Synchonous SSL certificate handling on iPhone

问题:

I was wondering if anyone can help me understand how to add SSL certificate handling to synchronous connections to a https service.

I know how to do this with asynchronous connections but not synchronous.

                NSString *URLpath = @"https://mydomain.com/";
    NSURL *myURL = [[NSURL alloc] initWithString:URLpath];
    NSMutableURLRequest *myURLRequest = [NSMutableURLRequest requestWithURL:myURL cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:60];
    [myURL release];
    [myURLRequest setHTTPMethod:@"POST"];

    NSString *httpBodystr = @"setting1=1";
    [myURLRequest setHTTPBody:[httpBodystr dataUsingEncoding:NSUTF8StringEncoding]];

    NSHTTPURLResponse* myURLResponse; 
    NSError* myError;
    NSData* myDataResult = [NSURLConnection sendSynchronousRequest:myURLRequest returningResponse:&myURLResponse error:&myError];

            //I guess I am meant to put some SSL handling code here

Thank you.

回答1:

Using the static sendSynchronousRequest function is not posible, but i found an alternative.

First of all NSURLConnectionDataDelegate object like this one

FailCertificateDelegate.h

@interface FailCertificateDelegate : NSObject <NSURLConnectionDataDelegate>
   @property(atomic,retain)NSCondition *downloaded;
   @property(nonatomic,retain)NSData *dataDownloaded;
   -(NSData *)getData;
@end

FailCertificateDelegate.m

#import "FailCertificateDelegate.h"

@implementation FailCertificateDelegate
@synthesize dataDownloaded,downloaded;
-(id)init{
    self = [super init];
    if (self){
        dataDownloaded=nil;
        downloaded=[[NSCondition alloc] init];   
    }
    return self;
}


- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:    (NSURLProtectionSpace *)protectionSpace {
    NSLog(@"canAuthenticateAgainstProtectionSpace:");
    return [protectionSpace.authenticationMethod         isEqualToString:NSURLAuthenticationMethodServerTrust];
}


- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:    (NSURLAuthenticationChallenge *)challenge {
     NSLog(@"didReceiveAuthenticationChallenge:");
    [challenge.sender useCredential:[NSURLCredential     credentialForTrust:challenge.protectionSpace.serverTrust]     forAuthenticationChallenge:challenge];
}


- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    [downloaded signal]; 
    [downloaded unlock];
    self.hasFinnishLoading = YES; 
} 
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
    [dataDownloaded appendData:data];
    [downloaded lock]; 
} 

-(NSData *)getData{
    if (!self.hasFinnishLoading){
        [downloaded lock]; 
        [downloaded wait]; 
        [downloaded unlock]; 
    } 

    return dataDownloaded; 
}

@end

And for use it

FailCertificateDelegate *fcd=[[FailCertificateDelegate alloc] init];
NSURLConnection *c=[[NSURLConnection alloc] initWithRequest:request delegate:fcd startImmediately:NO];
[c setDelegateQueue:[[NSOperationQueue alloc] init]];
[c start];    
NSData *d=[fcd getData];

Now you will have all benefits of have an async use of nsurlconnection and benefits of a simple sync connection, the thread will be blocked until you download all data on the delegate, but you could improve it adding some error control on FailCertificateDelegate class

EDIT: fix for big data. based on Nikolay DS comment. Thanks a lot

回答2:

I had a similar issue. In my case i had an a-synchronous connection working with ssl as required using the two delegate methods that allowed me to accept any certificate:

- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace {
    return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
}

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
    [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];
}

But i was stuck on doing the same in a synchronous manner. I searched the web until i found your post and unfortunately another stackoverflow post where it is hinted that you cannot perform synch calls on NSURLConnection and work with ssl (because of the lack of a delegate to handle the ssl authentication process). What i ended up doing is getting ASIHTTPRequest and using that. It was painless to do and took me about an hour to set up and its working perfectly. here is how i use it.

+ (NSString *) getSynchronously:(NSDictionary *)parameters {
    NSURL *url = [NSURL URLWithString:@"https://localhost:8443/MyApp/";
    ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
    NSString *parameterJSONString = [parameters JSONRepresentation];
    [request appendPostString:parameterJSONString];
    [request addRequestHeader:@"User-Agent" value:@"MyAgent"];
    request.timeOutSeconds = CONNECTION_TIME_OUT_INTERVAL;
    [request setValidatesSecureCertificate:NO];
    [request startSynchronous];

    NSString *responseString = [request responseString];
    if (request.error) {
        NSLog(@"Server connection failed: %@", [request.error localizedDescription]);
    } else {
        NSLog(@"Server response: %@", responseString);
    }

    return responseString;
}

The important part of course is the

[request setValidatesSecureCertificate:NO];

---

Another alternative for you is to handle the download in another thread with an a-synch connection using the two methods above and block the thread from which you want the synch connection until the request is complete

回答3:

Im close to finding the solution for this with the code below. This works but often crashes probably because I am doing something wrong in the way I code this and I don't have a strong understanding of the methods used. But if anyone has any suggestions on how to improve this than please post.

Just after the line:

NSError* myError;

and just before the line:

NSData* myDataResult = [NSURLConnection sendSynchronousRequest:myURLRequest       
returningResponse:&myURLResponse error:&myError];

add:

    int failureCount = 0;
    NSURLProtectionSpace *protectionSpace = [[NSURLProtectionSpace alloc]      
    initWithHost:@"mydomain.com" port:443 protocol:@"https"  realm:nil  
    authenticationMethod:NSURLAuthenticationMethodServerTrust];

    NSURLResponse *response = [[NSURLResponse alloc] initWithURL:myURL MIMEType:@"text/html" 
    expectedContentLength:-1 textEncodingName:nil]; 

    NSURLAuthenticationChallenge *challange = [[NSURLAuthenticationChallenge alloc] 
    initWithProtectionSpace:protectionSpace proposedCredential:[NSURLCredential 
    credentialForTrust:protectionSpace.serverTrust] previousFailureCount:failureCount 
    failureResponse:response error:myError sender:nil];