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| -rw-r--r-- | README | 52 | ||||
| -rw-r--r-- | README.dns | 47 | ||||
| -rw-r--r-- | README.md | 79 | ||||
| -rw-r--r-- | README.platform | 96 | ||||
| -rw-r--r-- | README.privsep | 51 | ||||
| -rw-r--r-- | README.tun | 132 |
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@@ -0,0 +1,52 @@ +See https://www.openssh.com/releasenotes.html#8.4p1 for the release notes. + +Please read https://www.openssh.com/report.html for bug reporting +instructions and note that we do not use Github for bug reporting or +patch/pull-request management. + +This is the port of OpenBSD's excellent OpenSSH[0] to Linux and other +Unices. + +OpenSSH is based on the last free version of Tatu Ylonen's sample +implementation with all patent-encumbered algorithms removed (to +external libraries), all known security bugs fixed, new features +reintroduced and many other clean-ups. OpenSSH has been created by +Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt, +and Dug Song. It has a homepage at https://www.openssh.com/ + +This port consists of the re-introduction of autoconf support, PAM +support, EGD/PRNGD support and replacements for OpenBSD library +functions that are (regrettably) absent from other unices. This port +has been best tested on AIX, Cygwin, HP-UX, Linux, MacOS/X, +FreeBSD, NetBSD, OpenBSD, OpenServer, Solaris and UnixWare. + +This version actively tracks changes in the OpenBSD CVS repository. + +The PAM support is now more functional than the popular packages of +commercial ssh-1.2.x. It checks "account" and "session" modules for +all logins, not just when using password authentication. + +There is now several mailing lists for this port of OpenSSH. Please +refer to https://www.openssh.com/list.html for details on how to join. + +Please send bug reports and patches to https://bugzilla.mindrot.org or +the mailing list openssh-unix-dev@mindrot.org. To mitigate spam, the +list only allows posting from subscribed addresses. Code contribution +are welcomed, but please follow the OpenBSD style guidelines[1]. + +Please refer to the INSTALL document for information on dependencies and +how to install OpenSSH on your system. + +Damien Miller <djm@mindrot.org> + +Miscellania - + +This version of OpenSSH is based upon code retrieved from the OpenBSD CVS +repository which in turn was based on the last free sample implementation +released by Tatu Ylonen. + +References - + +[0] https://www.openssh.com/ +[1] https://man.openbsd.org/style.9 + diff --git a/README.dns b/README.dns new file mode 100644 index 0000000..29ecaee --- /dev/null +++ b/README.dns @@ -0,0 +1,47 @@ +How to verify host keys using OpenSSH and DNS +--------------------------------------------- + +OpenSSH contains support for verifying host keys using DNS as described +in https://tools.ietf.org/html/rfc4255. The document contains very brief +instructions on how to use this feature. Configuring DNS is out of the +scope of this document. + + +(1) Server: Generate and publish the DNS RR + +To create a DNS resource record (RR) containing a fingerprint of the +public host key, use the following command: + + ssh-keygen -r hostname -f keyfile -g + +where "hostname" is your fully qualified hostname and "keyfile" is the +file containing the public host key file. If you have multiple keys, +you should generate one RR for each key. + +In the example above, ssh-keygen will print the fingerprint in a +generic DNS RR format parsable by most modern name server +implementations. If your nameserver has support for the SSHFP RR +you can omit the -g flag and ssh-keygen will print a standard SSHFP RR. + +To publish the fingerprint using the DNS you must add the generated RR +to your DNS zone file and sign your zone. + + +(2) Client: Enable ssh to verify host keys using DNS + +To enable the ssh client to verify host keys using DNS, you have to +add the following option to the ssh configuration file +($HOME/.ssh/config or /etc/ssh/ssh_config): + + VerifyHostKeyDNS yes + +Upon connection the client will try to look up the