Author: NomadIT

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Azure AD Synchronization Customization Cont.

In a previous post I talked about customizing the Azure AD synch rules to do some gymnastics with AD attributes getting imported into Azure AD. Recently I ran into a vendor who required that the email address’s capitalization match the capitalization in their SSO entries in order for the SSO to work. So if, on my side of things, I formatted people’s email addresses JohnDoe@domain.com, but in the application I set someone’s email address to be johndoe@domain.com, these two entries would not match and the SSO would not work.

I know. I’m flabbergasted as well.

To solve this, we resolved to always use lowercases for email addresses in both our AD and the application. But we’re human, people make mistakes, and more importantly people leave jobs with institutional knowledge like this and we may as try to make the computers do some of this work for us. As it turns out, the AD Sync synchronization rules editor has a function to convert strings to all uppercase or lowercase. We’ll use the previous post as a jumping off point. 

Modified:
IIF(IsPresent([extensionAttribute1]),LCase([extensionAttribute1]), IIF(IsPresent([userPrincipalName]),[userPrincipalName], IIF(IsPresent([sAMAccountName]),([sAMAccountName]&"@"&%Domain.FQDN%),Error("AccountName is not present"))))

Wrapping [extensionAttribute1] with LCase() will force what’s in the user’s AD extensionAttribute1 attribute to be sent to Azure AD all lowercase. This makes sure that, at least from the IT side of things, we won’t have any problems if we accidentally set up JohnDoe@domain.com

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Crontab – Run the first Tuesday for a full week

I recently had a cronjob that I wanted to run on the first full Tuesday of the month. Well, crontab doesn’t handle this, obviously, but it got me thinking how to figure this one out. As it so happens, the first Tuesday of the month will always fall somewhere between the 2nd and the 8th.

I’m defining the first full week of the month as the first week where, starting Monday, every day that week is of the same month.

So, the earliest full week is one where the 1st falls on a Monday, so the 2nd falls on a Tuesday.

Following that logic, the latest full week would be one where the month starts on a Tuesday, meaning the first full week starts with the 7th on a Monday. That means the first Tuesday of a full week would be on the 8th.

So if we make a cronjob that runs every Tuesday and checks if the date is >= 2 and <= 8, we should always find the first Tuesday of the month that is part of a full week.

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OAuth2 Proxy Cont.

As is any SysAdmin’s wont in life, I’ve been messing around with OAuth2-Proxy and trying to add additional functionality beyond It-Finally-Works. If you haven’t already seen my previous post about setting up OAuth2-Proxy, please check it out since I’ll be working from that foundation.

Sign Out

While it might not have been the most important thing for a wiki page, it would be nice for my users to have the option to sign out if, say, they’re on a public computer (and responsible enough users to actually think of that, but that’s another story altogether).

This should be as simple as putting a “sign out” link for the users to click, but what URL do we use there. Well, there are two things we have to consider: the locally cached cookies, and the actual IDP session. If we do the first, but not the second, we’ll be taken to back to a login screen, but as soon as the IDP auth begins, your IDP will say “No need, you’re already logged in” and send you on your way without a username and password prompt. If you do the second, but not the first, then you won’t even get the sign in screen, because the cookies will still be cached. Even if you’re logged out from the IDP’s perspective, OAuth2-proxy still sees the cookies and will let you in without needing to check with your IDP.

OAuth2-Proxy’s documentation tell us we can use the following to clear cookies:

/oauth2/sign_out?rd=https%3A%2F%2Fmy-oidc-provider.example.com%2Fsign_out_page

but then we need to also redirect to the IDP provider to also close sessions there. For Azure AD, that url is:

https://login.microsoftonline.com/common/oauth2/v2.0/logout? post_logout_redirect_uri=http%3A%2F%2Flocalhost%2Fmyapp%2F

So we’ll need to combine these two into a URL. That monstrosity (including all of the HTML URL encoding necessary) should look something like this (assuming you’re using Azure AD as your IDP):

https://wiki.domain.com/oauth2/sign_out?rd=https%3A%2F%2Flogin.microsoftonline.com%2Fcommon%2Foauth2%2Fv2.0%2Flogout%3Fpost%5Flogout%5Fredirect%5Furi%3Dhttps%3A%2F%2Fwiki.domain.com

This URL will first tell OAuth2-Proxy to remove its cookies. then redirect (rd) to login.microsoft.com to log out of Azure AD, then tell Azure AD to re-route back to wiki.domain.com. From the user’s perspective, they’ll click on a sign out screen, choose a user account they’re logged in as to log out of, then get kicked to a couple of informational screens, then back to the sign in page.

