Question

I am developing an application for the DropBox API and cannot for the life of me find any information about what’s meant to go into the “signature” of the first token request during authentication.

Does anyone else know?

Answer 1

If it is OAuth then the signature is the combination of

• OAuthVersion
• OAuthNonce
• Timestamp
• ConsumerKey
• SignatureMethod (e.g. HMACSHA1)
• Any parameters you wish to send along
• HTTP method

For example here is some code that does it

    /// <summary>
    /// Generate the signature base that is used to produce the signature
    /// </summary>
    /// <param name="url">The full url that needs to be signed including its non OAuth url parameters</param>
    /// <param name="consumerKey">The consumer key</param>        
    /// <param name="token">The token, if available. If not available pass null or an empty string</param>
    /// <param name="tokenSecret">The token secret, if available. If not available pass null or an empty string</param>
    /// <param name="httpMethod">The http method used. Must be a valid HTTP method verb (POST,GET,PUT, etc)</param>
    /// <param name="signatureType">The signature type. To use the default values use <see cref="OAuthBase.SignatureTypes">OAuthBase.SignatureTypes</see>.</param>
    /// <returns>The signature base</returns>
    public static string GenerateSignatureBase(Uri url, string consumerKey, string token, string tokenSecret, string httpMethod, string timeStamp, string nonce, string signatureType, SortedList<String, String> customParameters, out string normalizedUrl, out string normalizedRequestParameters)
    {
        if (token == null)
        {
            token = string.Empty;
        }

        if (tokenSecret == null)
        {
            tokenSecret = string.Empty;
        }

        if (string.IsNullOrEmpty(consumerKey))
        {
            throw new ArgumentNullException("consumerKey");
        }

        if (string.IsNullOrEmpty(httpMethod))
        {
            throw new ArgumentNullException("httpMethod");
        }

        if (string.IsNullOrEmpty(signatureType))
        {
            throw new ArgumentNullException("signatureType");
        }

        normalizedUrl = null;
        normalizedRequestParameters = null;

        List<QueryParameter> parameters = GetQueryParameters(url.Query);
        parameters.Add(new QueryParameter(OAuthVersionKey, OAuthVersion));
        parameters.Add(new QueryParameter(OAuthNonceKey, nonce));
        parameters.Add(new QueryParameter(OAuthTimestampKey, timeStamp));
        parameters.Add(new QueryParameter(OAuthSignatureMethodKey, signatureType));
        parameters.Add(new QueryParameter(OAuthConsumerKeyKey, consumerKey));

        foreach (String key in customParameters.Keys)
        {
            parameters.Add(new QueryParameter(key, UrlEncode(customParameters[key])));
        }


        if (!string.IsNullOrEmpty(token))
        {
            parameters.Add(new QueryParameter(OAuthTokenKey, token));
        }

        parameters.Sort(new QueryParameterComparer());

        normalizedUrl = string.Format("{0}://{1}", url.Scheme, url.Host);
        if (!((url.Scheme == "http" && url.Port == 80) || (url.Scheme == "https" && url.Port == 443)))
        {
            normalizedUrl += ":" + url.Port;
        }
        normalizedUrl += url.AbsolutePath;
        normalizedRequestParameters = NormalizeRequestParameters(parameters);

        StringBuilder signatureBase = new StringBuilder();
        signatureBase.AppendFormat("{0}&", httpMethod.ToUpper());
        signatureBase.AppendFormat("{0}&", UrlEncode(normalizedUrl));
        signatureBase.AppendFormat("{0}", UrlEncode(normalizedRequestParameters));

        return signatureBase.ToString();
    }

    /// <summary>
    /// Generate the signature value based on the given signature base and hash algorithm
    /// </summary>
    /// <param name="signatureBase">The signature based as produced by the GenerateSignatureBase method or by any other means</param>
    /// <param name="hash">The hash algorithm used to perform the hashing. If the hashing algorithm requires initialization or a key it should be set prior to calling this method</param>
    /// <returns>A base64 string of the hash value</returns>
    public static string GenerateSignatureUsingHash(string signatureBase, HashAlgorithm hash)
    {
        return ComputeHash(hash, signatureBase);
    }

        /// <summary>
    /// Helper function to compute a hash value
    /// </summary>
    /// <param name="hashAlgorithm">The hashing algoirhtm used. If that algorithm needs some initialization, like HMAC and its derivatives, they should be initialized prior to passing it to this function</param>
    /// <param name="data">The data to hash</param>
    /// <returns>a Base64 string of the hash value</returns>
    private static string ComputeHash(HashAlgorithm hashAlgorithm, string data)
    {
        if (hashAlgorithm == null)
        {
            throw new ArgumentNullException("hashAlgorithm");
        }

        if (string.IsNullOrEmpty(data))
        {
            throw new ArgumentNullException("data");
        }

        byte[] dataBuffer = System.Text.Encoding.ASCII.GetBytes(data);
        byte[] hashBytes = hashAlgorithm.ComputeHash(dataBuffer);

        return Convert.ToBase64String(hashBytes);
    }

/// <summary>
    /// Generates a signature using the specified signatureType 
    /// </summary>      
    /// <param name="url">The full url that needs to be signed including its non OAuth url parameters</param>
    /// <param name="consumerKey">The consumer key</param>
    /// <param name="consumerSecret">The consumer seceret</param>
    /// <param name="token">The token, if available. If not available pass null or an empty string</param>
    /// <param name="tokenSecret">The token secret, if available. If not available pass null or an empty string</param>
    /// <param name="httpMethod">The http method used. Must be a valid HTTP method verb (POST,GET,PUT, etc)</param>
    /// <param name="signatureType">The type of signature to use</param>
    /// <returns>A base64 string of the hash value</returns>
    public static string GenerateSignature(Uri url, string consumerKey, string consumerSecret, string token, string tokenSecret, string httpMethod, string timeStamp, string nonce, SignatureTypes signatureType, SortedList<String, String> parameters, out string normalizedUrl, out string normalizedRequestParameters)
    {
        normalizedUrl = null;
        normalizedRequestParameters = null;

        switch (signatureType)
        {
            case SignatureTypes.PLAINTEXT:
                return HttpUtility.UrlEncode(string.Format("{0}&{1}", consumerSecret, tokenSecret));
            case SignatureTypes.HMACSHA1:


                string signatureBase = GenerateSignatureBase(url, consumerKey, token, tokenSecret, httpMethod, timeStamp, nonce, HMACSHA1SignatureType, parameters, out normalizedUrl, out normalizedRequestParameters);

                HMACSHA1 hmacsha1 = new HMACSHA1();
                hmacsha1.Key = Encoding.ASCII.GetBytes(string.Format("{0}&{1}", UrlEncode(consumerSecret), string.IsNullOrEmpty(tokenSecret) ? "" : UrlEncode(tokenSecret)));

                return GenerateSignatureUsingHash(signatureBase, hmacsha1);
            case SignatureTypes.RSASHA1:
                throw new NotImplementedException();
            default:
                throw new ArgumentException("Unknown signature type", "signatureType");
        }
    }

But check out http://oauth.net/core/1.0a/ for details.