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Merge pull request #421 from YunoHost/add-certmanager-doc
[enh] Add documentation / FAQ about certificate management in yunohost
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Laurent Peuch
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certmanager.md
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certmanager.md
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Certificate management
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======================
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Managing certificates with Yunohost
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-----------------------------------
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The main feature of the certificate manager is to allow you to install Let's
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Encrypt certificate on your domains without pain. You can use it from the web
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administration (*SSL certificate* on a given domain info page), or from the
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command line with `yunohost domain cert-status`, `cert-install` and
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`cert-renew`.
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#### What is required to be able to have a Let's Encrypt certificate ?
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Your server needs to be reachable from the rest of Internet on port 80 (and
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443), and make your `domain.tld` points to your server's public IP in your DNS
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configuration. See [this documentation](hdiagnostic) if you need help.
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#### Will my certificate be automatically be renewed ?
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Yes. Right now, Let's Encrypt certificates are valid 90 days. A cron job will
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run every day and attempt to renew any certificate that will expire in less than
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15 days. An email will be sent to the root user if a renewal fails.
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#### I want/need to use a certificate from a different CA than Let's Encrypt.
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This cannot be done automatically for now. You will need to manually create a
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Certificate Signing Request (CSR) to be given to your CA, and manually import
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the certificate you get from it. Check out [this page](certificate) for more
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info. This process might be made easier by Yunohost in the future.
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Migration procedure
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--------------------
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> Because of the current [rate limits](https://letsencrypt.org/docs/rate-limits/)
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on new Let's Encrypt certificate emissions, we recommend that you **do not
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migrate** to the new built-in management feature **as long as you don't need to**.
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This is especially true for nohost.me / noho.st users (and other domains services
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sharing a common subdomain). If too many people migrate during the same period
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of time, you might get stuck with a self-signed certificate for a few days !
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#### I used the *letsencrypt_ynh* app
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You will be asked to uninstall the app before being able to use the new
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management feature. You can do it from the web administration interface, or from
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the command line with :
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```bash
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yunohost app remove letsencrypt
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yunohost domain cert-install
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```
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Be aware that the first command will revert your domains to self-signed
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certificate. The second command will attempt to reinstall a Let's Encrypt
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certificate on all your domains which have a self-signed certificate.
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#### I manually installed my Let's Encrypt certificates
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You should go in your nginx configuration, and remove the `letsencrypt.conf` (or
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whatever you called the file containing the `location
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'/.well-known/acme-challenge'` block) for each of your domains. Remove your
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certificate renewer cron job in `/etc/cron.weekly/`, and backup and remove your
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`/etc/letsencrypt/` folder.
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Then run :
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```bash
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yunohost domain cert-install your.domain.tld --force
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```
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for each of your domains you want a Let's Encrypt certificate.
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Troubleshooting
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---------------
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#### Admin interfaces says the letsencrypt app is installed, but it's not, and I can't access the certificate management interface !
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Make sure you refresh the cache of your browser (Ctrl + Shift + R on Firefox),
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and report the issue on the forum or on the bugtracker. You can work around the
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issue by using `yunohost domain cert-install your.domain.tld` from the command
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line.
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#### I tried to uninstall the letsencrypt app, but it broke my nginx conf !
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Sorry about that. Some user reported that this happens when the uninstallation
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script fails to find a backup of your self-signed certificate. Running `yunohost
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domain cert-install` should work anyway...
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#### I get "Too many certificates already issued", what's happening ?
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Currently, Let's Encrypt has a rate limit of issuing no more than 20 new
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certificates by period of 7 days for a given subdomains. For example, `nohost.me`
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and `noho.st` are already considered as subdomains themselves, meaning all users
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of the nohost.me / noho.st service share the same common limit. According to
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Let's Encrypt, this applies for *new* certificates, but not for renewals or
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duplicates. If you encounter this limit, there isn't much to do except retrying
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a few days later.
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#### Certificate installation fails, says "Wrote file to 'some path', but couldn't download 'some url'" !
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This should be fixed in the future, but for now you might need to manually add the
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following line in your `/etc/hosts` :
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```bash
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127.0.0.1 your.domain.tld
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```
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About certificates and Let's Encrypt
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------------------------------------
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#### What is HTTPS ? What's the point of SSL certificates ?
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HTTPS is the secure version of the HTTP protocol, which describes how a client
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(e.g. a web browser) and a server (e.g. nginx running on your Yunohost
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instance) can talk to each other. HTTPS heavily relies on [asymmetric
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cryptography](https://en.wikipedia.org/wiki/Public-key_cryptography) to achieve
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two things :
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- confidentiality, meaning that an attacker will not be able to decrypt the content of the communication if it is intercepted ;
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- server's identification, meaning that a server can prove he is who it says it is, thus protecting against [man-in-the-middle attacks](https://en.wikipedia.org/wiki/Man-in-the-middle_attack).
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SSL certificates is the technology used for server to prove their identity. The
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whole process relies on trust in third parties called Certification Authorities
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(CA), whose role is to verify the server identity (e.g. that a given machine
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effectively controls the domain `ilikecoffee.com`) before delivering
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[cryptographic certificates](https://en.wikipedia.org/wiki/Public_key_certificate).
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#### Why do browsers complain about self-signed certificates ?
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Self-signed certificates are, as their name says, self-signed, meaning that you
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were your own certification authority in the process. Such a certificate does
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not allow to verify your server's identity, since it could have easily been
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generated by an attacker on its own, attempting to perform man-in-the-middle
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attacks.
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#### What's up with Let's Encrypt ?
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Historically, the process of verifying the identity of a server often required
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human intervention, time and money.
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In 2015, Let's Encrypt, developped a protocol called
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[ACME](https://en.wikipedia.org/wiki/Automated_Certificate_Management_Environment),
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which allows to automatically verify that a machine controls a domain, and deliver
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certificates for free, drastically reducing the cost of setting up a SSL
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certificate.
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#### How does Let's Encrypt works ?
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To verify your server's identity and deliver the certificate, Let's Encrypt uses
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the [ACME
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protocol](https://en.wikipedia.org/wiki/Automated_Certificate_Management_Environment). It
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basically works as follow (it's simplified, but you'll get the idea) :
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- A program running on your server contacts the Let's Encrypt CA server, ask for
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a certificate for domain `ilikecoffee.com`.
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- The Let's Encrypt CA server generates a random string such as `A84F2D0B`, and
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tells the program on your server to prove it operates the domain
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`ilikecoffee.com` by making the URI `http://ilikecoffee.com/.well-known/acme-challenge/A84F2D0B`
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accessible.
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- The program on your server edit/creates files accordingly.
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- The Let's Encrypt CA server attempt to access the URI. If it works, then it
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concludes the program indeed operates the domain `ilikecoffee.com`. It
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delivers a certificate.
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- The program on your server obtains the certificate and setups it.
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#### Do we really need Certification Authorities ?
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The reliance on Certification Authorities can be criticized, as they represent
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points of failure in the security scheme. Some trusted CAs have been found to
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issue rogue certificates in the past, sometimes with critical implications
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[[1](http://www.darkreading.com/endpoint/authentication/fake-google-digital-certificates-found-and-confiscated/d/d-id/1297165),
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[2](https://reflets.info/microsoft-et-ben-ali-wikileaks-confirme-les-soupcons-d-une-aide-pour-la-surveillance-des-citoyens-tunisiens/)].
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Alternatives have been proposed, such as
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[DANE/DNSSEC](https://en.wikipedia.org/wiki/DNS-based_Authentication_of_Named_Entities),
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which is based on the DNS system does not require certification authorities.
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