A change log of this software can be found at the end of this document. For announcements of updates, send mail to majordomo@wzv.win.tue.nl with as body (not subject): subscribe logdaemon-announce Report problems to: Wietse Venema (wietse@wzv.win.tue.nl) Eindhoven University of Technology Eindhoven, The Netherlands Warning: ======== Many programs in this kit replace system utilities. Don't replace system utilities unless you are an experienced system programmer and system administrator. I am using these programs daily on SunOS 4 and SunOS 5 systems, so I am pretty confident that they work well in these environments. Other plaforms that are supported to some extent: Ultrix 4, IRIX 5, HP-UX 9 and OSF 1 (Digital UNIX). However, I do not have root access on such systems so I unable to verify that the programs are really compatible with the ones that they replace. Introduction: ============= This archive contains the result of years of gradual transformations on BSD source. All code works with SunOS 4, SunOS 5 (Solaris), Ultrix 4.x and other BSD43/SYSV4 clones. In addition, the S/Key-ified parts work with IRIX 5.3, HP-UX 9.0, and Sony NewsOS 4.x; the login clone also reportedly works with Linux. There is a very good chance everything now also works with Digital UNIX, but I was unable to test this myself. (1) rsh and rlogin daemons that log the remote username and perform logging and access control in tcp/ip wrapper style. By default these daemons do not accept wildcards in hosts.equiv or .rhosts files. Both daemons have an '-l' option to disable user .rhosts files. The rshd optionally logs the user command (edit Makefile). The programs are more picky than usual about file permissions of .rhosts files: they must be owned by the user (or by the superuser), and they may not be group or world writable. (2) ftpd, rexecd and login software with fascist login failure logging and with optional support for S/Key one-time passwords. The rexecd daemon disallows root logins, once my favourite backdoor. The support for S/Key one-time passwords is optional, and completely invisible to users that do not need it. UNIX passwords are still permitted by default. A short description of how to use S/Key can be found in the skey subdirectory. Binaries for DOS and other systems can be found on thumper.bellcore.com. The rexecd optionally logs the user command (edit Makefile). (2a) ftpd and login software that supports the SecureNet card (code donated by William LeFebvre, Argonne National Laboratory). This software needs a DES library (for example, host ftp.psy.uq.oz.au directory /pub/Crypto/DES). See snk/README for more information. The code has been tested with SunOS 4.x and 5.x. (3) an S/Key login shell for sites that cannot replace the login program. Users first log into a password-less dummy account. The S/Key login shell prompts for their real account name and presents the corresponding S/Key challenge. The S/Key support uses the MD4 or MD5 hash function. The mode (MD4 by default, for backwards compatibility) is selected in skey/Makefile. The rshd and rlogind programs need the libwrap.a library that comes with recent (version >= 7.0) tcp/ip daemon wrapper implementations. In order to build rshd and rlogind you will have to do a setenv LOG_TCP /directory/with/libwrap.a Contents per directory: ======================= rlogind logging and access control in tcp wrapper style. Regular access is logged (by default) with priority daemon.info. Rejected access is logged with daemon.warn or more urgent. SunOS 4.x, SunOS 5.x and Ultrix 4.x. In order to use the "-l" (ignore user .rhosts files) option you will also need to install the login clone (see below). rshd logging and access control in tcp wrapper style. Regular access is logged (by default) with priority daemon.info. Logging of commands is a compile-time option (see the rshd/Makefile). Rejected access is logged with daemon.warn or more urgent. SunOS 4.x, SunOS 5.x and Ultrix 4.x. login hacked for SunOS 4.x, SunOS 5.x, with optional access control per (user,host) or per (user, tty); fbtab(5) security; fascist login failure logging. Regular logins are logged with priority auth.info, unusual or rejected logins with auth.notice. S/Key support. Can also be used with Ultrix 4.x for logins on non-graphics consoles. Appears to work with IRIX 5.3, HP-UX 9.0 and Linux (Slackware), NewsOS 4.x, Digital UNIX. rexecd Regular access is logged with priority daemon.info. Fascist login failure logging. Logging of commands is a compile-time option (see rexecd/Makefile). Rejected