ADAL .Net Core nuget package does not support UserPasswordCredential

Question

In ADAL.Net 3.x UserPasswordCredential is introduced on top of UserCredential from 2.x. But the same UserPasswordCredential is not exposed in the .Net Core under the same nuget package?

UserCredential class has only one property UserName

namespace Microsoft.IdentityModel.Clients.ActiveDirectory
{
    //
    // Summary:
    //     Credential used for integrated authentication on domain-joined machines.
    public class UserCredential
    {
        //
        // Summary:
        //     Constructor to create user credential. Using this constructor would imply integrated
        //     authentication with logged in user and it can only be used in domain joined scenarios.
        public UserCredential();
        //
        // Summary:
        //     Constructor to create credential with client id and secret
        //
        // Parameters:
        //   userName:
        //     Identifier of the user application requests token on behalf.
        public UserCredential(string userName);

        //
        // Summary:
        //     Gets identifier of the user.
        public string UserName { get; }
    }
}

Since UserPasswordCredential is not available in .NetCore and UserCredential takes only one parameter username, how to input the password of the user and implement below code in .Net Core?

authContext.AcquireTokenAsync(WebAPIResourceId, ClientId, userPasswordCredential);

I am using ADAL 3.13.4 version specifically in .Net Core 1.0 version

Answer 1

To use the resource owner password credentials grant flow to get the access token for Azure AD, we can call the http request diectly using the HttpClient. Here is an example for your reference :

HttpClient client = new HttpClient();
string tokenEndpoint = "https://login.microsoftonline.com/{tenantId}/oauth2/token";
var body = "resource={resourceUrl}&client_id={clientId}&grant_type=password&username={userName}&password={password}";
var stringContent = new StringContent(body, Encoding.UTF8, "application/x-www-form-urlencoded");

var result=await client.PostAsync(tokenEndpoint, stringContent).ContinueWith<string>((response) =>
{
    return response.Result.Content.ReadAsStringAsync().Result;
});

JObject jobject = JObject.Parse(result);

var token = jobject["access_token"].Value<string>();

Answer 2

You are correct, UserPasswordCredential is not available for .NET Core, and UserCredential no longer accepts username and password. This means ADAL v3 does not support the username/password flow on .NET Core.

Answer 3

Below is what i have been doing to get around this problem. I replicated the same behaviour in a static method for use in .NET Core, since the UserPasswordCredential class is missing. This is based on fiddler traces of what happens when the UserPasswordCredential class is used in the .NET version. Since the .NET DLL seems to be obfuscated, this is a best attempt at capturing what it does.

public const string Saml11Bearer = "urn:ietf:params:oauth:grant-type:saml1_1-bearer";
public const string Saml20Bearer = "urn:ietf:params:oauth:grant-type:saml2-bearer";
public const string JwtBearer = "urn:ietf:params:oauth:grant-type:jwt-bearer";

/// <summary>
/// Acquire an AAD authentication token silently for an AAD App (Native) with an AAD account
/// 
/// NOTE: This process was ported from the Microsoft.IdentityModel.Clients.ActiveDirectory's
///  AuthenticationContext.AcquireTokenAsync method, which can silently authenticate using the UserPasswordCredential class.
///  Since this class is missing from .NET Core, this method can be used to perform the same without any dependencies.
/// </summary>
/// <param name="user">AAD login</param>
/// <param name="pass">AAD pass</param>
/// <param name="tenantId">Tenant ID</param>
/// <param name="resourceUrl">Resource ID: the Azure app that will be accessed</param>
/// <param name="clientId">The Application ID of the calling app. This guid can be obtained from Azure Portal > app auth setup > Advanced Settings</param>
public static string GetAuthTokenForAADNativeApp(string user, SecureString pass, string tenantId, string resourceUrl, string clientId)
{
    string tokenForUser = string.Empty;
    string authority = "https://login.microsoftonline.com/" + tenantId; // The AD Authority used for login
    string clientRequestID = Guid.NewGuid().ToString();

