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Infrastructure Kerberos authentication

Background

Starting in November 2016, Fedora Infrastructure began to use Kerberos authentication for some services, starting with koji (the Fedora build system). On December 12th 2016, the koji buildsystem will be switched to only allow Kerberos authentication, and disallow the old SSL cert authentication. In March 2021 the authentication backend FAS was replaced with Accounts

Supported Services

  • koji
  • All Fedora Infrastructure ipsilon using applications via GSSAPI

Technical Details

Fedora Infrastructure is using Fedora Accounts (was FAS before), but now it syncs some account information to a pair of FreeIPA servers. Those servers are made available via a web proxy to Fedora contributors. Also, via the ipsilon identity management server and GSSAPI we are able to use Kerberos tickets to authenticate users to any services that use ipsilon.

How to use kerberos auth with Fedora Infrastructure

Command line

  • Install the krb5-workstation package (sudo dnf install krb5-workstation) if you do not have kinit command available.
  • If you are using two-factor authentication (OTP) you will also need the krb5-pkinit package.
  • You can check the Kerberos main configuration file /etc/krb5.conf that it contains stanza includedir /etc/krb5.conf.d/ to sources modules from the directory /etc/krb5.conf.d/. It should be something as following 
    includedir /etc/krb5.conf.d/

[logging]
 default = FILE:/var/log/krb5libs.log
 kdc = FILE:/var/log/krb5kdc.log
 admin_server = FILE:/var/log/kadmind.log

[libdefaults]
  dns_lookup_realm = false
  ticket_lifetime = 24h
  renew_lifetime = 7d
  forwardable = true
  rdns = false
  default_ccache_name = KEYRING:persistent:%{uid}
  dns_canonicalize_hostname = false

[realms]

[domain_realm]
  • Create the file /etc/krb5.conf.d/fedoraproject_org with the following content (or install the fedora-packager-kerberos package) 
    [realms]
 FEDORAPROJECT.ORG = {
        kdc = https://id.fedoraproject.org/KdcProxy
        pkinit_anchors = FILE:/etc/pki/ipa/fedoraproject_ipa_ca.crt
 }
[domain_realm]
 .fedoraproject.org = FEDORAPROJECT.ORG
 fedoraproject.org = FEDORAPROJECT.ORG
    Note
    See section Debugging problems to double sure the configuration
  • With fedora-packager-kerberos package you can run fkinit or fkinit -u yourusername. Alternatively you can do the following steps:
  • kinit <yourfasloginname>@FEDORAPROJECT.ORG
    • Note
    Yes, upper-case FEDORAPROJECT.ORG — that's the convention for Kerberos.

    You can set default_realm = FEDORAPROJECT.ORG at libdefaults section to avoid each typing @FEDORAPROJECT.ORG

  • Enter your FAS password
    • Note
    You should now be able to authenticate to supported services (koji and lookaside upload)

    Tickets are valid for 24 hours and can be renewed for 1 week.

    You can renew a existing ticket with kinit -R <username>@FEDORAPROJECT.ORG
  • If you are using two-factor authentication (AKA OTP) you need to do init your kerberos ticket with 
    kinit -n @FEDORAPROJECT.ORG -c FILE:${HOME}/armor.ccache
kinit -T FILE:${HOME}/armor.ccache <username>@FEDORAPROJECT.ORG

    When prompted for Enter OTP Token Value:, you should actually enter password+OTP. More information on Fedora Accounts documentation.

  • Store your FAS username (all lower case) in ~/.fedora.upn (This is not actually needed for Kerberos but for other tools that used the Fedora client certificate to determine the FAS username)
    • Note
    You need to do this regularly whenever fedpkg or koji authentication fail. There is no support for these tools to prompt you automatically when the ticket expired.

GUI (gnome/workstation)

  • Open settings -> Online Accounts -> Click on the + to add an account -> Click on "Other" at the end of the list -> Click on "Enterprise login (kerberos)"
  • Enter your FAS name @FEDORAPROJECT.ORG for the principal, e.g. fas@FEDORAPROJECT.ORG.
  • Enter your password when prompted.

Firefox

If you have Firefox 49 or higher and not tweaked any special configuration, you are done. If you have a lower version or want to check:

  • Go to about:config
  • Click the "I accept the risk" button
  • Search for "network.negotiate-auth.trusted-uris"
  • Double-click this option if it's not set to "https://", and set it to "https://"

Chromium/Chrome

For Chrome/Chromium, you need to create a policy file.

