Apache Server 2.4 Unix
Apache Server 2.4 for Unix Benchmark - Custom. Version v1 r1, released June 9, 2018.
WA000-WWA024 A24: The KeepAliveTimeout directive must be enabled
To view the KeepAliveTimeout value enter the following command: find / -name httpd.conf -print -exec grep -H -i "KeepAliveTimeout" {} \; If the value of "KeepAliveTimeout" is not set to 15 or less, this is a finding. Note: If the directive does not exist, this is not a finding because it will default to 5. It is recommended that the directive be explicitly set to prevent unexpected results should the defaults for any reason change(i.e. software update).
Discussion
The number of seconds Apache will wait for a subsequent request before closing the connection. Once a request has been received, the timeout value specified by the Timeout directive applies. Setting KeepAliveTimeout to a high value may cause performance problems in heavily loaded servers. The higher the timeout, the more server processes will be kept occupied waiting on connections with idle clients. These requirements are set to mitigate the effects of several types of denial of service attacks.
Fix
Edit the httpd.conf file and set the value of "KeepAliveTimeout" to the value of 15 or less.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG370 A24: MIME types for csh or sh shell programs must be disabled.
Enter the following commands: find / -name httpd.conf -print -exec grep -H -i "Action" {} \; find / -name httpd.conf -print -exec grep -H -i "AddHandler" {} \; If either of these exist and they configure /bin/csh, or any other shell as a viewer for documents, this is a finding.
Discussion
Users must not be allowed to access the shell programs. Shell programs might execute shell escapes and could then perform unauthorized activities that could damage the security posture of the web server. A shell is a program that serves as the basic interface between the user and the operating system. In this regard, there are shells that are security risks in the context of a web server and shells that are unauthorized in the context of the Security Features User's Guide.
Fix
Disable MIME types for csh or sh shell programs.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG440 A24: Monitoring software must include CGI or equivalent programs in its scope.
CGI or equivalent files must be monitored by a security tool that reports unauthorized changes. It is the purpose of such software to monitor key files for unauthorized changes to them. The reviewer should query the ISSO, the SA, and the web administrator and verify the information provided by asking to see the template file or configuration file of the software being used to accomplish this security task. Example file extensions for files considered to provide active content are, but not limited to, .cgi, .asp, .aspx, .class, .vb, .php, .pl, and .c. If the site does not have a process in place to monitor changes to CGI program files, this is a finding.
Discussion
By their very nature, CGI type files permit the anonymous web user to interact with data and perhaps store data on the web server. In many cases, CGI scripts exercise system-level control over the server’s resources. These files make appealing targets for the malicious user. If these files can be modified or exploited, the web server can be compromised. These files must be monitored by a security tool that reports unauthorized changes to these files.
Fix
Use a monitoring tool to monitor changes to the CGI or equivalent directory. This can be done with something as simple as a script or batch file that would identify a change in the file.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA022 A24: The KeepAlive directive must be enabled
To view the KeepAlive value enter the following command: find / -name httpd.conf -print -exec grep -H -i "KeepAlive" {} \; Verify the Value of KeepAlive is set to "On" If not, this is a finding. NOTE: This vulnerability can be documented locally with the ISSM/ISSO if the site has operational reasons for not using persistent connections. If the site has this documentation, this should be marked as Not a Finding.
Discussion
The KeepAlive extension to HTTP/1.0 and the persistent connection feature of HTTP/1.1 provide long lived HTTP sessions which allow multiple requests to be sent over the same connection. These requirements are set to mitigate the effects of several types of denial of service attacks. Although there is some latitude concerning the settings themselves, the requirements attempt to provide reasonable limits for the protection of the web server. If necessary, these limits can be adjusted to accommodate the operational requirement of a given system.
Fix
Edit the httpd.conf file and set the value of "KeepAlive" to "On"
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA032 A24: The httpd.conf MaxRequestWorkers directive must be set properly.
To view the MaxRequestWorkers value enter the following command: find / -name httpd.conf -print -exec grep -H -i "MaxRequestWorkers" {} \; If the value of "MaxRequestWorkers" is not 256 or less, this is a finding. If the directive does not exist, this is NOT a finding because it will default to 256. It is recommended that the directive be explicitly set to prevent unexpected results if the defaults change with updated software. NOTE: This vulnerability can be documented locally with the ISSM/ISSO if the site has operational reasons for the use of increased value. If the site has this documentation, this should be marked as Not a Finding.
Discussion
These requirements are set to mitigate the effects of several types of denial of service attacks. Although there is some latitude concerning the settings themselves, the requirements attempt to provide reasonable limits for the protection of the web server. If necessary, these limits can be adjusted to accommodate the operational requirement of a given system. From Apache.org: The MaxRequestWorkers directive sets the limit on the number of simultaneous requests that will be served. Any connection attempts over the MaxRequestWorkers limit will normally be queued, up to a number based on the ListenBacklog directive. Once a child process is freed at the end of a different request, the connection will then be serviced. For non-threaded servers (i.e., prefork), MaxRequestWorkers translates into the maximum number of child processes that will be launched to serve requests. The default value is 256; to increase it, you must also raise ServerLimit. For threaded and hybrid servers (e.g. event or worker) MaxRequestWorkers restricts the total number of threads that will be available to serve clients. For hybrid MPMs the default value is 16 (ServerLimit) multiplied by the value of 25 (ThreadsPerChild). Therefore, to increase MaxRequestWorkers to a value that requires more than 16 processes, you must also raise ServerLimit.
Fix
Edit the httpd.conf file and set the value of "MaxRequestWorkers" to a value of 256 or less, add the directive if it does not exist.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG190 A24: Web server software must be a vendor-supported version.
To determine the version of the Apache software that is running on the system. Use the command: httpd -v If the version of Apache is not at the following version or higher, this is a finding. Apache httpd server version 2.4 - Release 2.4.33 (March 2018) Note: In some situations, the Apache software that is being used is supported by another vendor, such as Oracle in the case of the Oracle Application Server or IBMs HTTP Server. The versions of the software in these cases may not match the above mentioned version numbers. If the site can provide vendor documentation showing the version of the web server is supported, this would not be a finding.
Discussion
Many vulnerabilities are associated with older versions of web server software. As hot fixes and patches are issued, these solutions are included in the next version of the server software. Maintaining the web server at a current version makes the efforts of a malicious user to exploit the web service more difficult.
Fix
Install the current version of the web server software and maintain appropriate service packs and patches.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
WG130 A24: All utility programs, not necessary for operations, must be removed or disabled.
If the site requires the use of a particular piece of software, the ISSO will need to maintain documentation identifying this software as necessary for operations. The software must be operated at the vendor’s current patch level and must be a supported vendor release. If programs or utilities that meet the above criteria are installed on the Web Server, and appropriate documentation and signatures are in evidence, this is not a finding. Determine whether the web server is configured with unnecessary software. Determine whether processes other than those that support the web server are loaded and/or run on the web server. Examples of software that should not be on the web server are all web development tools, office suites (unless the web server is a private web development server), compilers, and other utilities that are not part of the web server suite or the basic operating system. Check the directory structure of the server and ensure that additional, unintended, or unneeded applications are not loaded on the system. If, after review of the application on the system, there is no justification for the identified software, this is a finding.
