Difference between revisions of "ASL Configuration"
m (→HIDS_SHUN_MULTIPLIER) |
(→RESOURCE_LOGGING: correction, disabled by default) |
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==== RESOURCE_LOGGING ==== | ==== RESOURCE_LOGGING ==== | ||
| − | When enabled, all attempts to overstep resource limits will be logged with the resource name, the requested size, and the current limit. Due to high volume alerts this | + | When enabled, all attempts to overstep resource limits will be logged with the resource name, the requested size, and the current limit. Due to high volume alerts you can consider disabling this option. RESOURCE_LOGGING is disabled by default. |
==== ROMOUNT_PROTECT ==== | ==== ROMOUNT_PROTECT ==== | ||
Revision as of 14:33, 25 February 2013
Introduction
ASL is configured to a secure set of defaults upon installation. Most users do not need to change these settings.
Installation
ASL Installation settings are documented on the ASL installation page, please see that page for installation configuration options.
Post Installation Configuration
You can access the ASL configuration settings by following this process:
Step 1) Log into the ASL GUI
Step 2) Click on the Configuration tab
Step 3) Select "ASL Configuration"
This will pull up all the ASL Configuration options, which are broken into classes and are documented below or links are provided to the specific documentation pages for those options.
Authentication Information
ASL Web Settings
In addition to the settings below, also, please see the ASL Web Settings page for documentation about configuring the ASL GUI itself.
USERNAME
This is the username ASL will use to download updates. This should be the same username you use to log into the License Manager.
PASSWORD
This is the password ASL will use to download updates. This should be the same password you use to log into the License Manager.
ASL_DB_RETENTION
Period alert data is considered to be live before being moved into an archive table. Once this limit is reached, ASL will move the events into the database archive table.
The format for this field is an integer follow by "days" "weeks" "months" or "years". For example, if you want to archive events after 3 months, you would change this field to:
3 months
The default is 7 days. After 7 days, events are archived.
This value is ignored if ASL_DB_ARCHIVE is set to "no" below.
ASL_DB_ARCHIVE
ASL will store old data in monthly archive table if this is set to 'yes', or simply delete past retention data if it is set to 'no' once the ASL_DB_RETENTION period is reached for the data.
Data Paths
PATH_RSS
URL to the Atomicorp Security Bulletins RSS feed.
General Settings
NOTIFY
Determines if ASL will notify by email or not. Set this to yes if you want ASL to email you, and no if you do not.
Default email address used to send alerts to. This is also set during installation.
HOSTNAME
Hostname for the system. This is also set during installation.
ADMIN_USERS
Defines administrative users allowed to SSH to the system. If this is defined, AND the users exist, AND they have valid SSH keys, password auth and root logins will be automatically disabled.
SYSTEM_TYPE
Defines a basic services policy for the system. Currently webserver and custom are the only supported policies.
Setting the profile to "webserver" will configure ASL to disable the following services: portmap nfs nfslock rpcidmapd cups gpm xfs pcscd mcstrans kdump isdn hplip hidd messagebus haldaemon gpm bluetooth avahi-daemon autofs apmd.
If this is set to custom, no services will be automatically disabled.
AUTOMATIC_UPDATES
Configures the update frequency for ASL to download and install updates, such as new rules and signatures
NOTE: Updates can be run manually from the command line with aum -u.
If a software update is available you should follow your normal patch management procedure. We recommend that all users test upgrades on a test system before deploying to a production system. See "UPDATE_TYPE" below.
UPDATE_TYPE
Configures the behavior of the AUTOMATIC_UPDATE event. There are three options:
All: This will upgrade all ASL software, rule and signatures updates.
Exclude-kernel: This will upgrade all ASL software, rule and signatures updates but not upgrade the kernel.
rules-only: This will exclude all software updates, yum package updates and kernel updates and will only install rule and signature updates.
Some rule and signature updates may not work without ASL updates, so if you set this to "rules only" be sure to regularly check your system for any software updates for ASL to be fully protected.
RESTART_APACHE
Sets the restart policy for actions involving the web server. Updates to the WAF, mod_security, or mod_evasive policies will require a web server restart to go into effect. This setting has three options:
Yes: Restart apache when needed.
