(Objective-C) 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 v11.1.0 or greater.

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#import <CkoCrypt2.h>
#import <CkoBinData.h>

BOOL success = NO;

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

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];

// Use aes-256-cbc
crypt.CryptAlgorithm = @"aes";
crypt.CipherMode = @"cbc";
crypt.KeyLength = [NSNumber numberWithInt: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:
crypt.HashAlgorithm = @"sha256";

// This example assumes openssl 1.0.2 was used to encrypt what we're now decrypting:
crypt.HashAlgorithm = @"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:
[crypt SetEncodedKey: @"secret" encoding: @"openssl"];

// Load the file to be decrypted.
CkoBinData *fileData = [[CkoBinData alloc] init];
success = [fileData LoadFile: @"qa_data/openssl_enc/hamlet.enc"];

// Decrypt
crypt.VerboseLogging = YES;
success = [crypt DecryptBd: fileData];
NSLog(@"%@",crypt.LastErrorText);

// Save the decrypted output.
success = [fileData WriteFile: @"c:/temp/qa_output/hamlet_dec.xml"];

NSLog(@"%@%d",@"success = ",success);