Detections
Analytics
6.3.3 Ensure cryptographic mechanisms are used to protect the integrity of audit tools
Information
Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators.aide.conf is case-sensitive. Leading and trailing white spaces are ignored. Each config lines must end with new line.
AIDE uses the backslash character () as escape character for ' ' (space), '@' and '' (backslash) (e.g. ' ' or '@'). To literally match a '' in a file path with a regular expression you have to escape the backslash twice (i.e. '\').
There are three types of lines in aide.conf :
- The configuration options which are used to set configuration parameters and define groups.
- (restricted) rules that are used to indicate which files are added to the database.
- Macro lines define or undefine variables within the config file. Note: Lines beginning with # are ignored as comments.
@@include
<FILE>
- Include
<FILE>
.
- The content of the file is used as if it were inserted in this part of the config file.
- The maximum depth of nested includes is 16.
`@@include
<DIRECTORY>
<REGEX>
- [RULE_PREFIX] (added in AIDE v0.17)
- Include all (regular) files found in <DIRECTORY> matching regular expression <REGEX> (sub-directories are ignored).
- The file are included in lexical sort order.
- If RULE_PREFIX is set, all rules included by the statement are prefixed with given <RULE_PREFIX> (added in AIDE v0.18). Prefixes from nested include statements are concatenated.
- The content of the files is used as if it were inserted in this part of the config file.
@x_include :
- is identical to @@include except that if a config file is executable is is run and the output is used as config.
- If the executable file exits with status greater than zero or writes to stderr aide stops with an error.
- For security reasons
<DIRECTORY>
and each executable config file must be owned by the current user or root. They must not be group- or world-writable.
- @@x_include _<FILE>_ (added in AIDE v0.17):
- `@@x_include
<DIRECTORY>
<REGEX>
[RULE_PREFIX] (added in AIDE v0.17)
@@x_include_setenv
<VAR>
<VALUE>
(added in AIDE v0.17)
- Adds the variable
<VAR>
with the value
<VALUE>
to the environment used for config file execution.
- Environment variable names are limited to alphanumeric characters (A-Za-z0-9) and the underscore '_' and must not begin with a digit.
Protecting the integrity of the tools used for auditing purposes is a critical step toward ensuring the integrity of audit information. Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity.
Attackers may replace the audit tools or inject code into the existing tools with the purpose of providing the capability to hide or erase system activity from the audit logs.
Audit tools should be cryptographically signed in order to provide the capability to identify when the audit tools have been modified, manipulated, or replaced. An example is a checksum hash of the file or files.
Solution
Run the following command to determine the absolute path to the non-symlinked version on the audit tools:# readlink -f /sbin
The output will be either /usr/sbin - OR - /sbin Ensure the correct path is used.
Edit /etc/aide/aide.conf and add or update the following selection lines replacing <PATH> with the correct path returned in the command above:
# Audit Tools
<PATH>/auditctl p+i+n+u+g+s+b+acl+xattrs+sha512
<PATH>/auditd p+i+n+u+g+s+b+acl+xattrs+sha512
<PATH>/ausearch p+i+n+u+g+s+b+acl+xattrs+sha512
<PATH>/aureport p+i+n+u+g+s+b+acl+xattrs+sha512
<PATH>/autrace p+i+n+u+g+s+b+acl+xattrs+sha512
<PATH>/augenrules p+i+n+u+g+s+b+acl+xattrs+sha512
Example
# printf '%s
' "" "# Audit Tools" "$(readlink -f /sbin/auditctl) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/auditd) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/ausearch) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/aureport) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/autrace) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/augenrules) p+i+n+u+g+s+b+acl+xattrs+sha512" >> /etc/aide/aide.conf
Note: - IF - /etc/aide/aide.conf includes a @@x_include statement:
-
<DIRECTORY>
and each executable config file must be owned by the current user or root
- They must not be group or world-writable
Example:
@@x_include /etc/aide.conf.d ^[a-zA-Z0-9_-]+$
See Also
Item Details
Audit Name: CIS Debian Linux 12 v1.1.0 L2 Server
Category: SYSTEM AND INFORMATION INTEGRITY
References: 800-53|SI-7
Plugin: Unix
Control ID: 5a0cb22f3018f71c45b9a1082a76ef0f05e8afeb9aba5047adb2a0dbbcfd3d76