rssh

Rssh is a restricted shell that works efficiently with OpenSSH. It offers limited access to only scp and/or sftp. Recently, the rssh project integrated support for rdist, rsync, and cvs. Rssh helps in cases when a user wants to restrict server access only to file-copying via scp, without providing shell access. The best part of rssh is that it is written to work with OpenSSH, but it also supports other SSH implementations. Additionally, rssh is Linux-based; however, it can compile and function on any POSIX.2-compliant system.

This software is verified on operating systems such as a wide range of Linux distributions (IA32 and IA64 hardware), Compaq Tru64 Unix, Solaris 2.x - 8, AIX 5.1, HP/UX 11.00 (PA-RISC), HP/UX 11.22 (IA64), and Irix 6.5. Unfortunately, it may not work on most of the *BSDs or OS X, lacking the wordexp() function, which rssh employs for command-line argument expansion.

However, Jacques A. Vidrine reported that FreeBSD 5.0 now has the wordexp() function, indicating that rssh compiles cleanly on it, although he has not tested it. Moreover, users can work around the absence of the wordexp() function in a BSD system by compiling wordexp.c manually and linking it against other .o files. Users should send complete configure output and any compilation errors generated if they have an issue in compiling or installing rssh software on their favorite platform.

The newest release of rssh fixes a design flaw in rssh_chroot_helper that allowed local users with full shell access to gain root privileges. In conclusion, rssh provides a fundamental level of access restriction, allowing only the essential functionality needed by users, thus ensuring the security of the server.