access is logged with auth.warn or more urgent. Access to the root account is prohibited. S/Key support. SunOS 4.x, SunOS 5.x and IRIX 5.3. Should also work with Ultrix. May work with HP-UX 9.0 and NewsOS 4.x, Digital UNIX. ftpd ftp daemon with fascist logging and login failure detection much like the login clone. Also logs anonymous ftp transfers. Tested with SunOS [45]. S/Key support. Should also work with Ultrix 4.x. May work with IRIX 5.3, HP-UX 9.0, NewsOS 4.x, Digital UNIX. telnetd pretty dumb BSD 4.3 telnetd. No access control or logging, but compatible with SunOS 4.x, Ultrix 4.x, SunOS 5.x. Relatively poor in features (no environment passing) so there is less risks of surprises. keysu NET/2 BSD su command ported back to SunOS 4.x, with S/Key support. Tested with FreeBSD and SunOS 4.1.3. May work with IRIX 5.3, HP-UX 9.0, NewsOS 4.x, Digital UNIX. skeysh An S/key login shell for sites that cannot replace the login program. The solution is to create a dummy account with skeysh as the login shell. skeysh is nothing but a stripped-down skey-only login program. People first log into the dummy account. This drops them into skeysh that prompts them for their real account name and presents the corresponding S/Key challenge. Tested with SunOS 4.1.3 and with Solaris 2.3 and IRIX 5.3. Should work anywhere the login clone works. lib additional routines used by login and by some daemons. Includes the ruserok() function that understands NIS, NFS (yuck) and that optionally skips user .rhosts files, and functions that mangle various UTMP file formats. skey Portions of S/Key source from thumper.bellcore.com, plus code that I hacked together myself. All bugs are my own. Edit the Makefile to choose between the MD4 or MD5 secure hash function. MD4 is default, for backwards compatibility. snk Code for the SecureNet card by William LeFebvre, Argonne National Laboratory). See snk/README for more information. Change log: =========== 901218 Fixed a problem with NOFLSH in login.c that caused interrupts to not flush the terminal input queue. 910209 Added per-user login access control. 911128 Added support to login for SunOS 4.x style /etc/fbtab, a table of devices whose protection and ownership is to be adjusted when a user logs in. 920609 Added tcp wrapper (log_tcp) style access control to rlogind and rshd. Improved the remote host name verification code. Added the LD_xxx environment fix to login. 920624 Login no longer just dies when the connection is broken, but first reports a login failure. This exposes an old cracker's trick. 921029 Ported to Ultrix 4.2. Most of the work was finding out why the login process did not have a controlling terminal. 921208 Ported to Solaris 2.0. rlogind can now work with the /bin/login that comes with most UNIXes. This was desirable because not everyone is in a position to replace /bin/login. Moreover, some SYSV logins can't even support the '-f' option at all (or everyone could login without a password). 2alpha version released. 921229 Tested with Solaris 2.1; some cleanups after looking at modified 4.4BSD sources from Charles Hedrick (hedrick@cs.rutgers.edu). The sources can be found on farside.rutgers.edu. 930103 Most of the sensible SYSV login features implemented. Frozen after check, check and double check. The source really suffered from porting and has become too ugly. It becomes a lot more readable after running through the unifdef program. Version 2beta released. 930119 Version 2 released after compatibility patches: rshd path; disabling the local domain stripping in login.c; cleanup utmpx file after rejecting an rlogin connection. 930221 Added group support to the login access control code, so that we can disallow off-site logins to wheel group members. Group matches work only for accounts that are explicitly listed in the group file: the matching is not based on group id values. 930222 Stole the code for the EXCEPT operator from the tcp wrapper. This, and the previous change, allows me to replace: # Disallow non-local logins into the wheel accounts +:foo bar baz:LOCAL .my.domain -:foo bar baz:ALL into the much easier to understand: -:wheel:ALL EXCEPT LOCAL .my.domain Assuming, of course, that the default is to permit access. 930331 Added per-program hints on how to configure syslogd. Added __svr4__ to the Solaris CFLAGS macro because the unbundled C compiler does not define it. 930925 Upped the number of ptys that telnetd and rlogind will attempt to open. The original versions would give up after 64 ptys. 930925 rshd now preserves TZ info when running under SunOS 5. We were too compatible with SunOS 5. 