How do you use openAuth from a windows client application?

I am looking at integrating a public api in to an existin开发者_开发问答g windows form application. The api requires openAuth authentication. All examples of this that I have seen are on web based applications.

How can openAUth be used on a client application?

thanks

Its not the easiest of things to explain, but I did this for a YouTube implementation:

I built a ShardOAuth Class that builds the messages:

    #Region "Imports"
Imports System.Text
Imports System.Security.Cryptography
#End Region

Public NotInheritable Class SharedOAuth

#Region "Class Declarations"
    Private Const unreservedChars As String = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.~"

    Private Const OAuthVersion As String = "1.0"
    Private Const OAuthParameterPrefix As String = "oauth_"
    Private Const OAuthParameterExclusionPrefix As String = "xoauth_"

    Private Const OAuthConsumerKeyKey As String = "oauth_consumer_key"
    Private Const OAuthCallbackKey As String = "oauth_callback"
    Private Const OAuthVersionKey As String = "oauth_version"
    Private Const OAuthSignatureMethodKey As String = "oauth_signature_method"
    Private Const OAuthSignatureKey As String = "oauth_signature"
    Private Const OAuthTimestampKey As String = "oauth_timestamp"
    Private Const OAuthNonceKey As String = "oauth_nonce"
    Private Const OAuthTokenKey As String = "oauth_token"
    Private Const OAuthTokenSecretKey As String = "oauth_token_secret"
#End Region

#Region "Constructor"
    Private Sub New()
        'prevent construction
    End Sub
#End Region


#Region "Shared Functions"
    Public Shared Function GetSignatureTypeNameFromType(ByVal signatureType As enumerations.OAuthEnumerations.SignatureTypes) As String
        Select Case signatureType
            Case enumerations.OAuthEnumerations.SignatureTypes.HmacSha1
                Return "HMAC-SHA1"
            Case Else
                Return String.Empty
        End Select
    End Function

    Public Shared Function GenerateTimeStamp() As String
        'Implementation of UNIX current UTC time
        Dim _ts As TimeSpan = DateTime.UtcNow - New DateTime(1970, 1, 1, 0, 0, 0, 0)
        Return Convert.ToInt64(_ts.TotalSeconds).ToString(CultureInfo.InvariantCulture)
    End Function

    Public Shared Function GenerateNonce() As String
        'Some random Number
        Return New Random().Next(123400, 9999999).ToString
    End Function

    Public Shared Function UrlEncode(ByVal value As String) As String
        Dim _result As New StringBuilder

        If (String.IsNullOrEmpty(value)) Then
            Return value
        End If

        For Each _symbol As Char In value
            If unreservedChars.IndexOf(_symbol) <> -1 Then
                _result.Append(_symbol)
            Else
                _result.Append(String.Format("%{0}", String.Format("{0:X2}", Asc(_symbol))))
            End If
        Next

        Return _result.ToString
    End Function

    ''' <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 Shared Function GenerateSignature(ByVal url As Uri, ByVal consumerKey As String, ByVal consumerSecret As String, ByVal token As String, ByVal tokenSecret As String, ByVal httpMethod As String, ByVal timeStamp As String, ByVal nonce As String, ByVal signatureType As enumerations.OAuthEnumerations.SignatureTypes, ByRef normalizedUrl As String, ByRef normalizedRequestParameters As String) As String
        normalizedUrl = String.Empty
        normalizedRequestParameters = String.Empty

        Dim _signatureBase As String
        Dim _hash As HMACSHA1

        Select Case signatureType
            Case enumerations.OAuthEnumerations.SignatureTypes.HmacSha1
                _signatureBase = GenerateSignatureBase(url, consumerKey, token, tokenSecret, httpMethod, timeStamp, nonce, enumerations.OAuthEnumerations.SignatureTypes.HmacSha1, normalizedUrl, normalizedRequestParameters)

                Dim _sb As New StringBuilder
                With _sb
                    .Append(UrlEncode(consumerSecret))
                    .Append("&")

                    If (String.IsNullOrEmpty(tokenSecret)) Then
                        .Append("")
                    Else
                        .Append(UrlEncode(tokenSecret))
                    End If
                End With