Discussion
Just as running unneeded services and protocols is a danger to the web server at the lower levels of the OSI model, running unneeded utilities and programs is also a danger at the application layer of the OSI model. Office suites, development tools, and graphical editors are examples of such programs that are troublesome. Individual productivity tools have no legitimate place or use on an enterprise, production web server and they are also prone to their own security risks.
Fix
Remove any unnecessary applications
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
WG145 A24: The private web server must use an approved DoD certificate validation process.
The reviewer should query the ISSO, the SA, the web administrator, or developers as necessary to determine if the web server is configured to utilize an approved DoD certificate validation process. The web administrator should be questioned to determine if a validation process is being utilized on the web server. To validate this, the reviewer can ask the web administrator to describe the validation process being used. They should be able to identify either the use of certificate revocation lists (CRLs) or Online Certificate Status Protocol (OCSP). If the production web server is accessible, the SA or the web administrator should be able to demonstrate the validation of good certificates and the rejection of bad certificates. If CRLs are being used, the SA should be able to identify how often the CRL is updated and the location from which the CRL is downloaded. If the web administrator cannot identify the type of validation process being used, this is a finding.
Discussion
Without the use of a certificate validation process, the site is vulnerable to accepting certificates that have expired or have been revoked. This would allow unauthorized individuals access to the web server. This also defeats the purpose of the multi-factor authentication provided by the PKI process.
Fix
Configure DoD Private Web Servers to conduct certificate revocation checking utilizing certificate revocation lists (CRLs) or Online Certificate Status Protocol (OCSP).
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG040 A24: Public web server resources must not be shared with private assets.
Determine whether the public web server has a two-way trusted relationship with any private asset located within the network. Private web server resources (e.g., drives, folders, printers, etc.) will not be directly mapped to or shared with public web servers. If sharing is selected for any web folder, this is a finding. If private resources (e.g., drives, partitions, folders/directories, printers, etc.) are shared with the public web server, then this is a finding.
Discussion
It is important to segregate public web server resources from private resources located behind the DoD DMZ in order to protect private assets. When folders, drives or other resources are directly shared between the public web server and private servers the intent of data and resource segregation can be compromised. In addition to the requirements of the DoD Internet-NIPRNet DMZ STIG that isolates inbound traffic from the external network to the internal network, resources such as printers, files, and folders/directories will not be shared between public web servers and assets located within the internal network.
Fix
Configure the public web server to not have a trusted relationship with any system resource that is also not accessible to the public. Web content is not to be shared via Microsoft shares or NFS mounts.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA060 A24: A public web server, if hosted on the NIPRNet, must be isolated in an accredited DoD DMZ Extension.
Interview the SA or web administrator to see where the public web server is logically located in the data center. Review the site’s network diagram to see how the web server is connected to the LAN. Visually check the web server hardware connections to see if it conforms to the site’s network diagram. An improperly located public web server is a potential threat to the entire network. If the web server is not isolated in an accredited DoD DMZ Extension, this is a finding.
Discussion
To minimize exposure of private assets to unnecessary risk by attackers, public web servers must be isolated from internal systems. Public web servers are by nature more vulnerable to attack from publically based sources, such as the public Internet. Once compromised, a public web server might be used as a base for further attack on private resources, unless additional layers of protection are implemented. Public web servers must be located in a DoD DMZ Extension, if hosted on the NIPRNet, with carefully controlled access. Failure to isolate resources in this way increase risk that private assets are exposed to attacks from public sources.
Fix
Logically relocate the public web server to be isolated from internal systems. In addition, ensure the public web server does not have trusted connections with assets outside the confines of the demilitarized zone (DMZ) other than application and/or database servers that are a part of the same system as the web server.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA054 A24: Server side includes (SSIs) must run with execution capability disabled.
To view the Options value enter the following command: find / -name httpd.conf -print -exec grep -H -i "Options" {} \; Review all uncommented Options statements for the following values: +IncludesNOEXEC -IncludesNOEXEC -Includes If none of these values exist, this is a finding. Notes: - If all enabled Options statements are set to None this is not a finding.
Discussion
The Options directive configures the web server features that are available in particular directories. The IncludesNOEXEC feature controls the ability of the server to utilize SSIs while disabling the exec command, which is used to execute external scripts. If the full includes feature is used it could allow the execution of malware leading to a system compromise.
Fix
Edit the httpd.conf file and add one of the following to the enabled Options directive: +IncludesNOEXEC -IncludesNOEXEC -Includes Remove the 'Includes' or '+Includes' setting from the Options statement.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
WG204 A24: A web server must be segregated from other services.
Request a copy of and review the web server’s installation and configuration plan. Ensure that the server is in compliance with this plan. If the server is not in compliance with the plan, this is a finding. Query the SA to ascertain if and where the additional services are installed. Confirm that the additional service or application is not installed on the same partition as the operating systems root directory or the web document root. If it is, this is a finding.
Discussion
The web server installation and configuration plan should not support the co-hosting of multiple services such as Domain Name Service (DNS), e-mail, databases, search engines, indexing, or streaming media on the same server that is providing the web publishing service. By separating these services additional defensive layers are established between the web service and the applicable application should either be compromised. Disallowed or restricted services in the context of this vulnerability applies to services that are not directly associated with the delivery of web content. An operating system that supports a web server will not provide other services (e.g., domain controller, e-mail server, database server, etc.). Only those services necessary to support the web server and its hosted sites are specifically allowed and may include, but are not limited to, operating system, logging, anti-virus, host intrusion detection, administrative maintenance, or network requirements.
Fix
Move or install additional services and applications to partitions that are not the operating system root or the web document root.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG280 A24: The access control files are owned by a privileged web server account.
This check verifies that the SA or Web Manager controlled account owns the key web server files. These same files, which control the configuration of the web server, and thus its behavior, must also be accessible by the account that runs the web service process. If it exists, the following file need to be owned by a privileged account. .htaccess httpd.conf Use the following commands to determine permissions and ownership of these files: find / -name .htaccess -print -exec ls -l {} \; find / -name httpd.conf -print -exec ls -l {} \; The Web Manager or the SA should own all the system files and directories. The configurable directories can be owned by the WebManager or equivalent user. Permissions on these files should be 660 or more restrictive. If root or an authorized user does not own the web system files and the permissions are not correct, this is a finding.
Discussion
This check verifies that the key web server system configuration files are owned by the SA or Web Manager controlled account. These same files which control the configuration of the web server, and thus its behavior, must also be accessible by the account which runs the web service. If these files are altered by a malicious user, the web server would no longer be under the control of its managers and owners; properties in the web server configuration could be altered to compromise the entire server platform.
Fix
The site needs to ensure that the owner should be the non-privileged web server account or equivalent which runs the web service; however, the group permissions represent those of the user accessing the web site that must execute the directives in .htaccess.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00540 A24: The web server must be configured to explicitly deny access to the OS root.
