@@ -20,3 +20,5 @@ rpc-cache.txt
- introduction to the caching mechanisms in the sunrpc layer.
idmapper.txt
- information for configuring request-keys to be used by idmapper
+knfsd-rpcgss.txt
+ - Information on GSS authentication support in the NFS Server
new file mode 100644
@@ -0,0 +1,91 @@
+
+rpcsec_gss support for kernel RPC servers
+=========================================
+
+This document gives references to the standards and protocols used to
+implement RPCGSS authentication in kernel RPC servers such as the NFS
+server and the NFS client's NFSv4.0 callback server. (But note that
+NFSv4.1 and higher don't require the client to act as a server for the
+purposes of authentication.)
+
+RPCGSS is specified in a few IETF documents:
+ - RFC2203 v1: http://tools.ietf.org/rfc/rfc2203.txt
+ - RFC5403 v2: http://tools.ietf.org/rfc/rfc5403.txt
+and there is a 3rd version being proposed:
+ - http://tools.ietf.org/id/draft-williams-rpcsecgssv3.txt
+ (At draft n. 02 at the time of writing)
+
+Background
+----------
+
+The RPCGSS Authentication method describes a way to perform GSSAPI
+Authentication for NFS. Although GSSAPI is itself completely mechanism
+agnostic, in many cases only the KRB5 mechanism is supported by NFS
+implementations.
+
+The Linux kernel, at the moment, supports only the KRB5 mechanism, and
+depends on GSSAPI extensions that are KRB5 specific.
+
+GSSAPI is a complex library, and implementing it completely in kernel is
+unwarranted. However GSSAPI operations are fundementally separable in 2
+parts:
+- initial context establishment
+- integrity/privacy protection (signing and encrypting of individual
+ packets)
+
+The former is more complex and policy-independent, but less
+performance-sensitive. The latter is simpler and needs to be very fast.
+
+Therefore, we perform per-packet integrity and privacy protection in the
+kernel, but leave the initial context establishment to userspace. We
+need upcalls to request userspace to perform context establishment.
+
+NFS Server Legacy Upcall Mechanism
+----------------------------------
+
+The classic upcall mechanism uses a custom text based upcall mechanism
+to talk to a custom daemon called rpc.svcgssd that is provide by the
+nfs-utils package.
+
+This upcall mechanism has 2 limitations:
+
+A) It can handle tokens that are no bigger than 2KiB
+
+In some Kerberos deployment GSSAPI tokens can be quite big, up and
+beyond 64KiB in size due to various authorization extensions attacked to
+the Kerberos tickets, that needs to be sent through the GSS layer in
+order to perform context establishment.
+
+B) It does not properly handle creds where the user is member of more
+than a few housand groups (the current hard limit in the kernel is 65K
+groups) due to limitation on the size of the buffer that can be send
+back to the kernel (4KiB).
+
+NFS Server New RPC Upcall Mechanism
+-----------------------------------
+
+The newer upcall mechanism uses RPC over a unix socket to a daemon
+called gss-proxy, implemented by a userspace program called Gssproxy.
+
+The gss_proxy RPC protocol is currently documented here:
+
+ https://fedorahosted.org/gss-proxy/wiki/ProtocolDocumentation
+
+This upcall mechanism uses the kernel rpc client and connects to the gssproxy
+userspace program over a regular unix socket. The gssproxy protocol does not
+suffer from the size limitations of the legacy protocol.
+
+Negotiating Upcall Mechanisms
+-----------------------------
+
+To provide backward compatibility, the kernel defaults to using the
+legacy mechanism. To switch to the new mechanism, gss-proxy must bind
+to /var/run/gssproxy.sock and then write "1" to
+/proc/net/rpc/use-gss-proxy. If gss-proxy dies, it must repeat both
+steps.
+
+Once the upcall mechanism is chosen, it cannot be changed. To prevent
+locking into the legacy mechanisms, the above steps must be performed
+before starting nfsd. Whoever starts nfsd can guarantee this by reading
+from /proc/net/rpc/use-gss-proxy and checking that it contains a
+"1"--the read will block until gss-proxy has done its write to the file.