fingerprint RR +using DNS. If the fingerprint received from the DNS server matches +the remote host key, the user will be notified. + + + Jakob Schlyter + Wesley Griffin + + +$OpenBSD: README.dns,v 1.2 2003/10/14 19:43:23 jakob Exp $ diff --git a/README.md b/README.md new file mode 100644 index 0000000..28fb43d --- /dev/null +++ b/README.md @@ -0,0 +1,79 @@ +# Portable OpenSSH + +[](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, and [zlib](https://www.zlib.net/). ``libcrypto`` from either [LibreSSL](https://www.libressl.org/) or [OpenSSL](https://www.openssl.org) may also be used, but OpenSSH may be built without it supporting a subset of crypto algorithms. + +FIDO security token support need [libfido2](https://github.com/Yubico/libfido2) and its dependencies. Also, certain platforms and build-time options may require additional dependencies, see README.platform for details. + +### 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). + +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). diff --git a/README.platform b/README.platform new file mode 100644 index 0000000..9210e07 --- /dev/null +++ b/README.platform @@ -0,0 +1,96 @@ +This file contains notes about OpenSSH on specific platforms. + +AIX +--- +As of OpenSSH 3.8p1, sshd will now honour an accounts password expiry +settings, where previously it did not. Because of this, it's possible for +sites that have used OpenSSH's sshd exclusively to have accounts which +have passwords expired longer than the inactive time (ie the "Weeks between +password EXPIRATION and LOCKOUT" setting in SMIT or the maxexpired +chuser attribute). + +Accounts in this state must have their passwords reset manually by the +administrator. As a precaution, it is recommended that the administrative +passwords be reset before upgrading from OpenSSH <3.8. + +As of OpenSSH 4.0, configure will attempt to detect if your version +and maintenance level of AIX has a working getaddrinfo, and will use it +if found. This will enable IPv6 support. If for some reason configure +gets it wrong, or if you want to build binaries to work on earlier MLs +than the build host then you can add "-DBROKEN_GETADDRINFO" to CFLAGS +to force the previous IPv4-only behaviour. + +IPv6 known to work: 5.1ML7 5.2ML2 5.2ML5 +IPv6 known broken: 4.3.3ML11 5.1ML4 + +If you wish to use dynamic libraries that aren't in the normal system +locations (eg IBM's OpenSSL and zlib packages) then you will need to +define the environment variable blibpath before running configure, eg + +blibpath=/lib:/usr/lib:/opt/freeware/lib ./configure \ + --with-ssl-dir=/opt/freeware --with-zlib=/opt/freeware + +If sshd is built with the WITH_AIXAUTHENTICATE option (which is enabled +by default) then sshd checks that users are permitted via the +loginrestrictions() function, in particular that the user has the +"rlogin" attribute set. This check is not done for the root account, +instead the PermitRootLogin setting in sshd_config is used. + +If you are using the IBM compiler you probably want to use CC=xlc rather +than the default of cc. + + +Cygwin +------ +To build on Cygwin, OpenSSH requires the following packages: +gcc, gcc-mingw-core, mingw-runtime, binutils, make, openssl, +openssl-devel, zlib, minres, minires-devel. + + +Darwin and MacOS X +------------------ +Darwin does not provide a tun(4) driver required for OpenSSH-based +virtual private networks. The BSD manpage still exists, but the driver +has been removed in recent releases of Darwin and MacOS X. + +Nevertheless, tunnel support is known to work with Darwin 8 and +MacOS X 10.4 in Point-to-Point (Layer 3) and Ethernet (Layer 2) mode +using a third party driver. More information is available at: + http://www-user.rhrk.uni-kl.de/~nissler/tuntap/ + + +Linux +----- + +Some Linux distributions (including Red Hat/Fedora/CentOS) include +headers and library links in the -devel RPMs rather than the main +binary RPMs. If you get an error about headers, or complaining about a +missing prerequisite then you may need to install the equivalent +development packages. On Redhat