Enter the following command: find / -name httpd.conf -print -exec cat {} \; Review the httpd.conf file and search for the following directive: Directory For every root directory entry (i.e. <Directory />) ensure the following exists; if not, this is a finding. Require all denied If the statement above is not found in the root directory statement, this is a finding. If any other Require (host, user, ip, etc.) directives are included in the root directory statement, this is a finding.
Discussion
The Apache Directory directive allows for directory specific configuration of access controls and many other features and options. One important usage is to create a default deny policy that does not allow access to Operating System directories and files, except for those specifically allowed. This is done, with denying access to the OS root directory. One aspect of Apache, which is occasionally misunderstood, is the feature of default access. That is, unless you take steps to change it, if the server can find its way to a file through normal URL mapping rules, it can and will serve it to clients. Having a default deny is a predominate security principal, and then helps prevent the unintended access, and we do that in this case by denying access to the OS root directory.
Fix
Edit the httpd.conf file and set the root directory directive as follows: Directory Require all denied
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA060 A24: The HTTP request message body size must be limited.
To view the LimitRequestBody value enter the following command: find / -name httpd.conf -print -exec grep -H -i "LimitRequestBody" {} \; If the value of LimitRequestBody is not set to 1 or greater or does not exist, this is a finding. Note: The default value is set to unlimited.
Discussion
Buffer overflow attacks are carried out by a malicious attacker sending amounts of data that the web server cannot store in a given size buffer. The eventual overflow of this buffer can overwrite system memory. Subsequently an attacker may be able to elevate privileges and take control of the server. The Apache directives listed below limit the size of the various HTTP header sizes thereby limiting the chances for a buffer overflow. The LimitRequestBody directive allows the user to set a limit on the allowed size of an HTTP request message body within the context in which the directive is given (server, per-directory, per-file or per-location). If the client request exceeds that limit, the server will return an error response instead of servicing the request. The size of a normal request message body will vary greatly depending on the nature of the resource and the methods allowed on that resource. CGI scripts typically use the message body for retrieving form information. Implementations of the PUT method will require a value at least as large as any representation that the server wishes to accept for that resource.
Fix
Edit the httpd.conf file and specify a size for the LimitRequestBody directive.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00515 A24: Automatic directory indexing must be disabled.
Enter the following command: httpd -M | grep autoindex If autoindex_module is found, this is a finding.
Discussion
It is recommended this module be disabled.
Fix
Edit the httpd.conf file and disable autoindex_module.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG420 A24: Backup interactive scripts on the production web server are prohibited.
This check is limited to CGI/interactive content and not static HTML. Search for backup copies of CGI scripts on the web server or ask the SA or the Web Administrator if they keep backup copies of CGI scripts on the web server. Common backup file extensions are: *.bak, *.old, *.temp, *.tmp, *.backup, *.??0. This would also apply to .jsp files. find / -name "*.bak" -print find / -name "*.*~" -print find / -name "*.old" -print If files with these extensions are found in either the document directory or the home directory of the web server, this is a finding. If files with these extensions are stored in a repository (not in the document root) as backups for the web server, this is a finding. If files with these extensions have no relationship with web activity, such as a backup batch file for operating system utility, and they are not accessible by the web application, this is not a finding.
Discussion
Copies of backup files will not execute on the server, but they can be read by the anonymous user if special precautions are not taken. Such backup copies contain the same sensitive information as the actual script being executed and, as such, are useful to malicious users. Techniques and systems exist today that search web servers for such files and are able to exploit the information contained in them. Backup copies of files are automatically created by some text editors such as emacs and edit plus. The emacs editor will write a backup file with an extension ~ added to the name of the original file. The edit plus editor will create a .bak file. Of course, this would imply the presence and use of development tools on the web server, which is a finding under WG130. Having backup scripts on the web server provides one more opportunity for malicious persons to view these scripts and use the information found in them.
Fix
Ensure that CGI backup scripts are not left on the production web server.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
WG050 A24: The web server password(s) must be entrusted to the SA or Web Manager.
The reviewer should make a note of the name of the account being used for the web service. This information may be needed later in the SRR. There may also be other server services running related to the web server in support of a particular web application, these passwords must be entrusted to the SA or Web Manager as well. Query the SA or Web Manager to determine if they have the web service password(s). If the web services password(s) are not entrusted to the SA or Web Manager, this is a finding. NOTE: For installations that run as a service, or without a password, the SA or Web Manager having an Admin account on the system would meet the intent of this check.
Discussion
Normally, a service account is established for the web server. This is because a privileged account is not desirable and the server is designed to run for long uninterrupted periods of time. The SA or Web Manager will need password access to the web server to restart the service in the event of an emergency as the web server is not to restart automatically after an unscheduled interruption. If the password is not entrusted to an SA or web manager the ability to ensure the availability of the web server is compromised.
Fix
Ensure the SA or Web Manager are entrusted with the web service(s) password.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00555 A24: The web server must be configured to listen on a specific IP address and port.
Enter the following command: find / -name httpd.conf -print -exec grep -i -H "Listen" {} \; Review the results for the following directive: Listen For any enabled Listen directives ensure they specify both an IP address and port number. If the Listen directive is found with only an IP address, or only a port number specified, this is finding. If the IP address is all zeros (i.e. 0.0.0.0:80 or [::ffff:0.0.0.0]:80, this is a finding. If the Listen directive does not exist, this is a finding.
Discussion
The Apache Listen directive specifies the IP addresses and port numbers the Apache web server will listen for requests. Rather than be unrestricted to listen on all IP addresses available to the system, the specific IP address or addresses intended must be explicitly specified. Specifically a Listen directive with no IP address specified, or with an IP address of zero’s should not be used. Having multiple interfaces on web servers is fairly common, and without explicit Listen directives, the web server is likely to be listening on an inappropriate IP address / interface that were not intended for the web server. Single homed system with a single IP addressed are also required to have an explicit IP address in the Listen directive, in case additional interfaces are added to the system at a later date.
Fix
Edit the httpd.conf file and set the "Listen" directive to listen on a specific IP address and port.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA052 A24: The "-FollowSymLinks" setting must be disabled.
To view the Options value enter the following command: find / -name httpd.conf -print -exec grep -H -i "Options" {} \; Review all uncommented Options statements for the following value: -FollowSymLinks If the value is found with an Options statement, and it does not have a preceding '-', this is a finding. Notes: - If the value does NOT exist, this is a finding. - If all enabled Options statements are set to None this is not a finding.
Discussion
The Options directive configures the web server features that are available in particular directories. The FollowSymLinks option controls the ability of the server to follow symbolic links. A symbolic link allows a file or a directory to be referenced using a symbolic name raising a potential hazard if symbolic linkage is made to a sensitive area. When web scripts are executed and symbolic links are allowed, the web user could be allowed to access locations on the web server that are outside the scope of the web document root or home directory.
Fix
Edit the httpd.conf file and set the value of "FollowSymLinks" to "-FollowSymLinks".
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00510 A24: Web server status module must be disabled.