@@ -29,9 +29,6 @@
#define GSSPROXY_PROGRAM (400112u)
#define GSSPROXY_VERS_1 (1u)
-DEFINE_MUTEX(gssp_clnt_mutex);
-struct rpc_clnt *gssp_clnt;
-
/*
* Encoding/Decoding functions
*/
@@ -129,49 +126,62 @@ out:
return result;
}
-static struct rpc_clnt *get_clnt(struct net *net, bool global_clnt)
+void init_gssp_clnt(struct sunrpc_net *sn)
{
- struct rpc_clnt *clnt;
- int err;
-
- mutex_lock(&gssp_clnt_mutex);
+ mutex_init(&sn->gssp_lock);
+ sn->gssp_clnt = NULL;
+ init_waitqueue_head(&sn->gssp_wq);
+}
- if (global_clnt && gssp_clnt)
- return gssp_clnt;
+int set_gssp_clnt(struct net *net)
+{
+ struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+ struct rpc_clnt *clnt;
+ int ret;
- err = gssp_rpc_create(net, &clnt);
- if (err) {
- mutex_unlock(&gssp_clnt_mutex);
- return NULL;
+ mutex_lock(&sn->gssp_lock);
+ ret = gssp_rpc_create(net, &clnt);
+ if (!ret) {
+ if (sn->gssp_clnt)
+ rpc_shutdown_client(sn->gssp_clnt);
+ sn->gssp_clnt = clnt;
}
- if (global_clnt)
- gssp_clnt = clnt;
-
- mutex_unlock(&gssp_clnt_mutex);
- return clnt;
+ mutex_unlock(&sn->gssp_lock);
+ wake_up(&sn->gssp_wq);
+ return ret;
}
-static void kill_clnt(struct rpc_clnt *clnt)
+void clear_gssp_clnt(struct sunrpc_net *sn)
{
- BUG_ON(clnt == NULL);
-
- mutex_lock(&gssp_clnt_mutex);
+ mutex_lock(&sn->gssp_lock);
+ if (sn->gssp_clnt) {
+ rpc_shutdown_client(sn->gssp_clnt);
+ sn->gssp_clnt = NULL;
+ }
+ mutex_unlock(&sn->gssp_lock);
+}
- rpc_shutdown_client(clnt);
- if (clnt == gssp_clnt)
- gssp_clnt = NULL;
+static struct rpc_clnt *get_gssp_clnt(struct sunrpc_net *sn)
+{
+ struct rpc_clnt *clnt;
- mutex_unlock(&gssp_clnt_mutex);
+ mutex_lock(&sn->gssp_lock);
+ clnt = sn->gssp_clnt;
+ if (clnt)
+ atomic_inc(&clnt->cl_count);
+ mutex_unlock(&sn->gssp_lock);
+ return clnt;
}
static int gssp_call(struct net *net, struct rpc_message *msg)
{
+ struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
struct rpc_clnt *clnt;
int status;
- /* for now always create new one */
- clnt = get_clnt(net, false);
-
+ clnt = get_gssp_clnt(sn);
+ if (!clnt)
+ return -EIO;
status = rpc_call_sync(clnt, msg, 0);
if (status < 0) {
dprintk("gssp: rpc_call returned error %d\n", -status);
@@ -192,10 +202,7 @@ static int gssp_call(struct net *net, struct rpc_message *msg)
break;
}
}
-
- /* always kill connection for now */
- kill_clnt(clnt);
-
+ rpc_release_client(clnt);
return status;
}
@@ -23,6 +23,7 @@
#include <linux/sunrpc/auth_gss.h>
#include "gss_rpc_xdr.h"
+#include "../netns.h"
struct gssp_upcall_data {
struct xdr_netobj in_handle;
@@ -40,4 +41,7 @@ int gssp_accept_sec_context_upcall(struct net *net,
struct gssp_upcall_data *data);
void gssp_free_upcall_data(struct gssp_upcall_data *data);
+void init_gssp_clnt(struct sunrpc_net *);
+int set_gssp_clnt(struct net *);
+void clear_gssp_clnt(struct sunrpc_net *);
#endif /* _GSS_RPC_UPCALL_H */
@@ -48,8 +48,8 @@
#include <linux/sunrpc/svcauth.h>
#include <linux/sunrpc/svcauth_gss.h>
#include <linux/sunrpc/cache.h>
+#include "gss_rpc_upcall.h"
-#include "../netns.h"
#ifdef RPC_DEBUG
# define RPCDBG_FACILITY RPCDBG_AUTH
@@ -976,13 +976,10 @@ gss_write_init_verf(struct cache_detail *cd, struct svc_rqst *rqstp,
}
static inline int
-gss_read_verf(struct rpc_gss_wire_cred *gc,
- struct kvec *argv, __be32 *authp,
- struct xdr_netobj *in_handle,
- struct xdr_netobj *in_token)
+gss_read_common_verf(struct rpc_gss_wire_cred *gc,