930925 login will now syslog() all regular logins, too. It took me too much time to examine individual wtmp files. 930929 Ultrix last minute patch to fix rshd environment handling. The fix must be ok for SunOS too but no time to verify this. 931206 With SunOS 5.x, Do not pass the "-p" option to login. 931212 Added logindevperm support for compatibility with SunOS 5.3. 931212 Added support to the login command for secure (DES) RPC (only for SunOS [45].x). This requires that the cleartext password be kept around until we have dropped privileges. Had to jump some hoops to prevent the program from ever dropping core with a cleartext password. 931212 Print error message when the login.access file exists but cannot be opened. 931225 Added S/Key support to login 'cause I was going on a trip. 931229 While on my trip, added S/Key support to ftpd. 940106 Woke up at 5am and realized there was a problem in my S/Key stuff. 940107 S/Key Solaris portability fixes from Douglas Lee Schales. 940110 Make sure that keyinit does not produce world-writable files. 940112 SysV4.0 wtmpx portability fixes from Baruch Cochavy. 940124 Fixed some ftpd and skey things that broke for Ultrix 4.x. 940125 Fix for Solaris uname(2) >0 return value. I fixed this before but somehow the change got misplaced. From Douglas Lee Schales. 940130 Made initial seed from skeyinit.c more random (use seconds instead of minutes). I managed to produce the same seed on multiple machines. The whole seed generation procedure sucks anyway: taking the first two letters of a host name. 940205 Made initial seed from skeyinit.c more random (use last 5 digits of current time in seconds). 940206 Fixed some login Makefile things that broke for Ultrix 4.x. 940206 Had some real fun with (argh) NIS+. The old BSD login code would blindly close all filedescriptors > 2 right AFTER it had processed the command-line options. I had to move the closing of open files right to the top of the main program. The reason for this is that all kinds of nisplus library routines secretly open sockets or files and keep them open forever. They get very upset when you unexpectedly close their open files. 940306 Finally got so disgusted from the BSD/SYSV #ifdefs that I began to clean up the login program. From now on we use POSIX instead of BSD/SYSV ifdefs. Many of my personal enhancements are no longer conditional. Ultrix misses some definitions so login won't compile there anymore. Kerberos code for login.c (John DiMarco ). 940312 Security feature: when S/Key decides whether UNIX passwords are ok, skip IP addresses listed for the remote host that appear to belong to someone else. Cleaned up the rlogind/telnetd code (POSIX interfaces instead of BSD/SYSV ifdefs). Changed the ftpd S/Key password prompt so that the MS-DOS `termkey' TSR can parse it. 940314 Cleaned up the ftpd code (POSIX interfaces instead of BSD/SYSV ifdefs). Ultrix misses some definitions so ftpd won't compile there anymore. All code now compiles and works on freebsd, which has become my development platform while traveling. The code compiles OK on an Indy running IRIX 5.something: just pretend to be sunos5. 940317 The telnetd/login programs no longer assume 7 or 8 bits, but leave CS7/CS8 tty settings alone. 940321 Modern rloginds seem to prefer 8-bit clean settings, so we force CS8 from now on. 940326 Our system administrator wanted netgroup support in the login access control file. This took only a few lines of code. A netgroup is written as @name, and can be used in host patterns and in user patterns. Included the keyinfo command and documentation, after getting rid of localisms. keyinit now restores the tty settings when it is interrupted. logdaemon-4.1.tar.Z released. 940426 Backwards compatibility code for Ultrix in login and ftpd. Added keysu (s/key su) command. This has little to do with daemon stuff but it just makes the package complete. This has been tested only with SunOS 4.x and FreeBSD. Unset FLUSHO in login.c, in case it helps. 940430 rexecd and rlogind now use the fd_set macros, to shut up the ANSI C compiler. converted net/2 su.1 man page to old -man macro style. William C. DenBesten asked for user@host patterns in the login access control files, so he could control many machines with just one set of rules. Fortunately, this took only a few lines of code. The hostpart is matched against the local host name. With user@host patterns and netgroups you can build impressive patterns such as @usergroup@@hostgroup. 