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-# MSC 1711 Certificates FAQ
-
-The goal of Synapse 0.99.0 is to act as a stepping stone to Synapse 1.0.0. It
-supports the r0.1 release of the server to server specification, but is
-compatible with both the legacy Matrix federation behaviour (pre-r0.1) as well
-as post-r0.1 behaviour, in order to allow for a smooth upgrade across the
-federation.
-
-The most important thing to know is that Synapse 1.0.0 will require a valid TLS
-certificate on federation endpoints. Self signed certificates will not be
-sufficient.
-
-Synapse 0.99.0 makes it easy to configure TLS certificates and will
-interoperate with both >= 1.0.0 servers as well as existing servers yet to
-upgrade.
-
-It is critical that all admins upgrade to 0.99.0 and configure a valid TLS
-certificate. Admins will have 1 month to do so, after which 1.0.0 will be
-released and those servers without a valid certificate will not longer be able
-to federate with >= 1.0.0 servers.
-
-If you are unable to generate a valid TLS certificate for your server (e.g.
-because you run it on behalf of someone who doesn't want to give you a TLS
-certificate for their domain, or simply because the matrix domain is hosted on
-a different server), then you can now create a /.well-known/matrix/server file
-on the matrix domain in order to delegate Matrix hosting to another domain.
- Admins who currently use SRV records to delegate a domain which they do not
-control TLS for will need to switch to using .well-known/matrix/server - though
-they should retain their SRV record while the federation upgrades over the
-course of the month.  Other SRV records are unaffected.
-
-Full upgrade notes can be found in
-[UPGRADE.rst](https://github.com/matrix-org/synapse/blob/master/UPGRADE.rst),
-what follows is a timeline and some frequently asked questions.
-
-## Contents
-* Timeline
-* Synapse 0.99.0 has just been released, what do I need to do right now?
-* How do I upgrade?
-* What will happen if I do not set up a valid federation certificate
-  immediately?
-* What will happen if I do nothing at all?
-* When do I need a SRV record or .well-known URI?
-* Can I still use an SRV record?
-* I have created a .well-known URI. Do I still need an SRV record?
-* It used to work just fine, why are you breaking everything?
-* Can I manage my own certificates rather than having Synapse renew
-  certificates itself?
-* Do you still recommend against using a reverse-proxy on the federation port?
-* Do I still need to give my TLS certificates to Synapse if I am using a
-  reverse-proxy?
-* Do I need the same certificate for the client and federation port?
-* How do I tell Synapse to reload my keys/certificates after I replace them?
-
-
-### Timeline
-
-5th Feb 2019  - Synapse 0.99.0 is released.
-
-All server admins are encouraged to upgrade.
-
-0.99.0:
-
--   provides support for ACME to make setting up Let's Encrypt certs easy, as
-    well as .well-known support.
-
--   does not enforce that a valid CA cert is present on the federation API, but
-    rather makes it easy to set one up.
-
--   provides support for .well-known
-
-Admins should upgrade and configure a valid CA cert. Homeservers that require a
-.well-known entry (see below), should retain their SRV record and use it
-alongside their .well-known record.
-
->= 5th March 2019  - Synapse 1.0.0 is released
-
-1.0.0 will land no sooner than 1 month after 0.99.0, leaving server admins one
-month after 5th February to upgrade to 0.99.0 and deploy their certificates. In
-accordance with the the [S2S spec](https://matrix.org/docs/spec/server_server/r0.1.0.html)
-1.0.0 will enforce federation checks. This means that any homeserver without a
-valid certificate after this point will no longer be able to federate with
-1.0.0 servers.
-
-### Synapse 0.99.0 has just been released, what do I need to do right now?
-
-Upgrade as soon as you can in preparation for Synapse 1.0.0.
-
-### How do I upgrade?
-
-Follow the upgrade notes here XXX
-
-### What will happen if I do not set up a valid federation certificate immediately?
-
-Nothing initially, but once 1.0.0 is in the wild it will not be possible to
-federate with 1.0.0 servers.
-
-### What will happen if I do nothing at all?
-
-If the admin takes no action at all, and remains on a Synapse < 0.99.0 then the
-homeserver will be unable to federate with those who have implemented
-.well-known. Then, as above, once the month upgrade window has expired the
-homeserver will not be able to federate with any Synapse >= 1.0.0
-
-### When do I need a SRV record or .well-known URI?
-
-If your homeserver listens on the default federation port (8448), and your
-server_name points to the host that your homeserver runs on, you do not need an
-SRV record or .well-known/matrix/server URI.\
-For instance, if you registered example.com and pointed its DNS A record at a
-fresh Upcloud VPS or similar, you could install Synapse 0.99 on that host,
-giving it a server_name of example.com, and it would automatically generate a
-valid TLS certificate for you via Let's Encrypt and no SRV record or
-.well-known URI would be needed.
-
-This is the common case, although you can add an SRV record or
-.well-known/matrix/server URI for completeness if you wish.
-
-However, if your server does not listen on port 8448, or if your server_name
-does not point to the host that your homeserver runs on, you will need to let
-other servers know how to find it.
-
-The easiest way to do this is with a .well-known/matrix/server URI on the
-webroot of the domain to advertise your server. For instance, if you ran
-"matrixhosting.com" and you were hosting a Matrix server for example.com, you
-would ask example.comto create a file at:
-
-`<https://example.com/.well-known/matrix/server>`
-
-with contents:
-
-`{"m.server": "example.matrixhosting.com:8448"}`
-
-...which would tell servers trying to connect to example.com to instead connect
-to example.matrixhosting.com on port 8448. You would then configure Synapse
-with a server_name of "example.com", but generate a TLS certificate for
-example.matrixhosting.com.