+ struct kvec *argv, __be32 *authp,
+ struct xdr_netobj *in_handle)
{
- struct xdr_netobj tmpobj;
-
/* Read the verifier; should be NULL: */
*authp = rpc_autherr_badverf;
if (argv->iov_len < 2 * 4)
@@ -998,6 +995,23 @@ gss_read_verf(struct rpc_gss_wire_cred *gc,
if (dup_netobj(in_handle, &gc->gc_ctx))
return SVC_CLOSE;
*authp = rpc_autherr_badverf;
+
+ return 0;
+}
+
+static inline int
+gss_read_verf(struct rpc_gss_wire_cred *gc,
+ struct kvec *argv, __be32 *authp,
+ struct xdr_netobj *in_handle,
+ struct xdr_netobj *in_token)
+{
+ struct xdr_netobj tmpobj;
+ int res;
+
+ res = gss_read_common_verf(gc, argv, authp, in_handle);
+ if (res)
+ return res;
+
if (svc_safe_getnetobj(argv, &tmpobj)) {
kfree(in_handle->data);
return SVC_DENIED;
@@ -1010,6 +1024,40 @@ gss_read_verf(struct rpc_gss_wire_cred *gc,
return 0;
}
+/* Ok this is really heavily depending on a set of semantics in
+ * how rqstp is set up by svc_recv and pages laid down by the
+ * server when reading a request. We are basically guaranteed that
+ * the token lays all down linearly across a set of pages, starting
+ * at iov_base in rq_arg.head[0] which happens to be the first of a
+ * set of pages stored in rq_pages[].
+ * rq_arg.head[0].iov_base will provide us the page_base to pass
+ * to the upcall.
+ */
+static inline int
+gss_read_proxy_verf(struct svc_rqst *rqstp,
+ struct rpc_gss_wire_cred *gc, __be32 *authp,
+ struct xdr_netobj *in_handle,
+ struct gssp_in_token *in_token)
+{
+ struct kvec *argv = &rqstp->rq_arg.head[0];
+ u32 inlen;
+ int res;
+
+ res = gss_read_common_verf(gc, argv, authp, in_handle);
+ if (res)
+ return res;
+
+ inlen = svc_getnl(argv);
+ if (inlen > (argv->iov_len + rqstp->rq_arg.page_len))
+ return SVC_DENIED;
+
+ in_token->pages = rqstp->rq_pages;
+ in_token->page_base = (ulong)argv->iov_base & ~PAGE_MASK;
+ in_token->page_len = inlen;
+
+ return 0;
+}
+
static inline int
gss_write_resv(struct kvec *resv, size_t size_limit,
struct xdr_netobj *out_handle, struct xdr_netobj *out_token,
@@ -1037,7 +1085,7 @@ gss_write_resv(struct kvec *resv, size_t size_limit,
* the upcall results are available, write the verifier and result.
* Otherwise, drop the request pending an answer to the upcall.
*/
-static int svcauth_gss_handle_init(struct svc_rqst *rqstp,
+static int svcauth_gss_legacy_init(struct svc_rqst *rqstp,
struct rpc_gss_wire_cred *gc, __be32 *authp)
{
struct kvec *argv = &rqstp->rq_arg.head[0];
@@ -1077,6 +1125,278 @@ out:
return ret;
}
+static int gss_proxy_save_rsc(struct cache_detail *cd,
+ struct gssp_upcall_data *ud,
+ uint64_t *handle)
+{
+ struct rsc rsci, *rscp = NULL;
+ static atomic64_t ctxhctr;
+ long long ctxh;
+ struct gss_api_mech *gm = NULL;
+ time_t expiry;
+ int status = -EINVAL;
+
+ memset(&rsci, 0, sizeof(rsci));
+ /* context handle */
+ status = -ENOMEM;
+ /* the handle needs to be just a unique id,
+ * use a static counter */
+ ctxh = atomic64_inc_return(&ctxhctr);
+
+ /* make a copy for the caller */
+ *handle = ctxh;
+
+ /* make a copy for the rsc cache */
+ if (dup_to_netobj(&rsci.handle, (char *)handle, sizeof(uint64_t)))
+ goto out;
+ rscp = rsc_lookup(cd, &rsci);
+ if (!rscp)
+ goto out;
+
+ /* creds */
+ if (!ud->found_creds) {
+ /* userspace seem buggy, we should always get at least a
+ * mapping to nobody */
+ dprintk("RPC: No creds found, marking Negative!\n");
