We need to encrypt a request using AES128 in Android and IOS and then send that encrypted message in the backend server written in Java.
Our Android encryption code is like below:
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);
where keyspec and ivspec is random bytes generated.
In Objective-C, this is how we do the encryption.
NSString* iv = #"a12bc1256b4de9a0";
NSData* ivData = [iv dataUsingEncoding:NSUTF8StringEncoding];
NSMutableData* cipherData = [NSMutableData dataWithLength:data.length+kCCBlockSizeAES128];
CCCryptorStatus result = CCCrypt(kCCEncrypt, kCCAlgorithmAES, kCCOptionPKCS7Padding, keyData.bytes, keyData.length, ivData.bytes, data.bytes, data.length, cipherData.mutableBytes, cipherData
.length, &outLength);
The problem with this is that when we compare the encrypted byte of thee Java program and Objective-C, they are not the same. I understand that the CCOption parameter in Objective-C should be CBC but that is not in the enum list of the CommonCrypto library. When we set it 0, the encrypted byte only return a series of zeros.
Please suggest other alternatives on how to do the AES 128 encryption in Objective-C using AES/CBC/NOPadding Algorithm.
You've requested padding: kCCOptionPKCS7Padding. That's not the same thing as Java's NoPadding. Remove the padding option. (You can use 0 to mean "no options.")
It's also unclear whether every other part of your encryption it the same. You didn't include the key generation or IV in the Java code.
(Note that if you get the exact same bytes out of an encryption algorithm for the same message, then you're using the encryption algorithm in an insecure way. Secure encryption constructions will generate a different cipher text for every encryption. I understand that your server may be using this kind of insecure approach; it's a very common mistake. But it is insecure.)
Related
This question already has answers here:
Is it possible to use AES128 with GCM mode on iOS?
(3 answers)
Closed 6 years ago.
Currently the encryption mode supported with AES 256 is CBC. But I want to use AES 256 encryption with GCM mode along with PKCS5Padding / PKCS7Padding.
Do let me know how it can be done ?
Common Crypto does not support GCM. But there is an implementation of AES GCM in the Security.framework, and you can add your own header file to use it. However associated data (AEAD) does not work.
From SO Answer by soyer:
CCCryptorStatus CCCryptorGCM(
CCOperation op, // kCCEncrypt, kCCDecrypt
CCAlgorithm kCCAlgorithmAES,
const void *key, size_t keyLength,
const void *iv, size_t ivLen,
const void *aData, size_t aDataLen, // does not work
const void *dataIn, size_t dataInLength,
void *dataOut,
const void *tag, size_t *tagLength);
There is an implemntation AES GCM on github that seems reasonable albiet slow in comparison to Common Crypto. Use at your own risk.
I'm trying to do RSA2048 in iOS and am following the example codes from Apple and also this question RSA implementations in Objective C. I have tested on iPhone 5c with iOS 8.4.1, but the sample codes fail at decryption with private key, with error code -9809 (An underlying cryptographic error was encountered), even though encryption with public key. I understand the basic approach is to generate an RSA key pair, secure them in keychain and use public key ref to encrypt and private key to decrypt. I'm completely lost why decryption shall fail, and not always, there are times when decryption succeeded.
Full codes can be found at https://gist.github.com/aceisScope/372e6d6f92650ce03624. The decryption part that throws an error is below, where from time to time status = -9809, and other times it works and returns 0:
status = SecKeyDecrypt(privateKey,
PADDING,
cipherBuffer,
cipherBufferSize,
plainBuffer,
&plainBufferSize
);
I have also set a check that if such key pair has already generated, next time encryption/decryption is called, it will directly using the already-generated-and-stored key pair from key chain without generating a new pair.
Update:
I came across this post iPhone Public-Key Encryption SecKeyEncrypt returns error 9809 (errSSLCrypto) which found out wrong cipher buffer size may cause -9809 error to encryption. Yet even if I make sure both the cipher buffer size in encryption and plain buffer size in decryption is the same as key block size and private key block size, encryption always works but with decryption failing from time to time.
I found the problem. By the end of encryption, when converting cipher buffer to NSData, in the following code
NSMutableData *data=[[NSMutableData alloc] init];
[data appendBytes:cipherBuffer length:strlen( (char*)cipherBuffer ) + 1];
the length is not correct. It should be the size of the cipher buffer, which is the same as key block size.
So after changing it to
NSData *data = [NSData dataWithBytes:cipherBuffer length:cipherBufferSize];
decryption works now.
