linux/fs/nfsd/nfsfh.c
J. Bruce Fields 9d7ed1355d nfsd: don't require low ports for gss requests
In a traditional NFS deployment using auth_unix, the clients are trusted
to correctly report the credentials of their logged-in users.  The
server assumes that only root on client machines is allowed to send
requests from low-numbered ports, so it can use the originating port
number to distinguish "real" NFS clients from NFS clients run by
ordinary users, to prevent ordinary users from spoofing credentials.

The originating port number on a gss-authenticated request is less
important.  The authentication ties the request to a user, and we take
it as proof that that user authorized the request.  The low port number
check no longer adds much.

So, don't enforce low port numbers in the auth_gss case.

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
2018-03-19 16:38:13 -04:00

707 lines
18 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* NFS server file handle treatment.
*
* Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
* Portions Copyright (C) 1999 G. Allen Morris III <gam3@acm.org>
* Extensive rewrite by Neil Brown <neilb@cse.unsw.edu.au> Southern-Spring 1999
* ... and again Southern-Winter 2001 to support export_operations
*/
#include <linux/exportfs.h>
#include <linux/sunrpc/svcauth_gss.h>
#include "nfsd.h"
#include "vfs.h"
#include "auth.h"
#define NFSDDBG_FACILITY NFSDDBG_FH
/*
* our acceptability function.
* if NOSUBTREECHECK, accept anything
* if not, require that we can walk up to exp->ex_dentry
* doing some checks on the 'x' bits
*/
static int nfsd_acceptable(void *expv, struct dentry *dentry)
{
struct svc_export *exp = expv;
int rv;
struct dentry *tdentry;
struct dentry *parent;
if (exp->ex_flags & NFSEXP_NOSUBTREECHECK)
return 1;
tdentry = dget(dentry);
while (tdentry != exp->ex_path.dentry && !IS_ROOT(tdentry)) {
/* make sure parents give x permission to user */
int err;
parent = dget_parent(tdentry);
err = inode_permission(d_inode(parent), MAY_EXEC);
if (err < 0) {
dput(parent);
break;
}
dput(tdentry);
tdentry = parent;
}
if (tdentry != exp->ex_path.dentry)
dprintk("nfsd_acceptable failed at %p %pd\n", tdentry, tdentry);
rv = (tdentry == exp->ex_path.dentry);
dput(tdentry);
return rv;
}
/* Type check. The correct error return for type mismatches does not seem to be
* generally agreed upon. SunOS seems to use EISDIR if file isn't S_IFREG; a
* comment in the NFSv3 spec says this is incorrect (implementation notes for
* the write call).
*/
static inline __be32
nfsd_mode_check(struct svc_rqst *rqstp, struct dentry *dentry,
umode_t requested)
{
umode_t mode = d_inode(dentry)->i_mode & S_IFMT;
if (requested == 0) /* the caller doesn't care */
return nfs_ok;
if (mode == requested) {
if (mode == S_IFDIR && !d_can_lookup(dentry)) {
WARN_ON_ONCE(1);
return nfserr_notdir;
}
return nfs_ok;
}
/*
* v4 has an error more specific than err_notdir which we should
* return in preference to err_notdir:
*/
if (rqstp->rq_vers == 4 && mode == S_IFLNK)
return nfserr_symlink;
if (requested == S_IFDIR)
return nfserr_notdir;
if (mode == S_IFDIR)
return nfserr_isdir;
return nfserr_inval;
}
static bool nfsd_originating_port_ok(struct svc_rqst *rqstp, int flags)
{
if (flags & NFSEXP_INSECURE_PORT)
return true;
/* We don't require gss requests to use low ports: */
if (rqstp->rq_cred.cr_flavor >= RPC_AUTH_GSS)
return true;
return test_bit(RQ_SECURE, &rqstp->rq_flags);
}
static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp,
struct svc_export *exp)
{
int flags = nfsexp_flags(rqstp, exp);
/* Check if the request originated from a secure port. */
if (!nfsd_originating_port_ok(rqstp, flags)) {
RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
dprintk("nfsd: request from insecure port %s!\n",
svc_print_addr(rqstp, buf, sizeof(buf)));
return nfserr_perm;
}
/* Set user creds for this exportpoint */
return nfserrno(nfsd_setuser(rqstp, exp));
}
static inline __be32 check_pseudo_root(struct svc_rqst *rqstp,
struct dentry *dentry, struct svc_export *exp)
{
if (!(exp->ex_flags & NFSEXP_V4ROOT))
return nfs_ok;
/*
* v2/v3 clients have no need for the V4ROOT export--they use
* the mount protocl instead; also, further V4ROOT checks may be
* in v4-specific code, in which case v2/v3 clients could bypass
* them.
