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SELinux refpolicy详解（5）

news 来源：原创 2024/5/20 15:09:18

接前一篇文章：SELinux refpolicy详解（4）

三、refpolicy内容详解

1. README

文件路径：refpolicy源码根目录/README。

文件内容如下：

1) Reference Policy make targets:General Make targets:install-src		Install the policy sources into/etc/selinux/NAME/src/policy, where NAME is defined inthe Makefile.  If not defined, the TYPE, as defined inthe Makefile, is used.  The default NAME is refpolicy.A pre-existing source policy will be moved to/etc/selinux/NAME/src/policy.bak.conf			Regenerate policy.xml, and update/create modules.confand booleans.conf.  This should be done after addingor removing modules, or after running the bare target.If the configuration files exist, their settings willbe preserved.  This must be ran on policy sources thatare checked out from the CVS repository before they canbe used.clean			Delete all temporary files, compiled policies,and file_contexts.  Configuration files are left intact.bare			Do the clean make target and also delete configurationfiles, web page documentation, and policy.xml.html			Regenerate policy.xml and create web page documentationin the doc/html directory.Make targets specific to modular (loadable modules) policies:base			Compile and package the base module.  This is thedefault target for modular policies.modules			Compile and package all Reference Policy modulesconfigured to be built as loadable modules.MODULENAME.pp		Compile and package the MODULENAME Reference Policymodule.all			Compile and package the base module and all ReferencePolicy modules configured to be built as loadablemodules.install			Compile, package, and install the base module andReference Policy modules configured to be built asloadable modules.load			Compile, package, and install the base module andReference Policy modules configured to be built asloadable modules, then insert them into the modulestore.validate		Validate if the configured modules can successfullylink and expand.install-headers		Install the policy headers into /usr/share/selinux/NAME.The headers are sufficient for building a policymodule locally, without requiring the completeReference Policy sources.  The build.conf settingsfor this policy configuration should be set beforeusing this target.build-interface-db	Build the policy interface database with'sepolgen-ifgen'.  This database is required forreference style policy generation by'audit2allow --reference'.Make targets specific to monolithic policies:policy			Compile a policy locally for development and testing.This is the default target for monolithic policies.install			Compile and install the policy and file contexts.load			Compile and install the policy and file contexts, thenload the policy.enableaudit		Remove all dontaudit rules from policy.conf.relabel			Relabel the filesystem.checklabels		Check the labels on the filesystem, and report whena file would be relabeled, but do not change its label.restorelabels		Relabel the filesystem and report each file that isrelabeled.2) Reference Policy Build Options (build.conf)TYPE			String.  Available options are standard, mls, and mcs.For a type enforcement only system, set standard.This optionally enables multi-level security (MLS) ormulti-category security (MCS) features.  This optioncontrols enable_mls, and enable_mcs policy blocks.NAME			String (optional).  Sets the name of the policy; theNAME is used when installing files to e.g.,/etc/selinux/NAME and /usr/share/selinux/NAME.  If notset, the policy type (TYPE) is used.DISTRO			String (optional).  Enable distribution-specific policy.Available options are redhat, gentoo, and debian.This option controls distro_redhat, distro_gentoo, anddistro_debian build option policy blocks.MONOLITHIC		Boolean.  If set, a monolithic policy is built,otherwise a modular policy is built.DIRECT_INITRC		Boolean.  If set, sysadm will be allowed to directlyrun init scripts, instead of requiring the run_inittool.  This is a build option instead of a tunable sincerole transitions do not work in conditional policy.This option controls direct_sysadm_daemon policyblocks.OUTPUT_POLICY		Integer.  Set the version of the policy created whenbuilding a monolithic policy.  This option has no effecton modular policy.UNK_PERMS		String.  Set the kernel behavior for handling ofpermissions defined in the kernel but missing from thepolicy.  The permissions can either be allowed (allow),denied (deny), or the policy loading can be rejected(reject).UBAC			Boolean.  If set, the SELinux user will be usedadditionally for approximate role separation.SYSTEMD			Boolean.  If set, systemd will be assumed to be the initprocess provider.MLS_SENS		Integer.  Set the number of sensitivities in the MLSpolicy.  Ignored on standard and MCS policies.MLS_CATS		Integer.  Set the number of categories in the MLSpolicy.  Ignored on standard and MCS policies.MCS_CATS		Integer.  Set the number of categories in the MCSpolicy.  Ignored on standard and MLS policies.QUIET			Boolean.  If set, the build system will only displaystatus messages and error messages.  This option has noeffect on policy.WERROR			Boolean.  If set, the build system will treat warningsas errors.  If any warnings are encountered, the buildwill fail.3) Reference Policy Files and Directories
All directories relative to the root of the Reference Policy sources directory.Makefile		General rules for building the policy.Rules.modular		Makefile rules specific to building loadable modulepolicies.Rules.monolithic	Makefile rules specific to building monolithic policies.build.conf		Options which influence the building of the policy,such as the policy type and distribution.config/appconfig-*	Application configuration files for all configurationsof the Reference Policy (targeted/strict with or withoutMLS or MCS).  These are used by SELinux-aware programs.config/local.users	The file read by load policy for adding SELinux usersto the policy on the fly.doc/html/*		This contains the contents of the in-policy XMLdocumentation, presented in web page form.doc/policy.dtd		The doc/policy.xml file is validated against this DTD.doc/policy.xml		This file is generated/updated by the conf and html maketargets.  It contains the complete XML documentationincluded in the policy.doc/templates/*		Templates used for documentation web pages.policy/booleans.conf	This file is generated/updated by the conf make target.It contains the booleans in the policy, and theirdefault values.  If tunables are implemented asbooleans, tunables will also be included.  This filewill be installed as the /etc/selinux/NAME/booleansfile.policy/constraints	This file defines additional constraints on permissionsin the form of boolean expressions that must besatisfied in order for specified permissions to begranted.  These constraints are used to further refinethe type enforcement rules and the role allow rules.Typically, these constraints are used to restrictchanges in user identity or role to certain domains.policy/global_booleans	This file defines all booleans that have a global scope,their default value, and documentation.policy/global_tunables	This file defines all tunables that have a global scope,their default value, and documentation.policy/flask/initial_sids  This file has declarations for each initial SID.policy/flask/security_classes  This file has declarations for each security class.policy/flask/access_vectors  This file defines the access vectors.  Commonprefixes for access vectors may be defined at thebeginning of the file.  After the common prefixes aredefined, an access vector may be defined for eachsecurity class.policy/mcs		The multi-category security (MCS) configuration.policy/mls		The multi-level security (MLS) configuration.policy/modules/*	Each directory represents a layer in Reference Policyall of the modules are contained in one of these layers.policy/modules.conf	This file contains a listing of available modules, andhow they will be used when building Reference Policy. Toprevent a module from  being used, set the module to"off".  For monolithic policies, modules set to "base"and "module" will be included in the policy.  Formodular policies, modules set to "base"	will be includedin the base module; those set to "module" will becompiled as individual loadable	modules.policy/support/*	Support macros.policy/users		This file defines the users included in the policy.support/*		Tools used in the build process.4) Building policy modules using Reference Policy headers:The system must first have the Reference Policy headers installed, typically
by the distribution.  Otherwise, the headers can be installed using the
install-headers target from the full Reference Policy sources.To set up a directory to build a local module, one must simply place a .te
file in a directory.  A sample Makefile to use in the directory is the
Makefile.example in the doc directory.  This may be installed in
/usr/share/doc, under the directory for the distribution's policy.
Alternatively, the primary Makefile in the headers directory (typically
/usr/share/selinux/NAME/Makefile) can be called directly, using make's -f
option.Larger projects can set up a structure of layers, just as in Reference
Policy, by creating policy/modules/LAYERNAME directories.  Each layer also
must have a metadata.xml file which is an XML file with a summary tag and
optional desc (long description) tag.  This should describe the purpose of
the layer.Metadata.xml example:<summary>ABC modules for the XYZ components.</summary>Make targets for modules built from headers:MODULENAME.pp		Compile and package the MODULENAME local module.all			Compile and package the modules in the currentdirectory.load			Compile and package the modules in the currentdirectory, then insert them into the module store.refresh			Attempts to reinsert all modules that are currentlyin the module store from the local and system modulepackages.xml			Build a policy.xml from the XML included with thebase policy headers and any XML in the modules inthe current directory.

