+<chapt>Security Considerations <!--{{{-->
+
+ <p>First of all, mutt-ng contains no security holes included by
+ intention but may contain unknown security holes. As a consequence,
+ please run mutt-ng only with as few permissions as possible.
+
+ <p>Please do not run mutt-ng as the super user.
+
+ <p>When configuring mutt-ng, there're some points to note about secure
+ setups.
+
+ <p>In practice, mutt-ng can be easily made as vulnerable as even the
+ most insecure mail user agents (in their default configuration) just
+ by changing mutt-ng's configuration files: it then can execute
+ arbitrary programs and scripts attached to messages, send out private
+ data on its own, etc. Although this is not believed to the common type
+ of setup, please read this chapter carefully.
+
+ <sect>Passwords <!--{{{-->
+
+ <p>Although mutt-ng can be told the various passwords for accounts,
+ please never store passwords in configuration files. Besides the
+ fact that the system's operator can always read them, you could
+ forget to replace the actual password with asterisks when reporting
+ a bug or asking for help via, for example, a mailing list so that
+ your mail including your password could be archived by internet
+ search engines, etc. Please never store passwords on disk.
+
+ <!--}}}-->
+
+ <sect>Temporary Files <!--{{{-->
+
+ <p>Mutt-ng uses many temporary files for viewing messages, verifying
+ digital signatures, etc. The <ref id="umask" name="$umask">
+ variable can be used to change the default permissions of these
+ files. Please only change it if you really know what you are doing.
+ Also, a different location for these files may be desired which can
+ be changed via the <ref id="tmpdir" name="$tmpdir"> variable.
+
+ <!--}}}-->
+
+ <sect>Information Leaks <!--{{{-->
+
+ <sect1>Message-ID: headers <!--{{{-->
+
+ <p>In the default configuration, mutt-ng will leak some information
+ to the outside world when sending messages: the generation of
+ <tt/Message-ID:/ headers includes a step counter which is increased
+ (and rotated) with every message sent. If you'd like to hide this
+ information probably telling others how many mail you sent in which
+ time, you at least need to remove the <tt/%P/ expando from the
+ default setting of the <ref id="msgid_format"
+ name="$msgid_format"> variable. Please make sure that
+ you really know how local parts of these <tt/Message-ID:/ headers
+ are composed.
+
+ <!--}}}-->
+
+ <sect1>mailto:-style links <!--{{{-->
+
+ <p>As mutt-ng be can be set up to be the mail client to handle
+ <tt/mailto:/ style links in websites, there're security
+ considerations, too. To keep the old behavior by default, mutt-ng
+ will be strict in interpreting them which means that arbitrary
+ header fields can be embedded in these links which could override
+ existing header fields or attach arbitrary files. This may be
+ problematic if the <ref id="edit_headers"
+ name="$edit_headers"> variable is <em/unset/, i.e. the
+ user doesn't want to see header fields while editing the message.
+
+ <p>For example, following a link like
+
+ <verb>
+mailto:joe@host?Attach=~/.gnupg/secring.gpg</verb>
+
+ will send out the user's private gnupg keyring to <tt/joe@host/ if
+ the user doesn't follow the information on screen carefully
+ enough.
+
+ <p>When <em/unsetting/ the <ref id="strict_mailto"
+ name="$strict_mailto"> variable, mutt-ng will
+
+ <itemize>
+
+ <item>be less strict when interpreting these links by
+ prepending a <tt/X-Mailto-/ string to all header fields
+ embedded in such a link <em/and/
+
+ <item>turn on the <ref id="edit_headers"
+ name="$edit_headers"> variable by
+ force to let the user see all the headers
+ (because they still may leak information.)
+
+ </itemize>
+
+ <!--}}}-->
+
+ <!--}}}-->
+
+ <sect>External applications <!--{{{-->
+
+ <p>Mutt-ng in many places has to rely on external applications or
+ for convenience supports mechanisms involving external
+ applications.
+
+ <sect1>mailcap <!--{{{-->
+
+ <p>One of these is the <tt/mailcap/ mechanism as defined by RfC
+ 1524. Mutt-ng can be set up to <em/automatically/ execute any
+ given utility as listed in one of the mailcap files (see the
+ <ref id="mailcap_path" name="$mailcap_path">
+ variable for details.)
+
+ These utilities may have a variety of security vulnerabilities,
+ including overwriting of arbitrary files, information leaks or
+ other exploitable bugs. These vulnerabilities may go unnoticed by
+ the user, especially when they are called automatically (and
+ without interactive prompting) from the mailcap file(s). When
+ using mutt-ng's autoview mechanism in combination with mailcap
+ files, please be sure to...
+
+ <itemize>
+
+ <item>manually select trustworth applications with a reasonable
+ calling sequence
+
+ <item>periodically check the contents of mailcap files,
+ especially after software installations or upgrades
+
+ <item>keep the software packages referenced in the mailcap file up to date
+
+ <item>leave the <ref id="mailcap_sanitize"
+ name="$mailcap_sanitize"> variable in its default
+ state to restrict mailcap expandos to a safe set of characters
+
+ </itemize>
+
+ <!--}}}-->
+
+ <sect1>Other <!--{{{-->
+
+ <p>Besides the mailcap mechanism, mutt-ng uses a number of other
+ external utilities for operation.
+
+ <p>The same security considerations apply for these as for tools
+ involved via mailcap (for example, mutt-ng is vulnerable to Denial
+ of Service Attacks with compressed folders support if the
+ uncompressed mailbox is too large for the disk it is saved to.)
+
+ <p>As already noted, most of these problems are not built in but
+ caused by wrong configuration, so please check your configuration.
+
+ <!--}}}-->
+
+ <!--}}}-->
+
+<!--}}}-->
+
projects / apps / madmutt.git / blobdiff