path: root/maildir/maildiracl.sgml

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<refentry id="maildiracl">
  <info><author><firstname>Sam</firstname><surname>Varshavchik</surname><contrib>Author</contrib></author><productname>Courier Mail Server</productname></info>

  <refmeta>
    <refentrytitle>maildiracl</refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo class="manual">Double Precision, Inc.</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>maildiracl</refname>
    <refpurpose>manage access control lists</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl</command>
      <arg choice="req" rep="norepeat">-reset</arg>
      <arg choice="req" rep="norepeat"><replaceable>maildir</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl</command>
      <arg choice="req" rep="norepeat">-list</arg>
      <arg choice="req" rep="norepeat"><replaceable>maildir</replaceable></arg>
      <arg choice="req" rep="norepeat"><replaceable>INBOX[.folder]</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl</command>
      <arg choice="req" rep="norepeat">-set</arg>
      <arg choice="req" rep="norepeat"><replaceable>maildir</replaceable></arg>
      <arg choice="req" rep="norepeat"><replaceable>INBOX[.folder]</replaceable></arg>
      <arg choice="req" rep="norepeat"><replaceable>[-]identifier</replaceable></arg>
      <arg choice="req" rep="norepeat"><replaceable>[+/-]rights</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl</command>
      <arg choice="req" rep="norepeat">-delete</arg>
      <arg choice="req" rep="norepeat"><replaceable>maildir</replaceable></arg>
      <arg choice="req" rep="norepeat"><replaceable>INBOX[.folder]</replaceable></arg>
      <arg choice="req" rep="norepeat"><replaceable>[-]identifier</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl</command>
      <arg choice="req" rep="norepeat">-compute</arg>
      <arg choice="req" rep="norepeat"><replaceable>maildir</replaceable></arg>
      <arg choice="req" rep="norepeat"><replaceable>INBOX[.folder]</replaceable></arg>
      <arg choice="req" rep="repeat"><replaceable>identifier</replaceable></arg>
    </cmdsynopsis>

  </refsynopsisdiv>

  <refsect1 id="maildiracl_description">
    <title>DESCRIPTION</title>

    <para>
<command moreinfo="none">maildiracl</command>
manages <quote>access control lists</quote> (or ACLs)
of the <application moreinfo="none">Courier</application> IMAP server maildir folders.
Access control lists are used primarily to provide fine-grained control
for accessing virtual shared folders via IMAP.</para>

      <note>
	<para>
The <application moreinfo="none">Courier</application> IMAP server server implements
two types of shared folders:
filesystem permission-based shared folders,
as well as virtual shared folders based on IMAP access control lists.
Use the <command moreinfo="none">maildiracl</command>
command to set up access control lists for virtual shared folders.
Use the
<ulink url="maildirmake.html"><citerefentry><refentrytitle>maildirmake</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,
command
to implement shared folders based on
filesystem permissions.</para>

	<para>
See the <application moreinfo="none">Courier</application> IMAP
server documentation for additional information
on setting up virtual shared folders.</para>

      </note>

      <refsect2 id="maildiracl_acl_overview">
	<title>ACL overview</title>

      <para>
ACLs provide a fine-grained mechanism for controlling
access to shared folders.
ACLs may be used to specify, for example, that
<literal moreinfo="none">user1</literal> may only open and read the messages in the folder;
and <literal moreinfo="none">user2</literal> can not only do that, but also delete messages,
and create subfolders.</para>

      <para>
Each folder maintains its own individual access control list, that specifies
who can do what to the folder.
An ACL is a list of <quote>identifier</quote> and <quote>rights</quote>
pairs.
Each <quote>identifier</quote> and <quote>rights</quote> pair means that an
entity called <quote>identifier</quote>
(using the <literal moreinfo="none">UTF-8</literal> character set)
is allowed to do <quote>rights</quote>
on this folder.
<quote>rights</quote> consists of one or more letters, each letter
signifies a particular action:</para>

      <variablelist>
	<varlistentry>
	  <term>a</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may modify this folder's ACLs.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>c</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may create subfolders of this folder (this includes renaming another
folder as this folder's subfolders).</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>e</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may remove deleted messages from this folder.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>i</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may add messages to this folder (either uploading them one by one,
or copying messages from another folder).</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>l</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may actually see that this folder exists.
If <replaceable>identifier</replaceable> does not have the <quote>l</quote>
right on this folder, the folder is effectively invisible to
<replaceable>identifier</replaceable>.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>r</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may open this folder.
Note that if <replaceable>identifier</replaceable>
knows the name of this folder, it can open it even if
<replaceable>identifier</replaceable> does not the <quote>l</quote>
right on this folder.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>s</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may mark messages in this folder as seen, or unseen.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>t</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may mark messages in this folder as deleted, or undeleted.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>w</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may change other status flags of messages in this folder.
May also add or remove custom keywords on individual messages.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>x</term>
	  <listitem>
	    <para>
<replaceable>identifier</replaceable>
may delete this folder (which includes renaming this folder as another
mailbox's subfoler.</para>
	  </listitem>
	</varlistentry>
      </variablelist>

