GenerateJWT ( header ; claim ; algorithm ; privatekey ; password )

To generate a JWT using native FileMaker Functionality

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Robert D Trammel - Show more from this author
https://www.linkedin.com/in/robertdtrammel/

Sample input:

GenerateJWT( $header; $claim; "SHA256"; $privateRSA; "" )

Sample output:

eyJhbGciOiJIUzI1NiIsInR5cGUiOiJKV1QifQ.eyJIZWxsbyI6IndvcmxkIn0.Pwaksjakdhfiwjokso

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

//Requires FileMaker 18 and up to use the CryptGenerateSignature function
//header expects a JSON object
//claim expects a JSON object
//private key is the private RSA certificate generated by whatever service you're using
//password is optional
//algorithm default is SHA512, see https://help.claris.com/en/pro-help/content/cryptauthcode.html for available algorithms

Let([
   algorithm = If( IsEmpty( algorithm ); "SHA512"; algorithm );
   head = Substitute( Base64EncodeRFC ( 4648; header );["=";""];["+";"-"];["/";"_"]);
   claim = Substitute( Base64EncodeRFC ( 4648; claim );["=";""];["+";"-"];["/";"_"]);
   signature = Substitute ( Base64EncodeRFC ( 4648; CryptGenerateSignature( head & "." & claim; algorithm; privateKey; password )  ) ;["=";""];["+";"-"];["/";"_"])
];
   head & "." & claim & "." & signature
)

Developed with help from the amazing post at - https://msdev.nz/generating-jwts-in-native-filemaker/

I'm not sure I would have figured out that I needed to do more than blank out the "=" signs in enough time to finish the project without that much needed article.

This is intended to allow you to generate JSON Web Tokens using FileMaker native functionality. At which point, you would just pass it to whatever service you're using it for. In my case, I used it to authenticate a google service.

You can also validate your JSON Web Tokens and learn more about them over at https://jwt.io

Google Specific Guides:
Scopes: https://developers.google.com/identity/protocols/oauth2/scopes#gmail
JWT config: https://developers.google.com/identity/protocols/oauth2/service-account#httprest

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Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

GenerateJWT ( header ; claim ; algorithm ; privatekey ; password )

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