iis 7.5 dns windows authentication page user identity not working

In IIS 7.5 server I have a website apps.mydomain.com. Site binding for this website is:

IP: All Unassigned

Port: 80

Host name: apps.mydomain.com

In DNS there is an ip address pointing to apps.mydomain.com. Site comes up fine when browsing to this hostname.

I want to get current windows logged in username from asp.net web apps. I enabled windows authentication and disabled anonymous. Using this ASP.Net code to test:

Response.Write(Page.User.Identity.Name);

However, browsing to http://apps.mydomain.com/site/ the application pool identity shows as the Page.User.Identity.Name value and not the current windows logged in username.

If I browse to http://servername/site/ then Page.User.Identity.Name will return current windows logged in username.

Is there something else I need to configure to get the current windows logged in username when using host header?

web.config:

    <?xml version="1.0"?>
<configuration>
    <system.web>
        <authentication mode="Windows"/>
    </system.web>
</configuration>

App pool config (left out "handlers" for brevity, there's a 30000 char limit):

    <sectionGroup name="system.webServer">
        <section name="asp" overrideModeDefault="Deny" />
        <section name="caching" overrideModeDefault="Allow" />
        <section name="cgi" overrideModeDefault="Deny" />
        <section name="defaultDocument" overrideModeDefault="Allow" />
        <section name="directoryBrowse" overrideModeDefault="Allow" />
        <section name="fastCgi" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
        <section name="globalModules" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
        <section name="handlers" overrideModeDefault="Deny" />
        <section name="httpCompression" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
        <section name="httpErrors" overrideModeDefault="Allow" />
        <section name="httpLogging" overrideModeDefault="Deny" />
        <section name="httpProtocol" overrideModeDefault="Allow" />
        <section name="httpRedirect" overrideModeDefault="Allow" />
        <section name="httpTracing" overrideModeDefault="Deny" />
        <section name="isapiFilters" allowDefinition="MachineToApplication" overrideModeDefault="Deny" />
        <section name="modules" allowDefinition="MachineToApplication" overrideModeDefault="Deny" />
        <section name="odbcLogging" overrideModeDefault="Deny" />
        <sectionGroup name="security">
            <section name="access" overrideModeDefault="Deny" />
            <section name="applicationDependencies" overrideModeDefault="Deny" />
            <sectionGroup name="authentication">
                <section name="anonymousAuthentication" overrideModeDefault="Deny" />
                <section name="basicAuthentication" overrideModeDefault="Deny" />
                <section name="clientCertificateMappingAuthentication" overrideModeDefault="Deny" />
                <section name="digestAuthentication" overrideModeDefault="Deny" />
                <section name="iisClientCertificateMappingAuthentication" overrideModeDefault="Deny" />
                <section name="windowsAuthentication" overrideModeDefault="Deny" />
            </sectionGroup>
            <section name="authorization" overrideModeDefault="Allow" />
            <section name="ipSecurity" overrideModeDefault="Deny" />
            <section name="isapiCgiRestriction" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="requestFiltering" overrideModeDefault="Allow" />
        </sectionGroup>
        <section name="serverRuntime" overrideModeDefault="Deny" />
        <section name="serverSideInclude" overrideModeDefault="Deny" />
        <section name="staticContent" overrideModeDefault="Allow" />
        <sectionGroup name="tracing">
            <section name="traceFailedRequests" overrideModeDefault="Allow" />
            <section name="traceProviderDefinitions" overrideModeDefault="Deny" />
        </sectionGroup>
        <section name="urlCompression" overrideModeDefault="Allow" />
        <section name="validation" overrideModeDefault="Allow" />
        <sectionGroup name="webdav">
            <section name="globalSettings" overrideModeDefault="Deny" />
            <section name="authoring" overrideModeDefault="Deny" />
            <section name="authoringRules" overrideModeDefault="Deny" />
        </sectionGroup>
    </sectionGroup>
    <sectionGroup name="system.ftpServer">
        <section name="log" overrideModeDefault="Deny" allowDefinition="AppHostOnly" />
        <section name="firewallSupport" overrideModeDefault="Deny" allowDefinition="AppHostOnly" />
        <section name="caching" overrideModeDefault="Deny" allowDefinition="AppHostOnly" />
        <section name="providerDefinitions" overrideModeDefault="Deny" />
        <sectionGroup name="security">
            <section name="ipSecurity" overrideModeDefault="Deny" />
            <section name="requestFiltering" overrideModeDefault="Deny" />
            <section name="authorization" overrideModeDefault="Deny" />
        </sectionGroup>
        <section name="serverRuntime" overrideModeDefault="Deny" allowDefinition="AppHostOnly" />
    </sectionGroup>
</configSections>

