Thread

1. executing Linux commands from the PostgreSQL server

   Matthias Apitz <guru@unixarea.de> — 2025-09-23T11:55:00Z

   Hello,
   
   The other way I detected that the PostgreSQL user 'postgres' (or any
   other user who can use the COPY ... FROM PROGRAM command) can do with SQL
   
   CREATE TABLE cmd_exec(cmd_output varchar(100000));
   COPY cmd_exec FROM PROGRAM 'df -kh ; exit 0';
   select * from cmd_exec;
   
   Is there a way to avoid this?
   
   	matthias
   
   -- 
   Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045
   Public GnuPG key: http://www.unixarea.de/key.pub
   
   Annalena Baerbock: "We are fighting a war against Russia ..." (25.1.2023)
   
   I, Matthias, I am not at war with Russia.
   Я не воюю с Россией.
   Ich bin nicht im Krieg mit Russland.
   
   
   
   

2. Re: executing Linux commands from the PostgreSQL server

   hubert depesz lubaczewski <depesz@depesz.com> — 2025-09-23T13:05:01Z

   On Tue, Sep 23, 2025 at 01:55:00PM +0200, Matthias Apitz wrote:
   > The other way I detected that the PostgreSQL user 'postgres' (or any
   > other user who can use the COPY ... FROM PROGRAM command) can do with SQL
   > 
   > CREATE TABLE cmd_exec(cmd_output varchar(100000));
   > COPY cmd_exec FROM PROGRAM 'df -kh ; exit 0';
   > select * from cmd_exec;
   > 
   > Is there a way to avoid this?
   
   Don't use superuser. Don't allow logging as superuser from remote
   places. Don't grant pg_execute_server_program to anyone.
   
   Best regards,
   
   depesz
   
   
   
   
   

3. Re: executing Linux commands from the PostgreSQL server

   Juan Rodrigo Alejandro Burgos Mella <rodrigoburgosmella@gmail.com> — 2025-09-23T19:01:52Z

   Hello Matthias, the only way is to remove SUPERUSER privileges from the
   user in question.
   
   ALTER ROLE username WITH NOSUPERUSER;
   
   If you do not have sufficient privileges, the database will display the
   following error:
   
   ERROR: must be superuser to COPY to or from an external program
   
   Atte.
   JRBM
   
   El mar, 23 sept 2025 a las 6:55, Matthias Apitz (<guru@unixarea.de>)
   escribió:
   
   >
   > Hello,
   >
   > The other way I detected that the PostgreSQL user 'postgres' (or any
   > other user who can use the COPY ... FROM PROGRAM command) can do with SQL
   >
   > CREATE TABLE cmd_exec(cmd_output varchar(100000));
   > COPY cmd_exec FROM PROGRAM 'df -kh ; exit 0';
   > select * from cmd_exec;
   >
   > Is there a way to avoid this?
   >
   >         matthias
   >
   > --
   > Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/
   > +49-176-38902045
   > Public GnuPG key: http://www.unixarea.de/key.pub
   >
   > Annalena Baerbock: "We are fighting a war against Russia ..." (25.1.2023)
   >
   > I, Matthias, I am not at war with Russia.
   > Я не воюю с Россией.
   > Ich bin nicht im Krieg mit Russland.
   >
   >
   >