                _hash = New HMACSHA1
                _hash.Key = Encoding.ASCII.GetBytes(_sb.ToString)

                Return GenerateSignatureUsingHash(_signatureBase, _hash)

            Case Else
                Throw New NotImplementedException

        End Select
    End Function

    Public Shared Function GenerateSignatureUsingHash(ByVal signatureBase As String, ByVal hash As HashAlgorithm) As String
        Return ComputeHash(hash, signatureBase)
    End Function

    Public Shared Function GenerateSignatureBase(ByVal url As Uri, ByVal consumerKey As String, ByVal token As String, ByVal tokenSecret As String, ByVal httpMethod As String, ByVal timeStamp As String, ByVal nonce As String, ByVal signatureType As enumerations.OAuthEnumerations.SignatureTypes, ByRef normalizedUrl As String, ByRef normalizedRequestParameters As String) As String
        Dim _SignatureTypeName As String = GetSignatureTypeNameFromType(signatureType)

        If String.IsNullOrEmpty(token) Then
            token = String.Empty
        End If

        If String.IsNullOrEmpty(tokenSecret) Then
            tokenSecret = String.Empty
        End If

        If String.IsNullOrEmpty(consumerKey) Then
            Throw New ArgumentNullException("consumerKey")
        End If

        If String.IsNullOrEmpty(httpMethod) Then
            Throw New ArgumentNullException("httpMethod")
        End If

        If String.IsNullOrEmpty(_SignatureTypeName) Then
            Throw New ArgumentNullException("SignatureType")
        End If

        normalizedUrl = String.Empty
        normalizedRequestParameters = String.Empty

        Dim _params As List(Of QueryParameter) = getqueryparameters(url.Query)

        With _params
            .Add(New QueryParameter(OAuthVersionKey, OAuthVersion))
            .Add(New QueryParameter(OAuthNonceKey, nonce))
            .Add(New QueryParameter(OAuthTimestampKey, timeStamp))
            .Add(New QueryParameter(OAuthSignatureMethodKey, _SignatureTypeName))
            .Add(New QueryParameter(OAuthConsumerKeyKey, consumerKey))

            If Not (String.IsNullOrEmpty(token)) Then
                .Add(New QueryParameter(OAuthTokenKey, token))
            End If

            .Sort(New QueryParameterComparer)
        End With

        normalizedUrl = String.Format("{0}://{1}", url.Scheme, url.Host)

        If Not ((url.Scheme = "http" AndAlso url.Port = 80) OrElse (url.Scheme = "https" AndAlso url.Port = 443)) Then
            normalizedUrl = String.Format("{0}:{1}", normalizedUrl, url.Port)
        End If

        normalizedUrl = String.Format("{0}{1}", normalizedUrl, url.AbsolutePath)

        normalizedRequestParameters = NormalizeRequestParameters(_params)

        Dim _sb As New StringBuilder
        With _sb
            .AppendFormat(CultureInfo.InvariantCulture, "{0}&", httpMethod.ToUpper)
            .AppendFormat(CultureInfo.InvariantCulture, "{0}&", UrlEncode(normalizedUrl))
            .AppendFormat(CultureInfo.InvariantCulture, "{0}", UrlEncode(normalizedRequestParameters))
        End With

        Return _sb.ToString

    End Function
#End Region

#Region "Private Methods"
    Private Shared Function ComputeHash(ByVal hashAlgorithm As HashAlgorithm, ByVal data As String) As String
        If hashAlgorithm Is Nothing Then
            Throw New ArgumentNullException("hashAlgorithm")
        End If

        If String.IsNullOrEmpty(data) Then
            Throw New ArgumentNullException("data")
        End If

        Dim _dataBuffer As Byte() = Encoding.ASCII.GetBytes(data)
        Dim _hashBytes As Byte() = hashAlgorithm.ComputeHash(_dataBuffer)

        Return Convert.ToBase64String(_hashBytes)
    End Function


    Private Shared Function NormalizeRequestParameters(ByVal parameters As IList(Of QueryParameter)) As String

        Dim _p As QueryParameter
        Dim _sb As New StringBuilder

        For i As Integer = 0 To parameters.count - 1
            _p = parameters(i)
            _sb.AppendFormat(CultureInfo.InvariantCulture, "{0}={1}", _p.Name, _p.Value)

