f374ba41f5
Release notes are available at https://www.openssh.com/txt/release-9.2 OpenSSH 9.2 contains fixes for two security problems and a memory safety problem. The memory safety problem is not believed to be exploitable. These fixes have already been committed to OpenSSH 9.1 in FreeBSD. Some other notable items from the release notes: * ssh(1): add a new EnableEscapeCommandline ssh_config(5) option that controls whether the client-side ~C escape sequence that provides a command-line is available. Among other things, the ~C command-line could be used to add additional port-forwards at runtime. * sshd(8): add support for channel inactivity timeouts via a new sshd_config(5) ChannelTimeout directive. This allows channels that have not seen traffic in a configurable interval to be automatically closed. Different timeouts may be applied to session, X11, agent and TCP forwarding channels. * sshd(8): add a sshd_config UnusedConnectionTimeout option to terminate client connections that have no open channels for a length of time. This complements the ChannelTimeout option above. * sshd(8): add a -V (version) option to sshd like the ssh client has. * scp(1), sftp(1): add a -X option to both scp(1) and sftp(1) to allow control over some SFTP protocol parameters: the copy buffer length and the number of in-flight requests, both of which are used during upload/download. Previously these could be controlled in sftp(1) only. This makes them available in both SFTP protocol clients using the same option character sequence. * ssh-keyscan(1): allow scanning of complete CIDR address ranges, e.g. "ssh-keyscan 192.168.0.0/24". If a CIDR range is passed, then it will be expanded to all possible addresses in the range including the all-0s and all-1s addresses. bz#976 * ssh(1): support dynamic remote port forwarding in escape command-line's -R processing. bz#3499 MFC after: 1 week Sponsored by: The FreeBSD Foundation
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298 lines
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Plaintext
1. Prerequisites
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----------------
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A C compiler. Any C89 or better compiler that supports variadic macros
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should work. Where supported, configure will attempt to enable the
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compiler's run-time integrity checking options. Some notes about
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specific compilers:
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- clang: -ftrapv and -sanitize=integer require the compiler-rt runtime
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(CC=clang LDFLAGS=--rtlib=compiler-rt ./configure)
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To support Privilege Separation (which is now required) you will need
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to create the user, group and directory used by sshd for privilege
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separation. See README.privsep for details.
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The remaining items are optional.
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A working installation of zlib:
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Zlib 1.1.4 or 1.2.1.2 or greater (earlier 1.2.x versions have problems):
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https://zlib.net/
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libcrypto from either of LibreSSL or OpenSSL. Building without libcrypto
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is supported but severely restricts the available ciphers and algorithms.
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- LibreSSL (https://www.libressl.org/)
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- OpenSSL (https://www.openssl.org) with any of the following versions:
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- 1.0.x >= 1.0.1 or 1.1.0 >= 1.1.0g or any 1.1.1
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Note that due to a bug in EVP_CipherInit OpenSSL 1.1 versions prior to
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1.1.0g can't be used.
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LibreSSL/OpenSSL should be compiled as a position-independent library
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(i.e. -fPIC, eg by configuring OpenSSL as "./config [options] -fPIC"
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or LibreSSL as "CFLAGS=-fPIC ./configure") otherwise OpenSSH will not
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be able to link with it. If you must use a non-position-independent
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libcrypto, then you may need to configure OpenSSH --without-pie.
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If you build either from source, running the OpenSSL self-test ("make
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tests") or the LibreSSL equivalent ("make check") and ensuring that all
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tests pass is strongly recommended.
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NB. If you operating system supports /dev/random, you should configure
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libcrypto (LibreSSL/OpenSSL) to use it. OpenSSH relies on libcrypto's
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direct support of /dev/random, or failing that, either prngd or egd.
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PRNGD:
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If your system lacks kernel-based random collection, the use of Lutz
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Jaenicke's PRNGd is recommended. It requires that libcrypto be configured
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to support it.
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http://prngd.sourceforge.net/
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EGD:
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The Entropy Gathering Daemon (EGD) supports the same interface as prngd.
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It also supported only if libcrypto is configured to support it.
