Custom URL Protocol to Globally Modify User Agent for URL Requests

ios-custom-url-protocol

@interface CustomBrowserURLProtocol : NSURLProtocol

@end

@interface CustomBrowserURLProtocol ()
@property (nonatomic, strong) NSURLConnection *connection;

@end

@implementation CustomBrowserURLProtocol

+ (BOOL)canInitWithRequest:(NSURLRequest *)request
{
    if ([NSURLProtocol propertyForKey:@"UserAgentSet" inRequest:request] != nil)
        return NO;
    
    return YES;
}

+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request
{
    return request;
}

- (void)startLoading
{
    NSMutableURLRequest *newRequest = [self.request mutableCopy];
    
    
    NSBundle *bundle = [NSBundle bundleForClass:[self class]];
    
    
    NSString *appName = [bundle objectForInfoDictionaryKey:@"CFBundleDisplayName"];
    NSString *bundleIdentifier = [bundle objectForInfoDictionaryKey:@"CFBundleIdentifier"];
    NSString *publicVersionNumber = [bundle objectForInfoDictionaryKey:@"CFBundleShortVersionString"];
    NSString *privateBuildNumber = [bundle objectForInfoDictionaryKey:@"CFBundleVersion"];
    NSString *osVersion = [[UIDevice currentDevice] systemVersion];

    NSString *updatedUserAgent = [NSString stringWithFormat:@"%@ %@/%@ (iOS %@; %@; build:%@)", [[newRequest allHTTPHeaderFields] objectForKey:@"User-Agent"], appName, publicVersionNumber, osVersion, bundleIdentifier, privateBuildNumber];
    
    [newRequest setValue:updatedUserAgent forHTTPHeaderField:@"User-Agent"];
    
    [NSURLProtocol setProperty:@YES forKey:@"UserAgentSet" inRequest:newRequest];
    
    self.connection = [NSURLConnection connectionWithRequest:newRequest delegate:self];
}

- (void)stopLoading
{
    [self.connection cancel];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.client URLProtocol:self didLoadData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [self.client URLProtocol:self didFailWithError:error];
    self.connection = nil;
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageAllowed];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    [self.client URLProtocolDidFinishLoading:self];
    self.connection = nil;
}

@end