(Tcl) 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.

Chilkat Tcl Extension Downloads Chilkat Tcl Extension Downloads

load ./chilkat.dll

# 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.

set plaintext "Live long and prosper."

# First build the JWE Protected Header.
# We want to build this: {"alg":"RSA1_5","enc":"A128CBC-HS256"}
set jweProtHdr [new_CkJsonObject]

CkJsonObject_AppendString $jweProtHdr "alg" "RSA1_5"
CkJsonObject_AppendString $jweProtHdr "enc" "A128CBC-HS256"
puts "JWE Protected Header: [CkJsonObject_emit $jweProtHdr]"
puts "--"

# The specific RSA key used in the A.2 example is the following JWK:
set sbJwk [new_CkStringBuilder]

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

# Load this JWK into a Chilkat private key object.
set rsaPrivKey [new_CkPrivateKey]

set success [CkPrivateKey_LoadJwk $rsaPrivKey [CkStringBuilder_getAsString $sbJwk]]
if {$success != 1} then {
    puts [CkPrivateKey_lastErrorText $rsaPrivKey]
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $rsaPrivKey
    exit
}

# 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 is a CkPublicKey
set rsaPubKey [CkPrivateKey_GetPublicKey $rsaPrivKey]

# Create the JWE...
set jwe [new_CkJwe]

CkJwe_SetProtectedHeader $jwe $jweProtHdr
CkJwe_SetPublicKey $jwe 0 $rsaPubKey
delete_CkPublicKey $rsaPubKey

set strJwe [CkJwe_encrypt $jwe $plaintext "utf-8"]
if {[CkJwe_get_LastMethodSuccess $jwe] != 1} then {
    puts [CkJwe_lastErrorText $jwe]
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $rsaPrivKey
    delete_CkJwe $jwe
    exit
}

# Show the JWE we just created:
puts "$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.
set jwe2 [new_CkJwe]

set success [CkJwe_LoadJwe $jwe2 $strJwe]
if {$success != 1} then {
    puts [CkJwe_lastErrorText $jwe2]
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $rsaPrivKey
    delete_CkJwe $jwe
    delete_CkJwe $jwe2
    exit
}

# Provide the RSA private key for decryption.
# (The JWE was encrypted for a single recipient at index 0.)
CkJwe_SetPrivateKey $jwe2 0 $rsaPrivKey

# Decrypt.
set originalPlaintext [CkJwe_decrypt $jwe2 0 "utf-8"]
if {[CkJwe_get_LastMethodSuccess $jwe2] != 1} then {
    puts [CkJwe_lastErrorText $jwe2]
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $rsaPrivKey
    delete_CkJwe $jwe
    delete_CkJwe $jwe2
    exit
}

puts "original text: "
puts "$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.

set sbJwe [new_CkStringBuilder]

CkStringBuilder_Append $sbJwe "eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0."
CkStringBuilder_Append $sbJwe "UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm"
CkStringBuilder_Append $sbJwe "1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc"
CkStringBuilder_Append $sbJwe "HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF"
CkStringBuilder_Append $sbJwe "NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8"
CkStringBuilder_Append $sbJwe "rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv"
CkStringBuilder_Append $sbJwe "-B3oWh2TbqmScqXMR4gp_A."
CkStringBuilder_Append $sbJwe "AxY8DCtDaGlsbGljb3RoZQ."
CkStringBuilder_Append $sbJwe "KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY."
CkStringBuilder_Append $sbJwe "9hH0vgRfYgPnAHOd8stkvw"

set success [CkJwe_LoadJweSb $jwe2 $sbJwe]
if {$success != 1} then {
    puts [CkJwe_lastErrorText $jwe2]
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $rsaPrivKey
    delete_CkJwe $jwe
    delete_CkJwe $jwe2
    delete_CkStringBuilder $sbJwe
    exit
}

# Provide the RSA private key for decryption.
CkJwe_SetPrivateKey $jwe2 0 $rsaPrivKey

# Decrypt.
set originalPlaintext [CkJwe_decrypt $jwe2 0 "utf-8"]
if {[CkJwe_get_LastMethodSuccess $jwe2] != 1} then {
    puts [CkJwe_lastErrorText $jwe2]
    delete_CkJsonObject $jweProtHdr
    delete_CkStringBuilder $sbJwk
    delete_CkPrivateKey $rsaPrivKey
    delete_CkJwe $jwe
    delete_CkJwe $jwe2
    delete_CkStringBuilder $sbJwe
    exit
}

puts "$originalPlaintext"

delete_CkJsonObject $jweProtHdr
delete_CkStringBuilder $sbJwk
delete_CkPrivateKey $rsaPrivKey
delete_CkJwe $jwe
delete_CkJwe $jwe2
delete_CkStringBuilder $sbJwe