(Lianja) JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256

This example duplicates the example A.3 in RFC 7516 for JSON Web Encryption (JWE).

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.

lcPlaintext = "Live long and prosper."

loJwe = createobject("CkJwe")

// First build the JWE Protected Header: {"alg":"A128KW","enc":"A128CBC-HS256"}
loJweProtHdr = createobject("CkJsonObject")
loJweProtHdr.AppendString("alg","A128KW")
loJweProtHdr.AppendString("enc","A128CBC-HS256")
loJwe.SetProtectedHeader(loJweProtHdr)

? "JWE Protected Header: " + loJweProtHdr.Emit()
? "--"

// The example A.3 in RFC 7516 uses the following 128-bit AES key,
// specified in JWK (JSON Web Key) format:
//      {"kty":"oct",
//       "k":"GawgguFyGrWKav7AX4VKUg"
//      }
// This is just a way of saying: The key type ("kty") is 
// a bunch of octets ("k") in base64url encoding.
// We can simply set the AES wrapping key like this:
lcAesWrappingKey = "GawgguFyGrWKav7AX4VKUg"
loJwe.SetWrappingKey(0,lcAesWrappingKey,"base64url")

// Encrypt and return the JWE:
lcStrJwe = loJwe.Encrypt(lcPlaintext,"utf-8")
if (loJwe.LastMethodSuccess <> .T.) then
    ? loJwe.LastErrorText
    release loJwe
    release loJweProtHdr
    return
endif

// Show the JWE we just created:
? lcStrJwe

// Decrypt the JWE that was just produced.
// 1) Load the JWE.
// 2) Set the AES wrapping key.
// 3) Decrypt.
loJwe2 = createobject("CkJwe")
llSuccess = loJwe2.LoadJwe(lcStrJwe)
if (llSuccess <> .T.) then
    ? loJwe2.LastErrorText
    release loJwe
    release loJweProtHdr
    release loJwe2
    return
endif

// Set the AES wrap key.
loJwe2.SetWrappingKey(0,lcAesWrappingKey,"base64url")

// Decrypt.
lcOriginalPlaintext = loJwe2.Decrypt(0,"utf-8")
if (loJwe2.LastMethodSuccess <> .T.) then
    ? loJwe2.LastErrorText
    release loJwe
    release loJweProtHdr
    release loJwe2
    return
endif

? "original text: "
? lcOriginalPlaintext

// ---------------------------------------------------------------------------------
// It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.3.7
// because it was produced using the same AES Wrap key.

loSbJwe = createobject("CkStringBuilder")
loSbJwe.Append("eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.")
loSbJwe.Append("6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.")
loSbJwe.Append("AxY8DCtDaGlsbGljb3RoZQ.")
loSbJwe.Append("KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.")
loSbJwe.Append("U0m_YmjN04DJvceFICbCVQ")

llSuccess = loJwe2.LoadJweSb(loSbJwe)
if (llSuccess <> .T.) then
    ? loJwe2.LastErrorText
    release loJwe
    release loJweProtHdr
    release loJwe2
    release loSbJwe
    return
endif

loJwe2.SetWrappingKey(0,lcAesWrappingKey,"base64url")

// Decrypt.
lcOriginalPlaintext = loJwe2.Decrypt(0,"utf-8")
if (loJwe2.LastMethodSuccess <> .T.) then
    ? loJwe2.LastErrorText
    release loJwe
    release loJweProtHdr
    release loJwe2
    release loSbJwe
    return
endif

? lcOriginalPlaintext


release loJwe
release loJweProtHdr
release loJwe2
release loSbJwe