Graceful: Use the "graceful" method which tries to wait for all clients to finish being served before restarting Apache. If apache has a stuck thread or worker Graceful may not complete.
No: Do not restart apache.
Note: If you set this to "No", updates that require apache restarts will not be applied, such as new WAF rules. If you set this to "No" you will need to schedule regular restart intervals to install the latest rules. Only the latest rules are supported with the WAF.
ASL_USER
Sets the user to run ASL web activity under. This can be either "tortix" for use with ASL-Web, or "psaadm" for use with the Plesk ASL module. Note: this setting has been deprecated.
FEED_TYPE
This setting allows you to toggle between different WAF feeds. Currently this is only used by ASL Lite, and supports the Real-Time and 90-day delayed feeds. ASL Users should not change this setting.
COMPLIANCE
This a new and UNSUPPORTED feature. If you use this, we welcome your feedback but it is unsupported.
This enables a compliance module based on one of 5 standards (CIS, DISA, DHS, NISPOM, PCI). It is not recommended by Atomicorp that you use any of these. It should only be used if you are required by a 3rd party regulator.
These compliance standards are very generic, and will break things on your system. These are not Atomicorp standards, so if you enable them be prepared to fix things.
Firewall Configuration
Please see the ASL firewall page for documentation on these settings.
Kernel configuration
If you are not using the ASL Kernel these settings in the ASL web console will have no effect.
ALLOW_kmod_loading
The default configuration for ASL is to disable Loadable Kernel Modules (LKM) after the system has booted (S99). This is intended to provide additional protection from attempts to load LKM rootkits by "locking" the kernel and preventing any additional changes to the kernel once it has been configured.
Setting this flag to "yes" and rebooting the system will allow kernel modules to be loaded and unloaded dynamically after a reboot. We do not recommend you set this to "yes", as a properly configured server should not require the kernel to dynamically modified. A number of known and in the wild attacks on Linux servers take advantage of kernel module loading being allowed, which can also be triggered by non-root users and have been used to compromise Linux systems.
The secure and recommended setting is "no". Do not allow kernel module loading.
ENABLE_TPE
Trusted Path Execution(TPE) will allow you to choose a gid to add to the supplementary groups of users you want to mark as "untrusted" or "trusted". These users will not be able to execute any files that are not in root-owned directories writable only by root.
TPE_GROUP_POLICY
The TPE group policy indicates the mode to enforce on the system. These are "trusted", which is an Unless Allow, Deny configuration where only users in the "trusted" group can execute commands that are not owned by the root user. It is the more aggressive and constricted mode. The default "untrusted" mode is an Unless Deny, Allow policy where the TPE security controls only apply to users in the "untrusted" group.
TPE_UNTRUSTED_USERS
Users in this group will have the TPE policy applied if the system is configured to operate in "untrusted" mode. The root user is automatically trusted.
TPE_TRUSTED_USERS
Users in this group will NOT have the TPE policy applied if the system is configured to operate in the "trusted" mode. Setting the policy to "trusted" means that only users in this list are trusted, all other users are considered untrusted. The root user is automatically trusted.
DISABLE_PRIVILEGED_IO
If you say yes here, all ioperm and iopl calls will return an error. Ioperm and iopl can be used to modify the running kernel. This is generally safe to set to "yes". Very few applications require that this be set to "no".
Some programs may need this access to operate properly, the most notable of which are XFree86 and hwclock.
hwclock is remedied by having RTC support in the the ASL kernel, so real-time clock support is enabled if this option is enabled, to ensure that hwclock operates correctly.
XFree86 still will not operate correctly with this option enabled, so DO NOT CHOOSE YES IF YOU USE XFree86.
AUDIT_MOUNT
Log all mount() and umount() actions.
AUDIT_CHDIR
Log all chdir() calls, or every time an application or user changes their directory. This is a high volume setting, and is disabled by default.
AUDIT_PTRACE
Log all attempts to attach to a process via ptrace().
AUDIT_TEXTREL
Log text relocations with the filename of the offending library or binary. This is a high volume setting, and is disabled by default.
