(PureBasic) JWE Using Flattened JWE JSON Serialization

This example duplicates the example A.5 in RFC 7516 for JSON Web Encryption (JWE).

This example demonstrates using the flattened JWE JSON Serialization syntax. This example demonstrates the capability for encrypting the plaintext to a single recipient in a flattened JSON structure.

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

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IncludeFile "CkStringBuilder.pb"
IncludeFile "CkJwe.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
    plaintext.s = "Live long and prosper."

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

    ; First build the JWE Protected Header: {"enc":"A128CBC-HS256"}
    jweProtHdr.i = CkJsonObject::ckCreate()
    If jweProtHdr.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::ckAppendString(jweProtHdr,"enc","A128CBC-HS256")
    CkJwe::ckSetProtectedHeader(jwe,jweProtHdr)

    ; We have a single recipient that uses AES Key Wrap to encrypt the CEK.
    ; 
    ;      {"alg":"A128KW","kid":"7"}

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

    CkJsonObject::ckAppendString(jweRecipientHdr,"alg","A128KW")
    CkJsonObject::ckAppendString(jweRecipientHdr,"kid","7")
    recipientIndex.i = 0
    CkJwe::ckSetRecipientHeader(jwe,recipientIndex,jweRecipientHdr)

    ; Set the Shared Unprotected Header:  {"jku":"https://server.example.com/keys.jwks"}
    jweUnprotHdr.i = CkJsonObject::ckCreate()
    If jweUnprotHdr.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::ckAppendString(jweUnprotHdr,"jku","https://server.example.com/keys.jwks")
    CkJwe::ckSetUnprotectedHeader(jwe,jweUnprotHdr)

    ; Set the AES key wrapping key.
    aesWrappingKey.s = "GawgguFyGrWKav7AX4VKUg"
    recipientIndex = 0
    CkJwe::ckSetWrappingKey(jwe,recipientIndex,aesWrappingKey,"base64url")

    ; OK.. everything has been specified.
    ; Now encrypt.  
    ; Indicate that we prefer the flattened JSON serialization.
    CkJwe::setCkPreferFlattened(jwe, 1)
    strJwe.s = CkJwe::ckEncrypt(jwe,plaintext,"utf-8")
    If CkJwe::ckLastMethodSuccess(jwe) <> 1
        Debug CkJwe::ckLastErrorText(jwe)
        CkJwe::ckDispose(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        CkJsonObject::ckDispose(jweRecipientHdr)
        CkJsonObject::ckDispose(jweUnprotHdr)
        ProcedureReturn
    EndIf

    ; The JWE is produced in the most compact form possible (a single line).
    ; Let's load it into a JSON object and examine in a non-compact pretty-printed format:
    jsonTemp.i = CkJsonObject::ckCreate()
    If jsonTemp.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::ckLoad(jsonTemp,strJwe)
    CkJsonObject::setCkEmitCompact(jsonTemp, 0)
    Debug CkJsonObject::ckEmit(jsonTemp)

    ; The JWE looks like this:
    ; (Note: Because of random values used in the encryption process, your encrypted results will be different.)

    ; 	{ 
    ; 	  "protected": "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
    ; 	  "unprotected": { 
    ; 	    "jku": "https://server.example.com/keys.jwks"
    ; 	  },
    ; 	  "header": { 
    ; 	    "alg": "A128KW",
    ; 	    "kid": "7"
    ; 	  },
    ; 	  "encrypted_key": "FW7z9VxOvnF2ClicvUT4HTeqcdyh90C6qytfEFJsOb77FOwTfYrc3w",
    ; 	  "iv": "O6Ly5-eML3zTs-_fNX3D5Q",
    ; 	  "ciphertext": "Q8NLmeac9JhLh0CQPuG_7D9wVDb55eToCh0g5-FQ4M0",
    ; 	  "tag": "slzlo6-J9C7wSDF4dh_kBg"
    ; 	} 

    ; Now decrypt......................................

