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NSData+Seal.m
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NSData+Seal.m
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//
// NSData+Seal.m
// ExampleApp
//
// Created by Jakob Jensen on 09/06/14.
//
//
#import "NSData+Seal.h"
#import <CommonCrypto/CommonCryptor.h>
#define kSealTokenSize 16
@implementation NSData (Seal)
- (NSData *)sealWithPublicKey:(SecKeyRef)publicKey
{
uint8_t iv[kSealTokenSize];
arc4random_buf(&iv, kSealTokenSize);
size_t tokenBytesLength = 256;
uint8_t *tokenBytes = (uint8_t *)malloc(sizeof(uint8_t) * tokenBytesLength);
SecKeyEncrypt(publicKey,
kSecPaddingPKCS1,
iv,
kSealTokenSize,
tokenBytes,
&tokenBytesLength);
NSData *tokenData = [NSData dataWithBytes:tokenBytes length:tokenBytesLength];
free(tokenBytes);
NSString *token = [tokenData base64EncodedStringWithOptions:0];
size_t usedBuffer;
size_t bufferSize = self.length + kCCKeySizeMinRC4;
void *buffer = malloc(bufferSize);
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
kCCAlgorithmRC4,
kCCModeRC4,
iv,
kSealTokenSize,
NULL,
self.bytes,
self.length,
buffer,
bufferSize,
&usedBuffer);
if (cryptStatus != kCCSuccess) {
free(buffer);
return nil;
}
NSData *payloadData = [NSData dataWithBytes:buffer length:usedBuffer];
free(buffer);
NSString *payload = [payloadData base64EncodedStringWithOptions:0];
NSMutableDictionary *json = [NSMutableDictionary new];
json[@"token"] = token;
json[@"payload"] = payload;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:json options:0 error:nil];
[json release];
return jsonData;
}
- (NSData *)openWithPrivateKey:(SecKeyRef)privateKey
{
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:self options:0 error:nil];
NSString *token = json[@"token"];
NSString *payload = json[@"payload"];
if (!token || !payload) return nil;
NSData *tokenData = [[NSData alloc] initWithBase64EncodedString:token options:0];
NSData *payloadData = [[NSData alloc] initWithBase64EncodedString:payload options:0];
size_t tokenBytesLength = kSealTokenSize;
uint8_t *tokenBytes = (uint8_t *)malloc(sizeof(uint8_t) * tokenBytesLength);
SecKeyDecrypt(privateKey,
kSecPaddingPKCS1,
tokenData.bytes,
tokenData.length,
tokenBytes,
&tokenBytesLength);
[tokenData release];
size_t usedBuffer;
size_t bufferSize = payloadData.length + kCCKeySizeMinRC4;
void *buffer = malloc(bufferSize);
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
kCCAlgorithmRC4,
kCCModeRC4,
tokenBytes,
tokenBytesLength,
NULL,
payloadData.bytes,
payloadData.length,
buffer,
bufferSize,
&usedBuffer);
free(tokenBytes);
[payloadData release];
if (cryptStatus != kCCSuccess) {
free(buffer);
return nil;
}
NSData *unsealedData = [NSData dataWithBytes:buffer length:usedBuffer];
free(buffer);
return unsealedData;
}
- (SecKeyRef)publicKeyRef
{
SecCertificateRef cert = SecCertificateCreateWithData(NULL, (__bridge CFDataRef)self);
SecKeyRef key = NULL;
SecTrustRef trust = NULL;
SecPolicyRef policy = NULL;
if (cert != NULL) {
policy = SecPolicyCreateBasicX509();
if (policy) {
if (SecTrustCreateWithCertificates((CFTypeRef)cert, policy, &trust) == noErr) {
SecTrustResultType result;
if (SecTrustEvaluate(trust, &result) == noErr) {
key = SecTrustCopyPublicKey(trust);
}
}
}
}
if (policy) CFRelease(policy);
if (trust) CFRelease(trust);
if (cert) CFRelease(cert);
return key;
}
- (SecKeyRef)privateKeyRefWithPassword:(NSString *)password
{
NSMutableDictionary * options = [[NSMutableDictionary alloc] init];
SecKeyRef privateKeyRef = NULL;
[options setObject:password forKey:(__bridge id)kSecImportExportPassphrase];
CFArrayRef items = NULL;
OSStatus securityError = SecPKCS12Import((__bridge CFDataRef)self, (CFDictionaryRef)CFBridgingRelease(options), &items);
if (securityError == noErr && CFArrayGetCount(items) > 0) {
CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
SecIdentityRef identityApp = (SecIdentityRef)CFDictionaryGetValue(identityDict, kSecImportItemIdentity);
securityError = SecIdentityCopyPrivateKey(identityApp, &privateKeyRef);
if (securityError != noErr) {
privateKeyRef = NULL;
}
}
CFRelease(items);
return privateKeyRef;
}
@end