OpenSSH is a complete implementation of the SSH protocol (version 2) for secure remote login, command execution and file transfer. It includes a client ssh and server sshd, file transfer utilities scp and sftp as well as tools for key generation (ssh-keygen), run-time key storage (ssh-agent) and a number of supporting programs.
This is a port of OpenBSD's OpenSSH to most Unix-like operating systems, including Linux, OS X and Cygwin. Portable OpenSSH polyfills OpenBSD APIs that are not available elsewhere, adds sshd sandboxing for more operating systems and includes support for OS-native authentication and auditing (e.g. using PAM).
This implementation of OpenSSH has been modified to provide additional security via the Qrypt Key Generation SDK. During KEX negotiation, the Qrypt SDK will generate an additional quantum-secure secret to be prepended to the session key hash inputs. Any conventional KEX algorithm can be enhanced by Qrypt security; a Qrypt-secured algorithm can be identified by the @Qrypt.com suffix.
Install the QryptSecurityC SDK by copying the include and lib folders to a directory that is accessible to PATH and Pkg-Config, such as /usr/, /usr/local/, or a user-defined path defined by environment variables. Once QryptSecurityC is installed as described, follow the "Building from Git" build steps as normal.
To enable Qrypt, pass a valid keygen token from the Qrypt Portal to ssh, sshd, or sftp using the QryptToken option:
- Export token:
export TOKEN="my token" - SSH Server:
sshd -o QryptToken=$TOKEN - SSH Client:
ssh -o QryptToken=$TOKEN sshuser@127.0.0.1
The official documentation for OpenSSH are the man pages for each tool:
Stable release tarballs are available from a number of download mirrors. We recommend the use of a stable release for most users. Please read the release notes for details of recent changes and potential incompatibilities.
Portable OpenSSH is built using autoconf and make. It requires a working C compiler, standard library and headers.
libcrypto from either LibreSSL or OpenSSL may also be used. OpenSSH may be built without either of these, but the resulting binaries will have only a subset of the cryptographic algorithms normally available.
zlib is optional; without it transport compression is not supported.
FIDO security token support needs libfido2 and its dependencies and will be enabled automatically if they are found.
In addition, certain platforms and build-time options may require additional dependencies; see README.platform for details about your platform.
Releases include a pre-built copy of the configure script and may be built using:
tar zxvf openssh-X.YpZ.tar.gz
cd openssh
./configure # [options]
make && make tests
See the Build-time Customisation section below for configure options. If you plan on installing OpenSSH to your system, then you will usually want to specify destination paths.
If building from git, you'll need autoconf installed to build the configure script. The following commands will check out and build portable OpenSSH from git:
git clone https://github.com/openssh/openssh-portable # or https://anongit.mindrot.org/openssh.git
cd openssh-portable
autoreconf
./configure
make && make tests
There are many build-time customisation options available. All Autoconf destination path flags (e.g. --prefix) are supported (and are usually required if you want to install OpenSSH).
For a full list of available flags, run ./configure --help but a few of the more frequently-used ones are described below. Some of these flags will require additional libraries and/or headers be installed.
| Flag | Meaning |
|---|---|
--with-pam |
Enable PAM support. OpenPAM, Linux PAM and Solaris PAM are supported. |
--with-libedit |
Enable libedit support for sftp. |
--with-kerberos5 |
Enable Kerberos/GSSAPI support. Both Heimdal and MIT Kerberos implementations are supported. |
--with-selinux |
Enable SELinux support. |
Portable OpenSSH development is discussed on the openssh-unix-dev mailing list (archive mirror). Bugs and feature requests are tracked on our Bugzilla.
Non-security bugs may be reported to the developers via Bugzilla or via the mailing list above. Security bugs should be reported to openssh@openssh.com.