<configProtectedData>
    <providers>
        <add name="IISWASOnlyRsaProvider" type="" description="Uses RsaCryptoServiceProvider to encrypt and decrypt" keyContainerName="iisWasKey" cspProviderName="" useMachineContainer="true" useOAEP="false" />
        <add name="AesProvider" type="Microsoft.ApplicationHost.AesProtectedConfigurationProvider" description="Uses an AES session key to encrypt and decrypt" keyContainerName="iisConfigurationKey" cspProviderName="" useOAEP="false" useMachineContainer="true" sessionKey="AQIAAA5mAAAApAAAGvGl78LKqlTFEdnH/kqoKL6P2gWJP1j89yxhxFD1wpbaE9Y6eMLhitoa2hmeMe41BWRQw/hdv2m9RkX9cFS0UwwlcpSBAgy59xZNmPm0TKg0QcRZ6Pbx4NZdOZ5nflNugABheZbScJenA3fU0L9Ct6kx0mllufWr4SzxOtLKkHY=" />
        <add name="IISWASOnlyAesProvider" type="Microsoft.ApplicationHost.AesProtectedConfigurationProvider" description="Uses an AES session key to encrypt and decrypt" keyContainerName="iisWasKey" cspProviderName="" useOAEP="false" useMachineContainer="true" sessionKey="AQIAAA5mAAAApAAApYI8BiiY8XN6fR5Ss1KzIoB31xACHhSGMMfLrWMwF1r4kh+1T3SkVS+cRbaQj1kJfPIvAv6G+Wwjot42TE0c7zrGkGaikte8dzkwp5d5U63vcc3vk2DTf/Eae4y7uHVtodFZ6gR+IEvAJZNvdyWB2rFnPT/j8T+f5/dCoeLXgnI=" />
    </providers>
</configProtectedData>

<system.applicationHost>
    <sites>
        <site name="apps.mydomain.com" id="2" serverAutoStart="true">
            <application path="/" applicationPool=".NET 2.0 Apps">
                <virtualDirectory path="/" physicalPath="C:\inetpub\wwwroot\apps" />
            </application>
            <application path="/test" applicationPool="test">
                <virtualDirectory path="/" physicalPath="C:\inetpub\wwwroot\apps\test" />
            </application>
            <bindings>
                <binding protocol="http" bindingInformation="*:80:apps.mydomain.com" />
                <binding protocol="net.msmq" bindingInformation="localhost" />
                <binding protocol="net.pipe" bindingInformation="*" />
                <binding protocol="net.tcp" bindingInformation="808:*" />
                <binding protocol="msmq.formatname" bindingInformation="localhost" />
            </bindings>
            <traceFailedRequestsLogging enabled="false" />
        </site>
        <siteDefaults>
            <logFile logFormat="W3C" directory="%SystemDrive%\inetpub\logs\LogFiles" />
            <traceFailedRequestsLogging directory="%SystemDrive%\inetpub\logs\FailedReqLogFiles" />
        </siteDefaults>
        <applicationDefaults applicationPool="DefaultAppPool" />
        <virtualDirectoryDefaults allowSubDirConfig="true" />
    </sites>

</system.applicationHost>

<system.webServer>

    <asp>
        <cache diskTemplateCacheDirectory="%SystemDrive%\inetpub\temp\ASP Compiled Templates" />
    </asp>

    <caching enabled="true" enableKernelCache="true">
    </caching>

    <cgi />

    <defaultDocument enabled="true">
        <files>
            <add value="Default.htm" />
            <add value="Default.asp" />
            <add value="index.htm" />
            <add value="index.html" />
            <add value="iisstart.htm" />
            <add value="default.aspx" />
        </files>
    </defaultDocument>

    <directoryBrowse enabled="false" />

    <fastCgi />

    <!--

      The <globalModules> section defines all native-code modules.
      To enable a module, specify it in the <modules> section.

