(PureBasic) Validate JWS Using RSASSA-PKCS1-v1_5 SHA-256

Validates a JSON Web Signature (JWS) that uses RSASSA-PKCS1-v1_5 SHA-256.

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

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkJws.pb"
IncludeFile "CkStringBuilder.pb"
IncludeFile "CkJsonObject.pb"
IncludeFile "CkPublicKey.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.

    ; This example takes a JSON signature in compact serialization format,
    ; and uses an RSA public key to validate and recover the protected header and payload.

    ; We only need a public key for signature validation.  This is the RSA public key
    ; that is used:

    ;      {"kty":"RSA", 
    ;       "n":"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx
    ;            HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs
    ;            D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH
    ;            SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV
    ;            MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8
    ;            NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ", 
    ;       "e":"AQAB"
    ;      }

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

    CkStringBuilder::ckAppend(sbPubKey,"{" + Chr(34) + "kty" + Chr(34) + ":" + Chr(34) + "RSA" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbPubKey,Chr(34) + "n" + Chr(34) + ":" + Chr(34) + "ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx")
    CkStringBuilder::ckAppend(sbPubKey,"HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs")
    CkStringBuilder::ckAppend(sbPubKey,"D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH")
    CkStringBuilder::ckAppend(sbPubKey,"SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV")
    CkStringBuilder::ckAppend(sbPubKey,"MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8")
    CkStringBuilder::ckAppend(sbPubKey,"NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbPubKey,Chr(34) + "e" + Chr(34) + ":" + Chr(34) + "AQAB" + Chr(34))
    CkStringBuilder::ckAppend(sbPubKey,"}")

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

    success.i = CkPublicKey::ckLoadFromString(pubKey,CkStringBuilder::ckGetAsString(sbPubKey))
    If success <> 1
        Debug CkPublicKey::ckLastErrorText(pubKey)
        CkStringBuilder::ckDispose(sbPubKey)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf

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

    ; Set the RSA public key:
    signatureIndex.i = 0
    CkJws::ckSetPublicKey(jws,signatureIndex,pubKey)

    ; Load the JWS.
    sbJws.i = CkStringBuilder::ckCreate()
    If sbJws.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkStringBuilder::ckAppend(sbJws,"eyJhbGciOiJSUzI1NiJ9")
    CkStringBuilder::ckAppend(sbJws,".")
    CkStringBuilder::ckAppend(sbJws,"eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt")
    CkStringBuilder::ckAppend(sbJws,"cGxlLmNvbS9pc19yb290Ijp0cnVlfQ")
    CkStringBuilder::ckAppend(sbJws,".")
    CkStringBuilder::ckAppend(sbJws,"cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7")
    CkStringBuilder::ckAppend(sbJws,"AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4")
    CkStringBuilder::ckAppend(sbJws,"BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K")
    CkStringBuilder::ckAppend(sbJws,"0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv")
    CkStringBuilder::ckAppend(sbJws,"hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB")
    CkStringBuilder::ckAppend(sbJws,"p0igcN_IoypGlUPQGe77Rw")

    success = CkJws::ckLoadJwsSb(jws,sbJws)
    If success <> 1
        Debug CkJws::ckLastErrorText(jws)
        CkStringBuilder::ckDispose(sbPubKey)
        CkPublicKey::ckDispose(pubKey)
        CkJws::ckDispose(jws)
        CkStringBuilder::ckDispose(sbJws)
        ProcedureReturn
    EndIf

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

    If v = 0
        Debug "Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both."
        CkStringBuilder::ckDispose(sbPubKey)
        CkPublicKey::ckDispose(pubKey)
        CkJws::ckDispose(jws)
        CkStringBuilder::ckDispose(sbJws)
        ProcedureReturn
    EndIf

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

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

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

    CkJsonObject::setCkEmitCompact(joseHeader, 0)

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

    ; Output:

    ; 	Signature validated.
    ; 	--
    ; 	Recovered content:
    ; 	{"iss":"joe", 
    ; 	 "exp":1300819380,
    ; 	 "http://example.com/is_root":true}
    ; 	--
    ; 	Protected (JOSE) header:
    ; 	{ 
    ; 	  "alg": "RS256"
    ; 	}


    CkStringBuilder::ckDispose(sbPubKey)
    CkPublicKey::ckDispose(pubKey)
    CkJws::ckDispose(jws)
    CkStringBuilder::ckDispose(sbJws)


    ProcedureReturn
EndProcedure