From 40520b65fcfba963e90dfcffe87acd63a1760881 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@redhat.com>
Date: Tue, 26 Jan 2010 08:45:53 -0500
Subject: [PATCH 1/5] mount.cifs: directly include sys/stat.h in mtab.c
This file is mysteriously getting included when built via the makefile,
but when you try to build mtab.o by hand it fails to build. Directly
include it to remove any ambiguity.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
source3/client/mtab.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/source3/client/mtab.c b/source3/client/mtab.c
index 93fbd11..70789bc 100644
--- a/source3/client/mtab.c
+++ b/source3/client/mtab.c
@@ -32,6 +32,7 @@
#include <errno.h>
#include <stdio.h>
#include <sys/time.h>
+#include <sys/stat.h>
#include <time.h>
#include <fcntl.h>
#include <mntent.h>
--
1.6.6
From 59dd0bb8c8b46c875bcc8b55a6c22fee5ea2113b Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@redhat.com>
Date: Tue, 26 Jan 2010 08:45:57 -0500
Subject: [PATCH 2/5] mount.cifs: properly check for mount being in fstab when running setuid root (try#3)
This is the third attempt to clean up the checks when a setuid
mount.cifs is run by an unprivileged user. The main difference in this
patch from the last one is that it fixes a bug where the mount might
have failed if unnecessarily if CIFS_LEGACY_SETUID_CHECK was set.
When mount.cifs is installed setuid root and run as an unprivileged
user, it does some checks to limit how the mount is used. It checks that
the mountpoint is owned by the user doing the mount.
These checks however do not match those that /bin/mount does when it is
called by an unprivileged user. When /bin/mount is called by an
unprivileged user to do a mount, it checks that the mount in question is
in /etc/fstab, that it has the "user" option set, etc.
This means that it's currently not possible to set up user mounts the
standard way (by the admin, in /etc/fstab) and simultaneously protect
from an unprivileged user calling mount.cifs directly to mount a share
on any directory that that user owns.
Fix this by making the checks in mount.cifs match those of /bin/mount
itself. This is a necessary step to make mount.cifs safe to be installed
as a setuid binary, but not sufficient. For that, we'd need to give
mount.cifs a proper security audit.
Since some users may be depending on the legacy behavior, this patch
also adds the ability to build mount.cifs with the older behavior.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
source3/client/mount.cifs.c | 202 ++++++++++++++++++++++++++++++++++---------
1 files changed, 162 insertions(+), 40 deletions(-)
diff --git a/source3/client/mount.cifs.c b/source3/client/mount.cifs.c
index 43dc7f6..da2867c 100644
--- a/source3/client/mount.cifs.c
+++ b/source3/client/mount.cifs.c
@@ -39,10 +39,11 @@
#include <mntent.h>
#include <fcntl.h>
#include <limits.h>
+#include <fstab.h>
#include "mount.h"
#define MOUNT_CIFS_VERSION_MAJOR "1"
-#define MOUNT_CIFS_VERSION_MINOR "12"
+#define MOUNT_CIFS_VERSION_MINOR "13"
#ifndef MOUNT_CIFS_VENDOR_SUFFIX
#ifdef _SAMBA_BUILD_
@@ -69,6 +70,10 @@
#define MS_BIND 4096
#endif
+/* private flags - clear these before passing to kernel */
+#define MS_USERS 0x40000000
+#define MS_USER 0x80000000
+
#define MAX_UNC_LEN 1024
#define CONST_DISCARD(type, ptr) ((type) ((void *) (ptr)))
@@ -83,6 +88,27 @@
/* currently maximum length of IPv6 address string */
#define MAX_ADDRESS_LEN INET6_ADDRSTRLEN
+/*
+ * By default, mount.cifs follows the conventions set forth by /bin/mount
+ * for user mounts. That is, it requires that the mount be listed in
+ * /etc/fstab with the "user" option when run as an unprivileged user and
+ * mount.cifs is setuid root.
+ *
+ * Older versions of mount.cifs however were "looser" in this regard. When
+ * made setuid root, a user could run mount.cifs directly and mount any share
+ * on a directory owned by that user.
+ *
+ * The legacy behavior is now disabled by default. To reenable it, set the
+ * following #define to true.
+ */
+#define CIFS_LEGACY_SETUID_CHECK 0
+
+/*
+ * When an unprivileged user runs a setuid mount.cifs, we set certain mount
+ * flags by default. These defaults can be changed here.