      <refsect3 id="maildiracl_negative_rights">
	<title>Negative rights</title>

	<para>
An ACL entry of <quote>-identifier</quote> and <quote>rights</quote>
is called a <quote>negative right</quote>, which
explicitly removes <quote>rights</quote> from <quote>identifier</quote>.
More than one <quote>identifier</quote> is usually used to determine the
actual rights someone has for the given folder.
The actual access rights are determined by taking all rights from all
applicable <replaceable>identifier</replaceable>, than subtracting any
negative rights, as specified in the following section.</para>
      </refsect3>

      <refsect3 id="maildiracl_identifiers">
	<title>Identifiers</title>

	<para>
Access rights on a given folder are computed by obtained the rights
on the following identifiers, then subtracting the negative rights on the
same identifiers:</para>

	<variablelist>
	  <varlistentry>
	    <term><literal moreinfo="none">owner</literal></term>
	    <listitem>
	      <para>
The owner of the maildir containing this folder.
The maildir's INBOX's ACL defaults to all rights for its owner.
A new folder's ACL is the same as its parent's ACL.
In all cases, trying to remove the <quote>a</quote> right from the owner
(either directly or using a negative right) results in an error.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal moreinfo="none">anyone</literal></term>
	    <listitem>
	      <para>
This identifier refers literally to every userid.
The associated rights (or negative rights) are always used.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal moreinfo="none">anonymous</literal></term>
	    <listitem>
	      <para>
This is a synonym from <quote>anyone</quote>.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal moreinfo="none">user=</literal><replaceable>loginid</replaceable></term>
	    <listitem>
	      <para>
Rights (or negative rights) for IMAP account <quote>loginid</quote>.
<note>
		  <para>
<quote>loginid</quote> is what's logged to syslog after a succesful
login.
In some situations <quote>loginid</quote> is not exactly the actual login ID
used by the IMAP client.</para>
		</note>
</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal moreinfo="none">group=</literal><replaceable>name</replaceable></term>
	    <listitem>
	      <para>
Rights (or negative rights) for account group <quote>name</quote>.
Access rights are granted to an account group as a whole.
The account options feature of the Courier Authentication Library specifies
which account belongs to which account group.
See courier-authlib's documentation for more information.
</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal moreinfo="none">administrators</literal></term>
	    <listitem>
	      <para>
This is an alias for <quote>group=administrators</quote>.
Accounts that are members of an account group called
<quote>administrators</quote> are considered administrative accounts, and
automatically receive all access rights on all accessible folders.</para>
	    </listitem>
	  </varlistentry>
	</variablelist>

	<para>
Consider the following access control list:</para>

	<informalexample>
	  <programlisting format="linespecific">
owner          aceilrstwx
anyone         lr
user=john      w
-user=mary     r
administrators aceilrstwx
</programlisting>
	</informalexample>

	<para>
This access control list specifies that the folder's owner has complete
control over the mailbox (as well as the administrators, which have complete
access to every folder); everyone else can see it and open it,
except for <quote>mary</quote> who can see that the mailbox exists, but
can't open it; additionally, <quote>john</quote> can change the status and
keywords of individual messages (but not mark them as deleted/undeleted or
seen/unseen, which requires additional rights).</para>
      </refsect3>
    </refsect2>
  </refsect1>
  <refsect1 id="maildiracl_options">
    <title>OPTIONS</title>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl -reset <replaceable>maildir</replaceable></command>
    </cmdsynopsis>

    <para>
This command resets access control lists in
<filename moreinfo="none"><replaceable>maildir</replaceable></filename>
which as a path to a maildir.
Under certain conditions, the files where a folder's ACLs are saved may
continue to exist after the folder is removed.
The <literal moreinfo="none">-reset</literal> options goes through
<replaceable>maildir</replaceable>
and removes all stale ACL files for removed folders.</para>

    <note>
      <para>
The <application moreinfo="none">Courier</application> IMAP server
normally performs this maintenance
function automatically.
It is not necessary to run this command under normal conditions.</para>
    </note>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl -list
<replaceable>maildir</replaceable>
<replaceable>folder</replaceable>
</command>
    </cmdsynopsis>

