(Lianja) 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.

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// 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" 
//      } 

loSbPubKey = createobject("CkStringBuilder")
loSbPubKey.Append('{"kty":"EC",')
loSbPubKey.Append('"crv":"P-256",')
loSbPubKey.Append('"x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",')
loSbPubKey.Append('"y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0"')
loSbPubKey.Append("}")

loPubKey = createobject("CkPublicKey")
llSuccess = loPubKey.LoadFromString(loSbPubKey.GetAsString())
if (llSuccess <> .T.) then
    ? loPubKey.LastErrorText
    release loSbPubKey
    release loPubKey
    return
endif

loJws = createobject("CkJws")

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

// Load the JWS.
loSbJws = createobject("CkStringBuilder")
loSbJws.Append("eyJhbGciOiJFUzI1NiJ9")
loSbJws.Append(".")
loSbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt")
loSbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ")
loSbJws.Append(".")
loSbJws.Append("DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA")
loSbJws.Append("pmWQxfKTUJqPP3-Kg6NU1Q")

llSuccess = loJws.LoadJwsSb(loSbJws)
if (llSuccess <> .T.) then
    ? loJws.LastErrorText
    release loSbPubKey
    release loPubKey
    release loJws
    release loSbJws
    return
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
    return
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
    return
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 <> .T.) then
    ? "No protected header found at the given index."
    release loSbPubKey
    release loPubKey
    release loJws
    release loSbJws
    return
endif

loJoseHeader.EmitCompact = .F.

? "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