*/
if (!nfsd_v4client(rqstp))
return nfserr_stale;
/*
* We're exposing only the directories and symlinks that have to be
* traversed on the way to real exports:
*/
if (unlikely(!d_is_dir(dentry) &&
!d_is_symlink(dentry)))
return nfserr_stale;
/*
* A pseudoroot export gives permission to access only one
* single directory; the kernel has to make another upcall
* before granting access to anything else under it:
*/
if (unlikely(dentry != exp->ex_path.dentry))
return nfserr_stale;
return nfs_ok;
}
/*
* Use the given filehandle to look up the corresponding export and
* dentry. On success, the results are used to set fh_export and
* fh_dentry.
*/
static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
{
struct knfsd_fh *fh = &fhp->fh_handle;
struct fid *fid = NULL, sfid;
struct svc_export *exp;
struct dentry *dentry;
int fileid_type;
int data_left = fh->fh_size/4;
__be32 error;
error = nfserr_stale;
if (rqstp->rq_vers > 2)
error = nfserr_badhandle;
if (rqstp->rq_vers == 4 && fh->fh_size == 0)
return nfserr_nofilehandle;
if (fh->fh_version == 1) {
int len;
if (--data_left < 0)
return error;
if (fh->fh_auth_type != 0)
return error;
len = key_len(fh->fh_fsid_type) / 4;
if (len == 0)
return error;
if (fh->fh_fsid_type == FSID_MAJOR_MINOR) {
/* deprecated, convert to type 3 */
len = key_len(FSID_ENCODE_DEV)/4;
fh->fh_fsid_type = FSID_ENCODE_DEV;
/*
* struct knfsd_fh uses host-endian fields, which are
* sometimes used to hold net-endian values. This
* confuses sparse, so we must use __force here to
* keep it from complaining.
*/
fh->fh_fsid[0] = new_encode_dev(MKDEV(ntohl((__force __be32)fh->fh_fsid[0]),
ntohl((__force __be32)fh->fh_fsid[1])));
fh->fh_fsid[1] = fh->fh_fsid[2];
}
data_left -= len;
if (data_left < 0)
return error;
exp = rqst_exp_find(rqstp, fh->fh_fsid_type, fh->fh_fsid);
fid = (struct fid *)(fh->fh_fsid + len);
} else {
__u32 tfh[2];
dev_t xdev;
ino_t xino;
if (fh->fh_size != NFS_FHSIZE)
return error;
/* assume old filehandle format */
xdev = old_decode_dev(fh->ofh_xdev);
xino = u32_to_ino_t(fh->ofh_xino);
mk_fsid(FSID_DEV, tfh, xdev, xino, 0, NULL);
exp = rqst_exp_find(rqstp, FSID_DEV, tfh);
}
error = nfserr_stale;
if (PTR_ERR(exp) == -ENOENT)
return error;
if (IS_ERR(exp))
return nfserrno(PTR_ERR(exp));
if (exp->ex_flags & NFSEXP_NOSUBTREECHECK) {
/* Elevate privileges so that the lack of 'r' or 'x'
* permission on some parent directory will
* not stop exportfs_decode_fh from being able
* to reconnect a directory into the dentry cache.
