### Security fix: OIDC changes in Headscale 0.24.0
_Headscale v0.23.0 and earlier_ identified OIDC users by the "username" part of their email address (when `strip_email_domain: true`, the default) or whole email address (when `strip_email_domain: false`).
Depending on how Headscale and your Identity Provider (IdP) were configured, only using the `email` claim could allow a malicious user with an IdP account to take over another Headscale user's account, even when `strip_email_domain: false`.
This would also cause a user to lose access to their Headscale account if they changed their email address.
_Headscale v0.24.0_ now identifies OIDC users by the `iss` and `sub` claims. [These are guaranteed by the OIDC specification to be stable and unique](https://openid.net/specs/openid-connect-core-1_0.html#ClaimStability), even if a user changes email address. A well-designed IdP will typically set `sub` to an opaque identifier like a UUID or numeric ID, which has no relation to the user's name or email address.
This issue _only_ affects Headscale installations which authenticate with OIDC.
Headscale v0.24.0 and later will also automatically update profile fields with OIDC data on login. This means that users can change those details in your IdP, and have it populate to Headscale automatically the next time they log in. However, this may affect the way you reference users in policies.
#### Migrating existing installations
Headscale v0.23.0 and earlier never recorded the `iss` and `sub` fields, so all legacy (existing) OIDC accounts from _need to be migrated_ to be properly secured.
Headscale v0.24.0 has an automatic migration feature, which is enabled by default (`map_legacy_users: true`). **This will be disabled by default in a future version of Headscale – any unmigrated users will get new accounts.**
Headscale v0.24.0 will ignore any `email` claim if the IdP does not provide an `email_verified` claim set to `true`. [What "verified" actually means is contextually dependent](https://openid.net/specs/openid-connect-core-1_0.html#StandardClaims) – Headscale uses it as a signal that the contents of the `email` claim is reasonably trustworthy.
Headscale v0.23.0 and earlier never checked the `email_verified` claim. This means even if an IdP explicitly indicated to Headscale that its `email` claim was untrustworthy, Headscale would have still accepted it.
##### What does automatic migration do?
When automatic migration is enabled (`map_legacy_users: true`), Headscale will first match an OIDC account to a Headscale account by `iss` and `sub`, and then fall back to matching OIDC users similarly to how Headscale v0.23.0 did:
- If `strip_email_domain: true` (the default): the Headscale username matches the "username" part of their email address.
- If `strip_email_domain: false`: the Headscale username matches the _whole_ email address.
On migration, Headscale will change the account's username to their `preferred_username`. **This could break any ACLs or policies which are configured to match by username.**
Like with Headscale v0.23.0 and earlier, this migration only works for users who haven't changed their email address since their last Headscale login.
A _successful_ automated migration should otherwise be transparent to users.
Once a Headscale account has been migrated, it will be _unavailable_ to be matched by the legacy process. An OIDC login with a matching username, but _non-matching_`iss` and `sub` will instead get a _new_ Headscale account.
Because of the way OIDC works, Headscale's automated migration process can _only_ work when a user tries to log in after the update. Mass updates would require Headscale implement a protocol like SCIM, which is **extremely** complicated and not available in all identity providers.
Administrators could also attempt to migrate users manually by editing the database, using their own mapping rules with known-good data sources.
Legacy account migration should have no effect on new installations where all users have a recorded `sub` and `iss`.
##### What happens when automatic migration is disabled?
When automatic migration is disabled (`map_legacy_users: false`), Headscale will only try to match an OIDC account to a Headscale account by `iss` and `sub`.
If there is no match, it will get a _new_ Headscale account – even if there was a legacy account which _could_ have matched and migrated.
We recommend new Headscale users explicitly disable automatic migration – but it should otherwise have no effect if every account has a recorded `iss` and `sub`.
When automatic migration is disabled, the `strip_email_domain` setting will have no effect.
Special thanks to @micolous for reviewing, proposing and working with us on these changes.
