(PureBasic) JWE using RSAES-PKCS1-v1_5 and AES_128_CBC_HMAC_SHA_256

This example duplicates the example A.2 in RFC 7516 for JSON Web Encryption (JWE).

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

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IncludeFile "CkStringBuilder.pb"
IncludeFile "CkJsonObject.pb"
IncludeFile "CkJwe.pb"
IncludeFile "CkPrivateKey.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.

    success.i
    plaintext.s = "Live long and prosper."

    ; First build the JWE Protected Header.
    ; We want to build this: {"alg":"RSA1_5","enc":"A128CBC-HS256"}
    jweProtHdr.i = CkJsonObject::ckCreate()
    If jweProtHdr.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkJsonObject::ckAppendString(jweProtHdr,"alg","RSA1_5")
    CkJsonObject::ckAppendString(jweProtHdr,"enc","A128CBC-HS256")
    Debug "JWE Protected Header: " + CkJsonObject::ckEmit(jweProtHdr)
    Debug "--"

    ; The specific RSA key used in the A.2 example is the following JWK:
    sbJwk.i = CkStringBuilder::ckCreate()
    If sbJwk.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkStringBuilder::ckAppend(sbJwk,"{" + Chr(34) + "kty" + Chr(34) + ":" + Chr(34) + "RSA" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwk,Chr(34) + "n" + Chr(34) + ":" + Chr(34) + "sXchDaQebHnPiGvyDOAT4saGEUetSyo9MKLOoWFsueri23bOdgWp4Dy1Wl")
    CkStringBuilder::ckAppend(sbJwk,"UzewbgBHod5pcM9H95GQRV3JDXboIRROSBigeC5yjU1hGzHHyXss8UDpre")
    CkStringBuilder::ckAppend(sbJwk,"cbAYxknTcQkhslANGRUZmdTOQ5qTRsLAt6BTYuyvVRdhS8exSZEy_c4gs_")
    CkStringBuilder::ckAppend(sbJwk,"7svlJJQ4H9_NxsiIoLwAEk7-Q3UXERGYw_75IDrGA84-lA_-Ct4eTlXHBI")
    CkStringBuilder::ckAppend(sbJwk,"Y2EaV7t7LjJaynVJCpkv4LKjTTAumiGUIuQhrNhZLuF_RJLqHpM2kgWFLU")
    CkStringBuilder::ckAppend(sbJwk,"7-VTdL1VbC2tejvcI2BlMkEpk1BzBZI0KQB0GaDWFLN-aEAw3vRw" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwk,Chr(34) + "e" + Chr(34) + ":" + Chr(34) + "AQAB" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwk,Chr(34) + "d" + Chr(34) + ":" + Chr(34) + "VFCWOqXr8nvZNyaaJLXdnNPXZKRaWCjkU5Q2egQQpTBMwhprMzWzpR8Sxq")
    CkStringBuilder::ckAppend(sbJwk,"1OPThh_J6MUD8Z35wky9b8eEO0pwNS8xlh1lOFRRBoNqDIKVOku0aZb-ry")
    CkStringBuilder::ckAppend(sbJwk,"nq8cxjDTLZQ6Fz7jSjR1Klop-YKaUHc9GsEofQqYruPhzSA-QgajZGPbE_")
    CkStringBuilder::ckAppend(sbJwk,"0ZaVDJHfyd7UUBUKunFMScbflYAAOYJqVIVwaYR5zWEEceUjNnTNo_CVSj")
    CkStringBuilder::ckAppend(sbJwk,"-VvXLO5VZfCUAVLgW4dpf1SrtZjSt34YLsRarSb127reG_DUwg9Ch-Kyvj")
    CkStringBuilder::ckAppend(sbJwk,"T1SkHgUWRVGcyly7uvVGRSDwsXypdrNinPA4jlhoNdizK2zF2CWQ" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwk,Chr(34) + "p" + Chr(34) + ":" + Chr(34) + "9gY2w6I6S6L0juEKsbeDAwpd9WMfgqFoeA9vEyEUuk4kLwBKcoe1x4HG68")
    CkStringBuilder::ckAppend(sbJwk,"ik918hdDSE9vDQSccA3xXHOAFOPJ8R9EeIAbTi1VwBYnbTp87X-xcPWlEP")
    CkStringBuilder::ckAppend(sbJwk,"krdoUKW60tgs1aNd_Nnc9LEVVPMS390zbFxt8TN_biaBgelNgbC95sM" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwk,Chr(34) + "q" + Chr(34) + ":" + Chr(34) + "uKlCKvKv_ZJMVcdIs5vVSU_6cPtYI1ljWytExV_skstvRSNi9r66jdd9-y")
    CkStringBuilder::ckAppend(sbJwk,"BhVfuG4shsp2j7rGnIio901RBeHo6TPKWVVykPu1iYhQXw1jIABfw-MVsN")
    CkStringBuilder::ckAppend(sbJwk,"-3bQ76WLdt2SDxsHs7q7zPyUyHXmps7ycZ5c72wGkUwNOjYelmkiNS0" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwk,Chr(34) + "dp" + Chr(34) + ":" + Chr(34) + "w0kZbV63cVRvVX6yk3C8cMxo2qCM4Y8nsq1lmMSYhG4EcL6FWbX5h9yuv")
    CkStringBuilder::ckAppend(sbJwk,"ngs4iLEFk6eALoUS4vIWEwcL4txw9LsWH_zKI-hwoReoP77cOdSL4AVcra")
    CkStringBuilder::ckAppend(sbJwk,"Hawlkpyd2TWjE5evgbhWtOxnZee3cXJBkAi64Ik6jZxbvk-RR3pEhnCs" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwk,Chr(34) + "dq" + Chr(34) + ":" + Chr(34) + "o_8V14SezckO6CNLKs_btPdFiO9_kC1DsuUTd2LAfIIVeMZ7jn1Gus_Ff")
    CkStringBuilder::ckAppend(sbJwk,"7B7IVx3p5KuBGOVF8L-qifLb6nQnLysgHDh132NDioZkhH7mI7hPG-PYE_")
    CkStringBuilder::ckAppend(sbJwk,"odApKdnqECHWw0J-F0JWnUd6D2B_1TvF9mXA2Qx-iGYn8OVV1Bsmp6qU" + Chr(34) + ",")
    CkStringBuilder::ckAppend(sbJwk,Chr(34) + "qi" + Chr(34) + ":" + Chr(34) + "eNho5yRBEBxhGBtQRww9QirZsB66TrfFReG_CcteI1aCneT0ELGhYlRlC")
    CkStringBuilder::ckAppend(sbJwk,"tUkTRclIfuEPmNsNDPbLoLqqCVznFbvdB7x-Tl-m0l_eFTj2KiqwGqE9PZ")
    CkStringBuilder::ckAppend(sbJwk,"B9nNTwMVvH3VRRSLWACvPnSiwP8N5Usy-WRXS-V7TbpxIhvepTfE0NNo" + Chr(34))
    CkStringBuilder::ckAppend(sbJwk,"}")