Enter the following command: httpd -M | grep -e "info" -e "status" If any of the following modules are found, this is a finding. info_module status_module
Discussion
The Apache mod_info module provides information on the server configuration via access to a /server-info URL location, while the mod_status module provides current server performance statistics. While having server configuration and status information available as a web page may be convenient, it is recommended that these modules not be enabled: Once mod_info is loaded into the server, its handler capability is available in per-directory .htaccess files and can leak sensitive information from the configuration directives of other Apache modules such as system paths, usernames/passwords, database names, etc. If mod_status is loaded into the server, its handler capability is available in all configuration files, including per-directory files (e.g., .htaccess) and may have security-related ramifications.
Fix
Edit the httpd.conf file and disable the following modules: info_module status_module
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA030 A24: The httpd.conf MaxSpareServers directive must be set properly.
To view the MaxSpareServers value enter the following command: find / -name httpd.conf -print -exec grep -H -i "MaxSpareServers" {} \; If the value of "MaxSpareServers" is not 10 or less, this is a finding. If the directive does not exist, this is NOT a finding because it will default to 10. It is recommended that the directive be explicitly set to prevent unexpected results if the defaults change with updated software. NOTE: This vulnerability can be documented locally with the ISSM/ISSO if the site has operational reasons for the use of increased value. If the site has this documentation, this should be marked as Not a Finding.
Discussion
These requirements are set to mitigate the effects of several types of denial of service attacks. Although there is some latitude concerning the settings themselves, the requirements attempt to provide reasonable limits for the protection of the web server. If necessary, these limits can be adjusted to accommodate the operational requirement of a given system. From Apache.org: The MaxSpareServers directive sets the desired maximum number of idle child server processes. An idle process is one which is not handling a request. If there are more than MaxSpareServers idle, then the parent process will kill off the excess processes. Tuning of this parameter should only be necessary on very busy sites. Setting this parameter to a large number is almost always a bad idea. If you are trying to set the value equal to or lower than MinSpareServers, Apache HTTP Server will automatically adjust it to MinSpareServers + 1.
Fix
Edit the httpd.conf file and set the value of "MaxSpareServers" to a value of 10 or less, add the directive if it does not exist.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
WA00520 A24: The web server must not be configured as a proxy server.
If the Apache web server is only performing in a proxy server role and does not host any websites nor support any applications, this check is Not Applicable. Enter the following command: httpd -M | grep proxy If any of the following modules are found, this is a finding: proxy_module proxy_ajp_module proxy_balancer_module proxy_ftp_module proxy_http_module proxy_connect_module
Discussion
The Apache proxy modules allow the server to act as a proxy (either forward or reverse proxy) of http and other protocols with additional proxy modules loaded. If the Apache installation is not intended to proxy requests to or from another network then the proxy module should not be loaded. Proxy servers can act as an important security control when properly configured, however a secure proxy server is not within the scope of this benchmark. A web server should be primarily a web server or a proxy server but not both, for the same reasons that other multi-use servers are not recommended. Scanning for web servers that will also proxy requests is a very common attack, as proxy servers are useful for anonymizing attacks on other servers, or possibly proxying requests into an otherwise protected network.
Fix
Edit the httpd.conf file and disable the following modules: proxy_module proxy_ajp_module proxy_balancer_module proxy_ftp_module proxy_http_module proxy_connect_module
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG270 A24: The web server’s htpasswd files (if present) must reflect proper ownership and permissions.
To locate the htpasswd file enter the following command: find / -name htpasswd -print -exec ls -l {} \; Permissions should be r-xr-x--- (mode 550) If permissions on htpasswd are greater than 550, this is a finding. Ownser should be the SA or Web Manager account. If another account has access to this file, this is a finding.
Discussion
In addition to OS restrictions, access rights to files and directories can be set on a web site using the web server software. That is, in addition to allowing or denying all access rights, a rule can be specified that allows or denies partial access rights. For example, users can be given read-only access rights to files, to view the information but not change the files. This check verifies that the htpasswd file is only accessible by system administrators or web managers, with the account running the web service having group permissions of read and execute. htpasswd is a utility used by Netscape and Apache to provide for password access to designated web sites.
Fix
The SA or Web Manager account should own the htpasswd file and permissions should be set to 550.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG080 A24: Installation of a compiler on production web server is prohibited.
Query the SA and the Web Manager to determine if a compiler is present on the server. If a compiler is present, this is a finding. NOTE: If the web server is part of an application suite and a compiler is needed for installation, patching, and upgrading of the suite or if the compiler is embedded and can't be removed without breaking the suite, document the installation of the compiler with the ISSO/ISSM and verify that the compiler is restricted to administrative users only. If documented and restricted to administrative users, this is not a finding.
Discussion
The presence of a compiler on a production server facilitates the malicious user’s task of creating custom versions of programs and installing Trojan Horses or viruses. For example, the attacker’s code can be uploaded and compiled on the server under attack.
Fix
Remove any compiler found on the production web server, but if the compiler program is needed to patch or upgrade an application suite in a production environment or the compiler is embedded and will break the suite if removed, document the compiler installation with the ISSO/ISSM and ensure that the compiler is restricted to only administrative users.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG385 A24: All web server documentation, sample code, example applications, and tutorials must be removed from a production web server.
Query the SA to determine if all directories that contain samples and any scripts used to execute the samples have been removed from the server. Each web server has its own list of sample files. This may change with the software versions, but the following are some examples of what to look for (This should not be the definitive list of sample files, but only an example of the common samples that are provided with the associated web server.): ls -Ll /usr/local/apache2/manual If there is a requirement to maintain these directories at the site for training or other such purposes, have permissions or set the permissions to only allow access to authorized users. If any sample files are found on the web server, this is a finding.
Discussion
Web server documentation, sample code, example applications, and tutorials may be an exploitable threat to a web server. A production web server may only contain components that are operationally necessary (e.g., compiled code, scripts, web-content, etc.). Delete all directories that contain samples and any scripts used to execute the samples. If there is a requirement to maintain these directories at the site on non-production servers for training purposes, have NTFS permissions set to only allow access to authorized users (i.e., web administrators and systems administrators). Sample applications or scripts have not been evaluated and approved for use and may introduce vulnerabilities to the system.
Fix
Ensure sample code and documentation have been removed from the web server.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
WA070 A24: A private web server must be located on a separate controlled access subnet.
Verify the site’s network diagram and visually check the web server, to ensure that the private web server is located on a separate controlled access subnet and is not a part of the public DMZ that houses the public web servers. In addition, the private web server needs to be isolated via a controlled access mechanism from the local general population LAN.
Discussion
Private web servers, which host sites that serve controlled access data, must be protected from outside threats in addition to insider threats. Insider threat may be accidental or intentional but, in either case, can cause a disruption in service of the web server. To protect the private web server from these threats, it must be located on a separate controlled access subnet and must not be a part of the public DMZ that houses the public web servers. It also cannot be located inside the enclave as part of the local general population LAN.
Fix
Isolate the private web server from the public DMZ and separate it from the internal general population LAN.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA056 A24: The MultiViews directive must be disabled.
To view the MultiViews values enter the following command: find / -name httpd.conf -print -exec grep -H -i "MultiViews" {} \; Review all uncommented Options statements for the following value: -MultiViews If the value is found on the Options statement, and it does not have a preceding '-', this is a finding. Notes: - If the value does NOT exist, this is a finding. - If all enabled Options statements are set to None this is not a finding.