* The same problem can affect "SUBTREECHECK" exports,
* but as nfsd_acceptable depends on correct
* access control settings being in effect, we cannot
* fix that case easily.
*/
struct cred *new = prepare_creds();
if (!new) {
error = nfserrno(-ENOMEM);
goto out;
}
new->cap_effective =
cap_raise_nfsd_set(new->cap_effective,
new->cap_permitted);
put_cred(override_creds(new));
put_cred(new);
} else {
error = nfsd_setuser_and_check_port(rqstp, exp);
if (error)
goto out;
}
/*
* Look up the dentry using the NFS file handle.
*/
error = nfserr_stale;
if (rqstp->rq_vers > 2)
error = nfserr_badhandle;
if (fh->fh_version != 1) {
sfid.i32.ino = fh->ofh_ino;
sfid.i32.gen = fh->ofh_generation;
sfid.i32.parent_ino = fh->ofh_dirino;
fid = &sfid;
data_left = 3;
if (fh->ofh_dirino == 0)
fileid_type = FILEID_INO32_GEN;
else
fileid_type = FILEID_INO32_GEN_PARENT;
} else
fileid_type = fh->fh_fileid_type;
if (fileid_type == FILEID_ROOT)
dentry = dget(exp->ex_path.dentry);
else {
dentry = exportfs_decode_fh(exp->ex_path.mnt, fid,
data_left, fileid_type,
nfsd_acceptable, exp);
}
if (dentry == NULL)
goto out;
if (IS_ERR(dentry)) {
if (PTR_ERR(dentry) != -EINVAL)
error = nfserrno(PTR_ERR(dentry));
goto out;
}
if (d_is_dir(dentry) &&
(dentry->d_flags & DCACHE_DISCONNECTED)) {
printk("nfsd: find_fh_dentry returned a DISCONNECTED directory: %pd2\n",
dentry);
}
fhp->fh_dentry = dentry;
fhp->fh_export = exp;
return 0;
out:
exp_put(exp);
return error;
}
/**
* fh_verify - filehandle lookup and access checking
* @rqstp: pointer to current rpc request
* @fhp: filehandle to be verified
* @type: expected type of object pointed to by filehandle
* @access: type of access needed to object
*
* Look up a dentry from the on-the-wire filehandle, check the client's
* access to the export, and set the current task's credentials.
*
* Regardless of success or failure of fh_verify(), fh_put() should be
* called on @fhp when the caller is finished with the filehandle.
*
* fh_verify() may be called multiple times on a given filehandle, for
* example, when processing an NFSv4 compound. The first call will look
* up a dentry using the on-the-wire filehandle. Subsequent calls will
* skip the lookup and just perform the other checks and possibly change
* the current task's credentials.
*
* @type specifies the type of object expected using one of the S_IF*
* constants defined in include/linux/stat.h. The caller may use zero
* to indicate that it doesn't care, or a negative integer to indicate
* that it expects something not of the given type.
*
* @access is formed from the NFSD_MAY_* constants defined in
* fs/nfsd/vfs.h.
*/
__be32
fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type, int access)
{
struct svc_export *exp;
struct dentry *dentry;
__be32 error;
dprintk("nfsd: fh_verify(%s)\n", SVCFH_fmt(fhp));
if (!fhp->fh_dentry) {
error = nfsd_set_fh_dentry(rqstp, fhp);
if (error)
goto out;
}
dentry = fhp->fh_dentry;
exp = fhp->fh_export;
/*
* We still have to do all these permission checks, even when
* fh_dentry is already set:
* - fh_verify may be called multiple times with different
* "access" arguments (e.g. nfsd_proc_create calls
* fh_verify(...,NFSD_MAY_EXEC) first, then later (in
* nfsd_create) calls fh_verify(...,NFSD_MAY_CREATE).
