linux/net/sunrpc/auth_unix.c
NeilBrown dc6f55e9f8 NFS/sunrpc: don't use a credential with extra groups.
The sunrpc layer keeps a cache of recently used credentials and
'unx_match' is used to find the credential which matches the current
process.

However unx_match allows a match when the cached credential has extra
groups at the end of uc_gids list which are not in the process group list.

So if a process with a list of (say) 4 group accesses a file and gains
access because of the last group in the list, then another process
with the same uid and gid, and a gid list being the first tree of the
gids of the original process tries to access the file, it will be
granted access even though it shouldn't as the wrong rpc credential
will be used.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org
2011-10-25 11:20:58 +02:00

247 lines
5.5 KiB
C

/*
* linux/net/sunrpc/auth_unix.c
*
* UNIX-style authentication; no AUTH_SHORT support
*
* Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
*/
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/auth.h>
#define NFS_NGROUPS 16
struct unx_cred {
struct rpc_cred uc_base;
gid_t uc_gid;
gid_t uc_gids[NFS_NGROUPS];
};
#define uc_uid uc_base.cr_uid
#define UNX_WRITESLACK (21 + (UNX_MAXNODENAME >> 2))
#ifdef RPC_DEBUG
# define RPCDBG_FACILITY RPCDBG_AUTH
#endif
static struct rpc_auth unix_auth;
static const struct rpc_credops unix_credops;
static struct rpc_auth *
unx_create(struct rpc_clnt *clnt, rpc_authflavor_t flavor)
{
dprintk("RPC: creating UNIX authenticator for client %p\n",
clnt);
atomic_inc(&unix_auth.au_count);
return &unix_auth;
}
static void
unx_destroy(struct rpc_auth *auth)
{
dprintk("RPC: destroying UNIX authenticator %p\n", auth);
rpcauth_clear_credcache(auth->au_credcache);
}
/*
* Lookup AUTH_UNIX creds for current process
*/
static struct rpc_cred *
unx_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
return rpcauth_lookup_credcache(auth, acred, flags);
}
static struct rpc_cred *
unx_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
struct unx_cred *cred;
unsigned int groups = 0;
unsigned int i;
dprintk("RPC: allocating UNIX cred for uid %d gid %d\n",
acred->uid, acred->gid);
if (!(cred = kmalloc(sizeof(*cred), GFP_NOFS)))
return ERR_PTR(-ENOMEM);
rpcauth_init_cred(&cred->uc_base, acred, auth, &unix_credops);
cred->uc_base.cr_flags = 1UL << RPCAUTH_CRED_UPTODATE;
if (acred->group_info != NULL)
groups = acred->group_info->ngroups;
if (groups > NFS_NGROUPS)
groups = NFS_NGROUPS;
cred->uc_gid = acred->gid;
for (i = 0; i < groups; i++)
cred->uc_gids[i] = GROUP_AT(acred->group_info, i);
if (i < NFS_NGROUPS)
cred->uc_gids[i] = NOGROUP;
return &cred->uc_base;
}
static void
unx_free_cred(struct unx_cred *unx_cred)
{
dprintk("RPC: unx_free_cred %p\n", unx_cred);
kfree(unx_cred);
}
static void
unx_free_cred_callback(struct rcu_head *head)
{
struct unx_cred *unx_cred = container_of(head, struct unx_cred, uc_base.cr_rcu);
unx_free_cred(unx_cred);
}
static void
unx_destroy_cred(struct rpc_cred *cred)
{
call_rcu(&cred->cr_rcu, unx_free_cred_callback);
}
/*
