After 2 days searching on the internet cannot find a way to limit user authentication by IP range.
I have 2 rodc(A and B) and a RWDC. I have user1 in my RWDC active directory.
I want to specify a user to RODC A, but both clients in both RODC can login to windows with user1.
Is there any way to limit user authentication by IP using PowerShell.
To agree with #Vasili Syrakis, how you are describing your problem, you have to do this with firewalls, or routing on your managed switch.
AD is designed for authentication of users. All it does is verify that the user exists, is a member of the appropriate groups, passwords match, is not disabled, and that's it. AD does no validation based on IP address, and is not capable, or designed for doing that.
You have to change the way you are thinking. Don't think about trying to limit user authentication, let AD do it's job and authenticate the user. You have to think about it in terms of limiting access to the resource.
How you limit access to the resource really depends on what the resource is. If you want to limit it at the Server level (i.e. don't allow anyone from 192.168.1.xxx subnet get to me), then you have to have a firewall or switch that manages access control. Firewalls and access control lists are designed to do this. They won't let the user even reach the resource, and so they won't even get the chance to authenticate with AD.
If it is specific computers (not necessarily IP addresses) that you want to stop people from logging into, then you do that with a combination of AD Groups and Group Policy See: Deny and Allow Logons with Group Policy
Related
I have recently deployed a JEA endpoint on a few Domain Controllers for a user (Domain User, non privileged).
The user had to be added to "Remote Management Users" AD group in order to have the ability to Powershell into a these DCs.
It occurred to me that outside of the provided, confined endpoint, the user can create sessions to default Powershell endpoint which has access to everything.
Following the great article, I would have to add the user under the permissions of the default windows.powershell endpoint which isn't a straight forward process.
What would be the sensible way to confine the given user to just the one particular endpoint?
Many thanks,
I have 2 users, one with less than 30 roles and one with 400 roles. When I login with the 30 role user, I can reach the redirect URL without issues. But when I log in with the 400 role user, the request to the redirect URL doesn't complete. If I reduce the number of roles in the 400 role user then it will work. So, is there a way to disable passing roles in the java access token or increase some limit somewhere that's causing the failure?
I would suggest to focus rather on roles reduction/optimization than forcing the transmission (raising limits) over the maximum number of roles inside tokens (or anywhere else).
Some interesting questions (among others) to start with:
Which protected resources am I going to serve?
What am I trying to protect? and what are the associated risks? (build a Threat Model)
How do resources are served by each application? and how are they distributed among my applications?
What kind of resources are they? How can I group them? Which sets are identifiable? or what are the relationships between them? What actions are possible against all sets of resources?
Who are the users of each application? How will they interact with my resources? Which flows are sensitive?
What roles can I define for all my resources?
Which role can apply to each application, resource type or set?
What kind of user groups can I create?
Do I need additional attributes or claims for each set of roles or users/groups?
I firmly believe that if you answer all these questions you will end up having a bunch of roles instead of hundreds. Think security by design and follow principle of least privilege.
Focus on your use case
Now as far as I understand, your blocking point is that you are assuming that each resource is unique, sensitive and requires its own permissions, and consequently a role definition. While it may be true in some cases, in most other cases it does not mean that you have to use the token roles/scopes/claims to secure your assets deep at the resource-level. I'll try to illustrate this sentence by an example.
RBAC and authorizations example for your use case
Let's assume that:
you have millions of sensitive resources to serve
each registered user of your application has access to a (different) set of these resources.
your resources are splitted into, say, 3 categories (e-books, videos, musics).
each resource can be downloaded, uploaded, deleted.
your application will meet unregistered users, registered users, contributors and administrators
registered users will always have read access to resources (not a single action will ever allow a modification)
contributors are particular registered users who can perform special actions including modification ('upload', 'edit')
contributors and administrators may have access to various administrative parts of the application
your application will evolve by serving additional categories of resources in the future and new actions will be available to users later (such as 'flag', 'edit' or 'share link').
Then first things first:
organize your resources accordingly by serving them behind categorized paths such as: .../myapp/res/ebooks, .../myapp/res/videos, .../myapp/res/musics
identify your resources via UUID such that a resource may look like: .../myapp/res/ebooks/duz7327abdhgsd95a
Now imagine that your business risks or at least the greatest risks you wish to avoid are:
unregistered users having gaining access or rights for any part of the application or resource
uncontrolled registration process (robots, spam, no mail verification, fake users, ...)
registered users gaining illegal privileges (unauthorized actions, access to other categories, illegal administrative rights)
discovery of available resources by any mean
You will note that I voluntarily didn't listed:
registered user having illegal access to certain resources. For example: maliciously pointed/provided by an existing user.
This is because it is not a high risk as you may hold contact information about registered users as well as log activity and actions, quota or requests throttling, and you may be able to ban them or start legal action against them. Your registration process is also assumed robust and secure. Nonetheless if its considered a critical risk you can address this with extra mechanisms (cf. suggestions at the end). But never will it result in adding extra roles, such as one per resource, as it does not fit in any security model.
