11. Prerequisites 2---------------- 3 4A C compiler. Any C89 or better compiler that supports variadic macros 5should work. Where supported, configure will attempt to enable the 6compiler's run-time integrity checking options. Some notes about 7specific compilers: 8 - clang: -ftrapv and -sanitize=integer require the compiler-rt runtime 9 (CC=clang LDFLAGS=--rtlib=compiler-rt ./configure) 10 11To support Privilege Separation (which is now required) you will need 12to create the user, group and directory used by sshd for privilege 13separation. See README.privsep for details. 14 15 16The remaining items are optional. 17 18A working installation of zlib: 19Zlib 1.1.4 or 1.2.1.2 or greater (earlier 1.2.x versions have problems): 20https://zlib.net/ 21 22libcrypto from either of LibreSSL or OpenSSL. Building without libcrypto 23is supported but severely restricts the available ciphers and algorithms. 24 - LibreSSL (https://www.libressl.org/) 25 - OpenSSL (https://www.openssl.org) with any of the following versions: 26 - 1.0.x >= 1.0.1 or 1.1.0 >= 1.1.0g or any 1.1.1 27 28Note that due to a bug in EVP_CipherInit OpenSSL 1.1 versions prior to 291.1.0g can't be used. 30 31LibreSSL/OpenSSL should be compiled as a position-independent library 32(i.e. -fPIC, eg by configuring OpenSSL as "./config [options] -fPIC" 33or LibreSSL as "CFLAGS=-fPIC ./configure") otherwise OpenSSH will not 34be able to link with it. If you must use a non-position-independent 35libcrypto, then you may need to configure OpenSSH --without-pie. 36 37If you build either from source, running the OpenSSL self-test ("make 38tests") or the LibreSSL equivalent ("make check") and ensuring that all 39tests pass is strongly recommended. 40 41NB. If you operating system supports /dev/random, you should configure 42libcrypto (LibreSSL/OpenSSL) to use it. OpenSSH relies on libcrypto's 43direct support of /dev/random, or failing that, either prngd or egd. 44 45PRNGD: 46 47If your system lacks kernel-based random collection, the use of Lutz 48Jaenicke's PRNGd is recommended. It requires that libcrypto be configured 49to support it. 50 51http://prngd.sourceforge.net/ 52 53EGD: 54 55The Entropy Gathering Daemon (EGD) supports the same interface as prngd. 56It also supported only if libcrypto is configured to support it. 57 58http://egd.sourceforge.net/ 59 60PAM: 61 62OpenSSH can utilise Pluggable Authentication Modules (PAM) if your 63system supports it. PAM is standard most Linux distributions, Solaris, 64HP-UX 11, AIX >= 5.2, FreeBSD, NetBSD and Mac OS X. 65 66Information about the various PAM implementations are available: 67 68Solaris PAM: http://www.sun.com/software/solaris/pam/ 69Linux PAM: http://www.kernel.org/pub/linux/libs/pam/ 70OpenPAM: http://www.openpam.org/ 71 72If you wish to build the GNOME passphrase requester, you will need the GNOME 73libraries and headers. 74 75GNOME: 76http://www.gnome.org/ 77 78Alternatively, Jim Knoble <jmknoble@pobox.com> has written an excellent X11 79passphrase requester. This is maintained separately at: 80 81http://www.jmknoble.net/software/x11-ssh-askpass/ 82 83TCP Wrappers: 84 85If you wish to use the TCP wrappers functionality you will need at least 86tcpd.h and libwrap.a, either in the standard include and library paths, 87or in the directory specified by --with-tcp-wrappers. Version 7.6 is 88known to work. 89 90http://ftp.porcupine.org/pub/security/index.html 91 92LibEdit: 93 94sftp supports command-line editing via NetBSD's libedit. If your platform 95has it available natively you can use that, alternatively you might try 96these multi-platform ports: 97 98http://www.thrysoee.dk/editline/ 99http://sourceforge.net/projects/libedit/ 100 101LDNS: 102 103LDNS is a DNS BSD-licensed resolver library which supports DNSSEC. 104 105http://nlnetlabs.nl/projects/ldns/ 106 107Autoconf: 108 109If you modify configure.ac or configure doesn't exist (eg if you checked 110the code out of git yourself) then you will need autoconf-2.69 and 111automake-1.16.1 to rebuild the automatically generated files by running 112"autoreconf". Earlier versions may also work but this is not guaranteed. 113 114http://www.gnu.org/software/autoconf/ 115http://www.gnu.org/software/automake/ 116 117Basic Security Module (BSM): 118 119Native BSM support is known to exist in Solaris from at least 2.5.1, 120FreeBSD 6.1 and OS X. Alternatively, you may use the OpenBSM 121implementation (http://www.openbsm.org). 122 123makedepend: 124 125https://www.x.org/archive/individual/util/ 126 127If you are making significant changes to the code you may need to rebuild 128the dependency (.depend) file using "make depend", which requires the 129"makedepend" tool from the X11 distribution. 130 131libfido2: 132 133libfido2 allows the use of hardware security keys over USB. libfido2 134in turn depends on libcbor. libfido2 >= 1.5.0 is strongly recommended. 135Limited functionality is possible with earlier libfido2 versions. 