+ */
+#define CIFS_SETUID_FLAGS (MS_NOSUID|MS_NODEV)
+
const char *thisprogram;
int verboseflag = 0;
int fakemnt = 0;
@@ -142,6 +168,99 @@ static size_t strlcat(char *d, const char *s, size_t bufsize)
}
#endif
+/*
+ * If an unprivileged user is doing the mounting then we need to ensure
+ * that the entry is in /etc/fstab.
+ */
+static int
+check_mountpoint(const char *progname, char *mountpoint)
+{
+ int err;
+ struct stat statbuf;
+
+ /* does mountpoint exist and is it a directory? */
+ err = stat(mountpoint, &statbuf);
+ if (err) {
+ fprintf(stderr, "%s: failed to stat %s: %s\n", progname,
+ mountpoint, strerror(errno));
+ return EX_USAGE;
+ }
+
+ if (!S_ISDIR(statbuf.st_mode)) {
+ fprintf(stderr, "%s: %s is not a directory!", progname,
+ mountpoint);
+ return EX_USAGE;
+ }
+
+#if CIFS_LEGACY_SETUID_CHECK
+ /* do extra checks on mountpoint for legacy setuid behavior */
+ if (!getuid() || geteuid())
+ return 0;
+
+ if (statbuf.st_uid != getuid()) {
+ fprintf(stderr, "%s: %s is not owned by user\n", progname,
+ mountpoint);
+ return EX_USAGE;
+ }
+
+ if ((statbuf.st_mode & S_IRWXU) != S_IRWXU) {
+ fprintf(stderr, "%s: invalid permissions on %s\n", progname,
+ mountpoint);
+ return EX_USAGE;
+ }
+#endif /* CIFS_LEGACY_SETUID_CHECK */
+
+ return 0;
+}
+
+#if CIFS_LEGACY_SETUID_CHECK
+static int
+check_fstab(const char *progname, char *mountpoint, char *devname,
+ char **options)
+{
+ return 0;
+}
+#else /* CIFS_LEGACY_SETUID_CHECK */
+static int
+check_fstab(const char *progname, char *mountpoint, char *devname,
+ char **options)
+{
+ FILE *fstab;
+ struct mntent *mnt;
+
+ /* make sure this mount is listed in /etc/fstab */
+ fstab = setmntent(_PATH_FSTAB, "r");
+ if (!fstab) {
+ fprintf(stderr, "Couldn't open %s for reading!\n",
+ _PATH_FSTAB);
+ return EX_FILEIO;
+ }
+
+ while((mnt = getmntent(fstab))) {
+ if (!strcmp(mountpoint, mnt->mnt_dir))
+ break;
+ }
+ endmntent(fstab);
+
+ if (mnt == NULL || strcmp(mnt->mnt_fsname, devname)) {
+ fprintf(stderr, "%s: permission denied: no match for "
+ "%s found in %s\n", progname, mountpoint,
+ _PATH_FSTAB);
+ return EX_USAGE;
+ }
+
+ /*
+ * 'mount' munges the options from fstab before passing them
+ * to us. It is non-trivial to test that we have the correct
+ * set of options. We don't want to trust what the user
+ * gave us, so just take whatever is in /etc/fstab.