    // Discover the preferred openid / oauth2 endpoint for the tenant (by authority)
    string api = "https://login.microsoftonline.com/common/discovery/instance?api-version=1.1&authorization_endpoint=" + authority + "/oauth2/authorize";
    string openIdPreferredNetwork = string.Empty;
    var client = new HttpClient();
    client.DefaultRequestHeaders.Clear();
    client.DefaultRequestHeaders.Add("client-request-id", clientRequestID);
    client.DefaultRequestHeaders.Add("return-client-request-id", "true");
    client.DefaultRequestHeaders.Add("Accept", "application/json");

    var responseTask = client.GetAsync(api);
    responseTask.Wait();
    if (responseTask.Result.Content != null)
    {
        var responseString = responseTask.Result.Content.ReadAsStringAsync();
        responseString.Wait();
        try
        {
            dynamic json = JObject.Parse(responseString.Result);
            openIdPreferredNetwork = json.metadata[0].preferred_network; // e.g. login.microsoftonline.com
        }
        catch { }
    }
    if (string.IsNullOrEmpty(openIdPreferredNetwork))
        openIdPreferredNetwork = "login.microsoftonline.com";

    // Get the federation metadata url & federation active auth url by user realm (by user domain)
    responseTask = client.GetAsync("https://" + openIdPreferredNetwork + "/common/userrealm/" + user + "?api-version=1.0");
    responseTask.Wait();
    string federation_metadata_url = string.Empty;
    string federation_active_auth_url = string.Empty;
    if (responseTask.Result.Content != null)
    {
        var responseString = responseTask.Result.Content.ReadAsStringAsync();
        responseString.Wait();
        try
        {
            dynamic json = JObject.Parse(responseString.Result);
            federation_metadata_url = json.federation_metadata_url; // e.g. https://sts.{domain}.com.au/adfs/services/trust/mex
            federation_active_auth_url = json.federation_active_auth_url; // e.g. https://sts.{domain}.com.au/adfs/services/trust/2005/usernamemixed
        }
        catch { }
    }
    if(string.IsNullOrEmpty(federation_metadata_url) || string.IsNullOrEmpty(federation_active_auth_url))
        return string.Empty;

    // Get federation metadata
    responseTask = client.GetAsync(federation_metadata_url);
    responseTask.Wait();
    string federationMetadataXml = null;
    if (responseTask.Result.Content != null)
    {
        var responseString = responseTask.Result.Content.ReadAsStringAsync();
        responseString.Wait();
        try
        {
            federationMetadataXml = responseString.Result;
        }
        catch { }
    }
    if (string.IsNullOrEmpty(federationMetadataXml))
        return string.Empty;

    // Post credential to the federation active auth URL
    string messageId = Guid.NewGuid().ToString("D").ToLower();
    string postData = @"
<s:Envelope xmlns:s='http://www.w3.org/2003/05/soap-envelope' xmlns:a='http://www.w3.org/2005/08/addressing' xmlns:u='http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd'>
<s:Header>
<a:Action s:mustUnderstand='1'>http://schemas.xmlsoap.org/ws/2005/02/trust/RST/Issue</a:Action>
<a:MessageID>urn:uuid:" + messageId + @"</a:MessageID>
<a:ReplyTo>
<a:Address>http://www.w3.org/2005/08/addressing/anonymous</a:Address>
</a:ReplyTo>
<a:To s:mustUnderstand='1'>" + federation_active_auth_url + @"</a:To>
<o:Security s:mustUnderstand='1' xmlns:o='http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd'>
<u:Timestamp u:Id='_0'>
<u:Created>" + DateTime.Now.ToString("o") + @"</u:Created>
<u:Expires>" + DateTime.Now.AddMinutes(10).ToString("o") + @"</u:Expires>
</u:Timestamp>
<o:UsernameToken u:Id='uuid-" + Guid.NewGuid().ToString("D").ToLower() + @"'>
<o:Username>" + user + @"</o:Username>
<o:Password>" + FromSecureString(pass) + @"</o:Password>
</o:UsernameToken>
</o:Security>
</s:Header>
<s:Body>
<trust:RequestSecurityToken xmlns:trust='http://schemas.xmlsoap.org/ws/2005/02/trust'>
<wsp:AppliesTo xmlns:wsp='http://schemas.xmlsoap.org/ws/2004/09/policy'>
<a:EndpointReference>
  <a:Address>urn:federation:MicrosoftOnline</a:Address>
</a:EndpointReference>
</wsp:AppliesTo>
<trust:KeyType>http://schemas.xmlsoap.org/ws/2005/05/identity/NoProofKey</trust:KeyType>
<trust:RequestType>http://schemas.xmlsoap.org/ws/2005/02/trust/Issue</trust:RequestType>
</trust:RequestSecurityToken>
</s:Body>
</s:Envelope>";
    var content = new StringContent(postData, Encoding.UTF8, "application/soap+xml");
    client.DefaultRequestHeaders.Clear();
    client.DefaultRequestHeaders.Add("SOAPAction", "http://schemas.xmlsoap.org/ws/2005/02/trust/RST/Issue");
    client.DefaultRequestHeaders.Add("client-request-id", clientRequestID);
    client.DefaultRequestHeaders.Add("return-client-request-id", "true");
    client.DefaultRequestHeaders.Add("Accept", "application/json");