940505 Peter Kossakowski (dfn cert) mentioned he usefulness of the -l option to ignore user .rhosts files. On most systems, the ruserok() library function have no support for that, so a modified version is provided. As a bonus, '+' wildcards are by default no longer accepted. Instead a loud complaint is sent to the syslogd. The programs must be compiled without -DNOPLUS to re-enable '+' wildcards. The -l option is supported by rshd, rlogind and by the login program (rlogind must pass on the -l option when the login program does the hosts.equiv/rhosts processing). Thus, in order to use -l you will have to replace both rlogind and login (and, of course, rshd). Most path names and syslog logging classes are now configurable from the Makefile. 940516 Fixed the README and released version 4.2. 940523 Just like the login program, the ftpd now tries to avoid dumping core with cleartext or encrypted (shadow) passwords. 940628 Generalized the format of the /etc/skey.access file so you can permit/deny UNIX passwords depending on user, tty and/or host. There is a new manual page, skey/skey.access.5 that documents this new format. 940718 Fixed another thing that broke with Ultrix: in lib/rcmd.c moved an #endif up to above the rresvport() routine. Now that you can specify what terminals are secure, the S/Key code has been modified to always permit UNIX passwords on the console. This saves you the embarrasment of having to break into your own machine. Alas, on some systems the console is not called /dev/console. Released version 4.3. 940908 Added -user and -host support to ruserok(). No-one complained sofar, but most systems document it. Looks like one feature that Berkeley dropped. HP-UX and BSDI support from Howard Chu for login, keysu and s/key. Replaced Howard's "vendor" #ifdefs by "feature" #ifdefs. (s/key) When built with -DSECURETTY, the keysu command will not accept the root password unless it is invoked from a secure terminal. Idea from Howard Chu. (s/key) "keyinit -s" would ask for counts up to 10000 but the actual limit is 9999 (Howard Chu). (s/key) Eliminated a possible localhost vs localhost.domain clash (Howard Chu). 940910 Collected system dependencies in one central file (sys_defs.h) and cleaned up the Makefiles. This may help when porting to other systems. 940911 After discussions with Guido van Rooij, documented several host name and address spoofing loopholes that may cause S/Key to permit UNIX passwords to unauthorized clients. 940914/5 Porting rexecd, ftpd, rlogind and telnetd to HP-UX 9.0 was not impossibly difficult. The effort may be useful to someone. 940917 Disabled the `site' extensions (umask, chmod) for ftp guest logins. 940922 Replaced the MD4 code by the byte-order independent versions from the NRL distribution on thumper.bellcore.com. MD4 is still the default. Edit skey/Makefile to switch to MD5. 941001 Idea from *Hobbit*: sites that cannot replace their login program create a dummy s/key account with as login shell a very much stripped-down skey-only login program. The skeysh program is my result of such an exercise. 941002 Cleaned up docs and comments. Released version 4.4. 941014 setenv() was missing an argument in skeysh/skeysh.c. This should not cause problems, but gcc barfs on it. sigh. 941022 Fixed pointer indirection level in lib/utmp_login.c. This would produce unpredictable results for HP-UX. 941105 Parametrized some hard-coded lengths for environment variables and fixed some rather short limits on username length. 941121 Changed the default console from /dev/console to none. This is more compatible with SysV (Kevin Davidson). 941121 Dropped ptyopen() etc. support for HP-UX. Having to support BSD and SYSV ptys is bad enough. 941126 It seems that assignments of static data to the environ variable may cause trouble on non-BSD systems. Instead of environ = envinit; execl(...); we no longer replace environ but truncate it and use putenv(): environ[0] = 0; putenv(...); 941127 On System V all daemons now preserve the complete initial environment. There were several reports of missing TZ values. I was unable to reproduce them with Solaris 2.3 and gcc. 941127 Fixed skey/skeylogin.c to look at more than just the first 8 characters of the login name. 941127 Fixed something in the skeysh/Makefile that broke on Ultrix. Released version 4.5. 941129 With Solaris 2.x, keysu would recognize '-' as a user name. This is due to getopt() incompatibilities. Fix: SysV su does not support options anyway, so drop the getopt loop. Reported by in1052@wlv.ac.uk (A.Parkes). 