source: postlfs/security/openssh.xml@ 81a0948

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Last change on this file since 81a0948 was 81a0948, checked in by Bruce Dubbs <bdubbs@…>, 2 years ago

Update to openssh-9.0p1. Includes ssh-askpass.
  • Property mode set to 100644
File size: 19.0 KB
Line 
1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../../general.ent">
5 %general-entities;
6
7 <!ENTITY openssh-download-http
8 "https://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz">
9 <!ENTITY openssh-download-ftp
10 " "> <!-- at the moment, unable to connect via ftp: ken
11 "ftp://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz"> -->
12 <!ENTITY openssh-md5sum "5ed8252a0ee379c0f7c9e0d25d32424d">
13 <!ENTITY openssh-size "1.7 MB">
14 <!ENTITY openssh-buildsize "44 MB (add 21 MB for tests)">
15 <!ENTITY openssh-time "0.2 SBU (Using parallelism=4;
16 running the tests takes about 28 minutes,
17 irrespective of processor speed)">
18]>
19
20<sect1 id="openssh" xreflabel="OpenSSH-&openssh-version;">
21 <?dbhtml filename="openssh.html"?>
22
23 <sect1info>
24 <date>$Date$</date>
25 </sect1info>
26
27 <title>OpenSSH-&openssh-version;</title>
28
29 <indexterm zone="openssh">
30 <primary sortas="a-OpenSSH">OpenSSH</primary>
31 </indexterm>
32
33 <sect2 role="package">
34 <title>Introduction to OpenSSH</title>
35
36 <para>
37 The <application>OpenSSH</application> package contains
38 <command>ssh</command> clients and the <command>sshd</command> daemon.
39 This is useful for encrypting authentication and subsequent traffic over
40 a network. The <command>ssh</command> and <command>scp</command> commands
41 are secure implementations of <command>telnet</command> and
42 <command>rcp</command> respectively.
43 </para>
44
45 &lfs111_checked;
46
47 <bridgehead renderas="sect3">Package Information</bridgehead>
48 <itemizedlist spacing="compact">
49 <listitem>
50 <para>
51 Download (HTTP): <ulink url="&openssh-download-http;"/>
52 </para>
53 </listitem>
54 <listitem>
55 <para>
56 Download (FTP): <ulink url="&openssh-download-ftp;"/>
57 </para>
58 </listitem>
59 <listitem>
60 <para>
61 Download MD5 sum: &openssh-md5sum;
62 </para>
63 </listitem>
64 <listitem>
65 <para>
66 Download size: &openssh-size;
67 </para>
68 </listitem>
69 <listitem>
70 <para>
71 Estimated disk space required: &openssh-buildsize;
72 </para>
73 </listitem>
74 <listitem>
75 <para>
76 Estimated build time: &openssh-time;
77 </para>
78 </listitem>
79 </itemizedlist>
80<!--
81 <bridgehead renderas="sect3">Additional Downloads</bridgehead>
82 <itemizedlist spacing="compact">
83 <listitem>
84 <para>
85 Required patch:
86 <ulink url="&patch-root;/openssh-&openssh-version;-glibc_2.31_fix-1.patch"/>
87 </para>
88 </listitem>
89 </itemizedlist>
90-->
91 <bridgehead renderas="sect3">OpenSSH Dependencies</bridgehead>
92
93 <bridgehead renderas="sect4">Optional</bridgehead>
94 <para role="optional">
95 <xref linkend="gdb"/> (for tests),
96 <xref linkend="linux-pam"/>,
97 <xref linkend="x-window-system"/>,
98 <xref linkend="mitkrb"/>,
99 <xref linkend="which"/> (for tests),
100 <ulink url="http://www.thrysoee.dk/editline/">libedit</ulink>,
101 <ulink url="http://www.libressl.org/">LibreSSL Portable</ulink>,
102 <ulink url="https://github.com/OpenSC/OpenSC/wiki">OpenSC</ulink>, and
103 <ulink url="http://www.citi.umich.edu/projects/smartcard/sectok.html">libsectok</ulink>
104 </para>
105
106 <bridgehead renderas="sect4">Optional Runtime (Used only to gather entropy)</bridgehead>
107 <para role="optional">
