Implemented NTLM auth support. Replaced deprecated auth challenge methods from `NSURLConnectionDelegate`. Replaces #711.

- added `username` and `password` properties on `SDWebImageDownloader`
- added `shouldUseCredentialStorage` and `credential` properties on `SDWebImageDownloaderOperation`
- `SDWebImageDownloaderOperation` conforms to `NSURLConnectionDataDelegate` (it used to implement the methods, but didn't stated the protocol in the declaration)
- removed deprecated methods: `- connection:canAuthenticateAgainstProtectionSpace:` and `- connection:didReceiveAuthenticationChallenge:` with `- connectionShouldUseCredentialStorage:` and `- connection:willSendRequestForAuthenticationChallenge:`
- updated demo project to download one image the requires HTTP auth

Examples/SDWebImage Demo/MasterViewController.m

@@ -29,7 +29,14 @@
                                                                                 style:UIBarButtonItemStylePlain
                                                                                target:self
                                                                                action:@selector(flushCache)];
+        
+        // HTTP NTLM auth example
+        // Add your NTLM image url to the array below and replace the credentials
+        [SDWebImageManager sharedManager].imageDownloader.username = @"httpwatch";
+        [SDWebImageManager sharedManager].imageDownloader.password = @"httpwatch01";
+        
         _objects = [NSArray arrayWithObjects:
+                    @"http://www.httpwatch.com/httpgallery/authentication/authenticatedimage/default.aspx?0.35786508303135633",     // requires HTTP auth, used to demo the NTLM auth
                     @"http://assets.sbnation.com/assets/2512203/dogflops.gif",
                     @"http://www.ioncannon.net/wp-content/uploads/2011/06/test2.webp",
                     @"http://www.ioncannon.net/wp-content/uploads/2011/06/test9.webp",

SDWebImage/SDWebImageDownloader.h

@@ -97,8 +97,23 @@ typedef void(^SDWebImageDownloaderCompletedBlock)(UIImage *image, NSData *data,
  */
 @property (assign, nonatomic) SDWebImageDownloaderExecutionOrder executionOrder;
 
+/**
+ *  Singleton method, returns the shared instance
+ *
+ *  @return global shared instance of downloader class
+ */
 + (SDWebImageDownloader *)sharedDownloader;
 
+/**
+ * Set username
+ */
+@property (strong, nonatomic) NSString *username;
+
+/**
+ * Set password
+ */
+@property (strong, nonatomic) NSString *password;
+
 /**
  * Set filter to pick headers for downloading image HTTP request.
  *

SDWebImage/SDWebImageDownloader.m

@@ -153,6 +153,10 @@ static NSString *const kCompletedCallbackKey = @"completed";
                                                                      [sself removeCallbacksForURL:url];
                                                                  }];
         
+        if (wself.username && wself.password) {
+            operation.credential = [NSURLCredential credentialWithUser:wself.username password:wself.password persistence:NSURLCredentialPersistenceForSession];
+        }
+        
         if (options & SDWebImageDownloaderHighPriority) {
             operation.queuePriority = NSOperationQueuePriorityHigh;
         } else if (options & SDWebImageDownloaderLowPriority) {

SDWebImage/SDWebImageDownloaderOperation.h

@@ -12,7 +12,28 @@
 
 @interface SDWebImageDownloaderOperation : NSOperation <SDWebImageOperation>
 
+/**
+ * The request used by the operation's connection.
+ */
 @property (strong, nonatomic, readonly) NSURLRequest *request;
+
+/**
+ * Whether the URL connection should consult the credential storage for authenticating the connection. `YES` by default.
+ *
+ * This is the value that is returned in the `NSURLConnectionDelegate` method `-connectionShouldUseCredentialStorage:`.
+ */
+@property (nonatomic, assign) BOOL shouldUseCredentialStorage;
+
+/**
+ * The credential used for authentication challenges in `-connection:didReceiveAuthenticationChallenge:`.
+ *
+ * This will be overridden by any shared credentials that exist for the username or password of the request URL, if present.
+ */
+@property (nonatomic, strong) NSURLCredential *credential;
+
+/**
+ * The SDWebImageDownloaderOptions for the receiver.
+ */
 @property (assign, nonatomic, readonly) SDWebImageDownloaderOptions options;
 
 /**

SDWebImage/SDWebImageDownloaderOperation.m

@@ -12,7 +12,7 @@
 #import <ImageIO/ImageIO.h>
 #import "SDWebImageManager.h"
 
-@interface SDWebImageDownloaderOperation () {
+@interface SDWebImageDownloaderOperation () <NSURLConnectionDataDelegate> {
     BOOL _executing;
     BOOL _finished;
 }
@@ -46,6 +46,7 @@
 - (id)initWithRequest:(NSURLRequest *)request options:(SDWebImageDownloaderOptions)options progress:(void (^)(NSInteger, NSInteger))progressBlock completed:(void (^)(UIImage *, NSData *, NSError *, BOOL))completedBlock cancelled:(void (^)())cancelBlock {
     if ((self = [super init])) {
         _request = request;
+        _shouldUseCredentialStorage = YES;
         _options = options;
         _progressBlock = [progressBlock copy];
         _completedBlock = [completedBlock copy];
@@ -404,18 +405,25 @@
     return self.options & SDWebImageDownloaderContinueInBackground;
 }
 
-- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace {
-    return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
+- (BOOL)connectionShouldUseCredentialStorage:(NSURLConnection __unused *)connection {
+    return self.shouldUseCredentialStorage;
 }
 
-- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
-    BOOL trustAllCertificates = (self.options & SDWebImageDownloaderAllowInvalidSSLCertificates);
-    if (trustAllCertificates && [challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]) {
-        [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust]
-             forAuthenticationChallenge:challenge];
+- (void)connection:(NSURLConnection *)connection willSendRequestForAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge{
+    if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]) {
+        NSURLCredential *credential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];
+        [[challenge sender] useCredential:credential forAuthenticationChallenge:challenge];
+    } else {
+        if ([challenge previousFailureCount] == 0) {
+            if (self.credential) {
+                [[challenge sender] useCredential:self.credential forAuthenticationChallenge:challenge];
+            } else {
+                [[challenge sender] continueWithoutCredentialForAuthenticationChallenge:challenge];
+            }
+        } else {
+            [[challenge sender] continueWithoutCredentialForAuthenticationChallenge:challenge];
+        }
     }
-
-    [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
 }
 
 @end