i am preparing a new training lab (WSO2) where the X-JWT-Assertion Header needs to be decoded and basically the Json payload needs to be in the body. Originally i have a backend service but that requires another instance. I saw that i could get the header into the response { \"copiedHeader\": \"{{request.headers.X-JWT-Assertion}}\" } however, decoding the payload using : { "message": "Extracted user from custom JWT assertion header", "userId": "{{#assign 'jwtPayload'}}{{base64 (regexExtract request.headers.X-JWT-Assertion '([^.]+)\\.([^.]+)\\.([^.]+)' group=2) decode=true}}{{/assign}}{{#assign 'claims'}}{{parseJson jwtPayload}}{{/assign}}{{claims.sub}}" } give 500 [ERROR] 126 java.lang.IllegalArgumentException: Illegal base64 character 5b when i do this { "status": "success", "userId": "{{#assign 'jwtSegments'}}{{split request.headers.[X-JWT-Assertion] '.'}}{{/assign}}{{#assign 'payloadSegment'}}{{jwtSegments.[1]}}{{/assign}}{{#assign 'jwtPayload'}}{{base64 payloadSegment decode=true}}{{/assign}}{{#assign 'claims'}}{{parseJson jwtPayload}}{{/assign}}{{claims.sub}}", "apiName": "{{#assign 'jwtSegments'}}{{split request.headers.[X-JWT-Assertion] '.'}}{{/assign}}{{#assign 'payloadSegment'}}{{jwtSegments.[1]}}{{/assign}}{{#assign 'jwtPayload'}}{{base64 payloadSegment decode=true}}{{/assign}}{{#assign 'claims'}}{{parseJson jwtPayload}}{{/assign}}{{formData claims 'wso2.org/claims/apiname'}}" } there is no error but an empty payload "status": "success", "userId": "", "apiName": "" } what are the right steps to decode this JWT X-JWT-Assertion eyJ4NXQiOiJOR1k1T1dVNU5EVTNaakl6TjJVM1kyVTNNV1JqT0RkbFlUUXhaRE16TVRZMVpEbGxZemN4TWc9PSIsImtpZCI6IlEwNDliRzlqWVd4b2IzTjBMQ0JQVlQxWFUwOHlMQ0JQUFZkVFR6SXNJRXc5VFc5MWJuUmhhVzRnVm1sbGR5d2dVMVE5UTBFc0lFTTlWVk1qTlRrd056WTFOVGN3TmpJMU1qQTBNVGN3T1RBM05qTXpNVEU1T0RnNE5qVXhOVGM0T0RFeU5URTFNekF5TVRNeSIsInR5cCI6IkpXVCIsImFsZyI6IlJTMjU2In0.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.azO/wET5wRF+zR/V9exHTMCDxxJRD5llqz15Hlj7V6t9/TfJJ1lgx4fADbkj2oO2qES02Je3JHIPOya7fkdl3mhdYpXdCSO6PgNNbrJwJ8Y5SIKeTtZ0h/82d2OVgiKE7kOK73QOBCkzth6/jpqEwUMyiBgVWAXLFmxdlO7qEq1f2LS25HEICodAVYfBEQQ/XfKeEpREN1f0vqOKynJZUaLo0z8Oq1jQ8UpmZSAYh6eJhjHtZQzlXj6EIEZVXhUXmTNAmNTpksar4rZcOLkMF+zfOA3RHhsktSdcXsPVbRt7M8K0dUXVWGT9NJ+oHzDktLtDxD6j/js+4X0NddEbRg

Hi @rob.blaauboer, I can’t get your example JWT to parse in jwt.io. Seems the signature is encrypted maybe? This might also be confusing the WM parser.

hi @Tom if you go to wso2-cs.github.io/cs-tools and use the JWT decoder you can decode it. it is a bit tricky

This seems to work:

{{#trim}}
{{val request.headers.[X-JWT-Assertion].[0] assign='jwtString'}}
{{val (split jwtString '.') assign='jwtSegments'}}
{{val (lookup (split jwtString '.') '[1]') assign='payloadSegment'}}
{{val (base64 payloadSegment decode=true) assign='jwtPayload'}}
{{val (parseJson jwtPayload) assign='jwtClaims'}}
{{#formatJson}}
{
  "status": "success",
  "userId":  "{{jwtClaims.sub}}",
  "apiName": "{{lookup jwtClaims '[<http://wso2.org/claims/apiname]'}}>"
}
{{/formatJson}}
{{/trim}}

great @Tom thanks. I am impressed by the functionality of the product. I am moving more and more of my training backends to wiremock. We can take a look to see if i can incorporate more

That's great to hear, thanks for the kind feedback! And please don't hesitate to shout if we can help with anything else.