<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">Le 15/03/2017 à 15:37, Janos
Mattyasovszky a écrit :<br>
</div>
<blockquote
cite="mid:MZZWj-Kbyl5CX68ZKvNVfkVS1S50WYoUYC6ZQGIxxiqIMxOEqiSke60DxemWJc8Yb3Wv_ctdAqhxvIWVb3v6oHI8rD-505ZicOXvwmbkCT8=@matya.hu"
type="cite">
<div>Hi,<br>
</div>
<div><br>
</div>
<div>In my opinion it is not necessary for the Relay to sign
anything not originating directly from that relay. It could of
course double-sign it so the node could also verify that there
is no any kind of MITM, but if we trust cf-serverd to ensure a
secure end-to-end transport of policies, putting on the
signature of the relay is just a small benefit, probably not
directly worth it. If a Relay would become compromised, it would
also mean the private key used to sign anything <b>by</b> the
Relay would also be compromised.<br>
</div>
<div><br>
</div>
<div>The original idea I had in mind is for each Node to validate
that the Policy-updates are originating from the Root server,
and to ensure no bogus policy could be sneaked in if a Relay is
compromised.<br>
</div>
<div><br>
</div>
<div>If the Relay has the task to distribute Files to Nodes on
behalf of the Root server, the Files should be signed by the
Root, and the Nodes should trust the Root and verify the
authenticity if the Signature belongs to the Root. <br>
</div>
<div><br>
</div>
<div>I see multiple possible directions you could go:<br>
</div>
<ul>
<li><u>X509-Certificates:<br>
</u>The Root-Server would be a Certificate Authority (CA) to
sign SSL Certificates for it's Policy Servers<br>
</li>
<ul>
<li>The Policy Servers' Apache installation (Root and Relays)
would get a signed Certificate by this CA:<br>
</li>
<ul>
<li>The WebDAV endpoints would be secured with this
certficate on the Root/Relays<br>
</li>
<li>A newly set up Nodes (not having set up any out-of-band
trust before) could fetch the Certificate-Chain from the
WebDAV endpoint directly at the time they are preparing
the first inventory upload and could establish initial
trust to that (since the Webserver is actually sending
it's SSL Chain to the Client)<br>
</li>
</ul>
<li>The Root Server could use the Private Key for the CA to
sign any Policy intended for an accepted Node.</li>
<ul>
<li>The Node could verify the authenticity of Policy updates
belonging to the same "instance" it established trust
initially (via the SSL Certificate Chain) and would only
accept inventory updates if a checksum file of all updated
files is signed by the RootCA.<br>
</li>
</ul>
<li>Pros:<br>
</li>
<ul>
<li>You make sure all communication over TLS (WebDAV) is
secured properly and trust is established the first time a
Node connects to a WebDAV endpoint of the Server in it's
policy_server.dat.<br>
</li>
<li>It would solve trust of Web-Transport and also
File-Signature by only trusting one "public key",
retrievable only with the knowledge of the policy server
by standard HTTPS-Protocol.<br>
</li>
</ul>
</ul>
</ul>
</blockquote>
<br>
You still need 2 trusts, since the transport over https is done by
communicating with the relay, you also must trust it.<br>
<br>
<blockquote
cite="mid:MZZWj-Kbyl5CX68ZKvNVfkVS1S50WYoUYC6ZQGIxxiqIMxOEqiSke60DxemWJc8Yb3Wv_ctdAqhxvIWVb3v6oHI8rD-505ZicOXvwmbkCT8=@matya.hu"
type="cite">
<ul>
<ul>
<li>Cons:<br>
</li>
<ul>
<li>File-Signing and -Verification with X509 is not easy and
also not designed for, but within the scope of possible<br>
</li>
<li>Rudder-Managing the SSL-Certificates requires all
hostnames / frontends to precisely match of what Rudder
thinks it's called<br>
</li>
</ul>
</ul>
</ul>
</blockquote>
<br>
Since we would use client certificates only for signature and not
for TLS, we can put any name we want in them, and in our case i
would prefer using their uuid instead of their hostname.<br>
With 4.1 we added relay API, and now every relay already have the
information of which hosts has which key behind itself.<br>
<br>
