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Subject: Re: [PATCH V3] Ensure correct monolithic binary policy is loaded
To:     Richard Haines <richard_c_haines@btinternet.com>,
        selinux-refpolicy@vger.kernel.org
References: <20201221122213.11643-1-richard_c_haines@btinternet.com>
From:   Chris PeBenito <pebenito@ieee.org>
Message-ID: <3d7cae1e-943f-d857-b9b3-89c1d773362e@ieee.org>
Date:   Wed, 13 Jan 2021 09:56:51 -0500
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On 12/21/20 7:22 AM, Richard Haines wrote:
> 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.
> Resolve this by using selinux_binary_policy_path(3) to determine the
> current configured policy name and its location.
> 
> 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 this by checking if DESTDIR has been set.
> 
> 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.
> V3 Change: Use the selinux_binary_policy_path() python script and reword
> error messages.
> 
>   Makefile                              |  1 +
>   Rules.monolithic                      | 15 ++++++++++++++-
>   support/selinux_binary_policy_path.py | 12 ++++++++++++
>   3 files changed, 27 insertions(+), 1 deletion(-)
>   create mode 100644 support/selinux_binary_policy_path.py
> 
> diff --git a/Makefile b/Makefile
> index 6ba215f1..1b0a4826 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
> +binary_policy_path := $(PYTHON) $(support)/selinux_binary_policy_path.py
>   fcsort := $(PYTHON) $(support)/fc_sort.py
>   setbools := $(AWK) -f $(support)/set_bools_tuns.awk
>   get_type_attr_decl := $(SED) -r -f $(support)/get_type_attr_decl.sed
> diff --git a/Rules.monolithic b/Rules.monolithic
> index a8ae98d1..7dbc2e1c 100644
> --- a/Rules.monolithic
> +++ b/Rules.monolithic
> @@ -13,6 +13,12 @@ ifeq "$(kv)" ""
>   	kv := $(pv)
>   endif
>   
> +# load_policy(8) loads policy from /etc/selinux/<SELINUXTYPE>/policy/policy.$(pv)
> +# It does this by reading the /etc/selinux/config file SELINUXTYPE entry to
> +# form the full path. $(polbinpath) will contain this evaluated path for use as
> +# a validation check.
> +polbinpath := $(shell $(binary_policy_path))
> +
>   policy_conf = $(builddir)policy.conf
>   fc = $(builddir)file_contexts
>   polver = $(builddir)policy.$(pv)
> @@ -91,9 +97,16 @@ endif
>   # Load the binary policy
>   #
>   reload $(tmpdir)/load: $(loadpath) $(fcpath) $(appfiles)
> +ifneq ($(DESTDIR),)
> +	$(error Cannot load policy as '$$DESTDIR' is set to $(DESTDIR), \
> +		creating an invalid policy load path)
> +endif
> +ifneq ($(polbinpath).$(pv),$(loadpath))
> +	$(error Cannot load policy as invalid policy path: $(polbinpath).$(pv) - \
> +		Check $(topdir)/config file entry is: "SELINUXTYPE=$(NAME)")
> +endif
>   	@echo "Loading $(NAME) $(loadpath)"
>   	$(verbose) $(LOADPOLICY) -q $(loadpath)
> -	@touch $(tmpdir)/load
>   
>   ########################################
>   #
> diff --git a/support/selinux_binary_policy_path.py b/support/selinux_binary_policy_path.py
> new file mode 100644
> index 00000000..a30eb9b6
> --- /dev/null
> +++ b/support/selinux_binary_policy_path.py
> @@ -0,0 +1,12 @@
> +#!/usr/bin/env python3
> +
> +try:
> +    import warnings
> +    with warnings.catch_warnings():
> +        warnings.filterwarnings("ignore", category=PendingDeprecationWarning)
> +        import selinux
> +
> +    if selinux.is_selinux_enabled():
> +        print(selinux.selinux_binary_policy_path())
> +except ImportError:
> +    exit(0)

Merged, sorry for the slow response.

-- 
Chris PeBenito