Sending a POST request from Cocoa to Tumblr

Question

This code snippet isn't working, I'm getting an "Authentication Failed." response from the server. Any ideas?

    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] 
                                    initWithURL:
                                    [NSURL URLWithString:@"http://www.tumblr.com/api/write"]];
    [request setHTTPMethod:@"POST"];
    [request addValue:_tumblrLogin forHTTPHeaderField:@"email"];
    [request addValue:_tumblrPassword forHTTPHeaderField:@"password"];
    [request addValue:@"regular" forHTTPHeaderField:@"type"];
    [request addValue:@"theTitle" forHTTPHeaderField:@"title"];
    [request addValue:@"theBody" forHTTPHeaderField:@"body"];

    NSLog(@"Tumblr Login:%@\nTumblr Password:%@", _tumblrLogin, _tumblrPassword);

    [NSURLConnection connectionWithRequest:request delegate:self];

    [request release];

Both _tumblrLogin and _tumblrPassword are run through stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding elsewhere in my code. My login email is of the form "[email protected]". It works just fine for logging in directly to tumblr, but I'm wondering if the "+" character is causing problems with the encoding? It's not being escaped. Should it be?

---

Thanks to Martin's suggestion, I'm now using CFURLCreateStringByAddingPercentEscapes to escape my login and password. I'm still having the same issue, though, my Authentication is failing.

Iinde

Can you tell me the working code reference available for Tumblr API? – Plagio

Answer 1

The problem is that you are not creating a proper HTTP POST request. A POST request requires a properly formatted multipart MIME-encoded body containing all the parameters you want to send to the server. You are trying to set the parameters as HTTP headers which won't work at all.

This code will do what you want, note especially the NSString categories that create a valid Multipart MIME string:

@interface NSString (MIMEAdditions)
+ (NSString*)MIMEBoundary;
+ (NSString*)multipartMIMEStringWithDictionary:(NSDictionary*)dict;
@end

@implementation NSString (MIMEAdditions)
//this returns a unique boundary which is used in constructing the multipart MIME body of the POST request
+ (NSString*)MIMEBoundary
{
    static NSString* MIMEBoundary = nil;
    if(!MIMEBoundary)
        MIMEBoundary = [[NSString alloc] initWithFormat:@"----_=_YourAppNameNoSpaces_%@_=_----",[[NSProcessInfo processInfo] globallyUniqueString]];
    return MIMEBoundary;
}
//this create a correctly structured multipart MIME body for the POST request from a dictionary
+ (NSString*)multipartMIMEStringWithDictionary:(NSDictionary*)dict 
{
    NSMutableString* result = [NSMutableString string];
    for (NSString* key in dict)
    {
        [result appendFormat:@"--%@\r\nContent-Disposition: form-data; name=\"%@\"\r\n\r\n%@\r\n",[NSString MIMEBoundary],key,[dict objectForKey:key]];
    }
    [result appendFormat:@"\r\n--%@--\r\n",[NSString MIMEBoundary]];
    return result;
}
@end


@implementation YourObject
- (void)postToTumblr
{
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] 
                                    initWithURL:
                                    [NSURL URLWithString:@"http://www.tumblr.com/api/write"]];
    [request setHTTPMethod:@"POST"];
    //tell the server to expect 8-bit encoded content as we're sending UTF-8 data, 
    //and UTF-8 is an 8-bit encoding
    [request addValue:@"8bit" forHTTPHeaderField:@"Content-Transfer-Encoding"];
    //set the content-type header to multipart MIME
    [request addValue: [NSString stringWithFormat:@"multipart/form-data; boundary=%@",[NSString MIMEBoundary]] forHTTPHeaderField: @"Content-Type"];

    //create a dictionary for all the fields you want to send in the POST request
    NSDictionary* postData = [NSDictionary dictionaryWithObjectsAndKeys:
                                 _tumblrLogin, @"email",
                                 _tumblrPassword, @"password",
                                 @"regular", @"type",
                                 @"theTitle", @"title",
                                 @"theBody", @"body",
                                 nil];
    //set the body of the POST request to the multipart MIME encoded dictionary
    [request setHTTPBody: [[NSString multipartMIMEStringWithDictionary: postData] dataUsingEncoding: NSUTF8StringEncoding]];
    NSLog(@"Tumblr Login:%@\nTumblr Password:%@", _tumblrLogin, _tumblrPassword);
    [NSURLConnection connectionWithRequest:request delegate:self];
    [request release];
}
@end

Articulator

Holy crap. I'd star this 10000x if I could. Thanks for your help. While I've got you on the hook, do you happen to have a link explaining the headerFields (why do you need to set the 8bit encoding) and the MIMEBoundary? – Iinde

You need to set 8-bit encoding because the body of the request is a blob of data encoded using UTF8 (using the -dataUsingEncoding: method of NSString and passing in NSUTF8StringEncoding). UTF8 is an 8 bit encoding, if it was interpreted as a 7-bit encoding (ASCII) data corruption would occur. Multipart MIME encoding allows you to create a string that contains separate sections. Each section is delineated by a constant string used as a boundary marker. The boundary string is completely arbitrary but must not be contained in the non-boundary content of the string. – Articulator

The Wikipedia article on MIME is probably useful: en.wikipedia.org/wiki/MIME#Multipart_messages – Articulator

Answer 2

As per the answers to this question, stringByAddingPercentEscapesUsingEncoding: doesn't perform a full escape encoding. For whatever reason, the CoreFoundation version of this method does, however:

[(NSString *) CFURLCreateStringByAddingPercentEscapes(NULL, 
    (CFStringRef)[[self mutableCopy] autorelease], NULL, 
    CFSTR("=,!$&'()*+;@?\n\"<>#\t :/"), kCFStringEncodingUTF8) autorelease];

You can also use NSMutableString's replaceOccurencesOfString:withString:options: method to do the replacement manually, but that method is more repetitive and verbose. (See here.)

Peseta

Thanks for this. I did use the CFURLCreate... per your suggestion, but it still isn't working. – Iinde