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diff --git a/fetchmail-FAQ.html b/fetchmail-FAQ.html index ae681705..9787d227 100644 --- a/fetchmail-FAQ.html +++ b/fetchmail-FAQ.html @@ -10,7 +10,7 @@ <table width="100%" cellpadding=0><tr> <td width="30%">Back to <a href="index.html">Fetchmail Home Page</a> <td width="30%" align=center>To <a href="/~esr/sitemap.html">Site Map</a> -<td width="30%" align=right>$Date: 1998/07/20 18:51:59 $ +<td width="30%" align=right>$Date: 1998/07/25 17:15:16 $ </table> <HR> <H1>Frequently Asked Questions About Fetchmail</H1> @@ -55,8 +55,7 @@ IP address?</a><br> <a href="#C1">C1. Why do I need a .fetchmailrc when running as root on my own machine?</a><br> <a href="#C2">C2. How can I arrange for a fetchmail daemon to get killed when I log out?</a><br> <a href="#C3">C3. How do I know what interface and address to use with --interface?</a><br> -<a href="#C4">C4. How can I get fetchmail to work with ssh?</a><br> -<a href="#C5">C5. How can I set up support for sendmail's anti-spam 571 response?</a><br> +<a href="#C4">C4. How can I set up support for sendmail's anti-spam 571 response?</a><br> <h1>How to make fetchmail play nice with other software:</h1> @@ -72,6 +71,8 @@ IP address?</a><br> <a href="#T10">T10. How can I use fetchmail with HP OpenMail?</a><br> <a href="#T11">T11. How can I use fetchmail with SOCKS?</a><br> <a href="#T12">T12. How can I use fetchmail with IPv6 and IPsec?</a><br> +<a href="#T13">T13. How can I get fetchmail to work with ssh?</a><br> +<a href="#T14">T14. What do I have to do to use the IMAP-GSS protocol?</a><br> <h1>Runtime fatal errors:</h1> @@ -363,7 +364,7 @@ alone will really address your security exposure. If you think you might be snooped, it's better to use end-to-end encryption on your whole mail stream so none of it can be read. One of the advantages of fetchmail over conventional SMTP-push delivery is that you may be able -to arrange this by using ssh(1); see <a href="#C4">C4</a>.<P> +to arrange this by using ssh(1); see <a href="#T13">T13</a>.<P> If ssh/sshd isn't available, or you find it too complicated for you to set up, password encryption will at least keep a malicious cracker @@ -830,103 +831,7 @@ would work. To range over any value of the last two octets </pre> <hr> -<h2><a name="C4">C4. How can I get fetchmail to work with ssh?</a></h2> - -We have two recipes for this. The first is a little easier to set up, -but only supports one user at a time.<P> - -First, a lightly edited version of a recipe from Masafumi NAKANE:<p> - -1. You must have ssh (the ssh client) on the local host and sshd (ssh -server) on the remote mail server. And you have to configure ssh so -you can login to the sshd server host without a password. (Refer to ssh -man page for several authentication methods.)<p> - -2. Add something like following to your .fetchmailrc file: <p> - -<pre> -poll mailhost port 1234 via localhost with proto pop3: - preconnect "ssh -f -L 1234:mailhost:110 mailhost sleep 20 </dev/null >/dev/null"; -</pre> - -(Note that 1234 can be an arbitrary port number. Privileged ports can -be specified only by root.) The effect of this ssh command is to -forward connections made to localhost port 1234 (in above example) to -mailhost's 110.<p> - -This configuration will enable secure mail transfer. All the -conversation between fetchmail and remote pop server will be -encrypted.<p> - -If sshd is not running on the remote mail server, you can specify -intermediate host running it. If you do this, however, communication -between the machine running sshd and the POP server will not be encrypted. -And the preconnect line would be like this:<p> - -<pre> -preconnect "ssh -f -L 1234:mailhost:110 sshdhost sleep 20 </dev/null >/dev/null" -</pre> - -You can work this trick with IMAP too, but the port number 110 in the -above would need to become 143.