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Blog post for filesystem integrity
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---
layout: post
title: "Enabling Integrity on Filesystem realms"
date: 2022-06-08
tags: filesystem-realm integrity
synopsis: An overview of the new support for filesystem realm integrity verification.
author: araskar
link:
---

Previously, any data in the filesystem realm was not verified, this meant that anyone with access to the identity files, could tamper with the data without any way of knowing. Now filesystem integrity has been added by generating a signature through the use of a public-private key pair.

== An overview of the new attributes

The filesystem realm now supports the following attributes

* ``key-store``: This attribute specifies the key store resource where the key pair resides in. This key store must be configured prior to creating the filesystem realm. This attribute is optional and if not specified, the filesystem realm will not verify its integrity.

* ``key-store-alias``: This attribute specifies the alias to the key pair in the key store to verify filesystem integrity. This attribute is required if the `key-store` attribute is specified.

== A Complete Example

In this post we go through an example of setting up a filesystem realm with integrity enabled on a web application.

=== Example Project
Clone the ``elytron-examples`` repo locally:

[source]
----
git clone https://github.com/wildfly-security-incubator/elytron-examples
cd elytron-examples
----
We'll be looking at the *https://github.com/wildfly-security-incubator/elytron-examples/blob/master/integrity-filesystem-realm[integrity-filesystem-realm]*

=== Server Configuration
In the following section, we will review the configuration available in the script for the quickstart
*https://github.com/wildfly-security-incubator/elytron-examples/blob/master/integrity-filesystem-realm/configure-elytron.cli[configure-elytron.cli]*. We start our configuration by connecting to the server using the following command:

[source,shell]
----
$ WILDFLY_HOME/bin/jboss-cli.sh --connect
----
==== Note: Use of WILDFLY_HOME
In the following post, replace ``WILDFLY_HOME`` with the actual path to your WildFly installation.

We first create a keystore and keypair under the Elytron subsystem, with the name ``keystore``, and alias ``user``.
[source]
----
/subsystem=elytron/key-store=keystore:add(path=keystore, relative-to=jboss.server.config.dir, type=JKS, credential-reference={clear-text=secret})
/subsystem=elytron/key-store=keystore:generate-key-pair(alias=user,algorithm=RSA,key-size=1024,validity=365,distinguished-name="CN=localhost")
/subsystem=elytron/key-store=keystore:store()
----


Then we create a filesystem realm under the Elytron subsystem using the key-store and key-store-alias specified above. We then add an identity ``quickstartUser``, setting a digest password and adding the
attributes ``Guest`` and ``Admin`` as follows:
[source]
----
/subsystem=elytron/filesystem-realm=fsRealm:add(path=fs-realm,relative-to=jboss.server.config.dir, key-store=keystore, key-store-alias=user)
/subsystem=elytron/filesystem-realm=fsRealm:add-identity(identity=quickstartUser)
/subsystem=elytron/filesystem-realm=fsRealm:set-password(digest={algorithm=digest-md5, realm=fsRealm, password=password123!}, identity=quickstartUser)
/subsystem=elytron/filesystem-realm=fsRealm:add-identity-attribute(identity=quickstartUser, name=Roles, value=["Admin", "Guest"])
----

For more information about creating FileSystem realms along with all of its possible configurations,
please refer to the https://docs.wildfly.org/26/WildFly_Elytron_Security.html[Elytron documentation].

We then configure a simple role decoder and create a new security domain which will make use of our
filesystem realm and role decoder as follows:
[source]
----
/subsystem=elytron/simple-role-decoder=from-roles-attribute:add(attribute=Roles)
/subsystem=elytron/security-domain=fsDomain:add(realms=[{realm=fsRealm, role-decoder=from-roles-attribute}], default-realm=fsRealm,permission-mapper=default-permission-mapper)
----


NOTE: Creating an additional security domain (``fsDomain``in this case) is not necessary.
We could alternatively take the default ``ApplicationDomain`` and add the
FileSystem realm and role-decoder to it.

We then add our security domain mapping to the Undertow subsystem:

[source]
----
/subsystem=undertow/application-security-domain=other:write-attribute(name=security-domain, value=fsDomain)
----


=== Deploying to app to WildFly

From the root directory of the *https://github.com/wildfly-security-incubator/elytron-examples/blob/master/integrity-filesystem-realm/[quickstart example]* run the following command the deploy the web application to wildfly
[source]
----
mvn clean install wildfly:deploy
----

=== Verifying Integrity
Now you may navigate to ``http://localhost:8080/integrity-filesystem``, and when it prompt's you to enter a username and password, put in the credentials we specified earlier, ``quickstartUser``, and ``password123!``. This should authenticate you to a page that shows you the principal you're logged in with.

The successful login indicates that integrity has been configured correctly.

In order to further verify that these features are being used correctly we can navigate to the identity file and check the contents. The file should be located at ``WILDFLY_HOME/standalone/configuration/fs-realm/q/u/quickstartuser-OF2WSY3LON2GC4TUKVZWK4Q.xml`` if the same filesystem realm and identity configuration was used.

In the identity we can see there is now a ``<principal />`` tag specifying the principal name, to ensure it matches with the file name, as well as a ``<Signature>`` tag.

The format for the signature tag should look like the following

[xml]
----
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#"><SignedInfo><CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/><SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/><Reference URI=""><Transforms><Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/></Transforms><DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><DigestValue>ArpOOvSwrygVhHqyHYZb/y8R5Hn8CFRfpTliiHQEyA=</DigestValue></Reference></SignedInfo><SignatureValue>RWl3Tt1iYuJD1Sj8MeCIYkB3W1j+gNzMoHZ1nAMZaDtWIf9pJApf84L0bihM9+cUeHaNnJjjic8T&#13;
tx+EwwYKF2liZXbOlM8QBV6H2ODX1pYHjFfVDEoqI8oY8egP2nPNLxREp/kmNiWJGeLnHibYapZ7&#13;
RjJG7r21+yeCvni4rLc=</SignatureValue><KeyInfo><KeyValue><RSAKeyValue><Modulus>jKCHruUkqzCrXhvKBPGv98I5zZsWxcWE+1gz4EqIv5EHlKv8rvfaLnhlQIxwIe0uB6Tfa2M3NKjE&#13;
RBsL7AH5R3T4h9ht8rdRcZfVZlq55d/dqvZv+QHDwzy2bMY2s/+1E3nF95CmGTa4uf0zm3WYOs1K&#13;
0iLzGzkyPT1JZSa0gRU=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue></KeyValue></KeyInfo></Signature>
----

== Summary
This blog post has given an overview on how to configure a filesystem realm to enable integrity support.

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