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This update gets it so 'lpr -r' ("remove the file after printing") will

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try to move the file from the source to the destination (spool) directory.
If that succeeds, much time and disk-space will be saved by doing that
instead of copying the entire file only to remove the original.  This
could be a big win on machines doing samba-service or CAP-based printing.

Note that this is about the fourth or fifth iteration of the patch, after
trying to address all possible security implications of the change.

PR:		16124
Reviewed by:	freebsd-current or freebsd-hackers (some time ago)
This commit is contained in:
Garance A Drosehn 2000-11-03 03:29:01 +00:00
parent 4b0ac46336
commit 4c4f66db72
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=68275
1 changed files with 79 additions and 0 deletions
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79
usr.sbin/lpr/lpr/lpr.c
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@ -133,7 +133,9 @@ main(argc, argv)
char *arg, *cp, *printer, *p;
char buf[BUFSIZ];
int c, i, f, errs;
int ret, didlink;
struct stat stb;
struct stat statb1, statb2;
struct printer myprinter, *pp = &myprinter;
printer = NULL;
@ -398,6 +400,83 @@ main(argc, argv)
}
if (sflag)
printf("%s: %s: not linked, copying instead\n", name, arg);
if (f) {
/*
* The user wants the file removed after it is copied
* to the spool area, so see if the file can be moved
* instead of copy/unlink'ed. This is much faster and
* uses less spool space than copying the file. This
* can be very significant when running services like
* samba, pcnfs, CAP, et al.
*/
seteuid(euid);
didlink = 0;
/*
* There are several things to check to avoid any
* security issues. Some of these are redundant
* under BSD's, but are necessary when lpr is built
* under some other OS's (which I do do...)
*/
if (lstat(arg, &statb1) < 0)
goto nohardlink;
if (S_ISLNK(statb1.st_mode))
goto nohardlink;
if (link(arg, dfname) != 0)
goto nohardlink;
didlink = 1;
/*
* Make sure the user hasn't tried to trick us via
* any race conditions
*/
if (lstat(dfname, &statb2) < 0)
goto nohardlink;
if (statb1.st_dev != statb2.st_dev)
goto nohardlink;
if (statb1.st_ino != statb2.st_ino)
goto nohardlink;
/*
* Skip if the file already had multiple hard links,
* because changing the owner and access-bits would
* change ALL versions of the file
*/
if (statb2.st_nlink > 2)
goto nohardlink;
/*
* If we can access and remove the original file
* without special setuid-ness then this method is
* safe. Otherwise, abandon the move and fall back
* to the (usual) copy method.
*/
seteuid(uid);
ret = access(dfname, R_OK);
if (ret == 0)
ret = unlink(arg);
seteuid(euid);
if (ret != 0)
goto nohardlink;
/*
* Unlink of user file was successful. Change the
* owner and permissions, add entries to the control
* file, and skip the file copying step.
*/
chown(dfname, pp->daemon_user, getegid());
chmod(dfname, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
seteuid(uid);
if (format == 'p')
card('T', title ? title : arg);
for (i = 0; i < ncopies; i++)
card(format, &dfname[inchar-2]);
card('U', &dfname[inchar-2]);
card('N', arg);
nact++;
continue;
nohardlink:
if (didlink)
unlink(dfname);
seteuid(uid); /* restore old uid */
} /* end: if (f) */
if ((i = open(arg, O_RDONLY)) < 0) {
printf("%s: cannot open %s\n", name, arg);
} else {