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<title>SSL/TLS Settings</title>
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<h1 id="ssltls_settings">SSL/TLS Settings</h1>
<p>This section describes how to set your SSL/TLS preferences.</p>
<div class="contentsBox">In this section:
<ul>
<li><a href="#privacy_and_security_preferences_ssltls">Privacy & Security
Preferences - SSL/TLS</a></li>
</ul>
</div>
<h2 id="privacy_and_security_preferences_ssltls">Privacy & Security
Preferences - SSL/TLS</h2>
<p>This section describes how to use the SSL/TLS preferences panel. If you are
not already viewing the panel, follow these steps:</p>
<ol>
<li>Open the <span class="mac">&brandShortName;</span>
<span class="noMac">Edit</span> menu and choose Preferences.</li>
<li>Under the Privacy & Security category, click SSL/TLS. (If no
subcategories are visible, double-click Privacy & Security to expand
the list.)</li>
</ol>
<h3 id="ssltls_protocol_versions">SSL/TLS Protocol Versions</h3>
<p>The <a href="glossary.xhtml#ssl">Secure Sockets Layer (SSL)</a> protocol
and its successor, the <a href="glossary.xhtml#tls">Transport Layer Security
(TLS)</a> protocol, are standards which define rules governing mutual
authentication between a website and browser software and the encryption
of information that flows between them. They are also used for secure
communication in various other protocols, e.g., for protection of sensitive
information exchanged with email, calendar, or directory servers.</p>
<p>The SSL 2.0 and SSL 3.0 protocols are insecure and thus deprecated. The
current TLS protocol is based on SSL but with its own version numbering.
TLS 1.0 can be thought of as SSL 3.1, TLS 1.1 is in turn an update to TLS
1.0, etc. Newer protocols are preferred over older ones as they provide
better security and more features. Older protocols are supported to ensure
compatibility.</p>
<p>By default, &brandShortName; will select the most secure version which is
widely supported to connect to the server. If that attempt doesn't
succeed, it will try to connect with the next older version, etc., to the
extent allowed by the settings in this panel. The connection will fail if no
protocol supported by both sides is found. You can exclude older versions
explicitly or allow newer versions which may not be widely supported yet
with the following options:</p>
<ul>
<li><strong>Enable</strong>: Check the <strong>TLS 1.0</strong>,
<strong>TLS 1.1</strong>, <strong>TLS 1.2</strong>, and/or
<strong>TLS 1.3</strong> boxes to indicate which protocol versions can be
used for a secure connection to a server.</li>
</ul>
<p><strong>Notes</strong>:</p>
<ul>
<li>At least one protocol version must be selected, thus it is not possible
to uncheck the last remaining box.</li>
<li>Also, the selection must be contiguous. It is not possible to select both
TLS 1.0 and TLS 1.2 but to exclude the intermediate TLS 1.1 version.</li>
<li>You can extend the range by multiple versions. For example, if only TLS
1.0 is currently checked and you select TLS 1.2, the TLS 1.1 version is
automatically selected as well.</li>
<li>Checkboxes may appear checked but grayed out if you cannot uncheck them
without violating these rules. Uncheck the outermost boxes to regain
access to an enclosed intermediate version.</li>
</ul>
<h3 id="ssltls_warnings">SSL/TLS Warnings</h3>
<p>It's easy to tell when the website you are viewing is using an encrypted
connection. If the connection is encrypted, the lock icon in the lower-right
corner of the browser window is locked
connection is not encrypted, the lock icon is unlocked
pages which contain some unencrypted items (mixed content) are shown with a
broken-lock icon
<p>If you want additional warnings, you can select one or more of the warning
checkboxes in the SSL/TLS preferences panel. Unless stated otherwise, a
notification bar will be presented at the top of the page triggering the
alert, with an option to enter this panel to change the option if the alert
is considered annoying.</p>
<p>To activate any of these warnings, select the corresponding checkbox:</p>
<ul>
<li><strong>Loading a page that supports encryption</strong>: Select this
warning if you want to be reminded whenever you are loading a page that
supports encryption.</li>
<li><strong>Leaving a page that supports encryption</strong>: Select this
warning if you want to be reminded whenever you are leaving a page that
supports encryption for one that does not.</li>
<li><strong>Sending form data from an unencrypted page to an unencrypted
page</strong>: Select this warning if you want to be alerted whenever you
are submitting data over an unencrypted connection. When this option is
selected, a dialog box will be presented to the user <em>before</em> the
page is actually opened, which allows the loading of the page to be
canceled before any potentially sensitive information is sent over an
unencrypted connection that can easily be intercepted by others.
