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Revision 1.8 - (hide annotations) (download) (as text)
Sun Mar 11 19:44:22 2012 UTC (2 years, 9 months ago) by robbat2
Branch: MAIN
Changes since 1.7: +6 -2 lines
File MIME type: application/xml
Add link to official SSH fingerprints, and clarify that the fingerprint on the page is from the output of ssh-keygen.

1 klieber 1.1 <?xml version='1.0' encoding="UTF-8"?>
2     <?xml-stylesheet href="/xsl/guide.xsl" type="text/xsl"?>
3     <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4    
5 nightmorph 1.6 <guide>
6 klieber 1.1 <title>SSH access to cvs.gentoo.org</title>
7 nightmorph 1.6
8 klieber 1.1 <author title="Author">
9 nightmorph 1.6 <mail link="swift"/>
10 klieber 1.1 </author>
11 robbat2 1.4 <author title="Author">
12 nightmorph 1.6 <mail link="robbat2"/>
13     </author>
14 antarus 1.7 <author title="Author">
15     <mail link="antarus"/>
16     </author>
17 nightmorph 1.6 <author title="Editor">
18     <mail link="nightmorph"/>
19 robbat2 1.4 </author>
20 nightmorph 1.6
21 klieber 1.1 <abstract>
22     This mini-guide explains on how to create and use ssh-keys, especially
23     for use on cvs.gentoo.org.
24     </abstract>
25 nightmorph 1.6
26 antarus 1.7 <version>1.3</version>
27     <date>2011-10-14</date>
28 klieber 1.1
29     <chapter>
30     <title>SSH keys</title>
31     <section>
32 antarus 1.7 <title>Key Handling</title>
33     <body>
34     <p>
35     Your SSH keypair authenticates you to Gentoo Infrastructure. Properly
36     handling these keys is vital to keeping our machines safe. Please try to
37     follow these guidelines.
38     </p>
39    
40     <ul>
41 robbat2 1.8 <li>Place your private keys <b>only</b> on machines you trust. This means only you have root
42 antarus 1.7 on these machines and they are not shared with other users.
43     </li>
44     <li>Do not trust Gentoo Infrastructure. Do not place copies of your keys
45     on Gentoo machines (like dev.gentoo.org.) You may forward your SSH agent
46     through Gentoo managed machines if they are configured to allow users to
47     agent forward (more on forwarding later.)
48     </li>
49     <li>Encrypt your keys with a strong passphrase. If you have trouble making
50     a passphrase try emerge pwgen; pwgen -sB 25
51     </li>
52     <li>Do not access Gentoo infrastructure from untrusted machines such as business
53     kiosks at hotels, internet cafes, or machines at computer conferences. Many of these machines
54     are infected with malware.</li>
55     <li>If you believe your keys were compromised, contact infrastructure immediately.
56     You can do this via #gentoo-infra on irc.freenode.net or by emailing incidents@gentoo.org.
57     </li>
58 robbat2 1.8 <li>Official hostkey fingerprints for Gentoo Infrastructure servers are
59     available on the <uri link="/proj/en/infrastructure/server-specs"> server
60     specifications </uri> page.
61     </li>
62 antarus 1.7 </ul>
63     </body>
64     </section>
65     <section>
66 klieber 1.1 <title>Creating the SSH keys</title>
67     <body>
68 nightmorph 1.6
69 klieber 1.1 <p>
70     First of all, be physically logged on to your own computer. Make sure
71     that no-one will see you typing stuff in, since we are going to type in
72 klieber 1.2 passphrases and such. So get your pepperspray and fight all untrusted
73 klieber 1.1 entities until you are home alone.
74     </p>
75 nightmorph 1.6
76 klieber 1.1 <p>
77     Now we are going to create our ssh keys, DSA keys to be exact. Log onto
78     your computer as the user that you are going to be using when you want
79     to access cvs.gentoo.org. Then issue <c>ssh-keygen -t dsa</c>:
80     </p>
81 nightmorph 1.6
82     <pre caption="Creating SSH keys">
83 klieber 1.1 $ <i>ssh-keygen -t dsa</i>
84     Generating public/private dsa key pair.
85     Enter file in which to save the key (/home/temp/.ssh/id_dsa): <comment>(Press enter)</comment>
86     Created directory '/home/temp/.ssh'.
87 klieber 1.2 Enter passphrase (empty for no passphrase): <comment>(Enter your passphrase)</comment>
88     Enter same passphrase again: <comment>(Enter your passphrase again)</comment>
89 klieber 1.1 Your identification has been saved in /home/temp/.ssh/id_dsa.
90     Your public key has been saved in /home/temp/.ssh/id_dsa.pub.
91     The key fingerprint is:
92 robbat2 1.8 85:35:81:a0:87:56:78:a2:da:53:6c:63:32:d1:34:48 user@examplehost <comment>This is the fingerprint of your new key</comment>
93 klieber 1.1 </pre>
94 nightmorph 1.6
95 klieber 1.1 <note>
96     Please be sure to set a strong passphrase on your private key. Ideally,
97 antarus 1.7 this passphrase should be at least eight characters and contain a mixture of
98 klieber 1.1 letters, numbers and symbols.
99     </note>
100 nightmorph 1.6
101 antarus 1.7 <warn>
102     Do not set an empty passphrase on your ssh key. If infra finds out this is the
103     case; your account will be suspended.
