Encrypt and Decrypt iOS/Node.js Security Inquiry - ios

Question

I'm currently using AES128 on both platforms and my code from this answer
Note: I changed the code a bit to deviate from using an IV because I thought it was overkill for the purpose of my application.
node.js:
var CryptoJS = require("crypto-js");
var crypto = require('crypto');
var password = "1234567890123456";
var salt = "gettingsaltyfoo!";
var hash = CryptoJS.SHA256(salt);
var key = CryptoJS.PBKDF2(password, hash, { keySize: 256/32, iterations: 1000 });
var algorithm = 'aes128';
console.log(key.toString(CryptoJS.enc.Base64));
function encrypt(text){
var cipher = crypto.createCipher(algorithm,key.toString(CryptoJS.enc.Base64));
var crypted = cipher.update(text,'utf8','hex');
crypted += cipher.final('hex');
return crypted;
}
function decrypt(text){
var decipher = crypto.createDecipher(algorithm,key.toString(CryptoJS.enc.Base64));
var dec = decipher.update(text,'hex','utf8');
dec += decipher.final('utf8');
return dec;
}
iOS:
#import <CommonCrypto/CommonCrypto.h>
NSString* password = #"1234567890123456";
NSString* salt = #"gettingsaltyfoo!";
-(NSString *)decrypt:(NSString*)encrypted64{
NSMutableData* hash = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
NSMutableData* key = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
CC_SHA256(salt.UTF8String, (CC_LONG)strlen(salt.UTF8String), hash.mutableBytes);
CCKeyDerivationPBKDF(kCCPBKDF2, password.UTF8String, strlen(password.UTF8String), hash.bytes, hash.length, kCCPRFHmacAlgSHA1, 1000, key.mutableBytes, key.length);
NSLog(#"Hash : %#",[hash base64EncodedStringWithOptions:0]);
NSLog(#"Key : %#",[key base64EncodedStringWithOptions:0]);
NSData* encryptedWithout64 = [[NSData alloc] initWithBase64EncodedString:encrypted64 options:0];
NSMutableData* decrypted = [NSMutableData dataWithLength:encryptedWithout64.length + kCCBlockSizeAES128];
size_t bytesDecrypted = 0;
CCCrypt(kCCDecrypt,
kCCAlgorithmAES128,
kCCOptionPKCS7Padding,
key.bytes,
key.length,
NULL,
encryptedWithout64.bytes, encryptedWithout64.length,
decrypted.mutableBytes, decrypted.length, &bytesDecrypted);
NSData* outputMessage = [NSMutableData dataWithBytes:decrypted.mutableBytes length:bytesDecrypted];
NSString* outputString = [[NSString alloc] initWithData:outputMessage encoding:NSUTF8StringEncoding];
NSLog(#"Decrypted : %#",outputString);
return outputString;
}
-(NSString *)encrypt:(NSString *)toEncrypt{
NSMutableData* hash = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
NSMutableData* key = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
CC_SHA256(salt.UTF8String, (CC_LONG)strlen(salt.UTF8String), hash.mutableBytes);
CCKeyDerivationPBKDF(kCCPBKDF2, password.UTF8String, strlen(password.UTF8String), hash.bytes, hash.length, kCCPRFHmacAlgSHA1, 1000, key.mutableBytes, key.length);
NSData* message = [toEncrypt dataUsingEncoding:NSUTF8StringEncoding];
NSMutableData* encrypted = [NSMutableData dataWithLength:message.length + kCCBlockSizeAES128];
size_t bytesEncrypted = 0;
CCCrypt(kCCEncrypt,
kCCAlgorithmAES128,
kCCOptionPKCS7Padding,
key.bytes,
key.length,
NULL,
message.bytes, message.length,
encrypted.mutableBytes, encrypted.length, &bytesEncrypted);
NSString* encrypted64 = [[NSMutableData dataWithBytes:encrypted.mutableBytes length:bytesEncrypted] base64EncodedStringWithOptions:0];
NSLog(#"Encrypted : %#",encrypted64);
return encrypted64;
}
MY QUESTION: Is it okay if I hardcode the salt like this? I'm trying to encrypt and decrypt the password (the var password and NSString password will probably be hardcoded into something). I've read online that I need to keep my salt with my password in my db. If it's not okay if I hardcode my salt, how do I send it from iOS to node.js and be consistent with the salt? Should my iOS request look like this?
{
key:"someKeyGeneratedOnTheSpotWithRandomSalt",
password:"somePasswordGeneratedFromKey"
}
and in my backend check the password by pulling these fields from the database?
{
key:"someKeyGeneratedWhenTheUserFirstSignedUp",
password:"somePasswordGeneratedFromTheOrginalKeyWhenUserFirstSignedUp"
}
And then decrypt both passwords using the key and password generated from both scenarios?
OR is it okay to have a hardcoded salt, say the username, so that way the key is always the same per user?
Basically I'm confused on whether or not I have the right idea for my encryption model.
Thanks for any assistance.

Answer 1

Typically a random salt is used and prepended to the encrypted data. It is also common to all prepend the PBKDF2 iteration count along with a version number helps for future-proofing. Finally, skipping an iv reduces the protection of the first block and you might consider an authentication hash.
This is similar to what RNCryptor does. See RNCryptor-Spec-v3.md for a detail of a encrypted message.
Notes:
I don't understand CC_SHA256 of the salt, that shouldn't be necessary.
NSData* outputMessage = [NSMutableData dataWithBytes:decrypted.mutableBytes
length:bytesDecrypted];
is unnecessary, just set the length of decrypted
decrypted.length = bytesDecrypted;
and use decrypted in place of outputMessage.