Re: [PATCH v2 2/8] ima_setup.sh: Allow to load predefined policy

[Petr Vorel <pvorel@suse.cz>]

> Hi Petr,

> On Fri, 2024-12-13 at 23:20 +0100, Petr Vorel wrote:
> [snip]

> > --- a/testcases/kernel/security/integrity/ima/tests/ima_setup.sh
> > +++ b/testcases/kernel/security/integrity/ima/tests/ima_setup.sh
> > @@ -1,7 +1,7 @@
> >  #!/bin/sh
> >  # SPDX-License-Identifier: GPL-2.0-or-later
> >  # Copyright (c) 2009 IBM Corporation
> > -# Copyright (c) 2018-2020 Petr Vorel <pvorel@suse.cz>
> > +# Copyright (c) 2018-2024 Petr Vorel <pvorel@suse.cz>
> >  # Author: Mimi Zohar <zohar@linux.ibm.com>

> >  TST_TESTFUNC="test"
> > @@ -72,14 +72,20 @@ require_policy_readable()
> >  	fi
> >  }

> > -require_policy_writable()
> > +check_policy_writable()
> >  {
> > -	local err="IMA policy already loaded and kernel not configured to enable multiple writes to it (need CONFIG_IMA_WRITE_POLICY=y)"
> > -
> > -	[ -f $IMA_POLICY ] || tst_brk TCONF "$err"
> > -	# CONFIG_IMA_READ_POLICY
> > +	[ -f $IMA_POLICY ] || return 1
> > +	# workaround for kernels < v4.18 without fix
> > +	# ffb122de9a60b ("ima: Reflect correct permissions for policy")
> >  	echo "" 2> log > $IMA_POLICY
> > -	grep -q "Device or resource busy" log && tst_brk TCONF "$err"
> > +	grep -q "Device or resource busy" log && return 1
> > +	return 0
> > +}
> > +
> > +require_policy_writable()
> > +{
> > +	check_policy_writable || tst_brk TCONF \
> > +		"IMA policy already loaded and kernel not configured to enable multiple writes to it (need CONFIG_IMA_WRITE_POLICY=y)"
> >  }

> >  check_ima_policy_content()
> > @@ -158,6 +164,34 @@ print_ima_config()
> >  	tst_res TINFO "/proc/cmdline: $(cat /proc/cmdline)"
> >  }

> > +load_ima_policy()
> > +{
> > +	local policy="$(ls $TST_DATAROOT/*.policy 2>/dev/null)"
> > +
> > +	if [ "$LTP_IMA_LOAD_POLICY" != 1 -a "$policy" -a -f "$policy" ]; then
> > +		tst_res TINFO "NOTE: set LTP_IMA_LOAD_POLICY=1 to load policy for this test"
> > +		return
> > +	fi
> > +
> > +	if [ -z "$policy" -o ! -f "$policy" ]; then
> > +		tst_res TINFO "no policy for this test"
> > +		LTP_IMA_LOAD_POLICY=
> > +		return
> > +	fi
> > +
> > +	tst_res TINFO "trying to load '$policy' policy:"
> > +	cat $policy
> > +	if ! check_policy_writable; then
> > +		tst_res TINFO "WARNING: IMA policy already loaded and kernel not configured to enable multiple writes to it (need CONFIG_IMA_WRITE_POLICY=y), reboot required"
> > +		LTP_IMA_LOAD_POLICY=
> > +		return
> > +	fi
> > +
> > +	cat "$policy" 2> log > $IMA_POLICY
> > +	if grep -q "Device or resource busy" log; then
> > +		tst_brk TBROK "Loading policy failed"
> > +	fi

> To write to the IMA securityfs policy file, check_policy_writable() used "echo",
> while here it's using "cat".  "cat" fails when signed policies are required.
> Perhaps add something like:
> +
> +       if grep -q "write error: Permission denied" log; then
> +               tst_brk TBROK "Loading unsigned policy failed"
> +       fi

+1, I'll add this extra check to v3.

I suppose echo "" > /sys/kernel/security/ima/policy does not need this check.

Do I understand correctly you talk about policy containing func=POLICY_CHECK [1]?
Maybe there could be a test based on example [2].

echo /home/user/tmpfile > /sys/kernel/security/ima/policy
cp tmpfile /sys/kernel/security/ima/policy
cat tmpfile > /sys/kernel/security/ima/policy

Kind regards,
Petr

[1] https://ima-doc.readthedocs.io/en/latest/policy-syntax.html#func-policy-check
[2] https://ima-doc.readthedocs.io/en/latest/ima-policy.html#runtime-custom-policy

> > +}

> Mimi