1-------- 2 3Vixie Cron Changes from V2 to V3 4Paul Vixie 529-Dec-1993 6 7The crontab command now conforms to POSIX 1003.2. This means that when you 8install it, if you have any "crontab" command lines floating around in shell 9scripts (such as /etc/rc or /etc/rc.local), you will need to change them. 10 11I have integrated several changes made by BSDi for their BSD/386 operating 12system; these were offerred to me before I started consulting for them, so 13it is safe to say that they were intended for publication. Most notably, 14the name of the cron daemon has changed from "crond" to "cron". This was 15done for compatibility with 4.3BSD. Another change made for the same reason 16is the ability to read in an /etc/crontab file which has an extra field in 17each entry, between the time fields and the command. This field is a user 18name, and it permits the /etc/crontab command to contain commands which are 19to be run by any user on the system. /etc/crontab is not "installed" via 20the crontab(1) command; it is automatically read at startup time and it will 21be reread whenever it changes. 22 23I also added a "-e" option to crontab(1). Nine people also sent me diffs 24to add this option, but I had already implemented it on my own. I actually 25released an interim version (V2.2, I think) for limited testing, and got a 26chance to fix a bad security bug in the "-e" option thanks to XXX. 27 28The daemon used to be extraordinarily sloppy in its use of file descriptors. 29A heck of a lot of them were left open in spawned jobs, which caused problems 30for the daemon and also caused problems with the spawned jobs if they were 31shell scripts since "sh" and "csh" have traditionally used hidden file 32descriptors to pass information to subshells, and cron was causing them to 33think they were subshells. If you had trouble with "sh" or "csh" scripts in 34V2, chances are good that V3 will fix your problems. 35 36About a dozen people have reminded me that I forgot to initialize 37"crontab_fd" in database.c. Keith Cantrell was the first, so he gets the 38point. 39 40Steve Simmons reminded me that once an account has been deleted from the 41system, "crontab -u USER -d" will not work. My solution is to suggest to 42all of you that before you delete a user's account, you first delete that 43user's crontab file if any. From cron's point of view, usernames can never 44be treated as arbitrary strings. Either they are valid user names, or they 45are not. I will not make an exception for the "-d" case, for security 46reasons that I consider reasonable. It is trivial for a root user to delete 47the entry by hand if necessary. 48 49Dan O'Neil reminded me that I forgot to reset "log_fd" in misc.c. A lot of 50others also reminded me of this, but Dan gets the point. I didn't fix it 51there, since the real bug was that it should have been open in the parent. 52 53Peter Kabal reminded me that I forgot to "#ifdef DEBUGGING" some code in 54misc.c. Hans Trompert actually told me first, but Peter sent the patch so 55he gets the point. 56 57Russell Nelson told me that I'd forgotten to "#include <syslog.h>" in misc.c, 58which explains why a lot of other people complained that it wasn't using 59syslog even when they configured it that way :-). Steve Simmons told me 60first, though, so he gets the point. 61 62An interim version of the daemon tried to "stat" every file before 63executing it; this turned out to be a horribly bad idea since finding the 64name of a file from a shell command is a hard job (that's why we have 65shells, right?) I removed this bogus code. Dave Burgess gets the point. 66 67Dennis R. Conley sent a suggestion for MMDF systems, which I've added to the 68comments in cron.h. 69 70Mike Heisler noted that I use comments in the CONVERSION file which are 71documented as illegal in the man pages. Thanks, Mike. 72 73Irving Wolfe sent me some very cheerful changes for a NeXT system, but I 74consider the system itself broken and I can't bring myself to #ifdef for 75something as screwed up as this system seems to be. However, various others 76did send me smaller patches which appear to have cause cron to build and run 77correctly on (the latest) NeXT machines, with or without the "-posix" CFLAG. 78Irving also asked for a per-job MAILTO, and this was finally added later when 79I integrated the BSD/386 changes contributed by BSDi, and generalized some of 80the parsing. 81 82Lots of folks complained that the autogenerated "Date:" header wasn't in 83ARPA format. I didn't understand this -- either folks will use Sendmail and 84not generate a Date: at all (since Sendmail will do it), or folks will use 85something other than Sendmail which won't care about Date: formats. But 86I've "fixed" it anyway... 87 88Several people suggested that "*" should be able to take a "/step". One person 89suggested that "N/step" ought to mean "N-last/step", but that's stretching things 90a bit far. "*/step" seems quite intuitive to me, so I've added it. Colin Plumb 91sent in the first and most polite request for this feature. 92 93As with every release of Cron, BIND, and seemingly everything else I do, one 94user stands out with the most critical but also the most useful analysis. 95Cron V3's high score belongs to Peter Holzer, who sent in the nicest looking 96patch for the "%" interpretation problem and also helped me understand a 97tricky bit of badness in the "log_fd" problem. 98 99agulbra@flode.nvg.unit.no wins the honors for being the first to point out the 100nasty security hole in "crontab -r". 'Nuff said. 101 102Several folks pointed out that log_it() needed to exist even if logging was 103disabled. Some day I will create a tool that will compile a subsystem with 104every possible combination and permutation of #ifdef options, but meanwhile 105thanks to everybody. 106 107job_runqueue() was using storage after freeing it, since Jordan told me back 108in 1983 that C let you do that, and I believed him in 1986 when I wrote all 109this junk. Linux was the first to die from this error, and the Linux people 110sent me the most amazing, um, collection of patches for this problem. Thanks 111for all the fish. 112 113Jeremy Bettis reminded me that popen() isn't safe. I grabbed Ken Arnold's 114version of popen/pclose from the ftpd and hacked it to taste. We're safe now, 115from this at least. 116 117Branko Lankester sent me a very timely and helpful fix for a looming security 118problem in my "crontab -e" implementation. 119 120-------- 121 122Vixie Cron Changes from V1 to V2 123Paul Vixie 1248-Feb-1988 125 126Many changes were made in a rash of activity about six months ago, the exact 127list of which is no longer clear in my memory. I know that V1 used a file 128called POKECRON in /usr/spool/cron to tell it that it was time to re-read 129all the crontab files; V2 uses the modtime the crontab directory as a flag to 130check out the crontab files; those whose modtime has changed will be re-read, 131and the others left alone. Note that the crontab(1) command will do a utimes 132call to make sure the mtime of the dir changes, since the filename/inode will 133often remain the same after a replacement and the mtime wouldn't change in 134that case. 135 1368-Feb-88: made it possible to use much larger environment variable strings. 137 V1 allowed 100 characters; V2 allows 1000. This was needed for PATH 138 variables on some systems. Thanks to Toerless Eckert for this idea. 139 E-mail: UUCP: ...pyramid!fauern!faui10!eckert 140 14116-Feb-88: added allow/deny, moved /usr/spool/cron/crontabs to 142 /usr/lib/cron/tabs. allow and deny are /usr/lib/cron/{allow,deny}, 143 since the sysv naming for this depends on 'at' using the same 144 dir, which would be stupid (hint: use /usr/{lib,spool}/at). 145 14622-Feb-88: made it read the spool directory for crontabs and look each one 147 up using getpwnam() rather than reading all passwds with getpwent() 148 and trying to open each crontab. 149 1509-Dec-88: made it sync to :00 after the minute, makes cron predictable. 151 added logging to /var/cron/log. 152 15314-Apr-90: (actually, changes since December 1989) 154 fixed a number of bugs reported from the net and from John Gilmore. 155 added syslog per Keith Bostic. security features including not 156 being willing to run a command owned or writable by other than 157 the owner of the crontab 9not working well yet) 158