<blockquote
cite="mid:MZZWj-Kbyl5CX68ZKvNVfkVS1S50WYoUYC6ZQGIxxiqIMxOEqiSke60DxemWJc8Yb3Wv_ctdAqhxvIWVb3v6oHI8rD-505ZicOXvwmbkCT8=@matya.hu"
type="cite">
<ul>
<ul>
<ul>
<li>If a Node connects to a compromised Relay, it will trust
that (there is actually no good way to trust something you
know initially nothing of)<br>
</li>
</ul>
</ul>
</ul>
</blockquote>
<br>
Except if you have deployed a CA on the relay and a relay
certificate signed by this CA.<br>
<br>
<blockquote
cite="mid:MZZWj-Kbyl5CX68ZKvNVfkVS1S50WYoUYC6ZQGIxxiqIMxOEqiSke60DxemWJc8Yb3Wv_ctdAqhxvIWVb3v6oHI8rD-505ZicOXvwmbkCT8=@matya.hu"
type="cite">
<ul>
<li><u>GPG Trust:<br>
</u>The Root-Server would have a private GPG Key to a publicly
propagated Signature</li>
<ul>
<li>The Policy Server propagates the signature of the Root
Server's GPG Key via HTTP(s) to anybody asking for it (just
like /uuid).<br>
</li>
<ul>
<li>The Nodes would query the GPG Key's Signature in
addition to the uuid of it's policy server and trust it
the first time they retrieve it.<br>
</li>
<li>The Nodes would verify any Policy-Update with this GPG
Key for authenticity<br>
</li>
</ul>
<li>Pros<br>
</li>
<ul>
<li>GPG is very mature and has good tooling if it comes to
File encryption / verification<br>
</li>
</ul>
</ul>
</ul>
</blockquote>
<br>
openssl also has the feature<br>
<br>
<blockquote
cite="mid:MZZWj-Kbyl5CX68ZKvNVfkVS1S50WYoUYC6ZQGIxxiqIMxOEqiSke60DxemWJc8Yb3Wv_ctdAqhxvIWVb3v6oHI8rD-505ZicOXvwmbkCT8=@matya.hu"
type="cite">
<ul>
<ul>
<ul>
<li>If would also enable you later to use a GPG-Based
solution to encrypt Files for dedicated nodes, so only
they can open it <br>
(if the Nodes were to generate a private GPG key and send
the public key in the initial inventory)</li>
</ul>
<li>Cons:<br>
</li>
<ul>
<li>The Trust of the Web-Endpoints are still subject for the
User to provide valid certificates (btw, currently the
curl has "-k", so that's not really a "trusted" channel
anyway)<br>
</li>
<li>The public part has to be propagated in a way.<br>
</li>
</ul>
</ul>
</ul>
<div><br>
</div>
<div>The question becomes of course a lot trickier if you want to
share files without involving the Root between Nodes <b>and</b>
want the Receiver Node to have the ability to verify the
authenticity of the received files without the direct knowledge
of any cryptographic identifies of the Sender Node :-/ ... Not
sure about that use case, but I think that if you want to make
things secure, you have to first establish some kind of trust
relationship with the Root-Instance, and then let the
Root-Instance distribute any further knowledge about possible
inter-Node trust relationship ...<br>
</div>
<div><br>
</div>
<div>Thanks for reading,</div>
<div class="protonmail_signature_block ">
<div class="protonmail_signature_block-user ">
<div>-- <br>
</div>
<div>Janos Mattyasovszky<br>
</div>
</div>
<div class="protonmail_signature_block-proton
protonmail_signature_block-empty"><br>
</div>
</div>
<div><br>
</div>
<blockquote type="cite" class="protonmail_quote">
<div>-------- Original Message --------<br>
</div>
<div>Subject: Re: [rudder-dev] Strenghten the integrity of the
node policy if using Relays<br>
</div>
<div>Local Time: 15. März 2017 12:20 PM<br>
</div>
<div>UTC Time: 15. März 2017 11:20<br>
</div>
<div>From: <a class="moz-txt-link-abbreviated" href="mailto:benoit.peccatte@normation.com">benoit.peccatte@normation.com</a><br>
</div>
<div>To: Janos Mattyasovszky <a class="moz-txt-link-rfc2396E" href="mailto:mail@matya.eu"><mail@matya.eu></a>,
<a class="moz-txt-link-abbreviated" href="mailto:rudder-dev@lists.rudder-project.org">rudder-dev@lists.rudder-project.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:rudder-dev@lists.rudder-project.org"><rudder-dev@lists.rudder-project.org></a>,
<a class="moz-txt-link-abbreviated" href="mailto:rudder-users@lists.rudder-project.org">rudder-users@lists.rudder-project.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:rudder-users@lists.rudder-project.org"><rudder-users@lists.rudder-project.org></a><br>