108 <!--<xref role="runtime" linkend="openjdk"/>, Not seen in 8.8p1 -->
109 <xref role="runtime" linkend="net-tools"/>, and
110 <xref role="runtime" linkend="sysstat"/>
111 </para>
112
113 <para condition="html" role="usernotes">
114 User Notes: <ulink url="&blfs-wiki;/OpenSSH"/>
115 </para>
116 </sect2>
117
118 <sect2 role="installation">
119 <title>Installation of OpenSSH</title>
120
121 <para>
122 <application>OpenSSH</application> runs as two processes when connecting
123 to other computers. The first process is a privileged process and controls
124 the issuance of privileges as necessary. The second process communicates
125 with the network. Additional installation steps are necessary to set up
126 the proper environment, which are performed by issuing the following
127 commands as the <systemitem class="username">root</systemitem> user:
128 </para>
129
130<screen role="root"><userinput>install -v -m700 -d /var/lib/sshd &amp;&amp;
131chown -v root:sys /var/lib/sshd &amp;&amp;
132
133groupadd -g 50 sshd &amp;&amp;
134useradd -c 'sshd PrivSep' \
135 -d /var/lib/sshd \
136 -g sshd \
137 -s /bin/false \
138 -u 50 sshd</userinput></screen>
139<!--
140 <para>
141 Apply a patch to allow OpenSSH to build and function with
142 <application>Glibc-2.31</application> and later:
143 </para>
144
145<screen><userinput remap="pre">patch -Np1 -i ../openssh-&openssh-version;-glibc_2.31_fix-1.patch</userinput></screen>
146-->
147
148<!-- Applied in 8.5p1
149 <para>
150 First, adapt <application>ssh-copy-id</application> to changes
151 in bash-5.1:
152 </para>
153
154<screen><userinput remap="pre">sed -e '/INSTALLKEYS_SH/s/)//' -e '260a\ )' -i contrib/ssh-copy-id</userinput></screen>
155
156 <para>
157 Next, fix an issue on platforms other than x86_64:
158 </para>
159 <screen><userinput remap="pre">if [ "$(uname -m)" != "x86_64" ]; then
160 l1="#ifdef __NR_pselect6_time64"
161 l2=" SC_ALLOW(__NR_pselect6_time64),"
162 l3="#endif"
163 sed -e "/^#ifdef __NR_read$/ i $l1\n$l2\n$l3" \
164 -i sandbox-seccomp-filter.c
165fi</userinput></screen>
166-->
167 <para>
168 Install <application>OpenSSH</application> by running the following
169 commands:
170 </para>
171
172<!-- -\-with-md5-passwords used to be here, but a comment inside of a <screen>
173 block leaves an eyesore. -->
174<screen><userinput>./configure --prefix=/usr \
175 --sysconfdir=/etc/ssh \
176 --with-privsep-path=/var/lib/sshd \
177 --with-default-path=/usr/bin \
178 --with-superuser-path=/usr/sbin:/usr/bin \
179 --with-pid-dir=/run &amp;&amp;
180make</userinput></screen>
181
182 <para>
183 The testsuite requires an installed copy of <command>scp</command> to
184 complete the multiplexing tests. To run the test suite, first copy the
185 <command>scp</command> program to
186 <filename class="directory">/usr/bin</filename>, making sure that you
187 backup any existing copy first.
188 </para>
189<!-- I got all tests passed without this with 9.0p1. Apr 13, 2022.
190 <para>
191 If you wish to run the tests, remove a test suite that is not valid on
192 Linux-based platforms:
193 </para>
194
195<screen><userinput>sed -i 's/conch-ciphers//' regress/Makefile</userinput></screen>
196-->
197 <para>
198 To test the results, issue: <command>make -j1 tests</command>.
199 <!--One test, <filename>key options</filename>, fails when run in chroot.-->
200 </para>
201
202<!-- commenting this, I get "all tests passed" [ ken ]
203 NB tests should be run as _user_ but the role in the comment is root
204
205 commenting [ bruce ]: There are a couple of tests that want root.