            If i < parameters.count - 1 Then
                _sb.Append("&")
            End If
        Next

        Return _sb.ToString

    End Function

    Private Shared Function GetQueryParameters(ByVal parameters As String) As List(Of QueryParameter)
        If (parameters.StartsWith("?")) Then
            parameters = parameters.Remove(0, 1)
        End If

        Dim _result As New List(Of QueryParameter)
        Dim _p As String() = parameters.Split("&"c)

        Dim _temp As String()

        If Not (String.IsNullOrEmpty(parameters)) Then

            For Each s As String In _p
                If Not (String.IsNullOrEmpty(s)) AndAlso Not (s.StartsWith(OAuthParameterExclusionPrefix)) Then 'AndAlso (s.StartsWith(OAuthParameterPrefix)) Then
                    If s.IndexOf("=") > -1 Then
                        _temp = s.Split("="c)
                        _result.Add(New QueryParameter(_temp(0), _temp(1)))
                    Else
                        _result.Add(New QueryParameter(s, String.Empty))
                    End If
                End If

            Next

        End If

        Return _result

    End Function
#End Region


End Class

And then a Class to use these lower level functions to build and Parse the OAuth Messages

Public MustInherit Class BaseOAuth
    Inherits BaseAccess

#Region "Class Declarations"
    Protected Const CONSUMER_KEY As String = "anonymous"
    Protected Const CONSUMER_SECRET As String = "anonymous"

    Protected Const SCOPEURL As String = "http://gdata.youtube.com"  '

    Protected m_FeedCollection As ArrayList
#End Region

#Region "Constructor"
    Public Sub New()
        MyBase.new()
    End Sub

    Public Sub New(ByVal context As Common.Statefulogic.Context)
        MyBase.new(context)
    End Sub
#End Region

#Region "Public Properties"

#End Region

#Region "Private Functions"

#End Region

#Region "Public Methods"
    Public Function SignCommandUrl(ByVal commandUrl As String) As String
        Return SignCommandUrl(commandUrl, Nothing, Nothing)
    End Function

    Public Function SignCommandUrl(ByVal commandUrl As String, ByVal overrideToken As String, ByVal overrideTokenSecret As String) As String
        Dim _commandUri = New Uri(commandUrl)
        Dim _oAuthSignature As String
        Dim _oAuthTimeStamp As String = SharedOAuth.GenerateTimeStamp
        Dim _oAuthNOnce As String = SharedOAuth.GenerateNonce
        Dim _oAuth_normalized_url As String = String.Empty
        Dim _oAuth_normalized_params As String = String.Empty

        If Not (String.IsNullOrEmpty(overrideToken)) OrElse Not (String.IsNullOrEmpty(overrideTokenSecret)) Then
            _oAuthSignature = SharedOAuth.GenerateSignature(_commandUri, CONSUMER_KEY, CONSUMER_SECRET, overrideToken, overrideTokenSecret, "GET", _oAuthTimeStamp, _oAuthNOnce, enumerations.OAuthEnumerations.SignatureTypes.HmacSha1, _oAuth_normalized_url, _oAuth_normalized_params)
        Else

            If MasterAccessToken Is Nothing Then
                _oAuthSignature = SharedOAuth.GenerateSignature(_commandUri, CONSUMER_KEY, CONSUMER_SECRET, String.Empty, String.Empty, "GET", _oAuthTimeStamp, _oAuthNOnce, enumerations.OAuthEnumerations.SignatureTypes.HmacSha1, _oAuth_normalized_url, _oAuth_normalized_params)
            Else
                _oAuthSignature = SharedOAuth.GenerateSignature(_commandUri, CONSUMER_KEY, CONSUMER_SECRET, SharedOAuth.UrlEncode(MasterAccessToken.Token), MasterAccessToken.TokenSecret, "GET", _oAuthTimeStamp, _oAuthNOnce, enumerations.OAuthEnumerations.SignatureTypes.HmacSha1, _oAuth_normalized_url, _oAuth_normalized_params)
            End If
        End If

