(Visual FoxPro) Validate a JWS Using ECDSA P-256 SHA-256

Validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loSbPubKey
LOCAL loPubKey
LOCAL lnSuccess
LOCAL loJws
LOCAL lnSignatureIndex
LOCAL loSbJws
LOCAL v
LOCAL loJoseHeader

* 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 ECDSA public key to validate and recover the protected header and payload.

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

*      {"kty":"EC", 
*       "crv":"P-256", 
*       "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU", 
*       "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" 
*      } 

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbPubKey = CreateObject('Chilkat.StringBuilder')
loSbPubKey.Append('{"kty":"EC",')
loSbPubKey.Append('"crv":"P-256",')
loSbPubKey.Append('"x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",')
loSbPubKey.Append('"y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0"')
loSbPubKey.Append("}")

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.PublicKey')
loPubKey = CreateObject('Chilkat.PublicKey')
lnSuccess = loPubKey.LoadFromString(loSbPubKey.GetAsString())
IF (lnSuccess <> 1) THEN
    ? loPubKey.LastErrorText
    RELEASE loSbPubKey
    RELEASE loPubKey
    CANCEL
ENDIF

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Jws')
loJws = CreateObject('Chilkat.Jws')

* Set the ECC public key:
lnSignatureIndex = 0
loJws.SetPublicKey(lnSignatureIndex,loPubKey)

* Load the JWS.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbJws = CreateObject('Chilkat.StringBuilder')
loSbJws.Append("eyJhbGciOiJFUzI1NiJ9")
loSbJws.Append(".")
loSbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt")
loSbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ")
loSbJws.Append(".")
loSbJws.Append("DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA")
loSbJws.Append("pmWQxfKTUJqPP3-Kg6NU1Q")

lnSuccess = loJws.LoadJwsSb(loSbJws)
IF (lnSuccess <> 1) THEN
    ? loJws.LastErrorText
    RELEASE loSbPubKey
    RELEASE loPubKey
    RELEASE loJws
    RELEASE loSbJws
    CANCEL
ENDIF

* Validate the 1st (and only) signature at index 0..
v = loJws.Validate(lnSignatureIndex)
IF (v < 0) THEN
    * Perhaps Chilkat was not unlocked or the trial expired..
    ? "Method call failed for some other reason."
    ? loJws.LastErrorText
    RELEASE loSbPubKey
    RELEASE loPubKey
    RELEASE loJws
    RELEASE loSbJws
    CANCEL
ENDIF

IF (v = 0) THEN
    ? "Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both."
    RELEASE loSbPubKey
    RELEASE loPubKey
    RELEASE loJws
    RELEASE loSbJws
    CANCEL
ENDIF

* If we get here, the signature was validated..
? "Signature validated."
? "--"

* Recover the original content:
? "Recovered content:"
? loJws.GetPayload("utf-8")
? "--"

* Examine the protected header:
loJoseHeader = loJws.GetProtectedHeader(lnSignatureIndex)
IF (loJws.LastMethodSuccess <> 1) THEN
    ? "No protected header found at the given index."
    RELEASE loSbPubKey
    RELEASE loPubKey
    RELEASE loJws
    RELEASE loSbJws
    CANCEL
ENDIF

loJoseHeader.EmitCompact = 0

? "Protected (JOSE) header:"
? loJoseHeader.Emit()
RELEASE loJoseHeader

* Output:

* 	Signature validated.
* 	--
* 	Recovered content:
* 	{"iss":"joe",
* 	 "exp":1300819380,
* 	 "http://example.com/is_root":true}
* 	--
* 	Protected (JOSE) header:
* 	{ 
* 	  "alg": "ES256"
* 	}

RELEASE loSbPubKey
RELEASE loPubKey
RELEASE loJws
RELEASE loSbJws