* - in the NFSv4 case, the filehandle may have been filled
* in by fh_compose, and given a dentry, but further
* compound operations performed with that filehandle
* still need permissions checks. In the worst case, a
* mountpoint crossing may have changed the export
* options, and we may now need to use a different uid
* (for example, if different id-squashing options are in
* effect on the new filesystem).
*/
error = check_pseudo_root(rqstp, dentry, exp);
if (error)
goto out;
error = nfsd_setuser_and_check_port(rqstp, exp);
if (error)
goto out;
error = nfsd_mode_check(rqstp, dentry, type);
if (error)
goto out;
/*
* pseudoflavor restrictions are not enforced on NLM,
* which clients virtually always use auth_sys for,
* even while using RPCSEC_GSS for NFS.
*/
if (access & NFSD_MAY_LOCK || access & NFSD_MAY_BYPASS_GSS)
goto skip_pseudoflavor_check;
/*
* Clients may expect to be able to use auth_sys during mount,
* even if they use gss for everything else; see section 2.3.2
* of rfc 2623.
*/
if (access & NFSD_MAY_BYPASS_GSS_ON_ROOT
&& exp->ex_path.dentry == dentry)
goto skip_pseudoflavor_check;
error = check_nfsd_access(exp, rqstp);
if (error)
goto out;
skip_pseudoflavor_check:
/* Finally, check access permissions. */
error = nfsd_permission(rqstp, exp, dentry, access);
if (error) {
dprintk("fh_verify: %pd2 permission failure, "
"acc=%x, error=%d\n",
dentry,
access, ntohl(error));
}
out:
if (error == nfserr_stale)
nfsdstats.fh_stale++;
return error;
}
/*
* Compose a file handle for an NFS reply.
*
* Note that when first composed, the dentry may not yet have
* an inode. In this case a call to fh_update should be made
* before the fh goes out on the wire ...
*/
static void _fh_update(struct svc_fh *fhp, struct svc_export *exp,
struct dentry *dentry)
{
if (dentry != exp->ex_path.dentry) {
struct fid *fid = (struct fid *)
(fhp->fh_handle.fh_fsid + fhp->fh_handle.fh_size/4 - 1);
int maxsize = (fhp->fh_maxsize - fhp->fh_handle.fh_size)/4;
int subtreecheck = !(exp->ex_flags & NFSEXP_NOSUBTREECHECK);
fhp->fh_handle.fh_fileid_type =
exportfs_encode_fh(dentry, fid, &maxsize, subtreecheck);
fhp->fh_handle.fh_size += maxsize * 4;
} else {
fhp->fh_handle.fh_fileid_type = FILEID_ROOT;
}
}
/*
* for composing old style file handles
*/
static inline void _fh_update_old(struct dentry *dentry,
struct svc_export *exp,
struct knfsd_fh *fh)
{
fh->ofh_ino = ino_t_to_u32(d_inode(dentry)->i_ino);
fh->ofh_generation = d_inode(dentry)->i_generation;
if (d_is_dir(dentry) ||
(exp->ex_flags & NFSEXP_NOSUBTREECHECK))
fh->ofh_dirino = 0;
}
static bool is_root_export(struct svc_export *exp)
{
return exp->ex_path.dentry == exp->ex_path.dentry->d_sb->s_root;
}
static struct super_block *exp_sb(struct svc_export *exp)
{
return exp->ex_path.dentry->d_sb;
}
static bool fsid_type_ok_for_exp(u8 fsid_type, struct svc_export *exp)
{
switch (fsid_type) {
case FSID_DEV:
if (!old_valid_dev(exp_sb(exp)->s_dev))
return 0;
/* FALL THROUGH */
case FSID_MAJOR_MINOR:
case FSID_ENCODE_DEV:
return exp_sb(exp)->s_type->fs_flags & FS_REQUIRES_DEV;
case FSID_NUM:
return exp->ex_flags & NFSEXP_FSID;
case FSID_UUID8:
case FSID_UUID16:
if (!is_root_export(exp))
return 0;
/* fall through */
case FSID_UUID4_INUM:
case FSID_UUID16_INUM:
return exp->ex_uuid != NULL;
}
return 1;
}
static void set_version_and_fsid_type(struct svc_fh *fhp, struct svc_export *exp, struct svc_fh *ref_fh)
{
u8 version;
u8 fsid_type;
retry:
version = 1;
if (ref_fh && ref_fh->fh_export == exp) {
version = ref_fh->fh_handle.fh_version;
fsid_type = ref_fh->fh_handle.fh_fsid_type;
ref_fh = NULL;
switch (version) {
case 0xca:
fsid_type = FSID_DEV;
break;
case 1:
break;
default:
goto retry;
}
/*
* As the fsid -> filesystem mapping was guided by
* user-space, there is no guarantee that the filesystem
* actually supports that fsid type. If it doesn't we
* loop around again without ref_fh set.