That being said, finally, here are the roles and authorizations scheme you may come with:
SCOPE / AUDIENCE
MY_APP
ROLES
USER
CONTRIBUTOR
ADMINISTRATOR
CLAIMS / ATTRIBUTES
CATEGORIES
ACTIONS
--> POSSIBLE USER GROUPS
USERS
Roles: USER
Claims: CATEGORIES(variable), ACTIONS('download')
CONTRIBUTORS
Roles: USER, CONTRIBUTOR
Claims: CATERGORIES(variable), ACTIONS('download', 'upload', 'edit')
ADMINISTRATORS
Roles: USER, CONTRIBUTOR, ADMINISTRATOR
Claims: CATEGORIES(*), ACTIONS(*)
Following this model, assigning the correct group to each registered user will provide high-grade security by mitigating/controlling the main risks. As claims/attributes are defined in the token(s) (managed and signed by Keycloak) then you can trust this information in your application and serve your resources accordingly and safely. There is also no risk of illegal access or discovery of resources as you are using UUIDs, only registered users having had access once to a resource will know it and registration with appropriate category access will be needed for another user to access it (to only be able to read it basically). Of course you may store in a database the list of resources to which each user has access to, raising the overall security to a very high level.
However, if the latest is not enough you may also implement rolling UUIDs or temporary links for your resources when served to users. To go farther you may also define groups and masks for your categories, resources and actions.
In fine, in this example I made use exclusively of token claims to define roles (common claim), categories and actions (custom claims). In terms of security the authentication and identity will be the first-line security followed by roles then categories, actions and stored list of resources per user (db).
Other alternatives are obviously possible, its just an example. Still, I hope it helps!
To fix this problem you should start from defining client scope mappings for each of you applications (e.g. oidc clients). Main idea of this facility is that even if your user is super duper admin with all existing roles, all of his roles actually don't required for any particular application. For example client foo which defines following roles:
foo_user
foo_viewer
to perform its security logic need to know only whether currently logged user has foo_user or foo_viewer, but it doesn't care about has this user roles bar_user or bar_admin from application bar. So our goal is to make Keycloak return for any client access token with only valuable set of roles for this client. And roles scope mappings is you friend here. You can set for client foo scope like:
foo.foo_user
foo.foo_viewer
bar.bar_admin
and now even if logged user has role "bar.bar_admin" this will not go to access_token since client foo doesn't take this role into account. After applying some scope settings you can test them at 'Clients -> $CLIENT_OIDC_ID -> Client scopes tab -> Evaluate sub tab.
As for you case with 400 roles, i'm quite confident that none of your application requires all of 400 roles, so precise scope configuration for you apllications can drammatically reduce access token size.
But if i'm mistaken and you really have an application that rely on large amount of roles you should look into you runtime settings.
For example if you run keycloak behind reverse proxy like nginx large tokens may not fit in default HTTP parameters buffer size (afaik about 2-4kb) so you have to increase it via appropriate nginx configuration option. Another example is tomcat which has about 16kb as default HTTP header buffer, so if you send request with very large access token in Authorization header Tomcat may not handle this request properly.
I'm studying Kubernetes now, and have a question about Kubernetes Users. I learned how to create Users and how to limit access by Role, but when should I use it? For example, if a malicious user (not a k8s user, but an operating user) penetrates the k8s server, they can switch the administrator easily (if they can see .kube/config). In addition to that, if a user switches his or her user account and forgets to switch back, then another person who enters next can also use the first user's account. I doubt if I misunderstand the usage of k8s Users, but there seems to be no documents about why k8s prepared it. I assume that Users are only used for doing something from within pods, but if so, what's the difference between Users and Service Accounts?
Kubernetes has a very loose idea of a user. It knows that authentication is a thing, and that the output of that is a name and maybe some groups and tags. But really all it does it hand that info off to the authorization plugins to decide if a given request is allowed or not. ServiceAccounts are a specific object type because they generate you a JWT signed by the cluster, but there isn't a specific User type, that only exists within the context of your authentication plugin(s).
I'm trying to write a proof-of-concept application that performs Kerberos delegation. I've written all the code, and it seems to working (I'm authenticating fine), but the resulting security context doesn't have the ISC_REQ_DELEGATE flag set.
So I'm thinking that maybe one of the endpoints (client or server) is forbidden to delegate. However I'm not authenticating against an SPN. Just one domain user against another domain user. As the SPN for InitializeSecurityContext() I'm passing "someuser#mydomain.lan" (which is the user account under which the server application is running). As I understand, domain users have delegation enabled by default. Anyway, I asked the admin to check, and the "account is sensitive and cannot be delegated" checkbox is off.
