Index 16 out of bounds; string length 0 in swift - ios

Question

i try to decode some string, which encoded within AES. When the input is string without encode. My app crash. Log:
Terminating app due to uncaught exception 'NSRangeException', reason: '** -[__NSCFConstantString substringFromIndex:]: Index 16 out of bounds; string length 0'*
i used cryptLib to encode and decode
#import "CryptLib.h"
#implementation CryptLib
- (NSData *)encrypt:(NSData *)plainText key:(NSString *)key iv:(NSString *)iv {
char keyPointer[kCCKeySizeAES256+2],// room for terminator (unused) ref: https://devforums.apple.com/message/876053#876053
ivPointer[kCCBlockSizeAES128+2];
BOOL patchNeeded;
bzero(keyPointer, sizeof(keyPointer)); // fill with zeroes for padding
patchNeeded= ([key length] > kCCKeySizeAES256+1);
if(patchNeeded)
{
NSLog(#"Key length is longer %lu", (unsigned long)[[self md5:key] length]);
key = [key substringToIndex:kCCKeySizeAES256]; // Ensure that the key isn't longer than what's needed (kCCKeySizeAES256)
}
//NSLog(#"md5 :%#", key);
[key getCString:keyPointer maxLength:sizeof(keyPointer) encoding:NSUTF8StringEncoding];
[iv getCString:ivPointer maxLength:sizeof(ivPointer) encoding:NSUTF8StringEncoding];
if (patchNeeded) {
keyPointer[0] = '\0'; // Previous iOS version than iOS7 set the first char to '\0' if the key was longer than kCCKeySizeAES256
}
NSUInteger dataLength = [plainText length];
//see https://developer.apple.com/library/ios/documentation/System/Conceptual/ManPages_iPhoneOS/man3/CCryptorCreateFromData.3cc.html
// For block ciphers, the output size will always be less than or equal to the input size plus the size of one block.
size_t buffSize = dataLength + kCCBlockSizeAES128;
void *buff = malloc(buffSize);
size_t numBytesEncrypted = 0;
//refer to http://www.opensource.apple.com/source/CommonCrypto/CommonCrypto-36064/CommonCrypto/CommonCryptor.h
//for details on this function
//Stateless, one-shot encrypt or decrypt operation.
CCCryptorStatus status = CCCrypt(kCCEncrypt, /* kCCEncrypt, etc. */
kCCAlgorithmAES128, /* kCCAlgorithmAES128, etc. */
kCCOptionPKCS7Padding, /* kCCOptionPKCS7Padding, etc. */
keyPointer, kCCKeySizeAES256, /* key and its length */
ivPointer, /* initialization vector - use random IV everytime */
[plainText bytes], [plainText length], /* input */
buff, buffSize,/* data RETURNED here */
&numBytesEncrypted);
if (status == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buff length:numBytesEncrypted];
}
free(buff);
return nil;
}
-(NSData *)decrypt:(NSData *)encryptedText key:(NSString *)key iv:(NSString *)iv {
char keyPointer[kCCKeySizeAES256+2],// room for terminator (unused) ref: https://devforums.apple.com/message/876053#876053
ivPointer[kCCBlockSizeAES128+2];
BOOL patchNeeded;
patchNeeded = ([key length] > kCCKeySizeAES256+1);
if(patchNeeded)
{
NSLog(#"Key length is longer %lu", (unsigned long)[[self md5:key] length]);
key = [key substringToIndex:kCCKeySizeAES256]; // Ensure that the key isn't longer than what's needed (kCCKeySizeAES256)
}
[key getCString:keyPointer maxLength:sizeof(keyPointer) encoding:NSUTF8StringEncoding];
[iv getCString:ivPointer maxLength:sizeof(ivPointer) encoding:NSUTF8StringEncoding];
if (patchNeeded) {
keyPointer[0] = '\0'; // Previous iOS version than iOS7 set the first char to '\0' if the key was longer than kCCKeySizeAES256
}
NSUInteger dataLength = [encryptedText length];
//see https://developer.apple.com/library/ios/documentation/System/Conceptual/ManPages_iPhoneOS/man3/CCryptorCreateFromData.3cc.html
// For block ciphers, the output size will always be less than or equal to the input size plus the size of one block.
size_t buffSize = dataLength + kCCBlockSizeAES128;
void *buff = malloc(buffSize);
size_t numBytesEncrypted = 0;
//refer to http://www.opensource.apple.com/source/CommonCrypto/CommonCrypto-36064/CommonCrypto/CommonCryptor.h
//for details on this function
//Stateless, one-shot encrypt or decrypt operation.
