Question

I have an encrypted MP3 file. The file was encrypted using the following openssl method

openssl enc -e -aes-128-cbc -K 00ff349830193845af43984758690213 -p -iv 0 -nosalt -in  input.mp3 -out output.mp3

Then I’m trying decrypt the file in my ios application as follows,

NSString *resourceDocPath = [[NSString alloc] initWithString:[[NSBundle mainBundle] bundlePath]] ;
NSString *filePath = [resourceDocPath stringByAppendingPathComponent:@"output.mp3"];
NSData *key = [@"00ff349830193845af43984758690213" dataUsingEncoding:NSUTF8StringEncoding];
NSData *iv = [@"00000000000000000000000000000000" dataUsingEncoding:NSUTF8StringEncoding];
NSData *fileData = [[NSData alloc] initWithContentsOfFile:filePath];
NSData *decryptData;

CCCryptorStatus ccStatus   = kCCSuccess;
size_t          cryptBytes = 0;    // Number of bytes moved to buffer.
NSMutableData  *dataOut    = [NSMutableData dataWithLength:fileData.length + kCCBlockSizeAES128];

ccStatus = CCCrypt(kCCDecrypt,
                   kCCAlgorithmAES128,
                   kSecPaddingNone,
                   key.bytes,
                   kCCKeySizeAES128,
                   iv.bytes,
                   fileData.bytes,
                   fileData.length,
                   dataOut.mutableBytes,
                   dataOut.length,
                   &cryptBytes);

if (ccStatus != kCCSuccess) {
    NSLog(@"CCCrypt status: %d", ccStatus);
}    
dataOut.length = cryptBytes;
decryptData = dataOut;

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"MyDECFile.mp3"];
[decrypt writeToFile:appFile atomically:YES];
NSLog(@"%@",documentsDirectory);

Now I have the decrypted MP3 file in document directory, But its not playing and literally its a junk output. Please suggest me a way to get the desired output.

Answer 1

I have used https://github.com/rnapier/RNCryptor for decryption.

#import "ViewController.h"
#import <Security/Security.h>
#import <MediaPlayer/MediaPlayer.h>
#import "RNEncryptor.h"
#import "RNDecryptor.h"
#import "RNOpenSSLEncryptor.h"
#import "RNOpenSSLDecryptor.h"

NSString *resourceDocPath = [[NSString alloc] initWithString:[[NSBundle mainBundle] bundlePath]] ;
NSString *filePath1 = [resourceDocPath stringByAppendingPathComponent:@"output.mp3"]; //The encrypted mp3 file (with aPassword)
NSData *passEncryptedData =[[NSData alloc] initWithContentsOfFile:filePath1]; 
NSError *error;   
NSString *pass = @"aPassword";    
NSData *dataDecrypted = [RNOpenSSLDecryptor decryptData:passEncryptedData 
                                           withSettings:kRNCryptorAES256Settings
                                               password:pass
                                                  error:&error];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"passDecryptFile.mp3"]; //The Decrypted file saved here
[dataDecrypted writeToFile:appFile atomically:YES];
NSLog(@"%@",documentsDirectory);