There’s two more steps we need before we’re done. First, go into the Azure Portal, and go back to your registered app (Azure AD > App Registrations, and click your registered app). In the left-hand panel, go to “Authentication” and in the main panel, scroll down to “Front-channel logout URL.” Here, put in https://wiki.domain.com/oauth2/sign_out. I’m not entirely sure if this is correct, since in my testing I couldn’t quite get single sign-out to work right, but it couldn’t hurt.

Finally, and this is important, go into your config file and add whitelist_domains = "login.microsoft.com" (or whatever domain your IDP uses). Without this, OAuth2-Proxy won’t redirect to your IDP.

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OAuth2-Proxy

Don’t want to hear me babble and just want to get to the meat? Click here to go straight to the instructions.

My company recently published a company wiki for end users to go to in order to find answers to common tech issues we’ve seen in our environment (wishful thinking, I know). And even more recently, we’ve found that we wanted to put up some more sensitive information that we wouldn’t want out on the public internet. To solve this, I wanted to force users to authenticate using their Azure AD SSO credentials before viewing the wiki.

Our wiki is published through a WordPress site, and considering how many plugins there are for WordPress, I figured it couldn’t be that difficult to find something I could use, right?

Wrong.

Turns out there are a few plug-ins that will allow admins to authenticate with SSO to administrate the site and publish, but nothing that would require visitors to authenticate before viewing the site. After a bunch of searching, I finally found my solution: OAuth2-Proxy.

Now for the catch: this does exactly what I wanted it to do, but the documentation is terrible, and I have an incredibly rudimentary knowledge of how Apache and reverse proxies work. Cue a few days of Just Trying Stuff ™ before finally finding the combination of things that worked.

So here’s all I’m trying to accomplish. I want a user to go to my site (wiki.domain.com), receive an SSO prompt, log in, and then get to my site. Simple, right? Below is a little diagram that OAuth2-Proxy presents that shows what I’m trying to do.

In this case, I’ll be using OAuth2-Proxy as my reverse proxy. Thankfully it has this built-in so I don’t have to go through the headache of making this work with NGINX (something I only barely know how to configure to begin with).

First thing’s first, I need to get things set up in Azure AD, which will be my Auth Provider. Because this is using OAuth2 and not SAML, I can’t create an Enterprise Application in Azure. We’ll use App Registrations under Azure AD. Also, because this is Microsoft and they insist on changing their UI nearly constantly, this guide comes with the customary guarantee of 5 feet or 5 minutes, whichever comes first.

Azure AD

  • Go to Azure AD and, in the left panel, go to Manage > App Registrations
  • Click New Registration
  • Give the app a name, leave everything else default.
  • Click Register.
  • In the app, on the Overview page, note the Application (client) ID and the Directory (tenant) ID.
  • In the left panel, in Manage > Authentication, under “Redirect URIs,” add a new one for https://wiki.domain.com/oauth2/callback. Save.
  • In the left panel, in Manage > Certificates & secrets, under Client Secrets, create a new client secret. Note the Value (not the Secret ID). Also note the expiration on the secret. This will need to be renewed when the secret expires. Microsoft no longer allows secrets that do not expire.

Linux

I went with Ubuntu as the OS for my Oauth2-Proxy server. I will also note here that I’m primarly a Windows sys admin that has been allowed to dabble in Linux, so I might be doing stuff all funky like. Don’t @ me.