206 The log mentions that SUDO is not set. These skipped tests are
207 ignored and the end says 'all tests passed' even when not root
208
209 <para>
210 To run the test suite, issue the following commands:
211 </para>
212
213<screen role="root"><userinput>make tests 2&gt;&amp;1 | tee check.log
214grep FATAL check.log</userinput></screen>
215
216 <para>
217 If the above command produces no 'FATAL' errors, then proceed with the
218 installation, as the <systemitem class="username">root</systemitem> user:
219 </para>-->
220 <para>
221 Now, as the <systemitem class="username">root</systemitem> user:
222 </para>
223
224<screen role="root"><userinput>make install &amp;&amp;
225install -v -m755 contrib/ssh-copy-id /usr/bin &amp;&amp;
226
227install -v -m644 contrib/ssh-copy-id.1 \
228 /usr/share/man/man1 &amp;&amp;
229install -v -m755 -d /usr/share/doc/openssh-&openssh-version; &amp;&amp;
230install -v -m644 INSTALL LICENCE OVERVIEW README* \
231 /usr/share/doc/openssh-&openssh-version;</userinput></screen>
232 </sect2>
233
234 <sect2 role="commands">
235 <title>Command Explanations</title>
236
237 <para>
238 <parameter>--sysconfdir=/etc/ssh</parameter>: This prevents the
239 configuration files from being installed in
240 <filename class="directory">/usr/etc</filename>.
241 </para>
242
243 <!--
244 <para>
245 <parameter>-\-with-md5-passwords</parameter>: This enables the use of MD5
246 passwords.
247 </para>
248 -->
249
250 <para>
251 <parameter>--with-default-path=/usr/bin</parameter> and
252 <parameter>--with-superuser-path=/usr/sbin:/usr/bin</parameter>:
253 These set <envar>PATH</envar> consistent with LFS and BLFS
254 <application>Shadow</application> package.
255 </para>
256
257 <para>
258 <parameter>--with-pid-dir=/run</parameter>: This prevents
259 <application>OpenSSH</application> from referring to deprecated
260 <filename class="directory">/var/run</filename>.
261 </para>
262
263 <para>
264 <option>--with-pam</option>: This parameter enables
265 <application>Linux-PAM</application> support in the build.
266 </para>
267
268 <para>
269 <option>--with-xauth=/usr/bin/xauth</option>: Set the default
270 location for the <command>xauth</command> binary for X authentication.
271 Change the location if <command>xauth</command> will be installed to a
272 different path. This can also be controlled from
273 <filename>sshd_config</filename> with the XAuthLocation keyword. You can
274 omit this switch if <application>Xorg</application> is already installed.
275 </para>
276
277 <para>
278 <option>--with-kerberos5=/usr</option>: This option is used to
279 include Kerberos 5 support in the build.
280 </para>
281
282 <para>
283 <option>--with-libedit</option>: This option enables line editing
284 and history features for <command>sftp</command>.
285 </para>
286
287 </sect2>
288
289 <sect2 role="configuration">
290 <title>Configuring OpenSSH</title>
291
292 <sect3 id="openssh-config">
293 <title>Config Files</title>
294
295 <para>
296 <filename>~/.ssh/*</filename>,
297 <filename>/etc/ssh/ssh_config</filename>, and
298 <filename>/etc/ssh/sshd_config</filename>
299 </para>
300
301 <indexterm zone="openssh openssh-config">
302 <primary sortas="e-AA.ssh">~/.ssh/*</primary>
303 </indexterm>
304
305 <indexterm zone="openssh openssh-config">
306 <primary sortas="e-etc-ssh-ssh_config">/etc/ssh/ssh_config</primary>
307 </indexterm>
308
309 <indexterm zone="openssh openssh-config">
310 <primary sortas="e-etc-ssh-sshd_config">/etc/ssh/sshd_config</primary>
311 </indexterm>
312
313 <para>
314 There are no required changes to any of these files. However,
315 you may wish to view the
316 <filename class='directory'>/etc/ssh/</filename> files and make any
317 changes appropriate for the security of your system. One recommended
318 change is that you disable
319 <systemitem class='username'>root</systemitem> login via
320 <command>ssh</command>. Execute the following command as the
321 <systemitem class='username'>root</systemitem> user to disable
322 <systemitem class='username'>root</systemitem> login via
323 <command>ssh</command>:
324 </para>
325
326<screen role="root"><userinput>echo "PermitRootLogin no" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
327
328 <para>
329 If you want to be able to log in without typing in your password, first
330 create ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub with
331 <command>ssh-keygen</command> and then copy ~/.ssh/id_rsa.pub to
332 ~/.ssh/authorized_keys on the remote computer that you want to log into.