<p> - -Second, a recipe from Charlie Brady <cbrady@ind.tansu.com.au>:<p> - -Charlie says: "The [previous] recipe certainly works, but -the solution I post here is better in a few respects": - -<UL> -<LI>this method will not fail if two or more users attempt to use fetchmail - simultaneously. -<LI>you are able to use the full facilities of tcpd to control access -<LI>this method does not depend on the preconnect feature of fetchmail, so - can be used for tunneling of other services as well. -</UL> - -Here are the steps: - -<OL> -<LI> -Make sure that the "socket" program is installed on the server -machine. Presently it lives at <a -href="ftp://sunsite.unc.edu/pub/linux/system/network/misc/socket-1.1.tar.gz"> -ftp://sunsite.unc.edu/pub/linux/system/network/misc/socket-1.1.tar.gz</a>, -but watch out for a change in version number.<P> -<LI> -Set up an unprivileged account on your system with a .ssh directory -containing an SSH identity file "identity" with no pass phrase, -"identity.pub" and "known_hosts" containing the host key of your -mailhost. Let's call this account "noddy". -<LI> -On mailhost, set up no-password access for noddy@yourhost. Add to your -SSH authorised_keys file: - -<PRE> -command="socket localhost 110",no-port-forwarding 1024 ...... -</PRE> - -where "<code>1024</code> ......" is the content of noddy's identity.pub file. -<LI> -Create a script /usr/local/bin/ssh.fm and make it executable: - -<PRE> -#! /bin/sh -exec ssh -q -C -l your.login.id -e none mailhost socket localhost 110 -</PRE> -<LI> -Add an entry in inetd.conf for whatever port you choose to use - say: - -<PRE> -1234 stream tcp nowait noddy /usr/sbin/tcpd /usr/local/bin/ssh.fm -</PRE> -<LI> -Send a HUP signal to your inetd. -</OL> - -Now just use localhost:1234 to access your POP server.<P> - -<hr> -<h2><a name="C5">C5. How can I set up support for sendmail's anti-spam 571 response?</a></h2> +<h2><a name="C4">C4. How can I set up support for sendmail's anti-spam 571 response?</a></h2> Rachel Polanskis <r.polanskis@nepean.uws.edu.au> writes:<p> @@ -1366,6 +1271,135 @@ http://www.bieringer.de/linux/IPv6/IPv6-HOWTO/IPv6-HOWTO.html</a> </UL> <hr> +<h2><a name="T13">T13. How can I get fetchmail to work with ssh?</a></h2> + +We have two recipes for this. The first is a little easier to set up, +but only supports one user at a time.<P> + +First, a lightly edited version of a recipe from Masafumi NAKANE:<p> + +1. You must have ssh (the ssh client) on the local host and sshd (ssh +server) on the remote mail server. And you have to configure ssh so +you can login to the sshd server host without a password. (Refer to ssh +man page for several authentication methods.)<p> + +2. Add something like following to your .fetchmailrc file: <p> + +<pre> +poll mailhost port 1234 via localhost with proto pop3: + preconnect "ssh -f -L 1234:mailhost:110 mailhost sleep 20 </dev/null >/dev/null"; +</pre> + +(Note that 1234 can be an arbitrary port number. Privileged ports can +be specified only by root.) The effect of this ssh command is to +forward connections made to localhost port 1234 (in above example) to +mailhost's 110.<p> + +This configuration will enable secure mail transfer. All the +conversation between fetchmail and remote pop server will be +encrypted.<p> + +If sshd is not running on the remote mail server, you can specify +intermediate host running it. If you do this, however, communication +between the machine running sshd and the POP server will not be encrypted. +And the preconnect line would be like this:<p> + +<pre> +preconnect "ssh -f -L 1234:mailhost:110 sshdhost sleep 20 </dev/null >/dev/null" +</pre> + +You can work this trick with IMAP too, but the port number 110 in the +above would need to become 143.