11. Prerequisites 2---------------- 3 4A C compiler. Any C89 or better compiler should work. Where supported, 5configure will attempt to enable the compiler's run-time integrity checking 6options. Some notes about specific compilers: 7 - clang: -ftrapv and -sanitize=integer require the compiler-rt runtime 8 (CC=clang LDFLAGS=--rtlib=compiler-rt ./configure) 9 10To support Privilege Separation (which is now required) you will need 11to create the user, group and directory used by sshd for privilege 12separation. See README.privsep for details. 13 14 15The remaining items are optional. 16 17A working installation of zlib: 18Zlib 1.1.4 or 1.2.1.2 or greater (earlier 1.2.x versions have problems): 19http://www.gzip.org/zlib/ 20 21libcrypto from either of LibreSSL or OpenSSL. Building without libcrypto 22is supported but severely restricts the available ciphers and algorithms. 23 - LibreSSL (https://www.libressl.org/) 24 - OpenSSL (https://www.openssl.org) with any of the following versions: 25 - 1.0.x >= 1.0.1 or 1.1.0 >= 1.1.0g or any 1.1.1 26 27Note that due to a bug in EVP_CipherInit OpenSSL 1.1 versions prior to 281.1.0g can't be used. 29 30LibreSSL/OpenSSL 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. It requires that libcrypto be configured 48to support it. 49 50http://prngd.sourceforge.net/ 51 52EGD: 53 54The Entropy Gathering Daemon (EGD) supports the same interface as prngd. 55It also supported only if libcrypto is configured to support it. 56 57http://egd.sourceforge.net/ 58 59PAM: 60 61OpenSSH can utilise Pluggable Authentication Modules (PAM) if your 62system supports it. PAM is standard most Linux distributions, Solaris, 63HP-UX 11, AIX >= 5.2, FreeBSD, NetBSD and Mac OS X. 64 65Information about the various PAM implementations are available: 66 67Solaris PAM: http://www.sun.com/software/solaris/pam/ 68Linux PAM: http://www.kernel.org/pub/linux/libs/pam/ 69OpenPAM: http://www.openpam.org/ 70 71If you wish to build the GNOME passphrase requester, you will need the GNOME 72libraries and headers. 73 74GNOME: 75http://www.gnome.org/ 76 77Alternatively, Jim Knoble <jmknoble@pobox.com> has written an excellent X11 78passphrase requester. This is maintained separately at: 79 80http://www.jmknoble.net/software/x11-ssh-askpass/ 81 82TCP Wrappers: 83 84If you wish to use the TCP wrappers functionality you will need at least 85tcpd.h and libwrap.a, either in the standard include and library paths, 86or in the directory specified by --with-tcp-wrappers. Version 7.6 is 87known to work. 88 89http://ftp.porcupine.org/pub/security/index.html 90 91LibEdit: 92 93sftp supports command-line editing via NetBSD's libedit. If your platform 94has it available natively you can use that, alternatively you might try 95these multi-platform ports: 96 97http://www.thrysoee.dk/editline/ 98http://sourceforge.net/projects/libedit/ 99 100LDNS: 101 102LDNS is a DNS BSD-licensed resolver library which supports DNSSEC. 103 104http://nlnetlabs.nl/projects/ldns/ 105 106Autoconf: 107 108If you modify configure.ac or configure doesn't exist (eg if you checked 109the code out of git yourself) then you will need autoconf-2.69 and 110automake-1.16.1 to rebuild the automatically generated files by running 111"autoreconf". Earlier versions may also work but this is not guaranteed. 112 113http://www.gnu.org/software/autoconf/ 114http://www.gnu.org/software/automake/ 115 116Basic Security Module (BSM): 117 118Native BSM support is known to exist in Solaris from at least 2.5.1, 119FreeBSD 6.1 and OS X. Alternatively, you may use the OpenBSM 120implementation (http://www.openbsm.org). 121 122makedepend: 123 124https://www.x.org/archive/individual/util/ 125 126If you are making significant changes to the code you may need to rebuild 127the dependency (.depend) file using "make depend", which requires the 128"makedepend" tool from the X11 distribution. 129 130libfido2: 131 132libfido2 allows the use of hardware security keys over USB. libfido2 133in turn depends on libcbor. libfido2 >= 1.5.0 is strongly recommended. 134Limited functionality is possible with earlier libfido2 versions. 135 136https://github.com/Yubico/libfido2 137https://github.com/pjk/libcbor 138 139 1402. Building / Installation 141-------------------------- 142 143To install OpenSSH with default options: 144 145./configure 146make 147make install 148 149This will install the OpenSSH binaries in /usr/local/bin, configuration files 150in /usr/local/etc, the server in /usr/local/sbin, etc. To specify a different 151installation prefix, use the --prefix option to configure: 152 153./configure --prefix=/opt 154make 155make install 156 157Will install OpenSSH in /opt/{bin,etc,lib,sbin}. You can also override 158specific paths, for example: 159 160./configure --prefix=/opt --sysconfdir=/etc/ssh 161make 162make install 163 164This will install the binaries in /opt/{bin,lib,sbin}, but will place the 165configuration files in /etc/ssh. 166 167If you are using PAM, you may need to manually install a PAM control 168file as "/etc/pam.d/sshd" (or wherever your system prefers to keep 169them). Note that the service name used to start PAM is __progname, 170which is the basename of the path of your sshd (e.g., the service name 171for /usr/sbin/osshd will be osshd). If you have renamed your sshd 172executable, your PAM configuration may need to be modified. 