Invalid signature: oauth_signature in iOS

[Anum Amin]

I am trying to produce oauth_signature to use **Fatsecret API**, but getting invalid signature error - can't figure out why. I tried to follow all steps mentioned for Signature value generation as accurately as possible.

For base64 encoding, I used QSStrings.h

 Steps I coded are as follows:

    - (void)viewDidLoad

    {

    NSTimeInterval intervalFloat = [[NSDate date] timeIntervalSince1970];

    int interval = (int) intervalFloat;

    NSLog(@"time interval: %d",interval);

    

    //for oauth_nonce random string

    NSString *randomString = [self genRandString]; //see definition below

    NSLog(@"%@",randomString);

    

    NSString *requestString = [NSString stringWithFormat:@"POST&http%3A%2F%2Fplatform.fatsecret.com%2Frest%2Fserver.api&format%3Djson%26method%3Dprofile.create%26oauth_consumer_key%3Db753c99ccxxxxxx%26oauth_nonce%3D%@%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D%d%26oauth_version%3D1.0",randomString,interval];

    NSString *secret = @"3959096c04xxxxxxxx&";

    

    NSString *encodedStr = [self hmacsha1:requestString secret:secret]; //see definition below

    NSLog(@"encodedStr: %@",encodedStr);

    

    NSString *encodedString = [self urlEncodeValue:encodedStr]; //see definition below

    NSLog(@"encodedString: %@",encodedString);

    

    NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://platform.fatsecret.com/rest/server.api?format=json&method=profile.create&oauth_consumer_key=b753c99ccxxxxxx&oauth_nonce=%@&oauth_signature=%@&oauth_signature_method=HMAC-SHA1&oauth_timestamp=%d&oauth_version=1.0",randomString, encodedString,interval]];

               

    _request = [ASIFormDataRequest requestWithURL:url];

    [_request setPostValue:@"json" forKey:@"format"];

    [_request setPostValue:@"profile.create" forKey:@"method"];

    [_request setPostValue:@"b753c99ccxxxxxx" forKey:@"oauth_consumer_key"];

    [_request setPostValue:randomString forKey:@"oauth_nonce"];

    [_request setPostValue:encodedString forKey:@"oauth_signature"];

    [_request setPostValue:@"HMAC-SHA1" forKey:@"oauth_signature_method"];

    [_request setPostValue:[NSNumber numberWithInt:interval] forKey:@"oauth_timestamp"];

    [_request setPostValue:@"1.0" forKey:@"oauth_version"];

    [_request setDelegate:self];

    _request.timeOutSeconds = 60.0; 

    [_request startAsynchronous];

    

    }

Definitions for methods I used in code above are as follows:

    - (NSString *)hmacsha1:(NSString *)data secret:(NSString *)key {

    

    const char *cKey  = [key cStringUsingEncoding:NSASCIIStringEncoding];

    const char *cData = [data cStringUsingEncoding:NSASCIIStringEncoding];

    

    unsigned char cHMAC[CC_SHA1_DIGEST_LENGTH];

    

    CCHmac(kCCHmacAlgSHA1, cKey, strlen(cKey), cData, strlen(cData), cHMAC);

    

    NSData *HMAC = [[NSData alloc] initWithBytes:cHMAC length:sizeof(cHMAC)];

    

    NSString *hash = [QSStrings encodeBase64WithData:HMAC];

    

    NSLog(@"Hash: %@", hash);  

    

    return hash;

    }

    NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

    -(NSString *) genRandString {

    //fixing length of 4 chars

    NSMutableString *randomString = [NSMutableString stringWithCapacity: 4];

    

    for (int i=0; i<4; i++) {

        [randomString appendFormat: @"%C", [letters characterAtIndex: arc4random() % [letters length]]];

    }

    

    return randomString;

    }

    - (NSString *)urlEncodeValue:(NSString *)str

    {

    NSMutableString * output = [NSMutableString string];

    const unsigned char * source = (const unsigned char *)[str UTF8String];

    int sourceLen = strlen((const char *)source);

    for (int i = 0; i < sourceLen; ++i) {

        const unsigned char thisChar = source[i];

        if (thisChar == ' '){

            [output appendString:@"+"];

        } else if (thisChar == '.' || thisChar == '-' || thisChar == '_' || thisChar == '~' || 

                   (thisChar >= 'a' && thisChar <= 'z') ||

                   (thisChar >= 'A' && thisChar <= 'Z') ||

                   (thisChar >= '0' && thisChar <= '9')) {

            [output appendFormat:@"%c", thisChar];

        } else {

            [output appendFormat:@"%%%02X", thisChar];

        }

    }

    return output;   

   

    }

Please anybody help me out. Thanks :(

[Parker Wightman]

I built a library that does all this for you that might be of use to you: https://github.com/mysterioustrousers/FatSecretKit

This is too much code to wrap one's head around in a forum like this, sorry I can't be of more help :-(