Discussion
Directory options directives are directives that can be applied to further restrict access to file and directories. MultiViews is a per-directory option, meaning it can be set with an Options directive within a <Directory> directive. Elsewhere this option is ignored.
Fix
Edit the httpd.conf file and add the '-' to the MultiViews setting, or set the Options directive to None.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA020 A24: The TimeOut directive must be properly set.
To view the TimeOut value enter the following command: find / -name httpd.conf -print -exec grep -H -i "TimeOut" {} \; Verify the value is 300 or less if not, this is a finding. Note:If the directive does not exist, this is not a finding because it will default to 60. It is recommended that the directive be explicitly set to prevent unexpected results should the defaults for any reason be changed (i.e. software update).
Discussion
The TimeOut requirements are set to mitigate the effects of several types of denial of service attacks. Although there is some latitude concerning the settings themselves, the requirements attempt to provide reasonable limits for the protection of the web server. If necessary, these limits can be adjusted to accommodate the operational requirement of a given system.
Fix
Edit the httpd.conf file and set the value of "Timeout" to 300 seconds or less.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00550 A24: The TRACE method must be disabled.
Enter the following command: find / -name httpd.conf -print -exec cat {} \; Review the results for the following directive: TraceEnable For any enabled TraceEnable directives ensure they are part of the server level configuration(i.e. not nested in a <Directory> or <Location> directive). Also ensure that the TraceEnable directive is set to "Off". If the TraceEnable directive is not part of the server level configuration and/or is not set to "Off", this is a finding. If the directive does not exist in the conf file, this is a finding because the default value is "On".
Discussion
Diagnostics help establish a history of activities, and can be useful in detecting attack attempts or determining tuning adjustments to improve server availability. Trace logs are essential to the investigation and prosecution of unauthorized access to web server software and data. However, in standard production operations, use of diagnostics may reveal undiscovered vulnerabilities and ultimately, to compromise of the data. Because of the potential for abuse, the HTTP Trace method should be disabled.
Fix
Edit the httpd.conf file and add or set the value of EnableTrace to "Off".
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG220 A24: Web administration tools must be restricted to the web manager and the web manager’s designees.
Determine which tool or control file is used to control the configuration of the web server. If the control of the web server is done via control files, verify who has update access to them. If tools are being used to configure the web server, determine who has access to execute the tools. If accounts other than the SA, the web manager, or the web manager designees have access to the web administration tool or control files, this is a finding.
Discussion
All automated information systems are at risk of data loss due to disaster or compromise. Failure to provide adequate protection to the administration tools creates risk of potential theft or damage that may ultimately compromise the mission. Adequate protection ensures that server administration operates with less risk of losses or operations outages. The key web service administrative and configuration tools must be accessible only by the authorized web server administrators. All users granted this authority must be documented and approved by the ISSO. Access to the IIS Manager will be limited to authorized users and administrators.
Fix
Restrict access to the web administration tool to only the web manager and the web manager’s designees.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00505 A24: Web Distributed Authoring and Versioning (WebDAV) must be disabled.
Enter the following command: httpd -M | grep dav If any of the following modules are found, this is a finding. dav_module dav_fs_module dav_lock_module
Discussion
The Apache mod_dav and mod_dav_fs modules support WebDAV ('Web-based Distributed Authoring and Versioning') functionality for Apache. WebDAV is an extension to the HTTP protocol which allows clients to create, move, and delete files and resources on the web server. WebDAV is not widely used, and has serious security concerns as it may allow clients to modify unauthorized files on the web server. Therefore, the WebDav modules mod_dav and mod_dav_fs should be disabled.
Fix
Edit the httpd.conf file and disable the following modules: dav_module dav_fs_module dav_lock_module
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA058 A24: Directory indexing must be disabled on directories not containing index files.
To view the Indexes value enter the following command: find / -name httpd.conf -print -exec grep -H -i "Indexes" {} \; Review all uncommented Options statements for the following value: -Indexes If the value is found on the Options statement, and it does not have a preceding '-', this is a finding. Notes: - If the value does NOT exist, this is a finding. - If all enabled Options statements are set to None this is not a finding.
Discussion
Directory options directives are directives that can be applied to further restrict access to file and directories. If a URL which maps to a directory is requested, and there is no DirectoryIndex (e.g., index.html) in that directory, then mod_autoindex will return a formatted listing of the directory which is not acceptable.
Fix
Edit the httpd.conf file and add an '-' to the Indexes setting, or set the Options directive to None.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00500 A24: Active software modules must be minimized.
Enter the following command: httpd -M This will provide a list of the loaded modules. Validate that all displayed modules are required for operations. If any module is not required for operation, this is a finding. Note: The following modules are needed for basic web function and do not need to be reviewed: core_module http_module so_module mpm_prefork_module
Discussion
Modules are the source of Apache httpd servers core and dynamic capabilities. Thus not every module available is needed for operation. Most installations only need a small subset of the modules available. By minimizing the enabled modules to only those that are required, we reduce the number of doors and have therefore reduced the attack surface of the web site. Likewise having fewer modules means less software that could have vulnerabilities.
Fix
Disable any modules that are not needed.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00535 A24: The score board file must be properly secured.
To determine the location and permissions of the score board file enter the following command: find / -name ScoreBoard -print -exec ls -lL {} \; If the permissions on the file are not set to 644 or less, this is a finding.
Discussion
The ScoreBoardfile directive sets a file path which the server will use for Inter-Process Communication (IPC) among the Apache processes. If the directive is specified, then Apache will use the configured file for the inter-process communication. Therefore if it is specified it needs to be located in a secure directory. If the ScoreBoardfile is placed in a writable directory, other accounts could create a denial of service attack and prevent the server from starting by creating a file with the same name, and or users could monitor and disrupt the communication between the processes by reading and writing to the file.
Fix
The scoreboard file is created when the server starts, and is deleted when it shuts down, set the permissions during the creation of the file.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA050 A24: All interactive programs must be placed in a designated directory with appropriate permissions.
Search for the unnecessary CGI programs which may be found in the directories configured with ScriptAlias, Script or other Script* directives. Often, CGI directories are named cgi-bin. Also, CGI AddHandler or SetHandler directives may also be in use for specific handlers such as perl, python and PHP. To search the httpd.conf file for Options enter the following command: find / -name httpd.conf -print -exec grep -H -i "Options" {} \; If the value for Options is returned with a ExecCGI (no +) this is a finding.
Discussion
Directory options directives are directives that can be applied to further restrict access to file and directories. The Options directive controls which server features are available in a particular directory. The ExecCGI option controls the execution of CGI scripts using mod_cgi. This needs to be restricted to only the directory intended for script execution.
Fix
Locate any cgi-bin files and directories enabled in the Apache configuration via Script, ScriptAlias or other Script* directives. Remove the printenv default CGI in cgi-bin directory if it is installed. rm $APACHE_PREFIX/cgi-bin/printenv. Remove the test-cgi file from the cgi-bin directory if it is installed. rm $APACHE_PREFIX/cgi-bin/test-cgi. Review and remove any other cgi-bin files which are not needed for business purposes.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG300 A24: Web server system files must conform to minimum file permission requirements.
