Re: [PATCH] libselinux: Add security_reject_unknown(3) man page

[Petr Lautrbach <plautrba@redhat.com>]

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

> On 3/4/19 11:37 AM, Petr Lautrbach wrote:
>> Commit c19395d7 added a new interface security_reject_unknown() 
>> which needs to
>> be documented.
>>
>> Signed-off-by: Petr Lautrbach <plautrba@redhat.com>
>> ---
>>   libselinux/man/man3/security_getenforce.3     | 9 ++++++++-
>>   libselinux/man/man3/security_reject_unknown.3 | 1 +
>>   2 files changed, 9 insertions(+), 1 deletion(-)
>>   create mode 100644 
>>   libselinux/man/man3/security_reject_unknown.3
>>
>> diff --git a/libselinux/man/man3/security_getenforce.3 
>> b/libselinux/man/man3/security_getenforce.3
>> index 29cf3de7..8d72afb6 100644
>> --- a/libselinux/man/man3/security_getenforce.3
>> +++ b/libselinux/man/man3/security_getenforce.3
>> @@ -1,6 +1,7 @@
>>   .TH "security_getenforce" "3" "1 January 2004" 
>>   "russell@coker.com.au" "SELinux API documentation"
>>   .SH "NAME"
>> -security_getenforce, security_setenforce, 
>> security_deny_unknown, security_get_checkreqprot\- get or set 
>> the enforcing state of SELinux
>> +security_getenforce, security_setenforce, 
>> security_deny_unknown, security_reject_unknown,
>> +security_get_checkreqprot\- get or set the enforcing state of 
>> SELinux
>>   .
>>   .SH "SYNOPSIS"
>>   .B #include <selinux/selinux.h>
>> @@ -11,6 +12,8 @@ security_getenforce, security_setenforce, 
>> security_deny_unknown, security_get_ch
>>   .sp
>>   .B int security_deny_unknown(void);
>>   .sp
>> +.B int security_reject_unknown(void);
>> +.sp
>>   .B int security_get_checkreqprot(void);
>>   .
>>   .SH "DESCRIPTION"
>> @@ -27,6 +30,10 @@ returned.
>>   returns 0 if SELinux treats policy queries on undefined 
>>   object classes or
>>   permissions as being allowed, 1 if such queries are denied, 
>>   and \-1 on error.
>>   +.BR security_reject_unknown ()
>> +returns 0 if SELinux allows to load a policy which doesn't 
>> define all object
>> +classes and permissions, 1 if loading such policy is rejected, 
>> and \-1 on error.
>
> s/all object classes and permissions/all kernel object classes 
> and permissions/
>
> A policy can still be loaded if it is missing userspace object 
> classes and
> permissions regardless of security_reject_unknown(), although 
> the object manager
> may later encounter a failure upon selinux_set_mapping(), which 
> internally calls
> security_reject_unknown() to decide how to proceed, or direct 
> attempts to lookup
> the class or permission via string_to_security_class() or 
> string_to_av_perm().

I'll update the text.

> I don't know of anyone building policies with handle_unknown == 
> reject so it is
> unlikely that anyone is testing this case.  deny is the default. 
> allow is set
> in Fedora/RHEL.  Android uses deny.

We're considering to use handle_unknown = reject for nightly 
builds
to detect whether there's a new kernel class or permission defined 
in
kernel which is not covered by policy.



>> +
>>   .BR security_get_checkreqprot ()
>>   can be used to determine whether SELinux is configured to 
>>   check the
>>   protection requested by the application or the actual 
>>   protection that will
>> diff --git a/libselinux/man/man3/security_reject_unknown.3 
>> b/libselinux/man/man3/security_reject_unknown.3
>> new file mode 100644
>> index 00000000..d59e5c2c
>> --- /dev/null
>> +++ b/libselinux/man/man3/security_reject_unknown.3
>> @@ -0,0 +1 @@
>> +.so man3/security_getenforce.3
>>