(PureBasic) openssl enc decrypt

Demonstrates how to decrypt a file that was encrypted using "openssl enc".

This example shows how to decrypt what was created using this openssl command:

openssl enc -e -aes-256-cbc -in hamlet.xml -out hamlet.enc -pass file:./secret.txt

This example shows how to do this:

openssl enc -d -aes-256-cbc -in hamlet.enc -out hamlet_dec.xml -pass file:./secret.txt

Note: This example requires Chilkat v9.5.0.71 or later.

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IncludeFile "CkCrypt2.pb"
IncludeFile "CkBinData.pb"

Procedure ChilkatExample()

    ; This example requires the Chilkat API to have been previously unlocked.
    ; See Global Unlock Sample for sample code.

    crypt.i = CkCrypt2::ckCreate()
    If crypt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Use aes-256-cbc
    CkCrypt2::setCkCryptAlgorithm(crypt, "aes")
    CkCrypt2::setCkCipherMode(crypt, "cbc")
    CkCrypt2::setCkKeyLength(crypt, 256)

    ; We'll need to set the hash algorithm to either MD5 or SHA256.
    ; openssl version 1.0.* or earlier used MD5 by default
    ; openssl version 1.1.* uses SHA-256 for the password to secret key derivation.

    ; For example, if openssl 1.1.0 was used, we should do this:
    CkCrypt2::setCkHashAlgorithm(crypt, "sha256")

    ; This example assumes openssl 1.0.2 was used to encrypt what we're now decrypting:
    CkCrypt2::setCkHashAlgorithm(crypt, "md5")

    ; The openssl command we are duplicating is:
    ; 
    ;    openssl enc -d -aes-256-cbc -in hamlet.enc -out hamlet_dec.xml -pass file:./secret.txt
    ; 
    ; The file secret.txt contains the word "secret".  We could write code to load the contents
    ; of secret.txt, but instead we'll just do this:
    CkCrypt2::ckSetSecretKeyViaPassword(crypt,"secret")

    ; Load the file to be decrypted.
    fileData.i = CkBinData::ckCreate()
    If fileData.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkBinData::ckLoadFile(fileData,"qa_data/openssl_enc/hamlet.enc")

    ; Decrypt
    success = CkCrypt2::ckDecryptBd(crypt,fileData)

    ; Save the decrypted output.
    success = CkBinData::ckWriteFile(fileData,"qa_output/hamlet_dec.xml")

    Debug "success = " + Str(success)


    CkCrypt2::ckDispose(crypt)
    CkBinData::ckDispose(fileData)


    ProcedureReturn
EndProcedure