CCCryptorStatus status = CCCrypt(kCCDecrypt,/* kCCEncrypt, etc. */
kCCAlgorithmAES128, /* kCCAlgorithmAES128, etc. */
kCCOptionPKCS7Padding, /* kCCOptionPKCS7Padding, etc. */
keyPointer, kCCKeySizeAES256,/* key and its length */
ivPointer, /* initialization vector - use same IV which was used for decryption */
[encryptedText bytes], [encryptedText length], //input
buff, buffSize,//output
&numBytesEncrypted);
if (status == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buff length:numBytesEncrypted];
}
free(buff);
return nil;
}
- (NSString *) encryptPlainText:(NSString *)plainText key:(NSString *)key iv:(NSString *)iv {
return [[[[CryptLib alloc] init] encrypt:[plainText dataUsingEncoding:NSUTF8StringEncoding] key:[[CryptLib alloc] sha256:key length:32] iv:iv] base64EncodedStringWithOptions:0];
}
- (NSString *) decryptCipherText:(NSString *)ciperText key:(NSString *)key iv:(NSString *)iv {
return [[NSString alloc] initWithData:[[CryptLib alloc] decrypt:[[NSData alloc] initWithBase64EncodedString:ciperText options:NSDataBase64DecodingIgnoreUnknownCharacters] key:[[CryptLib alloc] sha256:key length:32] iv:[[CryptLib alloc] generateRandomIV16]] encoding:NSUTF8StringEncoding];
}
- (NSString *) encryptPlainTextRandomIVWithPlainText:(NSString *)plainText key:(NSString *)key {
CryptLib *crypt = [CryptLib alloc];
NSString *plain = [crypt generateRandomIV16];
plain = [plain stringByAppendingString:plainText];
return [[[crypt init] encrypt:[plain dataUsingEncoding:NSUTF8StringEncoding] key:[crypt sha256:key length:32] iv:[crypt generateRandomIV16]] base64EncodedStringWithOptions:0];
}
- (NSString *) decryptCipherTextRandomIVWithCipherText:(NSString *)cipherText key:(NSString *)key {
CryptLib *crypt = [CryptLib alloc];
NSString *plain = [[NSString alloc] initWithData:[crypt decrypt:[[NSData alloc] initWithBase64EncodedString:cipherText options:NSDataBase64DecodingIgnoreUnknownCharacters] key:[crypt sha256:key length:32] iv:[crypt generateRandomIV16]] encoding:NSUTF8StringEncoding];
return [plain substringFromIndex:16];
}
//this function is no longer used in encryption / decryption
- (NSString *)md5:(NSString *) input
{
const char *cStr = [input UTF8String];
unsigned char digest[16];
CC_MD5( cStr, (uint32_t)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;
}
- (NSString*)generateRandomIV:(size_t)length {
// Since the length of Base64 hash is = (3/4) x (length of input string) we can work out input length required to
// generate 32byte hash is 24 bytes long. Note: Base64 may pad end with one, two or no '=' chars if not divisible.
// Therefore we don't care the generated string will be too long, just trim it down before returning.
NSMutableData *data = [NSMutableData dataWithLength:length];
int result = SecRandomCopyBytes(NULL, length, data.mutableBytes);
NSAssert(result == 0, #"Error generating random bytes: %d", errno);
NSString *base64EncodedData = [[data base64EncodedStringWithOptions:0] substringToIndex:length];
return base64EncodedData;
}
- (NSString*)generateRandomIV16 {
// Since the length of Base64 hash is = (3/4) x (length of input string) we can work out input length required to
// generate 32byte hash is 24 bytes long. Note: Base64 may pad end with one, two or no '=' chars if not divisible.
// Therefore we don't care the generated string will be too long, just trim it down before returning.
NSMutableData *data = [NSMutableData dataWithLength:16];
int result = SecRandomCopyBytes(NULL, 16, data.mutableBytes);
NSAssert(result == 0, #"Error generating random bytes: %d", errno);
NSString *base64EncodedData = [[data base64EncodedStringWithOptions:0] substringToIndex:16];
return base64EncodedData;
}
/**
* This function computes the SHA256 hash of input string
* #param key input text whose SHA256 hash has to be computed
* #param length length of the text to be returned
* #return returns SHA256 hash of input text
*/
- (NSString*) sha256:(NSString *)key length:(NSInteger) length{
const char *s=[key cStringUsingEncoding:NSASCIIStringEncoding];
NSData *keyData=[NSData dataWithBytes:s length:strlen(s)];
uint8_t digest[CC_SHA256_DIGEST_LENGTH]={0};
CC_SHA256(keyData.bytes, (CC_LONG)keyData.length, digest);
NSData *out=[NSData dataWithBytes:digest length:CC_SHA256_DIGEST_LENGTH];
NSString *hash=[out debugDescription];
hash = [hash stringByReplacingOccurrencesOfString:#" " withString:#""];
hash = [hash stringByReplacingOccurrencesOfString:#"<" withString:#""];
hash = [hash stringByReplacingOccurrencesOfString:#">" withString:#""];
if(length > [hash length])
{
return hash;
}
else
{
return [hash substringToIndex:length];
}
}
#end
and
#import <CommonCrypto/CommonDigest.h>
#import <CommonCrypto/CommonCryptor.h>
#import <Foundation/Foundation.h>
#interface CryptLib : NSObject
- (NSData *)encrypt:(NSData *)plainText key:(NSString *)key iv:(NSString *)iv;
- (NSData *)decrypt:(NSData *)encryptedText key:(NSString *)key iv:(NSString *)iv;
- (NSData *)generateRandomIV:(size_t)length;
- (NSString *) md5:(NSString *) input;
- (NSString *) sha256:(NSString *)key length:(NSInteger) length;
- (NSString *) encryptPlainText:(NSString *)plainText key:(NSString *)key iv:(NSString *)iv;
- (NSString *) decryptCipherText:(NSString *)cipherText key:(NSString *)key iv:(NSString *)iv;
- (NSString *) encryptPlainTextRandomIVWithPlainText:(NSString *)plainText key:(NSString *)key;
- (NSString *) decryptCipherTextRandomIVWithCipherText:(NSString *)cipherText key:(NSString *)key;
#end
My code in my app:
let decryptedString = cryptLib.decryptCipherTextRandomIV(withCipherText: stringValue, key: key)
viewModel.decode = decryptedString
viewModel.showImmunizationImformation.accept(())
i try to handle error but not success:
do {
let decryptedString = try? cryptLib.decryptCipherTextRandomIV(withCipherText: stringValue, key: key)
viewModel.decode = decryptedString
viewModel.showImmunizationImformation.accept(())
} catch {
print("error")
return
}