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Measures

An overview of the security measures Authelia implements.

2018-08-26T23:46:15+02:00

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overview

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security

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/docs/security/measures.html

Authelia sets several cookie attributes to help prevent cookie theft:

HttpOnly is set forbidding client-side code like javascript from access to the cookie.
Secure is set forbidding the browser from sending the cookie to sites which do not use the HTTPS scheme.
SameSite is by default set to Lax which prevents it being sent over cross-origin requests.

Read about these attributes in detail on the MDN.

Since Authelia uses multi-domain cookies to perform single sign-on, an attacker who poisoned a user's DNS cache can easily retrieve the user's cookies by making the user send a request to one of the attacker's IPs.

This is technically mitigated by the Secure attribute set in cookies by Authelia, however it's still advisable to only use HTTPS connections with valid certificates and enforce it with HTTP Strict Transport Security (HSTS) which will prevent domains from serving over HTTP at all as long as the user has visited the domain before. This means even if the attacker poisons DNS they are unable to get modern browsers to connect to a compromised host unless they can also obtain the certificate.

Note that using HSTS has consequences and you should do adequate research into understanding HSTS before you enable it. For example the nginx blog has a good article helping users understand it.

Protection against username enumeration

Authelia adaptively delays authentication attempts based on the mean (average) of the previous 10 successful attempts in addition to a small random interval of time. The result of this delay is that it makes it incredibly difficult to determine if the unsuccessful login was the result of a bad password, a bad username, or both. The random interval of time is anything between 0 milliseconds and 85 milliseconds.

When Authelia first starts it assumes the last 10 attempts took 1000 milliseconds each. As users login successfully it quickly adjusts to the actual time the login attempts take. This process is independent of the login backend you have configured.

The cost of this is low since in the instance of a user not existing it just stops processing the request to delay the login. Lastly the absolute minimum time authentication can take is 250 milliseconds. Both of these measures also have the added effect of creating an additional delay for all authentication attempts increasing the time that a brute-force attack will take, this combined with regulation greatly delays brute-force attacks and the effectiveness of them in general.

Protections against password cracking (File authentication provider)

Authelia implements a variety of measures to prevent an attacker cracking passwords if they somehow obtain the file used by the file authentication provider, this is unrelated to LDAP auth.

First and foremost Authelia only uses very secure hashing algorithms with sane and secure defaults. The first and default hashing algorithm we use is Argon2id which is currently considered the most secure hashing algorithm. We also support SHA512, which previously was the default.

Secondly Authelia uses salting with all hashing algorithms. These salts are generated with a random string generator, which is seeded every time it's used by a cryptographically secure 1024bit prime number. This ensures that even if an attacker obtains the file, each password has to be brute forced individually.

Lastly Authelia's implementation of Argon2id is highly tunable. You can tune the key length, salt used, iterations (time), parallelism, and memory usage. To read more about this please read how to configure file authentication.

Protections against return oriented programming attacks and general hardening

Authelia is built as a position independent executable which makes Return Oriented Programming (ROP) attacks significantly more difficult to execute reliably.

In addition it is built as a static binary with full relocation read-only support making this and several other traditional binary weaknesses significantly more difficult to exploit.

User profile and group membership always kept up-to-date (LDAP authentication provider)

This measure is unrelated to the File authentication provider.

Authelia by default refreshes the user's profile and membership every 5 minutes. This ensures that if you alter a users groups in LDAP that their new groups are obtained relatively quickly in order to adjust their access level for applications secured by Authelia.

Additionally, it will invalidate any session where the user could not be retrieved from LDAP based on the user filter, for example if they were deleted or disabled provided the user filter is set correctly. These updates occur when a user accesses a resource protected by Authelia. This means you should ensure disabled users or users with expired passwords are not obtainable using the LDAP filter, the default filter for Active Directory implements this behaviour. LDAP implementations vary, so please ask if you need some assistance in configuring this.

These protections can be tuned according to your security policy by changing refresh_interval, however we believe that 5 minutes is a fairly safe interval.