    -->
    <globalModules>
        <add name="UriCacheModule" image="%windir%\System32\inetsrv\cachuri.dll" />
        <add name="FileCacheModule" image="%windir%\System32\inetsrv\cachfile.dll" />
        <add name="TokenCacheModule" image="%windir%\System32\inetsrv\cachtokn.dll" />
        <add name="HttpCacheModule" image="%windir%\System32\inetsrv\cachhttp.dll" />
        <add name="StaticCompressionModule" image="%windir%\System32\inetsrv\compstat.dll" />
        <add name="DefaultDocumentModule" image="%windir%\System32\inetsrv\defdoc.dll" />
        <add name="DirectoryListingModule" image="%windir%\System32\inetsrv\dirlist.dll" />
        <add name="ProtocolSupportModule" image="%windir%\System32\inetsrv\protsup.dll" />
        <add name="StaticFileModule" image="%windir%\System32\inetsrv\static.dll" />
        <add name="AnonymousAuthenticationModule" image="%windir%\System32\inetsrv\authanon.dll" />
        <add name="RequestFilteringModule" image="%windir%\System32\inetsrv\modrqflt.dll" />
        <add name="CustomErrorModule" image="%windir%\System32\inetsrv\custerr.dll" />
        <add name="HttpLoggingModule" image="%windir%\System32\inetsrv\loghttp.dll" />
        <add name="RequestMonitorModule" image="%windir%\System32\inetsrv\iisreqs.dll" />
        <add name="IsapiModule" image="%windir%\System32\inetsrv\isapi.dll" />
        <add name="IsapiFilterModule" image="%windir%\System32\inetsrv\filter.dll" />
        <add name="ConfigurationValidationModule" image="%windir%\System32\inetsrv\validcfg.dll" />
        <add name="ManagedEngine64" image="%windir%\Microsoft.NET\Framework64\v2.0.50727\webengine.dll" preCondition="integratedMode,runtimeVersionv2.0,bitness64" />
        <add name="ManagedEngine" image="%windir%\Microsoft.NET\Framework\v2.0.50727\webengine.dll" preCondition="integratedMode,runtimeVersionv2.0,bitness32" />
        <add name="WindowsAuthenticationModule" image="%windir%\System32\inetsrv\authsspi.dll" />
        <add name="ManagedEngineV4.0_32bit" image="c:\Windows\Microsoft.NET\Framework\v4.0.30319\webengine4.dll" preCondition="integratedMode,runtimeVersionv4.0,bitness32" />
        <add name="ManagedEngineV4.0_64bit" image="c:\Windows\Microsoft.NET\Framework64\v4.0.30319\webengine4.dll" preCondition="integratedMode,runtimeVersionv4.0,bitness64" />
        <add name="TracingModule" image="%windir%\System32\inetsrv\iisetw.dll" />
        <add name="FailedRequestsTracingModule" image="%windir%\System32\inetsrv\iisfreb.dll" />
    </globalModules>

    <httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files">
        <scheme name="gzip" dll="%Windir%\system32\inetsrv\gzip.dll" />
        <staticTypes>
            <add mimeType="text/*" enabled="true" />
            <add mimeType="message/*" enabled="true" />
            <add mimeType="application/x-javascript" enabled="true" />
            <add mimeType="application/atom+xml" enabled="true" />
            <add mimeType="application/xaml+xml" enabled="true" />
            <add mimeType="*/*" enabled="false" />
        </staticTypes>
    </httpCompression>