  • Create your working directory /home/username/oauth2proxy
  • Create a logs directory /home/username/oauth2proxy/logs
  • Create a www directory /home/username/oauth2proxy/www
  • Go to https://github.com/oauth2-proxy/oauth2-proxy and download the appropriate binary (wget URL/to/file)
  • Extract from the tarball (tar -xf filename).
  • Move oauth2-proxy to the root of the working directory (/home/username/oauth2proxy).
  • Run dd if=/dev/urandom bs=32 count=1 2>/dev/null | base64 | tr -d -- '\n' | tr -- '+/' '-_'; echo and note the result as your cookie secret.
  • Obtain TLS pem and key cert. Easiest to do this with certbot.
  • (Optional) Place a logo file as /home/username/oauth2proxy/www/logo.png
  • Create a config file (/home/username/oauth2proxy/config.cfg) with the following:
    provider = "azure"
    client_id = <enter client ID here from above>
    client_secret = <enter client secret value from above>
    oidc_issuer_url = "https://sts.windows.net/<enter tenant id here>/"
    cookie_secret = "<enter cookie secret here from above>"
    email_domains = "*"
    upstreams = "https://<IP address of site behind SSO>:<port>/"
    http_address = "127.0.0.1:80"
    https_address = ":443"
    request_logging = true
    standard_logging = true
    auth_logging = true
    logging_filename = "/home/username/oauth2proxy/logs/log.txt"
    ssl_upstream_insecure_skip_verify = "true"
    tls_cert_file = "/path/to/cert.pem"
    tls_key_file = "/path/to/privkey.pem"
    force_https = "true"
    custom_sign_in_logo= "/home/username/oauth2proxy/www/logo.png"
  • Create a Bash script (oauth2proxy.sh):
    #!/bin/bash /
    home/username/oauth2proxy/oauth2-proxy --config /home/username/oauth2proxy/config.cfg
  • Make the script executable (chmod 755 oauth2proxy.sh)
  • Copy the script to /etc/init.d
  • Create a symlink to run the script on startup (ln -s /etc/init.d/oauth2proxy.sh /etc/rc3.d/S02oauth2proxy.sh)
  • Reboot the server and confirm if the script is running

DNS and Networking

In DNS, make sure that wiki.domain.com is pointing to the public IP address of your OAuth2-Proxy server. You also want to make sure that the server running the wiki is only allowing http and/or https traffic from your OAuth2-Proxy server, otherwise people can do an end run around your proxy server and access the wiki directly via IP.

Stuff That Didn’t Work (And How To Fix It)

Here are some of the issues and roadblocks I ran into while I was implementing this, and how I went about solving them.

Browser gives a “Redirected too many times” error after SSO authentication
In the config file, make sure the syntax for the Upstreams parameter is exactly what I have. I had to make sure I included the port to forward traffic to (even if I’m forwarding http traffic to port 80) and had to make sure I ended the line with “/”.

Receiving a 403 Forbidden page after SSO authentication
In the config file, make sure to set the email domains to “*”. I originally had my email domain here, and maybe I need to figure out what the actual correct syntax here is, but I wound up giving it the “Domain Admins” treatment.

Can’t navigate to subpages on the upstream site
So I could go through SSO authentication and get to wiki.domain.com, but I could not then click on any links or get to wiki.domain.com/subpage. Turns out all the links on my site were pointing to http://wiki.domain.com/subpage instead of https://wiki.domain.com/subpage. Changing all of the links (I found a WordPress plugin that would do this for me in the WordPress database) to start with https://wiki.domain.com worked.

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Delete Files Based On File Age

Ever wanted to delete every file over a certain age? Maybe for pesky log files that are ballooning the storage on your server?

The below script will delete all files in a specified folder that is older than the current date. Modify as necessary to change the age of files you want. Set up a Windows task to run as necessary. 

$folder = "C:\Path\To\Folder"
$date = Get-Date -format "MM/dd/yyyy" | out-string
$files = Get-childitem -path $folder | where {$_.LastWriteTime -lt $date}
Remove-item $files.FullName
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Enable Inheritance Without Taking Ownership

Having NTFS permissions that are messed up is a HUGE headache. Fixing them means trying to trick NTFS into letting you do what you need to, and sometimes it just won’t let you. Below is my nuclear option that will, at least, get you back where you can make the necessary changes to get what you need set.

Download the NTFSSecurity powershell module, unblock the zip file, then extract it to C:\Windows\System32\WindowsPowerShell\v1.0\Modules

Make sure that the top level folder has the permissions you want to inherit. Make sure you have permissions on this top level folder.

Run Powershell as admin. 

Run the following commands in the folder you want to propagate inheritance down from: 

import-module ntfssecurity
enable-privileges
get-childitem -recurse | Enable-NTFSAccessInheritance
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Run Windows Explorer as Admin

You may have noticed that since Server 2012 R2, signing in with a local admin account (that isn’t .\Administrator) doesn’t run Windows Explorer as an admin. You’ll be logged in, of course, but File Explorer won’t be running with elevated privileges, and that means that you can’t change security ACLs on files through the GUI.