Here is how I encrypt the string:
+ (NSString *)encrypt:(NSString *)message password:(NSString *)password {
NSData *encryptedData = [[message dataUsingEncoding:NSUTF8StringEncoding] AES256EncryptedDataUsingKey:[password dataUsingEncoding:NSUTF8StringEncoding] error:nil];
NSString *base64EncodedString = [NSString base64StringFromData:encryptedData length:[encryptedData length]];
return base64EncodedString;
}
The plain text is:
{"roomID":"{\"array\":[\"949156\",\"949157\"]}","duration":15,"link":"","type":"text","thumbnailBlobID":"","posy":103.6809424405021,"text":"Aa","className":"Message","originalBlobID":"","datetime":"20140319214528457","selfDestructive":0,"userID":"949157","posx":1.347154229880634,"status":"normal","entityID":"20140319214528457and949157and{\"array\":[\"949156\",\"949157\"]}"}
This is what I get
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
From website http://aesencryption.net (256 bit)
(Which i assume to be the correct answer
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
There is no single standard way to apply AES, or standard data format for the output. AES requires a number of helpers when used on data that is not exactly 16-bytes long, and they can be configured in different ways. I have no idea how the aesencryption.net tool is applying these helpers; it doesn't say. If AES256EncryptedDataUsingKey: is the particular piece of code I assume it, it applies them very poorly (it's very similar to the code I discuss in Properly Encrypting With AES With CommonCrypto). I would not be surprised if aesencryption.net does something different.
If you have a piece of plaintext and a key, and you pass it to an encryptor twice and get the same answer back, then your encryptor is broken. A correct AES encryptor (for almost any common use of AES) should always return different results for the same plaintext+key (otherwise an attacker can determine that two plaintexts are equal, which breaks the security proof of AES). In the most common case, this is achieved by having a unique initialization vector (IV). For password-based AES, you also include a random salt. So even if these were good implementations of AES, you wouldn't expect your results to match.
Is it possible that the escape characters (the back slashes) are being interpreted differently in code versus via the web? The bottom line here is I would (in code) decode what you just encoded and you should come out with the same as what you put in. This is probably the test you want to conduct. Hope this helps. Also see comment below from #RobNapier
My question is about this question:
Is your product designed to use cryptography or does it contain or incorporate cryptography?
I don't know what to answer because my app is using the commoncrypto framework and md5 encryption. What should I answer?
Codes used in App:
(NSString *) md5:(NSString *) input
{
const char *cStr = [input UTF8String];
unsigned char digest[16];
CC_MD5( cStr, strlen(cStr), digest ); // This is the md5 call
NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
[output appendFormat:#"%02x", digest[i]];
return output;
}
md5 is a hash function and hash functions are one-way and are not encryption.
If all you are using is a hash function the answer is No you are not using encryption.
If you are using AES, DES of other encryption, that is two-way crypto functions then the answer is YES.
Merely adding the CommonCrypto framework makes no difference, it is the usage of encryption that counts.
The only concern is any encryption in the app, there is no concern with anything done on a related server.
iTunes Connect does not care server-side implementation.
If you use MD5 or any other encryption mechanism in server side (but not in App side), you should choose No for the answer.
I'm trying to implement decryption of a PGP file on an iPad. I set up some test .txt files which I then encrypted via PGP desktop.
I've imported the private key of the certificate used to encrypt the document, using SecPKCS12Import, then SecIdentityCopyPrivateKey() from the resulting SecIdentityRef.
If I test encrypting and decrypting a simple string in Objective C, using the public and private key of the cert, that works perfectly.
Now that I'm trialling the actual PGP decryption, I'm a bit stumped... Reading the text from the .pgp file, I get:
-----BEGIN PGP MESSAGE-----
Version: 10.1.1.10
qANQR1DBwEwDraQm2Kxa5GkBB/4yLebeLk10C2DVvHpQL20E0DThhgQlTasXo+YJ
pLp5Ig2hHu4Xx0m74D3vfyWpA2XQA02TMAHO9lhNfkE234c/ds05D1UyQkJEoqW+
joEcbRT5rlGN3qrMf1FXv8/01EHH0dgeD6mAkkDeDEorIirYHCF6+QVkedaphZLs
c63GmcikzkWZT/vv20ICL3Ys0DaC3P9zu0T1GtjkmQ062kaTab/VBJnQrsY/y1JU
ypmbW9bbFeZMcAqXHMqpjw49K5UluIJaDbRNAjIvHTFLNuOYWVJM6FcMs5p6xqvZ
ltizeKAjr1B1h4DvbQaqdO6/OAb+dGr7fJoIHEszDsJbW1cc0lUBitrxKHrPGovF
1uEW+3glA3SopveWB4GkKzcYlbqT5y1p/gQNwY8yuZr/6iF1hyF9mx/hU/+xjOMB
og3sGX4npcQegsAMw2y+zz9kJ9a6jlteNufi
=d2Fq
-----END PGP MESSAGE-----
I know that I need to get the random one-time key, that PGP used to encrypt the file, from the data in the file. I know that to do that, I need to use SecKeyDecrypt with the private key, to obtain the one-time AES key. Once I have that key, I can then decrypt the rest of the data.