    ; First, load the JWE..
    jwe2.i = CkJwe::ckCreate()
    If jwe2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkJwe::ckLoadJwe(jwe2,strJwe)
    If success <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJwe::ckDispose(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        CkJsonObject::ckDispose(jweRecipientHdr)
        CkJsonObject::ckDispose(jweUnprotHdr)
        CkJsonObject::ckDispose(jsonTemp)
        CkJwe::ckDispose(jwe2)
        ProcedureReturn
    EndIf

    ; Set the AES wrap key..
    recipientIndex = 0
    CkJwe::ckSetWrappingKey(jwe2,recipientIndex,aesWrappingKey,"base64url")

    ; Decrypt
    originalPlaintext.s = CkJwe::ckDecrypt(jwe2,recipientIndex,"utf-8")
    If CkJwe::ckLastMethodSuccess(jwe2) <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJwe::ckDispose(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        CkJsonObject::ckDispose(jweRecipientHdr)
        CkJsonObject::ckDispose(jweUnprotHdr)
        CkJsonObject::ckDispose(jsonTemp)
        CkJwe::ckDispose(jwe2)
        ProcedureReturn
    EndIf

    Debug "original text decrypted with AES key wrap key: "
    Debug originalPlaintext

    ; ---------------------------------------------------------------------------------
    ; It should also be possible to decrypt the flattened JWE as shown in RFC 7516, Appendix A.5
    ; because it was produced using the same key.

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

    CkStringBuilder::ckAppend(sbJwe,"{")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "protected" + Chr(34) + ":")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "unprotected" + Chr(34) + ":")
    CkStringBuilder::ckAppend(sbJwe,"{" + Chr(34) + "jku" + Chr(34) + ":" + Chr(34) + "https://server.example.com/keys.jwks" + Chr(34) + "},")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "header" + Chr(34) + ":")
    CkStringBuilder::ckAppend(sbJwe,"{" + Chr(34) + "alg" + Chr(34) + ":" + Chr(34) + "A128KW" + Chr(34) + "," + Chr(34) + "kid" + Chr(34) + ":" + Chr(34) + "7" + Chr(34) + "},")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "encrypted_key" + Chr(34) + ":")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "iv" + Chr(34) + ":")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "AxY8DCtDaGlsbGljb3RoZQ" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "ciphertext" + Chr(34) + ":")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "tag" + Chr(34) + ":")
    CkStringBuilder::ckAppend(sbJwe,Chr(34) + "Mz-VPPyU4RlcuYv1IwIvzw" + Chr(34))
    CkStringBuilder::ckAppend(sbJwe,"}")

    success = CkJwe::ckLoadJweSb(jwe2,sbJwe)
    If success <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJwe::ckDispose(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        CkJsonObject::ckDispose(jweRecipientHdr)
        CkJsonObject::ckDispose(jweUnprotHdr)
        CkJsonObject::ckDispose(jsonTemp)
        CkJwe::ckDispose(jwe2)
        CkStringBuilder::ckDispose(sbJwe)
        ProcedureReturn
    EndIf

    recipientIndex = 0
    CkJwe::ckSetWrappingKey(jwe2,recipientIndex,aesWrappingKey,"base64url")

    originalPlaintext = CkJwe::ckDecrypt(jwe2,recipientIndex,"utf-8")
    If CkJwe::ckLastMethodSuccess(jwe2) <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJwe::ckDispose(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        CkJsonObject::ckDispose(jweRecipientHdr)
        CkJsonObject::ckDispose(jweUnprotHdr)
        CkJsonObject::ckDispose(jsonTemp)
        CkJwe::ckDispose(jwe2)
        CkStringBuilder::ckDispose(sbJwe)
        ProcedureReturn
    EndIf

    Debug "original text decrypted from published flattened JWE: "
    Debug originalPlaintext

    ; The output:

    ; original text decrypted with AES key wrap key: 
    ; Live long and prosper.
    ; original text decrypted from published flattened JWE: 
    ; Live long and prosper.


    CkJwe::ckDispose(jwe)
    CkJsonObject::ckDispose(jweProtHdr)
    CkJsonObject::ckDispose(jweRecipientHdr)
    CkJsonObject::ckDispose(jweUnprotHdr)
    CkJsonObject::ckDispose(jsonTemp)
    CkJwe::ckDispose(jwe2)
    CkStringBuilder::ckDispose(sbJwe)


    ProcedureReturn
EndProcedure