freebsd-nq/bin/rm/rm.c
Conrad Meyer 900c4ed3ca rm(1): Formalize non-functional status of -P flag
-P was introduced in 4.4BSD-Lite2 around 1994.  It overwrote file contents
with a pass of 0xff, 0x00, then 0xff, in a low effort attempt to "really
delete" files.

It has no user-visible effect; at the end of the day, the file is unlinked via
the filesystem.  Furthermore, the utility of overwriting files with patterned
data is extremely limited due to caveats at every layer of the stack[0] and
therefore mostly futile.  At the least, three passes is likely wasteful on
modern hardware[1].  It could also be seen as a violation of the "Unix
Philosophy" to do one thing per tiny, composable program.

Since 1994, FreeBSD has left it alone; OpenBSD replaced it with a single
pass of arc4random(3) output in 2012[2]; and NetBSD implemented partial, but
explicitly incomplete support for U.S. DoD 5220.22-M, "National Industrial
Security Program Operating Manual" in 2004[3].

NetBSD's enhanced comment above rm_overwrite makes a strong case for removing
the flag entirely:

> This is an expensive way to keep people from recovering files from your
> non-snapshotted FFS filesystems using fsdb(8).  Really.  No more.
>
> It is impossible to actually conform to the exact procedure given in
> [NISPOM] if one is overwriting a file, not an entire disk, because the
> procedure requires examination and comparison of the disk's defect lists.
> Any program that claims to securely erase *files* while conforming to the
> standard, then, is not correct.
>
> Furthermore, the presence of track caches, disk and controller write
> caches, and so forth make it extremely difficult to ensure that data have
> actually been written to the disk, particularly when one tries to repeatedly
> overwrite the same sectors in quick succession.  We call fsync(), but
> controllers with nonvolatile cache, as well as IDE disks that just plain lie
> about the stable storage of data, will defeat this.
>
> [NISPOM] requires physical media destruction, rather than any technique of
> the sort attempted here, for secret data.

As a first step towards evental removal, make it a placebo.  It's not like
it was serving any security function.  It is not defined in or mentioned by
POSIX.

If you are security conscious and need to erase your files, use a
woodchipper.  At a minimum, the entire disk needs to be overwritten, not
just one file.

[0]: https://www.ru.nl/publish/pages/909282/draft-paper.pdf
[1]: https://commons.erau.edu/cgi/viewcontent.cgi?article=1131&context=jdfsl
[2]: https://github.com/openbsd/src/commit/7c5c57ba81b5fe8ff2d4899ff643af18c
[3]: https://github.com/NetBSD/src/commit/fdf0a7a25e59af958fca1e2159921562cd

Reviewed by:	markj, Daniel O'Connor <darius AT dons.net.au> (previous version)
Differential Revision:	https://reviews.freebsd.org/D17906
2018-11-10 20:26:55 +00:00