CHROOT_CAPS
When enabled, the capabilities on all root processes within a chroot jail will be lowered to stop module insertion, raw i/o, system and net admin tasks, rebooting the system, modifying immutable, files, modifying IPC owned by another, and changing the system time.
Note: EL6 boots the system into a chroot. Enabling this protection will cause the first tty on the system to "echo" all input that should not be "echoed". For example, the password field will echo from the console on tty1.
The solution is to either disable this protection, or to use a different tty. See this forum post for a more detailed explanation:
https://www.atomicorp.com/forums/viewtopic.php?f=3&t=6292&p=36069&hilit=chroot#p36069
CHROOT_DENY_CHMOD
When enabled, processes inside a chroot will not be able to chmod or fchmod files to make them have suid or sgid bits.
CHROOT_DENY_CHROOT
When enabled, processes inside a chroot will not be able to chroot again outside the chroot.
CHROOT_DENY_FCHDIR
When enabled, a well-known method of breaking chroots by fchdir'ing to a file descriptor of the chrooting process that points to a directory outside the filesystem will be stopped.
CHROOT_DENY_MKNOD
When enabled, processes inside a chroot will not be allowed to mknod.
CHROOT_DENY_MOUNT
When enabled, processes inside a chroot will not be able to mount or remount.
CHROOT_DENY_PIVOT
When enabled, processes inside root will not be able to use pivot_root().
CHROOT_DENY_SHMAT
When enabled, processes inside a chroot will not be able to attach to shared memory segments that were created outside of the chroot jail.
CHROOT_DENY_SYSCTL
When enabled, an attacker in a chroot will not be able to write to sysctl entries, either by sysctl(2) or through a /proc interface.
CHROOT_DENY_UNIX
When enabled, processes inside a chroot will not be able to connect to abstract (meaning not belonging to a filesystem) Unix domain sockets that were bound outside of a chroot.
CHROOT_ENFORCE_CHDIR
When enabled, current working directory of all newly-chrooted applications will be set to the the root directory of the chroot.
CHROOT_ENFORCE_CHDIR
When enabled, current working directory of all newly-chrooted applications will be set to the the root directory of the chroot.
CHROOT_EXECLOG
When enabled, all executions inside a chroot jail will be logged to syslog. This is a high volume setting and is disabled by default.
CHROOT_FINDTASK
When enabled, processes inside a chroot will not be able to kill, send signals with fcntl, ptrace, capget, getpgid, setpgid, getsid, or view any process outside of the chroot.
CHROOT_RESTRICT_NICE
When enabled, processes inside a chroot will not be able to raise the priority of processes in the chroot, or alter the priority of processes outside the chroot.
EXEC_LOGGING
When enabled, all execve() calls for users in the group execlog (1007) will be logged (since the other exec*() calls are frontends to execve(), all execution will be logged). This is a high volume setting and is disabled by default.
EXEC_LOG_USERS
Users in the group execlog will have all execve() actions logged to syslog if EXEC_LOGGING is enabled. This is a high volume setting, and is disabled by default.
DMESG
When enabled, non-root users will not be able to use dmesg(8) to view up to the last 4kb of messages in the kernel's log buffer.
EXECVE_LIMITING
When enabled, users with a resource limit on processes will have the value checked during execve() calls.
FIFO_RESTRICTIONS
When enabled, users will not be able to write to FIFOs they don't own in world-writable +t directories (i.e. /tmp), unless the owner of the FIFO is the same owner of the directory it's held in.
FORKFAIL_LOGGING
When enabled, all failed fork() attempts will be logged.
HARDEN_PTRACE
When enabled, TTY sniffers and other malicious monitoring programs implemented through ptrace will be defeated.
Certain Parallels products have a bug that requires that this protection be disabled. These products have a bug that incorrectly reports that users are running a debugger, when they are not if this protection is enabled. This is a bug in Plesk, and not in ASL. Please report this bug to Parallels if you wish to use these feature.
You can read more about this bug in Plesk at the forum post below:
https://atomicorp.com/forums/viewtopic.php?f=3&t=4636&p=26867#p26867
IP_BLACKHOLE
When enabled, either TCP resets nor ICMP destination-unreachable packets will be sent in response to packets sent to ports for which no associated listening process exists.