based distros these may be openssl-devel, +zlib-devel and pam-devel, on Debian based distros these may be +libssl-dev, libz-dev and libpam-dev. + + +Solaris +------- +If you enable BSM auditing on Solaris, you need to update audit_event(4) +for praudit(1m) to give sensible output. The following line needs to be +added to /etc/security/audit_event: + + 32800:AUE_openssh:OpenSSH login:lo + +The BSM audit event range available for third party TCB applications is +32768 - 65535. Event number 32800 has been chosen for AUE_openssh. +There is no official registry of 3rd party event numbers, so if this +number is already in use on your system, you may change it at build time +by configure'ing --with-cflags=-DAUE_openssh=32801 then rebuilding. + + +Platforms using PAM +------------------- +As of OpenSSH 4.3p1, sshd will no longer check /etc/nologin itself when +PAM is enabled. To maintain existing behaviour, pam_nologin should be +added to sshd's session stack which will prevent users from starting shell +sessions. Alternatively, pam_nologin can be added to either the auth or +account stacks which will prevent authentication entirely, but will still +return the output from pam_nologin to the client. diff --git a/README.privsep b/README.privsep new file mode 100644 index 0000000..d658c46 --- /dev/null +++ b/README.privsep @@ -0,0 +1,51 @@ +Privilege separation, or privsep, is method in OpenSSH by which +operations that require root privilege are performed by a separate +privileged monitor process. Its purpose is to prevent privilege +escalation by containing corruption to an unprivileged process. +More information is available at: + http://www.citi.umich.edu/u/provos/ssh/privsep.html + +Privilege separation is now mandatory. During the pre-authentication +phase sshd will chroot(2) to "/var/empty" and change its privileges to the +"sshd" user and its primary group. sshd is a pseudo-account that should +not be used by other daemons, and must be locked and should contain a +"nologin" or invalid shell. + +You should do something like the following to prepare the privsep +preauth environment: + + # mkdir /var/empty + # chown root:sys /var/empty + # chmod 755 /var/empty + # groupadd sshd + # useradd -g sshd -c 'sshd privsep' -d /var/empty -s /bin/false sshd + +/var/empty should not contain any files. + +configure supports the following options to change the default +privsep user and chroot directory: + + --with-privsep-path=xxx Path for privilege separation chroot + --with-privsep-user=user Specify non-privileged user for privilege separation + +PAM-enabled OpenSSH is known to function with privsep on AIX, FreeBSD, +HP-UX (including Trusted Mode), Linux, NetBSD and Solaris. + +On Cygwin, Tru64 Unix and OpenServer only the pre-authentication part +of privsep is supported. Post-authentication privsep is disabled +automatically (so you won't see the additional process mentioned below). + +Note that for a normal interactive login with a shell, enabling privsep +will require 1 additional process per login session. + +Given the following process listing (from HP-UX): + + UID PID PPID C STIME TTY TIME COMMAND + root 1005 1 0 10:45:17 ? 0:08 /opt/openssh/sbin/sshd -u0 + root 6917 1005 0 15:19:16 ? 0:00 sshd: stevesk [priv] + stevesk 6919 6917 0 15:19:17 ? 0:03 sshd: stevesk@2 + stevesk 6921 6919 0 15:19:17 pts/2 0:00 -bash + +process 1005 is the sshd process listening for new connections. +process 6917 is the privileged monitor process, 6919 is the user owned +sshd process and 6921 is the shell process. diff --git a/README.tun b/README.tun new file mode 100644 index 0000000..5e1cb07 --- /dev/null +++ b/README.tun @@ -0,0 +1,132 @@ +How to use OpenSSH-based virtual private networks +------------------------------------------------- + +OpenSSH contains support for VPN tunneling using the tun(4) network +tunnel pseudo-device which is available on most platforms, either for +layer 2 or 3 traffic. + +The following brief instructions on how to use this feature use +a network configuration specific to the OpenBSD operating