Storage security measures

We force users to encrypt vulnerable data stored in the database. It is strongly advised you do not give this encryption key to anyone. In the instance of a database installation that multiple users have access to, you should aim to ensure that users who have access to the database do not also have access to this key.

The encrypted data in the database is as follows:

Table	Column	Rational
totp_configurations	secret	Prevents a Leaked Database or Bad Actors from compromising security
webauthn_devices	public_key	Prevents Bad Actors from compromising security
oauth2_authorization_code_session	session_data	Prevents Bad Actors from compromising security
oauth2_access_token_session	session_data	Prevents Bad Actors from compromising security
oauth2_refresh_token_session	session_data	Prevents Bad Actors from compromising security
oauth2_pkce_request_session	session_data	Prevents Bad Actors from compromising security
oauth2_openid_connect_session	session_data	Prevents Bad Actors from compromising security

Leaked Database

A leaked database can reasonably compromise security if there are credentials that are not encrypted. Columns encrypted for this purpose prevent this attack vector.

Bad Actors

A bad actor who has the SQL password and access to the database can theoretically change another users credential, this theoretically bypasses authentication. Columns encrypted for this purpose prevent this attack vector.

A bad actor may also be able to use data in the database to bypass 2FA silently depending on the credentials. In the instance of the U2F public key this is not possible, they can only change it which would eventually alert the user in question. But in the case of TOTP they can use the secret to authenticate without knowledge of the user in question.

Encryption key management

You must supply the encryption key in the recommended method of a secret or in one of the other methods available for configuration.

If you wish to change your encryption key for any reason you can do so using the following steps:

Run the authelia --version command to determine the version of Authelia you're running and either download that version or run another container of that version interactively. All the subsequent commands assume you're running the authelia binary in the current working directory. You will have to adjust this according to how you're running it.
Run the ./authelia storage encryption change-key --help command.
Stop Authelia.
- You can skip this step, however note that any data changed between the time you make the change and the time when you stop Authelia i.e. via user registering a device; will be encrypted with the incorrect key.
Run the ./authelia storage encryption change-key command with the appropriate parameters.
- The help from step 1 will be useful here. The easiest method to accomplish this is with the --config, --encryption-key, and --new-encryption-key parameters.
Update the encryption key Authelia uses on startup.
Start Authelia.

Notifier security measures (SMTP)

The SMTP Notifier implementation does not allow connections that are not secure without changing default configuration values.

As such all SMTP connections require the following:

A TLS Connection (StartTLS or implicit) has been negotiated before authentication or sending emails (unauthenticated connections require it as well)
Valid X509 Certificate presented to the client during the TLS handshake

There is an option to disable both of these security measures however they are not recommended.

The following configuration options exist to configure the security level in order of most preferable to least preferable:

Configuration Option: certificates_directory

You can configure a certificates_directory option which contains certificates for Authelia to trust. These certificates can either be CA's or individual public certificates that should be trusted. These are added in addition to the environments PKI trusted certificates if available. This is useful for trusting a certificate that is self-signed without drastically reducing security. This is the most recommended workaround to not having a valid PKI trusted certificate as it gives you complete control over which ones are trusted without disabling critically needed validation of the identity of the target service.

Read more in the certificates_directory documentation for this option.

Configuration Option: tls.skip_verify

The tls.skip_verify option allows you to skip verifying the certificate entirely which is why certificates directory is preferred over this. This will effectively mean you cannot be sure the certificate is valid which means an attacker via DNS poisoning or MITM attacks could intercept emails from Authelia compromising a user's security without their knowledge.

Configuration Option: disable_require_tls

Authelia by default ensures that the SMTP server connection is secured via TLS prior to sending sensitive information.

The disable_require_tls option disables this requirement which means the emails may be sent in cleartext. This is the least secure option as it effectively removes the validation of SMTP certificates and makes using an encrypted connection with TLS optional.

This means not only can the vulnerabilities of the skip_verify option be exploited, but any router or switch along the route of the email which receives the packets could be used to silently exploit the cleartext nature of the connection to manipulate the email in transit.

This is only usable currently with authentication disabled (comment out the password), and as such is only an option for SMTP servers that allow unauthenticated relaying (bad practice).