333 You'll need to change REMOTE_USERNAME and REMOTE_HOSTNAME for the username and hostname of the remote
334 computer and you'll also need to enter your password for the ssh-copy-id command
335 to succeed:
336 </para>
337
338<screen><userinput>ssh-keygen &amp;&amp;
339ssh-copy-id -i ~/.ssh/id_rsa.pub <replaceable>REMOTE_USERNAME</replaceable>@<replaceable>REMOTE_HOSTNAME</replaceable></userinput></screen>
340
341 <para>
342 Once you've got passwordless logins working it's actually more secure
343 than logging in with a password (as the private key is much longer than
344 most people's passwords). If you would like to now disable password
345 logins, as the <systemitem class="username">root</systemitem> user:
346 </para>
347
348
349<screen role="root"><userinput>echo "PasswordAuthentication no" >> /etc/ssh/sshd_config &amp;&amp;
350echo "KbdInteractiveAuthentication no" >> /etc/ssh/sshd_config</userinput></screen>
351
352 <para>
353 If you added <application>Linux-PAM</application> support and you want
354 ssh to use it then you will need to add a configuration file for
355 <application>sshd</application> and enable use of
356 <application>LinuxPAM</application>. Note, ssh only uses PAM to check
357 passwords, if you've disabled password logins these commands are not
358 needed. If you want to use PAM, issue the following commands as the
359 <systemitem class='username'>root</systemitem> user:
360 </para>
361
362<screen role="root"><userinput>sed 's@d/login@d/sshd@g' /etc/pam.d/login &gt; /etc/pam.d/sshd &amp;&amp;
363chmod 644 /etc/pam.d/sshd &amp;&amp;
364echo "UsePAM yes" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
365
366 <para>
367 Additional configuration information can be found in the man
368 pages for <command>sshd</command>, <command>ssh</command> and
369 <command>ssh-agent</command>.
370 </para>
371 </sect3>
372
373 <sect3 id="openssh-init">
374 <title><phrase revision="sysv">Boot Script</phrase>
375 <phrase revision="systemd">Systemd Unit</phrase></title>
376
377 <para revision="sysv">
378 To start the SSH server at system boot, install the
379 <filename>/etc/rc.d/init.d/sshd</filename> init script included
380 in the <xref linkend="bootscripts"/> package.
381 </para>
382
383 <para revision="systemd">
384 To start the SSH server at system boot, install the
385 <filename>sshd.service</filename> unit included in the
386 <xref linkend="systemd-units"/> package.
