[CentOS] Type enforcement / mechanism not clear

Sun Sep 9 13:43:31 UTC 2018
Leon Fauster <leonfauster at googlemail.com>

Am 09.09.2018 um 14:49 schrieb Daniel Walsh <dwalsh at redhat.com>:
> On 09/08/2018 09:50 PM, Leon Fauster via CentOS wrote:
>> Any SElinux expert here - briefly:
>> # getenforce
>> Enforcing
>> # sesearch -ACR -s httpd_t  -c file -p read |grep system_conf_t
>> <no output>
>> # sesearch -ACR -s httpd_t  -c file -p read |grep syslog_conf_t
>> <no output>
>> # ls -laZ /etc/sysctl.conf /etc/rsyslog.conf
>> -rw-r--r--. root root system_u:object_r:syslog_conf_t:s0 /etc/rsyslog.conf
>> -rw-r--r--. root root system_u:object_r:system_conf_t:s0 /etc/sysctl.conf
>> # ausearch -m avc --start recent
>> type=SYSCALL msg=audit(1536457230.922:85): arch=c000003e syscall=6 success=no exit=-13 a0=7fff6460dcf0 a1=7fff6460dbe0 a2=7fff6460dbe0 a3=11 items=0 ppid=1362 pid=1364 auid=4294967295 uid=48 gid=48 euid=48 suid=48 fsuid=48 egid=48 sgid=48 fsgid=48 tty=(none) ses=4294967295 comm="php-fpm" exe="/usr/sbin/php-fpm" subj=system_u:system_r:httpd_t:s0 key=(null)
>> type=AVC msg=audit(1536457230.922:85): avc:  denied  { getattr } for  pid=1364 comm="php-fpm" path="/etc/rsyslog.conf" dev=dm-0 ino=138287 scontext=system_u:system_r:httpd_t:s0 tcontext=system_u:object_r:syslog_conf_t:s0 tclass=file
>> My test PHP script can read /etc/sysctl.conf but not /etc/rsyslog.conf. For both
>> no rule are found (sesearch above). So, why the script can read sysctl.conf?
> Because almost no apache servers would normally be walking through /etc reading
> configuration files.  Do you scripts actually need to read these config files?

Normally, sure - but a malicious developer (or attacker) will do. So, I'm evaluating different 
approaches to secure our platform. Its possible to limit fs access in PHP but this comes with
a massive performance penalty.

Well, I do not want to discuss that all "etc_t" files can be read but why 
sysctl.conf with "system_conf_t" type can be read where it shouldn't??

Any pointer would be greatly appreciated.