= Using Shared System Certificates

The Shared System Certificates storage enables NSS, GnuTLS, OpenSSL, and Java to share a default source for retrieving system certificate anchors and black list information. By default, the trust store contains the Mozilla CA list, including positive and negative trust. The system allows updating of the core Mozilla CA list or choosing another certificate list.


== Using the System-wide Trust Store

In Fedora, the consolidated system-wide trust store is located in the `/etc/pki/ca-trust/` and `/usr/share/pki/ca-trust-source/` directories. The trust settings in `/usr/share/pki/ca-trust-source/` are processed with lower priority than settings in `/etc/pki/ca-trust/`.

Certificate files are treated depending on the subdirectory they are installed to the following directories:

* for trust anchors
** `/usr/share/pki/ca-trust-source/anchors/` or
** `/etc/pki/ca-trust/source/anchors/`
* for distrusted certificates
** `/usr/share/pki/ca-trust-source/blocklist/` or
** `/etc/pki/ca-trust/source/blocklist/`
* for certificates in the extended BEGIN TRUSTED file format
** `/usr/share/pki/ca-trust-source/` or
** `/etc/pki/ca-trust/source/`

NOTE: In a hierarchical cryptographic system, a trust anchor is an authoritative entity which is assumed to be trustworthy. For example, in X.509 architecture, a root certificate is a trust anchor from which a chain of trust is derived. The trust anchor must be put in the possession of the trusting party beforehand to make path validation possible.



== Adding New Certificates

Often, system administrators want to install a certificate into the trust store. This can be done with the [command]`trust anchor` sub-command of the [command]`trust` command, as described in xref:managing-trusted-system-certificates[Managing Trusted System Certificates].

Alternatively, you can simply copy the certificate file in the PEM or DER file format to the `/etc/pki/ca-trust/source/anchors/` directory, followed by running the [command]`update-ca-trust` command, for example:

[subs="+quotes,macros"]
----
# cp _~/certificate-trust-examples/Cert-trust-test-ca.pem_ _/etc/pki/ca-trust/source/anchors/_
----

----
# update-ca-trust
----

The [command]`update-ca-trust` command ensures that the certificate bundles in application-specific formats, such as Java keystore, are regenerated.

[NOTE]
====
The certificates installed in the above steps cannot be removed with the [command]`trust anchor --remove`.
====

[NOTE]
====
While the Firefox browser is able to use an added certificate without executing [command]`update-ca-trust`, it is recommended to run [command]`update-ca-trust` after a CA change. Also note that browsers, such as Firefox, Epiphany, or Chromium, cache files, and you might need to clear the browser's cache or restart your browser to load the current system certificates configuration.
====



== Managing Trusted System Certificates

To list, extract, add, remove, or change trust anchors, use the [command]`trust` command. To see the built-in help for this command, enter it without any arguments or with the [option]`--help` directive:

[subs="quotes, macros"]
----
$ [command]`trust`
usage: trust command <args>...

Common trust commands are:
  list             List trust or certificates
  extract          Extract certificates and trust
  extract-compat   Extract trust compatibility bundles
  anchor           Add, remove, change trust anchors
  dump             Dump trust objects in internal format

See 'trust <command> --help' for more information
----

To list all system trust anchors and certificates, use the [command]`trust list` command:

[subs="quotes, macros"]
----
$ [command]`trust list`
pkcs11:id=%d2%87%b4%e3%df%37%27%93%55%f6%56%ea%81%e5%36%cc%8c%1e%3f%bd;type=cert
    type: certificate
    label: ACCVRAIZ1
    trust: anchor
    category: authority

pkcs11:id=%a6%b3%e1%2b%2b%49%b6%d7%73%a1%aa%94%f5%01%e7%73%65%4c%ac%50;type=cert
    type: certificate
    label: ACEDICOM Root
    trust: anchor
    category: authority
...
[output has been truncated]
----



To store a trust anchor into the system-wide trust store, use the [command]`trust anchor` sub-command and specify a _path.to_ a certificate, for example:

[subs="macros"]
----
# trust anchor pass:quotes[_path.to/certificate.crt_]
----

To remove a certificate, use either a _path.to_ a certificate or an ID of a certificate:

[subs="macros"]
----
# trust anchor --remove pass:quotes[_path.to/certificate.crt_]
# trust anchor --remove pass:quotes[_"pkcs11:id=%AA%BB%CC%DD%EE;type=cert"_]
----

.More information

All sub-commands of the [command]`trust` commands offer a detailed built-in help, for example:

----
$ trust list --help
usage: trust list --filter=<what>

  --filter=<what>     filter of what to export
                        ca-anchors        certificate anchors
                        blacklist         blacklisted certificates
                        trust-policy      anchors and blacklist (default)
                        certificates      all certificates
                        pkcs11:object=xx  a PKCS#11 URI
  --purpose=<usage>   limit to certificates usable for the purpose
                        server-auth       for authenticating servers
                        client-auth       for authenticating clients
                        email             for email protection
                        code-signing      for authenticating signed code
                        1.2.3.4.5...      an arbitrary object id
  -v, --verbose       show verbose debug output
  -q, --quiet         suppress command output
----





== Additional Resources

For more information, see the following man pages:

* `update-ca-trust(8)`
* `trust(1)`