LASTACK_RETRIES
When enabled, prevents a socket from lasting more than 45 seconds in LAST_ACK state. The default value of 4 prevents a socket from lasting more than 45 seconds in LAST_ACK state.
The default is 4.
LINKING_RESTRICTIONS
When enabled, /tmp race exploits will be prevented, since users will no longer be able to follow symlinks owned by other users in world-writable +t directories (i.e. /tmp), unless the owner of the symlink is the owner of the directory. users will also not be able to hardlink to files they do not own.
RESOURCE_LOGGING
When enabled, all attempts to overstep resource limits will be logged with the resource name, the requested size, and the current limit. Due to high volume alerts you can consider disabling this option. RESOURCE_LOGGING is disabled by default.
ROMOUNT_PROTECT
By setting this option to 1 at runtime, filesystems will be protected in the following ways: No new writable mounts will be allowed, Existing read-only mounts won't be able to be remounted read/write, Write operations will be denied on all block devices. This is best used in embedded or appliance type environments, and is disabled by default.
RWXMAP_LOGGING
When enabled, calls to mmap() and mprotect() with explicit usage of PROT_WRITE and PROT_EXEC together will be logged when denied by the PAX_MPROTECT feature.
SIGNAL_LOGGING
When enabled, certain important signals will be logged, such as SIGSEGV, which will as a result inform you of when a error in a program occurred, which in some cases could mean a possible exploit attempt. This is disabled by default.
SOCKET_ALL
When enabled, you will be able to choose which users will be unable to connect to other hosts from your machine or run server applications from your machine.
SOCKET_USERS
Users in the socket group be unable to connect to other hosts from your machine or run server applications from your machine.
SOCKET_CLIENT
When enabled, users in the client group will only be able to create outbound connections, and will be prevented from creating servers on the system (clients can not listen for incoming connections).
SOCKET_CLIENT_USERS
Users in the client group will be unable to run server applications from your machine. This is in a comma delimited format.
SOCKET_SERVER
When enabled, the server-only policy group will be enabled on the system. Users in the servers group will be able to run servers on the system, but be unable to connect to other hosts from the machine.
SOCKET_SERVER_USERS
Users in the server group will be able to run services on the system, but be unable to connect to other hosts from the system as a client. This is in a comma delimited format.
Non GUI options
There are a few options that are not currently configurable via the web console. These will be added in a future release of ASL.
Restrict symlinks to owner
This is a kernel-based race-free implementation of Apache's SymlinksIfOwnerMatch option. This is enabled by placing users into a special group. When users are made part of this group, ASL restricts the following of symlinks to the owner of the file. This means that if a user is part of this special group, and creates a symlink to a file or directory they do not own, the kernel will prevent the symlink from being followed. This feature ensures that a compromised user on a shared hosting server can't cause Apache to follow a symlink to a sensitive file in another user's webroot in order to read its contents.
Note: This requires kernel 2.6.32.59-28 and up, and gradm 2.9.1 and up.
To add a user
To restrict a user, simply add their user ID to the symlinkown_gid. By default, that group is "1008". So if you add a user ID to group ID 1008, that user will not be able to follow symlinks to files and directories they do not own. For example:
If user "bob" has the uid "123", and symlinkown_gid is set to 1006, you can add bob to the symlinkown_gid with this command:
usermod -a -G 1008 bob
Note: For web applications, if you wish to enforce this restriction, its important to make sure that the effective uid for the web application is included in this group. For example, if your web applications run as the user "apache", then apache must be added to this group.
To change the group ID
If you wish to change the GID for the symlinkown group, you will need to set this condition as part of your /etc/sysctl.conf file:
kernel.grsecurity.symlinkown_gid = 12345
Change 12345 to the GID you wish to use.
One trick with this option, is to set the GID to the default GID for your users. This is a quick way to cause this restriction to be automatically inherited by your users.
Note: If your kernel is locked, this may require a reboot of your system.
TIMECHANGE_LOGGING
ClamAV configuration
Also, see the anti virus page for important documentation about configuring the Real Time Antimalware system in ASL.
CLAMAV_ENABLED
Enable or Disable the ClamAV malware detection engine for the system.