553 lines
12 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1990, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if 0
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1990, 1993, 1994\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
static char sccsid[] = "@(#)rm.c 8.5 (Berkeley) 4/18/94";
#endif /* not lint */
#endif
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/stat.h>
#include <sys/param.h>
#include <sys/mount.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <fts.h>
#include <grp.h>
#include <locale.h>
#include <pwd.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>
static int dflag, eval, fflag, iflag, vflag, Wflag, stdin_ok;
static int rflag, Iflag, xflag;
static uid_t uid;
static volatile sig_atomic_t info;
static int check(const char *, const char *, struct stat *);
static int check2(char **);
static void checkdot(char **);
static void checkslash(char **);
static void rm_file(char **);
static void rm_tree(char **);
static void siginfo(int __unused);
static void usage(void);
/*
* rm --
* This rm is different from historic rm's, but is expected to match
* POSIX 1003.2 behavior. The most visible difference is that -f
* has two specific effects now, ignore non-existent files and force
* file removal.
*/
int
main(int argc, char *argv[])
{
int ch;
char *p;
(void)setlocale(LC_ALL, "");
/*
* Test for the special case where the utility is called as
* "unlink", for which the functionality provided is greatly
* simplified.
*/
if ((p = strrchr(argv[0], '/')) == NULL)
p = argv[0];
else
++p;
if (strcmp(p, "unlink") == 0) {
if (argc == 2)
rm_file(&argv[1]);
else if (argc == 3 && strcmp(argv[1], "--") == 0)
rm_file(&argv[2]);
else
usage();
exit(eval);
}
rflag = xflag = 0;
while ((ch = getopt(argc, argv, "dfiIPRrvWx")) != -1)
switch(ch) {
case 'd':
dflag = 1;
break;
case 'f':
fflag = 1;
iflag = 0;
break;
case 'i':
fflag = 0;
iflag = 1;
break;
case 'I':
Iflag = 1;
break;
case 'P':
/* Compatibility no-op. */
break;
case 'R':
case 'r': /* Compatibility. */
rflag = 1;
break;
case 'v':
vflag = 1;
break;
case 'W':
Wflag = 1;
break;
case 'x':
xflag = 1;
break;
default:
usage();
}
argc -= optind;
argv += optind;
if (argc < 1) {
if (fflag)
return (0);
usage();
}
checkdot(argv);
checkslash(argv);
uid = geteuid();
(void)signal(SIGINFO, siginfo);
if (*argv) {
stdin_ok = isatty(STDIN_FILENO);
if (Iflag) {
if (check2(argv) == 0)
exit (1);
}
if (rflag)
rm_tree(argv);
else
rm_file(argv);
}
exit (eval);
}
static void
rm_tree(char **argv)
{
FTS *fts;
FTSENT *p;
int needstat;
int flags;
int rval;
/*
* Remove a file hierarchy. If forcing removal (-f), or interactive
* (-i) or can't ask anyway (stdin_ok), don't stat the file.
*/
needstat = !uid || (!fflag && !iflag && stdin_ok);
/*
* If the -i option is specified, the user can skip on the pre-order
* visit. The fts_number field flags skipped directories.
*/
#define SKIPPED 1
flags = FTS_PHYSICAL;
if (!needstat)
flags |= FTS_NOSTAT;
if (Wflag)
flags |= FTS_WHITEOUT;
if (xflag)
flags |= FTS_XDEV;
if (!(fts = fts_open(argv, flags, NULL))) {
if (fflag && errno == ENOENT)
return;
err(1, "fts_open");
}
while ((p = fts_read(fts)) != NULL) {
switch (p->fts_info) {
case FTS_DNR:
if (!fflag || p->fts_errno != ENOENT) {
warnx("%s: %s",
