diff options
| -rw-r--r-- | Documentation/filesystems/nfs/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/nfs/rpc-server-gss.txt | 91 | ||||
| -rw-r--r-- | net/sunrpc/auth_gss/gss_rpc_upcall.c | 2 | ||||
| -rw-r--r-- | net/sunrpc/auth_gss/svcauth_gss.c | 347 | ||||
| -rw-r--r-- | net/sunrpc/netns.h | 3 |
5 files changed, 436 insertions, 9 deletions
diff --git a/Documentation/filesystems/nfs/00-INDEX b/Documentation/filesystems/nfs/00-INDEX index 1716874a..66eb6c8 100644 --- a/Documentation/filesystems/nfs/00-INDEX +++ b/Documentation/filesystems/nfs/00-INDEX @@ -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 diff --git a/Documentation/filesystems/nfs/rpc-server-gss.txt b/Documentation/filesystems/nfs/rpc-server-gss.txt new file mode 100644 index 0000000..716f4be --- /dev/null +++ b/Documentation/filesystems/nfs/rpc-server-gss.txt @@ -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. diff --git a/net/sunrpc/auth_gss/gss_rpc_upcall.c b/net/sunrpc/auth_gss/gss_rpc_upcall.c index 2d33ddf..3f874d7 100644 --- a/net/sunrpc/auth_gss/gss_rpc_upcall.c +++ b/net/sunrpc/auth_gss/gss_rpc_upcall.c @@ -137,6 +137,7 @@ void init_gssp_clnt(struct sunrpc_net *sn) { mutex_init(&sn->gssp_lock); sn->gssp_clnt = NULL; + init_waitqueue_head(&sn->gssp_wq); } int set_gssp_clnt(struct net *net) @@ -153,6 +154,7 @@ int set_gssp_clnt(struct net *net) sn->gssp_clnt = clnt; } mutex_unlock(&sn->gssp_lock); + wake_up(&sn->gssp_wq); return ret; } diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c index 20eedec..58f5bc3 100644 --- a/net/sunrpc/auth_gss/svcauth_gss.c +++ b/net/sunrpc/auth_gss/svcauth_gss.c @@ -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 @@ -988,13 +988,10 @@ 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) @@ -1010,6 +1007,23 @@ 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; @@ -1022,6 +1036,40 @@ 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, @@ -1049,7 +1097,7 @@ 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]; @@ -1089,6 +1137,278 @@ 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 @@ -1155,7 +1475,10 @@ 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: */ @@ -1530,7 +1853,12 @@ 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; @@ -1539,6 +1867,7 @@ 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); } diff --git a/net/sunrpc/netns.h b/net/sunrpc/netns.h index e9f8895..7111a4c 100644 --- a/net/sunrpc/netns.h +++ b/net/sunrpc/netns.h @@ -25,7 +25,10 @@ struct sunrpc_net { 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; |