Sielco PolyEco Digital FM Transmitter 2.0.6 Authorization Bypass Factory Reset


Vendor: Sielco S.r.l
Product web page: https://www.sielco.org
Affected version: PolyEco1000 CPU:2.0.6 FPGA:10.19
                  PolyEco1000 CPU:1.9.4 FPGA:10.19
                  PolyEco1000 CPU:1.9.3 FPGA:10.19
                  PolyEco500 CPU:1.7.0 FPGA:10.16
                  PolyEco300 CPU:2.0.2 FPGA:10.19
                  PolyEco300 CPU:2.0.0 FPGA:10.19

Summary: PolyEco is the innovative family of high-end digital
FM transmitters of Sielco. They are especially suited as high
performance power system exciters or compact low-mid power
transmitters. The same cabinet may in fact be fitted with 50,
100, 300, 500, 1000W power stage (PolyEco50, 100, 300, 500,
1000).

All features can be controlled via the large touch-screen display
4.3" or remotely. Many advanced features are inside by default
in the basic version such as: stereo and RDS encoder, audio
change-over, remote-control via LAN and SNMP, "FFT" spectral
analysis of the audio sources, SFN synchronization and much more.

Desc: Improper access control occurs when the application provides
direct access to objects based on user-supplied input. As a result
of this vulnerability attackers can bypass authorization and access
resources behind protected pages.

Tested on: lwIP/2.1.1 (http://savannah.nongnu.org/projects/lwip)


Vulnerability discovered by Gjoko 'LiquidWorm' Krstic
Macedonian Information Security Research and Development Laboratory
Zero Science Lab - https://www.zeroscience.mk - @zeroscience


Advisory ID: ZSL-2023-5768
Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2023-5768.php


26.01.2023

--


index.htm:
----------
54: function dologin() {
55:             var hash = hex_md5($('#password').val() + id);
56:             $.get('/login.cgi', {
57:                 user: $('#user').val(),
58:                 password: hash,
59:                 id: id
60:             }).done(function (data) {
61:                 var dati = $.parseXML(data);
62:                 id = $(dati).find('id').text();
63:                 user = $(dati).find('u').text();
64:                 if (id == 0)
65:                     window.location.href = '/index.htm';
66:                 else {
67:                     scriviCookie('polyeco', id, 180);
68:                     if (user >= 3)
69:                         window.location.href = '/protect/factory.htm';
70:                     else
71:                         window.location.href = '/protect/index.htm';
72:                 }
73:             });
74:         }


The function 'dologin()' in index.htm is called when a user submits a login form.
It starts by calculating a hash of the user-entered password and a variable 'id'
using the hex_md5 function. Then it makes an HTTP GET request to the 'login.cgi'
endpoint with the user's entered username, the calculated password hash and the
'id' variable as parameters. If the request is successful, the function parses the
XML data returned from the server, extracting the values of the 'id' and 'u' elements.
Then it checks the value of the 'id' variable, if it's equal to 0 then it redirects
the user to '/index.htm', otherwise, it writes a cookie called 'polyeco' with the
value of 'id' and expires after 180 days.

After that it checks the value of the 'user' variable, if it's greater than or equal
to 3, it redirects the user to '/protect/factory.htm', otherwise it redirects the
user to '/protect/index.htm'. An attacker can exploit this by modifying the client-side
JavaScript to always set the 'user' variable to a high value (4), or by tampering with
the data sent to the server during the login process to change the value of the 'user'
variable. It also works if the server's response variable 'user' is modified.