        'Get a token
        Dim _sb As New System.Text.StringBuilder
        With _sb
            .Append(_oAuth_normalized_url)
            .Append("?")
            .Append(_oAuth_normalized_params)
            .Append("&")
            .Append("oauth_signature")
            .Append("=")
            .Append(SharedOAuth.UrlEncode(_oAuthSignature))
        End With

        Return _sb.ToString
    End Function

    Public Function BuildPostHeader(ByVal commandUrl As String) As String
        Dim _commandUri = New Uri(commandUrl)
        Dim _oAuthTimeStamp As String = SharedOAuth.GenerateTimeStamp
        Dim _oAuthNOnce As String = SharedOAuth.GenerateNonce
        Dim _oAuth_normalized_url As String = String.Empty
        Dim _oAuth_normalized_params As String = String.Empty
        Dim _oAuthSignature As String

        If MasterAccessToken Is Nothing Then
            _oAuthSignature = SharedOAuth.GenerateSignature(_commandUri, CONSUMER_KEY, CONSUMER_SECRET, String.Empty, String.Empty, "POST", _oAuthTimeStamp, _oAuthNOnce, enumerations.OAuthEnumerations.SignatureTypes.HmacSha1, _oAuth_normalized_url, _oAuth_normalized_params)
        Else
            _oAuthSignature = SharedOAuth.GenerateSignature(_commandUri, CONSUMER_KEY, CONSUMER_SECRET, SharedOAuth.UrlEncode(MasterAccessToken.Token), MasterAccessToken.TokenSecret, "POST", _oAuthTimeStamp, _oAuthNOnce, enumerations.OAuthEnumerations.SignatureTypes.HmacSha1, _oAuth_normalized_url, _oAuth_normalized_params)
        End If


        Dim _sb As New System.Text.StringBuilder
        With _sb
            .Append("Authorization: OAuth oauth_version=""1.0"", ")
            .AppendFormat("oauth_nonce=""{0}"", ", _oAuthNOnce)
            .AppendFormat("oauth_timestamp=""{0}"", ", _oAuthTimeStamp)
            .AppendFormat("oauth_consumer_key=""{0}"", ", CONSUMER_KEY)
            .AppendFormat("oauth_token=""{0}"", ", MasterAccessToken.Token)
            .Append("oauth_signature_method=""HMAC-SHA1"", ")
            .AppendFormat("oauth_signature=""{0}""", _oAuthSignature)
        End With

        Return _sb.ToString
    End Function

    Public Shared Function PostRequestReturnCollection(ByVal commandUrl As String) As NameValueCollection
        Dim _nameValCollection As NameValueCollection

        Dim _request As HttpWebRequest = CType(WebRequest.Create(commandUrl), HttpWebRequest)

        Using _response As HttpWebResponse = CType(_request.GetResponse, HttpWebResponse)
            Using _reader As TextReader = New StreamReader(_response.GetResponseStream)
                _nameValCollection = HttpUtility.ParseQueryString(_reader.ReadToEnd)
            End Using
        End Using

        Return _nameValCollection
    End Function
#End Region

End Class

And Finally a Call to Get the OAuth Tokens..

Public Function RequestApplicationAccess() As TokenParams
    Dim _oAuthCallbackConfirmed As Boolean
    Dim _oAuthTokenUrl As String
    Dim _oauth_Authenticate_Page As String
    Dim _oAuthtokendataCollection As NameValueCollection
    Dim _request As HttpWebRequest

    Dim _oauth_token As String = String.Empty
    Dim _oauth_token_secret As String = String.Empty
    Dim _oauth_verifier As String = String.Empty

    m_CallbackSite = "http://www.previewthebestof.co.uk/_services/googleauth.aspx"

    'Generate a signature
    Dim _RequestUrl As String = "https://www.google.com/accounts/OAuthGetRequestToken"
    _oAuthTokenUrl = SignCommandUrl(String.Format("{0}?scope={1}&oauth_callback={2}&xoauth_displayname={3}", _RequestUrl, SharedOAuth.UrlEncode(SCOPEURL), SharedOAuth.UrlEncode(m_CallbackSite), SharedOAuth.UrlEncode(APPDISPLAYNAME)))

    _oAuthtokendataCollection = PostRequestReturnCollection(_oAuthTokenUrl)