</div>
<div><br>
</div>
<div> <br>
</div>
<div class="moz-cite-prefix">Le 14/03/2017 à 10:16, Janos
Mattyasovszky a écrit :<br>
</div>
<blockquote type="cite">
<div>Hi dear Rudder Community, <br>
</div>
<div><br>
</div>
<div><u>The issue:</u><br>
</div>
<div>The policy generated by the Root server is transmitted
encrypted via the Relay servers, but this provides only
transport encryption between the endpoints, and the Relays
basically are by-design MITM hosts, which have the ability
to modify policy files and reports going back through them
(the inventories are signed - so they would break). This
requires that every relay has a high need for <i>integrity</i>,
since there is no real way to determine from a
Rudder-Root-Server point of view if any of the relay behaves
rogue and injects bogus policy and modifies the reports
stream back to represent that all nodes are good, even if
they are not and are executing an attacker-provided modified
policy.<br>
</div>
<div><br>
</div>
<div><u>Proposed solution:</u><br>
</div>
<div>Use cryptographic signature on the generated policy with
the Root Server's RSA key.<br>
</div>
<div><br>
</div>
<div>With the usage of PKI a client can validate the policy
received from the Master before executing it by trusting the
public key of it. This would require the pubkey of the Root
Server to be known to the Nodes. Currently if you have any
Relays in between, they become the effective policy server
for the nodes, and the nodes will not know anything about
the Relay not being the root server (they just behave
identical as if they would be connected to a root server in
the POW of an end-of-the-leaf node).<br>
</div>
</blockquote>
<div><br>
</div>
<div>Does that mean you think the signature should be done by
the relay ?<br>
</div>
<div> <br>
</div>
<div> <br>
</div>
<blockquote type="cite">
<div><br>
</div>
<div>By using a logic like "trust on first use", where the
root server includes it's pubkey in any policy being
generated, and then the node would trust the first key that
it would receive if it has no policy yet, it could establish
a trust until a "rudder agent reset/reinit" would be issued.
After that the node could verify any further policy by
checking the signature of a file containing the hashes of
all the policy files.<br>
</div>
<div><br>
</div>
<div>This would work as long the nodes are not connecting
initially to a compromised relay, or if the Pubkey of the
Root Server is also deployed out-of-band at the time the
rudder-agent package is installed and policy_server.dat is
configured, so basically the node has already an initial
knowledge of the root server's pubkey, and would as of that
only trust policy signed by that root server, regardless of
the path the policy would travel.<br>
</div>
</blockquote>
<div><br>
</div>
<div>Distributing the public key out of band is a possibility,
distributing a CA and checking signature may be better for
long term key management.<br>
</div>
<div> This CA could be managed locally by rudder or be managed
by Normation for its clients.<br>
</div>
<div> <br>
</div>
<div> <br>
</div>
<blockquote type="cite">
<div><br>
</div>
<div>This would raise the overall security level and reducing
the criticality of a relay to "only" require <i>confidentiality</i>,
since any compromise would result in worst case the nodes
behind a relay not executing the compromised policy and if
the relay was faking the expected reports the nodes would
have to send through the relays, so we'd go from "<i>compromising
all nodes below the relay to execute our code</i>" down to
"<i>cutting off the nodes from any new policy update without
being detected by the Root server</i>", which is still a
great improvement, and if you have out-of-Rudder monitoring
for policy updates (#7282), you could detect this by having