p->fts_path, strerror(p->fts_errno));
eval = 1;
}
continue;
case FTS_ERR:
errx(1, "%s: %s", p->fts_path, strerror(p->fts_errno));
case FTS_NS:
/*
* Assume that since fts_read() couldn't stat the
* file, it can't be unlinked.
*/
if (!needstat)
break;
if (!fflag || p->fts_errno != ENOENT) {
warnx("%s: %s",
p->fts_path, strerror(p->fts_errno));
eval = 1;
}
continue;
case FTS_D:
/* Pre-order: give user chance to skip. */
if (!fflag && !check(p->fts_path, p->fts_accpath,
p->fts_statp)) {
(void)fts_set(fts, p, FTS_SKIP);
p->fts_number = SKIPPED;
}
else if (!uid &&
(p->fts_statp->st_flags & (UF_APPEND|UF_IMMUTABLE)) &&
!(p->fts_statp->st_flags & (SF_APPEND|SF_IMMUTABLE)) &&
lchflags(p->fts_accpath,
p->fts_statp->st_flags &= ~(UF_APPEND|UF_IMMUTABLE)) < 0)
goto err;
continue;
case FTS_DP:
/* Post-order: see if user skipped. */
if (p->fts_number == SKIPPED)
continue;
break;
default:
if (!fflag &&
!check(p->fts_path, p->fts_accpath, p->fts_statp))
continue;
}
rval = 0;
if (!uid &&
(p->fts_statp->st_flags & (UF_APPEND|UF_IMMUTABLE)) &&
!(p->fts_statp->st_flags & (SF_APPEND|SF_IMMUTABLE)))
rval = lchflags(p->fts_accpath,
p->fts_statp->st_flags &= ~(UF_APPEND|UF_IMMUTABLE));
if (rval == 0) {
/*
* If we can't read or search the directory, may still be
* able to remove it. Don't print out the un{read,search}able
* message unless the remove fails.
*/
switch (p->fts_info) {
case FTS_DP:
case FTS_DNR:
rval = rmdir(p->fts_accpath);
if (rval == 0 || (fflag && errno == ENOENT)) {
if (rval == 0 && vflag)
(void)printf("%s\n",
p->fts_path);
if (rval == 0 && info) {
info = 0;
(void)printf("%s\n",
p->fts_path);
}
continue;
}
break;
case FTS_W:
rval = undelete(p->fts_accpath);
if (rval == 0 && (fflag && errno == ENOENT)) {
if (vflag)
(void)printf("%s\n",
p->fts_path);
if (info) {
info = 0;
(void)printf("%s\n",
p->fts_path);
}
continue;
}
break;
case FTS_NS:
/*
* Assume that since fts_read() couldn't stat
* the file, it can't be unlinked.
*/
if (fflag)
continue;
/* FALLTHROUGH */
case FTS_F:
case FTS_NSOK:
default:
rval = unlink(p->fts_accpath);
if (rval == 0 || (fflag && errno == ENOENT)) {
if (rval == 0 && vflag)
(void)printf("%s\n",
p->fts_path);
if (rval == 0 && info) {
info = 0;
(void)printf("%s\n",
p->fts_path);
}
continue;
}
}
}
err:
warn("%s", p->fts_path);
eval = 1;
}
if (!fflag && errno)
err(1, "fts_read");
fts_close(fts);
}
static void
rm_file(char **argv)
{
struct stat sb;
int rval;
char *f;
/*
* Remove a file. POSIX 1003.2 states that, by default, attempting
* to remove a directory is an error, so must always stat the file.
*/
while ((f = *argv++) != NULL) {
/* Assume if can't stat the file, can't unlink it. */
if (lstat(f, &sb)) {
if (Wflag) {
sb.st_mode = S_IFWHT|S_IWUSR|S_IRUSR;
} else {
if (!fflag || errno != ENOENT) {
warn("%s", f);
eval = 1;
}
continue;
}
} else if (Wflag) {
warnx("%s: %s", f, strerror(EEXIST));
eval = 1;
continue;
}
if (S_ISDIR(sb.st_mode) && !dflag) {
warnx("%s: is a directory", f);
eval = 1;
continue;
}
if (!fflag && !S_ISWHT(sb.st_mode) && !check(f, f, &sb))
continue;
rval = 0;
if (!uid && !S_ISWHT(sb.st_mode) &&
(sb.st_flags & (UF_APPEND|UF_IMMUTABLE)) &&
!(sb.st_flags & (SF_APPEND|SF_IMMUTABLE)))
rval = lchflags(f, sb.st_flags & ~(UF_APPEND|UF_IMMUTABLE));
