I have to set NSHTTPCookie such that it expiry is set to Session. I used the following code to set properties of that cookie.
NSMutableDictionary *cookieProperties = [NSMutableDictionary dictionary];
[cookieProperties setObject:@"mycookiename" forKey:NSHTTPCookieName];
[cookieProperties setObject:@"mycookievalue" forKey:NSHTTPCookieValue];
[cookieProperties setObject:[NSNumber numberWithBool:TRUE] forKey:NSHTTPCookieSecure];
[cookieProperties setObject:@"com.mydomain" forKey:NSHTTPCookieDomain];
[cookieProperties setObject:@"com.mydomain" forKey:NSHTTPCookieOriginURL];
[cookieProperties setObject:@"/" forKey:NSHTTPCookiePath];
[cookieProperties setObject:@"0" forKey:NSHTTPCookieVersion];
NSHTTPCookie *cookie = [NSHTTPCookie cookieWithProperties:cookieProperties];
[[NSHTTPCookieStorage sharedHTTPCookieStorage] setCookie:cookie];
However both of the above properties set the expiry to 1 Jan 2001 02:00:00 GMT+2 rather than setting the expiry to Session