Apache directory and file permissions and ownership should be set per the following table. The installation directories may vary from one installation to the next. If used, the WebAdmins group should contain only accounts of persons authorized to manage the web server configuration, otherwise the root group should own all Apache files and directories. If the files and directories are not set to the following permissions or more restrictive, this is a finding. To locate the ServerRoot directory enter the following command. find / -name httpd.conf -print -exec grep -H -i "^ServerRoot" {} \; /Server root dir apache root WebAdmin 771/660 /apache/cgi-bin root WebAdmin 775/775 /apache/bin root WebAdmin 550/550 /apache/config root WebAdmin 770/660 /apache/htdocs root WebAdmin 775/664 /apache/logs root WebAdmin 750/640 NOTE: The permissions are noted as directories / files
Discussion
This check verifies that the key web server system configuration files are owned by the SA or the web administrator controlled account. These same files that control the configuration of the web server, and thus its behavior, must also be accessible by the account that runs the web service. If these files are altered by a malicious user, the web server would no longer be under the control of its managers and owners; properties in the web server configuration could be altered to compromise the entire server platform.
Fix
Use the chmod/chown/chgrp commands (as appropriate) to set permissions on the web server system directories and files as follows. root dir apache root WebAdmin 771/660 /apache/cgi-bin root WebAdmin 775/775 /apache/bin root WebAdmin 550/550 /apache/config root WebAdmin 770/660 /apache/htdocs root WebAdmin 775/664 /apache/logs root WebAdmin 750/640
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA064 A24: The HTTP request header field size must be limited.
To view the LimitRequestFieldSize value enter the following command: find / -name httpd.conf -print -exec grep -H -i "LimitRequestFieldSize" {} \; If no LimitRequestFieldSize directives exist, this is a finding. Although the default value is 8190, this directive must be explicitly set. If the value of LimitRequestFieldSize is not set to 8190, this is a finding.
Discussion
Buffer overflow attacks are carried out by a malicious attacker sending amounts of data that the web server cannot store in a given size buffer. The eventual overflow of this buffer can overwrite system memory. Subsequently an attacker may be able to elevate privileges and take control of the server. This Apache directives limits the size of the various HTTP header sizes thereby limiting the chances for a buffer overflow. The LimitRequestFieldSize directive allows the server administrator to reduce or increase the limit on the allowed size of an HTTP request header field. A server needs this value to be large enough to hold any one header field from a normal client request. The size of a normal request header field will vary greatly among different client implementations, often depending upon the extent to which a user has configured their browser to support detailed content negotiation. SPNEGO authentication headers can be up to 12392 bytes. This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks.
Fix
Edit the httpd.conf file and set the LimitRequestFieldSize directive to 8190 or other approved value, add the directive if it does not exist.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00545 A24: Web server options for the OS root must be disabled.
Enter the following command: find / -name httpd.conf -print -exec cat {} \; Review the httpd.conf file and search for the following directive: Directory For every root directory entry (i.e. <Directory />) ensure the following exists: Options None If the statement above is not found in the root directory statement, this is a finding. If Allow directives are included in the root directory statement, this is a finding. If the root directory statement is not found at all, this is a finding.
Discussion
The Apache Options directive allows for specific configuration of options, including execution of CGI, following symbolic links, server side includes, and content negotiation. The Options directive for the root OS level is used to create a default minimal options policy that allows only the minimal options at the root directory level. Then for specific web sites or portions of the web site, options may be enabled as needed and appropriate. No options should be enabled and the value for the Options Directive should be None.
Fix
Ensure the root directory has the appropriate Options assignment.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA230 A24: The Web site software used with the web server must have all applicable security patches applied and documented.
Query the web administrator to determine if the site has a detailed process as part of its configuration management plan to stay compliant with all security-related patches. Proposed Questions: How does the SA stay current with web server vendor patches? How is the SA notified when a new security patch is issued by the vendor? (Exclude the IAVM.) What is the process followed for applying patches to the web server? If the site is not in compliance with all applicable security patches, this is a finding.
Discussion
The IAVM process does not address all patches that have been identified for the host operating system or, in this case, the web server software environment. Many vendors have subscription services available to notify users of known security threats. The site needs to be aware of these fixes and make determinations based on local policy and what software features are installed, if these patches need to be applied. In some cases, patches also apply to middleware and database systems. Maintaining the security of web servers requires frequent reviews of security notices. Many security notices mandate the installation of a software patch to overcome security vulnerabilities. SAs and ISSOs should regularly check the vendor support web site for patches and information related to the web server software. All applicable security patches will be applied to the operating system and to the web server software. Security patches are deemed applicable if the product is installed, even if it is not used or is disabled.
Fix
Establish a detailed process as part of the configuration management plan to stay compliant with all web server security-related patches.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA120 A24: Administrative users and groups that have access rights to the web server must be documented.
Proposed Questions: How many user accounts are associated with the Web server operation and maintenance? Where are these accounts documented? Use the command line utility more /etc/passwd to identify the accounts on the web server. Query the SA or Web Manager regarding the use of each account and each group. If the documentation does not match the users and groups found on the server, this is a finding.
Discussion
There are typically several individuals and groups that are involved in running a production web server. These accounts must be restricted to only those necessary to maintain web services, review the server’s operation, and the operating system. By minimizing the amount of user and group accounts on a web server the total attack surface of the server is minimized. Additionally, if the required accounts aren’t documented no known standard is created. Without a known standard the ability to identify required accounts is diminished, increasing the opportunity for error when such a standard is needed (i.e. COOP, IR, etc.).
Fix
Document the administrative users and groups which have access rights to the web server in the web site SOP or in an equivalent document.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
WG200 A24: Administrators must be the only users allowed access to the directory tree, the shell, or other operating system functions and utilities.
Obtain a list of the user accounts for the system, noting the priviledges for each account. Verify with the system administrator or the ISSO that all privileged accounts are mission essential and documented. Verify with the system administrator or the ISSO that all non-administrator access to shell scripts and operating system functions are mission essential and documented. If undocumented privileged accounts are found, this is a finding. If undocumented access to shell scripts or operating system functions is found, this is a finding.
Discussion
As a rule, accounts on a web server are to be kept to a minimum. Only administrators, web managers, developers, auditors, and web authors require accounts on the machine hosting the web server. This is in addition to the anonymous web user account. The resources to which these accounts have access must also be closely monitored and controlled. Only the SA needs access to all the system’s capabilities, while the web administrator and associated staff require access and control of the web content and web server configuration files. The anonymous web user account must not have access to system resources as that account could then control the server.
Fix
Ensure non-administrators are not allowed access to the directory tree, the shell, or other operating system functions and utilities.
Rating Info
DISA Cat I. NIST impact 4.
Expert Comment
None
WA000-WWA066 A24: The HTTP request line must be limited.
To view the LimitRequestLine value enter the following command: find / -name httpd.conf -print -exec grep -H -i "LimitRequestLine" {} \; If the value of LimitRequestLine is not set to 8190, this is a finding. If no LimitRequestLine directives exist, this is a finding. Although the default value is 8190, this directive must be explicitly set.