  • For Chromium, the directory to put this in is /etc/chromium/policies/managed/ .
  • For Chrome, the directory is /etc/opt/chrome/policies/managed/ (you might have to create this yourself).

In that, create a file (e.g. fedora_kerberos.json), with contents: 

{
	"AuthServerWhitelist": "*.fedoraproject.org",
	"AuthNegotiateDelegateWhitelist": "*.fedoraproject.org"
}


For Mac Chrome/Chromium, you need to enter command 


	sudo defaults write /Library/Preferences/com.google.Chrome.plist AuthServerWhitelist '.fedoraproject.org'
	sudo defaults write /Library/Preferences/com.google.Chrome.plist AuthNegotiateDelegateWhitelist '.fedoraproject.org'
Note
For Chrome/Chromium > 86 the policy parameter names are AuthServerAllowlist and AuthNegotiateDelegateAllowlist.

Questions and Answers

Is there any particular format for username / domain I need to use?

Yes. Your username should be all lower case, and the domain name should be all UPPER CASE. ie, username@FEDORAPROJECT.ORG

How can I see how long my ticket(s) are valid for?

use klist -A

I don't seem to be logged into the koji web interface after this, why not?

Logging into the koji web interface doesn't really get you much of anything, but you can get a valid ticket and then go to https://koji.fedoraproject.org/koji/login in your browser and you will be logged in.

When I run kinit I get Client 'yourname@FEDORAPROJECT.ORG' not found in Kerberos database while getting initial credentials

Login to Fedora Accounts and then retry. Your information needs to be synced from Fedora Accounts to the IPA server. Logging into FAS does so.

I did that (logged into Fedora Accounts) in the last answer, and it didn't help, I still get the same error message. What's going on?

For some small number of users there may be some issue with syncing information from Fedora Accounts->ipa. If this happens to you, please file an infrastructure ticket or talk with us on #fedora-admin[?] and we can manually fix things.

It's not working for me, how can I gather debugging information?

Run the command with KRB5_TRACE=/dev/stdout in front of it and it should print a lot of debugging information.

koji and/or fedpkg don't seem to be working for me.

Make sure you have upgraded to the versions listed above and also make sure you fold changes from /etc/koji.conf.rpmnew (if you ever modified your /etc/koji.conf) and your ~/.koji/config. Note that in normal operation you can just use the stock /etc/koji.conf from the koji package and there is no need for a ~/.koji/config. If it still doesn't work also check /etc/rpkg/fedpkg.conf.rpmnew and update your old config if it exists.

Where should I report problems or get help?

#fedora-admin[?] on IRC or file a fedora-infrastructure ticket and we will try and assist you!

I get kinit: Cannot find KDC for realm "FEDORAPROJECT.ORG" while getting initial credentials

Try adding "includedir /etc/krb5.conf.d/" as the top line in the /etc/krb5.conf file

I get kinit: KDC can't fulfill requested option while renewing credentials

When getting the initial ticket, use kinit -r <secs> to get a renewable ticket. Or add "renew_lifetime = <lifetime>", where <lifetime> is for example 7d, to the [libdefaults] section of /etc/krb5.conf.

After entering my password I get: Password incorrect while getting initial credentials

Please make sure you enter your correct password. If you are sure you entered the correct password, but it doesn't work, please visit the Fedora Accounts and log in and change your password. NOTE: Resetting your password does *NOT* update the Kerberos password. If you forgot your password, first use the password reset feature and then log in again to Fedora Accounts and use the change password link.

Using Koji, I get an error ImportError: Please install python-krbV to use kerberos

Please make sure that in /etc/krb5.conf, under [libdefaults], the option "rdns = false" is set. Note that this might break some non-Fedora krb5 services, but this is required to make GSSAPI work against Fedora services.

I'm on a windows machine and I get a pop up window asking me for login and password and no matter what I enter there it doesn't work. Whats going on?

This is windows seeing that you have a kerberos ticket and trying to authenticate as if it was a active directory setup. This will not work at all. When you get a windows authentication pop up, press 'cancel' and you should instead see the fedoraproject login/pass in the web browser page, enter your information here and you should authenticate.

Extra info for Infrastructure people

To access nagios, you need to use Kerberos as well.

  • This will require you to change /etc/krb5.conf, and under [libdefaults] add or set "rdns = false" and "dns_canonicalize_hostname = false".
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