(PureBasic) JWS Using HMAC SHA-256

Creates a JSON Web Signatures (JWS) using HMAC SHA-256.

Note: This example requires Chilkat v9.5.0.66 or greater.

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IncludeFile "CkJws.pb"
IncludeFile "CkJsonObject.pb"

Procedure ChilkatExample()

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

    ; Note: This example requires Chilkat v9.5.0.66 or greater.

    success.i

    ; First create the JWS Protected Header
    jwsProtHdr.i = CkJsonObject::ckCreate()
    If jwsProtHdr.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::ckAppendString(jwsProtHdr,"typ","JWT")
    CkJsonObject::ckAppendString(jwsProtHdr,"alg","HS256")
    Debug "JWS Protected Header: " + CkJsonObject::ckEmit(jwsProtHdr)

    ; Output:
    ; JWS Protected Header: {"typ":"JWT","alg":"HS256"}

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

    ; Set the HMAC key:
    hmacKey.s = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
    signatureIndex.i = 0
    CkJws::ckSetMacKey(jws,signatureIndex,hmacKey,"base64url")

    ; Set the protected header:
    CkJws::ckSetProtectedHeader(jws,signatureIndex,jwsProtHdr)

    ; Set the payload.
    bIncludeBom.i = 0
    payloadStr.s = "In our village, folks say God crumbles up the old moon into stars."
    CkJws::ckSetPayload(jws,payloadStr,"utf-8",bIncludeBom)

    ; Create the JWS
    ; By default, the compact serialization is used.
    jwsCompact.s = CkJws::ckCreateJws(jws)
    If CkJws::ckLastMethodSuccess(jws) <> 1
        Debug CkJws::ckLastErrorText(jws)
        CkJsonObject::ckDispose(jwsProtHdr)
        CkJws::ckDispose(jws)
        ProcedureReturn
    EndIf

    Debug "JWS: " + jwsCompact

    ; sample output:
    ; JWS: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.bsYsi8HJ0N6OqGI1hKQ9QQRNPxxA5qMpcHLtOvXatk8

    ; Now load the JWS, validate, and recover the original text.
    jws2.i = CkJws::ckCreate()
    If jws2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Load the JWS.
    success = CkJws::ckLoadJws(jws2,jwsCompact)

    ; Set the MAC key used for validation.
    signatureIndex = 0
    CkJws::ckSetMacKey(jws2,signatureIndex,hmacKey,"base64url")

    ; Validate the 1st (and only) signature at index 0..
    v.i = CkJws::ckValidate(jws2,signatureIndex)
    If v < 0
        ; Perhaps Chilkat was not unlocked or the trial expired..
        Debug "Method call failed for some other reason."
        Debug CkJws::ckLastErrorText(jws2)
        CkJsonObject::ckDispose(jwsProtHdr)
        CkJws::ckDispose(jws)
        CkJws::ckDispose(jws2)
        ProcedureReturn
    EndIf

    If v = 0
        Debug "Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both."
        CkJsonObject::ckDispose(jwsProtHdr)
        CkJws::ckDispose(jws)
        CkJws::ckDispose(jws2)
        ProcedureReturn
    EndIf

    ; If we get here, the signature was validated..
    Debug "Signature validated."

    ; Recover the original content:
    Debug CkJws::ckGetPayload(jws2,"utf-8")

    ; Examine the protected header:
    joseHeader.i = CkJws::ckGetProtectedHeader(jws2,signatureIndex)
    If CkJws::ckLastMethodSuccess(jws2) <> 1
        Debug "No protected header found at the given index."
        CkJsonObject::ckDispose(jwsProtHdr)
        CkJws::ckDispose(jws)
        CkJws::ckDispose(jws2)
        ProcedureReturn
    EndIf

    CkJsonObject::setCkEmitCompact(joseHeader, 0)

    Debug "Protected (JOSE) header:"
    Debug CkJsonObject::ckEmit(joseHeader)
    CkJsonObject::ckDispose(joseHeader)

    ; Output:

    ; 	Signature validated.
    ; 	In our village, folks say God crumbles up the old moon into stars.
    ; 	Protected (JOSE) header:
    ; 	{ 
    ; 	  "typ": "JWT",
    ; 	  "alg": "HS256"
    ; 	} 


    CkJsonObject::ckDispose(jwsProtHdr)
    CkJws::ckDispose(jws)
    CkJws::ckDispose(jws2)


    ProcedureReturn
EndProcedure