freebsd-dev/crypto/openssh/README.md

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# Portable OpenSSH
[![C/C++ CI](https://github.com/openssh/openssh-portable/actions/workflows/c-cpp.yml/badge.svg)](https://github.com/openssh/openssh-portable/actions/workflows/c-cpp.yml)
[![Fuzzing Status](https://oss-fuzz-build-logs.storage.googleapis.com/badges/openssh.svg)](https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:openssh)
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](https://openssh.com) 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).
## Documentation
The official documentation for OpenSSH are the man pages for each tool:
* [ssh(1)](https://man.openbsd.org/ssh.1)
* [sshd(8)](https://man.openbsd.org/sshd.8)
* [ssh-keygen(1)](https://man.openbsd.org/ssh-keygen.1)
* [ssh-agent(1)](https://man.openbsd.org/ssh-agent.1)
* [scp(1)](https://man.openbsd.org/scp.1)
* [sftp(1)](https://man.openbsd.org/sftp.1)
* [ssh-keyscan(8)](https://man.openbsd.org/ssh-keyscan.8)
* [sftp-server(8)](https://man.openbsd.org/sftp-server.8)
## Stable Releases
Stable release tarballs are available from a number of [download mirrors](https://www.openssh.com/portable.html#downloads). We recommend the use of a stable release for most users. Please read the [release notes](https://www.openssh.com/releasenotes.html) for details of recent changes and potential incompatibilities.
## Building Portable OpenSSH
### Dependencies
Portable OpenSSH is built using autoconf and make. It requires a working C compiler, standard library and headers.
ssh: update to OpenSSH 9.1p1 Release notes are available at https://www.openssh.com/txt/release-9.1 9.1 contains fixes for three minor memory safety problems; these have lready been merged to the copy of OpenSSH 9.0 that is in the FreeBSD base system. Some highlights copied from the release notes: Potentially-incompatible changes -------------------------------- * ssh(1), sshd(8): SetEnv directives in ssh_config and sshd_config are now first-match-wins to match other directives. Previously if an environment variable was multiply specified the last set value would have been used. bz3438 * ssh-keygen(8): ssh-keygen -A (generate all default host key types) will no longer generate DSA keys, as these are insecure and have not been used by default for some years. New features ------------ * ssh(1), sshd(8): add a RequiredRSASize directive to set a minimum RSA key length. Keys below this length will be ignored for user authentication and for host authentication in sshd(8). * sftp-server(8): add a "users-groups-by-id@openssh.com" extension request that allows the client to obtain user/group names that correspond to a set of uids/gids. * sftp(1): use "users-groups-by-id@openssh.com" sftp-server extension (when available) to fill in user/group names for directory listings. * sftp-server(8): support the "home-directory" extension request defined in draft-ietf-secsh-filexfer-extensions-00. This overlaps a bit with the existing "expand-path@openssh.com", but some other clients support it. * ssh-keygen(1), sshd(8): allow certificate validity intervals, sshsig verification times and authorized_keys expiry-time options to accept dates in the UTC time zone in addition to the default of interpreting them in the system time zone. YYYYMMDD and YYMMDDHHMM[SS] dates/times will be interpreted as UTC if suffixed with a 'Z' character. Also allow certificate validity intervals to be specified in raw seconds-since-epoch as hex value, e.g. -V 0x1234:0x4567890. This is intended for use by regress tests and other tools that call ssh-keygen as part of a CA workflow. bz3468 * sftp(1): allow arguments to the sftp -D option, e.g. sftp -D "/usr/libexec/sftp-server -el debug3" * ssh-keygen(1): allow the existing -U (use agent) flag to work with "-Y sign" operations, where it will be interpreted to require that the private keys is hosted in an agent; bz3429 MFC after: 2 weeks Relnotes: Yes Sponsored by: The FreeBSD Foundation
2022-10-19 14:27:11 +00:00
``libcrypto`` from either [LibreSSL](https://www.libressl.org/) or [OpenSSL](https://www.openssl.org) 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](https://www.zlib.net/) is optional; without it transport compression is not supported.
