Re: strange tclass in AVCs

[Stephen Smalley <sds@tycho.nsa.gov>]

On 9/18/19 10:03 AM, Ted Toth wrote:
> On Wed, Sep 18, 2019 at 8:53 AM Stephen Smalley <sds@tycho.nsa.gov> wrote:
>>
>> On 9/18/19 9:35 AM, Ted Toth wrote:
>>> I'm seeing things like tclass=context#012 in some AVCs what is this telling me?
>>
>> Just a guess here, but octal 012 is '\n' aka a newline character, and
>> libselinux/src/avc.c:avc_audit() appends a "\n" at the end of the buffer
>> before calling avc_log() to log the entire string.  avc_log() will call
>> the logging callback, and dbusd does define one, which calls
>> audit_log_user_avc_message().  Maybe audit_log_user_avc_message() is
>> escaping the newline character in its output as well as appending
>> additional data.
>>
>> I'm a little unclear though on why dbusd is checking a context contains
>> permission?
> 
> These appear to only occur when systemd is starting the dbus daemon
> and they end up in /var/log/messages not /var/log/audit/audit.log as
> I'd expect.

Sounds like auditd isn't operational at that point and therefore the 
output just goes to syslog.

Arguably avc_audit() shouldn't be adding a newline at all and that 
should be handled by the logging callback (or default_selinux_log if no 
callback is set).  But it has been this way forever, so that would no 
doubt break some users.  Legacy of when this was a printk/printf.