smokingoyster smokingoyster - 5 months ago 149
Objective-C Question

PBEWithMD5AndDES Encryption in iOS

I'm having an issue with PBEWithMD5AndDES encryption in iOS. I've got my strings encrypting and decrypting using this, https://gist.github.com/788840/24bc73ecd0ac3134cbd242892c74a06ac561d37b.

The problem is I get different encrypted values depending on which class my methods are in. For example, I moved all the encryption methods into a helper class and ran it. I noticed I was getting a different encrypted value.

I now have two identical versions of the same method in different classes and I'm running them side by side. They get different encrypted values, and one cannot decrypt the others'. I'm kind of stumped on this.

Here's the helper class that does encryption/decryption.

@implementation CryptoHelper

#pragma mark -
#pragma mark Init Methods
- (id)init
{
if(self = [super init])
{

}
return self;
}

#pragma mark -
#pragma mark String Specific Methods

/**
* Encrypts a string for social blast service.
*
* @param plainString The string to encrypt;
*
* @return NSString The encrypted string.
*/
- (NSString *)encryptString: (NSString *) plainString{

// Convert string to data and encrypt
NSData *data = [self encryptPBEWithMD5AndDESData:[plainString dataUsingEncoding:NSUTF8StringEncoding] password:@"1111"];



// Get encrypted string from data
return [data base64EncodingWithLineLength:1024];

}


/**
* Descrypts a string from social blast service.
*
* @param plainString The string to decrypt;
*
* @return NSString The decrypted string.
*/
- (NSString *)decryptString: (NSString *) encryptedString{

// decrypt the data
NSData * data = [self decryptPBEWithMD5AndDESData:[NSData dataWithBase64EncodedString:encryptedString] password:@"1111"];

// extract and return string
return [NSString stringWithUTF8String:[data bytes]];

}


#pragma mark -
#pragma mark Crypto Methods

- (NSData *)encryptPBEWithMD5AndDESData:(NSData *)inData password:(NSString *)password {
return [self encodePBEWithMD5AndDESData:inData password:password direction:1];
}

- (NSData *)decryptPBEWithMD5AndDESData:(NSData *)inData password:(NSString *)password {
return [self encodePBEWithMD5AndDESData:inData password:password direction:0];
}

- (NSData *)encodePBEWithMD5AndDESData:(NSData *)inData password:(NSString *)password direction:(int)direction
{
NSLog(@"helper data = %@", inData);

static const char gSalt[] =
{
(unsigned char)0xAA, (unsigned char)0xAA, (unsigned char)0xAA, (unsigned char)0xAA,
(unsigned char)0xAA, (unsigned char)0xAA, (unsigned char)0xAA, (unsigned char)0xAA
};

unsigned char *salt = (unsigned char *)gSalt;
int saltLen = strlen(gSalt);
int iterations = 15;

EVP_CIPHER_CTX cipherCtx;


unsigned char *mResults; // allocated storage of results
int mResultsLen = 0;

const char *cPassword = [password UTF8String];

unsigned char *mData = (unsigned char *)[inData bytes];
int mDataLen = [inData length];


SSLeay_add_all_algorithms();
/*X509_ALGOR *algorithm = PKCS5_pbe_set(NID_pbeWithMD5AndDES_CBC,
iterations, salt, saltLen);*/
const EVP_CIPHER *cipher = EVP_des_cbc();

// Need to set with iv
X509_ALGOR *algorithm = PKCS5_pbe2_set_iv(cipher, iterations,
salt, saltLen, salt, NID_hmacWithMD5);


memset(&cipherCtx, 0, sizeof(cipherCtx));

if (algorithm != NULL)
{
EVP_CIPHER_CTX_init(&(cipherCtx));



if (EVP_PBE_CipherInit(algorithm->algorithm, cPassword, strlen(cPassword),
algorithm->parameter, &(cipherCtx), direction))
{