    responseTask = client.PostAsync(federation_active_auth_url, content);
    responseTask.Wait();
    XmlDocument xml = new XmlDocument();
    string assertion = string.Empty;
    string grant_type = string.Empty;
    if (responseTask.Result.Content != null)
    {
        HttpResponseMessage rseponse = responseTask.Result;
        Task<string> responseContentTask = rseponse.Content.ReadAsStringAsync();
        responseContentTask.Wait();
        try { xml.LoadXml(responseContentTask.Result); }
        catch { }
        var nodeList = xml.GetElementsByTagName("saml:Assertion");
        if (nodeList.Count > 0)
        {
            assertion = nodeList[0].OuterXml;
            // The grant type depends on the assertion value returned previously <saml:Assertion MajorVersion="1" MinorVersion="1"...>
            grant_type = Saml11Bearer;
            string majorVersion = nodeList[0].Attributes["MajorVersion"] != null ? nodeList[0].Attributes["MajorVersion"].Value : string.Empty;
            if (majorVersion == "1")
                grant_type = Saml11Bearer;
            if (majorVersion == "2")
                grant_type = Saml20Bearer;
            else
                grant_type = Saml11Bearer; // Default to Saml11Bearer
        }
    }

    // Post to obtain an oauth2 token to for the resource 
    // (*) Pass in the assertion XML node encoded to base64 in the post, as is done here https://blogs.msdn.microsoft.com/azuredev/2018/01/22/accessing-the-power-bi-apis-in-a-federated-azure-ad-setup/
    UserAssertion ua = new UserAssertion(assertion, grant_type, Uri.EscapeDataString(user));
    UTF8Encoding encoding = new UTF8Encoding();
    Byte[] byteSource = encoding.GetBytes(ua.Assertion);
    string base64ua = Uri.EscapeDataString(Convert.ToBase64String(byteSource));
    postData = "resource={resourceUrl}&client_id={clientId}&grant_type={grantType}&assertion={assertion}&scope=openid"
        .Replace("{resourceUrl}", Uri.EscapeDataString(resourceUrl))
        .Replace("{clientId}", Uri.EscapeDataString(clientId))
        .Replace("{grantType}", Uri.EscapeDataString(grant_type))
        .Replace("{assertion}", base64ua);
    content = new StringContent(postData, Encoding.UTF8, "application/x-www-form-urlencoded");
    client.DefaultRequestHeaders.Clear();
    client.DefaultRequestHeaders.Add("client-request-id", clientRequestID);
    client.DefaultRequestHeaders.Add("return-client-request-id", "true");
    client.DefaultRequestHeaders.Add("Accept", "application/json");

    responseTask = client.PostAsync("https://" + openIdPreferredNetwork + "/common/oauth2/token", content);
    responseTask.Wait();
    if (responseTask.Result.Content != null)
    {
        var responseString = responseTask.Result.Content.ReadAsStringAsync();
        responseString.Wait();
        try
        {
            dynamic json = JObject.Parse(responseString.Result);
            tokenForUser = json.access_token;
        }
        catch { }
    }
    if (string.IsNullOrEmpty(federationMetadataXml))
        return string.Empty;


    return tokenForUser;
}

private static string FromSecureString(SecureString value)
{
    string stringBSTR;
    IntPtr bSTR = Marshal.SecureStringToBSTR(value);
    if (bSTR == IntPtr.Zero)
    {
        return string.Empty;
    }
    try
    {
        stringBSTR = Marshal.PtrToStringBSTR(bSTR);
    }
    finally
    {
        Marshal.FreeBSTR(bSTR);
    }
    return stringBSTR;
}