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From:   Richard Haines <richard_c_haines@btinternet.com>
To:     selinux-refpolicy@vger.kernel.org
Cc:     Richard Haines <richard_c_haines@btinternet.com>
Subject: [PATCH V2] Ensure correct monolithic binary policy is loaded
Date:   Fri, 18 Dec 2020 15:03:07 +0000
Message-Id: <20201218150307.8826-1-richard_c_haines@btinternet.com>
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When building a monolithic policy with 'make load', the
selinux_config(5) file 'SELINUXTYPE' entry determines what policy
is loaded as load_policy(8) does not take a path value (it always loads
the active system policy as defined by /etc/selinux/config).

Currently it is possible to load the wrong binary policy, for example if
the Reference Policy source is located at:
/etc/selinux/refpolicy
and the /etc/selinux/config file has the following entry:
SELINUXTYPE=targeted
Then the /etc/selinux/targeted/policy/policy.<ver> is loaded when
'make load' is executed.

Another example is that if the Reference Policy source is located at:
/tmp/custom-rootfs/etc/selinux/refpolicy
and the /etc/selinux/config file has the following entry:
SELINUXTYPE=refpolicy
Then the /etc/selinux/refpolicy/policy/policy.<ver> is loaded when
'make DESTDIR=/tmp/custom-rootfs load' is executed (not the
/tmp/custom-rootfs/etc/selinux/refpolicy/policy/policy.<ver> that the
developer thought would be loaded).

Resolve these issues by using selinux_path(3) to resolve the policy root,
then checking the selinux_config(5) file for the appropriate SELINUXTYPE
entry.

Remove the '@touch $(tmpdir)/load' line as the file is never referenced.

Signed-off-by: Richard Haines <richard_c_haines@btinternet.com>
---
V2 Changes: Use $(error .. instead of NO_LOAD logic. Use python script to
find selinux path not sestatus. Reword error messages.

 Makefile                |  1 +
 Rules.monolithic        | 15 ++++++++++++++-
 support/selinux_path.py | 13 +++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 support/selinux_path.py

diff --git a/Makefile b/Makefile
index 6ba215f1..e49d43d0 100644
--- a/Makefile
+++ b/Makefile
@@ -97,6 +97,7 @@ genxml := $(PYTHON) $(support)/segenxml.py
 gendoc := $(PYTHON) $(support)/sedoctool.py
 genperm := $(PYTHON) $(support)/genclassperms.py
 policyvers := $(PYTHON) $(support)/policyvers.py
+selinux_path := $(PYTHON) $(support)/selinux_path.py
 fcsort := $(PYTHON) $(support)/fc_sort.py
 setbools := $(AWK) -f $(support)/set_bools_tuns.awk
 get_type_attr_decl := $(SED) -r -f $(support)/get_type_attr_decl.sed
diff --git a/Rules.monolithic b/Rules.monolithic
index a8ae98d1..cd065362 100644
--- a/Rules.monolithic
+++ b/Rules.monolithic
@@ -42,6 +42,12 @@ vpath %.te $(all_layers)
 vpath %.if $(all_layers)
 vpath %.fc $(all_layers)
 
+# load_policy(8) loads policy from <SELINUX_PATH>/<SELINUXTYPE>/policy/policy.<ver>
+# It does this by reading the <SELINUX_PATH>/config file and using the
+# SELINUX_PATH/SELINUXTYPE entries to form the initial path.
+SELINUX_PATH := $(shell $(selinux_path))
+SELINUXTYPE := $(strip $(shell $(AWK) -F= '/^SELINUXTYPE/{ print $$2 }' $(SELINUX_PATH)/config))
+
 ########################################
 #
 # default action: build policy locally
@@ -91,9 +97,16 @@ endif
 # Load the binary policy
 #
 reload $(tmpdir)/load: $(loadpath) $(fcpath) $(appfiles)
+ifneq ($(SELINUXTYPE),$(NAME))
+	$(error Cannot load policy as $(SELINUX_PATH)/config file contains SELINUXTYPE=$(SELINUXTYPE) - \
+		Edit $(SELINUX_PATH)/config and set "SELINUXTYPE=$(NAME)")
+endif
+ifneq ($(topdir),$(SELINUX_PATH))
+	$(error Cannot load policy as policy root MUST be $(SELINUX_PATH)/$(NAME) - \
+		Current policy root is: $(topdir)/$(NAME))
+endif
 	@echo "Loading $(NAME) $(loadpath)"
 	$(verbose) $(LOADPOLICY) -q $(loadpath)
-	@touch $(tmpdir)/load
 
 ########################################
 #
diff --git a/support/selinux_path.py b/support/selinux_path.py
new file mode 100644
index 00000000..b663ff09
--- /dev/null
+++ b/support/selinux_path.py
@@ -0,0 +1,13 @@
+#!/usr/bin/env python3
+
+try:
+    import warnings
+    with warnings.catch_warnings():
+        warnings.filterwarnings("ignore", category=PendingDeprecationWarning)
+        import selinux
+
+    if selinux.is_selinux_enabled():
+        # Strip the trailing '/'
+        print(selinux.selinux_path()[:-1])
+except ImportError:
+    exit(0)
-- 
2.29.2