Discussion
Buffer overflow attacks are carried out by a malicious attacker sending amounts of data that the web server cannot store in a given size buffer. The eventual overflow of this buffer can overwrite system memory. Subsequently an attacker may be able to elevate privileges and take control of the server. This Apache directives limits the size of the various HTTP header sizes thereby limiting the chances for a buffer overflow. The LimitRequestLine directive allows the server administrator to reduce or increase the limit on the allowed size of a client's HTTP request-line. Since the request-line consists of the HTTP method, URI, and protocol version, the LimitRequestLine directive places a restriction on the length of a request-URI allowed for a request on the server. A server needs this value to be large enough to hold any of its resource names, including any information that might be passed in the query part of a GET request. This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks.
Fix
Edit the httpd.conf file and set the LimitRequestLine directive to 8190 or other approved value, add the directive if it does not exist.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG345 A24: The web server must remove all export ciphers from the cipher suite.
Locate the Apache httpd.conf and ssl.conf file if available. Open the httpd.conf and ssl.conf file with an editor and search for the following uncommented directive: SSLCipherSuite For all enabled SSLCipherSuite directives, ensure the cipher specification string contains the kill cipher from list option for all export cipher suites, i.e., !EXP. If the SSLCipherSuite directive does not contain !EXP or there are no enabled SSLCipherSuite directives, this is a finding.
Discussion
During the initial setup of a Transport Layer Security (TLS) connection to the web server, the client sends a list of supported cipher suites in order of preference. The web server will reply with the cipher suite it will use for communication from the client list. If an attacker can intercept the submission of cipher suites to the web server and place, as the preferred cipher suite, a weak export suite, the encryption used for the session becomes easy for the attacker to break, often within minutes to hours.
Fix
Update the cipher specification string for all enabled SSLCipherSuite directives to include !EXP.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG330 A24: A public web server must limit email to outbound only.
To determine if email applications are excepting incoming connections (on standard ports)enter the following command: telnet localhost 25 review the command results, If an e-mail program is installed and that program has been configured to accept inbound email, this is a finding.
Discussion
Incoming E-mail has been known to provide hackers with access to servers. Disabling the incoming mail service prevents this type of attacks. Additionally, Email represents the main use of the Internet. It is specialized application that requires the dedication of server resources. To combine this type of transaction processing function with the file serving role of the web server creates an inherent conflict. Supporting mail services on a web server opens the server to the risk of abuse as an email relay.
Fix
Configure the email application to not allow incoming connections.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA062 A24: The HTTP request header fields must be limited.
To view the LimitRequestFields value enter the following command: find / -name httpd.conf -print -exec grep -H -i "LimitRequestFields" {} \; If the value of LimitRequestFields is not set to a value greater than 0, this is a finding. Note: The default value for LimitRequestFields is 100.
Discussion
Buffer overflow attacks are carried out by a malicious attacker sending amounts of data that the web server cannot store in a given size buffer. The eventual overflow of this buffer can overwrite system memory. Subsequently an attacker may be able to elevate privileges and take control of the server. This Apache directives limits the size of the various HTTP header sizes thereby limiting the chances for a buffer overflow. The LimitRequestFields directive allows the server administrator to modify the limit on the number of request header fields allowed in an HTTP request. A server needs this value to be larger than the number of fields that a normal client request might include. The number of request header fields used by a client rarely exceeds 20, but this may vary among different client implementations, often depending upon the extent to which a user has configured their browser to support detailed content negotiation. Optional HTTP extensions are often expressed using request header fields. This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks. The value should be increased if normal clients see an error response from the server that indicates too many fields were sent in the request.
Fix
Edit the httpd.conf file and set the LimitRequestFields directive to a value greater than 0.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00530 A24: The process ID (PID) file must be properly secured.
Enter the following command: find / -name httpd.conf -print -exec grep -H -i "PidFile" {} \; Note the location of the PID file. If the PidFile directive is not found enabled in the conf file, use /logs as the directory containing the Scoreboard file. Verify the permissions and ownership on the folder containing the PID file. If any user accounts other than root, auditor, or the account used to run the web server have permission to, or ownership of, this folder, this is a finding. If the PID file is located in the web server DocumentRoot this is a finding.
Discussion
The PidFile directive sets the file path to the process ID file to which the server records the process id of the server, which is useful for sending a signal to the server process or for checking on the health of the process. If the PidFile is placed in a writable directory, other accounts could create a denial of service attack and prevent the server from starting by creating a PID file with the same name.
Fix
Modify the location, permissions, and/or ownership for the PID file folder.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00547 A24: The ability to override the access configuration for the OS root directory must be disabled.
Enter the following command: find / -name httpd.conf -print -exec cat {} \; Review the httpd.conf file and search for the following directive: Directory For every root directory entry (i.e. <Directory />) ensure the following exists: AllowOverride None If the statement above is not found in the root directory statement, this is a finding. If Allow directives are included in the root directory statement, this is a finding. If the root directory statement is not found at all, this is a finding.
Discussion
The Apache OverRide directive allows for .htaccess files to be used to override much of the configuration, including authentication, handling of document types, auto generated indexes, access control, and options. When the server finds an .htaccess file (as specified by AccessFileName) it needs to know which directives declared in that file can override earlier access information. When this directive is set to None, then .htaccess files are completely ignored. In this case, the server will not even attempt to read .htaccess files in the file system. When this directive is set to All, then any directive which has the .htaccess Context is allowed in .htaccess files.
Fix
Edit the httpd.conf file and add or set the value of AllowOverride to "None".
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG520 A24: Web server and/or operating system information must be protected.
Enter the following command: find / -name httpd.conf -print -exec grep -H -i "ServerTokens" {} \; The directive ServerTokens must be set to "Prod" (ex. ServerTokens Prod). This directive controls whether Server response header field that is sent back to clients that includes a description of the OS-type of the server as well as information about compiled-in modules. If the web server or operating system information are sent to the client via the server response header or the directive does not exist, this is a finding. Note: The default value is set to Full.
Discussion
The web server response header of an HTTP response can contain several fields of information including the requested HTML page. The information included in this response can be web server type and version, operating system and version, and ports associated with the web server. This provides the malicious user valuable information without the use of extensive tools.
Fix
Edit the httpd.conf file and ensure the ServerTokens directive is set to Prod.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
WA140 A24: Web server content and configuration files must be part of a routine backup program.
Interview the Information Systems Security Officer (ISSO), SA, Web Manager, Webmaster or developers as necessary to determine whether or not a tested and verifiable backup strategy has been implemented for web server software as well as all web server data files. Proposed Questions: Who maintains the backup and recovery procedures? Do you have a copy of the backup and recovery procedures? Where is the off-site backup location? Is the contingency plan documented? When was the last time the contingency plan was tested? Are the test dates and results documented? If there is not a backup and recovery process for the web server, this is a finding.