173 174A generic PAM configuration is included as "contrib/sshd.pam.generic", 175you may need to edit it before using it on your system. If you are 176using a recent version of Red Hat Linux, the config file in 177contrib/redhat/sshd.pam should be more useful. Failure to install a 178valid PAM file may result in an inability to use password 179authentication. On HP-UX 11 and Solaris, the standard /etc/pam.conf 180configuration will work with sshd (sshd will match the other service 181name). 182 183There are a few other options to the configure script: 184 185--with-audit=[module] enable additional auditing via the specified module. 186Currently, drivers for "debug" (additional info via syslog) and "bsm" 187(Sun's Basic Security Module) are supported. 188 189--with-pam enables PAM support. If PAM support is compiled in, it must 190also be enabled in sshd_config (refer to the UsePAM directive). 191 192--with-prngd-socket=/some/file allows you to enable EGD or PRNGD 193support and to specify a PRNGd socket. Use this if your Unix lacks 194/dev/random. 195 196--with-prngd-port=portnum allows you to enable EGD or PRNGD support 197and to specify a EGD localhost TCP port. Use this if your Unix lacks 198/dev/random. 199 200--with-lastlog=FILE will specify the location of the lastlog file. 201./configure searches a few locations for lastlog, but may not find 202it if lastlog is installed in a different place. 203 204--without-lastlog will disable lastlog support entirely. 205 206--with-osfsia, --without-osfsia will enable or disable OSF1's Security 207Integration Architecture. The default for OSF1 machines is enable. 208 209--with-tcp-wrappers will enable TCP Wrappers (/etc/hosts.allow|deny) 210support. 211 212--with-utmpx enables utmpx support. utmpx support is automatic for 213some platforms. 214 215--without-shadow disables shadow password support. 216 217--with-ipaddr-display forces the use of a numeric IP address in the 218$DISPLAY environment variable. Some broken systems need this. 219 220--with-default-path=PATH allows you to specify a default $PATH for sessions 221started by sshd. This replaces the standard path entirely. 222 223--with-pid-dir=PATH specifies the directory in which the sshd.pid file is 224created. 225 226--with-xauth=PATH specifies the location of the xauth binary 227 228--with-ssl-dir=DIR allows you to specify where your Libre/OpenSSL 229libraries are installed. 230 231--with-ssl-engine enables Libre/OpenSSL's (hardware) ENGINE support 232 233--without-openssl builds without using OpenSSL. Only a subset of ciphers 234and algorithms are supported in this configuration. 235 236--without-zlib builds without zlib. This disables the Compression option. 237 238--with-4in6 Check for IPv4 in IPv6 mapped addresses and convert them to 239real (AF_INET) IPv4 addresses. Works around some quirks on Linux. 240 241If you need to pass special options to the compiler or linker, you 242can specify these as environment variables before running ./configure. 243For example: 244 245CC="/usr/foo/cc" CFLAGS="-O" LDFLAGS="-s" LIBS="-lrubbish" ./configure 246 2473. Configuration 248---------------- 249 250The runtime configuration files are installed by in ${prefix}/etc or 251whatever you specified as your --sysconfdir (/usr/local/etc by default). 252 253The default configuration should be instantly usable, though you should 254review it to ensure that it matches your security requirements. 255 256To generate a host key, run "make host-key". Alternately you can do so 257manually using the following commands: 258 259 ssh-keygen -t [type] -f /etc/ssh/ssh_host_key -N "" 260 261for each of the types you wish to generate (rsa, dsa or ecdsa) or 262 263 ssh-keygen -A 264 265to generate keys for all supported types. 266 267Replacing /etc/ssh with the correct path to the configuration directory. 268(${prefix}/etc or whatever you specified with --sysconfdir during 269configuration). 270 271If you have configured OpenSSH with EGD/prngd support, ensure that EGD or 272prngd is running and has collected some entropy first. 273 274For more information on configuration, please refer to the manual pages 275for sshd, ssh and ssh-agent. 276 2774. (Optional) Send survey 278------------------------- 279 280$ make survey 281[check the contents of the file "survey" to ensure there's no information 282that you consider sensitive] 283$ make send-survey 284 285This will send configuration information for the currently configured 286host to a survey address. This will help determine which configurations 287are actually in use, and what valid combinations of configure options 288exist. The raw data is available only to the OpenSSH developers, however 289summary data may be published. 290 2915. Problems? 292------------ 293 294If you experience problems compiling, installing or running OpenSSH, 295please refer to the "reporting bugs" section of the webpage at 296https://www.openssh.com/ 297