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 one of LibreSSL, OpenSSL, AWS-LC or BoringSSL. Building 23without libcrypto is supported but severely restricts the available 24ciphers and algorithms. 25 - LibreSSL (https://www.libressl.org/) 3.1.0 or greater 26 - OpenSSL (https://www.openssl.org) 1.1.1 or greater 27 - AWS-LC (https://github.com/aws/aws-lc) 28 - BoringSSL (https://github.com/google/boringssl) 29 30libcrypto should be compiled as a position-independent library 31(i.e. -fPIC, eg by configuring OpenSSL as "./config [options] -fPIC" 32or LibreSSL as "CFLAGS=-fPIC ./configure") otherwise OpenSSH will not 33be able to link with it. If you must use a non-position-independent 34libcrypto, then you may need to configure OpenSSH --without-pie. 35 36If you build either from source, running the OpenSSL self-test ("make 37tests") or the LibreSSL equivalent ("make check") and ensuring that all 38tests pass is strongly recommended. 39 40NB. If you operating system supports /dev/random, you should configure 41libcrypto (LibreSSL/OpenSSL) to use it. OpenSSH relies on libcrypto's 42direct support of /dev/random, or failing that, either prngd or egd. 43 44PRNGD: 45 46If your system lacks kernel-based random collection, the use of Lutz 47Jaenicke's PRNGd is recommended. If you are using libcrypto it requires 48that the libcrypto is configured to support it. If you are building 49--without-openssl then the --with-prngd-socket option must match the 50socket provided by prngd. 51 52http://prngd.sourceforge.net/ 53 54EGD: 55 56The Entropy Gathering Daemon (EGD) supports the same interface as prngd. 57The same caveats about configuration for prngd also apply. 58 59http://egd.sourceforge.net/ 60 61PAM: 62 63OpenSSH can utilise Pluggable Authentication Modules (PAM) if your 64system supports it. PAM is standard most Linux distributions, Solaris, 65HP-UX 11, AIX >= 5.2, FreeBSD, NetBSD and Mac OS X. 66 67Information about the various PAM implementations are available: 68 69Solaris PAM: http://www.sun.com/software/solaris/pam/ 70Linux PAM: http://www.kernel.org/pub/linux/libs/pam/ 71OpenPAM: http://www.openpam.org/ 72 73If you wish to build the GNOME passphrase requester, you will need the GNOME 74libraries and headers. 75 76GNOME: 77http://www.gnome.org/ 78 79Alternatively, Jim Knoble <jmknoble@pobox.com> has written an excellent X11 80passphrase requester. This is maintained separately at: 81 82http://www.jmknoble.net/software/x11-ssh-askpass/ 83 84TCP Wrappers: 85 86If you wish to use the TCP wrappers functionality you will need at least 87tcpd.h and libwrap.a, either in the standard include and library paths, 88or in the directory specified by --with-tcp-wrappers. Version 7.6 is 89known to work. 90 91http://ftp.porcupine.org/pub/security/index.html 92 93LibEdit: 94 95sftp supports command-line editing via NetBSD's libedit. If your platform 96has it available natively you can use that, alternatively you might try 97these multi-platform ports: 98 99http://www.thrysoee.dk/editline/ 100http://sourceforge.net/projects/libedit/ 101 102LDNS: 103 104LDNS is a DNS BSD-licensed resolver library which supports DNSSEC. 105 106http://nlnetlabs.nl/projects/ldns/ 107 108Autoconf: 109 110If you modify configure.ac or configure doesn't exist (eg if you checked 111the main git branch) then you will need autoconf-2.69 and automake-1.16.1 112or newer to rebuild the automatically generated files by running 113"autoreconf". Earlier versions may also work but this is not guaranteed. 114 115http://www.gnu.org/software/autoconf/ 116http://www.gnu.org/software/automake/ 117 118Basic Security Module (BSM): 119 120Native BSM support is known to exist in Solaris from at least 2.5.1, 121FreeBSD 6.1 and OS X. Alternatively, you may use the OpenBSM 122implementation (http://www.openbsm.org). 123 124makedepend: 125 126https://www.x.org/archive/individual/util/ 127 128If you are making significant changes to the code you may need to rebuild 129the dependency (.depend) file using "make depend", which requires the 130"makedepend" tool from the X11 distribution. 131 132libfido2: 133 134libfido2 allows the use of hardware security keys over USB. libfido2 135in turn depends on libcbor. libfido2 >= 1.5.0 is strongly recommended. 136Limited functionality is possible with earlier libfido2 versions. 137 138https://github.com/Yubico/libfido2 139https://github.com/pjk/libcbor 140 141 1422. Building / Installation 143-------------------------- 144 145To install OpenSSH with default options: 146 147./configure 148make 149make install 150 151This will install the OpenSSH binaries in /usr/local/bin, configuration files 152in /usr/local/etc, the server in /usr/local/sbin, etc. To specify a different 153installation prefix, use the --prefix option to configure: 154 155./configure --prefix=/opt 156make 157make install 158 159Will install OpenSSH in /opt/{bin,etc,lib,sbin}. You can also override 160specific paths, for example: 161 162./configure --prefix=/opt --sysconfdir=/etc/ssh 163make 164make install 165 166This will install the binaries in /opt/{bin,lib,sbin}, but will place the 167configuration files in /etc/ssh. 168 169If you are using PAM, you may need to manually install a PAM control 170file as "/etc/pam.d/sshd" (or wherever your system prefers to keep 171them). Note that the service name used to start PAM is __progname, 172which is the basename of the path of your sshd (e.g., the service name 173for /usr/sbin/osshd will be osshd). If you have renamed your sshd 174executable, your PAM configuration may need to be modified. 