source: postlfs/security/openssh.xml@ 85ec85ef

gnome
Last change on this file since 85ec85ef was 85ec85ef, checked in by Christopher Gregory <cjg@…>, 10 years ago

Added new subdirectory intro to gnome Added new Introduction chapter to Gnome which mirrors what has been done with kde Moved gnome-intro page into
the subdirectory intro in gnome directory Added gnome-intro page href to newly created introduction page Removed excess white space from the gpm page
Removed excess white space from the rsync page Removed excess white space from the wicd page Removed excess white space from the openssh page
Removed text block regarding other desktops from gnome platform page to add it to newly created intro section

git-svn-id: svn://svn.linuxfromscratch.org/BLFS/branches/gnome@13435 af4574ff-66df-0310-9fd7-8a98e5e911e0
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File size: 18.7 KB
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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 "http://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz">
9 <!ENTITY openssh-download-ftp
10 "ftp://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz">
11 <!ENTITY openssh-md5sum "3e9800e6bca1fbac0eea4d41baa7f239">
12 <!ENTITY openssh-size "1.3 MB">
13 <!ENTITY openssh-buildsize "32 MB (additional 2 MB if running the tests)">
14 <!ENTITY openssh-time "0.5 SBU (running the tests takes at least 10
15 minutes, irrespective of processor speed)">
16]>
17
18<sect1 id="openssh" xreflabel="OpenSSH-&openssh-version;">
19 <?dbhtml filename="openssh.html"?>
20
21 <sect1info>
22 <othername>$LastChangedBy$</othername>
23 <date>$Date$</date>
24 </sect1info>
25
26 <title>OpenSSH-&openssh-version;</title>
27
28 <indexterm zone="openssh">
29 <primary sortas="a-OpenSSH">OpenSSH</primary>
30 </indexterm>
31
32 <sect2 role="package">
33 <title>Introduction to OpenSSH</title>
34
35 <para>
36 The <application>OpenSSH</application> package contains
37 <command>ssh</command> clients and the <command>sshd</command> daemon. This
38 is useful for encrypting authentication and subsequent traffic over a
39 network. The <command>ssh</command> and <command>scp</command> commands are
40 secure implementions of <command>telnet</command> and <command>rcp</command>
41 respectively.
42 </para>
43
44 &lfs75_checked;
45
46 <bridgehead renderas="sect3">Package Information</bridgehead>
47 <itemizedlist spacing="compact">
48 <listitem>
49 <para>
50 Download (HTTP): <ulink url="&openssh-download-http;"/>
51 </para>
52 </listitem>
53 <listitem>
54 <para>
55 Download (FTP): <ulink url="&openssh-download-ftp;"/>
56 </para>
57 </listitem>
58 <listitem>
59 <para>
60 Download MD5 sum: &openssh-md5sum;
61 </para>
62 </listitem>
63 <listitem>
64 <para>
65 Download size: &openssh-size;
66 </para>
67 </listitem>
68 <listitem>
69 <para>
70 Estimated disk space required: &openssh-buildsize;
71 </para>
72 </listitem>
73 <listitem>
74 <para>
75 Estimated build time: &openssh-time;
76 </para>
77 </listitem>
78 </itemizedlist>
79
80 <bridgehead renderas="sect3">OpenSSH Dependencies</bridgehead>
81
82 <bridgehead renderas="sect4">Required</bridgehead>
83 <para role="required"><xref linkend="openssl"/></para>
84
85 <bridgehead renderas="sect4">Optional</bridgehead>
86 <para role="optional">
87 <xref linkend="linux-pam"/>,
88 <xref linkend="x-window-system"/>,
89 <xref linkend="mitkrb"/>,
90 <ulink url="http://www.thrysoee.dk/editline/">libedit</ulink>,
91 <ulink url="http://www.opensc-project.org/">OpenSC</ulink>, and
92 <ulink url="http://www.citi.umich.edu/projects/smartcard/sectok.html">libsectok</ulink>
93 </para>
94
95 <bridgehead renderas="sect4">Optional Runtime (Used only to gather entropy)</bridgehead>
96 <para role="optional">
97 <xref linkend="openjdk"/>,
98 <xref linkend="net-tools"/>, and
99 <xref linkend="sysstat"/>.