I know that if my server was running as a NETWORK SERVICE and I used an SPN to connect to it, then I'd need the computer account in AD to have the "Trust computer for delegation" checkbox checked (off by default), but... this is not the case, right? Or is it?
Also - when the checkbox in the computer account is set, do the changes take place immediately, or must I reboot the server PC or wait for a while?
According to this ISC_REQ_DELEGATE is only ignored if you use constrained delegation. I'm pretty sure for constrained delegation to happen, you have to explicitly state which services the account is allowed to delegate to in Active Directory (delegation tab for a user or computer in the AD snap in).
I'm not sure of the rules using UPNs vs SPNs. Have you tried turning on Kerberos event logging and looking in the event log? The messages are often cryptic but usually possible to decipher.
Your description of the NETWORK SERVICE scenario is accurate. Trust for delegation is off by default, but NETWORK SERVICE might have permission to self register an SPN (I think this can be determined by group policy).
When you tick the box the change takes place immediately, but may have to propogate throughout all the domain controllers in the domain (I typically test in a test domain with a single DC). So, restarting your service app is enough, you don't need to reboot.
The Kerb tickets reside on the client machine. These have an expiry time, and can be flushed manually using klist or kerbtray.
I've got two separate homemade applications that need to communicate among themselves. One is a frontend application (asp.net actually), the other is a backend interface to an accounting application. The backend interface was not created specifically for this frontend - it is a generic interface that many other applications use to integrate with our product.
For the convenience of users we wish to provide a Windows Authentication in our frontend application. That means however that we need to pass the credentials on to the backend application which has to check them.
We do not wish to set up our frontend as a "trusted" application to the backend which can authenticate itself as any user. If the frontend was to be hacked, it would then also compromise the backend system.
As I understand it, one way to do it with Windows Authentication is Kerberos Delegation. However this requires to be explicitly enabled for the user that is to be delegated, and the machine which does the delegation (the server with our frontend). By default these options are disabled in Active Directory, and I suspect that many sysadmins will have their reservations about turning them on for all their users.
Also, I'm not really sure that this is what Kerberos Delegation was meant for. I don't need our frontend to impersonate the user that is connecting. I just need to prove that this user has authenticated itself to me.
How would you do this?
I'm not clear what you can and can't do with your use case but I can answer the question what Kerberos Delegation was meant for.
First let's talk about what Kerberos does prior to delegation. It is important to understand this part well because it is subtle.
Kerberos authenticates the identity of BOTH ends of a communication between two end-points across a network, those end-points can be interactive users or services running on a computer.
This is strong authentication so it will not allow a man-in-middle attack in any form. If set up correctly an end point can guarantee they won't be compromised. To the level of the service name (if you are connecting to IIs on a machine it is different than connecting to SQL Server on the same machine). It makes heavy use of modern encryption techniques and requires the use of secure certificates. The details of the authentication protocol are complicated and not worth going into now, but it involves about 20 different distinct steps of confirmation between the two authenticating end points and authentication server (in windows the Domain Controller is the authentication server).
So what the heck is delegation?
Delegation is a Microsoft extension to the Kerberos standard which
allows a trusted source to continue the authentication to another
end-point.
This allows you to act as a "man in the middle" -- however many settings have to be explicitly setup, certificates installed, etc to allow this to work. It is far from simple. (EDIT: Here is another SO answer on the details - https://stackoverflow.com/a/954154/215752)
So, for example, you could have someone authenticate to a website and then have the .NET code connect to an SQL Server AS THE SAME USER to read data with that user's rights.
Now to answer your question, since I'm not sure what you want to do I present three choices:
1) You want to connect to the back end system as the SAME user as the one authenticating at the website.
In this case Kerberos delegation is perfect -- it does exactly what you want.
2) You want to connect to the back end system as a DIFFERENT user than the one authenticating at the website (eg a service account).
In this case you don't want delegation. Kerberos to the website and Kerberos (as a different user) to the back-end will work great.
3) You want to connect to the back end system as the SAME user some of the time and as a DIFFERENT user other times. (For example, you need to validate this is a legal user for the back end system, but want to perform trusted actions as a system account other times. This is (in my experience) the most common use case.)
In this case you use both. Delegation for the connections which need to validate the user identity and then revert to the service account identity for the times when you need system access to the back end. (A previous question of mine went into the details of how to revert to the system identity on the .NET platform see How to "un-impersonate" (un-delegate?) in Kerberos.)
Here is a post describing how Kerberos works and how to set it up.
ASP.NET passing along Windows Authentication credentials
Actually Kerberos delegation is designed exactly for this use case. But the challenge here is craft this on a legacy system and with AD's settings that you do not want to change.
One possible hack is to have the Front End just send the user and the time of authentication but the backend can query the Active Directory Event Logs to determine whether that user has authenticated to the Front end. This requires you to use WIndows Event Log API.and also play around with Event Log settings in AD to log the issue of service tickets. (MY recollection is that this is the default)
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