175 176A generic PAM configuration is included as "contrib/sshd.pam.generic", 177you may need to edit it before using it on your system. If you are 178using a recent version of Red Hat Linux, the config file in 179contrib/redhat/sshd.pam should be more useful. Failure to install a 180valid PAM file may result in an inability to use password 181authentication. On HP-UX 11 and Solaris, the standard /etc/pam.conf 182configuration will work with sshd (sshd will match the other service 183name). 184 185There are a few other options to the configure script: 186 187--with-audit=[module] enable additional auditing via the specified module. 188Currently, drivers for "debug" (additional info via syslog) and "bsm" 189(Sun's Basic Security Module) are supported. 190 191--with-pam enables PAM support. If PAM support is compiled in, it must 192also be enabled in sshd_config (refer to the UsePAM directive). 193 194--with-prngd-socket=/some/file allows you to enable EGD or PRNGD 195support and to specify a PRNGd socket. Use this if your Unix lacks 196/dev/random. 197 198--with-prngd-port=portnum allows you to enable EGD or PRNGD support 199and to specify a EGD localhost TCP port. Use this if your Unix lacks 200/dev/random. 201 202--with-lastlog=FILE will specify the location of the lastlog file. 203./configure searches a few locations for lastlog, but may not find 204it if lastlog is installed in a different place. 205 206--without-lastlog will disable lastlog support entirely. 207 208--with-osfsia, --without-osfsia will enable or disable OSF1's Security 209Integration Architecture. The default for OSF1 machines is enable. 210 211--with-tcp-wrappers will enable TCP Wrappers (/etc/hosts.allow|deny) 212support. 213 214--with-utmpx enables utmpx support. utmpx support is automatic for 215some platforms. 216 217--without-shadow disables shadow password support. 218 219--with-ipaddr-display forces the use of a numeric IP address in the 220$DISPLAY environment variable. Some broken systems need this. 221 222--with-default-path=PATH allows you to specify a default $PATH for sessions 223started by sshd. This replaces the standard path entirely. 224 225--with-pid-dir=PATH specifies the directory in which the sshd.pid file is 226created. 227 228--with-xauth=PATH specifies the location of the xauth binary 229 230--with-ssl-dir=DIR allows you to specify where your Libre/OpenSSL 231libraries are installed. 232 233--with-ssl-engine enables Libre/OpenSSL's (hardware) ENGINE support 234 235--without-openssl builds without using OpenSSL. Only a subset of ciphers 236and algorithms are supported in this configuration. 237 238--without-zlib builds without zlib. This disables the Compression option. 239 240--with-4in6 Check for IPv4 in IPv6 mapped addresses and convert them to 241real (AF_INET) IPv4 addresses. Works around some quirks on Linux. 242 243If you need to pass special options to the compiler or linker, you 244can specify these as environment variables before running ./configure. 245For example: 246 247CC="/usr/foo/cc" CFLAGS="-O" LDFLAGS="-s" LIBS="-lrubbish" ./configure 248 2493. Configuration 250---------------- 251 252The runtime configuration files are installed by in ${prefix}/etc or 253whatever you specified as your --sysconfdir (/usr/local/etc by default). 254 255The default configuration should be instantly usable, though you should 256review it to ensure that it matches your security requirements. 257 258To generate a host key, run "make host-key". Alternately you can do so 259manually using the following commands: 260 261 ssh-keygen -t [type] -f /etc/ssh/ssh_host_key -N "" 262 263for each of the types you wish to generate (rsa, ed25519 or ecdsa) or 264 265 ssh-keygen -A 266 267to generate keys for all supported types. 268 269Replacing /etc/ssh with the correct path to the configuration directory. 270(${prefix}/etc or whatever you specified with --sysconfdir during 271configuration). 272 273If you have configured OpenSSH with EGD/prngd support, ensure that EGD or 274prngd is running and has collected some entropy first. 275 276For more information on configuration, please refer to the manual pages 277for sshd, ssh and ssh-agent. 278 2794. (Optional) Send survey 280------------------------- 281 282$ make survey 283[check the contents of the file "survey" to ensure there's no information 284that you consider sensitive] 285$ make send-survey 286 287This will send configuration information for the currently configured 288host to a survey address. This will help determine which configurations 289are actually in use, and what valid combinations of configure options 290exist. The raw data is available only to the OpenSSH developers, however 291summary data may be published. 292 2935. Problems? 294------------ 295 296If you experience problems compiling, installing or running OpenSSH, 297please refer to the "reporting bugs" section of the webpage at 298https://www.openssh.com/ 299