100 </para>
101
102 <para condition="html" role="usernotes">
103 User Notes: <ulink url="&blfs-wiki;/OpenSSH"/>
104 </para>
105 </sect2>
106
107 <sect2 role="installation">
108 <title>Installation of OpenSSH</title>
109
110 <para>
111 <application>OpenSSH</application> runs as two processes when connecting
112 to other computers. The first process is a privileged process and controls
113 the issuance of privileges as necessary. The second process communicates
114 with the network. Additional installation steps are necessary to set up
115 the proper environment, which are performed by issuing the following
116 commands as the <systemitem class="username">root</systemitem> user:
117 </para>
118
119<screen role="root"><userinput>install -v -m700 -d /var/lib/sshd &amp;&amp;
120chown -v root:sys /var/lib/sshd &amp;&amp;
121
122groupadd -g 50 sshd &amp;&amp;
123useradd -c 'sshd PrivSep' -d /var/lib/sshd -g sshd -s /bin/false -u 50 sshd</userinput></screen>
124
125 <para>
126 Install <application>OpenSSH</application> by running the following
127 commands:
128 </para>
129
130<screen><userinput>./configure --prefix=/usr \
131 --sysconfdir=/etc/ssh \
132 --with-md5-passwords \
133 --with-privsep-path=/var/lib/sshd &amp;&amp;
134make</userinput></screen>
135
136 <para>
137 The testsuite requires an installed copy of <command>scp</command> to
138 complete the multiplexing tests. To run the test suite, first copy the
139 <command>scp</command> program to
140 <filename class="directory">/usr/bin</filename>, making sure that you
141 back up any existing copy first.
142 </para>
143
144 <para>
145 To test the results, issue: <command>make tests</command>.
146 </para>
147
148<!-- commenting this, I get "all tests passed" [ ken ]
149 NB tests should be run as _user_ but the role in the comment is root
150
151 commenting [ bruce ]: There are a couple of tests that want root.
152 The log mentions that SUDO is not set. These skipped tests are
153 ignored and the end says 'all tests passed' even when not root
154
155 <para>
156 To run the test suite, issue the following commands:
157 </para>
158
159<screen role="root"><userinput>make tests 2&gt;&amp;1 | tee check.log
160grep FATAL check.log</userinput></screen>
161
162 <para>
163 If the above command produces no 'FATAL' errors, then proceed with the
164 installation, as the <systemitem class="username">root</systemitem> user:
165 </para>-->
166 <para>
167 Now, as the <systemitem class="username">root</systemitem> user:
168 </para>
169
170<screen role="root"><userinput>make install &amp;&amp;
171install -v -m755 contrib/ssh-copy-id /usr/bin &amp;&amp;
172install -v -m644 contrib/ssh-copy-id.1 /usr/share/man/man1 &amp;&amp;
173install -v -m755 -d /usr/share/doc/openssh-&openssh-version; &amp;&amp;
174install -v -m644 INSTALL LICENCE OVERVIEW README* /usr/share/doc/openssh-&openssh-version;</userinput></screen>
175 </sect2>
176
177 <sect2 role="commands">
178 <title>Command Explanations</title>
179
180 <para>
181 <parameter>--sysconfdir=/etc/ssh</parameter>: This prevents the
182 configuration files from being installed in
183 <filename class="directory">/usr/etc</filename>.
184 </para>
185
186 <para>
187 <parameter>--with-md5-passwords</parameter>: This enables the use of MD5
188 passwords.
189 </para>
190
191 <para>
192 <parameter>--with-pam</parameter>: This parameter enables
193 <application>Linux-PAM</application> support in the build.
194 </para>
195
196 <para>
197 <parameter>--with-xauth=/usr/bin/xauth</parameter>: Set the default
198 location for the <command>xauth</command> binary for X authentication.