* Match credentials against current process creds.
* The root_override argument takes care of cases where the caller may
* request root creds (e.g. for NFS swapping).
*/
static int
unx_match(struct auth_cred *acred, struct rpc_cred *rcred, int flags)
{
struct unx_cred *cred = container_of(rcred, struct unx_cred, uc_base);
unsigned int groups = 0;
unsigned int i;
if (cred->uc_uid != acred->uid || cred->uc_gid != acred->gid)
return 0;
if (acred->group_info != NULL)
groups = acred->group_info->ngroups;
if (groups > NFS_NGROUPS)
groups = NFS_NGROUPS;
for (i = 0; i < groups ; i++)
if (cred->uc_gids[i] != GROUP_AT(acred->group_info, i))
return 0;
if (groups < NFS_NGROUPS &&
cred->uc_gids[groups] != NOGROUP)
return 0;
return 1;
}
/*
* Marshal credentials.
* Maybe we should keep a cached credential for performance reasons.
*/
static __be32 *
unx_marshal(struct rpc_task *task, __be32 *p)
{
struct rpc_clnt *clnt = task->tk_client;
struct unx_cred *cred = container_of(task->tk_rqstp->rq_cred, struct unx_cred, uc_base);
__be32 *base, *hold;
int i;
*p++ = htonl(RPC_AUTH_UNIX);
base = p++;
*p++ = htonl(jiffies/HZ);
/*
* Copy the UTS nodename captured when the client was created.
*/
p = xdr_encode_array(p, clnt->cl_nodename, clnt->cl_nodelen);
*p++ = htonl((u32) cred->uc_uid);
*p++ = htonl((u32) cred->uc_gid);
hold = p++;
for (i = 0; i < 16 && cred->uc_gids[i] != (gid_t) NOGROUP; i++)
*p++ = htonl((u32) cred->uc_gids[i]);
*hold = htonl(p - hold - 1); /* gid array length */
*base = htonl((p - base - 1) << 2); /* cred length */
*p++ = htonl(RPC_AUTH_NULL);
*p++ = htonl(0);
return p;
}
/*
* Refresh credentials. This is a no-op for AUTH_UNIX
*/
static int
unx_refresh(struct rpc_task *task)
{
set_bit(RPCAUTH_CRED_UPTODATE, &task->tk_rqstp->rq_cred->cr_flags);
return 0;
}
static __be32 *
unx_validate(struct rpc_task *task, __be32 *p)
{
rpc_authflavor_t flavor;
u32 size;
flavor = ntohl(*p++);
if (flavor != RPC_AUTH_NULL &&
flavor != RPC_AUTH_UNIX &&
flavor != RPC_AUTH_SHORT) {
printk("RPC: bad verf flavor: %u\n", flavor);
return NULL;
}
size = ntohl(*p++);
if (size > RPC_MAX_AUTH_SIZE) {
printk("RPC: giant verf size: %u\n", size);
return NULL;
}
task->tk_rqstp->rq_cred->cr_auth->au_rslack = (size >> 2) + 2;
p += (size >> 2);
return p;
}
int __init rpc_init_authunix(void)
{
return rpcauth_init_credcache(&unix_auth);
}
void rpc_destroy_authunix(void)
{
rpcauth_destroy_credcache(&unix_auth);
}
const struct rpc_authops authunix_ops = {
.owner = THIS_MODULE,
.au_flavor = RPC_AUTH_UNIX,
.au_name = "UNIX",
.create = unx_create,
.destroy = unx_destroy,
.lookup_cred = unx_lookup_cred,
.crcreate = unx_create_cred,
};
static
struct rpc_auth unix_auth = {
.au_cslack = UNX_WRITESLACK,
.au_rslack = 2, /* assume AUTH_NULL verf */
.au_ops = &authunix_ops,
.au_flavor = RPC_AUTH_UNIX,
.au_count = ATOMIC_INIT(0),
};
static
const struct rpc_credops unix_credops = {
.cr_name = "AUTH_UNIX",
.crdestroy = unx_destroy_cred,
.crbind = rpcauth_generic_bind_cred,
.crmatch = unx_match,
.crmarshal = unx_marshal,
.crrefresh = unx_refresh,
.crvalidate = unx_validate,
};