mailu/webmails/snuffleupagus.rules

# This is based on default configuration file for Snuffleupagus (https://snuffleupagus.rtfd.io),
# for php8.
# It contains "reasonable" defaults that won't break your websites,
# and a lot of commented directives that you can enable if you want to
# have a better protection.

# Harden the PRNG
sp.harden_random.enable();

# Disabled XXE
sp.xxe_protection.enable();

# Global configuration variables
sp.global.secret_key("{{ SNUFFLEUPAGUS_KEY }}");

# Globally activate strict mode
# https://www.php.net/manual/en/language.types.declarations.php#language.types.declarations.strict
sp.global_strict.enable();

# Prevent unserialize-related exploits
# sp.unserialize_hmac.enable();

# Only allow execution of read-only files. This is a low-hanging fruit that you should enable.
sp.readonly_exec.enable();

# PHP has a lot of wrappers, most of them aren't usually useful, you should
# only enable the ones you're using.
sp.wrappers_whitelist.list("file,php,phar,mailsosubstreams");

# Prevent sloppy comparisons.
sp.sloppy_comparison.enable();

# Use SameSite on session cookie
# https://snuffleupagus.readthedocs.io/features.html#protection-against-cross-site-request-forgery
sp.cookie.name("PHPSESSID").samesite("lax");

# Harden the `chmod` function (0777 (oct = 511, 0666 = 438)
sp.disable_function.function("chmod").param("permissions").value("438").drop();
sp.disable_function.function("chmod").param("permissions").value("511").drop();

# Prevent various `mail`-related vulnerabilities
sp.disable_function.function("mail").param("additional_parameters").value_r("\\-").drop();

# Since it's now burned, me might as well mitigate it publicly
sp.disable_function.function("putenv").param("assignment").value_r("LD_").drop()

# This one was burned in Nov 2019 - https://gist.github.com/LoadLow/90b60bd5535d6c3927bb24d5f9955b80
sp.disable_function.function("putenv").param("assignment").value_r("GCONV_").drop()

# Since people are stupid enough to use `extract` on things like $_GET or $_POST, we might as well mitigate this vector
sp.disable_function.function("extract").param("array").value_r("^_").drop()
sp.disable_function.function("extract").param("flags").value("0").drop()

# This is also burned:
# ini_set('open_basedir','..');chdir('..');…;chdir('..');ini_set('open_basedir','/');echo(file_get_contents('/etc/passwd'));
# Since we have no way of matching on two parameters at the same time, we're
# blocking calls to open_basedir altogether: nobody is using it via ini_set anyway.
# Moreover, there are non-public bypasses that are also using this vector ;)
sp.disable_function.function("ini_set").param("option").value_r("open_basedir").drop()

# Prevent various `include`-related vulnerabilities
sp.disable_function.function("require_once").value_r("\.(inc|phtml|php)$").allow();
sp.disable_function.function("include_once").value_r("\.(inc|phtml|php)$").allow();
sp.disable_function.function("require").value_r("\.(inc|phtml|php)$").allow();
sp.disable_function.function("include").value_r("\.(inc|phtml|php)$").allow();
sp.disable_function.function("require_once").drop()
sp.disable_function.function("include_once").drop()
sp.disable_function.function("require").drop()
sp.disable_function.function("include").drop()

# Prevent `system`-related injections
sp.disable_function.function("system").param("command").value_r("[$|;&`\\n\\(\\)\\\\]").drop();
sp.disable_function.function("shell_exec").param("command").value_r("[$|;&`\\n\\(\\)\\\\]").drop();
sp.disable_function.function("exec").param("command").value_r("[$|;&`\\n\\(\\)\\\\]").drop();
# This is **very** broad but doing better is non-straightforward
sp.disable_function.function("proc_open").param("command").value_r("^gpg ").allow();
sp.disable_function.function("proc_open").param("command").value_r("[$|;&`\\n\\(\\)\\\\]").drop();

# Prevent runtime modification of interesting things
sp.disable_function.function("ini_set").param("option").value("assert.active").drop();
sp.disable_function.function("ini_set").param("option").value("zend.assertions").drop();
sp.disable_function.function("ini_set").param("option").value("memory_limit").drop();
sp.disable_function.function("ini_set").param("option").value("include_path").drop();
sp.disable_function.function("ini_set").param("option").value("open_basedir").drop();

# Detect some backdoors via environment recon
sp.disable_function.function("ini_get").param("option").value("allow_url_fopen").drop();
sp.disable_function.function("ini_get").param("option").value("open_basedir").drop();
sp.disable_function.function("ini_get").param("option").value_r("suhosin").drop();
sp.disable_function.function("function_exists").param("function").value("eval").drop();
sp.disable_function.function("function_exists").param("function").value("exec").drop();
sp.disable_function.function("function_exists").param("function").value("system").drop();
sp.disable_function.function("function_exists").param("function").value("shell_exec").drop();
sp.disable_function.function("function_exists").param("function").value("proc_open").drop();
sp.disable_function.function("function_exists").param("function").value("passthru").drop();
sp.disable_function.function("is_callable").param("value").value("eval").drop();
sp.disable_function.function("is_callable").param("value").value("exec").drop();
sp.disable_function.function("is_callable").param("value").value("system").drop();
sp.disable_function.function("is_callable").param("value").value("shell_exec").drop();
sp.disable_function.function("is_callable").filename_r("/app/libraries/snappymail/pgp/gpg\.php$").param("value").value("proc_open").allow();
sp.disable_function.function("is_callable").param("value").value("proc_open").drop();
sp.disable_function.function("is_callable").param("value").value("passthru").drop();

# Ghetto error-based sqli detection
#sp.disable_function.function("mysql_query").ret("FALSE").drop();
#sp.disable_function.function("mysqli_query").ret("FALSE").drop();
#sp.disable_function.function("PDO::query").ret("FALSE").drop();

# Ensure that certificates are properly verified
sp.disable_function.function("curl_setopt").param("value").value("1").allow();
sp.disable_function.function("curl_setopt").param("value").value("2").allow();
# `81` is SSL_VERIFYHOST and `64` SSL_VERIFYPEER
sp.disable_function.function("curl_setopt").param("option").value("64").drop().alias("Please don't turn CURLOPT_SSL_VERIFYCLIENT off.");
sp.disable_function.function("curl_setopt").param("option").value("81").drop().alias("Please don't turn CURLOPT_SSL_VERIFYHOST off.");

# File upload
sp.disable_function.function("move_uploaded_file").param("to").value_r("\\.ph").drop();
sp.disable_function.function("move_uploaded_file").param("to").value_r("\\.ht").drop();

# Logging lockdown
sp.disable_function.function("ini_set").param("option").value_r("error_log").drop()
sp.disable_function.function("ini_set").param("option").value_r("display_errors").drop()

sp.auto_cookie_secure.enable();
# TODO: consider encrypting the cookies?
# TODO: ensure this is up to date
sp.cookie.name("roundcube_sessauth").samesite("strict");
sp.cookie.name("roundcube_sessid").samesite("strict");
sp.ini_protection.policy_silent_fail();

# roundcube uses unserialize() everywhere.
# This should do the job until https://github.com/jvoisin/snuffleupagus/issues/438 is implemented.
sp.disable_function.function("unserialize").param("data").value_r("[cCoO]:\d+:[\"{]").drop();