+ set_bit(CACHE_NEGATIVE, &rsci.h.flags);
+ } else {
+
+ /* steal creds */
+ rsci.cred = ud->creds;
+ memset(&ud->creds, 0, sizeof(struct svc_cred));
+
+ status = -EOPNOTSUPP;
+ /* get mech handle from OID */
+ gm = gss_mech_get_by_OID(&ud->mech_oid);
+ if (!gm)
+ goto out;
+
+ status = -EINVAL;
+ /* mech-specific data: */
+ status = gss_import_sec_context(ud->out_handle.data,
+ ud->out_handle.len,
+ gm, &rsci.mechctx,
+ &expiry, GFP_KERNEL);
+ if (status)
+ goto out;
+ }
+
+ rsci.h.expiry_time = expiry;
+ rscp = rsc_update(cd, &rsci, rscp);
+ status = 0;
+out:
+ gss_mech_put(gm);
+ rsc_free(&rsci);
+ if (rscp)
+ cache_put(&rscp->h, cd);
+ else
+ status = -ENOMEM;
+ return status;
+}
+
+static int svcauth_gss_proxy_init(struct svc_rqst *rqstp,
+ struct rpc_gss_wire_cred *gc, __be32 *authp)
+{
+ struct kvec *resv = &rqstp->rq_res.head[0];
+ struct xdr_netobj cli_handle;
+ struct gssp_upcall_data ud;
+ uint64_t handle;
+ int status;
+ int ret;
+ struct net *net = rqstp->rq_xprt->xpt_net;
+ struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+
+ memset(&ud, 0, sizeof(ud));
+ ret = gss_read_proxy_verf(rqstp, gc, authp,
+ &ud.in_handle, &ud.in_token);
+ if (ret)
+ return ret;
+
+ ret = SVC_CLOSE;
+
+ /* Perform synchronous upcall to gss-proxy */
+ status = gssp_accept_sec_context_upcall(net, &ud);
+ if (status)
+ goto out;
+
+ dprintk("RPC: svcauth_gss: gss major status = %d\n",
+ ud.major_status);
+
+ switch (ud.major_status) {
+ case GSS_S_CONTINUE_NEEDED:
+ cli_handle = ud.out_handle;
+ break;
+ case GSS_S_COMPLETE:
+ status = gss_proxy_save_rsc(sn->rsc_cache, &ud, &handle);
+ if (status)
+ goto out;
+ cli_handle.data = (u8 *)&handle;
+ cli_handle.len = sizeof(handle);
+ break;
+ default:
+ ret = SVC_CLOSE;
+ goto out;
+ }
+
+ /* Got an answer to the upcall; use it: */
+ if (gss_write_init_verf(sn->rsc_cache, rqstp,
+ &cli_handle, &ud.major_status))
+ goto out;
+ if (gss_write_resv(resv, PAGE_SIZE,
+ &cli_handle, &ud.out_token,
+ ud.major_status, ud.minor_status))
+ goto out;
+
+ ret = SVC_COMPLETE;
+out:
+ gssp_free_upcall_data(&ud);
+ return ret;
+}
+
+DEFINE_SPINLOCK(use_gssp_lock);
+
+static bool use_gss_proxy(struct net *net)
+{
+ struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+
+ if (sn->use_gss_proxy != -1)
+ return sn->use_gss_proxy;
+ spin_lock(&use_gssp_lock);
+ /*
+ * If you wanted gss-proxy, you should have said so before
+ * starting to accept requests:
+ */
+ sn->use_gss_proxy = 0;
+ spin_unlock(&use_gssp_lock);
+ return 0;
+}
+
+static bool set_gss_proxy(struct net *net, int type)
+{
+ struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+ int ret = 0;
+
+ WARN_ON_ONCE(type != 0 && type != 1);
+ spin_lock(&use_gssp_lock);
+ if (sn->use_gss_proxy == -1 || sn->use_gss_proxy == type)
+ sn->use_gss_proxy = type;
+ else
+ ret = -EBUSY;
+ spin_unlock(&use_gssp_lock);
+ wake_up(&sn->gssp_wq);
+ return ret;
+}
+
+static inline bool gssp_ready(struct sunrpc_net *sn)
+{
+ switch (sn->use_gss_proxy) {
+ case -1:
+ return false;
+ case 0:
+ return true;
+ case 1:
+ return sn->gssp_clnt;
+ }
+ WARN_ON_ONCE(1);
+ return false;
+}
+
+static int wait_for_gss_proxy(struct net *net)
+{
+ struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+
+ return wait_event_interruptible(sn->gssp_wq, gssp_ready(sn));
+}
+
+#ifdef CONFIG_PROC_FS
+