    ; Load this JWK into a Chilkat private key object.
    rsaPrivKey.i = CkPrivateKey::ckCreate()
    If rsaPrivKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPrivateKey::ckLoadJwk(rsaPrivKey,CkStringBuilder::ckGetAsString(sbJwk))
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(rsaPrivKey)
        CkJsonObject::ckDispose(jweProtHdr)
        CkStringBuilder::ckDispose(sbJwk)
        CkPrivateKey::ckDispose(rsaPrivKey)
        ProcedureReturn
    EndIf

    ; The public key is used to encrypt (i.e. create the JWE), 
    ; and the private key is used to decrypt.
    ; The RSA public key is simply a subset of the private key.  The RSA public key
    ; is composed of the "n" and "e" members shown above.  These are also known as the
    ; modulus and exponent.
    ; We can simply get the public key object from the private key object
    rsaPubKey.i = CkPrivateKey::ckGetPublicKey(rsaPrivKey)

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

    CkJwe::ckSetProtectedHeader(jwe,jweProtHdr)
    CkJwe::ckSetPublicKey(jwe,0,rsaPubKey)
    CkPublicKey::ckDispose(rsaPubKey)

    strJwe.s = CkJwe::ckEncrypt(jwe,plaintext,"utf-8")
    If CkJwe::ckLastMethodSuccess(jwe) <> 1
        Debug CkJwe::ckLastErrorText(jwe)
        CkJsonObject::ckDispose(jweProtHdr)
        CkStringBuilder::ckDispose(sbJwk)
        CkPrivateKey::ckDispose(rsaPrivKey)
        CkJwe::ckDispose(jwe)
        ProcedureReturn
    EndIf

    ; Show the JWE we just created:
    Debug strJwe

    ; Note: The RSA PKCS1_V1_5 padding uses random value, and the results
    ; will be different each time.  However, each result should be successfully
    ; decrypting if using the correct RSA private key.