    _oauth_token = _oAuthtokendataCollection.Item("oauth_token")
    _oauth_token_secret = _oAuthtokendataCollection.Item("oauth_token_secret")

    If _oAuthtokendataCollection.Count = 3 Then
        _oAuthCallbackConfirmed = CType(_oAuthtokendataCollection.Item("oauth_callback_confirmed"), Boolean)
    End If

    If String.IsNullOrEmpty(_oauth_token) OrElse String.IsNullOrEmpty(_oauth_token_secret) Then
        Throw New N5.Common.ExceptionManager.N5Exception("Cannot get an authentication token (_oauth_token or _oauth_token_secret is blank)")
    End If

    '----------------------------------------------------
    'Write the token to the users profile
    m_Context.UserObject.SetUserAuthenticationTokens(_oauth_token, String.Empty, String.Empty, String.Empty)

    '-----------------------------------------------------
    'Authorize the token
    _RequestUrl = "https://www.google.com/accounts/OAuthAuthorizeToken"

    _oAuthTokenUrl = String.Format("{0}?oauth_token={1}", _RequestUrl, SharedOAuth.UrlEncode(_oauth_token))

    _request = CType(WebRequest.Create(_oAuthTokenUrl), HttpWebRequest)
    Using _response = CType(_request.GetResponse, HttpWebResponse)
        Using _reader As TextReader = New StreamReader(_response.GetResponseStream)
            _oauth_Authenticate_Page = _reader.ReadToEnd
        End Using
    End Using

    If Not (_oauth_Authenticate_Page.ToLower.Contains("<html>")) Then
        Throw New N5.Common.ExceptionManager.N5Exception("AuthToken Respose does not contain a webpage")
    End If

    'Response contains html, which is the youtube authentication page - need to show this to the user 
    'write to temp file
    Dim _tempFileName As String = IO.Path.Combine(My.Computer.FileSystem.SpecialDirectories.Temp, String.Concat(FilenameUtilities.GetRandomFilename, ".htm"))
    Using _tempFile As New StreamWriter(_tempFileName)
        _tempFile.Write(_oauth_Authenticate_Page)
    End Using

    'Load a browser form and navigate to the file just created.
    Using _browser As New BasePopupBrowser
        With _browser
            .WindowState = FormWindowState.Maximized
            .AutoCloseText = "<H1>OAuth Token Authorised</H1>"
            .CheckForAutoCloseText = True
            .NavigateTo(New System.Uri(_tempFileName))
        End With
    End Using

    'Clean up the tempfile
    My.Computer.FileSystem.DeleteFile(_tempFileName)

    '------------------------------------------------------
    'Check the db for a request_token - did the user press authorise?
    m_Context.UserObject.RefreshUserAuthenticationTokens()
    Dim _dv As DataView = m_Context.UserObject.AuthenticationTokensDataView
    _dv.RowFilter = "TokenName='YouTubeAuthVerifier'"

    If _dv.Count > 0 Then
        _oauth_verifier = _dv(0)("Value").ToString
    End If

    If String.IsNullOrEmpty(_oauth_verifier) Then
        'We didnt get a verification token back, chances are the user pressed reject, Doh!
        Return Nothing
    End If

    '---------------------------------------------------------
    'Now we need to exchange the request token for an access token
    _RequestUrl = String.Format("https://www.google.com/accounts/OAuthGetAccessToken?oauth_verifier={0}", SharedOAuth.UrlEncode(_oauth_verifier))

    _oAuthTokenUrl = SignCommandUrl(_RequestUrl, _oauth_token, _oauth_token_secret)

    _oAuthtokendataCollection = PostRequestReturnCollection(_oAuthTokenUrl)

    _oauth_token = _oAuthtokendataCollection.Item("oauth_token")
    _oauth_token_secret = _oAuthtokendataCollection.Item("oauth_token_secret")

    m_Context.UserObject.SetUserAuthenticationTokens(String.Empty, String.Empty, _oauth_token, _oauth_token_secret)

    Return New TokenParams(_oauth_token, _oauth_token_secret)
End Function

The Wrox book Professional Twitter Development: With Examples in .NET 3.5 has a walkthrough of doing OAuth from a C# client, and the code is available as a free download from their website.