Support client side encryption via SEGCrypto protocol (#592)

* Adding SEGStorage and SEGCrypto classes

* Adding SEGUserDefaultsStorage

* Route all disk access through SEGStorage classes and expose SEGCrypto as
part of SEGAnalyticsConfiguration

* Run pod install again

* Fix anonymousId loading. Removing no longer used anonymousIdURL

* Removing unused SEGAnalyticsURLForFilename

* Adding CryptoTest, FileStorageTest and UserDefaultsStorageTest from redux branch

* Adding changes to Podfile

Analytics.podspec

@@ -17,5 +17,7 @@ Pod::Spec.new do |s|
   s.ios.deployment_target = '7.0'
   s.tvos.deployment_target = '9.0'
 
+  s.framework = 'Security'
+
   s.source_files = 'Analytics/Classes/**/*'
 end

Analytics/Classes/Crypto/SEGAES256Crypto.h

@@ -0,0 +1,23 @@
+//
+//  SEGAES256Crypto.h
+//  Analytics
+//
+//  Copyright © 2016 Segment. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+#import "SEGCrypto.h"
+
+@interface SEGAES256Crypto : NSObject <SEGCrypto>
+
+@property (nonatomic, readonly, nonnull) NSString *password;
+@property (nonatomic, readonly, nonnull) NSData *salt;
+@property (nonatomic, readonly, nonnull) NSData *iv;
+
+- (instancetype _Nonnull)initWithPassword:(NSString * _Nonnull)password salt:(NSData * _Nonnull)salt iv:(NSData * _Nonnull)iv;
+// Convenient shorthand. Will randomly generate salt and iv.
+- (instancetype _Nonnull)initWithPassword:(NSString * _Nonnull)password;
+
++ (NSData * _Nonnull)randomDataOfLength:(size_t)length;
+
+@end

Analytics/Classes/Crypto/SEGAES256Crypto.m

@@ -0,0 +1,140 @@
+//
+//  SEGAES256Crypto.m
+//  Analytics
+//
+//  Copyright © 2016 Segment. All rights reserved.
+//
+
+
+#import <CommonCrypto/CommonCryptor.h>
+#import <CommonCrypto/CommonKeyDerivation.h>
+#import "SEGAES256Crypto.h"
+#import "SEGUtils.h"
+
+// Implementation courtesy of http://robnapier.net/aes-commoncrypto
+
+static NSString * const kRNCryptManagerErrorDomain = @"com.segment.crypto";
+
+static const CCAlgorithm kAlgorithm = kCCAlgorithmAES;
+static const NSUInteger kAlgorithmKeySize = kCCKeySizeAES256;
+static const NSUInteger kAlgorithmBlockSize = kCCBlockSizeAES128;
+static const NSUInteger kAlgorithmIVSize = kCCBlockSizeAES128;
+static const NSUInteger kPBKDFSaltSize = 8;
+static const NSUInteger kPBKDFRounds = 10000;  // ~80ms on an iPhone 4
+
+@implementation SEGAES256Crypto
+
+- (instancetype)initWithPassword:(NSString *)password salt:(NSData *)salt iv:(NSData * _Nonnull)iv {
+    if (self = [super init]) {
+        _password = password;
+        _salt = salt;
+        _iv = iv;
+    }
+    return self;
+}
+
+- (instancetype)initWithPassword:(NSString *)password {
+    NSData *iv = [SEGAES256Crypto randomDataOfLength:kAlgorithmIVSize];
+    NSData *salt = [SEGAES256Crypto randomDataOfLength:kPBKDFSaltSize];
+    return [self initWithPassword:password salt:salt iv:iv];
+}
+
+- (NSData *)aesKey {
+    return [[self class] AESKeyForPassword:self.password salt:self.salt];
+}
+
+- (NSData *)encrypt:(NSData *)data {
+    size_t outLength;
+    NSMutableData *cipherData = [NSMutableData dataWithLength:data.length + kAlgorithmBlockSize];
+
+    CCCryptorStatus
+    result = CCCrypt(kCCEncrypt, // operation
+                     kAlgorithm, // Algorithm
+                     kCCOptionPKCS7Padding, // options
+                     self.aesKey.bytes, // key
+                     self.aesKey.length, // keylength
+                     self.iv.bytes,// iv
+                     data.bytes, // dataIn
+                     data.length, // dataInLength,
+                     cipherData.mutableBytes, // dataOut
+                     cipherData.length, // dataOutAvailable
+                     &outLength); // dataOutMoved
+
+    if (result == kCCSuccess) {
+        cipherData.length = outLength;
+    } else {
+        NSError *error = [NSError errorWithDomain:kRNCryptManagerErrorDomain
+                                             code:result
+                                         userInfo:nil];
+        SEGLog(@"Unable to encrypt data", error);
+        return nil;
+    }
+    return cipherData;
+}
+
+- (NSData *)decrypt:(NSData *)data {
+    size_t outLength;
+    NSMutableData *decryptedData = [NSMutableData dataWithLength:data.length + kAlgorithmBlockSize];
+
+    CCCryptorStatus
+    result = CCCrypt(kCCDecrypt, // operation
+                     kAlgorithm, // Algorithm
+                     kCCOptionPKCS7Padding, // options
+                     self.aesKey.bytes, // key
+                     self.aesKey.length, // keylength
+                     self.iv.bytes,// iv
+                     data.bytes, // dataIn
+                     data.length, // dataInLength,
+                     decryptedData.mutableBytes, // dataOut
+                     decryptedData.length, // dataOutAvailable
+                     &outLength); // dataOutMoved
+
+    if (result == kCCSuccess) {
+        decryptedData.length = outLength;
+    } else {
+        NSError *error = [NSError errorWithDomain:kRNCryptManagerErrorDomain
+                                             code:result
+                                         userInfo:nil];
+        SEGLog(@"Unable to encrypt data", error);
+        return nil;
+    }
+    return decryptedData;
+}
+
++ (NSData *)randomDataOfLength:(size_t)length {
+    NSMutableData *data = [NSMutableData dataWithLength:length];
+
+    int result = SecRandomCopyBytes(kSecRandomDefault,
+                                    length,
+                                    data.mutableBytes);
+    if (result != kCCSuccess) {
+        SEGLog(@"Unable to generate random bytes: %d", result);
+    }
+
+    return data;
+}
+
+// Replace this with a 10,000 hash calls if you don't have CCKeyDerivationPBKDF
++ (NSData *)AESKeyForPassword:(NSString *)password 
+                         salt:(NSData *)salt {
+    NSMutableData *derivedKey = [NSMutableData dataWithLength:kAlgorithmKeySize];
+
+    int result = CCKeyDerivationPBKDF(kCCPBKDF2,            // algorithm
+                                      password.UTF8String,  // password
+                                      [password lengthOfBytesUsingEncoding:NSUTF8StringEncoding],  // passwordLength
+                                      salt.bytes,           // salt
+                                      salt.length,          // saltLen
+                                      kCCPRFHmacAlgSHA1,    // PRF
+                                      kPBKDFRounds,         // rounds
+                                      derivedKey.mutableBytes, // derivedKey
+                                      derivedKey.length); // derivedKeyLen
+
+    // Do not log password here
+    if (result != kCCSuccess) {
+        SEGLog(@"Unable to create AES key for password: %d", result);
+    }
+
+    return derivedKey;
+}
+
+@end