<p><strong>Note</strong>: Submitting a form from an encrypted to an
unencrypted page will always prompt a dialog prior to opening the page,
regardless of this setting.</p>
</li>
</ul>
<h3 id="mixed_content">Mixed Content</h3>
<p>In general, there are two major issues related to transmitting sensitive
information over an unencrypted connection: One is the danger of someone
eavesdropping on the line, thus listening to the content transmitted; the
other of someone intercepting requests for the desired page and replacing
the legitimate content of that page with own (potentially malicious)
content. While so-called <q>Man In The Middle</q> attacks can usually be
detected in encrypted connections (e.g., by a certificate mismatch or an
invalid certificate presented by the interceptor), no such verification
exists for unencrypted connections.</p>
<p>The term <q>Mixed Content</q> refers to a web page which itself is
encrypted, but which includes content on the same or a different server
which is <em>not</em> encrypted. Consequently, this part of the page is
still subject to the vulnerabilities of an unencrypted line. While there
are legitimate uses of that concept (such as including a company logo from
a different insecure website into an otherwise secure page), such designs
should be avoided.</p>
<p>There are two general types of mixed content:</p>
<ul>
<li><strong>Mixed Active Content</strong> (or Mixed Script Content): This
is content which has the potential to hide or modify parts of a web page,
or to actively leak content from the secure part of the page to its
insecure part. Examples include scripts (JavaScript), style sheets (CSS),
or the embedding of entire web pages into the main web page (iframes).</li>
<li><strong>Mixed Passive Content</strong> (or Mixed Display Content):
This type of content does <em>not</em> have the potential to alter or
monitor the web page as such. Examples include images and audio or video
streams. It is however possible that sensitive information is passed as
an encoding of the content's location (URL), as cookies, or returned
with the content itself (e.g., as text included in an image). Thus, passive
content isn't entirely harmless either.</li>
</ul>
<p>The following options allow you to be warned about and/or to block both
mixed active and mixed passive content:</p>
<ul>
<li><strong>Warn me when encrypted pages contain insecure content</strong>:
Check this to instruct &brandShortName; to present a notification bar when
mixed <em>active</em> content was loaded or blocked. The notification bar
contains a button to open this preference panel.</li>
<li><strong>Don't load insecure content on encrypted pages</strong>:
Check this to prevent mixed active content from being loaded at all but
to be blocked. If also the <q>Warn me</q> option is checked, the
notification bar will contain two additional buttons:
<ul>
<li><strong>Keep Blocking</strong>: Dismiss the notification bar without
loading the potentially insecure content.</li>
<li><strong>Unblock</strong>:
Load the potentially insecure content <em>once</em> but not
automatically when this page is visited again in the future.</li>
</ul>
<strong>Note</strong>: The selection of <q>Unblock</q> for a specific site
can be revoked in the Permissions tab of the Data Manager. When in a
<a href="using_priv_help.xhtml#browsing_in_a_private_window">private
window</a>, these options aren't available in the notification bar.
</li>
<li><strong>Warn me when encrypted pages contain other types of mixed
content</strong>: Check this to instruct &brandShortName; to present a
notification bar when mixed <em>passive</em> content was loaded or blocked.
The notification bar contains a button to open this preference panel.</li>
<li><strong>Don't load other types of mixed content on encrypted
pages</strong>: Check this to prevent mixed passive content from being
loaded at all but to be blocked. If also the <q>Warn me</q> option is
checked, a notification is presented that such content was blocked.</li>
</ul>
<p>For short definitions, click
<a href="glossary.xhtml#authentication">authentication</a>,
<a href="glossary.xhtml#encryption">encryption</a>, or
<a href="glossary.xhtml#certificate">certificate</a>.</p>
<p>For more information about ciphers and encryption, see the following online
documents:</p>
<ul>
<li>
<a href="https://developer.mozilla.org/en-US/docs/Introduction_to_Public-Key_Cryptography">Introduction
to Public-Key Cryptography</a></li>
<li>
to SSL</a></li>
<li>
Available in the Network Security Services (NSS)</a>.</li>
</ul>
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