diff options
Diffstat (limited to 'Documentation/filesystems/nfs')
| -rw-r--r-- | Documentation/filesystems/nfs/00-INDEX | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/nfs/Exporting | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/nfs/nfs41-server.txt | 44 | ||||
| -rw-r--r-- | Documentation/filesystems/nfs/pnfs.txt | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/nfs/rpc-server-gss.txt | 91 |
5 files changed, 111 insertions, 32 deletions
diff --git a/Documentation/filesystems/nfs/00-INDEX b/Documentation/filesystems/nfs/00-INDEX index 1716874a651..53f3b596ac0 100644 --- a/Documentation/filesystems/nfs/00-INDEX +++ b/Documentation/filesystems/nfs/00-INDEX @@ -12,6 +12,8 @@ nfs41-server.txt - info on the Linux server implementation of NFSv4 minor version 1. nfs-rdma.txt - how to install and setup the Linux NFS/RDMA client and server software +nfsd-admin-interfaces.txt + - Administrative interfaces for nfsd. nfsroot.txt - short guide on setting up a diskless box with NFS root filesystem. pnfs.txt @@ -20,3 +22,5 @@ rpc-cache.txt - introduction to the caching mechanisms in the sunrpc layer. idmapper.txt - information for configuring request-keys to be used by idmapper +rpc-server-gss.txt + - Information on GSS authentication support in the NFS Server diff --git a/Documentation/filesystems/nfs/Exporting b/Documentation/filesystems/nfs/Exporting index 09994c24728..e543b1a619c 100644 --- a/Documentation/filesystems/nfs/Exporting +++ b/Documentation/filesystems/nfs/Exporting @@ -93,7 +93,7 @@ For a filesystem to be exportable it must: 2/ make sure that d_splice_alias is used rather than d_add when ->lookup finds an inode for a given parent and name. - If inode is NULL, d_splice_alias(inode, dentry) is eqivalent to + If inode is NULL, d_splice_alias(inode, dentry) is equivalent to d_add(dentry, inode), NULL diff --git a/Documentation/filesystems/nfs/nfs41-server.txt b/Documentation/filesystems/nfs/nfs41-server.txt index 01c2db76979..c49cd7e796e 100644 --- a/Documentation/filesystems/nfs/nfs41-server.txt +++ b/Documentation/filesystems/nfs/nfs41-server.txt @@ -5,11 +5,11 @@ Server support for minorversion 1 can be controlled using the by reading this file will contain either "+4.1" or "-4.1" correspondingly. -Currently, server support for minorversion 1 is disabled by default. -It can be enabled at run time by writing the string "+4.1" to +Currently, server support for minorversion 1 is enabled by default. +It can be disabled at run time by writing the string "-4.1" to the /proc/fs/nfsd/versions control file. Note that to write this -control file, the nfsd service must be taken down. Use your user-mode -nfs-utils to set this up; see rpc.nfsd(8) +control file, the nfsd service must be taken down. You can use rpc.nfsd +for this; see rpc.nfsd(8). (Warning: older servers will interpret "+4.1" and "-4.1" as "+4" and "-4", respectively. Therefore, code meant to work on both new and old @@ -29,29 +29,6 @@ are still under development out of tree. See http://wiki.linux-nfs.org/wiki/index.php/PNFS_prototype_design for more information. -The current implementation is intended for developers only: while it -does support ordinary file operations on clients we have tested against -(including the linux client), it is incomplete in ways which may limit -features unexpectedly, cause known bugs in rare cases, or cause -interoperability problems with future clients. Known issues: - - - gss support is questionable: currently mounts with kerberos - from a linux client are possible, but we aren't really - conformant with the spec (for example, we don't use kerberos - on the backchannel correctly). - - We do not support SSV, which provides security for shared - client-server state (thus preventing unauthorized tampering - with locks and opens, for example). It is mandatory for - servers to support this, though no clients use it yet. - -In addition, some limitations are inherited from the current NFSv4 -implementation: - - - Incomplete delegation enforcement: if a file is renamed or - unlinked by a local process, a client holding a delegation may - continue to indefinitely allow opens of the file under the old - name. - The table below, taken from the NFSv4.1 document, lists the operations that are mandatory to implement (REQ), optional (OPT), and NFSv4.0 operations that are required not to implement (MNI) @@ -169,6 +146,16 @@ NS*| CB_WANTS_CANCELLED | OPT | FDELG, | Section 20.10 | Implementation notes: +SSV: +* The spec claims this is mandatory, but we don't actually know of any + implementations, so we're ignoring it for now. The server returns + NFS4ERR_ENCR_ALG_UNSUPP on EXCHANGE_ID, which should be future-proof. + +GSS on the backchannel: +* Again, theoretically required but not widely implemented (in + particular, the current Linux client doesn't request it). We return + NFS4ERR_ENCR_ALG_UNSUPP on CREATE_SESSION. + DELEGPURGE: * mandatory only for servers that support CLAIM_DELEGATE_PREV and/or CLAIM_DELEG_PREV_FH (which allows clients to keep delegations that @@ -176,7 +163,6 @@ DELEGPURGE: now. EXCHANGE_ID: -* only SP4_NONE state protection supported * implementation ids are ignored CREATE_SESSION: @@ -190,7 +176,5 @@ Nonstandard compound limitations: ca_maxrequestsize request and a ca_maxresponsesize reply, so we may fail to live up to the promise we made in CREATE_SESSION fore channel negotiation. -* No more than one read-like operation allowed per compound; encoding - replies that cross page boundaries (except for read data) not handled. See also http://wiki.linux-nfs.org/wiki/index.php/Server_4.0_and_4.1_issues. diff --git a/Documentation/filesystems/nfs/pnfs.txt b/Documentation/filesystems/nfs/pnfs.txt index 52ae07f5f57..adc81a35fe2 100644 --- a/Documentation/filesystems/nfs/pnfs.txt +++ b/Documentation/filesystems/nfs/pnfs.txt @@ -12,7 +12,7 @@ struct pnfs_layout_hdr ---------------------- The on-the-wire command LAYOUTGET corresponds to struct pnfs_layout_segment, usually referred to by the variable name lseg. -Each nfs_inode may hold a pointer to a cache of of these layout +Each nfs_inode may hold a pointer to a cache of these layout segments in nfsi->layout, of type struct pnfs_layout_hdr. We reference the header for the inode pointing to it, across each diff --git a/Documentation/filesystems/nfs/rpc-server-gss.txt b/Documentation/filesystems/nfs/rpc-server-gss.txt new file mode 100644 index 00000000000..716f4be8e8b --- /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. |