Installing PL/Python Extension
While PL/Python is an untrusted language inside PostgreSQL, I was installing it to test some of its features. First, we check to see if PL/Python is installed by attempting to create a PL/Python function:
CREATE FUNCTION pima(a integer, b integer) RETURNS integer AS $$ if a > b: return a return b $$ LANGUAGE plpython3u; |
It likely should raise an error like this because PL/Python is an untrusted language. It’s untrusted because it runs with root privileges rather than a restricted user’s privilege. More or less, with PL/Python you can access the entire database. This makes PL/Python more of a threat than tool beyond experimentation in a test database.
ERROR: language "plpython3u" does not exist HINT: Use CREATE EXTENSION to load the language into the database. |
A quick query as the postgres user tells you whether or not PL/Python is installed:
SELECT * FROM pg_language; |
It returns the following:
lanname | lanowner | lanispl | lanpltrusted | lanplcallfoid | laninline | lanvalidator | lanacl ----------+----------+---------+--------------+---------------+-----------+--------------+-------- internal | 10 | f | f | 0 | 0 | 2246 | c | 10 | f | f | 0 | 0 | 2247 | sql | 10 | f | t | 0 | 0 | 2248 | plpgsql | 10 | t | t | 14088 | 14089 | 14090 | (4 rows) |
I attempted to add PL/Python with the following command:
CREATE EXTENSION plpython3u; |
It raised the following error:
ERROR: could not open extension control file "/usr/pgsql-11/share/extension/plpython3u.control": No such file or directory |
The error basically appeared to occur because there’s a missing Python 3 package from what I could find on the web. I installed the missing postgresql-plpython3 package as the root superuser, which you also could install as a member of the sudoer list. The following shows how to install it as a sudoer member:
sudo yum install -y postgresql-plpython3 |
You should see something close to the following console output:
Last metadata expiration check: 0:43:53 ago on Fri 06 Nov 2020 10:42:28 AM MST. Dependencies resolved. ============================================================================================================ Package Architecture Version Repository Size ============================================================================================================ Installing: postgresql-plpython3 x86_64 11.7-2.fc30 updates 86 k Installing dependencies: postgresql-server x86_64 11.7-2.fc30 updates 5.3 M Transaction Summary ============================================================================================================ Install 2 Packages Total download size: 5.3 M Installed size: 23 M Downloading Packages: (1/2): postgresql-plpython3-11.7-2.fc30.x86_64.rpm 218 kB/s | 86 kB 00:00 (2/2): postgresql-server-11.7-2.fc30.x86_64.rpm 3.0 MB/s | 5.3 MB 00:01 ------------------------------------------------------------------------------------------------------------ Total 2.1 MB/s | 5.3 MB 00:02 Running transaction check Transaction check succeeded. Running transaction test Transaction test succeeded. Running transaction Preparing : 1/1 Running scriptlet: postgresql-server-11.7-2.fc30.x86_64 1/2 Installing : postgresql-server-11.7-2.fc30.x86_64 1/2 warning: /var/lib/pgsql/.bash_profile created as /var/lib/pgsql/.bash_profile.rpmnew Running scriptlet: postgresql-server-11.7-2.fc30.x86_64 1/2 Installing : postgresql-plpython3-11.7-2.fc30.x86_64 2/2 Running scriptlet: postgresql-plpython3-11.7-2.fc30.x86_64 2/2 Verifying : postgresql-plpython3-11.7-2.fc30.x86_64 1/2 Verifying : postgresql-server-11.7-2.fc30.x86_64 2/2 Installed: postgresql-plpython3-11.7-2.fc30.x86_64 postgresql-server-11.7-2.fc30.x86_64 Complete! |
While I thought this might fix the problem, it didn’t and raised the following error:
ERROR: could not open extension control file "/usr/pgsql-11/share/extension/plpython3u.control": No such file or directory |
I found the plpython3u.control file on GitHub and put the following plpython3u.control file, after comparing it against the plpgsql.control file, into the /usr/pgsql-11/share/extension directory. At this point, I began wondering why it’s looking in the /usr/pgsql-11/share/extension directory instead of a /usr/plpython3u/share/extension directory (does not exist).
# plpython3u extension comment = 'PL/Python3U untrusted procedural language' default_version = '1.0' module_pathname = '$libdir/plpython3' relocatable = false schema = pg_catalog superuser = true |
I retried creating the plpython3u extension:
CREATE EXTENSION plpython3u; |
It raised the following error:
ERROR: extension "plpython3u" has no installation script nor update path for version "1.0" |
At this point, I could find no further help on the Internet. I did notice that there were these two *.sql files in the /usr/pgsql-11/share/extension directory:
- plpgsql–1.0.sql
- plpgsql–unpackaged–1.0.sql
I found this plpython3u--1.0.sql file on GitHub:
/* src/pl/plpython/plpython3u--1.0.sql */ CREATE FUNCTION plpython3_call_handler() RETURNS language_handler LANGUAGE c AS 'MODULE_PATHNAME'; CREATE FUNCTION plpython3_inline_handler(internal) RETURNS void STRICT LANGUAGE c AS 'MODULE_PATHNAME'; CREATE FUNCTION plpython3_validator(oid) RETURNS void STRICT LANGUAGE c AS 'MODULE_PATHNAME'; CREATE LANGUAGE plpython3u HANDLER plpython3_call_handler INLINE plpython3_inline_handler VALIDATOR plpython3_validator; COMMENT ON LANGUAGE plpython3u IS 'PL/Python3U untrusted procedural language'; |
I retried creating the plpython3u extension, as a member of the sudoer list and got a new error:
ERROR: permission denied to create extension "plpython3u" HINT: Must be superuser to create this extension. |
I retried creating the plpython3u extension as the postgres user, who is the owning user:
CREATE EXTENSION plpython3u; |
It raised the following error:
ERROR: could not access file "$libdir/plpython3": No such file or directory |
While I intend to finish this, that’s as far as I got. It appears from some of the things I’ve read I need to recompile or configure items that would destabilize what I have working at the moment. Finishing this will need to wait for me to build another test environment from scratch. If you catch this post and know the remaining steps, I invite you to add them in the comments.
Subscribe via RSS