Security considerations with DDM

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DDM uses the QUSER profile by default, when another machine accesses files. This might pose a possible security issue, because data can be read and written by an anonymous user.

On the AS/400 DDM can be used by creating a DDM file with the CRTDDMF command, and using the RMTFILE parameter fields to point to a valid file on the remote server.

The RMTLOCNAME parameter can either point to a SNA/APPN node, or to an IP host name.

  • APPN/APPC is enabled by default on OS/400. As soon as an APPN adjacency has been configured between any two machines, DDM can be used. It's an APPC service which is started on demand by a requesting APPC client. Given the usually limited reach of SNA networks today, and the necessity of former APPN configuration steps, the chance of a really anonymous attacker abusing this capability is low.
  • If you don't need DDM functionality over TCP/IP transport, simply ENDTCPSVR SERVER(*DDM), and make sure you disable autostart (CHGDDMTCPA AUTOSTART(*NO)).
  • If you need DDM functionality over TCP/IP transport, make sure you set PWDRQD at least to *YES, better to *ENCRYPTED.

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