+ */
+ free(*options);
+ *options = strdup(mnt->mnt_opts);
+ return 0;
+}
+#endif /* CIFS_LEGACY_SETUID_CHECK */
+
/* BB finish BB
cifs_umount
@@ -373,7 +492,7 @@ static int get_password_from_file(int file_descript, char * filename)
return rc;
}
-static int parse_options(char ** optionsp, int * filesys_flags)
+static int parse_options(char ** optionsp, unsigned long * filesys_flags)
{
const char * data;
char * percent_char = NULL;
@@ -423,6 +542,7 @@ static int parse_options(char ** optionsp, int * filesys_flags)
if (strncmp(data, "users",5) == 0) {
if(!value || !*value) {
+ *filesys_flags |= MS_USERS;
goto nocopy;
}
} else if (strncmp(data, "user_xattr",10) == 0) {
@@ -431,10 +551,7 @@ static int parse_options(char ** optionsp, int * filesys_flags)
if (!value || !*value) {
if(data[4] == '\0') {
- if(verboseflag)
- printf("\nskipping empty user mount parameter\n");
- /* remove the parm since it would otherwise be confusing
- to the kernel code which would think it was a real username */
+ *filesys_flags |= MS_USER;
goto nocopy;
} else {
printf("username specified with no parameter\n");
@@ -1046,7 +1163,7 @@ static void print_cifs_mount_version(void)
int main(int argc, char ** argv)
{
int c;
- int flags = MS_MANDLOCK; /* no need to set legacy MS_MGC_VAL */
+ unsigned long flags = MS_MANDLOCK;
char * orgoptions = NULL;
char * share_name = NULL;
const char * ipaddr = NULL;
@@ -1069,7 +1186,6 @@ int main(int argc, char ** argv)
size_t current_len;
int retry = 0; /* set when we have to retry mount with uppercase */
struct addrinfo *addrhead = NULL, *addr;
- struct stat statbuf;
struct utsname sysinfo;
struct mntent mountent;
struct sockaddr_in *addr4;
@@ -1127,8 +1243,8 @@ int main(int argc, char ** argv)
exit(EX_USAGE);
}
- /* add sharename in opts string as unc= parm */
+ /* add sharename in opts string as unc= parm */
while ((c = getopt_long (argc, argv, "afFhilL:no:O:rsSU:vVwt:",
longopts, NULL)) != -1) {
switch (c) {
@@ -1266,6 +1382,22 @@ int main(int argc, char ** argv)
exit(EX_USAGE);
}
+ /* make sure mountpoint is legit */
+ rc = check_mountpoint(thisprogram, mountpoint);
+ if (rc)
+ goto mount_exit;
+
+ /* sanity check for unprivileged mounts */
+ if (getuid()) {
+ rc = check_fstab(thisprogram, mountpoint, dev_name,
+ &orgoptions);
+ if (rc)
+ goto mount_exit;
+
+ /* enable any default user mount flags */
+ flags |= CIFS_SETUID_FLAGS;
+ }
+
if (getenv("PASSWD")) {
if(mountpassword == NULL)
mountpassword = (char *)calloc(MOUNT_PASSWD_SIZE+1,1);
@@ -1283,6 +1415,27 @@ int main(int argc, char ** argv)
rc = EX_USAGE;
goto mount_exit;
}
+
+ if (getuid()) {
+#if !CIFS_LEGACY_SETUID_CHECK
+ if (!(flags & (MS_USERS|MS_USER))) {
+ fprintf(stderr, "%s: permission denied\n", thisprogram);
+ rc = EX_USAGE;
+ goto mount_exit;
+ }
+#endif /* !CIFS_LEGACY_SETUID_CHECK */
+
+ if (geteuid()) {
+ fprintf(stderr, "%s: not installed setuid - \"user\" "
+ "CIFS mounts not supported.",
+ thisprogram);
+ rc = EX_FAIL;
+ goto mount_exit;
+ }
+ }
+
+ flags &= ~(MS_USERS|MS_USER);
+
addrhead = addr = parse_server(&share_name);
if((addrhead == NULL) && (got_ip == 0)) {
printf("No ip address specified and hostname not found\n");
@@ -1299,37 +1452,6 @@ int main(int argc, char ** argv)
mountpoint = resolved_path;
}
}
- if(chdir(mountpoint)) {
- printf("mount error: can not change directory into mount target %s\n",mountpoint);
- rc = EX_USAGE;
- goto mount_exit;
- }
-
- if(stat (".", &statbuf)) {
- printf("mount error: mount point %s does not exist\n",mountpoint);
- rc = EX_USAGE;
- goto mount_exit;
- }
-
- if (S_ISDIR(statbuf.st_mode) == 0) {
- printf("mount error: mount point %s is not a directory\n",mountpoint);
- rc = EX_USAGE;
- goto mount_exit;
- }
-
- if((getuid() != 0) && (geteuid() == 0)) {
- if((statbuf.st_uid == getuid()) && (S_IRWXU == (statbuf.st_mode & S_IRWXU))) {
-#ifndef CIFS_ALLOW_USR_SUID
- /* Do not allow user mounts to control suid flag
- for mount unless explicitly built that way */
- flags |= MS_NOSUID | MS_NODEV;
-#endif
- } else {
- printf("mount error: permission denied or not superuser and mount.cifs not installed SUID\n");
- exit(EX_USAGE);
- }
- }
-
if(got_user == 0) {
/* Note that the password will not be retrieved from the
USER env variable (ie user%password form) as there is
--
1.6.6
From a92fa34e73b988ca84fe15df6f67ea4879a6aa2e Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@redhat.com>
Date: Tue, 26 Jan 2010 08:45:58 -0500
Subject: [PATCH 3/5] mount.cifs: take extra care that mountpoint isn't changed during mount
It's possible to trick mount.cifs into mounting onto the wrong directory
by replacing the mountpoint with a symlink to a directory. mount.cifs
attempts to check the validity of the mountpoint, but there's still a
possible race between those checks and the mount(2) syscall.