#### Other OIDC changes
Headscale now uses [the standard OIDC claims](https://openid.net/specs/openid-connect-core-1_0.html#StandardClaims) to populate and update user information every time they log in:
- Loosened up `server_url` and `base_domain` check. It was overly strict in some cases. [#2248](https://github.com/juanfont/headscale/pull/2248)
- CLI for managing users now accepts `--identifier` in addition to `--name`, usage of `--identifier` is recommended [#2261](https://github.com/juanfont/headscale/pull/2261)
This release was intended to be mainly a code reorganisation and refactoring, significantly improving the maintainability of the codebase. This should allow us to improve further and make it easier for the maintainers to keep on top of the project.
However, as you all have noticed, it turned out to become a much larger, much longer release cycle than anticipated. It has ended up to be a release with a lot of rewrites and changes to the code base and functionality of Headscale, cleaning up a lot of technical debt and introducing a lot of improvements. This does come with some breaking changes,
#### Here is a short summary of the broad topics of changes:
Code has been organised into modules, reducing use of global variables/objects, isolating concerns and “putting the right things in the logical place”.
The new [policy](https://github.com/juanfont/headscale/tree/main/hscontrol/policy) and [mapper](https://github.com/juanfont/headscale/tree/main/hscontrol/mapper) package, containing the ACL/Policy logic and the logic for creating the data served to clients (the network “map”) has been rewritten and improved. This change has allowed us to finish SSH support and add additional tests throughout the code to ensure correctness.
The [“poller”, or streaming logic](https://github.com/juanfont/headscale/blob/main/hscontrol/poll.go) has been rewritten and instead of keeping track of the latest updates, checking at a fixed interval, it now uses go channels, implemented in our new [notifier](https://github.com/juanfont/headscale/tree/main/hscontrol/notifier) package and it allows us to send updates to connected clients immediately. This should both improve performance and potential latency before a client picks up an update.
Headscale now supports sending “delta” updates, thanks to the new mapper and poller logic, allowing us to only inform nodes about new nodes, changed nodes and removed nodes. Previously we sent the entire state of the network every time an update was due.
While we have a pretty good [test harness](https://github.com/search?q=repo%3Ajuanfont%2Fheadscale+path%3A_test.go&type=code) for validating our changes, the changes came down to [284 changed files with 32,316 additions and 24,245 deletions](https://github.com/juanfont/headscale/compare/b01f1f1867136d9b2d7b1392776eb363b482c525...ed78ecd) and bugs are expected. We need help testing this release. In addition, while we think the performance should in general be better, there might be regressions in parts of the platform, particularly where we prioritised correctness over speed.
- Change the structure of database configuration, see [config-example.yaml](./config-example.yaml) for the new structure. [#1700](https://github.com/juanfont/headscale/pull/1700)
- Old structure has been remove and the configuration _must_ be converted.
- Embedded DERP server requires a private key [#1611](https://github.com/juanfont/headscale/pull/1611)
- Add a filepath entry to [`derp.server.private_key_path`](https://github.com/juanfont/headscale/blob/b35993981297e18393706b2c963d6db882bba6aa/config-example.yaml#L95)
- Docker images are now built with goreleaser (ko) [#1716](https://github.com/juanfont/headscale/pull/1716) [#1763](https://github.com/juanfont/headscale/pull/1763)
- Entrypoint of container image has changed from shell to headscale, require change from `headscale serve` to `serve`
- MagicDNS domains no longer contain usernames []()
- This is in preperation to fix Headscales implementation of tags which currently does not correctly remove the link between a tagged device and a user. As tagged devices will not have a user, this will require a change to the DNS generation, removing the username, see [#1369](https://github.com/juanfont/headscale/issues/1369) for more information.
-`use_username_in_magic_dns` can be used to turn this behaviour on again, but note that this option _will be removed_ when tags are fixed.