CLAMAV_ENABLE_DAZUKO
Enable or Disable the the kernel realtime antimalware detect module. Note this requires the ASL kernel, and the dazuko module.
To configure, please see the Anti virus page.
CLAMAV_TCPADDRESS
Set the IP address for clamd to listen on. Default: localhost
This is an unsupported option, and will not work with the CLAMAV_ENABLE_DAZUKO option, which when enabled, requires a local instance of clamd.
CLAMAV_SCANONACCESS
Scan with clamav when a file is accessed. This requires CLAMAV_ENABLE_DAZUKO be set to use, and the ASL kernel is used. Default: no
CLAMAV_SCANONOPEN
Scan with clamav when a file is opened. This requires CLAMAV_ENABLE_DAZUKO be set to use, and the ASL kernel is used. Default: no
CLAMAV_SCANONEXEC
Scan with clamav when a file is executed. This requires CLAMAV_ENABLE_DAZUKO be set to use, and the ASL kernel is used. Default: no
CLAMAV_SCANONCLOSE
Scan with clamav when a file is closed. This requires CLAMAV_ENABLE_DAZUKO be set to use, and the ASL kernel is used. Default: no
CLAMAV_CLAMUKO_MAXFILESIZE
Maximum size of a file dazuko will scan in megs. This requires dazuko. Default: 10m
PSMON configuration
PSMON_ENABLED
Allows the Process monitoring daemon to be enabled/disabled.
Note: not supported on systems that do not use package managed PERL installations.
PSMON_NOTIFY =
Enable/Disable email notification for PSMON. The default is to use the $NOTIFY setting.
PSMON_EMAIL
Email address notifications of restart events will be sent to. The default is to use the value set for EMAIL
PSMON_FROM
From: line used for notifications of restart events. The default is to use psmon@hostname of the system
OSSEC configuration
OSSEC_ENABLED
Enable or Disable OSSEC HIDS
OSSEC_NOTIFY
Configure OSSEC to send alert notifications over email or not. Default is yes.
OSSEC_MODE
Operating mode for OSSEC, can be configured as either 'server' or 'client'. When in client mode you will need to set up the OSSEC key from the command line.
OSSEC_USE_MYSQL
Configure OSSEC to store events in mysql
OSSEC_DATABASE_SERVER
IP or hostname of OSSEC database server. Note OSSEC only uses tcp sockets. Network access is required
Remote mysql servers are not currently supported (but they may work).
OSSEC_DATABASE
Name of OSSEC database
OSSEC_DATABASE_USERNAME
Name of OSSEC database user
OSSEC_DATABASE_PASSWORD
Password for OSSEC database user
OSSEC_SERVER
IP address of OSSEC server, when this node is configured to be an OSSEC client. Leave this blank if OSSEC_MODE is set to server.
OSSEC_EMAIL
Email address to send all OSSEC alert notifications
OSSEC_SMTP_SERVER
SMTP server to send OSSEC alert notifications.
OSSEC_FROM
From: line used for OSSEC alert notifications
OSSEC_MAX_MSG
Maximum number of email messages OSSEC will send per hour. Multiple alerts will be sent in digest mode (a single email). Setting this to 0 will disable digest mode
OSSEC_ACTIVE_RESPONSE
Enable/Disable Active response mode. Setting this to yes will enable active firewall blocks when ASL detects an attack. Setting this to no will prevent ASL from enabling any firewall blocks due to an attack.
OSSEC_SHUN_ENABLE_TIMEOUT
Enable/Disable expiration of active response firewall blocks. Setting this to yes will expire blocks after a fixed interval defined in OSSEC_SHUN_TIME. Setting this to no will make all blocks permanent (not recommended).
OSSEC_SHUN_TIME
Number of seconds to maintain an active response block. Default is 600 seconds (10 minutes).
HIDS_SHUN_MULTIPLIER
Enable a block time multiplier for repeat offenders based on the Shun Time setting. OSSEC_SHUN_TIME will be multipled by this number for reach successive attack from an IP. Repeat attackers will be blocked for longer and longer periods based on this setting. For example, if the default shun time is 600 seconds, and HIDS_SHUN_MULTIPLE is set to "2" on the first attack the IP will be blocked for 600 seconds, on the second 1200 seconds, and so on. This data is valid for as long as the OSSEC Daemon is running, once OSSEC is restarded, all of this data will be lost/reset.
