifier is able to do the same as the previous ones, with the ability to configure the token generation (claims, output header name).

Let’s start by extending the previous verifier.

1. Jump to the Verif Strategy field and select Verify, transform and re-sign JWT token.

2. Edit the name with jwt-verify-transform-and-resign

3. Remove the default field in Verify token fields array
4. Change the second Hmac secret in Re-sign settings section with otoroshi-internal-secret
5. Set Internal-Authorization as Header name
6. Set key on first field of Rename token fields and from-otoroshi-verifier on second field
7. Set generated-key and generated-value as Set token fields
8. Add generated_at and ${date} as second field of Set token fields (Otoroshi supports an expression language)
9. Save your verifier and try to call your service again.

This should output a json with authorization in headers field and our generate token in Internal-Authorization. Once paste in jwt.io, you should have :

You can see, in the payload of your token, the two claims from-otoroshi-verifier and generated-key added during the generation of the token by the JWT verifier.