136 137https://github.com/Yubico/libfido2 138https://github.com/pjk/libcbor 139 140 1412. Building / Installation 142-------------------------- 143 144To install OpenSSH with default options: 145 146./configure 147make 148make install 149 150This will install the OpenSSH binaries in /usr/local/bin, configuration files 151in /usr/local/etc, the server in /usr/local/sbin, etc. To specify a different 152installation prefix, use the --prefix option to configure: 153 154./configure --prefix=/opt 155make 156make install 157 158Will install OpenSSH in /opt/{bin,etc,lib,sbin}. You can also override 159specific paths, for example: 160 161./configure --prefix=/opt --sysconfdir=/etc/ssh 162make 163make install 164 165This will install the binaries in /opt/{bin,lib,sbin}, but will place the 166configuration files in /etc/ssh. 167 168If you are using PAM, you may need to manually install a PAM control 169file as "/etc/pam.d/sshd" (or wherever your system prefers to keep 170them). Note that the service name used to start PAM is __progname, 171which is the basename of the path of your sshd (e.g., the service name 172for /usr/sbin/osshd will be osshd). If you have renamed your sshd 173executable, your PAM configuration may need to be modified. 174 175A generic PAM configuration is included as "contrib/sshd.pam.generic", 176you may need to edit it before using it on your system. If you are 177using a recent version of Red Hat Linux, the config file in 178contrib/redhat/sshd.pam should be more useful. Failure to install a 179valid PAM file may result in an inability to use password 180authentication. On HP-UX 11 and Solaris, the standard /etc/pam.conf 181configuration will work with sshd (sshd will match the other service 182name). 183 184There are a few other options to the configure script: 185 186--with-audit=[module] enable additional auditing via the specified module. 187Currently, drivers for "debug" (additional info via syslog) and "bsm" 188(Sun's Basic Security Module) are supported. 189 190--with-pam enables PAM support. If PAM support is compiled in, it must 191also be enabled in sshd_config (refer to the UsePAM directive). 192 193--with-prngd-socket=/some/file allows you to enable EGD or PRNGD 194support and to specify a PRNGd socket. Use this if your Unix lacks 195/dev/random. 196 197--with-prngd-port=portnum allows you to enable EGD or PRNGD support 198and to specify a EGD localhost TCP port. Use this if your Unix lacks 199/dev/random. 200 201--with-lastlog=FILE will specify the location of the lastlog file. 202./configure searches a few locations for lastlog, but may not find 203it if lastlog is installed in a different place. 204 205--without-lastlog will disable lastlog support entirely. 206 207--with-osfsia, --without-osfsia will enable or disable OSF1's Security 208Integration Architecture. The default for OSF1 machines is enable. 209 210--with-tcp-wrappers will enable TCP Wrappers (/etc/hosts.allow|deny) 211support. 212 213--with-utmpx enables utmpx support. utmpx support is automatic for 214some platforms. 215 216--without-shadow disables shadow password support. 217 218--with-ipaddr-display forces the use of a numeric IP address in the 219$DISPLAY environment variable. Some broken systems need this. 220 221--with-default-path=PATH allows you to specify a default $PATH for sessions 222started by sshd. This replaces the standard path entirely. 223 224--with-pid-dir=PATH specifies the directory in which the sshd.pid file is 225created. 226 227--with-xauth=PATH specifies the location of the xauth binary 228 229--with-ssl-dir=DIR allows you to specify where your Libre/OpenSSL 230libraries are installed. 231 232--with-ssl-engine enables Libre/OpenSSL's (hardware) ENGINE support 233 234--without-openssl builds without using OpenSSL. Only a subset of ciphers 235and algorithms are supported in this configuration. 236 237--without-zlib builds without zlib. This disables the Compression option. 238 239--with-4in6 Check for IPv4 in IPv6 mapped addresses and convert them to 240real (AF_INET) IPv4 addresses. Works around some quirks on Linux. 241 242If you need to pass special options to the compiler or linker, you 243can specify these as environment variables before running ./configure. 244For example: 245 246CC="/usr/foo/cc" CFLAGS="-O" LDFLAGS="-s" LIBS="-lrubbish" ./configure 247 2483. Configuration 249---------------- 250 251The runtime configuration files are installed by in ${prefix}/etc or 252whatever you specified as your --sysconfdir (/usr/local/etc by default). 253 254The default configuration should be instantly usable, though you should 255review it to ensure that it matches your security requirements. 256 257To generate a host key, run "make host-key". Alternately you can do so 258manually using the following commands: 259 260 ssh-keygen -t [type] -f /etc/ssh/ssh_host_key -N "" 261 262for each of the types you wish to generate (rsa, dsa or ecdsa) or 263 264 ssh-keygen -A 265 266to generate keys for all supported types. 267 268Replacing /etc/ssh with the correct path to the configuration directory. 269(${prefix}/etc or whatever you specified with --sysconfdir during 270configuration). 271 272If you have configured OpenSSH with EGD/prngd support, ensure that EGD or 273prngd is running and has collected some entropy first. 274 275For more information on configuration, please refer to the manual pages 276for sshd, ssh and ssh-agent. 277 2784. (Optional) Send survey 279------------------------- 280 281$ make survey 282[check the contents of the file "survey" to ensure there's no information 283that you consider sensitive] 284$ make send-survey 285 286This will send configuration information for the currently configured 287host to a survey address. This will help determine which configurations 288are actually in use, and what valid combinations of configure options 289exist. The raw data is available only to the OpenSSH developers, however 290summary data may be published. 291 2925. Problems? 293------------ 294 295If you experience problems compiling, installing or running OpenSSH, 296please refer to the "reporting bugs" section of the webpage at 297https://www.openssh.com/ 298