*/
if (!fsid_type_ok_for_exp(fsid_type, exp))
goto retry;
} else if (exp->ex_flags & NFSEXP_FSID) {
fsid_type = FSID_NUM;
} else if (exp->ex_uuid) {
if (fhp->fh_maxsize >= 64) {
if (is_root_export(exp))
fsid_type = FSID_UUID16;
else
fsid_type = FSID_UUID16_INUM;
} else {
if (is_root_export(exp))
fsid_type = FSID_UUID8;
else
fsid_type = FSID_UUID4_INUM;
}
} else if (!old_valid_dev(exp_sb(exp)->s_dev))
/* for newer device numbers, we must use a newer fsid format */
fsid_type = FSID_ENCODE_DEV;
else
fsid_type = FSID_DEV;
fhp->fh_handle.fh_version = version;
if (version)
fhp->fh_handle.fh_fsid_type = fsid_type;
}
__be32
fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry,
struct svc_fh *ref_fh)
{
/* ref_fh is a reference file handle.
* if it is non-null and for the same filesystem, then we should compose
* a filehandle which is of the same version, where possible.
* Currently, that means that if ref_fh->fh_handle.fh_version == 0xca
* Then create a 32byte filehandle using nfs_fhbase_old
*
*/
struct inode * inode = d_inode(dentry);
dev_t ex_dev = exp_sb(exp)->s_dev;
dprintk("nfsd: fh_compose(exp %02x:%02x/%ld %pd2, ino=%ld)\n",
MAJOR(ex_dev), MINOR(ex_dev),
(long) d_inode(exp->ex_path.dentry)->i_ino,
dentry,
(inode ? inode->i_ino : 0));
/* Choose filehandle version and fsid type based on
* the reference filehandle (if it is in the same export)
* or the export options.
*/
set_version_and_fsid_type(fhp, exp, ref_fh);
if (ref_fh == fhp)
fh_put(ref_fh);
if (fhp->fh_locked || fhp->fh_dentry) {
printk(KERN_ERR "fh_compose: fh %pd2 not initialized!\n",
dentry);
}
if (fhp->fh_maxsize < NFS_FHSIZE)
printk(KERN_ERR "fh_compose: called with maxsize %d! %pd2\n",
fhp->fh_maxsize,
dentry);
fhp->fh_dentry = dget(dentry); /* our internal copy */
fhp->fh_export = exp_get(exp);
if (fhp->fh_handle.fh_version == 0xca) {
/* old style filehandle please */
memset(&fhp->fh_handle.fh_base, 0, NFS_FHSIZE);
fhp->fh_handle.fh_size = NFS_FHSIZE;
fhp->fh_handle.ofh_dcookie = 0xfeebbaca;
fhp->fh_handle.ofh_dev = old_encode_dev(ex_dev);
fhp->fh_handle.ofh_xdev = fhp->fh_handle.ofh_dev;
fhp->fh_handle.ofh_xino =
ino_t_to_u32(d_inode(exp->ex_path.dentry)->i_ino);
fhp->fh_handle.ofh_dirino = ino_t_to_u32(parent_ino(dentry));
if (inode)
_fh_update_old(dentry, exp, &fhp->fh_handle);
} else {
fhp->fh_handle.fh_size =
key_len(fhp->fh_handle.fh_fsid_type) + 4;
fhp->fh_handle.fh_auth_type = 0;
mk_fsid(fhp->fh_handle.fh_fsid_type,
fhp->fh_handle.fh_fsid,
ex_dev,
d_inode(exp->ex_path.dentry)->i_ino,
exp->ex_fsid, exp->ex_uuid);
if (inode)
_fh_update(fhp, exp, dentry);
if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID) {
fh_put(fhp);
return nfserr_opnotsupp;
}
}
return 0;
}
/*
* Update file handle information after changing a dentry.