199 Change the location if <command>xauth</command> will be installed to a
200 different path. This can also be controlled from
201 <filename>sshd_config</filename> with the XAuthLocation keyword. You can
202 omit this switch if <application>Xorg</application> is already installed.
203 </para>
204
205 <para>
206 <parameter>--with-kerberos5=/usr</parameter>: This option is used to
207 include Kerberos 5 support in the build.
208 </para>
209
210 <para>
211 <parameter>--with-libedit</parameter>: This option enables line editing
212 and history features for <command>sftp</command>.
213 </para>
214
215 </sect2>
216
217 <sect2 role="configuration">
218 <title>Configuring OpenSSH</title>
219
220 <sect3 id="openssh-config">
221 <title>Config Files</title>
222
223 <para>
224 <filename>~/.ssh/*</filename>,
225 <filename>/etc/ssh/ssh_config</filename>, and
226 <filename>/etc/ssh/sshd_config</filename>
227 </para>
228
229 <indexterm zone="openssh openssh-config">
230 <primary sortas="e-AA.ssh">~/.ssh/*</primary>
231 </indexterm>
232
233 <indexterm zone="openssh openssh-config">
234 <primary sortas="e-etc-ssh-ssh_config">/etc/ssh/ssh_config</primary>
235 </indexterm>
236
237 <indexterm zone="openssh openssh-config">
238 <primary sortas="e-etc-ssh-sshd_config">/etc/ssh/sshd_config</primary>
239 </indexterm>
240
241 <para>
242 There are no required changes to any of these files. However,
243 you may wish to view the
244 <filename class='directory'>/etc/ssh/</filename> files and make any
245 changes appropriate for the security of your system. One recommended
246 change is that you disable
247 <systemitem class='username'>root</systemitem> login via
248 <command>ssh</command>. Execute the following command as the
249 <systemitem class='username'>root</systemitem> user to disable
250 <systemitem class='username'>root</systemitem> login via
251 <command>ssh</command>:
252 </para>
253
254<screen role="root"><userinput>echo "PermitRootLogin no" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
255
256 <para>
257 If you want to be able to log in without typing in your password, first
258 create ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub with
259 <command>ssh-keygen</command> and then copy ~/.ssh/id_rsa.pub to
260 ~/.ssh/authorized_keys on the remote computer that you want to log into.
261 You'll need to change REMOTE_HOSTNAME for the hostname of the remote
262 computer and you'll also need to enter you password for the ssh command
263 to succeed:
264 </para>
265
266<screen><userinput>ssh-keygen &amp;&amp;
267public_key="$(cat ~/.ssh/id_rsa.pub)" &amp;&amp;
268ssh REMOTE_HOSTNAME "echo ${public_key} &gt;&gt; ~/.ssh/authorized_keys" &amp;&amp;
269unset public_key</userinput></screen>
270
271 <para>
272 Once you've got passwordless logins working it's actually more secure
273 than logging in with a password (as the private key is much longer than
274 most people's passwords). If you would like to now disable password
275 logins, as the <systemitem class="username">root</systemitem> user:
276 </para>
277
278
279<screen role="root"><userinput>echo "PasswordAuthentication no" >> /etc/ssh/sshd_config &amp;&amp;
280echo "ChallengeResponseAuthentication no" >> /etc/ssh/sshd_config</userinput></screen>
281
282 <para>
283 If you added <application>LinuxPAM</application> support and you want
284 ssh to use it then you will need to add a configuration file for
285 <application>sshd</application> and enable use of
286 <application>LinuxPAM</application>. Note, ssh only uses PAM to check
287 passwords, if you've disabled password logins these commands are not
288 needed. If you want to use PAM issue the following commands as the
289 <systemitem class='username'>root</systemitem> user:
290 </para>
291
292<screen role="root"><userinput>sed 's@d/login@d/sshd@g' /etc/pam.d/login &gt; /etc/pam.d/sshd &amp;&amp;
293chmod 644 /etc/pam.d/sshd &amp;&amp;
294echo "UsePAM yes" &gt;&gt; /etc/ssh/sshd_config</userinput></screen>
295
296 <para>
297 Additional configuration information can be found in the man
298 pages for <command>sshd</command>, <command>ssh</command> and
299 <command>ssh-agent</command>.
