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Drop setuid status while doing file operations to prevent potential

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information leak.  This changeset is intended to be a minimal one
to make backports easier.

Reviewed by:	kevlo, remko
MFC after:	1 week
This commit is contained in:
Xin LI 2012-02-27 05:49:00 +00:00
parent 6e795141b2
commit cc427081a7
1 changed files with 21 additions and 12 deletions
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33
usr.sbin/cron/crontab/crontab.c
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@ -194,6 +194,17 @@ parse_args(argc, argv)
}
if (Option == opt_replace) {
/* relinquish the setuid status of the binary during
* the open, lest nonroot users read files they should
* not be able to read. we can't use access() here
* since there's a race condition. thanks go out to
* Arnt Gulbrandsen <agulbra@pvv.unit.no> for spotting
* the race.
*/
if (swap_uids() < OK)
err(ERROR_EXIT, "swapping uids");
/* we have to open the file here because we're going to
* chdir(2) into /var/cron before we get around to
* reading the file.
@ -204,21 +215,11 @@ parse_args(argc, argv)
!strcmp(resolved_path, SYSCRONTAB)) {
err(ERROR_EXIT, SYSCRONTAB " must be edited manually");
} else {
/* relinquish the setuid status of the binary during
* the open, lest nonroot users read files they should
* not be able to read. we can't use access() here
* since there's a race condition. thanks go out to
* Arnt Gulbrandsen <agulbra@pvv.unit.no> for spotting
* the race.
*/
if (swap_uids() < OK)
err(ERROR_EXIT, "swapping uids");
if (!(NewCrontab = fopen(Filename, "r")))
err(ERROR_EXIT, "%s", Filename);
if (swap_uids_back() < OK)
err(ERROR_EXIT, "swapping uids back");
}
if (swap_uids_back() < OK)
err(ERROR_EXIT, "swapping uids back");
}
Debug(DMISC, ("user=%s, file=%s, option=%s\n",
@ -363,11 +364,15 @@ edit_cmd() {
goto fatal;
}
again:
if (swap_uids() < OK)
err(ERROR_EXIT, "swapping uids");
if (stat(Filename, &statbuf) < 0) {
warn("stat");
fatal: unlink(Filename);
exit(ERROR_EXIT);
}
if (swap_uids_back() < OK)
err(ERROR_EXIT, "swapping uids back");
if (statbuf.st_dev != fsbuf.st_dev || statbuf.st_ino != fsbuf.st_ino)
errx(ERROR_EXIT, "temp file must be edited in place");
if (MD5File(Filename, orig_md5) == NULL) {
@ -433,6 +438,8 @@ edit_cmd() {
editor, WTERMSIG(waiter), WCOREDUMP(waiter) ?"" :"no ");
goto fatal;
}
if (swap_uids() < OK)
err(ERROR_EXIT, "swapping uids");
if (stat(Filename, &statbuf) < 0) {
warn("stat");
goto fatal;
@ -443,6 +450,8 @@ edit_cmd() {
warn("MD5");
goto fatal;
}
if (swap_uids_back() < OK)
err(ERROR_EXIT, "swapping uids back");
if (strcmp(orig_md5, new_md5) == 0 && !syntax_error) {
warnx("no changes made to crontab");
goto remove;