<p> + +Second, a recipe from Charlie Brady <cbrady@ind.tansu.com.au>:<p> + +Charlie says: "The [previous] recipe certainly works, but +the solution I post here is better in a few respects": + +<UL> +<LI>this method will not fail if two or more users attempt to use fetchmail + simultaneously. +<LI>you are able to use the full facilities of tcpd to control access +<LI>this method does not depend on the preconnect feature of fetchmail, so + can be used for tunneling of other services as well. +</UL> + +Here are the steps: + +<OL> +<LI> +Make sure that the "socket" program is installed on the server +machine. Presently it lives at <a +href="ftp://sunsite.unc.edu/pub/linux/system/network/misc/socket-1.1.tar.gz"> +ftp://sunsite.unc.edu/pub/linux/system/network/misc/socket-1.1.tar.gz</a>, +but watch out for a change in version number.<P> +<LI> +Set up an unprivileged account on your system with a .ssh directory +containing an SSH identity file "identity" with no pass phrase, +"identity.pub" and "known_hosts" containing the host key of your +mailhost. Let's call this account "noddy". +<LI> +On mailhost, set up no-password access for noddy@yourhost. Add to your +SSH authorised_keys file: + +<PRE> +command="socket localhost 110",no-port-forwarding 1024 ...... +</PRE> + +where "<code>1024</code> ......" is the content of noddy's identity.pub file. +<LI> +Create a script /usr/local/bin/ssh.fm and make it executable: + +<PRE> +#! /bin/sh +exec ssh -q -C -l your.login.id -e none mailhost socket localhost 110 +</PRE> +<LI> +Add an entry in inetd.conf for whatever port you choose to use - say: + +<PRE> +1234 stream tcp nowait noddy /usr/sbin/tcpd /usr/local/bin/ssh.fm +</PRE> +<LI> +Send a HUP signal to your inetd. +</OL> + +Now just use localhost:1234 to access your POP server.<P> + +<hr> +<h2><a name="T14">T14. What do I have to do to use the IMAP-GSS protocol?</a></h2> + +Fetchmail can use RFC1731 GSSAPI authorization to safely identify you +to your IMAP server, as long as you can share Kerberos V credentials +with your mail host and you have a GSSAPI-capable IMAP server. +UW-IMAP (available via FTP at <a +href="ftp://ftp.cac.washington.edu/mail/">ftp.cac.washington.edu</a>) +is the only one I'm aware of and the one I recommend anyway for other +reasons. You'll need version 4.1-FINAL or greater though, and it has +to have GSS support compiled in.<p> + +Neither UW-IMAP nor fetchmail compile in support for GSS by default, since +it requires libraries from the Kerberos V distribution (available via FTP at +<a href="ftp://athena-dist.mit.edu/pub/ATHENA/kerberos">athena-dist.mit.edu</a> +but mind the export restrictions). If you have these, compiling in GSS support +is simple: add a <pre>--with-gssapi=[/path/to/krb5/root]</pre> option to +configure. For instance, I have all of my kerberos V libraries installed under +/usr/krb5 so I run <pre>configure --with-gssapi=/usr/krb5</pre>.<p> + +Setting up Kerberos V authentication is beyond the scope of this FAQ, but +you'll need to add a credential for imap/[mailhost] to the keytab of the mail +server (IMAP doesn't just use the host key). Then you'll need to have your +credentials ready on your machine (cf. kinit).<p> + +After that things are very simple. Set your protocol to imap-gss in your +.fetchmailrc, and omit the password, since imap-gss doesn't need one. You +can specify a username if you want, but this is only useful if your mailbox +belongs to a username different from your kerberos principal. <p> + +Now you don't have to worry about your password appearing in cleartext in +your .fetchmailrc, or across the network.<p> + +<hr> <h2><a name="R1">R1. Fetchmail's initial gethostbyname call fails on my host.</a></h2> This is probably due to a DNS or NIS misconfiguration. The first @@ -2052,7 +2086,7 @@ Re-ordering messages is a user-agent function, anyway.<P> <table width="100%" cellpadding=0><tr> <td width="30%">Back to <a href="index.html">Fetchmail Home Page</a> <td width="30%" align=center>To <a href="/~esr/sitemap.html">Site Map</a> -<td width="30%" align=right>$Date: 1998/07/20 18:51:59 $ +<td width="30%" align=right>$Date: 1998/07/25 17:15:16 $ </table> <P><ADDRESS>Eric S. Raymond <A HREF="mailto:esr@thyrsus.com"><esr@snark.thyrsus.com></A></ADDRESS> |