Binding a server to privileged port on Linux w/o running as root

This is applicable to any service using privileged ports (< 1024), for instance to run a HTTP server on port 80 or a LDAP directory server on port 389.

  • Running the server as root is not a recommended option for security reasons.
  • Using iptables to map privileged port (e.g. 389) to non-privileged port is a well-know method.
  • Updating the Linux config to put 389 on the non-privileged port list is another option.

There is another option that I use frequently, based on setcap to run OUD on port 389 in my labs:

This solution requires install and modification of a java 7 JVM specifically for OUD use.

Such configuration has security implications, as anyone running that JVM has the right to bind on privileged ports (settings are JVM wide, not restricted to a specific jar file/application), so the jvm access should be restricted to the appropriate user only (the one allowed to start OUD)

Here is the procedure:

  1. download patchelf sources from here and compile them on target Linux.
  2. install setcap package on Linux if needed
  3. install a java 7 SDK on target system e.g. /space/java/jdk1.7.0_45
  4. restrict access to that jvm (java and jre) to the appropriate user only (the one used to start OUD).
    Put in place additional security if needed.
  5. as root, run the following commands to allow java to bind as priviledged ports

    setcap cap_net_bind_service=+epi <JAVA_HOME>/bin/java
    setcap cap_net_bind_service=+epi <JAVA_HOME>/jre/bin/java


  6. - change java dynamic library loading strategy as default strategy is not compatible with setcap

    patchelf --set-rpath <JAVA_HOME>/jre/lib/amd64/jli <JAVA_HOME>/jre/bin/java
    patchelf --set-rpath <JAVA_HOME>/lib/amd64/jli <JAVA_HOME>/bin/java


  7. - Modify jvm used by oud

    edit java.properties and modify property e.g default.java-home
    run dsjavaproperties

  8. - start OUD with standard start-ds command.


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About


I am Sylvain Duloutre, I work as a Software Architect in the Oracle Directory Integration Team, the customer-facing part of Directory Services & Identity Management Product Development, working on Technical Field Enablement.

The views expressed on this blog are my own and do not necessarily reflect the views of Oracle.

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