387 </para>
388
389 <indexterm zone="openssh openssh-init">
390 <primary sortas="f-sshd">sshd</primary>
391 </indexterm>
392
393<screen role="root"><userinput>make install-sshd</userinput></screen>
394 </sect3>
395 </sect2>
396
397 <sect2 role="content">
398 <title>Contents</title>
399
400 <segmentedlist>
401 <segtitle>Installed Programs</segtitle>
402 <segtitle>Installed Libraries</segtitle>
403 <segtitle>Installed Directories</segtitle>
404
405 <seglistitem>
406 <seg>
407 scp, sftp, <!--slogin (symlink to ssh),--> ssh, ssh-add, ssh-agent,
408 ssh-copy-id, ssh-keygen, ssh-keyscan, and sshd
409 </seg>
410 <seg>
411 None
412 </seg>
413 <seg>
414 /etc/ssh,
415 /usr/share/doc/openssh-&openssh-version;, and
416 /var/lib/sshd
417 </seg>
418 </seglistitem>
419 </segmentedlist>
420
421 <variablelist>
422 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
423 <?dbfo list-presentation="list"?>
424 <?dbhtml list-presentation="table"?>
425
426 <varlistentry id="scp">
427 <term><command>scp</command></term>
428 <listitem>
429 <para>
430 is a file copy program that acts like <command>rcp</command> except
431 it uses an encrypted protocol
432 </para>
433 <indexterm zone="openssh scp">
434 <primary sortas="b-scp">scp</primary>
435 </indexterm>
436 </listitem>
437 </varlistentry>
438
439 <varlistentry id="sftp">
440 <term><command>sftp</command></term>
441 <listitem>
442 <para>
443 is an FTP-like program that works over the SSH1 and SSH2 protocols
444 </para>
445 <indexterm zone="openssh sftp">
446 <primary sortas="b-sftp">sftp</primary>
447 </indexterm>
448 </listitem>
449 </varlistentry>
450<!-- Not installed anymore as of 8.5p1
451 <varlistentry id="slogin">
452 <term><command>slogin</command></term>
453 <listitem>
454 <para>
455 is a symlink to <command>ssh</command>
456 </para>
457 <indexterm zone="openssh slogin">
458 <primary sortas="b-slogin">slogin</primary>
459 </indexterm>
460 </listitem>
461 </varlistentry>
462-->
463 <varlistentry id="ssh">
464 <term><command>ssh</command></term>
465 <listitem>
466 <para>
467 is an <command>rlogin</command>/<command>rsh</command>-like client
468 program except it uses an encrypted protocol
469 </para>
470 <indexterm zone="openssh ssh">
471 <primary sortas="b-ssh">ssh</primary>
472 </indexterm>
473 </listitem>
474 </varlistentry>
475
476 <varlistentry id="sshd">
477 <term><command>sshd</command></term>
478 <listitem>
479 <para>
480 is a daemon that listens for <command>ssh</command> login requests
481 </para>
482 <indexterm zone="openssh sshd">
483 <primary sortas="b-sshd">sshd</primary>
484 </indexterm>
485 </listitem>
486 </varlistentry>
487
488 <varlistentry id="ssh-add">
489 <term><command>ssh-add</command></term>
490 <listitem>
491 <para>
492 is a tool which adds keys to the <command>ssh-agent</command>
493 </para>
494 <indexterm zone="openssh ssh-add">
495 <primary sortas="b-ssh-add">ssh-add</primary>
496 </indexterm>
497 </listitem>
498 </varlistentry>
499
500 <varlistentry id="ssh-agent">
501 <term><command>ssh-agent</command></term>
502 <listitem>
503 <para>
504 is an authentication agent that can store private keys
505 </para>
506 <indexterm zone="openssh ssh-agent">
507 <primary sortas="b-ssh-agent">ssh-agent</primary>
508 </indexterm>
509 </listitem>
510 </varlistentry>
511
512 <varlistentry id="ssh-copy-id">
513 <term><command>ssh-copy-id</command></term>
514 <listitem>
515 <para>
516 is a script that enables logins on remote machines using local keys
517 </para>
518 <indexterm zone="openssh ssh-copy-id">
519 <primary sortas="b-ssh-copy-id">ssh-copy-id</primary>
520 </indexterm>
521 </listitem>
522 </varlistentry>
523
524 <varlistentry id="ssh-keygen">
525 <term><command>ssh-keygen</command></term>
526 <listitem>
527 <para>
528 is a key generation tool
529 </para>
530 <indexterm zone="openssh ssh-keygen">
531 <primary sortas="b-ssh-keygen">ssh-keygen</primary>
532 </indexterm>
533 </listitem>
534 </varlistentry>
535
536 <varlistentry id="ssh-keyscan">
537 <term><command>ssh-keyscan</command></term>
538 <listitem>
539 <para>
540 is a utility for gathering public host keys from a number of hosts
541 </para>
542 <indexterm zone="openssh ssh-keyscan">
543 <primary sortas="b-ssh-keyscan">ssh-keyscan</primary>
544 </indexterm>
545 </listitem>
546 </varlistentry>
547
548 </variablelist>
549 </sect2>
550
551</sect1>
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