nodes not receiving policy updates as scheduled.<br>
</div>
<div><br>
</div>
<div>A second step could be not to send the reports via
unencrpyted UDP Syslog, but use the same method as sending
the inventories: one file with the current run's reports,
signed by the node's key, this would also solve the issue of
not being able to detect any compromised relay.<br>
</div>
</blockquote>
<div><br>
</div>
<div>We took a step forward having signature everywhere, since
the 4.1 we have a relay api to share files between hosts. This
API uses the same signature mechanism as inventories that is
checked everywhere.<br>
</div>
<div> This API could also be used in place of syslog to transmit
signed reporting to the server.<br>
</div>
<div> <br>
</div>
<div> <br>
</div>
<blockquote type="cite">
<div><br>
</div>
<div>Thanks for reading,<br>
</div>
<div><br>
</div>
<div>Best Regards,<br>
</div>
<div class="protonmail_signature_block ">
<div class="protonmail_signature_block-user ">
<div>Janos Mattyasovszky<br>
</div>
</div>
<div class="protonmail_signature_block-proton
protonmail_signature_block-empty"><br>
</div>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<pre wrap="">_______________________________________________
rudder-users mailing list
<a moz-do-not-send="true" rel="noreferrer nofollow noopener" class="moz-txt-link-abbreviated" href="mailto:rudder-users@lists.rudder-project.org">rudder-users@lists.rudder-project.org</a>
<a moz-do-not-send="true" rel="noreferrer nofollow noopener" class="moz-txt-link-freetext" href="http://www.rudder-project.org/mailman/listinfo/rudder-users">http://www.rudder-project.org/mailman/listinfo/rudder-users</a>
</pre>
</blockquote>
<div><br>
</div>
<p><br>
</p>
<div class="moz-signature">
<div>-- <br>
</div>
<div> <br>
</div>
<table border="0" cellpadding="0" cellspacing="2" width="380">
<tbody>
<tr>
<td colspan="2">
<hr><br>
</td>
</tr>
<tr>
<td colspan="2">
<div><b><img alt="Logo Normation"
src="cid:part3.AB538D63.099B6A9C@normation.com"
align="left" height="50" width="50"> <span
class="sig">Benoît Peccatte</span></b><br>
</div>
<div> <span class="sig"><i>Architecte</i></span><br>
</div>
<div> <span class="sig"><a moz-do-not-send="true"
rel="noreferrer nofollow noopener"
class="redlink" href="http://www.normation.com">Normation</a></span><br>
</div>
</td>
</tr>
<tr>
<td colspan="2">
<hr><br>
</td>
</tr>
<tr>
<td colspan="2"><span class="sigsmall"><b>87, Rue de
Turbigo, 75003 Paris, France</b></span><br>
</td>
</tr>
<tr>
<td><span class="sigsmall">Phone:</span><br>
</td>
<td><span class="sigsmall">+33 (0)1 85 08 48 96</span><br>
</td>
</tr>
<tr>
<td colspan="2">
<hr><br>
</td>
</tr>
</tbody>
</table>
</div>
</blockquote>
<div><br>
</div>
</blockquote>
<br>
<p><br>
</p>
<div class="moz-signature">-- <br>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<style type="text/css">
<!--
a.redlink:link { color: #1782E6; }
a.redlink:visited { color: #1782E6; }
.sig { font-family: 'Century Gothic', CenturyGothic, AppleGothic, sans-serif; font-size: small; }
.sigsmall { font-family: 'Century Gothic', CenturyGothic, AppleGothic, sans-serif; font-size: x-small; }
-->
</style>
<table border="0" cellpadding="0" cellspacing="2" width="380">
<tbody>
<tr>
<td colspan="2">
<hr></td>
</tr>
<tr>
<td colspan="2"><b><img alt="Logo Normation"
src="cid:part5.3314AD82.F2F4D5F1@normation.com"
align="left" height="50" hspace="10" width="50"> <span
class="sig">Benoît Peccatte</span></b><br>
<span class="sig"><i>Architecte</i></span><br>
<span class="sig"><a class="redlink"
href="http://www.normation.com">Normation</a></span> </td>
</tr>
<tr>
<td colspan="2">
<hr></td>
</tr>
<tr>
<td colspan="2"><span class="sigsmall"><b>87, Rue de
Turbigo, 75003 Paris, France</b></span></td>
</tr>
<tr>
<td><span class="sigsmall">Phone:</span></td>
<td><span class="sigsmall">+33 (0)1 85 08 48 96</span></td>
</tr>
<tr>
<td colspan="2">
<hr> </td>
</tr>
</tbody>
</table>
</div>
</body>
</html>