if (rval == 0) {
if (S_ISWHT(sb.st_mode))
rval = undelete(f);
else if (S_ISDIR(sb.st_mode))
rval = rmdir(f);
else
rval = unlink(f);
}
if (rval && (!fflag || errno != ENOENT)) {
warn("%s", f);
eval = 1;
}
if (vflag && rval == 0)
(void)printf("%s\n", f);
if (info && rval == 0) {
info = 0;
(void)printf("%s\n", f);
}
}
}
static int
check(const char *path, const char *name, struct stat *sp)
{
int ch, first;
char modep[15], *flagsp;
/* Check -i first. */
if (iflag)
(void)fprintf(stderr, "remove %s? ", path);
else {
/*
* If it's not a symbolic link and it's unwritable and we're
* talking to a terminal, ask. Symbolic links are excluded
* because their permissions are meaningless. Check stdin_ok
* first because we may not have stat'ed the file.
*/
if (!stdin_ok || S_ISLNK(sp->st_mode) ||
(!access(name, W_OK) &&
!(sp->st_flags & (SF_APPEND|SF_IMMUTABLE)) &&
(!(sp->st_flags & (UF_APPEND|UF_IMMUTABLE)) || !uid)))
return (1);
strmode(sp->st_mode, modep);
if ((flagsp = fflagstostr(sp->st_flags)) == NULL)
err(1, "fflagstostr");
(void)fprintf(stderr, "override %s%s%s/%s %s%sfor %s? ",
modep + 1, modep[10] == ' ' ? "" : " ",
user_from_uid(sp->st_uid, 0),
group_from_gid(sp->st_gid, 0),
*flagsp ? flagsp : "", *flagsp ? " " : "",
path);
free(flagsp);
}
(void)fflush(stderr);
first = ch = getchar();
while (ch != '\n' && ch != EOF)
ch = getchar();
return (first == 'y' || first == 'Y');
}
#define ISSLASH(a) ((a)[0] == '/' && (a)[1] == '\0')
static void
checkslash(char **argv)
{
char **t, **u;
int complained;
complained = 0;
for (t = argv; *t;) {
if (ISSLASH(*t)) {
if (!complained++)
warnx("\"/\" may not be removed");
eval = 1;
for (u = t; u[0] != NULL; ++u)
u[0] = u[1];
} else {
++t;
}
}
}
static int
check2(char **argv)
{
struct stat st;
int first;
int ch;
int fcount = 0;
int dcount = 0;
int i;
const char *dname = NULL;
for (i = 0; argv[i]; ++i) {
if (lstat(argv[i], &st) == 0) {
if (S_ISDIR(st.st_mode)) {
++dcount;
dname = argv[i]; /* only used if 1 dir */
} else {
++fcount;
}
}
}
first = 0;
while (first != 'n' && first != 'N' && first != 'y' && first != 'Y') {
if (dcount && rflag) {
fprintf(stderr, "recursively remove");
if (dcount == 1)
fprintf(stderr, " %s", dname);
else
fprintf(stderr, " %d dirs", dcount);
if (fcount == 1)
fprintf(stderr, " and 1 file");
else if (fcount > 1)
fprintf(stderr, " and %d files", fcount);
} else if (dcount + fcount > 3) {
fprintf(stderr, "remove %d files", dcount + fcount);
} else {
return(1);
}
fprintf(stderr, "? ");
fflush(stderr);
first = ch = getchar();
while (ch != '\n' && ch != EOF)
ch = getchar();
if (ch == EOF)
break;
}
return (first == 'y' || first == 'Y');
}
#define ISDOT(a) ((a)[0] == '.' && (!(a)[1] || ((a)[1] == '.' && !(a)[2])))
static void
checkdot(char **argv)
{
char *p, **save, **t;
int complained;
complained = 0;
for (t = argv; *t;) {
if ((p = strrchr(*t, '/')) != NULL)
++p;
else
p = *t;
if (ISDOT(p)) {
if (!complained++)
warnx("\".\" and \"..\" may not be removed");
eval = 1;
for (save = t; (t[0] = t[1]) != NULL; ++t)
continue;
t = save;
} else
++t;
}
}
static void
usage(void)
{
(void)fprintf(stderr, "%s\n%s\n",
"usage: rm [-f | -i] [-dIPRrvWx] file ...",
" unlink [--] file");
exit(EX_USAGE);
}
static void
siginfo(int sig __unused)
{
info = 1;
}