ssh: update to OpenSSH 9.1p1 Release notes are available at https://www.openssh.com/txt/release-9.1 9.1 contains fixes for three minor memory safety problems; these have lready been merged to the copy of OpenSSH 9.0 that is in the FreeBSD base system. Some highlights copied from the release notes: Potentially-incompatible changes -------------------------------- * ssh(1), sshd(8): SetEnv directives in ssh_config and sshd_config are now first-match-wins to match other directives. Previously if an environment variable was multiply specified the last set value would have been used. bz3438 * ssh-keygen(8): ssh-keygen -A (generate all default host key types) will no longer generate DSA keys, as these are insecure and have not been used by default for some years. New features ------------ * ssh(1), sshd(8): add a RequiredRSASize directive to set a minimum RSA key length. Keys below this length will be ignored for user authentication and for host authentication in sshd(8). * sftp-server(8): add a "users-groups-by-id@openssh.com" extension request that allows the client to obtain user/group names that correspond to a set of uids/gids. * sftp(1): use "users-groups-by-id@openssh.com" sftp-server extension (when available) to fill in user/group names for directory listings. * sftp-server(8): support the "home-directory" extension request defined in draft-ietf-secsh-filexfer-extensions-00. This overlaps a bit with the existing "expand-path@openssh.com", but some other clients support it. * ssh-keygen(1), sshd(8): allow certificate validity intervals, sshsig verification times and authorized_keys expiry-time options to accept dates in the UTC time zone in addition to the default of interpreting them in the system time zone. YYYYMMDD and YYMMDDHHMM[SS] dates/times will be interpreted as UTC if suffixed with a 'Z' character. Also allow certificate validity intervals to be specified in raw seconds-since-epoch as hex value, e.g. -V 0x1234:0x4567890. This is intended for use by regress tests and other tools that call ssh-keygen as part of a CA workflow. bz3468 * sftp(1): allow arguments to the sftp -D option, e.g. sftp -D "/usr/libexec/sftp-server -el debug3" * ssh-keygen(1): allow the existing -U (use agent) flag to work with "-Y sign" operations, where it will be interpreted to require that the private keys is hosted in an agent; bz3429 MFC after: 2 weeks Relnotes: Yes Sponsored by: The FreeBSD Foundation
2022-10-19 14:27:11 +00:00
FIDO security token support needs [libfido2](https://github.com/Yubico/libfido2) and its dependencies.
In addition, certain platforms and build-time options may require additional dependencies; see README.platform for details about your platform.
### Building a release
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](#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.
### Building from git
If building from git, you'll need [autoconf](https://www.gnu.org/software/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
```
### Build-time Customisation
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).
ssh: update to OpenSSH 9.1p1 Release notes are available at https://www.openssh.com/txt/release-9.1 9.1 contains fixes for three minor memory safety problems; these have lready been merged to the copy of OpenSSH 9.0 that is in the FreeBSD base system. Some highlights copied from the release notes: Potentially-incompatible changes -------------------------------- * ssh(1), sshd(8): SetEnv directives in ssh_config and sshd_config are now first-match-wins to match other directives. Previously if an environment variable was multiply specified the last set value would have been used. bz3438 * ssh-keygen(8): ssh-keygen -A (generate all default host key types) will no longer generate DSA keys, as these are insecure and have not been used by default for some years. New features ------------ * ssh(1), sshd(8): add a RequiredRSASize directive to set a minimum RSA key length. Keys below this length will be ignored for user authentication and for host authentication in sshd(8). * sftp-server(8): add a "users-groups-by-id@openssh.com" extension request that allows the client to obtain user/group names that correspond to a set of uids/gids. * sftp(1): use "users-groups-by-id@openssh.com" sftp-server extension (when available) to fill in user/group names for directory listings. * sftp-server(8): support the "home-directory" extension request defined in draft-ietf-secsh-filexfer-extensions-00. This overlaps a bit with the existing "expand-path@openssh.com", but some other clients support it. * ssh-keygen(1), sshd(8): allow certificate validity intervals, sshsig verification times and authorized_keys expiry-time options to accept dates in the UTC time zone in addition to the default of interpreting them in the system time zone. YYYYMMDD and YYMMDDHHMM[SS] dates/times will be interpreted as UTC if suffixed with a 'Z' character. Also allow certificate validity intervals to be specified in raw seconds-since-epoch as hex value, e.g. -V 0x1234:0x4567890. This is intended for use by regress tests and other tools that call ssh-keygen as part of a CA workflow. bz3468 * sftp(1): allow arguments to the sftp -D option, e.g. sftp -D "/usr/libexec/sftp-server -el debug3" * ssh-keygen(1): allow the existing -U (use agent) flag to work with "-Y sign" operations, where it will be interpreted to require that the private keys is hosted in an agent; bz3429 MFC after: 2 weeks Relnotes: Yes Sponsored by: The FreeBSD Foundation
2022-10-19 14:27:11 +00:00
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](https://en.wikipedia.org/wiki/Pluggable_authentication_module) support. [OpenPAM](https://www.openpam.org/), [Linux PAM](http://www.linux-pam.org/) and Solaris PAM are supported.
``--with-libedit`` | Enable [libedit](https://www.thrysoee.dk/editline/) support for sftp.
``--with-kerberos5`` | Enable Kerberos/GSSAPI support. Both [Heimdal](https://www.h5l.org/) and [MIT](https://web.mit.edu/kerberos/) Kerberos implementations are supported.
``--with-selinux`` | Enable [SELinux](https://en.wikipedia.org/wiki/Security-Enhanced_Linux) support.
``--with-security-key-builtin`` | Include built-in support for U2F/FIDO2 security keys. This requires [libfido2](https://github.com/Yubico/libfido2) be installed.
## Development
Portable OpenSSH development is discussed on the [openssh-unix-dev mailing list](https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev) ([archive mirror](https://marc.info/?l=openssh-unix-dev)). Bugs and feature requests are tracked on our [Bugzilla](https://bugzilla.mindrot.org/).
## Reporting bugs
_Non-security_ bugs may be reported to the developers via [Bugzilla](https://bugzilla.mindrot.org/) or via the mailing list above. Security bugs should be reported to [openssh@openssh.com](mailto:openssh.openssh.com).