The part I'm having problems with is which part of the data to feed into SecKeyDecrypt. How is the PGP file setup - is the first 128 chars the AES key? Unless my understanding is wrong, I need to get that out separately from the data.
If I run, say, the first 128 chars as a void through the SecKeyDecrypt function: (after stripping the BEGIN PGP MESSAGE lines)
size_t dataLength = [theKey length];
size_t outputLength = MAX(128, SecKeyGetBlockSize(privateKeyRef));
void *outputBuf = malloc(outputLength);
OSStatus err;
err = SecKeyDecrypt(privateKeyRef, kSecPaddingNone,//PKCS1,
(uint8_t *)theKey, dataLength,
outputBuf, &outputLength);
if (err) {
NSLog(#"something went wrong...err = %ld", err);
}
I get this:
MRªh6∞bJ˘e£t*˝ã=ŒA¢Òt‘ŸY±éÿAÃîâG
Îfi≠$b≈tâç`yxk=uHªqu-,–dïn^™È\›5±tb.‡€Kñ⁄≤sΩw–ïʃkafS˘À*Æô竡rAyv)fi]wOrµKz^ªq“à∑öΓı*r<+l˝Äo∑›g≠¶/÷eÔ&€PÒRåêM¶Ñ|Q$á6În^võ¬∏·h(ƒß•R≤(flò(*•Aa
I don't know what encoding this is, but trying to get it from the outputBuf into a string never works 100%. It seems to get modified no matter what encoding I pass it. If I pass it to NSData first, I can get the original string back.
NSData *keyData = [NSData dataWithBytesNoCopy:outputBuf length:outputLength];
NSString *keyFromData = [[NSString alloc] initWithBytes:[keyData bytes] length:[keyData length] encoding:NSASCIIStringEncoding];
I then try to pass that key to an AES256DecryptWithKey class, providing it with the remaining data from the PGP file, after the first 128 chars.
NSData *cipherText = [[NSData alloc]initWithData:[[bodyPart objectAtIndex:1] dataUsingEncoding:NSUTF8StringEncoding]];
NSData *plain = [[NSData alloc] initWithData:[cipherText AES256DecryptWithKey:keyFromData]];
NSLog(#"after decrypting = %#", [[NSString alloc] initWithData:plain encoding:NSUTF8StringEncoding]);
Problem:
The resulting data 'plain' prints as <> i.e. empty. My problem is I don't even think I know how to grab the key from the PGP file.
Can anyone explain to me the PGP file setup? What part is the 'key' if it is in fact separate from the data at all? Is it always the same length/ same position? If it's NOT separate then I don't know how I'd be able to grab it at all. I think the rest would work fine. I'm not getting any errors or crashes, it's just NOT the right key and/or data I'm passing for AES decryption, I suspect probably a combination of string encoding error and not grabbing the right amount for the AES key/ right combination.
Note -
I created 3 different text files and ran them through the PGP process. Inspecting them, they all started with the same 24 characters (qANQR1DBwEwDraQm2Kxa5GkB). Even if I pass these 24 through the decryption, it doesn't work, and I was under the impression that the AES key PGP used was different for every single document. Did I get that wrong?
Thanks for any step in the right direction!
Edited to add:
Just noticed partly my mistake - AES of 128 requires 16 bits, so either way I am taking the wrong amount by using 128 characters, stupid mistake, think I've been looking at this too long... Swapped it out and didn't work. Any decryption I do is resulting in the '⁄Ĉ¢ï¡0M¶È2Cˆ¿©gUú¨6iîΩ`&<%Jœv£¯nRb∆:(–%' type result, which to me implies I've done something wrong OR need to do something further with encoding.
Read RFC 4880. That file is an ASCII-Armored collection of PGP packets. There are 1 or more packets that contain the symmetric key needed to decrypt the actual message, each of the symmetric key packets is encrypted with the public key of a recipient. Only people who possess the right private key can decrypt the symmetric key packet and then use that symmetric key to decrypt the rest of the message.
The AES key is indeed different.
It is randomly selected, and the encrypted with the public key system (RSA, typically).
Pub key has costs and limitations that make it unattractive to use for bulk.
You might want to look at the NetPGP, which is C code under the
BSD license, which means you can incorporate it or modify it
without encumbering your app or upsetting Apple in any way.
(Of course, contributions of source code or money would be
appreciated by the project. I'm not affiliated with them.)
The OpenPGP standard is a lot of work to implement.
Even once an implementation works, there are countless
ways in which it can be insecure.