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http://egd.sourceforge.net/
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PAM:
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OpenSSH can utilise Pluggable Authentication Modules (PAM) if your
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system supports it. PAM is standard most Linux distributions, Solaris,
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HP-UX 11, AIX >= 5.2, FreeBSD, NetBSD and Mac OS X.
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Information about the various PAM implementations are available:
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Solaris PAM: http://www.sun.com/software/solaris/pam/
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Linux PAM: http://www.kernel.org/pub/linux/libs/pam/
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OpenPAM: http://www.openpam.org/
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If you wish to build the GNOME passphrase requester, you will need the GNOME
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libraries and headers.
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GNOME:
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http://www.gnome.org/
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Alternatively, Jim Knoble <jmknoble@pobox.com> has written an excellent X11
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passphrase requester. This is maintained separately at:
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http://www.jmknoble.net/software/x11-ssh-askpass/
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TCP Wrappers:
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If you wish to use the TCP wrappers functionality you will need at least
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tcpd.h and libwrap.a, either in the standard include and library paths,
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or in the directory specified by --with-tcp-wrappers. Version 7.6 is
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known to work.
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http://ftp.porcupine.org/pub/security/index.html
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LibEdit:
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sftp supports command-line editing via NetBSD's libedit. If your platform
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has it available natively you can use that, alternatively you might try
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these multi-platform ports:
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http://www.thrysoee.dk/editline/
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http://sourceforge.net/projects/libedit/
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LDNS:
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LDNS is a DNS BSD-licensed resolver library which supports DNSSEC.
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http://nlnetlabs.nl/projects/ldns/
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Autoconf:
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If you modify configure.ac or configure doesn't exist (eg if you checked
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the code out of git yourself) then you will need autoconf-2.69 and
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automake-1.16.1 to rebuild the automatically generated files by running
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"autoreconf". Earlier versions may also work but this is not guaranteed.
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http://www.gnu.org/software/autoconf/
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http://www.gnu.org/software/automake/
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Basic Security Module (BSM):
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Native BSM support is known to exist in Solaris from at least 2.5.1,
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FreeBSD 6.1 and OS X. Alternatively, you may use the OpenBSM
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implementation (http://www.openbsm.org).
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makedepend:
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https://www.x.org/archive/individual/util/
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If you are making significant changes to the code you may need to rebuild
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the dependency (.depend) file using "make depend", which requires the
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"makedepend" tool from the X11 distribution.
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libfido2:
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libfido2 allows the use of hardware security keys over USB. libfido2
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in turn depends on libcbor. libfido2 >= 1.5.0 is strongly recommended.
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Limited functionality is possible with earlier libfido2 versions.
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https://github.com/Yubico/libfido2
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https://github.com/pjk/libcbor
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2. Building / Installation
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--------------------------
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To install OpenSSH with default options:
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./configure
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make
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make install
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This will install the OpenSSH binaries in /usr/local/bin, configuration files
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in /usr/local/etc, the server in /usr/local/sbin, etc. To specify a different
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installation prefix, use the --prefix option to configure:
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./configure --prefix=/opt
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make
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make install
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Will install OpenSSH in /opt/{bin,etc,lib,sbin}. You can also override
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specific paths, for example:
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./configure --prefix=/opt --sysconfdir=/etc/ssh
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make
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make install
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This will install the binaries in /opt/{bin,lib,sbin}, but will place the
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configuration files in /etc/ssh.
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If you are using PAM, you may need to manually install a PAM control
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file as "/etc/pam.d/sshd" (or wherever your system prefers to keep
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them). Note that the service name used to start PAM is __progname,
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which is the basename of the path of your sshd (e.g., the service name
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for /usr/sbin/osshd will be osshd). If you have renamed your sshd
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executable, your PAM configuration may need to be modified.
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A generic PAM configuration is included as "contrib/sshd.pam.generic",
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you may need to edit it before using it on your system. If you are
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using a recent version of Red Hat Linux, the config file in
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contrib/redhat/sshd.pam should be more useful. Failure to install a
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valid PAM file may result in an inability to use password
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authentication. On HP-UX 11 and Solaris, the standard /etc/pam.conf
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configuration will work with sshd (sshd will match the other service
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name).