300 </para>
301 </sect3>
302
303 <sect3 id="openssh-init-systemd">
304 <title>Systemd Unit File</title>
305
306 <para>
307 The systemd-units package provides native unit files.
308 To start the SSH server at system boot, install the
309 systemd unit included in the <xref linkend="systemd-units"/>
310 package.as the
311 <systemitem class="username">root</systemitem> user:
312 </para>
313
314 <indexterm zone="openssh openssh-init-systemd">
315 <primary sortas="f-sshd">sshd</primary>
316 </indexterm>
317
318<screen role="root"><userinput>make install-sshd</userinput></screen>
319
320 <note>
321 <para>
322 Note that this package comes with two types of units: A service file and a socket file.
323 The service file will start sshd daemon once at boot and it will keep running until the
324 system shuts down. The socket file will make systemd listen to sshd port (Default 22, needs
325 to be edited for anything else) and will start sshd daemon when something tries to connect
326 to that port and stop the daemon when the connection is terminated. This is
327 called socket activation.
328
329 By default, the first method is used - sshd daemon is started at boot and stopped at shutdown.
330 If the socket method is desired, you need to run as the <systemitem class="username">root</systemitem> user:
331
332
333<screen role="root"><userinput>systemctl stop sshd &amp;&amp;
334systemctl disable sshd.service &amp;&amp;
335systemctl enable sshd.socket &amp;&amp;
336systemctl start sshd.socket</userinput></screen>
337
338 </para>
339 </note>
340 </sect3>
341
342 </sect2>
343
344 <sect2 role="content">
345 <title>Contents</title>
346
347 <segmentedlist>
348 <segtitle>Installed Programs</segtitle>
349 <segtitle>Installed Libraries</segtitle>
350 <segtitle>Installed Directories</segtitle>
351
352 <seglistitem>
353 <seg>
354 scp, sftp, sftp-server, slogin (symlink to ssh), ssh, sshd, ssh-add,
355 ssh-agent, ssh-copy-id, ssh-keygen, ssh-keyscan, ssh-keysign,
356 and ssh-pkcs11-helper
357 </seg>
358 <seg>
359 None
360 </seg>
361 <seg>
362 /etc/ssh,
363 /usr/libexec/openssh,
364 /usr/share/doc/openssh-&openssh-version;, and
365 /var/lib/sshd
366 </seg>
367 </seglistitem>
368 </segmentedlist>
369
370 <variablelist>
371 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
372 <?dbfo list-presentation="list"?>
373 <?dbhtml list-presentation="table"?>
374
375 <varlistentry id="scp">
376 <term><command>scp</command></term>
377 <listitem>
378 <para>
379 is a file copy program that acts like <command>rcp</command> except
380 it uses an encrypted protocol.
381 </para>
382 <indexterm zone="openssh scp">
383 <primary sortas="b-scp">scp</primary>
384 </indexterm>
385 </listitem>
386 </varlistentry>
387
388 <varlistentry id="sftp">
389 <term><command>sftp</command></term>
390 <listitem>
391 <para>
392 is an FTP-like program that works over the SSH1 and SSH2 protocols.
393 </para>
394 <indexterm zone="openssh sftp">
395 <primary sortas="b-sftp">sftp</primary>
396 </indexterm>
397 </listitem>
398 </varlistentry>
399
400 <varlistentry id="sftp-server">
401 <term><command>sftp-server</command></term>
402 <listitem>
403 <para>
404 is an SFTP server subsystem. This program is not normally called
405 directly by the user.
406 </para>
407 <indexterm zone="openssh sftp-server">
408 <primary sortas="b-sftp-server">sftp-server</primary>
409 </indexterm>
410 </listitem>
411 </varlistentry>
412
413 <varlistentry id="slogin">
414 <term><command>slogin</command></term>
415 <listitem>
416 <para>
417 is a symlink to <command>ssh</command>.
