Re: [PATCH v2] setsebool: support use of -P on SELinux-disabled hosts

[Petr Lautrbach <plautrba@redhat.com>]

Stephen Smalley <sds@tycho.nsa.gov> writes:

> On 1/14/19 6:31 AM, Petr Lautrbach wrote:
>> Stephen Smalley <sds@tycho.nsa.gov> writes:
>>
>>> As reported in #123, setsebool immediately exits with an error if
>>> SELinux is disabled, preventing its use for setting boolean persistent
>>> values.  In contrast, semanage boolean -m works on SELinux-disabled
>>> hosts.  Change setsebool so that it can be used with the -P option
>>> (persistent changes) even if SELinux is disabled.  In the SELinux-disabled
>>> case, skip setting of active boolean values, but set the persistent value
>>> in the policy store.  Policy reload is automatically disabled by libsemanage
>>> when SELinux is disabled, so we only need to call semanage_set_reload()
>>> if -N was used.
>>>
>>
>> So right now, `setsebool -N` and `semanage boolean -N` have the same effect that
>> `load_policy` is not run, but the value of the boolean is changed when
>> SELinux is enabled so it affects the system. Would it make sense to use
>> -N to just change values in the store and do not change the value in the
>> running kernel? E.g.
>>
>> --- a/policycoreutils/setsebool/setsebool.c
>> +++ b/policycoreutils/setsebool/setsebool.c
>> @@ -187,11 +187,14 @@ static int semanage_set_boolean_list(size_t boolcnt,
>>                                                    boolean) < 0)
>>                          goto err;
>>   -               if (enabled && semanage_bool_set_active(handle, bool_key,
>> boolean) < 0) {
>> -                       fprintf(stderr, "Failed to change boolean %s: %m\n",
>> -                               boollist[j].name);
>> -                       goto err;
>> -               }
>> +               if (no_reload)
>> +                       semanage_set_reload(handle, 0);
>> +               else
>> +                       if (enabled && semanage_bool_set_active(handle, bool_key, boolean) < 0) {
>> +                               fprintf(stderr, "Failed to change boolean %s: %m\n",
>> +                                                               boollist[j].name);
>> +                               goto err;
>> +                       }
>>
>>
>> A similar patch would need to be applied to seobject.py as well in this case.
>
> That makes sense to me logically (in fact, I don't really understand why
> setsebool w/o -P would ever trigger a reload), but I guess the concern is
> whether any existing users rely on the current behavior, e.g. the %post
> scriptlet in container-selinux that led to this issue.

container-selinux.spec:
==========================================================================
# Install all modules in a single transaction
if [ $1 -eq 1 ]; then
    %{_sbindir}/setsebool -P -N virt_use_nfs=1 virt_sandbox_use_all_caps=1
fi
...
if %{_sbindir}/selinuxenabled ; then
    %{_sbindir}/load_policy
    %relabel_files
    if [ $1 -eq 1 ]; then
	restorecon -R %{_sharedstatedir}/docker &> /dev/null || :
	restorecon -R %{_sharedstatedir}/containers &> /dev/null || :
    fi
fi
==========================================================================

It would definitely break this scriptlet on SELinux enabled systems as
load_policy preserves booleans.

So the question is if it's preferred current behavior with it's side
effects or if it's worth to try to fix it and properly announce the
change in release notes.

I take that it's not nice to change/break things but to me it
looks like -N generally considered as option which is used to avoid
changes in the running kernel. 




>
>>
>>
>>
>>> Fixes: https://github.com/SELinuxProject/selinux/issues/123
>>> Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
>>> ---
>>> v2 changes setsebool to only call semanage_set_reload() if -N was specified;
>>> otherwise we can use the libsemanage defaults just as we do in semodule
>>> and semanage.
>>>   policycoreutils/setsebool/setsebool.c | 15 ++++++---------
>>>   1 file changed, 6 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/policycoreutils/setsebool/setsebool.c b/policycoreutils/setsebool/setsebool.c
>>> index 53d3566c..a5157efc 100644
>>> --- a/policycoreutils/setsebool/setsebool.c
>>> +++ b/policycoreutils/setsebool/setsebool.c
>>> @@ -18,7 +18,7 @@
>>>   #include <errno.h>
>>>     int permanent = 0;
>>> -int reload = 1;
>>> +int no_reload = 0;
>>>   int verbose = 0;
>>>     int setbool(char **list, size_t start, size_t end);
>>> @@ -38,11 +38,6 @@ int main(int argc, char **argv)
>>>   	if (argc < 2)
>>>   		usage();
>>>   -	if (is_selinux_enabled() <= 0) {
>>> -		fputs("setsebool:  SELinux is disabled.\n", stderr);
>>> -		return 1;
>>> -	}
>>> -
>>>   	while (1) {
>>>   		clflag = getopt(argc, argv, "PNV");
>>>   		if (clflag == -1)
>>> @@ -53,7 +48,7 @@ int main(int argc, char **argv)
>>>   			permanent = 1;
>>>   			break;
>>>   		case 'N':
>>> -			reload = 0;
>>> +			no_reload = 1;
>>>   			break;
>>>   		case 'V':
>>>   			verbose = 1;
>>> @@ -130,6 +125,7 @@ static int semanage_set_boolean_list(size_t boolcnt,
>>>   	semanage_bool_key_t *bool_key = NULL;
>>>   	int managed;
>>>   	int result;
>>> +	int enabled = is_selinux_enabled();
>>>     	handle = semanage_handle_create();
>>>   	if (handle == NULL) {
>>> @@ -191,7 +187,7 @@ static int semanage_set_boolean_list(size_t boolcnt,
>>>   						  boolean) < 0)
>>>   			goto err;
>>>   -		if (semanage_bool_set_active(handle, bool_key, boolean) < 0) {
>>> +		if (enabled && semanage_bool_set_active(handle, bool_key, boolean) < 0) {
>>>   			fprintf(stderr, "Failed to change boolean %s: %m\n",
>>>   				boollist[j].name);
>>>   			goto err;
>>> @@ -202,7 +198,8 @@ static int semanage_set_boolean_list(size_t boolcnt,
>>>   		boolean = NULL;
>>>   	}
>>>   -	semanage_set_reload(handle, reload);
>>> +	if (no_reload)
>>> +		semanage_set_reload(handle, 0);
>>>   	if (semanage_commit(handle) < 0)
>>>   		goto err;