As it turns out, it’s pretty easy to fix this on a session-by-session basis.

Fire up Powershell as admin (for some reason this doesn’t work in CMD and I haven’t had the brain space to figure out why) and run the following: 

taskkill /f /FI "USERNAME eq $env:UserName"/im explorer.exe

That will kill the exiting explorer session for you (and it won’t restart, as it’s wont to do if you kill the process through task manager).

Then, run the following:

c:\windows\explorer.exe /nouaccheck

That’ll fire up explorer again, but this time you’ll be able to open File Explorer with your admin privileges and make changes as necessary.

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Ansible “until” loop

Continuing on with Amateur Ansible Fumbling Hour, here’s what I wanted to do, and what wound up working, with commentary on the errors I got and what’s going on for those unable to make heads or tails of the Ansible documentation.

I have an Ansible playbook that runs updates on servers, and then reboots them after the updates finish. However, I have noticed that after rebooting, an essential service on a server isn’t starting automatically, despite the service being set to start automatically. This seems like a great situation to add something into my playbook to check the status of that service and start it if it’s not started. However, I also wanted some level of error handling, just in case the service didn’t start automatically because something was stopping it just after reboot.

Here is the playbook that finally worked. 

---
- hosts: hosts
  tasks:
  - name: Check and start Service
    win_service:
      name: "service_name"
      state: started
    register: result
    until: (result is not failed) and (result.state == "running")
    retries: 5
    delay: 10

Now let me explain a couple of roadblocks I ran into trying to get this to work.

As you can see, I’ve got the results of the service start command being registered to result. Then, I use until to check the contents of the result variable, and specifically the running object. Below is the output of result after a successful run of the playbook. 

changed: [server.domain.com] => {
    "attempts": 3,
    "can_pause_and_continue": false,
    "changed": true,
    "depended_by": [],
    "dependencies": [
    ],
    "description": "Service description",
    "desktop_interact": false,
    "display_name": "Service Name",
    "exists": true,
    "invocation": {
        "module_args": {
            "dependencies": null,
            "dependency_action": "set",
            "description": null,
            "desktop_interact": false,
            "display_name": null,
            "error_control": null,
            "failure_actions": null,
            "failure_actions_on_non_crash_failure": null,
            "failure_command": null,
            "failure_reboot_msg": null,
            "failure_reset_period_sec": null,
            "force_dependent_services": false,
            "load_order_group": null,
            "name": "service",
            "password": null,
            "path": null,
            "pre_shutdown_timeout_ms": null,
            "required_privileges": null,
            "service_type": null,
            "sid_info": null,
            "start_mode": null,
            "state": "started",
            "update_password": null,
            "username": null
        }
    },
    "name": "Service",
    "path": "C:\Windows\System32\service.exe",
    "start_mode": "manual",
    "state": "running",
    "username": "LocalSystem"
}

So of course, I can use until to run the playbook until result.state == running, but when I only checked against that, I got an error message saying that dict object has no attribute 'state'. This took me a while to puzzle out, but the issue was that when the playbook failed (let’s say because the service was set to disabled), then nothing was being written to the result variable. Then, when the playbook went to check the contents of that vairable, of course there was no attribute ‘state.’ This is why I added the other check result is not failed. So now the playbook can’t fail, and the service has to be running for the playbook to end.

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Server Not Found in Kerberos Database

I recently started trying to use Ansible to manage all of the disparate systems I have at the office, and in trying to set up Ansible to communicate with our Windows systems, I ran into this (among other) issues. Despite having all of the right ports open to communicate with WinRM, a couple of systems were giving the error 

Server not found in Kerberos database

After some digging, I discovered that Kerberos is highly dependent on DNS to be able to perform both a forward and reverse lookup. In my case, my reverse lookup zone had not correctly populated for the servers that were giving this error.

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Edgerouter VPN CLI Commands

When working an Edgerouter setting an IPSec VPN, the following commands have come in handy. All of these are written assuming you have just fired up the CLI.

Reset the VPN, from either side of the tunnel:

clear vpn ipsec-peer <peer name>

Realtime ipsec connection logs:

sudo swanctl --log