system. + +(1) Server: Enable support for SSH tunneling + +To enable the ssh server to accept tunnel requests from the client, you +have to add the following option to the ssh server configuration file +(/etc/ssh/sshd_config): + + PermitTunnel yes + +Restart the server or send the hangup signal (SIGHUP) to let the server +reread it's configuration. + +(2) Server: Restrict client access and assign the tunnel + +The OpenSSH server simply uses the file /root/.ssh/authorized_keys to +restrict the client to connect to a specified tunnel and to +automatically start the related interface configuration command. These +settings are optional but recommended: + + tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... reyk@openbsd.org + +(3) Client: Configure the local network tunnel interface + +Use the hostname.if(5) interface-specific configuration file to set up +the network tunnel configuration with OpenBSD. For example, use the +following configuration in /etc/hostname.tun0 to set up the layer 3 +tunnel on the client: + + inet 192.168.5.1 255.255.255.252 192.168.5.2 + +OpenBSD also supports layer 2 tunneling over the tun device by adding +the link0 flag: + + inet 192.168.1.78 255.255.255.0 192.168.1.255 link0 + +Layer 2 tunnels can be used in combination with an Ethernet bridge(4) +interface, like the following example for /etc/bridgename.bridge0: + + add tun0 + add sis0 + up + +(4) Client: Configure the OpenSSH client + +To establish tunnel forwarding for connections to a specified +remote host by default, use the following ssh client configuration for +the privileged user (in /root/.ssh/config): + + Host sshgateway + Tunnel yes + TunnelDevice 0:any + PermitLocalCommand yes + LocalCommand sh /etc/netstart tun0 + +A more complicated configuration is possible to establish a tunnel to +a remote host which is not directly accessible by the client. +The following example describes a client configuration to connect to +the remote host over two ssh hops in between. It uses the OpenSSH +ProxyCommand in combination with the nc(1) program to forward the final +ssh tunnel destination over multiple ssh sessions. + + Host access.somewhere.net + User puffy + Host dmzgw + User puffy + ProxyCommand ssh access.somewhere.net nc dmzgw 22 + Host sshgateway + Tunnel Ethernet + TunnelDevice 0:any + PermitLocalCommand yes + LocalCommand sh /etc/netstart tun0 + ProxyCommand ssh dmzgw nc sshgateway 22 + +The following network plan illustrates the previous configuration in +combination with layer 2 tunneling and Ethernet bridging. + ++--------+ ( ) +----------------------+ +| Client |------( Internet )-----| access.somewhere.net | ++--------+ ( ) +----------------------+ + : 192.168.1.78 | + :............................. +-------+ + Forwarded ssh connection : | dmzgw | + Layer 2 tunnel : +-------+ + : | + : | + : +------------+ + :......| sshgateway | + | +------------+ +--- real connection Bridge -> | +----------+ +... "virtual connection" [ X ]--------| somehost | +[X] switch +----------+ + 192.168.1.25 + +(5) Client: Connect to the server and establish the tunnel + +Finally connect to the OpenSSH server to establish the tunnel by using +the following command: + + ssh sshgateway + +It is also possible to tell the client to fork into the background after +the connection has been successfully established: + + ssh -f sshgateway true + +Without the ssh configuration done in step (4), it is also possible +to use the following command lines: + + ssh -fw 0:1 sshgateway true + ifconfig tun0 192.168.5.1 192.168.5.2 netmask 255.255.255.252 + +Using OpenSSH tunnel forwarding is a simple way to establish secure +and ad hoc virtual private networks. Possible fields of application +could be wireless networks or administrative VPN tunnels. + +Nevertheless, ssh tunneling requires some packet header overhead and +runs on top of TCP. It is still suggested to use the IP Security +Protocol (IPSec) for robust and permanent VPN connections and to +interconnect corporate networks. + + Reyk Floeter + +$OpenBSD: README.tun,v 1.4 2006/03/28 00:12:31 deraadt Exp $ |