Insufficient protection against 'clickjacking'

Summary:
========

  LedgerSMB does not sufficiently guard against being wrapped by
  other sites, making it vulnerable to 'clickjacking. This allows
  an attacker to trick a targetted user to execute unintended actions.


Known vulnerable:
=================

  All of:

  - 1.1.0 upto 1.1.12 (including)
  - 1.2.0 upto 1.2.26 (including)
  - 1.3.0 upto 1.3.47 (including)
  - 1.4.0 upto 1.4.42 (including)
  - 1.5.0 upto 1.5.30 (including)
  - 1.6.0 upto 1.6.33 (including)
  - 1.7.0 upto 1.7.32 (including)
  - 1.8.0 upto 1.8.17 (including)


Known fixed:
============

  - 1.7.33
  - 1.8.18


Details:
========

  In a clickjacking attack, an attacker (invisibly) wraps the vulnerable
  site in his own site, carefully placing elements of his own site over
  elements of the wrapped site, tricking the user into performing unintended
  actions on the vulnerable site. More information on clickjacking is on the
  OWASP page at https://owasp.org/www-community/attacks/Clickjacking

  The lack of protection dates back to version 1.0, although it must
  be noted that mitigation measures were first available in browsers
  as of 2011 -- the year of the release of 1.3.0.


Severity:
=========

  CVSSv3.1 Base Score: 5.9 (Medium)

  CVSSv3.1 Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N


Recommendations:
================

  We recommend all users to upgrade to known-fixed versions. Versions prior
  to 1.7 are end-of-life and will not receive security fixes from the
  LedgerSMB project.

  Users who cannot upgrade, may apply the included patches or are advised
  to contact a vendor for custom support.

  As a workaround, administrators may configure their webservers to add
  the Content-Security-Policy header as documented in the content
  security policy site at https://content-security-policy.com/#server.


References:
===========

  CVE-2021-3731  (LedgerSMB)

  https://ledgersmb.org/cve-2021-3731-clickjacking

  https://huntr.dev/bounties/5664331d-f5f8-4412-8566-408f8655888a/


Reported by:
============

  sudheendra17, user of the huntr.dev platform


Patches:
========


Patch for LedgerSMB 1.8 (1.8.0 upto 1.8.17, including):
-------------------------------------------------------

[[[
diff --git a/lib/LedgerSMB/PSGI.pm b/lib/LedgerSMB/PSGI.pm
index b0b20a95b..a4785a9f1 100644
--- a/lib/LedgerSMB/PSGI.pm
+++ b/lib/LedgerSMB/PSGI.pm
@@ -122,6 +122,9 @@ sub old_app {
         return Plack::Util::response_cb(
             $handler->($env),
             sub {
+                Plack::Util::header_set($_[0]->[1],
+                                        'Content-Security-Policy',
+                                        q{frame-ancestors 'self'});
                 if (not Plack::Util::header_exists($_[0]->[1],
                                                    'X-LedgerSMB-App-Content')) {
                     Plack::Util::header_push($_[0]->[1],
@@ -179,6 +182,9 @@ sub psgi_app {
         }
     };
 
+    Plack::Util::header_set($res->[1],
+                            'Content-Security-Policy',
+                            q{frame-ancestors 'self'});
     return $res;
 }
 
]]]

Patch for LedgerSMB 1.7 (1.7.0 upto 1.7.32, including):
-------------------------------------------------------

[[[
diff --git a/lib/LedgerSMB/PSGI.pm b/lib/LedgerSMB/PSGI.pm
index ec8be07f1..bcb478524 100644
--- a/lib/LedgerSMB/PSGI.pm
+++ b/lib/LedgerSMB/PSGI.pm
@@ -91,6 +91,9 @@ sub old_app {
         return Plack::Util::response_cb(
             $handler->(@_),
             sub {
+                Plack::Util::header_set($_[0]->[1],
+                                        'Content-Security-Policy',
+                                        q{frame-ancestors 'self'});
                 if (not Plack::Util::header_exists($_[0]->[1],
                                                    'X-LedgerSMB-App-Content')) {
                     Plack::Util::header_push($_[0]->[1],
@@ -159,6 +162,9 @@ sub psgi_app {
         }
     };
 
+    Plack::Util::header_set($res->[1],
+                            'Content-Security-Policy',
+                            q{frame-ancestors 'self'});
     return $res;
 }
 
]]]


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