· May 22, 2023

How do you sign a JWT request?

The below code gives a empty string output.

Set secretSigned = ##class(%SYSTEM.Encryption).RSASHA1Sign(512,token,secret)

The secret is a valid PEM private key.

Is there any more logic that needs to prefix this method call?

Product version: IRIS 2021.1
Discussion (10)2
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I just tried RSASHASign() myself and a signature was returned, using your call:

Set in=##class(%Stream.FileCharacter).%New()
Do in.LinkToFile("/home/jeff/sample.jwt")
Set token=in.Read()
Set key=##class(%Stream.FileCharacter).%New()
Do key.LinkToFile("/home/jeff/sample.pem")
Set secret=key.Read()
Set sig=##class(%SYSTEM.Encryption).RSASHASign(512,token,secret)

The return value will be the signature only, though, not a signed JWT. If you want the latter, see the ObjectToJWT() method in  %OAuth2.JWT - InterSystems IRIS for Health 2021.1.

     Set encodedToken = ..UrlEncoding($System.Encryption.Base64Encode(..header.%ToJSON(),1)_
     "."_ $System.Encryption.Base64Encode(..payload.%ToJSON(),1))

     Set tFile=##class(%Stream.FileBinary).%New()
     Set tFile.Filename=secretLocation
     Set pemPrviateKey = tFile.Read($$$MaxLocalLength)
     Set secretSigned = ##class(%SYSTEM.Encryption).RSASHASign(512,encodedToken,pemPrviateKey)
     Set signature = $Translate($System.Encryption.Base64Encode(secretSigned, 1),"+/=","-_")
    Return encodedToken_"."_signature

In my scenario the token is two encrypted JSONs appended together and the signature gets appended to the end.

The code above doesn't produce anything at secretSigned, the PEM encoded private key is valid.

Can you try the code I posted above, substituting appropriate paths/filenames in the calls to the LinkToFile() methods? Any file will do for the in stream, as long as file/directory permissions permit. This at least would tell us whether the issue is with the key file or the JWT you're attempting to encrypt.

I've tried this on I4H 2023.1 and Health Connect 2021.1.2 and the RSASHASign() method has not failed to generate a signature unless the key was passphrase-protected or not readable (due to file ownership/permissions) by the process opening it.