EVP_CIPHER_CTX_set_padding(&cipherCtx, 1);

int blockSize = EVP_CIPHER_CTX_block_size(&cipherCtx);
int allocLen = mDataLen + blockSize + 1; // plus 1 for null terminator on decrypt
mResults = (unsigned char *)OPENSSL_malloc(allocLen);


unsigned char *in_bytes = mData;
int inLen = mDataLen;
unsigned char *out_bytes = mResults;
int outLen = 0;



int outLenPart1 = 0;
if (EVP_CipherUpdate(&(cipherCtx), out_bytes, &outLenPart1, in_bytes, inLen))
{
out_bytes += outLenPart1;
int outLenPart2 = 0;
if (EVP_CipherFinal(&(cipherCtx), out_bytes, &outLenPart2))
{
outLen += outLenPart1 + outLenPart2;
mResults[outLen] = 0;
mResultsLen = outLen;
}
} else {
unsigned long err = ERR_get_error();

ERR_load_crypto_strings();
ERR_load_ERR_strings();
char errbuff[256];
errbuff[0] = 0;
ERR_error_string_n(err, errbuff, sizeof(errbuff));
NSLog(@"OpenSLL ERROR:\n\tlib:%s\n\tfunction:%s\n\treason:%s\n",
ERR_lib_error_string(err),
ERR_func_error_string(err),
ERR_reason_error_string(err));
ERR_free_strings();
}


NSData *encryptedData = [NSData dataWithBytes:mResults length:mResultsLen]; //(NSData *)encr_buf;


//NSLog(@"encryption result: %@\n", [encryptedData base64EncodingWithLineLength:1024]);

EVP_cleanup();

return encryptedData;
}
}
EVP_cleanup();
return nil;

}

@end


I'm trying to duplicate the results of this java function. I have the same salt.

public DesEncrypter(String passPhrase) {
try {
// Create the key
KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt, iterationCount);
SecretKey key = SecretKeyFactory.getInstance(
"PBEWithMD5AndDES").generateSecret(keySpec);
ecipher = Cipher.getInstance(key.getAlgorithm());
dcipher = Cipher.getInstance(key.getAlgorithm());

// Prepare the parameter to the ciphers
AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt, iterationCount);

// Create the ciphers
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
} catch (java.security.InvalidAlgorithmParameterException e) {
} catch (java.security.spec.InvalidKeySpecException e) {
} catch (javax.crypto.NoSuchPaddingException e) {
} catch (java.security.NoSuchAlgorithmException e) {
} catch (java.security.InvalidKeyException e) {
}
}

Answer

Not sure what the protocol is here for accepting answers/upvoting them. I apologize if I'm doing this wrong. The answer turned out to be the lack of a final byte in the salt. I actually didn't need the IV with the 3DES encryption. I upvoted the other answer because it was helpful in understanding more about encryption.

Here's the final objective c class.

@implementation CryptoHelper

#pragma mark -
#pragma mark Init Methods
- (id)init
{
    if(self = [super init])
    {

    }
    return self;
}

#pragma mark -
#pragma mark String Specific Methods

/** 
 *  Encrypts a string for social blast service. 
 *  
 *  @param  plainString The string to encrypt;
 *
 *  @return NSString    The encrypted string. 
 */
- (NSString *)encryptString: (NSString *) plainString{

    // Convert string to data and encrypt
    NSData *data = [self encryptPBEWithMD5AndDESData:[plainString dataUsingEncoding:NSUTF8StringEncoding] password:@"1111"];



    // Get encrypted string from data
    return [data base64EncodingWithLineLength:1024];

}


/** 
 *  Descrypts a string from social blast service. 
 *  
 *  @param  plainString The string to decrypt;
 *
 *  @return NSString    The decrypted string. 
 */
- (NSString *)decryptString: (NSString *) encryptedString{

    // decrypt the data
    NSData * data = [self decryptPBEWithMD5AndDESData:[NSData dataWithBase64EncodedString:encryptedString] password:@"1111"];