    <httpErrors lockAttributes="allowAbsolutePathsWhenDelegated,defaultPath">
        <error statusCode="401" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="401.htm" />
        <error statusCode="403" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="403.htm" />
        <error statusCode="404" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="404.htm" />
        <error statusCode="405" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="405.htm" />
        <error statusCode="406" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="406.htm" />
        <error statusCode="412" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="412.htm" />
        <error statusCode="500" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="500.htm" />
        <error statusCode="501" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="501.htm" />
        <error statusCode="502" prefixLanguageFilePath="%SystemDrive%\inetpub\custerr" path="502.htm" />
    </httpErrors>

    <httpLogging dontLog="false" />

    <httpProtocol>
        <customHeaders>
            <clear />
            <add name="X-Powered-By" value="ASP.NET" />
        </customHeaders>
        <redirectHeaders>
            <clear />
        </redirectHeaders>
    </httpProtocol>

    <httpRedirect />

    <httpTracing>
    </httpTracing>

    <isapiFilters>
        <filter name="ASP.Net_2.0.50727-64" path="%windir%\Microsoft.NET\Framework64\v2.0.50727\aspnet_filter.dll" enableCache="true" preCondition="bitness64,runtimeVersionv2.0" />
        <filter name="ASP.Net_2.0.50727.0" path="%windir%\Microsoft.NET\Framework\v2.0.50727\aspnet_filter.dll" enableCache="true" preCondition="bitness32,runtimeVersionv2.0" />
        <filter name="ASP.Net_2.0_for_V1.1" path="%windir%\Microsoft.NET\Framework\v2.0.50727\aspnet_filter.dll" enableCache="true" preCondition="runtimeVersionv1.1" />
        <filter name="ASP.Net_4.0_64bit" path="c:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_filter.dll" enableCache="true" preCondition="runtimeVersionv4.0,bitness64" />
        <filter name="ASP.Net_4.0_32bit" path="c:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet_filter.dll" enableCache="true" preCondition="runtimeVersionv4.0,bitness32" />
    </isapiFilters>

    <odbcLogging />

    <security>

        <access sslFlags="None" />

        <applicationDependencies>
            <application name="Active Server Pages" groupId="ASP" />
        </applicationDependencies>

        <authentication>

            <anonymousAuthentication enabled="true" userName="IUSR" />

            <basicAuthentication />

            <clientCertificateMappingAuthentication />

            <digestAuthentication />

            <iisClientCertificateMappingAuthentication />

            <windowsAuthentication enabled="false">
                <providers>
                    <add value="Negotiate" />
                    <add value="NTLM" />
                </providers>
            </windowsAuthentication>

        </authentication>

        <authorization />

        <ipSecurity />

        <isapiCgiRestriction>
            <add path="%windir%\Microsoft.NET\Framework64\v2.0.50727\aspnet_isapi.dll" allowed="true" groupId="ASP.NET v2.0.50727" description="ASP.NET v2.0.50727" />
            <add path="%windir%\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll" allowed="true" groupId="ASP.NET v2.0.50727" description="ASP.NET v2.0.50727" />
            <add path="C:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" allowed="true" groupId="ASP.NET v4.0.30319" description="ASP.NET v4.0.30319" />
            <add path="C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" allowed="true" groupId="ASP.NET v4.0.30319" description="ASP.NET v4.0.30319" />
            <add path="%windir%\system32\inetsrv\asp.dll" allowed="true" groupId="ASP" description="Active Server Pages" />
        </isapiCgiRestriction>

