From e8dfed79866a4e16bbd5675c463a95e1e0e0ab6f Mon Sep 17 00:00:00 2001 From: tekkub Date: Thu, 3 Sep 2009 18:22:13 -0600 Subject: New guide for ssh-agent, don't tell people to make passphrase-less keys --- ...2009-09-03-working-with-key-passphrases.textile | 100 +++++++++++++++++++++ 1 file changed, 100 insertions(+) create mode 100644 _posts/2009-09-03-working-with-key-passphrases.textile (limited to '_posts/2009-09-03-working-with-key-passphrases.textile') diff --git a/_posts/2009-09-03-working-with-key-passphrases.textile b/_posts/2009-09-03-working-with-key-passphrases.textile new file mode 100644 index 0000000..07c6aa3 --- /dev/null +++ b/_posts/2009-09-03-working-with-key-passphrases.textile @@ -0,0 +1,100 @@ +--- +layout: default +title: Working with SSH key passphrases +description: SSH key passphrases, why you should use them, and how to avoid re-entering them +categories: windows mac setup +main_category: setup +--- + +This guide will step you through the process of securing your ssh keys while avoiding re-entry of your passphrase every time you use the key. + +h2. Why do I need a passphrase? + +Passwords aren't very secure, you already know this. If you use one that's easy to remember, it's easier to guess or brute-force. If you use one that's random it's hard to remember, and thus you're more inclined to write the password down. Both of these are Very Bad Things™. This is why you're using ssh keys. + +But using a key without a passphrase is basically the same as writing down that random password in a file on your computer. Anyone who gains access to your drive has gained access to every system you use that key with. This is also a Very Bad Thing™. The solution is obvious, add a passphrase. + +h3. But I don't want to enter a long passphrase every time I use the key! + +Neither do I! Thankfully, there's a nifty little tool called @ssh-agent@ that can save your passphrase securely so you don't have to re-enter it. If you're on OSX Leopard or later your keys can be saved in the system's keychain to make your life even easier. + +h2. Adding or changing a passphrase + +Passphrases can be added to an existing key or changed without regenerating the keypair very easily: + +
$ ssh-keygen -p
+Enter file in which the key is (/Users/tekkub/.ssh/id_rsa):
+Key has comment '/Users/tekkub/.ssh/id_rsa'
+Enter new passphrase (empty for no passphrase):
+Enter same passphrase again:
+Your identification has been saved with the new passphrase.
+ +If your key already has a passphrase, you will be prompted to enter it before you can change to a new passphrase. + +h2. Auto-launching ssh-agent on msysgit + +You can run @ssh-agent@ automatically when you open bash by adding the following to your @~/.profile@ or @~/.bashrc@ file: + +
SSH_ENV="$HOME/.ssh/environment"
+
+function start_agent {
+  echo "Initializing new SSH agent..."
+  /usr/bin/ssh-agent | sed 's/^echo/#echo/' > "${SSH_ENV}"
+  echo succeeded
+  chmod 600 "${SSH_ENV}"
+  . "${SSH_ENV}" > /dev/null
+  /usr/bin/ssh-add;
+}
+
+# Source SSH settings, if applicable
+if [ -f "${SSH_ENV}" ]; then
+  . "${SSH_ENV}" > /dev/null
+  #ps ${SSH_AGENT_PID} doesn't work under cywgin
+  ps -ef | grep ${SSH_AGENT_PID} | grep ssh-agent$ > /dev/null || {
+    start_agent;
+  }
+else
+  start_agent;
+fi
+ +p(. *Note:* If you don't use the default key names, or store your keys in a different path, you will need to add the path to the @/usr/bin/ssh-add@ line so that ssh knows where to find your key. + +Now when you first run git bash, you will be prompted for your passphrase: + +
Initializing new SSH agent...
+succeeded
+Enter passphrase for /c/Users/Tekkub/.ssh/id_rsa:
+Identity added: /c/Users/Tekkub/.ssh/id_rsa (/c/Users/Tekkub/.ssh/id_rsa)
+Welcome to Git (version 1.6.0.2-preview20080923)
+
+
+Run 'git help git' to display the help index.
+Run 'git help ' to display help for specific commands.
+[Tekkub@KAKU: ~ master]$
+ +The process will continue to run until you log out, shutdown or kill ssh-agent. To kill the process, find it's PID with @ps@ then call @kill @: + +
[Tekkub@KAKU: ~ master]$ ps
+        PID    PPID    PGID     WINPID  TTY  UID    STIME COMMAND
+       3796       1    3796       3796    ?  500 18:07:43 /bin/ssh-agent
+       2780       1    2780       2780  con  500 18:10:50 /bin/bash
+       3400    2780    3400        784  con  500 18:13:31 /bin/ps
+[Tekkub@KAKU: ~ master]$ kill 3796
+ +p(. This section was written with help from "this post":http://www.cygwin.com/ml/cygwin/2001-06/msg00537.html. + +h2. Mac OSX Keychain + +If you are on OSX Leopard or later, ssh-agent is run automatically for you. It will also integrate with the keychain, so you can unlock your keys with it. This has some major advantages over a command-line based setup like protecting your input from being copied or spied upon by universal access or low-level keyboard routines. + +The default key files (@.ssh/id_rsa@, @.ssh/id_dsa@ and @.ssh/identity@) should be handled automatically. If you have a key with a different name, you can add it with @ssh-add path/to/my_key@ + +p(. _Make sure that you're using the default OS X ssh-add command and not one installed by macports or some other external source._ + +When you first try to use the key you will be prompted to enter your passphrase: + +!/images/SecurityAgent.jpg(Keychain prompt)! + +If you choose to save the passphrase with your keychain, you won't have to enter it again. Instead you'll simply need to unlock your keychain. + +p(. This section was written with help from "this guide":http://www.dribin.org/dave/blog/archives/2007/11/28/ssh_agent_leopard/. If you would like to use more paranoid keychain settings like locking after sleep, check out "this guide":http://www.dribin.org/dave/blog/archives/2007/11/28/securing_ssh_agent/. -- cgit v1.3.1