To guard against this, chdir to the mountpoint very early, and only deal
with it as "." from then on out.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
source3/client/mount.cifs.c | 34 ++++++++++++++++++++++++++--------
1 files changed, 26 insertions(+), 8 deletions(-)
diff --git a/source3/client/mount.cifs.c b/source3/client/mount.cifs.c
index da2867c..53d1dad 100644
--- a/source3/client/mount.cifs.c
+++ b/source3/client/mount.cifs.c
@@ -179,7 +179,7 @@ check_mountpoint(const char *progname, char *mountpoint)
struct stat statbuf;
/* does mountpoint exist and is it a directory? */
- err = stat(mountpoint, &statbuf);
+ err = stat(".", &statbuf);
if (err) {
fprintf(stderr, "%s: failed to stat %s: %s\n", progname,
mountpoint, strerror(errno));
@@ -1383,6 +1383,14 @@ int main(int argc, char ** argv)
}
/* make sure mountpoint is legit */
+ rc = chdir(mountpoint);
+ if (rc) {
+ fprintf(stderr, "Couldn't chdir to %s: %s\n", mountpoint,
+ strerror(errno));
+ rc = EX_USAGE;
+ goto mount_exit;
+ }
+
rc = check_mountpoint(thisprogram, mountpoint);
if (rc)
goto mount_exit;
@@ -1445,13 +1453,23 @@ int main(int argc, char ** argv)
/* BB save off path and pop after mount returns? */
resolved_path = (char *)malloc(PATH_MAX+1);
- if(resolved_path) {
- /* Note that if we can not canonicalize the name, we get
- another chance to see if it is valid when we chdir to it */
- if (realpath(mountpoint, resolved_path)) {
- mountpoint = resolved_path;
- }
+ if (!resolved_path) {
+ fprintf(stderr, "Unable to allocate memory.\n");
+ rc = EX_SYSERR;
+ goto mount_exit;
}
+
+ /* Note that if we can not canonicalize the name, we get
+ another chance to see if it is valid when we chdir to it */
+ if(!realpath(".", resolved_path)) {
+ fprintf(stderr, "Unable to resolve %s to canonical path: %s\n",
+ mountpoint, strerror(errno));
+ rc = EX_SYSERR;
+ goto mount_exit;
+ }
+
+ mountpoint = resolved_path;
+
if(got_user == 0) {
/* Note that the password will not be retrieved from the
USER env variable (ie user%password form) as there is
@@ -1585,7 +1603,7 @@ mount_retry:
if (verboseflag)
fprintf(stderr, "\n");
- if (!fakemnt && mount(dev_name, mountpoint, "cifs", flags, options)) {
+ if (!fakemnt && mount(dev_name, ".", "cifs", flags, options)) {
switch (errno) {
case ECONNREFUSED:
case EHOSTUNREACH:
--
1.6.6
From bcdb9dc5d7daef6e93b742462e6dd056c0d1ed91 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@redhat.com>
Date: Tue, 26 Jan 2010 08:45:58 -0500
Subject: [PATCH 4/5] mount.cifs: check for invalid characters in device name and mountpoint
It's apparently possible to corrupt the mtab if you pass embedded
newlines to addmntent. Apparently tabs are also a problem with certain
earlier glibc versions. Backslashes are also a minor issue apparently,
but we can't reasonably filter those.
Make sure that neither the devname or mountpoint contain any problematic
characters before allowing the mount to proceed.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
source3/client/mount.cifs.c | 34 ++++++++++++++++++++++++++++++++++
1 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/source3/client/mount.cifs.c b/source3/client/mount.cifs.c
index 53d1dad..85be62b 100644
--- a/source3/client/mount.cifs.c
+++ b/source3/client/mount.cifs.c
@@ -1160,6 +1160,36 @@ static void print_cifs_mount_version(void)
MOUNT_CIFS_VENDOR_SUFFIX);
}
+/*
+ * This function borrowed from fuse-utils...
+ *
+ * glibc's addmntent (at least as of 2.10 or so) doesn't properly encode
+ * newlines embedded within the text fields. To make sure no one corrupts
+ * the mtab, fail the mount if there are embedded newlines.