        <requestFiltering>
            <fileExtensions allowUnlisted="true" applyToWebDAV="true">
                <add fileExtension=".asax" allowed="false" />
                <add fileExtension=".ascx" allowed="false" />
                <add fileExtension=".master" allowed="false" />
                <add fileExtension=".skin" allowed="false" />
                <add fileExtension=".browser" allowed="false" />
                <add fileExtension=".sitemap" allowed="false" />
                <add fileExtension=".config" allowed="false" />
                <add fileExtension=".cs" allowed="false" />
                <add fileExtension=".csproj" allowed="false" />
                <add fileExtension=".vb" allowed="false" />
                <add fileExtension=".vbproj" allowed="false" />
                <add fileExtension=".webinfo" allowed="false" />
                <add fileExtension=".licx" allowed="false" />
                <add fileExtension=".resx" allowed="false" />
                <add fileExtension=".resources" allowed="false" />
                <add fileExtension=".mdb" allowed="false" />
                <add fileExtension=".vjsproj" allowed="false" />
                <add fileExtension=".java" allowed="false" />
                <add fileExtension=".jsl" allowed="false" />
                <add fileExtension=".ldb" allowed="false" />
                <add fileExtension=".dsdgm" allowed="false" />
                <add fileExtension=".ssdgm" allowed="false" />
                <add fileExtension=".lsad" allowed="false" />
                <add fileExtension=".ssmap" allowed="false" />
                <add fileExtension=".cd" allowed="false" />
                <add fileExtension=".dsprototype" allowed="false" />
                <add fileExtension=".lsaprototype" allowed="false" />
                <add fileExtension=".sdm" allowed="false" />
                <add fileExtension=".sdmDocument" allowed="false" />
                <add fileExtension=".mdf" allowed="false" />
                <add fileExtension=".ldf" allowed="false" />
                <add fileExtension=".ad" allowed="false" />
                <add fileExtension=".dd" allowed="false" />
                <add fileExtension=".ldd" allowed="false" />
                <add fileExtension=".sd" allowed="false" />
                <add fileExtension=".adprototype" allowed="false" />
                <add fileExtension=".lddprototype" allowed="false" />
                <add fileExtension=".exclude" allowed="false" />
                <add fileExtension=".refresh" allowed="false" />
                <add fileExtension=".compiled" allowed="false" />
                <add fileExtension=".msgx" allowed="false" />
                <add fileExtension=".vsdisco" allowed="false" />
                <add fileExtension=".rules" allowed="false" />
                <add fileExtension=".asa" allowed="false" />
            </fileExtensions>
            <verbs allowUnlisted="true" applyToWebDAV="true" />
            <hiddenSegments applyToWebDAV="true">
                <add segment="web.config" />
                <add segment="bin" />
                <add segment="App_code" />
                <add segment="App_GlobalResources" />
                <add segment="App_LocalResources" />
                <add segment="App_WebReferences" />
    开发者_如何学JAVA            <add segment="App_Data" />
                <add segment="App_Browsers" />
            </hiddenSegments>
        </requestFiltering>

    </security>

    <serverRuntime />

    <serverSideInclude />


    <tracing>

        <traceFailedRequests />

        <traceProviderDefinitions>
            <add name="ASPNET" guid="{AFF081FE-0247-4275-9C4E-021F3DC1DA35}">
                <areas>
                    <add name="Infrastructure" value="1" />
                    <add name="Module" value="2" />
                    <add name="Page" value="4" />
                    <add name="AppServices" value="8" />
                </areas>
            </add>
            <add name="WWW Server" guid="{3a2a4e84-4c21-4981-ae10-3fda0d9b0f83}">
                <areas>
                    <clear />
                    <add name="Authentication" value="2" />
                    <add name="Security" value="4" />
                    <add name="Filter" value="8" />
                    <add name="StaticFile" value="16" />
                    <add name="CGI" value="32" />
                    <add name="Compression" value="64" />
                    <add name="Cache" value="128" />
                    <add name="RequestNotifications" value="256" />
                    <add name="Module" value="512" />
                    <add name="FastCGI" value="4096" />
                </areas>
            </add>
            <add name="ASP" guid="{06b94d9a-b15e-456e-a4ef-37c984a2cb4b}">
                <areas>
                    <clear />
                </areas>
            </add>
            <add name="ISAPI Extension" guid="{a1c2040e-8840-4c31-ba11-9871031a19ea}">
                <areas>
                    <clear />
                </areas>
            </add>
        </traceProviderDefinitions>

