Re: pg_hba.conf editing question

On 20/07/14 02:45 PM, Guillaume Lelarge wrote:
> 2014-07-19 18:11 GMT+02:00 Scott Furry <scott(dot)wl(dot)furry(at)gmail(dot)com
> <mailto:scott(dot)wl(dot)furry(at)gmail(dot)com>>:
>
> I am working with the pgAdmin git source and I am having trouble
> understanding the adminpack functions being used.
>
> In the file pgadmin/frm/frmHbaConfig.cpp, the pg_hba.conf edit
> form constructor appears to get the absolute path to the
> configuration file and stores this value in "serverFileName"
> ("SHOW hba_file"). The value is then used to few lines down in a
> call to "SELECT pg_file_read(...)".
>
> Net Search suggests that pg_file_read can be used to access files
> in the pg data/log directories only. Experimenting on my
> localhost, any attempt to use a "../" or and absolute path results
> in an error.
>
> What I'm having a problem understanding is how the pg_file_read
> function can work in this context. I can access files in the data
> directory nicely, but emulating the queries being used in the
> pgAdmin code will not work. What magic was built into the code to
> get around the absolute path security?
>
>
> No magic. pg_file_read() calls pg_read_file. Here is the main comment
> of this function:
>
> /*¬
> * Convert a "text" filename argument to C string, and check it's
> allowable.¬
> *¬
> * Filename may be absolute or relative to the DataDir, but we only allow¬
> * absolute paths that match DataDir or Log_directory.¬
> */¬
>
> So the path may be absolute but, in such a case, it must contain the
> data directory.
What about the case of a linux-base system. There was another message on
the pgAdmin list mentioning that pg_file_read did not work on Debian. I
used pgAdmin on a Windows system to edit the pg_hba.conf file. No
problems, but emulating that behaviour on linux systems by entering the
SQL commands fails.

I'm using the postgres account and the "SELECT pg_file_read" command
fails if I try to take into account the data directory.
Using:
SELECT * from
pg_read_file('../../../../../etc/postgresql/9.3/main/pg_hba.conf');
will return the error:
ERROR: path must be in or below the current directory

Yet this sequence of commands works for pgAdmin? This is why I'm asking
here if there was some special setup made when calling the config file
editing.

Thanks for the help.
Scott