-
-As an alternative, you can still use an SRV DNS record for the delegation, but
-this will require you to have a certificate for the matrix domain (example.com
-in this example). See "Can I still use an SRV record?".
-
-### Can I still use an SRV record?
-
-Firstly, if you didn't need an SRV record before (because your server is
-listening on port 8448 of your server_name), you certainly don't need one now:
-the defaults are still the same.
-
-If you previously had an SRV record, you can keep using it provided you are
-able to give Synapse a TLS certificate corresponding to your server name. For
-example, suppose you had the following SRV record, which directs matrix traffic
-for example.com to matrix.example.com:443:
-
-_matrix._tcp.example.com. IN SRV 10 5 443 matrix.example.com
-
-In this case, Synapse must be given a certificate for example.com - or be
-configured to acquire one from Let's Encrypt.
-
-If you are unable to give Synapse a certificate for your server_name, you will
-also need to use a .well-known URI instead. However, see also "I have created a
-.well-known URI. Do I still need an SRV record?".
-
-### I have created a .well-known URI. Do I still need an SRV record?
-
-As of Synapse 0.99, Synapse will first check for the existence of a .well-known
-URL and follow any delegation it suggests. It will only then check for the
-existence of an SRV record.
-
-That means that the SRV record will often be redundant. However, you should
-remember that there may still be older versions of Synapse in the federation
-which do not understand .well-known URIs, so if you removed your SRV record you
-would no longer be able to federate with them.
-
-It is therefore best to leave the SRV record in place for now. Synapse 0.34 and
-earlier will follow the SRV record (and not care about the invalid
-certificate). Synapse 0.99 and later will follow the .well-known URI, with the
-correct certificate chain.
-
-### It used to work just fine, why are you breaking everything?
-
-We have always wanted Matrix servers to be as easy to set up as possible, and
-so back when we started federation in 2014 we didn't want admins to have to go
-through the cumbersome process of buying a valid TLS certificate to run a
-server. This was before Let's Encrypt came along and made getting a free and
-valid TLS certificate straightforward. So instead, we adopted a system based on
-[Perspectives](https://en.wikipedia.org/wiki/Convergence_(SSL)): an approach
-where you check a set of "notary servers" (in practice, homeservers) to vouch
-for the validity of a certificate rather than having it signed by a CA. As long
-as enough different notaries agree on the certificate's validity, then it is
-trusted.
-
-However, in practice this has never worked properly. Most people only use the
-default notary server (matrix.org), leading to inadvertent centralisation which
-we want to eliminate. Meanwhile, we never implemented the full consensus
-algorithm to query the servers participating in a room to determine consensus
-on whether a given certificate is valid. This is fiddly to get right
-(especially in face of sybil attacks), and we found ourselves questioning
-whether it was worth the effort to finish the work and commit to maintaining a
-secure certificate validation system as opposed to focusing on core Matrix
-development.
-
-Meanwhile, Let's Encrypt came along in 2016, and put the final nail in the
-coffin of the Perspectives project (which was already pretty dead). So, the
-Spec Core Team decided that a better approach would be to mandate valid TLS
-certificates for federation alongside the rest of the Web. More details can be
-found in
-[MSC1711](https://github.com/matrix-org/matrix-doc/blob/master/proposals/1711-x509-for-federation.md#background-the-failure-of-the-perspectives-approach).
-
-This results in a breaking change, which is disruptive, but absolutely critical
-for the security model. However, the existence of Let's Encrypt as a trivial
-way to replace the old self-signed certificates with valid CA-signed ones helps
-smooth things over massively, especially as Synapse can now automate Let's
-Encrypt certificate generation if needed.
-
-### Can I manage my own certificates rather than having Synapse renew certificates itself?
-
-Yes, you are welcome to manage your certificates yourself. Synapse will only
-attempt to obtain certificates from Let's Encrypt if you configure it to do
-so.The only requirement is that there is a valid TLS cert present for
-federation end points.
-
-### Do you still recommend against using a reverse-proxy on the federation port?
-
-We no longer actively recommend against using a reverse proxy. Many admins will
-find it easier to direct federation traffic to a reverse-proxy and manage their
-own TLS certificates, and this is a supported configuration.
-
-Do I still need to give my TLS certificates to Synapse if I am using a
-reverse-proxy?
-
-Practically speaking, this is no longer necessary.
-
-If you are using a reverse-proxy for all of your TLS traffic, then you can set
-`no_tls: True`. In that case, the only reason Synapse needs the certificate is
-to populate a legacy 'tls_fingerprints' field in the federation API. This is
-ignored by Synapse 0.99.0 and later, and the only time pre-0.99 Synapses will
-check it is when attempting to fetch the server keys - and generally this is
-delegated via `matrix.org`, which is on 0.99.0.
-
-However, there is a bug in Synapse 0.99.0
-[4554](<https://github.com/matrix-org/synapse/issues/4554>) which prevents
-Synapse from starting if you do not give it a TLS certificate. To work around
-this, you can give it any TLS certificate at all. This will be fixed soon.
-
-### Do I need the same certificate for the client and federation port?
-
-No. There is nothing stopping you doing so, particularly if you are using a
-reverse-proxy. However, Synapse will use the same certificate on any ports
-where TLS is configured.
-
-### How do I tell Synapse to reload my keys/certificates after I replace them?
-
-Synapse will reload the keys and certificates when it receives a SIGHUP - for
-example kill -HUP $(cat homeserver.pid). Alternatively, simply restart Synapse,
-though this will result in downtime while it restarts.
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