Discussion
Backing up web server data and web server application software after upgrades or maintenance ensures that recovery can be accomplished up to the current version. It also provides a means to determine and recover from subsequent unauthorized changes to the software and data. A tested and verifiable backup strategy will be implemented for web server software as well as all web server data files. Backup and recovery procedures will be documented and the Web Manager or SA for the specific application will be responsible for the design, test, and implementation of the procedures. The site will have a contingency processing plan/disaster recovery plan that includes web servers. The contingency plan will be periodically tested in accordance with DoDI 8500.2 requirements. The site will identify an off-site storage facility in accordance with DoDI 8500.2 requirements. Off-site backups will be updated on a regular basis and the frequency will be documented in the contingency plan.
Fix
Document the backup procedures.
Rating Info
DISA Cat III. NIST impact 2.
Expert Comment
None
WA000-WWA026 A24: The httpd.conf StartServers directive must be set properly.
To view the StartServers value enter the following command: find / -name httpd.conf -print -exec grep -H -i "StartServers" {} \; If the value of "StartServers" is not between 5 and 10, this is a finding. If the directive does not exist, this is NOT a finding because it will default to 5. It is recommended that the directive be explicitly set to prevent unexpected results if the defaults change with updated software. NOTE: This vulnerability can be documented locally with the ISSM/ISSO if the site has operational reasons for the use of increased or decreased value. If the site has this documentation, this should be marked as Not a Finding.
Discussion
These requirements are set to mitigate the effects of several types of denial of service attacks. Although there is some latitude concerning the settings themselves, the requirements attempt to provide reasonable limits for the protection of the web server. If necessary, these limits can be adjusted to accommodate the operational requirement of a given system. From Apache.org: The StartServers directive sets the number of child server processes created on startup. As the number of processes is dynamically controlled depending on the load, there is usually little reason to adjust this parameter. The default value differs from MPM to MPM. worker and event default to StartServers 3; prefork defaults to 5; mpmt_os2 defaults to 2.
Fix
Edit the httpd.conf file and set the value of "StartServer" to a value between 5 and 10, add the directive if it does not exist.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WG355 A24: A private web server’s list of CAs in a trust hierarchy must lead to an authorized DoD PKI Root CA.
Enter the following command: find / -name ssl.conf -print -exec grep "SSLCACertificateFile" {} \; Review the results to determine the path of the SSLCACertificateFile cat /path/of/ca-bundle.crt Examine the contents of this file to determine if the trusted CAs are DoD approved. If the trusted CA that is used to authenticate users to the web site does not lead to an approved DoD CA, this is a finding. NOTE: There are non DoD roots that must be on the server in order for it to function. Some applications, such as anti-virus programs, require root CAs to function. DoD approved certificate can include the External Certificate Authorities (ECA), if approved by the DAA.
Discussion
A PKI certificate is a digital identifier that establishes the identity of an individual or a platform. A server that has a certificate provides users with third-party confirmation of authenticity. Most web browsers perform server authentication automatically and the user is notified only if the authentication fails. The authentication process between the server and the client is performed using the SSL/TLS protocol. Digital certificates are authenticated, issued, and managed by a trusted Certificate Authority (CA). The use of a trusted certificate validation hierarchy is crucial to the ability to control access to a site’s server and to prevent unauthorized access. Only DoD-approved PKIs will be utilized.
Fix
Configure the web server’s trust store to trust only DoD-approved PKIs (e.g., DoD PKI, DoD ECA, and DoD-approved external partners).
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA000-WWA028 A24: The httpd.conf MinSpareServers directive must be set properly.
To view the MinSpareServers value enter the following command: find / -name httpd.conf -print -exec grep -H -i "MinSpareServers" {} \; If the value of "MinSpareServers" is not between 5 and 10, this is a finding. If the directive does not exist, this is NOT a finding because it will default to 5. It is recommended that the directive be explicitly set to prevent unexpected results if the defaults change with updated software. NOTE: This vulnerability can be documented locally with the ISSM/ISSO if the site has operational reasons for the use of increased or decreased value. If the site has this documentation, this should be marked as Not a Finding.
Discussion
These requirements are set to mitigate the effects of several types of denial of service attacks. Although there is some latitude concerning the settings themselves, the requirements attempt to provide reasonable limits for the protection of the web server. If necessary, these limits can be adjusted to accommodate the operational requirement of a given system. From Apache.org: The MinSpareServers directive sets the desired minimum number of idle child server processes. An idle process is one which is not handling a request. If there are fewer than MinSpareServers idle, then the parent process creates new children: It will spawn one, wait a second, then spawn two, wait a second, then spawn four, and it will continue exponentially until it is spawning 32 children per second. It will stop whenever it satisfies the MinSpareServers setting. Tuning of this parameter should only be necessary on very busy sites. Setting this parameter to a large number is almost always a bad idea.
Fix
Edit the httpd.conf file and set the value of "MinSpareServers" to a value between 5 and 10, add the directive if it does not exist.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00560 A24: The URL-path name must be set to the file path name or the directory path name.
Enter the following command: find / -name httpd.conf -print -exec grep -i -H "ScriptAlias" {} \; If any enabled ScriptAlias directive do not have matching URL-path and file-path or directory-path entries, this is a finding.
Discussion
The ScriptAlias directive controls which directories the Apache server "sees" as containing scripts. If the directive uses a URL-path name that is different than the actual file system path, the potential exists to expose the script source code.
Fix
Edit the httpd.conf file and set the ScriptAlias URL-path and file-path or directory-path entries.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00565 A24: HTTP request methods must be limited.
Enter the following command: find / -name httpd.conf -print -exec cat {} \; For every enabled <Directory> directive (except root), ensure the following entry exists: Require all granted <LimitExcept GET POST OPTIONS> Require all denied </LimitExcept> If the statement above is found in the root directory statement (i.e. <Directory />), this is a finding. If the statement above is found enabled but without the appropriate LimitExcept or Require statement, this is a finding. If the statement is not found inside an enabled <Directory> directive, this is a finding. Note: If the LimitExcept statement above is operationally limiting. This should be explicitly documented with the Web Manager, at which point this can be considered not a finding.
Discussion
The HTTP 1.1 protocol supports several request methods which are rarely used and potentially high risk. For example, methods such as PUT and DELETE are rarely used and should be disabled in keeping with the primary security principal of minimize features and options. Also since the usage of these methods is typically to modify resources on the web server, they should be explicitly disallowed. For normal web server operation, you will typically need to allow only the GET, HEAD and POST request methods. This will allow for downloading of web pages and submitting information to web forms. The OPTIONS request method will also be allowed as it is used to request which HTTP request methods are allowed.
Fix
Edit the https.conf file and add the following entries for every enabled directory except root. Require all granted <LimitExcept GET POST OPTIONS> Require all denied </LimitExcept>
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None
WA00525 A24: User specific directories must not be globally enabled.
Enter the following command: httpd -M | grep userdir If userdir_module is listed, this is a finding.
Discussion
The UserDir directive must be disabled so that user home directories are not accessed via the web site with a tilde (~) preceding the username. The directive also sets the path name of the directory that will be accessed. The user directories should not be globally enabled since it allows anonymous access to anything users may want to share with other users on the network. Also consider that every time a new account is created on the system, there is potentially new content available via the web site.
Fix
Edit the httpd.conf file and disable userdir_module.
Rating Info
DISA Cat II. NIST impact 3.
Expert Comment
None