audit2why - Online in the Cloud

PROGRAM:

NAME

audit2allow - generate SELinux policy allow/dontaudit rules from logs of denied operations

audit2why - translates SELinux audit messages into a description of why the access was
denied (audit2allow -w)

SYNOPSIS

audit2allow [options]

OPTIONS

-a | --all
Read input from audit and message log, conflicts with -i

-b | --boot
Read input from audit messages since last boot conflicts with -i

-d | --dmesg
Read input from output of /bin/dmesg. Note that all audit messages are not
available via dmesg when auditd is running; use "ausearch -m avc | audit2allow" or
"-a" instead.

-D | --dontaudit
Generate dontaudit rules (Default: allow)

-h | --help
Print a short usage message

-i <inputfile> | --input <inputfile>
read input from <inputfile>

-l | --lastreload
read input only after last policy reload

-m <modulename> | --module <modulename>
Generate module/require output <modulename>

-M <modulename>
Generate loadable module package, conflicts with -o

-p <policyfile> | --policy <policyfile>
Policy file to use for analysis

-o <outputfile> | --output <outputfile>
append output to <outputfile>

-r | --requires
Generate require output syntax for loadable modules.

-N | --noreference
Do not generate reference policy, traditional style allow rules. This is the
default behavior.

-R | --reference
Generate reference policy using installed macros. This attempts to match denials
against interfaces and may be inaccurate.

-w | --why
Translates SELinux audit messages into a description of why the access was denied

-v | --verbose
Turn on verbose output

DESCRIPTION

This utility scans the logs for messages logged when the system denied permission for
operations, and generates a snippet of policy rules which, if loaded into policy, might
have allowed those operations to succeed. However, this utility only generates Type
Enforcement (TE) allow rules. Certain permission denials may require other kinds of
policy changes, e.g. adding an attribute to a type declaration to satisfy an existing
constraint, adding a role allow rule, or modifying a constraint. The audit2why(8) utility
may be used to diagnose the reason when it is unclear.

Care must be exercised while acting on the output of this utility to ensure that the
operations being permitted do not pose a security threat. Often it is better to define new
domains and/or types, or make other structural changes to narrowly allow an optimal set of
operations to succeed, as opposed to blindly implementing the sometimes broad changes
recommended by this utility. Certain permission denials are not fatal to the
application, in which case it may be preferable to simply suppress logging of the denial
via a 'dontaudit' rule rather than an 'allow' rule.

EXAMPLE

NOTE: These examples are for systems using the audit package. If you do
not use the audit package, the AVC messages will be in /var/log/messages.
Please substitute /var/log/messages for /var/log/audit/audit.log in the
examples.

Using audit2allow to generate module policy

$ cat /var/log/audit/audit.log | audit2allow -m local > local.te
$ cat local.te
module local 1.0;

require {
class file { getattr open read };

type myapp_t;
type etc_t;
};

allow myapp_t etc_t:file { getattr open read };
<review local.te and customize as desired>

Using audit2allow to generate module policy using reference policy

$ cat /var/log/audit/audit.log | audit2allow -R -m local > local.te
$ cat local.te
policy_module(local, 1.0)

gen_require(`
type myapp_t;
type etc_t;
};

files_read_etc_files(myapp_t)
<review local.te and customize as desired>

Building module policy using Makefile

# SELinux provides a policy devel environment under
# /usr/share/selinux/devel including all of the shipped
# interface files.
# You can create a te file and compile it by executing

$ make -f /usr/share/selinux/devel/Makefile local.pp

# This make command will compile a local.te file in the current
# directory. If you did not specify a "pp" file, the make file
# will compile all "te" files in the current directory. After
# you compile your te file into a "pp" file, you need to install
# it using the semodule command.

$ semodule -i local.pp

Building module policy manually

# Compile the module
$ checkmodule -M -m -o local.mod local.te

# Create the package
$ semodule_package -o local.pp -m local.mod

# Load the module into the kernel
$ semodule -i local.pp

Using audit2allow to generate and build module policy

$ cat /var/log/audit/audit.log | audit2allow -M local
Generating type enforcement file: local.te

Compiling policy: checkmodule -M -m -o local.mod local.te
Building package: semodule_package -o local.pp -m local.mod

******************** IMPORTANT ***********************

In order to load this newly created policy package into the kernel,
you are required to execute

semodule -i local.pp

Using audit2allow to generate monolithic (non-module) policy

$ cd /etc/selinux/$SELINUXTYPE/src/policy
$ cat /var/log/audit/audit.log | audit2allow >> domains/misc/local.te
$ cat domains/misc/local.te
allow cupsd_config_t unconfined_t:fifo_file { getattr ioctl };
<review domains/misc/local.te and customize as desired>
$ make load

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