- Use versioned migrations [#1644](https://github.com/juanfont/headscale/pull/1644)
- Make the OIDC callback page better [#1484](https://github.com/juanfont/headscale/pull/1484)
- SSH support [#1487](https://github.com/juanfont/headscale/pull/1487)
- State management has been improved [#1492](https://github.com/juanfont/headscale/pull/1492)
- Use error group handling to ensure tests actually pass [#1535](https://github.com/juanfont/headscale/pull/1535) based on [#1460](https://github.com/juanfont/headscale/pull/1460)
- Fix hang on SIGTERM [#1492](https://github.com/juanfont/headscale/pull/1492) taken from [#1480](https://github.com/juanfont/headscale/pull/1480)
- Send logs to stderr by default [#1524](https://github.com/juanfont/headscale/pull/1524)
- Turn off gRPC logging [#1640](https://github.com/juanfont/headscale/pull/1640) fixes [#1259](https://github.com/juanfont/headscale/issues/1259)
- Added the possibility to manually create a DERP-map entry which can be customized, instead of automatically creating it. [#1565](https://github.com/juanfont/headscale/pull/1565)
- Fix for registering nodes using preauthkeys when running on a postgres database in a non-UTC timezone. [#764](https://github.com/juanfont/headscale/issues/764)
- Make sure integration tests cover postgres for all scenarios
- CLI commands (all except `serve`) only requires minimal configuration, no more errors or warnings from unset settings [#2109](https://github.com/juanfont/headscale/pull/2109)
- CLI results are now concistently sent to stdout and errors to stderr [#2109](https://github.com/juanfont/headscale/pull/2109)
- Fix longstanding bug that would prevent "\*" from working properly in ACLs (issue [#699](https://github.com/juanfont/headscale/issues/699)) [#1279](https://github.com/juanfont/headscale/pull/1279)
- Fix issue where IPv6 could not be used in, or while using ACLs (part of [#809](https://github.com/juanfont/headscale/issues/809)) [#1339](https://github.com/juanfont/headscale/pull/1339)
- Log level option `log_level` was moved to a distinct `log` config section and renamed to `level` [#768](https://github.com/juanfont/headscale/pull/768)
- Add experimental support for [SSH ACL](https://tailscale.com/kb/1018/acls/#tailscale-ssh) (see docs for limitations) [#847](https://github.com/juanfont/headscale/pull/847)
- Please note that this support should be considered _partially_ implemented
- SSH ACLs status:
- Support `accept` and `check` (SSH can be enabled and used for connecting and authentication)
- Rejecting connections **are not supported**, meaning that if you enable SSH, then assume that _all_`ssh` connections **will be allowed**.
- If you decided to try this feature, please carefully managed permissions by blocking port `22` with regular ACLs or do _not_ set `--ssh` on your clients.
- Add -c option to specify config file from command line [#285](https://github.com/juanfont/headscale/issues/285) [#612](https://github.com/juanfont/headscale/pull/601)
- Add configuration option to allow Tailscale clients to use a random WireGuard port. [kb/1181/firewalls](https://tailscale.com/kb/1181/firewalls) [#624](https://github.com/juanfont/headscale/pull/624)
- nodes ls now print both Hostname and Name(Issue [#647](https://github.com/juanfont/headscale/issues/647) PR [#687](https://github.com/juanfont/headscale/pull/687))
-`/metrics` is now a configurable host:port endpoint: [#344](https://github.com/juanfont/headscale/pull/344). You must update your `config.yaml` file to include:
- Reduce the overhead of marshal/unmarshal for Hostinfo, routes and endpoints by using specific types in Machine [#371](https://github.com/juanfont/headscale/pull/371)
- Apply normalization function to FQDN on hostnames when hosts registers and retrieve information [#363](https://github.com/juanfont/headscale/issues/363)
- Add support for configurable mTLS [docs](docs/tls.md#configuring-mutual-tls-authentication-mtls) [#297](https://github.com/juanfont/headscale/pull/297)
- Fixed issue where hosts deleted from control server may be written back to the database, as long as they are connected to the control server [#278](https://github.com/juanfont/headscale/pull/278)
- Add gRPC and HTTP API (HTTP API is currently disabled) [#204](https://github.com/juanfont/headscale/pull/204)
- Use gRPC between the CLI and the server [#206](https://github.com/juanfont/headscale/pull/206), [#212](https://github.com/juanfont/headscale/pull/212)
- Beta OpenID Connect support [#126](https://github.com/juanfont/headscale/pull/126), [#227](https://github.com/juanfont/headscale/pull/227)