+static ssize_t write_gssp(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct net *net = PDE(file->f_path.dentry->d_inode)->data;
+ char tbuf[20];
+ unsigned long i;
+ int res;
+
+ if (*ppos || count > sizeof(tbuf)-1)
+ return -EINVAL;
+ if (copy_from_user(tbuf, buf, count))
+ return -EFAULT;
+
+ tbuf[count] = 0;
+ res = kstrtoul(tbuf, 0, &i);
+ if (res)
+ return res;
+ if (i != 1)
+ return -EINVAL;
+ res = set_gss_proxy(net, 1);
+ if (res)
+ return res;
+ res = set_gssp_clnt(net);
+ if (res)
+ return res;
+ return count;
+}
+
+static ssize_t read_gssp(struct file *file, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct net *net = PDE(file->f_path.dentry->d_inode)->data;
+ unsigned long p = *ppos;
+ char tbuf[10];
+ size_t len;
+ int ret;
+
+ ret = wait_for_gss_proxy(net);
+ if (ret)
+ return ret;
+
+ snprintf(tbuf, sizeof(tbuf), "%d\n", use_gss_proxy(net));
+ len = strlen(tbuf);
+ if (p >= len)
+ return 0;
+ len -= p;
+ if (len > count)
+ len = count;
+ if (copy_to_user(buf, (void *)(tbuf+p), len))
+ return -EFAULT;
+ *ppos += len;
+ return len;
+}
+
+static const struct file_operations use_gss_proxy_ops = {
+ .open = nonseekable_open,
+ .write = write_gssp,
+ .read = read_gssp,
+};
+
+static int create_use_gss_proxy_proc_entry(struct net *net)
+{
+ struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+ struct proc_dir_entry **p = &sn->use_gssp_proc;
+
+ sn->use_gss_proxy = -1;
+ *p = proc_create_data("use-gss-proxy", S_IFREG|S_IRUSR|S_IWUSR,
+ sn->proc_net_rpc,
+ &use_gss_proxy_ops, net);
+ if (!*p)
+ return -ENOMEM;
+ init_gssp_clnt(sn);
+ return 0;
+}
+
+static void destroy_use_gss_proxy_proc_entry(struct net *net)
+{
+ struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+
+ if (sn->use_gssp_proc) {
+ remove_proc_entry("use-gss-proxy", sn->proc_net_rpc);
+ clear_gssp_clnt(sn);
+ }
+}
+
+#endif /* CONFIG_PROC_FS */
+
/*
* Accept an rpcsec packet.
* If context establishment, punt to user space
@@ -1143,7 +1463,10 @@ svcauth_gss_accept(struct svc_rqst *rqstp, __be32 *authp)
switch (gc->gc_proc) {
case RPC_GSS_PROC_INIT:
case RPC_GSS_PROC_CONTINUE_INIT:
- return svcauth_gss_handle_init(rqstp, gc, authp);
+ if (use_gss_proxy(SVC_NET(rqstp)))
+ return svcauth_gss_proxy_init(rqstp, gc, authp);
+ else
+ return svcauth_gss_legacy_init(rqstp, gc, authp);
case RPC_GSS_PROC_DATA:
case RPC_GSS_PROC_DESTROY:
/* Look up the context, and check the verifier: */
@@ -1518,7 +1841,12 @@ gss_svc_init_net(struct net *net)
rv = rsi_cache_create_net(net);
if (rv)
goto out1;
+ rv = create_use_gss_proxy_proc_entry(net);
+ if (rv)
+ goto out2;
return 0;
+out2:
+ destroy_use_gss_proxy_proc_entry(net);
out1:
rsc_cache_destroy_net(net);
return rv;
@@ -1527,6 +1855,7 @@ out1:
void
gss_svc_shutdown_net(struct net *net)
{
+ destroy_use_gss_proxy_proc_entry(net);
rsi_cache_destroy_net(net);
rsc_cache_destroy_net(net);
}
@@ -689,6 +689,7 @@ rpc_release_client(struct rpc_clnt *clnt)
if (atomic_dec_and_test(&clnt->cl_count))
rpc_free_auth(clnt);
}
+EXPORT_SYMBOL_GPL(rpc_release_client);
/**
* rpc_bind_new_program - bind a new RPC program to an existing client
@@ -23,6 +23,12 @@ struct sunrpc_net {
struct rpc_clnt *rpcb_local_clnt4;
spinlock_t rpcb_clnt_lock;
unsigned int rpcb_users;
+
+ struct mutex gssp_lock;
+ wait_queue_head_t gssp_wq;
+ struct rpc_clnt *gssp_clnt;
+ int use_gss_proxy;
+ struct proc_dir_entry *use_gssp_proc;
};
extern int sunrpc_net_id;