1999-11-15 22:02:27 +01:00
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OpenSSH is almost completely compatible with the commercial SSH 1.2.x.
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There are, however, a few exceptions that you will need to bear in
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mind while upgrading:
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1. OpenSSH does not support any patented transport algorithms.
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Only 3DES and Blowfish can be selected. This difference may manifest
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itself in the ssh command refusing to read its config files.
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Solution: Edit /etc/ssh/ssh_config and select a different "Cipher"
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option ("3des" or "blowfish").
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2. Old versions of commercial SSH encrypt host keys with IDEA
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The old versions of SSH used a patented algorithm to encrypt their
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/etc/ssh/ssh_host_key
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This problem will manifest as sshd not being able to read its host
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key.
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Solution: You will need to run the *commercial* version of ssh-keygen
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on the host's private key:
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ssh-keygen -u /etc/ssh/ssh_host_key
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3. Incompatible changes to sshd_config format.
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OpenSSH extends the sshd_config file format in a number of ways. There
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is currently one change which is incompatible with the old.
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Commercial SSH controlled logging using the "QuietMode" and
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"FascistLogging" directives. OpenSSH introduces a more general set of
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logging options "SyslogFacility" and "LogLevel". See the sshd manual
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page for details.
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1999-11-25 03:50:10 +01:00
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4. Warning messages about key lengths
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Commercial SSH's ssh-keygen program contained a bug which caused it to
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occasionally generate RSA keys which had their Most Significant Bit
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(MSB) unset. Such keys were advertised as being full-length, but are
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actually only half as secure.
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OpenSSH will print warning messages when it encounters such keys. To
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rid yourself of these message, edit you known_hosts files and replace
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the incorrect key length (usually "1024") with the correct key length
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(usually "1023").
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1999-12-26 04:04:33 +01:00
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5. Spurious PAM authentication messages in logfiles
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OpenSSH will generate spurious authentication failures at every login,
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similar to "authentication failure; (uid=0) -> root for sshd service".
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These are generated because OpenSSH first tries to determine whether a
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user needs authentication to login (e.g. empty password). Unfortunatly
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PAM likes to log all authentication events, this one included.
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