SMTP Ports

All SMTP connections begin as cleartext, and then negotiate to upgrade to a secure TLS connection via StartTLS.

The submissions service (typically port 465) is an exception to this rule, where the connection begins immediately secured with TLS (similar to HTTPS). When the configured scheme for SMTP is set to submissions, Authelia will initiate TLS connections without requiring StartTLS negotiation.

When the submissions service port is available, it should be preferred over any StartTLS port for submitting mail.

NOTE: Prior to 2018, port 465 was previously assigned for a similar purpose known as smtps (A TLS only equivalent of the smtp port 25), which it had been deprecated for. Port 465 has since been re-assigned for only supporting mail submission (which unlike SMTP transfers via port 25, requires authentication), similar to port 587 (the submission port, a common alternative that uses StartTLS instead).

Protection against open redirects

Authelia protects your users against open redirect attacks by always checking if redirection URLs are pointing to a subdomain of the domain protected by Authelia. This prevents phishing campaigns tricking users into visiting infected websites leveraging legit links.

Mutual TLS

For the best security protection, configuration with TLS is highly recommended. TLS is used to secure the connection between the proxies and Authelia instances meaning that an attacker on the network cannot perform a man-in-the-middle attack on those connections. However, an attacker on the network can still impersonate proxies but this can be prevented by configuring mutual TLS.

Mutual TLS brings mutual authentication between Authelia and the proxies. Any other party attempting to contact Authelia would not even be able to create a TCP connection. This measure is recommended in all cases except if you already configured some kind of ACLs specifically allowing the communication between proxies and Authelia instances like in a service mesh or some kind of network overlay.

To configure mutual TLS, please refer to this document

Additional security

Reset Password

It's possible to disable the reset password functionality and is an optional adjustment to consider for anyone wanting to increase security. See the configuration for more information.

Session security

We have a few options to configure the security of a session. The main and most important one is the session secret. This is used to encrypt the session data when it is stored in the Redis key value database. The value of this option should be long and as random as possible. See more in the documentation for this option.

The validity period of session is highly configurable. For example in a highly security conscious domain you could set the session remember_me to 0 to disable this feature, and set the expiration to 2 hours and the inactivity of 10 minutes. Configuring the session security in this manner would mean if the cookie age was more than 2 hours or if the user was inactive for more than 10 minutes the session would be destroyed.

Response Headers

This document previously detailed additional per-proxy configuration options that could be utilized in a proxy to improve security. These headers are now documented here and implemented by default in all responses due to the fact the experience should be the same regardless of which proxy you're utilizing and the area is rapidly evolving.

Users who need custom behaviours in this area can submit a request or remove/replace the headers as necessary.

X-Content-Type-Options

Value: nosniff Endpoints: All

Prevents MIME type sniffing. See the MDN for more information.

Referrer-Policy

Value: strict-origin-when-cross-origin Endpoints: All

Sends only the origin as the referrer in cross-origin requests, but sends the origin, path, and query string in same-origin requests. See the MDN for more information.

X-Frame-Options

Value: SAMEORIGIN Endpoints: All

Prevents Authelia rendering in a frame, iframe, embed, or object element. See the MDN for more information.

X-XSS-Protection

Value: 0 Endpoints: All

We disable this as this feature is not present in any modern browser and could introduce vulnerabilities if enabled at all. Going forward CORS, CORP, CORB, and COEP are the standards for browser centric site security. See the MDN for more information.

Permissions-Policy

Value: interest-cohort=() Endpoints: All

Disables FLoC Cohorts.

Pragma

Value: no-cache Endpoints: API

Disables caching of API requests on HTTP/1.0 browsers. See the MDN for more information.

Cache-Control

Value: no-store Endpoints: API

Disables caching responses entirely on HTTP/1.1 browsers. See the MDN for more information.

More protections measures with fail2ban

If you are running fail2ban, adding a filter and jail for Authelia can reduce load on the application / web server. Fail2ban will ban IPs exceeding a threshold of repeated failed logins at the firewall level of your host. If you are using Docker, the Authelia log file location has to be mounted from the host system to the container for fail2ban to access it.