    // extract and return string
    return [NSString stringWithUTF8String:[data bytes]];

}


#pragma mark -
#pragma mark Crypto Methods

- (NSData *)encryptPBEWithMD5AndDESData:(NSData *)inData password:(NSString *)password {
    return [self encodePBEWithMD5AndDESData:inData password:password direction:1];
}

- (NSData *)decryptPBEWithMD5AndDESData:(NSData *)inData password:(NSString *)password {
    return [self encodePBEWithMD5AndDESData:inData password:password direction:0];
}

- (NSData *)encodePBEWithMD5AndDESData:(NSData *)inData password:(NSString *)password direction:(int)direction
{
    NSLog(@"helper data = %@", inData);

    static const char gSalt[] =
    {
        (unsigned char)0xAA, (unsigned char)0xAA, (unsigned char)0xAA, (unsigned char)0xAA,
        (unsigned char)0xAA, (unsigned char)0xAA, (unsigned char)0xAA, (unsigned char)0xAA,
        (unsigned char)0x00
    };

    unsigned char *salt = (unsigned char *)gSalt;
    int saltLen = strlen(gSalt);
    int iterations = 15;

    EVP_CIPHER_CTX cipherCtx;


    unsigned char *mResults; // allocated storage of results
    int mResultsLen = 0;

    const char *cPassword = [password UTF8String];

    unsigned char *mData = (unsigned char *)[inData bytes];
    int mDataLen = [inData length];


    SSLeay_add_all_algorithms();
    X509_ALGOR *algorithm = PKCS5_pbe_set(NID_pbeWithMD5AndDES_CBC,
                                          iterations, salt, saltLen);



    memset(&cipherCtx, 0, sizeof(cipherCtx));

    if (algorithm != NULL)
    {
        EVP_CIPHER_CTX_init(&(cipherCtx));



        if (EVP_PBE_CipherInit(algorithm->algorithm, cPassword, strlen(cPassword),
                               algorithm->parameter, &(cipherCtx), direction))
        {

            EVP_CIPHER_CTX_set_padding(&cipherCtx, 1);

            int blockSize = EVP_CIPHER_CTX_block_size(&cipherCtx);
            int allocLen = mDataLen + blockSize + 1; // plus 1 for null terminator on decrypt
            mResults = (unsigned char *)OPENSSL_malloc(allocLen);


            unsigned char *in_bytes = mData;
            int inLen = mDataLen;
            unsigned char *out_bytes = mResults;
            int outLen = 0;



            int outLenPart1 = 0;
            if (EVP_CipherUpdate(&(cipherCtx), out_bytes, &outLenPart1, in_bytes, inLen))
            {
                out_bytes += outLenPart1;
                int outLenPart2 = 0;
                if (EVP_CipherFinal(&(cipherCtx), out_bytes, &outLenPart2))
                {
                    outLen += outLenPart1 + outLenPart2;
                    mResults[outLen] = 0;
                    mResultsLen = outLen;
                }
            } else {
                unsigned long err = ERR_get_error();

                ERR_load_crypto_strings();
                ERR_load_ERR_strings();
                char errbuff[256];
                errbuff[0] = 0;
                ERR_error_string_n(err, errbuff, sizeof(errbuff));
                NSLog(@"OpenSLL ERROR:\n\tlib:%s\n\tfunction:%s\n\treason:%s\n",
                      ERR_lib_error_string(err),
                      ERR_func_error_string(err),
                      ERR_reason_error_string(err));
                ERR_free_strings();
            }


            NSData *encryptedData = [NSData dataWithBytes:mResults length:mResultsLen]; //(NSData *)encr_buf;


            //NSLog(@"encryption result: %@\n", [encryptedData base64EncodingWithLineLength:1024]);

            EVP_cleanup();

            return encryptedData;
        }
    }
    EVP_cleanup();
    return nil;

}

@end