+ */
+static int check_newline(const char *progname, const char *name)
+{
+ char *s;
+ for (s = "\n"; *s; s++) {
+ if (strchr(name, *s)) {
+ fprintf(stderr, "%s: illegal character 0x%02x in mount entry\n",
+ progname, *s);
+ return EX_USAGE;
+ }
+ }
+ return 0;
+}
+
+static int check_mtab(const char *progname, const char *devname,
+ const char *dir)
+{
+ if (check_newline(progname, devname) == -1 ||
+ check_newline(progname, dir) == -1)
+ return EX_USAGE;
+ return 0;
+}
+
+
int main(int argc, char ** argv)
{
int c;
@@ -1603,6 +1633,10 @@ mount_retry:
if (verboseflag)
fprintf(stderr, "\n");
+ rc = check_mtab(thisprogram, dev_name, mountpoint);
+ if (rc)
+ goto mount_exit;
+
if (!fakemnt && mount(dev_name, ".", "cifs", flags, options)) {
switch (errno) {
case ECONNREFUSED:
--
1.6.6
From ea8a30a9d217127eb2e5a0e0cd27d943cae7d13a Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@redhat.com>
Date: Tue, 26 Jan 2010 08:45:58 -0500
Subject: [PATCH 5/5] mount.cifs: don't allow it to be run as setuid root program
mount.cifs has been the subject of several "security" fire drills due to
distributions installing it as a setuid root program. This program has
not been properly audited for security and the Samba team highly
recommends that it not be installed as a setuid root program at this
time.
To make that abundantly clear, this patch forcibly disables the ability
for mount.cifs to run as a setuid root program. People are welcome to
trivially patch this out, but they do so at their own peril.
A security audit and redesign of this program is in progress and we hope
that we'll be able to remove this in the near future.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
source3/client/mount.cifs.c | 39 ++++++++++++++++++++++++++++++++++++++-
1 files changed, 38 insertions(+), 1 deletions(-)
diff --git a/source3/client/mount.cifs.c b/source3/client/mount.cifs.c
index 85be62b..f29e1e6 100644
--- a/source3/client/mount.cifs.c
+++ b/source3/client/mount.cifs.c
@@ -43,7 +43,7 @@
#include "mount.h"
#define MOUNT_CIFS_VERSION_MAJOR "1"
-#define MOUNT_CIFS_VERSION_MINOR "13"
+#define MOUNT_CIFS_VERSION_MINOR "14"
#ifndef MOUNT_CIFS_VENDOR_SUFFIX
#ifdef _SAMBA_BUILD_
@@ -89,6 +89,17 @@
#define MAX_ADDRESS_LEN INET6_ADDRSTRLEN
/*
+ * mount.cifs has been the subject of many "security" bugs that have arisen
+ * because of users and distributions installing it as a setuid root program.
+ * mount.cifs has not been audited for security. Thus, we strongly recommend
+ * that it not be installed setuid root. To make that abundantly clear,
+ * mount.cifs now check whether it's running setuid root and exit with an
+ * error if it is. If you wish to disable this check, then set the following
+ * #define to 1, but please realize that you do so at your own peril.
+ */
+#define CIFS_DISABLE_SETUID_CHECK 0
+
+/*
* By default, mount.cifs follows the conventions set forth by /bin/mount
* for user mounts. That is, it requires that the mount be listed in
* /etc/fstab with the "user" option when run as an unprivileged user and
@@ -213,6 +224,29 @@ check_mountpoint(const char *progname, char *mountpoint)
return 0;
}
+#if CIFS_DISABLE_SETUID_CHECK
+static int
+check_setuid(void)
+{
+ return 0;
+}
+#else /* CIFS_DISABLE_SETUID_CHECK */
+static int
+check_setuid(void)
+{
+ if (getuid() && !geteuid()) {
+ printf("This mount.cifs program has been built with the "
+ "ability to run as a setuid root program disabled.\n"
+ "mount.cifs has not been well audited for security "
+ "holes. Therefore the Samba team does not recommend "
+ "installing it as a setuid root program.\n");
+ return 1;
+ }
+
+ return 0;
+}
+#endif /* CIFS_DISABLE_SETUID_CHECK */
+
#if CIFS_LEGACY_SETUID_CHECK
static int
check_fstab(const char *progname, char *mountpoint, char *devname,
@@ -1222,6 +1256,9 @@ int main(int argc, char ** argv)
struct sockaddr_in6 *addr6;
FILE * pmntfile;
+ if (check_setuid())
+ return EX_USAGE;
+
/* setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE); */
--
1.6.6