上一回讲解了README文件的第一部分，本回继续针对于余下步骤一一进行说明和讲解。

（2）Reference Policy Build Options (build.conf)（参考策略构建选项 build.conf）

本小节内容是对于refpolicy源码根目录下的build.conf文件所进行的详细讲解，该文件内容如下：

########################################
#
# Policy build options
## Policy version
# By default, checkpolicy will create the highest
# version policy it supports.  Setting this will
# override the version.  This only has an
# effect for monolithic policies.
#OUTPUT_POLICY = 33# Policy Type
# standard, mls, mcs
TYPE = standard# Policy Name
# If set, this will be used as the policy
# name.  Otherwise the policy type will be
# used for the name.
NAME = refpolicy# Distribution
# Some distributions have portions of policy
# for programs or configurations specific to the
# distribution.  Setting this will enable options
# for the distribution.
# redhat, gentoo, debian, suse, and rhel4 are current options.
# Fedora users should enable redhat.
#DISTRO = redhat# Unknown Permissions Handling
# The behavior for handling permissions defined in the
# kernel but missing from the policy.  The permissions
# can either be allowed, denied, or the policy loading
# can be rejected.
# allow, deny, and reject are current options.
UNK_PERMS = deny# Direct admin init
# Setting this will allow sysadm to directly
# run init scripts, instead of requiring run_init.
# This is a build option, as role transitions do
# not work in conditional policy.
DIRECT_INITRC = n# Systemd
# Setting this will configure systemd as the init system.
SYSTEMD = n# Build monolithic policy.  Putting y here
# will build a monolithic policy.
MONOLITHIC = n# User-based access control (UBAC)
# Enable UBAC for role separations.
UBAC = y# Custom build options.  This field enables custom
# build options.  Putting foo here will enable
# build option blocks named foo.  Options should be
# separated by spaces.
CUSTOM_BUILDOPT =# Number of MLS Sensitivities
# The sensitivities will be s0 to s(MLS_SENS-1).
# Dominance will be in increasing numerical order
# with s0 being lowest.
MLS_SENS = 16# Number of MLS Categories
# The categories will be c0 to c(MLS_CATS-1).
MLS_CATS = 1024# Number of MCS Categories
# The categories will be c0 to c(MLS_CATS-1).
MCS_CATS = 1024# Set this to y to only display status messages
# during build.
QUIET = n# Set this to treat warnings as errors.
WERROR = n