      <para>
This command
lists the access control lists set for <replaceable>folder</replaceable>.
<replaceable>folder</replaceable> must be either
<quote>INBOX</quote> or <quote>INBOX.folder.subfolder</quote>, which is the
same naming convention for
the <application moreinfo="none">Courier</application> IMAP server.</para>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl -set
<replaceable>maildir</replaceable>
<replaceable>folder</replaceable>
<replaceable>identifier</replaceable>
<replaceable>rights</replaceable></command>
    </cmdsynopsis>

      <para>
Puts <replaceable>identifier</replaceable> (which may begin with a minus
sign to specify a negative right) and
<replaceable>rights</replaceable> in
<replaceable>folder</replaceable>'s access control list.
Existing rights for
<replaceable>identifier</replaceable>
(or <replaceable>identifier</replaceable>) are replaced by
<replaceable>rights</replaceable> unless <quote>rights</quote> begins with
<quote>+</quote> or <quote>-</quote>, which modifies the existing rights
by adding or removing from them accordingly.
Some examples:</para>

    <informalexample>
      <programlisting format="linespecific">
maildiracl -set /home/user1/Maildir INBOX.Sent user=john lr

maildiracl -set /home/user2/Maildir INBOX.Notes anyone -r

maildiracl -set /home/user3/Maildir INBOX.Private -user=tom +r
</programlisting>
    </informalexample>

    <note>
      <para>
Observe that the last command <emphasis>revokes</emphasis> the <quote>r</quote>
right from <quote>tom</quote>, by adding it as a negative right.</para>
    </note>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl -delete
<replaceable>maildir</replaceable>
<replaceable>folder</replaceable>
<replaceable>identifier</replaceable></command></cmdsynopsis>

      <para>
This command removes <replaceable>identifier</replaceable>
from
<replaceable>folder</replaceable>'s access control list, if it exists.
Use <quote>-<replaceable>identifier</replaceable></quote> to remove
negative rights.</para>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">maildiracl -compute
<replaceable>maildir</replaceable>
<replaceable>folder</replaceable>
[<replaceable>identifier</replaceable>]+</command></cmdsynopsis>

    <para>
This command takes a list of one or more
<replaceable>identifier</replaceable>s.
All access rights for the
<replaceable>identifier</replaceable>s are combined together, then
any appropriate negative rights are removed, and the result is printed
on standard output.
Use the following procedure to compute access rights the same way as they
are computed by
the <application moreinfo="none">Courier</application> IMAP server:</para>

    <informalexample>
      <programlisting format="linespecific">
maildiracl -compute /home/tom46/Maildir INBOX.Sent owner user=tom46
</programlisting>
    </informalexample>

    <para>
This command computes access rights <quote>tom46</quote> has on
his own folder.</para>

    <informalexample>
      <programlisting format="linespecific">
maildiracl -compute /home/john34/Maildir INBOX.Public user=tom46
</programlisting>
    </informalexample>

    <para>
This command computes access rights <quote>tom46</quote> has on
<quote>john34</quote>'s folder.</para>

  </refsect1>

  <refsect1 id="maildiracl_irrevocable_access_rights">
    <title>IRREVOCABLE ACCESS RIGHTS</title>

    <para>
The owner of the mailbox must always have the <quote>a</quote> amd
<quote>l</quote> access rights.
The <literal moreinfo="none">administrators</literal> group must always have all access
rights to all folders.
Attempts to set access control lists, that do not include these minimum
access rights, will be rejected.</para>
  </refsect1>

  <refsect1 id="maildiracl_bugs">
    <title>BUGS</title>

    <para>
All identifiers are specified using the <literal moreinfo="none">UTF-8</literal> character
set.</para>

    <para>
All non-Latin letters in folder names are specified using the
<literal moreinfo="none">modified-UTF7</literal> coding as used in IMAP.</para>

    <para>
This implementation of access control lists is based on
version 2 (or <quote>ACL2</quote>) of IMAP
access control lists, which is a work-in-progress.
The existing IMAP ACL,
<ulink url="http://www.rfc-editor.org/rfc/rfc2086.txt">RFC 2086</ulink>
is transparently implemented inside the ACL2 model.</para>

    <para>
If history's of any guidance, ACL2 is subject to change at any time.
Be sure to check the release notes
when upgrading to a newer version of this software.
The <quote>ACL overview</quote> portion of this manual page is a
<emphasis>very</emphasis> brief summary of ACL2, which leaves out optional
parts of ACL2 that are not implemented.</para>
  </refsect1>

  <refsect1 id="maildiracl_see_also">
    <title>SEE ALSO</title>

    <para>
<ulink url="maildirmake.html"><citerefentry><refentrytitle>maildirmake</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,
<ulink url="maildirkw.html"><citerefentry><refentrytitle>maildirkw</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,</para>
  </refsect1>

</refentry>