Analytics/Classes/Crypto/SEGCrypto.h

@@ -0,0 +1,15 @@
+//
+//  SEGCrypto.h
+//  Analytics
+//
+//  Copyright © 2016 Segment. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@protocol SEGCrypto <NSObject>
+
+- (NSData * _Nullable)encrypt:(NSData * _Nonnull)data;
+- (NSData * _Nullable)decrypt:(NSData * _Nonnull)data;
+
+@end

Analytics/Classes/Internal/SEGAnalyticsUtils.h

@@ -1,6 +1,5 @@
 #import <Foundation/Foundation.h>
 
-NSURL *SEGAnalyticsURLForFilename(NSString *filename);
 NSString *GenerateUUIDString();
 
 // Date Utils

Analytics/Classes/Internal/SEGAnalyticsUtils.m

@@ -3,24 +3,6 @@
 
 static BOOL kAnalyticsLoggerShowLogs = NO;
 
-NSURL *SEGAnalyticsURLForFilename(NSString *filename)
-{
-    NSArray *paths = NSSearchPathForDirectoriesInDomains(
-        NSApplicationSupportDirectory, NSUserDomainMask, YES);
-    NSString *supportPath = [paths firstObject];
-    if (![[NSFileManager defaultManager] fileExistsAtPath:supportPath
-                                              isDirectory:NULL]) {
-        NSError *error = nil;
-        if (![[NSFileManager defaultManager] createDirectoryAtPath:supportPath
-                                       withIntermediateDirectories:YES
-                                                        attributes:nil
-                                                             error:&error]) {
-            SEGLog(@"error: %@", error.localizedDescription);
-        }
-    }
-    return [[NSURL alloc] initFileURLWithPath:[supportPath stringByAppendingPathComponent:filename]];
-}
-
 NSString *GenerateUUIDString()
 {
     CFUUIDRef theUUID = CFUUIDCreate(NULL);

Analytics/Classes/Internal/SEGFileStorage.h

@@ -0,0 +1,22 @@
+//
+//  SEGFileStorage.h
+//  Analytics
+//
+//  Copyright © 2016 Segment. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+#import "SEGStorage.h"
+
+@interface SEGFileStorage : NSObject <SEGStorage>
+
+@property (nonatomic, strong, nullable) id<SEGCrypto> crypto;
+
+- (instancetype _Nonnull)init;
+- (instancetype _Nonnull)initWithFolder:(NSURL * _Nonnull)folderURL crypto:(id<SEGCrypto> _Nullable)crypto;
+
+- (NSURL * _Nonnull)urlForKey:(NSString * _Nonnull)key;
+
++ (NSURL * _Nullable)applicationSupportDirectoryURL;
+
+@end