Create a configuration file in the filter.d folder with the content below. In Debian-based systems the folder is typically located at /etc/fail2ban/filter.d.

# Fail2Ban filter for Authelia

# Make sure that the HTTP header "X-Forwarded-For" received by Authelia's backend
# only contains a single IP address (the one from the end-user), and not the proxy chain
# (it is misleading: usually, this is the purpose of this header).

# the failregex rule counts every failed 1FA attempt (first line, wrong username or password) and failed 2FA attempt
# second line) as a failure.
# the ignoreregex rule ignores info and warning messages as all authentication failures are flagged as errors
# the third line catches incorrect usernames entered at the password reset form
# the fourth line catches attempts to spam via the password reset form or 2fa device reset form. This requires debug logging to be enabled

[Definition]
failregex = ^.*Unsuccessful 1FA authentication attempt by user .*remote_ip="?<HOST>"? stack.*
            ^.*Unsuccessful (TOTP|Duo|U2F) authentication attempt by user .*remote_ip="?<HOST>"? stack.*
            ^.*user not found.*path=/api/reset-password/identity/start remote_ip="?<HOST>"? stack.*
            ^.*Sending an email to user.*path=/api/.*/start remote_ip="?<HOST>"?

ignoreregex = ^.*level=info.*
              ^.*level=warning.*

Modify the jail.local file. In Debian-based systems the folder is typically located at /etc/fail2ban/. If the file does not exist, create it by copying the jail.conf cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local. Add an Authelia entry to the "Jails" section of the file:

[authelia]
enabled = true
port = http,https,9091
filter = authelia
logpath = /path-to-your-authelia.log
maxretry = 3
bantime = 1d
findtime = 1d
chain = DOCKER-USER

If you are not using Docker remove the line "chain = DOCKER-USER". You will need to restart the fail2ban service for the changes to take effect.

Container privilege de-escalation

Authelia will run as the root user and group by default, there are two options available to run as a non-root user and group.

It is recommended which ever approach you take that to secure the sensitive files Authelia requires access to that you make sure the chmod of the files does not inadvertently allow read access to the files by users who do not need access to them.

Examples:

If you wanted to run Authelia as UID 8000, and wanted the GID of 9000 to also have read access to the files you might do the following assuming the files were in the relative path .data/authelia:

chown -r 8000:9000 .data/authelia
find .data/authelia/ -type d -exec chmod 750 {} \;
find .data/authelia/ -type f -exec chmod 640 {} \;

If you wanted to run Authelia as UID 8000, and wanted the GID of 9000 to also have write access to the files you might do the following assuming the files were in the relative path .data/authelia:

chown -r 8000:9000 .data/authelia
find .data/authelia/ -type d -exec chmod 770 {} \;
find .data/authelia/ -type f -exec chmod 660 {} \;

Docker user directive

The docker user directive allows you to configure the user the entrypoint runs as. This is generally the most secure option for containers as no process accessible to the container ever runs as root which prevents a compromised container from exploiting unnecessary privileges.

The directive can either be applied in your docker run command using the --user argument or by the docker-compose user: key. The examples below assume you'd like to run the container as UID 8000 and GID 9000.

Example for the docker CLI:

docker run --user 8000:9000 -v /authelia:/config authelia/authelia:latest

Example for docker-compose:

version: '3.8'
services:
  authelia:
    image: authelia/authelia
    container_name: authelia
    user: 8000:9000
    volumes:
      - ./authelia:/config

Running the container in this way requires that you manually adjust the file owner at the very least as described above. If you do not do so it will likely cause Authelia to exit immediately. This option takes precedence over the PUID and PGID environment variables below, so if you use it then changing the PUID and PGID have zero effect.

PUID/PGID environment variables using the entrypoint

The second option is to use the PUID and PGID environment variables. When the container entrypoint is executed as root, the entrypoint automatically runs the Authelia process as this user. An added benefit of using the environment variables is the mounted volumes ownership will automatically be changed for you. It is still recommended that you run the find chmod examples above in order to secure the files even further especially on servers multiple people have access to.

The examples below assume you'd like to run the container as UID 8000 and GID 9000.