418 </para>
419 <indexterm zone="openssh slogin">
420 <primary sortas="b-slogin">slogin</primary>
421 </indexterm>
422 </listitem>
423 </varlistentry>
424
425 <varlistentry id="ssh">
426 <term><command>ssh</command></term>
427 <listitem>
428 <para>
429 is an <command>rlogin</command>/<command>rsh</command>-like client
430 program except it uses an encrypted protocol.
431 </para>
432 <indexterm zone="openssh ssh">
433 <primary sortas="b-ssh">ssh</primary>
434 </indexterm>
435 </listitem>
436 </varlistentry>
437
438 <varlistentry id="sshd">
439 <term><command>sshd</command></term>
440 <listitem>
441 <para>
442 is a daemon that listens for <command>ssh</command> login requests.
443 </para>
444 <indexterm zone="openssh sshd">
445 <primary sortas="b-sshd">sshd</primary>
446 </indexterm>
447 </listitem>
448 </varlistentry>
449
450 <varlistentry id="ssh-add">
451 <term><command>ssh-add</command></term>
452 <listitem>
453 <para>
454 is a tool which adds keys to the <command>ssh-agent</command>.
455 </para>
456 <indexterm zone="openssh ssh-add">
457 <primary sortas="b-ssh-add">ssh-add</primary>
458 </indexterm>
459 </listitem>
460 </varlistentry>
461
462 <varlistentry id="ssh-agent">
463 <term><command>ssh-agent</command></term>
464 <listitem>
465 <para>
466 is an authentication agent that can store private keys.
467 </para>
468 <indexterm zone="openssh ssh-agent">
469 <primary sortas="b-ssh-agent">ssh-agent</primary>
470 </indexterm>
471 </listitem>
472 </varlistentry>
473
474 <varlistentry id="ssh-copy-id">
475 <term><command>ssh-copy-id</command></term>
476 <listitem>
477 <para>
478 is a script that enables logins on remote machine using local keys.
479 </para>
480 <indexterm zone="openssh ssh-copy-id">
481 <primary sortas="b-ssh-copy-id">ssh-copy-id</primary>
482 </indexterm>
483 </listitem>
484 </varlistentry>
485
486 <varlistentry id="ssh-keygen">
487 <term><command>ssh-keygen</command></term>
488 <listitem>
489 <para>
490 is a key generation tool.
491 </para>
492 <indexterm zone="openssh ssh-keygen">
493 <primary sortas="b-ssh-keygen">ssh-keygen</primary>
494 </indexterm>
495 </listitem>
496 </varlistentry>
497
498 <varlistentry id="ssh-keyscan">
499 <term><command>ssh-keyscan</command></term>
500 <listitem>
501 <para>
502 is a utility for gathering public host keys from a number of hosts.
503 </para>
504 <indexterm zone="openssh ssh-keyscan">
505 <primary sortas="b-ssh-keyscan">ssh-keyscan</primary>
506 </indexterm>
507 </listitem>
508 </varlistentry>
509
510 <varlistentry id="ssh-keysign">
511 <term><command>ssh-keysign</command></term>
512 <listitem>
513 <para>
514 is used by <command>ssh</command> to access the local host keys and
515 generate the digital signature required during hostbased
516 authentication with SSH protocol version 2. This program is not
517 normally called directly by the user.
518 </para>
519 <indexterm zone="openssh ssh-keysign">
520 <primary sortas="b-ssh-keysign">ssh-keysign</primary>
521 </indexterm>
522 </listitem>
523 </varlistentry>
524
525 <varlistentry id="ssh-pkcs11-helper">
526 <term><command>ssh-pkcs11-helper</command></term>
527 <listitem>
528 <para>
529 is a <command>ssh-agent</command> helper program for PKCS#11 support.
530 </para>
531 <indexterm zone="openssh ssh-pkcs11-helper">
532 <primary sortas="b-ssh-pkcs11-helper">ssh-pkcs11-helper</primary>
533 </indexterm>
534 </listitem>
535 </varlistentry>
536
537 </variablelist>
538 </sect2>
539</sect1>
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