941129 Found another static assignment to environ in keysu.c. 941130 Should have used setenv() to set the user's path in keysu. Reported by Patrick Cipiere . 941209 With passive open, do not wait forever in accept(). Idea from casper@fwi.uva.nl in article <3asnqc$1h0@mail.fwi.uva.nl>. 941218 Changed rlogind and rshd to use the open-ended tcp wrapper 7.0 programmatic interface, so that banners can be used. 950101 Patches from David Mazieres: close redundant file descriptors in rshd and rexecd; workaround for broken HPUX setsid(); also, the HP-UX baud-rate codes differ from those on other platforms. 950101 Ftpd would send bare linefeeds when listing files over an ASCII-mode data connection, causing problems with wattcp clients (reported by Shou-Chuan Lai). 950108 Released 4.6, together with TCP wrappers 7.0. 950111 David Mazieres: HPUX cc is pickier than I expected. What's worse, they already define a struct request_info. Time for a horrible workaround. 950111 In S/Key passwords, accept commas instead of blanks, to work around stupid software that collapses blanks in passwords. 950121 Added SYSV shadow support to keysu (suggestion: Leif Hedstrom). 950213 skeyaccess could dereference a null pointer when host lookup failed (Larry J. Blunk @ Merit.edu). How embarrassing. 950222 Make ftpd try again when the data port bind() fails with EADDRINUSE. 950222 keysu did not strip the "/dev/" from the device name when looking for a secure terminal (Rob Liebschutz). Released 4.7. 950229 Oops. The securetty code in keysu looked at the wrong tty variable (Matthew Needes). 950308 Some Solaris applications may pass a '-' as username to /usr/bin/login (Kadlecsik Jozsi). 950321 Protected all environ[0]=0 assignments by a test if environ is nonzero. Ultrix daemons may have a null environment pointer, how bizarre. Paul Sijben helped me figure out this one. 950414 Oops. do_access() should call exit() not cleanup() (credits to Shou-Chuan Lai of National Tsing Hua University). 950422 Completed ULIMIT, UMASK and SLEEPTIME login default support. 950423 IRIX 5.3 support for s/key utilities and login/ftpd/rexecd. I still need to figure out what some IRIX login options do. Released 4.8. 950425 The login kerberos code had stopped working (David Mazieres). 950426 HPUX login now sets LOGNAME environment variable. 950428 Start of yet another series of S/Key code cleanups (Guido van Rooij, Tom Dunigan, some thrown in myself). 950429 Linux (Slackware) login fixes (Michael Brennen). 950430 IRIX problem: libnsl breaks NIS lookups (Tom Dunigan). 950430 IRIX now takes default user and root PATH from . 950430 More Linux (Slackware) login fixes (Michael Brennen). 950430 IRIX login now also sets REMOTEUSER. 950430 Folded in support for Sony NEWS-OS V4 (Jun-ichiro Itoh). 950430 Makefile cleanups: recursive make -n, intel outside. 950430 FreeBSD 2.0 workarounds (sys_errlist) so I can work on this code on my laptop while in the train. 950430 Made console device name configurable via sys_defs.h so that skeyaccess does the right thing with Linux. 950501 With HPUX, now use the system's getusershell() routines and don't link in the SYSV default routines when building skeysh. 950501 Implemented IRIX login default MAXTRYS (login attempt limit). Released 4.9. This release was expedited because of a file descriptor leak in my own S/Key glue routines. The leak could give logged-in users write access to s/key control files. 950502 The keyprint script (to print credit cards with s/key passwords) did not set PATH (Lionel Cons). 950622 FreeBSD needs linking with -lcrypt or you get a weaker crypt() algorithm. Now I can hack logdaemon while on the train. 950805 On systems with shadow passwords, rshd should not look at password fields from /etc/passwd (Peter A. Bigot). 950806 Ultrix login now displays the LAT port (Michael A. Crowley). 950807 Workaround for variadic functions on the alpha and other architectures where sizeof(int) < sizeof(pointer). Should change the code to use varargs/stdarg instead. 950812 Folded in the support for SecureNet keycards from William LeFebvre, Argonne National Laboratory. Presently, this is tested for SunOS 4/5 only, but probably works on everything else. 950812 Added my best guess for OSF1 (now Digital UNIX) system dependencies: late BSD-ish with SYSV utmp. 950812 The rexecd and rshd servers will log now user commands when compiled with -DLOG_COMMANDS (see Makefile). 950813 ftpd now closes unused passive ports, and rejects PORT requests that specify a privileged port or a third-party host (Hobbit). 