HIDS_EMAIL_ALERT_LEVEL
This controls the minimum level an alert will need to be in order to activate an email event. Some events will be sent that are lower levels than this, for example 1002 which is the suspicious event alert. You can disable specific over rides in the rule manager.
Mod_security configuration
Please see the ASL WAF page for documentation on these settings.
PHP configuration
PHP_CHECKS
Enable/Disable PHP check enforcement mode. Default: No.
If this is set to "no", ASL will not be configured to manage any PHP settings, and rest of the PHP settings will have no effect. To enable, or disable PHP functions, this must be set to "yes".
Note: Setting this to no will still test for vulnerabilities, but will neither fix them, nor make any changes to your PHP configuration.
PHP_SAFE_MODE
Enable/Disable PHP Safe_Mode
Note: PHP 5.3 and later has deprecated this feature.
PHP_REGISTER_GLOBALS
Enable/Disable register_globals.
PHP_URL_FOPEN
Enable/Disable url_fopen
PHP_URL_INCLUDE
Enable/Disable URL includes
ALLOW_curl_exec
Enable/Disable the curl_exec() function
ALLOW_curl_multi_exec
Enable/Disable the curl_multi_exec() function
ALLOW_dl
Enable/Disable the dl() function
SSH daemon configuration
Also, see the SSH debugging page in case you can't log into your ASL server via SSH.
SSH_PROTOCOL
Note: Do not change this setting unless you know what you are doing.
SSH supports several legacy protocols (1 and 1.5), along with the current SSH protocol, 2. 1 and 1.5 have fundamental weakenesses that can cause SSH sessions with those protocols to be compromised, therefore we recommend you leave the protocol setting of "2".
Default: 2
SSH_PORT
This will tell SSH to change its default port of 22 to a different port. If you set this to "no", that will tell SSH to use the default port of 22. For example, if you wanted to change SSHs port to "2222" you would enter "2222" in this field.
Default: no
SSH_STRICTMODE
This tells SSH to check the ownership and permissions on ssh public key files. This prevents a user from accidentally setting the permissions on the file so that other users can add their keys to another users key file. We highly recommend you enable strict modes.
Default: yes
==== SSH_IGNORE_RHOSTS="yes"
This tells SSH to ignore rhosts file. rhosts files tell SSH to trust another host completely, which means a user logging in from that host will not asked for a password. Allowing rhosts files is very insecure, and we recommend you leave this enabled.
Default: yes
SSH_PUBKEY
This setting tells SSH to allow the use of public keys, instead of passwords, for authentication. Public keys are more secure than passwords, provided that the public key itself has a strong password. Keys can provide a cheap two factor authentication system (what you have, and what you know).
Default: yes
SSH_ROOTLOGINS
This setting tells SSH to allow root logins. If you set this to yes, root will be allowed to ssh in, if you set this to no, root will not be allowed to ssh in. We recommend you set this to "no".
Default: yes
SSH_PASSWORD_AUTH
This enables/disables password authentication via SSH.
Default: yes
SSH_PRIV_SEPARATION="yes"
This ensures that SSH runs with privilege separation.
Default: Yes.
SSH_GSSAPI_AUTH="no"
Default: No.
SSH_GSSAPI_CLEANUP
Default: No.
SSH_BANNER
ASL can configure SSH to display a banner to users when they log in. This tells SSH what file to use for the banner. ASL comes with a standard banner you can use that is provided in the /etc/asl/banner file.
Default: /etc/asl/banner
SSH_USEDNS
Default: yes
Rkhunter settings
Mod_evasive
Also, see the Mod evasive page for important documentation about configuring the DOS protection system for Apache.
Web App Inventory
APPINV_CRON
Interval to run the web application inventory engine. Default is daily.
Plesk Security Settings
PSA_DISABLE_CRONTAB
This setting will disable the ability to manage cron jobs in Plesk.
Default: No. Which means that you can manage cron jobs in Plesk.
