This is Dropbear, a smallish SSH 2 server and client.

INSTALL has compilation instructions.

MULTI has instructions on making a multi-purpose binary (ie a single binary
which performs multiple tasks, to save disk space)

SMALL has some tips on creating small binaries.

See TODO for a few of the things I know need looking at, and please contact
me if you have any questions/bugs found/features/ideas/comments etc :)

Matt Johnston
[email protected]

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Public key auth:

You can use ~/.ssh/authorized_keys in the same way as with OpenSSH, just put
the key entries in that file. They should be of the form:

ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEAwVa6M6cGVmUcLl2cFzkxEoJd06Ub4bVDsYrWvXhvUV+ZAM9uGuewZBDoAqNKJxoIn0Hyd0Nk/yU99UVv6NWV/5YSHtnf35LKds56j7cuzoQpFIdjNwdxAN0PCET/MG8qyskG/2IE2DPNIaJ3Wy+Ws4IZEgdJgPlTYUBWWtCWOGc= someone@hostname

You must make sure that ~/.ssh, and the key file, are only writable by the
user.

NOTE: Dropbear ignores authorized_keys options such as those described in the
OpenSSH sshd manpage, and will not allow a login for these keys. 

To run the server, you need to generate server keys, this is one-off:
./dropbearkey -t rsa -f dropbear_rsa_host_key
./dropbearkey -t dss -f dropbear_dss_host_key

or alternatively convert OpenSSH keys to Dropbear:
./dropbearconvert openssh dropbear /etc/ssh/ssh_host_dsa_key dropbear_dss_host_key

And you can now run the server.
./dropbear

or './dropbear -h' to get options.

If the server is run as non-root, you most likely won't be able to allocate a
pty, and you cannot login as any user other than that running the daemon
(obviously). Shadow passwords will also be unusable as non-root.

The Dropbear distribution includes a standalone version of OpenSSH's scp
program. You can compile it with "make scp", you may want to change the path
of the ssh binary, specified near the top of the scp.c file. By default
the progress meter isn't compiled in to save space, you can enable it with
"make scp-progress".