950814 Removed unnecessary seteuid() calls in FTPD passive mode. 950815 FTPD Passive mode can now be forced to bind to ports in a specific window by doing, before make: setenv PASV_WINDOW "-DPASV_MIN_PORT=nn -DPASV_MAX_PORT=mm" 950826 With secure RPC, the user's password should be truncated to 8 characters (Kjell Hogstrom). 950930 Skeysh did not re-enable INT and QUIT signals (Jay Borkenhagen). 951001 Changed the skeyaccess() interface. The skey.access "group" now also matches the primary group ID. (Michael Aichlmayr). 951001 Code reorganization: system dependencies moved from Makefile to sys_defs.h, common files moved to lib directory. 951012 Removed a redundant ulimit() call in login.c and skeysh.c: it broke with a zero ulimit in /etc/default/login (Carson Gaspar). 951017 Skeysh now preserves the REMOTEUSER environment variable. 951020 Updated the ftpd manual page to reflect today's reality. 951021 Some HP-UX tty drivers still default to the @ and # line editing characters, and rely on the login program to sanitize them (Gordon Marler). The login program now fixes such ancient settings. 951021 Avoid potential problems by saving results from functions with volatile results such as inet_ntoa() and gethostby*(). With Solaris library routines doing their own hidden connection management, such library results become unreliable. 951024 Dropped some redundant code and declarations from rexecd. 951024 The rshd host name spoofing test was slightly broken. The program would dump core instead of logging the attack. I wonder how many treasures of this kind still lie buried in the BSD source code. 951024 ftpd now uses facility LOG_AUTH, just like rexec and login. 951024 While in the underseas tunnel between France and the UK, fixed an obscure s/key ftpd core dump that happens when the user sends no password. 951027 Updated the fixenv() environment stripper. 951028 System dependencies now trigger on hpux9 instead of hpux, so that we can more easily migrate to HP-UX 10. 951028 Added support for window size changes to the telnet daemon. This is about the only essential feature that I was missing. In the process fixed a bug in the telnet suboptions handling. Released 5.0 951029 The S/Key routines now syslog an error when they are unable to open the skeykeys file. Better be explicit than have people wonder why something did not work. 951030 Cleaned up the ftpd yacc grammar. The YACC stack is now a union so it no longer assigns pointer values to integers. 951124 Solaris 2.5 now needs _SVID_GETTOD (Frank Kaefer) or we have a function prototype conflict. 951201 In transfer logs, ftpd should not log the current directory when the remote user specifies an absolute path name. 951201 login_access() did not match primary groups (Dave Adamson). 960115 Work around for HPUX 9.x in case the client hostname is unknown (telnetd/rlogind pass the *server* address on the command line). 960115 In the Makefiles, osf1 changed to decosf1 to avoid confusion with OSF on Intel. 960115 Several DECOSF patches from Lawrence MacIntyre. 960115 keysu now logs the host from which the user is logged in (Marcus Schwartz). 960115 Now also logs file owner and permissions problems with .rhosts files instead of just refusing to use the file (Bob Beck). 960115 keysu now has the '-c command' option. 960115 Cleaned up some logging code in login (Chris Metcalf). 960213 Better HP-UX 9.x compatibility (Eric Backus). 960213 No "wheel" group restriction for "su root" for SYSV systems (except SunOS 5...). 960213 Ignore empty "wheel" groups (Chris Metcalf). 960226 Christophe Dorchies found an missing argument in a fatalperror() call in the rlogind program. 960308 UTMP fix for Digital-UNIX - it's not really a SYSV-UTMP system. 960308 Jean-Luc Szpyrka spotted an unitialized memory read in btoe(). 960314 SunOS 4 sets the LOGNAME environment variable, and so should we (Peter W. Osel @ Siemens). 960322 rlogind/rshd did not pass server name/address info to the tcpd library routines (Shou-Chuan Lai ). Released 5.1 960425 Made skeyaccess() robust against null user arguments (Cedomir Igaly ). 960518 keysu did not chek the return from getenv("TERM") (Henry Ptasinski) 960518 snk_crypt() left secrets behind in memory (Henry Ptasinski). Released 5.2 960616 Patches for the login program for Digital UNIX with enhanced security (Cedomir Igaly). Specify -DDECOSF1_ENHANCED to enable this and link with -lsecurity (see login/Makefile). 960616 Use the Digital UNIX utmp/wtmp routines instead of our own (Cedomir Igaly, Lawrence Macintyre). Released 5.3