    ; Let's decrypt the JWE that was just produced.
    ; Do the following to decrypt a JWE:
    ; 1) Load the JWE.
    ; 2) Set the private key for decryption.
    ; 3) Decrypt.
    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)
        CkJsonObject::ckDispose(jweProtHdr)
        CkStringBuilder::ckDispose(sbJwk)
        CkPrivateKey::ckDispose(rsaPrivKey)
        CkJwe::ckDispose(jwe)
        CkJwe::ckDispose(jwe2)
        ProcedureReturn
    EndIf

    ; Provide the RSA private key for decryption.
    ; (The JWE was encrypted for a single recipient at index 0.)
    CkJwe::ckSetPrivateKey(jwe2,0,rsaPrivKey)

    ; Decrypt.
    originalPlaintext.s = CkJwe::ckDecrypt(jwe2,0,"utf-8")
    If CkJwe::ckLastMethodSuccess(jwe2) <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJsonObject::ckDispose(jweProtHdr)
        CkStringBuilder::ckDispose(sbJwk)
        CkPrivateKey::ckDispose(rsaPrivKey)
        CkJwe::ckDispose(jwe)
        CkJwe::ckDispose(jwe2)
        ProcedureReturn
    EndIf

    Debug "original text: "
    Debug originalPlaintext

    ; ---------------------------------------------------------------------------------
    ; It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.2.7
    ; because it was produced using the same RSA key.

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

    CkStringBuilder::ckAppend(sbJwe,"eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.")
    CkStringBuilder::ckAppend(sbJwe,"UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm")
    CkStringBuilder::ckAppend(sbJwe,"1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc")
    CkStringBuilder::ckAppend(sbJwe,"HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF")
    CkStringBuilder::ckAppend(sbJwe,"NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8")
    CkStringBuilder::ckAppend(sbJwe,"rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv")
    CkStringBuilder::ckAppend(sbJwe,"-B3oWh2TbqmScqXMR4gp_A.")
    CkStringBuilder::ckAppend(sbJwe,"AxY8DCtDaGlsbGljb3RoZQ.")
    CkStringBuilder::ckAppend(sbJwe,"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.")
    CkStringBuilder::ckAppend(sbJwe,"9hH0vgRfYgPnAHOd8stkvw")

    success = CkJwe::ckLoadJweSb(jwe2,sbJwe)
    If success <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJsonObject::ckDispose(jweProtHdr)
        CkStringBuilder::ckDispose(sbJwk)
        CkPrivateKey::ckDispose(rsaPrivKey)
        CkJwe::ckDispose(jwe)
        CkJwe::ckDispose(jwe2)
        CkStringBuilder::ckDispose(sbJwe)
        ProcedureReturn
    EndIf

    ; Provide the RSA private key for decryption.
    CkJwe::ckSetPrivateKey(jwe2,0,rsaPrivKey)

    ; Decrypt.
    originalPlaintext = CkJwe::ckDecrypt(jwe2,0,"utf-8")
    If CkJwe::ckLastMethodSuccess(jwe2) <> 1
        Debug CkJwe::ckLastErrorText(jwe2)
        CkJsonObject::ckDispose(jweProtHdr)
        CkStringBuilder::ckDispose(sbJwk)
        CkPrivateKey::ckDispose(rsaPrivKey)
        CkJwe::ckDispose(jwe)
        CkJwe::ckDispose(jwe2)
        CkStringBuilder::ckDispose(sbJwe)
        ProcedureReturn
    EndIf

    Debug originalPlaintext


    CkJsonObject::ckDispose(jweProtHdr)
    CkStringBuilder::ckDispose(sbJwk)
    CkPrivateKey::ckDispose(rsaPrivKey)
    CkJwe::ckDispose(jwe)
    CkJwe::ckDispose(jwe2)
    CkStringBuilder::ckDispose(sbJwe)


    ProcedureReturn
EndProcedure