Update fronting to use country-specific Google domains.

// FREEBIE

src/Network/OWSCensorshipConfiguration.h

@@ -7,7 +7,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface OWSCensorshipConfiguration : NSObject
 
-- (NSString *)frontingHost;
+- (NSString *)frontingHost:(NSString *)e164PhonNumber;
 - (NSString *)reflectorHost;
 - (BOOL)isCensoredPhoneNumber:(NSString *)e164PhonNumber;
 

src/Network/OWSCensorshipConfiguration.m

@@ -6,14 +6,29 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-NSString *const OWSCensorshipConfigurationFrontingHost = @"https://google.com";
 NSString *const OWSCensorshipConfigurationReflectorHost = @"signal-reflector-meek.appspot.com";
 
 @implementation OWSCensorshipConfiguration
 
-- (NSString *)frontingHost
+- (NSString *)frontingHost:(NSString *)e164PhonNumber
 {
-    return OWSCensorshipConfigurationFrontingHost;
+    OWSAssert(e164PhonNumber.length > 0);
+    
+    NSString *domain = nil;
+    for (NSString *countryCode in self.censoredCountryCodes.allKeys) {
+        if ([e164PhonNumber hasPrefix:countryCode]) {
+            domain = self.censoredCountryCodes[countryCode];
+        }
+    }
+    
+    // Fronting should only be used for countries specified in censoredCountryCodes,
+    // all of which have a domain specified.
+    OWSAssert(domain);
+    if (!domain) {
+        domain = @"google.com";
+    }
+    
+    return [@"https://" stringByAppendingString:domain];
 }
 
 - (NSString *)reflectorHost
@@ -21,26 +36,31 @@ NSString *const OWSCensorshipConfigurationReflectorHost = @"signal-reflector-mee
     return OWSCensorshipConfigurationReflectorHost;
 }
 
-- (NSArray<NSString *> *)censoredCountryCodes
+- (NSDictionary<NSString *, NSString *> *)censoredCountryCodes
 {
-    // Reports of censorship in:
-    return @[
+    // Domain fronting should be used for the following countries.
+    //
+    // For each country, we should the appropriate google domain,
+    // per:  https://en.wikipedia.org/wiki/List_of_Google_domains
+    return @{
              // Egypt
-             @"+20",
+             @"+20": @"google.com.eg",
              // Cuba
-             @"+53",
+             @"+53": @"google.com.cu",
              // Oman
-             @"+968",
+             @"+968": @"google.com.om",
              // UAE
-             @"+971",
+             @"+971": @"google.com.ae",
              // Iran
-             @"+98",
-             ];
+             //
+             // There does not appear to be a specific Google domain for Iran.
+             @"+98": @"google.com",
+             };
 }
 
 - (BOOL)isCensoredPhoneNumber:(NSString *)e164PhonNumber
 {
-    for (NSString *countryCode in self.censoredCountryCodes) {
+    for (NSString *countryCode in self.censoredCountryCodes.allKeys) {
         if ([e164PhonNumber hasPrefix:countryCode]) {
             return YES;
         }

src/Network/OWSSignalService.m

@@ -69,8 +69,11 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (AFHTTPSessionManager *)reflectorHTTPSessionManager
 {
+    NSString *localNumber = [TSAccountManager localNumber];
+    OWSAssert(localNumber.length > 0);
+
     // Target fronting domain
-    NSURL *baseURL = [[NSURL alloc] initWithString:self.censorshipConfiguration.frontingHost];
+    NSURL *baseURL = [[NSURL alloc] initWithString:[self.censorshipConfiguration frontingHost:localNumber]];
     NSURLSessionConfiguration *sessionConf = NSURLSessionConfiguration.ephemeralSessionConfiguration;
     AFHTTPSessionManager *sessionManager =
         [[AFHTTPSessionManager alloc] initWithBaseURL:baseURL sessionConfiguration:sessionConf];

src/Util/Cryptography.m

@@ -10,7 +10,6 @@
 #import <CommonCrypto/CommonHMAC.h>
 
 #import "Cryptography.h"
-
 #import "NSData+Base64.h"
 
 #define HMAC256_KEY_LENGTH 32