104     </warn>
105 nightmorph 1.6
106     <pre caption="Created files">
107 klieber 1.1 # <i>ls ~/.ssh</i>
108     id_dsa id_dsa.pub
109     </pre>
110 nightmorph 1.6
111 klieber 1.1 <p>
112 antarus 1.7 You may have more files than this, but the two files listed above
113 klieber 1.1 are the ones that are really important.
114     </p>
115 nightmorph 1.6
116 klieber 1.1 <p>
117     The first file, <path>id_dsa</path>, is your <e>private</e> key. Don't
118 antarus 1.7 give this to anyone; never decrypt it on an untrusted machine. Gentoo Staff
119     will never ask you for a copy of your private key.
120 klieber 1.1 </p>
121 nightmorph 1.6
122 klieber 1.1 <warn>
123 antarus 1.7 Be very careful which machines you put your private key on. If you have
124     several (<e>trusted!</e>) hosts from which you want to connect to
125     cvs.gentoo.org, you should copy <path>id_dsa</path> to the
126     <path>~/.ssh</path> directories on those hosts. Trusted machines are machines
127     that only you have root on; these machines are not shared with other users.
128 klieber 1.1 </warn>
129 nightmorph 1.6
130 klieber 1.1 <p>
131     The second file, <path>id_dsa.pub</path>, is your <e>public</e> key.
132     Distribute this file amongst all hosts that you want to be able to
133     access through SSH pubkey authentification. This file should be appended
134     to <path>~/.ssh/authorized_keys</path> on those remote hosts. Also add it
135     to your local host so you can connect to that one too if you have several
136     boxes.
137     </p>
138 nightmorph 1.6
139     <pre caption="Adding the SSH key to the box">
140 klieber 1.1 $ <i>cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys</i>
141     </pre>
142 nightmorph 1.6
143 klieber 1.1 </body>
144     </section>
145     <section>
146 nightmorph 1.6 <title>
147     Installing your public key on a machine using LDAP authentication for SSH
148     </title>
149 robbat2 1.4 <body>
150 nightmorph 1.6
151     <note>
152     If you are a new developer, your recruiter will put your first SSH key into
153     LDAP, so that you can login. You can then add any additional SSH keys yourself
154     using the following procedure.
155     </note>
156    
157 antarus 1.7 <note>
158 robbat2 1.4 For most of the Gentoo infrastructure, we use LDAP to distribute user
159     information including SSH public keys. On these machines,
160     <path>~/.ssh/authorized_keys</path> should generally not contain your key.
161 antarus 1.7 </note>
162 nightmorph 1.6
163 robbat2 1.4 <p>
164 antarus 1.7 You should place your public key into LDAP, using
165 robbat2 1.4 <path>perl_ldap</path>, or <path>ldapmodify</path> directly.
166     The Infrastructure <uri link="/proj/en/infrastructure/ldap.xml">LDAP
167     guide</uri> describes this in more detail.
168     </p>
169 nightmorph 1.6
170     <pre caption="Adding the SSH key with perl_ldap on dev.gentoo.org">
171 robbat2 1.4 $ <i>perl_ldap -b user -C sshPublicKey "$(cat ~/.ssh/id_dsa.pub)" &lt;username&gt;</i>
172     </pre>
173 nightmorph 1.6
174     <warn>
175     Each <path>sshPublicKey</path> attribute must contain exactly one public key. If you have multiple public keys, you must have multiple attributes!
176     </warn>
177    
178 robbat2 1.4 </body>
179     </section>
180     <section>
181 klieber 1.1 <title>Using keychain</title>
182     <body>
183 nightmorph 1.6
184 klieber 1.1 <p>
185     Every time you want to log on to a remote host using SSH public key
186 klieber 1.2 authentification, you will be asked to enter your passphrase. As much as
187 nightmorph 1.6 everybody likes typing, too much is sometimes too much. Luckily, there is
188     <c>keychain</c> to the rescue. There is an document on this one <uri
189     link="/doc/en/keychain-guide.xml">here</uri>, but I'll give you a quick
190     introduction.
191 klieber 1.1 </p>
192 nightmorph 1.6
193 klieber 1.1 <p>
194     First, install <c>keychain</c>:
195     </p>
196 nightmorph 1.6
197     <pre caption="Installing keychain">
198 klieber 1.1 # <i>emerge keychain</i>
199     </pre>
200 nightmorph 1.6
201 klieber 1.1 <p>
202 nightmorph 1.6 Now have keychain load up your private ssh key when you log on to your local
203     box. To do so, add the following to <path>~/.bash_profile</path>. Again, this
204     should be done on your <e>local</e> machine where you work at the Gentoo CVS.
205 klieber 1.1 </p>
206 nightmorph 1.6
207 antarus 1.7 <warn>
208     <b>NEVER</b> run keychain or decrypt your private key on an untrusted host.
209     </warn>
210    
211 nightmorph 1.6 <pre caption="Add this to .bash_profile">
212 klieber 1.1 keychain ~/.ssh/id_dsa
213     . .keychain/<comment>hostname</comment>-sh
214     </pre>
215 nightmorph 1.6
216 klieber 1.1 <p>
217     Be sure to substitute <c>hostname</c> with your hostname.
218     </p>
219 nightmorph 1.6
220 klieber 1.1 </body>
221     </section>
222     </chapter>
223     </guide>

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