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]

In the absence of detailed documentation, some notes follow:

Server 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. Beware of editors that split the key into multiple lines.

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

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Client public key auth:

Dropbear can do public key auth as a client, but you will have to convert OpenSSH style keys to Dropbear format, or use dropbearkey to create them.

If you have an OpenSSH-style private key ~/.ssh/id_rsa, you need to do:

dropbearconvert openssh dropbear ~/.ssh/id_rsa ~/.ssh/id_rsa.db dbclient -i ~/.ssh/id_rsa.db

Currently encrypted keys aren't supported, neither is agent forwarding. At some stage both hopefully will be.

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If you want to get the public-key portion of a Dropbear private key, look at dropbearkey's '-y' option.

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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

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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.

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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 by _PATH_SSH_PROGRAM in options.h . By default the progress meter isn't compiled in to save space, you can enable it by adding 'SCPPROGRESS=1' to the make commandline.