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