Dropbear SSH

Dropbear is a relatively small SSH server and client. It runs on a variety of POSIX-based platforms. Dropbear is open source software, distributed under a MIT-style license. Dropbear is particularly useful for "embedded"-type Linux (or other Unix) systems, such as wireless routers.

If you want to be notified of new releases, or for general discussion of Dropbear, you can subscribe to the relatively low volume mailing list.

Security Update Dropbear 2017.75 fixes security issues, most users are advised to upgrade

Features

• A small memory footprint suitable for memory-constrained environments – Dropbear can compile to a 110kB statically linked binary with uClibc on x86 (only minimal options selected)
• Dropbear server implements X11 forwarding, and authentication-agent forwarding for OpenSSH clients
• Can run from inetd or standalone
• Compatible with OpenSSH ~/.ssh/authorized_keys public key authentication
• The server, client, keygen, and key converter can be compiled into a single binary (like busybox)
• Features can easily be disabled when compiling to save space
• Multi-hop mode uses SSH TCP forwarding to tunnel through multiple SSH hosts in a single command. dbclient user1@hop1,user2@hop2,destination

Platforms

• Linux – standard distributions, uClibc >=0.9.17, dietlibc, musl libc, uClinux from inetd
• Mac OS X (compile with PAM support)
• FreeBSD, NetBSD and OpenBSD
• Solaris – tested v8 x86 and v9 Sparc
• IRIX 6.5 (with /dev/urandom, or prngd should work)
• Tru64 5.1 (using prngd for entropy)
• AIX 4.3.3 (with gcc and Linux Affinity Toolkit), AIX 5.2 (with /dev/urandom).
• HPUX 11.00 (+prngd), TCP forwarding doesn't work
• Cygwin – tested 1.5.19 on Windows XP

It shouldn't be hard to get it to work on other POSIX platforms, it is mostly a case of setting up the configure and Makefile settings.

Distributions

• LEAF Bering uClibc – a small Linux firewall/network appliance distribution.
• OpenWRT – a very nice distro for many wireless routers.
• BuildRoot – an easy way to build a toolchain and programs for a uClibc Linux system
• sabotage – a radical and experimental distribution based on musl libc and busybox
• Net::Dropbear - A Perl module that allows using Dropbear server inside a Perl program
• SSHDroid is another SSH server UI for Android
• Gentoo
• Fedora
• CirrOS a tiny cloud guest
• cam.ly wireless security cameras.
• FREESCO is is a single floppy NAT/firewall router/server.
• Tomato Firmware for wrt54g and similar.
• gumstix – tiny embedded Linux boards
• PSPSSH is a port to run on PlayStation Portables.
• Debian has outdated packages available.
• Ubuntu (outdated like Debian)
• Maemo packages – for Nokia N800/N810. Server-only or Client-only packages are available.
• FreeWRT – a Linux distro for various embedded devices (particularly wireless routers).
• DD-WRT is another Linux router distribution including Dropbear.
• OpenMoko includes Dropbear in the default install.
• VMware ESXi – a hypervisor OS for virtualisation.
• Bent Linux – a uClibc based Linux distribution, statically linked cpio.bz2 packages (should work on any distro)
• NetBSD Packages Collection
• FreeBSD Ports
• fli4l – a one-disk-router Linux distribution
• Ångström - the successor to OpenZaurus, for Sharp Zaurus handhelds.
• floppyfw – a single floppy firewall Linux distribution
• ttylinux – Linux to fit in 4 megabytes of disk space and run on 386es, as an internet terminal
• BrazilFW – a fork to continue Coyote Linux floppy firewall
• Trinux – a lightweight Linux security toolkit
• T2 System Development Environment – a build system for distributions
• LyconSys make various industrial routers that run Dropbear.
• SliTaz is a small Linux distro that includes Dropbear.
• Dreambox linux-based DVB recorder has Dropbear on the default firmware.
• US Robotics USR9108 DSL/wireless gateway uses Dropbear.
• Graterlia OS is a Linux distribution for satellite receivers
• Slackware package
• kboot – a proof-of-concept Linux boot loader.
• Motorola a780/e680/e680i phones (login or bugmenot required)
• Zipit Z2 shell environment for a handheld wifi messenger.

Please let me know of any others which should be added to this list.

Acknowledgements

The cryptographic code utilises Tom St Denis's LibTomCrypt, and uses his LibTomMath library for the bignum parts. PTY handling code is taken from OpenSSH (from Tatu Ylönen's original ssh), login recording (utmp/wtmp) code is from OpenSSH by Andre Lucas, and some implementation details were gleaned from PuTTY. Numerous people have contributed patches and bug reports, see CHANGES. Particular thanks go to Mihnea Stoenescu for his work on the client portion.

Thanks to PCextreme for hosting the mirror server with Raspberry Pi colocation.

Contact

If you have any comments, bugs you've found, or features you'd like, feel free to email me.
My email address is matt@ucc.asn.au
Matt Johnston

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