(Tcl) JWE using RSAES-OAEP and AES GCM

This example duplicates the example A.1 in RFC 7516 for JSON Web Encryption (JWE).

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

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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 "The true sign of intelligence is not knowledge but imagination."

# ---------------------------------
# A.1.1 JOSE Header
# First build the JWE Protected Header.
# We want to build this: {"alg":"RSA-OAEP","enc":"A256GCM"}
set jweProtHdr [new_CkJsonObject]

CkJsonObject_AppendString $jweProtHdr "alg" "RSA-OAEP"
CkJsonObject_AppendString $jweProtHdr "enc" "A256GCM"
puts "JWE Protected Header: [CkJsonObject_emit $jweProtHdr]"
puts "--"

# ---------------------------------
# A.1.2 Content Encryption Key
# Note: Chilkat automatically generates the random CEK internally.
# The application does not need to explicitly take this step.

# ---------------------------------
# A.1.3.  Key Encryption
# The application should load an RSA private key from any format.
# However, the application does not need to explicitly construct the JWE Encrypted Key.
# Chilkat automatically does it internally.
# The design of the Chilkat JWE API is to allow the application to create the JWE
# after specifying the inputs.  (This is in contrast to forcing the application developer
# to painstakingly go through each step of the JWE construction process.)

# The specific RSA key used in the A.1 example is the following JWK:
set sbJwk [new_CkStringBuilder]

CkStringBuilder_Append $sbJwk "{\"kty\": \"RSA\","
CkStringBuilder_Append $sbJwk "\"n\": \"oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW"
CkStringBuilder_Append $sbJwk "cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S"
CkStringBuilder_Append $sbJwk "psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a"
CkStringBuilder_Append $sbJwk "sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS"
CkStringBuilder_Append $sbJwk "tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj"
CkStringBuilder_Append $sbJwk "YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw\","
CkStringBuilder_Append $sbJwk "\"e\": \"AQAB\","
CkStringBuilder_Append $sbJwk "\"d\": \"kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N"
CkStringBuilder_Append $sbJwk "WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9"
CkStringBuilder_Append $sbJwk "3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk"
CkStringBuilder_Append $sbJwk "qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl"
CkStringBuilder_Append $sbJwk "t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd"
CkStringBuilder_Append $sbJwk "VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ\","
CkStringBuilder_Append $sbJwk "\"p\": \"1r52Xk46c-LsfB5P442p7atdPUrxQSy4mti_tZI3Mgf2EuFVbUoDBvaRQ-"
CkStringBuilder_Append $sbJwk "SWxkbkmoEzL7JXroSBjSrK3YIQgYdMgyAEPTPjXv_hI2_1eTSPVZfzL0lf"
CkStringBuilder_Append $sbJwk "fNn03IXqWF5MDFuoUYE0hzb2vhrlN_rKrbfDIwUbTrjjgieRbwC6Cl0\","
CkStringBuilder_Append $sbJwk "\"q\": \"wLb35x7hmQWZsWJmB_vle87ihgZ19S8lBEROLIsZG4ayZVe9Hi9gDVCOBm"
CkStringBuilder_Append $sbJwk "UDdaDYVTSNx_8Fyw1YYa9XGrGnDew00J28cRUoeBB_jKI1oma0Orv1T9aX"
CkStringBuilder_Append $sbJwk "IWxKwd4gvxFImOWr3QRL9KEBRzk2RatUBnmDZJTIAfwTs0g68UZHvtc\","
CkStringBuilder_Append $sbJwk "\"dp\": \"ZK-YwE7diUh0qR1tR7w8WHtolDx3MZ_OTowiFvgfeQ3SiresXjm9gZ5KL"
CkStringBuilder_Append $sbJwk "hMXvo-uz-KUJWDxS5pFQ_M0evdo1dKiRTjVw_x4NyqyXPM5nULPkcpU827"
CkStringBuilder_Append $sbJwk "rnpZzAJKpdhWAgqrXGKAECQH0Xt4taznjnd_zVpAmZZq60WPMBMfKcuE\","
CkStringBuilder_Append $sbJwk "\"dq\": \"Dq0gfgJ1DdFGXiLvQEZnuKEN0UUmsJBxkjydc3j4ZYdBiMRAy86x0vHCj"
CkStringBuilder_Append $sbJwk "ywcMlYYg4yoC4YZa9hNVcsjqA3FeiL19rk8g6Qn29Tt0cj8qqyFpz9vNDB"
CkStringBuilder_Append $sbJwk "UfCAiJVeESOjJDZPYHdHY8v1b-o-Z2X5tvLx-TCekf7oxyeKDUqKWjis\","
CkStringBuilder_Append $sbJwk "\"qi\": \"VIMpMYbPf47dT1w_zDUXfPimsSegnMOA1zTaX7aGk_8urY6R8-ZW1FxU7"
CkStringBuilder_Append $sbJwk "AlWAyLWybqq6t16VFd7hQd0y6flUK4SlOydB61gwanOsXGOAOv82cHq0E3"
CkStringBuilder_Append $sbJwk "eL4HrtZkUuKvnPrMnsUUFlfUdybVzxyjz9JF_XyaY14ardLSjf4L_FNY\"}"

# 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]

# ---------------------------------
# A.1.4.  Initialization Vector
# Chilkat automatically generates the necessary random IV internally.  
# The application does not need to do this explicitly.

# ---------------------------------
# A.1.5.  Additional Authenticated Data
# The Additional Authenticated Data encryption parameter is
# ASCII(BASE64URL(UTF8(JWE Protected Header))).
# Again, Chilkat automatically takes care of this internally.
# The application does not need to explicitly take this step.

# ---------------------------------
# A.1.6.  Content Encryption
# Again... this step is handled by Chilkat internally.

# ---------------------------------
# A.1.7.  Complete Representation
# The application need only call the Encrypt, EncryptSb, or EncryptBd method
# return the fully assembled JWE.  
# The final representation in the Compact Serialization 
# is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
# BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
# Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
# Authentication Tag).

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
}

# Note: The RSA OAEP algorithm uses random padding bytes internally.
# Therefore, the results will appear different each time -- even if the
# identical plaintext is encrypted with the identical RSA key. 
# (Do not expect the appearance of the results to be the same as what
# is published in the RFC.  However, what is published in the RFC *should*
# be decryptable using the code that follows.)
puts "$strJwe"

# 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.1.7
# because it was produced using the same RSA key.

set sbJwe [new_CkStringBuilder]

CkStringBuilder_Append $sbJwe "eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ."
CkStringBuilder_Append $sbJwe "OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe"
CkStringBuilder_Append $sbJwe "ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb"
CkStringBuilder_Append $sbJwe "Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV"
CkStringBuilder_Append $sbJwe "mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8"
CkStringBuilder_Append $sbJwe "1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi"
CkStringBuilder_Append $sbJwe "6UklfCpIMfIjf7iGdXKHzg."
CkStringBuilder_Append $sbJwe "48V1_ALb6US04U3b."
CkStringBuilder_Append $sbJwe "5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji"
CkStringBuilder_Append $sbJwe "SdiwkIr3ajwQzaBtQD_A."
CkStringBuilder_Append $sbJwe "XFBoMYUZodetZdvTiFvSkQ"

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