(PureBasic) Verify JWT with EdDSA / Ed25519 Signature

Note: This example requires Chilkat v9.5.0.84 or greater.

Demonstrates how to verify a JWT that was signed using an Ed25519 private key.

This example verifies the EdDSA signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original data.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkPublicKey.pb"
IncludeFile "CkJwt.pb"

Procedure ChilkatExample()

    ; Demonstrates how to verify a JWT with an EdDSA/Ed25519 Signature
    ; *** Requires Chilkat v9.5.0.84 or greater.

    ; This example assumes the Chilkat API to have been previously unlocked.
    ; See Global Unlock Sample for sample code.

    ; Use this Ed25519 public key for verification

    jsonPubKey.s = "{" + Chr(34) + "kty" + Chr(34) + ": " + Chr(34) + "OKP" + Chr(34) + "," + Chr(34) + "alg" + Chr(34) + ": " + Chr(34) + "EdDSA" + Chr(34) + "," + Chr(34) + "crv" + Chr(34) + ": " + Chr(34) + "Ed25519" + Chr(34) + "," + Chr(34) + "x" + Chr(34) + ": " + Chr(34) + "11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo" + Chr(34) + "}"

    pubKey.i = CkPublicKey::ckCreate()
    If pubKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkPublicKey::ckLoadFromString(pubKey,jsonPubKey)
    If success = 0
        Debug CkPublicKey::ckLastErrorText(pubKey)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf

    jwt.i = CkJwt::ckCreate()
    If jwt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    token.s = "eyJhbGciOiJFZERTQSJ9.RXhhbXBsZSBvZiBFZDI1NTE5IHNpZ25pbmc.hgyY0il_MGCjP0JzlnLWG1PPOt7-09PGcvMg3AIbQR6dWbhijcNR4ki4iylGjg5BhVsPt9g7sVvpAr_MuM0KAg"

    ; First verify the signature.
    sigVerified.i = CkJwt::ckVerifyJwtPk(jwt,token,pubKey)
    Debug "verified: " + Str(sigVerified)

    If sigVerified = 0
        Debug CkJwt::ckLastErrorText(jwt)
        CkPublicKey::ckDispose(pubKey)
        CkJwt::ckDispose(jwt)
        ProcedureReturn
    EndIf

    ; Let's see if the time constraints, if any, are valid.
    ; The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
    ; If the current system time is before the "nbf" time, or after the "exp" time,
    ; then IsTimeValid will return false/0.
    ; Also, we'll allow a leeway of 60 seconds to account for any clock skew.
    ; Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
    leeway.i = 60
    bTimeValid.i = CkJwt::ckIsTimeValid(jwt,token,leeway)
    Debug "time constraints valid: " + Str(bTimeValid)

    ; Recover the original data (the payload).
    payload.s = CkJwt::ckGetPayload(jwt,token)
    Debug payload

    ; Recover the original JOSE header in the same way:
    joseHeader.s = CkJwt::ckGetHeader(jwt,token)
    Debug joseHeader


    CkPublicKey::ckDispose(pubKey)
    CkJwt::ckDispose(jwt)


    ProcedureReturn
EndProcedure