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There are a few other options to the configure script:
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--with-audit=[module] enable additional auditing via the specified module.
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Currently, drivers for "debug" (additional info via syslog) and "bsm"
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(Sun's Basic Security Module) are supported.
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--with-pam enables PAM support. If PAM support is compiled in, it must
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also be enabled in sshd_config (refer to the UsePAM directive).
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--with-prngd-socket=/some/file allows you to enable EGD or PRNGD
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support and to specify a PRNGd socket. Use this if your Unix lacks
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/dev/random.
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--with-prngd-port=portnum allows you to enable EGD or PRNGD support
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and to specify a EGD localhost TCP port. Use this if your Unix lacks
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/dev/random.
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--with-lastlog=FILE will specify the location of the lastlog file.
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./configure searches a few locations for lastlog, but may not find
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it if lastlog is installed in a different place.
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--without-lastlog will disable lastlog support entirely.
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--with-osfsia, --without-osfsia will enable or disable OSF1's Security
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Integration Architecture. The default for OSF1 machines is enable.
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--with-tcp-wrappers will enable TCP Wrappers (/etc/hosts.allow|deny)
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support.
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--with-utmpx enables utmpx support. utmpx support is automatic for
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some platforms.
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--without-shadow disables shadow password support.
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--with-ipaddr-display forces the use of a numeric IP address in the
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$DISPLAY environment variable. Some broken systems need this.
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--with-default-path=PATH allows you to specify a default $PATH for sessions
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started by sshd. This replaces the standard path entirely.
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--with-pid-dir=PATH specifies the directory in which the sshd.pid file is
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created.
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--with-xauth=PATH specifies the location of the xauth binary
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--with-ssl-dir=DIR allows you to specify where your Libre/OpenSSL
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libraries are installed.
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--with-ssl-engine enables Libre/OpenSSL's (hardware) ENGINE support
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--without-openssl builds without using OpenSSL. Only a subset of ciphers
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and algorithms are supported in this configuration.
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--without-zlib builds without zlib. This disables the Compression option.
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--with-4in6 Check for IPv4 in IPv6 mapped addresses and convert them to
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real (AF_INET) IPv4 addresses. Works around some quirks on Linux.
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If you need to pass special options to the compiler or linker, you
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can specify these as environment variables before running ./configure.
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For example:
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CC="/usr/foo/cc" CFLAGS="-O" LDFLAGS="-s" LIBS="-lrubbish" ./configure
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3. Configuration
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----------------
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The runtime configuration files are installed by in ${prefix}/etc or
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whatever you specified as your --sysconfdir (/usr/local/etc by default).
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The default configuration should be instantly usable, though you should
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review it to ensure that it matches your security requirements.
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To generate a host key, run "make host-key". Alternately you can do so
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manually using the following commands:
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ssh-keygen -t [type] -f /etc/ssh/ssh_host_key -N ""
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for each of the types you wish to generate (rsa, dsa or ecdsa) or
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ssh-keygen -A
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to generate keys for all supported types.
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Replacing /etc/ssh with the correct path to the configuration directory.
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(${prefix}/etc or whatever you specified with --sysconfdir during
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configuration).
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If you have configured OpenSSH with EGD/prngd support, ensure that EGD or
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prngd is running and has collected some entropy first.
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For more information on configuration, please refer to the manual pages
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for sshd, ssh and ssh-agent.
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4. (Optional) Send survey
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-------------------------
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$ make survey
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[check the contents of the file "survey" to ensure there's no information
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that you consider sensitive]
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$ make send-survey
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This will send configuration information for the currently configured
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host to a survey address. This will help determine which configurations
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are actually in use, and what valid combinations of configure options
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exist. The raw data is available only to the OpenSSH developers, however
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summary data may be published.
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5. Problems?
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------------
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If you experience problems compiling, installing or running OpenSSH,
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please refer to the "reporting bugs" section of the webpage at
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https://www.openssh.com/
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