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<p class="MsoNormal"><span style="color:#1F497D">If anyone else has a similar issue, the problem is with SELinux’s built in policies. Here is the Type Enforcement module I had to build and install. Just let me know if any questions:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">module pdns_customized 1.0;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">require {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> type proc_t;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> type usr_t;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> type pdns_t;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> type unreserved_port_t;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> class udp_socket name_bind;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> class file { map read };<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">#============= pdns_t ==============<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">allow pdns_t proc_t:file read;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">allow pdns_t unreserved_port_t:udp_socket name_bind;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">allow pdns_t usr_t:file map;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Sean<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> Pdns-users <pdns-users-bounces@mailman.powerdns.com>
<b>On Behalf Of </b>Sean Lair via Pdns-users<br>
<b>Sent:</b> Saturday, June 6, 2020 3:14 PM<br>
<b>To:</b> pdns-users@mailman.powerdns.com<br>
<b>Subject:</b> [Pdns-users] Error binding on UDP port 53 only when slave=yes<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">Please double check the sender's email address. The sender may not be who they claim to be. -----------------------------------------------------------------------
<o:p></o:p></span></p>
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<p class="MsoNormal">Hello!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Our Authorities PDNS servers are currently using native mode with MariaDB. We are attempting to enabled slave=yes (in pdns.conf) but when we do so, we get the error below. ***If we do not have slave=yes configured, then PDNS works fine
(but not in slave mode of course).***<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-----------------------------<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 systemd[1]: Starting PowerDNS Authoritative Server...<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: Loading '/usr/lib64/pdns/libgmysqlbackend.so'<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: This is a standalone pdns<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: Listening on controlsocket in '/var/run/pdns/pdns.controlsocket'<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: UDP server bound to 0.0.0.0:53<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: UDP server bound to [::]:53<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: TCP server bound to 0.0.0.0:53<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: TCP server bound to [::]:53<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: PowerDNS Authoritative Server 4.3.0 (C) 2001-2020 PowerDNS.COM BV<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: Using 64-bits mode. Built using gcc 8.3.1 20190507 (Red Hat 8.3.1-4) on Apr 9 2020 19:45:37 by mockbuild@localhost.<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: PowerDNS comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it according to the terms of the GPL version 2.<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: [webserver] Listening for HTTP requests on 0.0.0.0:8081<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: Master/slave communicator launching<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: Creating backend connection for TCP<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: About to create 3 backend threads for UDP<o:p></o:p></p>
<p class="MsoNormal">Jun 6 19:57:54 ns1 pdns_server[8154]: Exiting because communicator thread died with error: Resolver binding to local UDP socket on 0.0.0.0: Permission denied<o:p></o:p></p>
<p class="MsoNormal">-----------------------------<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It seems that when slave=yes is configured that PDNS drops its privilege level before opening it’s sockets? If I turn off SELinux we have no issues, but with SELinux ON w/o slave=yes we also work without issue… Here is a line from our
audit log, confirming that SELinux is blocking listening on port 53 – again this blocking only occurs if slave=yes.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-----------------------------<o:p></o:p></p>
<p class="MsoNormal">type=AVC msg=audit(1591472511.372:4842): avc: denied { name_bind } for pid=8081 comm="pdns/comm-main" src=14783 scontext=system_u:system_r:pdns_t:s0 tcontext=system_u:object_r:unreserved_port_t:s0 tclass=udp_socket permissive=0<o:p></o:p></p>
<p class="MsoNormal">-----------------------------<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Let me know if there is anything else I can provide to help. We are CentOS8 and PowerDNS Authoritative Server 4.3.0.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks!<o:p></o:p></p>
<p class="MsoNormal">Sean<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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