(C) Duplicate PHP's openssl_encrypt and openssl_random_pseudo_bytes

Demonstrates how to duplicate PHP's openssl_encrypt function. (https://www.php.net/manual/en/function.openssl-encrypt.php)

For more information, see https://www.php.net/manual/en/function.openssl-encrypt.php

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#include <C_CkCrypt2.h>
#include <C_CkBinData.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkCrypt2 crypt;
    const char *text;
    const char *passphrase;
    const char *ivBase64;
    HCkBinData bdKey;
    int sz;
    const char *cipherText64;
    HCkBinData bd;
    const char *result;
    HCkBinData bdResult;
    const char *originalText;

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

    // Duplicates thw following PHP script:

    // $text = "This is a test";
    // $passphrase = "my password";
    // $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length("AES-256-CBC"));
    // $crypted = base64_encode($iv.openssl_encrypt($text, "AES-256-CBC", $passphrase, OPENSSL_RAW_DATA, $iv));
    // echo $crypted;

    crypt = CkCrypt2_Create();

    text = "This is a test";
    passphrase = "my password";

    // AES is a block cipher.  The IV size for any block cipher is the size of the block, which is defined by the encryption algorithm. 
    // For AES, the block size is always 16 bytes, regardless of key size (i.e. 128-bits, 192-bits, or 256-bits).
    // Therefore, generate 16 random bytes for the IV.
    CkCrypt2_putEncodingMode(crypt,"base64");
    ivBase64 = CkCrypt2_genRandomBytesENC(crypt,16);

    printf("Generated IV = %s\n",ivBase64);

    // Because we're doing AES-256-CBC, the key length must be 256-bits (i.e. 32 bytes).
    // Given that our passphrase is a us-ascii string that can be shorter or longer than 32-bytes, we need to 
    // somehow transform the passphrase to a 32-byte secret key.  We need to know what openssl_encrypt does.
    // Here's the answer from the openssl_encrypt documentation:
    // 
    // "If the passphrase is shorter than expected, it is silently padded with NUL characters; 
    // if the passphrase is longer than expected, it is silently truncated."

    // OK.... so let's pad or shorten to get a 32-byte key.
    bdKey = CkBinData_Create();
    CkBinData_AppendString(bdKey,passphrase,"utf-8");

    sz = CkBinData_getNumBytes(bdKey);
    if (sz > 32) {
        CkBinData_RemoveChunk(bdKey,32,sz - 32);
    }
    else {
        CkBinData_Clear(bdKey);
        CkBinData_AppendPadded(bdKey,passphrase,"utf-8",FALSE,32);
    }

    // Setup for encryption.
    CkCrypt2_putCryptAlgorithm(crypt,"aes");
    CkCrypt2_putKeyLength(crypt,256);
    CkCrypt2_SetEncodedIV(crypt,ivBase64,"base64");
    CkCrypt2_SetEncodedKey(crypt,CkBinData_getEncoded(bdKey,"base64"),"base64");

    // Encrypt and base64 encode.
    cipherText64 = CkCrypt2_encryptStringENC(crypt,text);

    // The PHP code fragment above returns the base64 encoded bytes of the IV and the encrypted text.
    // So let's do that..
    bd = CkBinData_Create();
    CkBinData_AppendEncoded(bd,ivBase64,"base64");
    CkBinData_AppendEncoded(bd,cipherText64,"base64");
    result = CkBinData_getEncoded(bd,"base64");

    printf("result = %s\n",result);

    // Sample output:
    // dN0vS1O0cWi5BbLAAY+NTf7bs3S27xzPf11RkG47sjs=

    // Now let's decrypt from the output...

    // Setup for decryption.
    CkCrypt2_putCryptAlgorithm(crypt,"aes");
    CkCrypt2_putKeyLength(crypt,256);
    CkCrypt2_SetEncodedKey(crypt,CkBinData_getEncoded(bdKey,"base64"),"base64");

    bdResult = CkBinData_Create();
    CkBinData_AppendEncoded(bdResult,result,"base64");
    CkCrypt2_SetEncodedIV(crypt,CkBinData_getEncodedChunk(bdResult,0,16,"base64"),"base64");

    // Remove the IV (first 16 bytes) from the result.
    CkBinData_RemoveChunk(bdResult,0,16);
    success = CkCrypt2_DecryptBd(crypt,bdResult);
    originalText = CkBinData_getString(bdResult,"utf-8");

    printf("original text = %s\n",originalText);


    CkCrypt2_Dispose(crypt);
    CkBinData_Dispose(bdKey);
    CkBinData_Dispose(bd);
    CkBinData_Dispose(bdResult);

    }