Sign OAuth Requests

OAuthRequestSigner.m

#import "OAuthRequestSigner.h"
#import <CommonCrypto/CommonCrypto.h>

@implementation OAuthRequestSigner

+(void)signRequestForOAuthRequest:(NSMutableURLRequest *)request
              withOAuthParameters:(NSDictionary *)oAuthParameters
                   consumerSecret:(NSString *)consumerSecret
                      tokenSecret:(NSString *)tokenSecret
{
    
    NSMutableDictionary *unsortedParameters = [NSMutableDictionary dictionaryWithDictionary:oAuthParameters];
    
    NSMutableArray *parameters = [[NSMutableArray alloc] init];
    
    NSURLComponents *queryComponents = [NSURLComponents new];
    queryComponents.query = [[request URL] query];
    [queryComponents.queryItems enumerateObjectsUsingBlock:^(NSURLQueryItem *qi, NSUInteger idx, BOOL *stop) {
        NSLog(@"--> %@=%@",qi.name,qi.value);
        [unsortedParameters addEntriesFromDictionary:@{qi.name:qi.value}];
    }];
    
    NSURLComponents *bodyComponents = [NSURLComponents new];
    bodyComponents.query = [[NSString alloc] initWithData:[request HTTPBody] encoding:NSUTF8StringEncoding];
    [bodyComponents.queryItems enumerateObjectsUsingBlock:^(NSURLQueryItem *qi, NSUInteger idx, BOOL *stop) {
        NSLog(@"--> %@=%@",qi.name,qi.value);
        [unsortedParameters addEntriesFromDictionary:@{qi.name:qi.value}];
    }];

    NSArray *sortedHeaderKeys = [[unsortedParameters allKeys] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
    [sortedHeaderKeys enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        NSString *parameter = [unsortedParameters objectForKey:obj];
        if (!parameter) {
            [parameters addObject:[NSString stringWithFormat:@"%@=true", obj]];
            return;
        }
        [parameters addObject:[NSString stringWithFormat:@"%@=%@", obj, parameter]];
    }];

    NSString *urlString = [[request URL] absoluteString];
    if ([[request URL] query]) {
        urlString = [[urlString stringByReplacingOccurrencesOfString:[[request URL] query] withString:@""] stringByReplacingOccurrencesOfString:@"?" withString:@""];
    }

    NSMutableString *baseString = [[NSMutableString alloc] init];
    [baseString appendString:[[request HTTPMethod] uppercaseString]];
    [baseString appendString:@"&"];
    [baseString appendString:[GPTwitterPublisher URLEncodeStringFromString:urlString]];
    [baseString appendString:@"&"];
    [baseString appendString:[GPTwitterPublisher URLEncodeStringFromString:[parameters componentsJoinedByString:@"&"]]];
    
    NSString *signingKey = [NSString stringWithFormat:@"%@&%@",
                            consumerSecret,
                            tokenSecret];
    
    const char *key = [signingKey cStringUsingEncoding:NSASCIIStringEncoding];
    const char *data = [baseString cStringUsingEncoding:NSASCIIStringEncoding];
    unsigned char mac[CC_SHA1_DIGEST_LENGTH];
    
    CCHmac(kCCHmacAlgSHA1, key, strlen(key), data, strlen(data), mac);
    NSData *hmacData = [NSData dataWithBytes:mac length:sizeof(mac)];
    NSString *signature = [hmacData base64EncodedStringWithOptions:0];
    
    NSMutableDictionary *authorisationHeader = [oAuthParameters mutableCopy];
    [authorisationHeader setObject:[GPTwitterPublisher URLEncodeStringFromString:signature] forKey:@"oauth_signature"];
    
    NSMutableArray *oAuthHeaderFields = [NSMutableArray array];
    [[[authorisationHeader allKeys] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)] enumerateObjectsUsingBlock:^(id key, NSUInteger idx, BOOL *stop) {
        NSString *param = [NSString stringWithFormat:@"%@=\"%@\"", [GPTwitterPublisher URLEncodeStringFromString:key], authorisationHeader[key]];
        [oAuthHeaderFields addObject:param];
    }];
    
    [request setValue:[NSString stringWithFormat:@"OAuth %@", [oAuthHeaderFields componentsJoinedByString:@","]] forHTTPHeaderField:@"Authorization"];
}

@end