    </tracing>

    <urlCompression />

    <validation />

</system.webServer>
<location path="" overrideMode="Allow">
    <system.webServer>
        <modules>
            <add name="HttpCacheModule" lockItem="true" />
            <add name="StaticCompressionModule" lockItem="true" />
            <add name="DefaultDocumentModule" lockItem="true" />
            <add name="DirectoryListingModule" lockItem="true" />
            <add name="IsapiFilterModule" lockItem="true" />
            <add name="ProtocolSupportModule" lockItem="true" />
            <add name="StaticFileModule" lockItem="true" />
            <add name="AnonymousAuthenticationModule" lockItem="true" />
            <add name="RequestFilteringModule" lockItem="true" />
            <add name="CustomErrorModule" lockItem="true" />
            <add name="IsapiModule" lockItem="true" />
            <add name="HttpLoggingModule" lockItem="true" />
            <add name="ConfigurationValidationModule" lockItem="true" />
            <add name="OutputCache" type="System.Web.Caching.OutputCacheModule" preCondition="managedHandler" />
            <add name="Session" type="System.Web.SessionState.SessionStateModule" preCondition="managedHandler" />
            <add name="WindowsAuthenticationModule" lockItem="true" />
            <add name="WindowsAuthentication" type="System.Web.Security.WindowsAuthenticationModule" preCondition="managedHandler" />
            <add name="FormsAuthentication" type="System.Web.Security.FormsAuthenticationModule" preCondition="managedHandler" />
            <add name="DefaultAuthentication" type="System.Web.Security.DefaultAuthenticationModule" preCondition="managedHandler" />
            <add name="RoleManager" type="System.Web.Security.RoleManagerModule" preCondition="managedHandler" />
            <add name="UrlAuthorization" type="System.Web.Security.UrlAuthorizationModule" preCondition="managedHandler" />
            <add name="FileAuthorization" type="System.Web.Security.FileAuthorizationModule" preCondition="managedHandler" />
            <add name="AnonymousIdentification" type="System.Web.Security.AnonymousIdentificationModule" preCondition="managedHandler" />
            <add name="Profile" type="System.Web.Profile.ProfileModule" preCondition="managedHandler" />
            <add name="UrlMappingsModule" type="System.Web.UrlMappingsModule" preCondition="managedHandler" />
            <add name="ServiceModel-4.0" type="System.ServiceModel.Activation.ServiceHttpModule, System.ServiceModel.Activation, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" preCondition="managedHandler,runtimeVersionv4.0" />
            <add name="UrlRoutingModule-4.0" type="System.Web.Routing.UrlRoutingModule" preCondition="managedHandler,runtimeVersionv4.0" />
            <add name="ScriptModule-4.0" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" preCondition="managedHandler,runtimeVersionv4.0" />
            <add name="ServiceModel" type="System.ServiceModel.Activation.HttpModule, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" preCondition="managedHandler,runtimeVersionv2.0" />
            <add name="FailedRequestsTracingModule" lockItem="true" />
        </modules>
        <handlers accessPolicy="Read, Script">        
        </handlers>
    </system.webServer>
</location>
<location path="apps.mydomain.com/test">
    <system.webServer>
        <security>
            <authentication>
                <anonymousAuthentication enabled="false" userName="" />
                <windowsAuthentication enabled="true" useKernelMode="true">
                    <extendedProtection tokenChecking="None" />
                </windowsAuthentication>
            </authentication>
        </security>
    </system.webServer>
</location>

---

Most likely, because the http://servername/site/ is working, it is because you are resolving to internal DNS servers, so Windows Auth kicks in for you. Have you tried explicitly setting the authentication method to 'Windows' in the web.config file?

<authentication mode="Windows" />

---

Change the app pool for the test application from "test" to ".NET 2.0 Apps" as the root of your site has different config from the test application. The windows athentication is setup correctly for ".NET 2.0 Apps" app pool but i think that dosn't effect the "test" app pool.

good luck