* This is only called by nfsd_create, nfsd_create_v3 and nfsd_proc_create
*/
__be32
fh_update(struct svc_fh *fhp)
{
struct dentry *dentry;
if (!fhp->fh_dentry)
goto out_bad;
dentry = fhp->fh_dentry;
if (d_really_is_negative(dentry))
goto out_negative;
if (fhp->fh_handle.fh_version != 1) {
_fh_update_old(dentry, fhp->fh_export, &fhp->fh_handle);
} else {
if (fhp->fh_handle.fh_fileid_type != FILEID_ROOT)
return 0;
_fh_update(fhp, fhp->fh_export, dentry);
if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID)
return nfserr_opnotsupp;
}
return 0;
out_bad:
printk(KERN_ERR "fh_update: fh not verified!\n");
return nfserr_serverfault;
out_negative:
printk(KERN_ERR "fh_update: %pd2 still negative!\n",
dentry);
return nfserr_serverfault;
}
/*
* Release a file handle.
*/
void
fh_put(struct svc_fh *fhp)
{
struct dentry * dentry = fhp->fh_dentry;
struct svc_export * exp = fhp->fh_export;
if (dentry) {
fh_unlock(fhp);
fhp->fh_dentry = NULL;
dput(dentry);
fh_clear_wcc(fhp);
}
fh_drop_write(fhp);
if (exp) {
exp_put(exp);
fhp->fh_export = NULL;
}
return;
}
/*
* Shorthand for dprintk()'s
*/
char * SVCFH_fmt(struct svc_fh *fhp)
{
struct knfsd_fh *fh = &fhp->fh_handle;
static char buf[80];
sprintf(buf, "%d: %08x %08x %08x %08x %08x %08x",
fh->fh_size,
fh->fh_base.fh_pad[0],
fh->fh_base.fh_pad[1],
fh->fh_base.fh_pad[2],
fh->fh_base.fh_pad[3],
fh->fh_base.fh_pad[4],
fh->fh_base.fh_pad[5]);
return buf;
}
enum fsid_source fsid_source(struct svc_fh *fhp)
{
if (fhp->fh_handle.fh_version != 1)
return FSIDSOURCE_DEV;
switch(fhp->fh_handle.fh_fsid_type) {
case FSID_DEV:
case FSID_ENCODE_DEV:
case FSID_MAJOR_MINOR:
if (exp_sb(fhp->fh_export)->s_type->fs_flags & FS_REQUIRES_DEV)
return FSIDSOURCE_DEV;
break;
case FSID_NUM:
if (fhp->fh_export->ex_flags & NFSEXP_FSID)
return FSIDSOURCE_FSID;
break;
default:
break;
}
/* either a UUID type filehandle, or the filehandle doesn't
* match the export.
*/
if (fhp->fh_export->ex_flags & NFSEXP_FSID)
return FSIDSOURCE_FSID;
if (fhp->fh_export->ex_uuid)
return FSIDSOURCE_UUID;
return FSIDSOURCE_DEV;
}