# SPDX-License-Identifier: GPL-2.0-only
config CIFS
tristate "SMB3 and CIFS support (advanced network filesystem)"
depends on INET
select NLS
select CRYPTO
select CRYPTO_MD4
select CRYPTO_MD5
select CRYPTO_SHA256
select CRYPTO_SHA512
select CRYPTO_CMAC
select CRYPTO_HMAC
select CRYPTO_ARC4
select CRYPTO_AEAD2
select CRYPTO_CCM
select CRYPTO_ECB
select CRYPTO_AES
select CRYPTO_DES
help
This is the client VFS module for the SMB3 family of NAS protocols,
(including support for the most recent, most secure dialect SMB3.1.1)
as well as for earlier dialects such as SMB2.1, SMB2 and the older
Common Internet File System (CIFS) protocol. CIFS was the successor
to the original dialect, the Server Message Block (SMB) protocol, the
native file sharing mechanism for most early PC operating systems.
The SMB3 protocol is supported by most modern operating systems
and NAS appliances (e.g. Samba, Windows 10, Windows Server 2016,
MacOS) and even in the cloud (e.g. Microsoft Azure).
The older CIFS protocol was included in Windows NT4, 2000 and XP (and
later) as well by Samba (which provides excellent CIFS and SMB3
server support for Linux and many other operating systems). Use of
dialects older than SMB2.1 is often discouraged on public networks.
This module also provides limited support for OS/2 and Windows ME
and similar very old servers.
This module provides an advanced network file system client
for mounting to SMB3 (and CIFS) compliant servers. It includes
support for DFS (hierarchical name space), secure per-user
session establishment via Kerberos or NTLM or NTLMv2, RDMA
(smbdirect), advanced security features, per-share encryption,
directory leases, safe distributed caching (oplock), optional packet
signing, Unicode and other internationalization improvements.
In general, the default dialects, SMB3 and later, enable better
performance, security and features, than would be possible with CIFS.
Note that when mounting to Samba, due to the CIFS POSIX extensions,
CIFS mounts can provide slightly better POSIX compatibility
than SMB3 mounts. SMB2/SMB3 mount options are also
slightly simpler (compared to CIFS) due to protocol improvements.
If you need to mount to Samba, Azure, Macs or Windows from this machine, say Y.
config CIFS_STATS2
bool "Extended statistics"
depends on CIFS
help
Enabling this option will allow more detailed statistics on SMB
request timing to be displayed in /proc/fs/cifs/DebugData and also
allow optional logging of slow responses to dmesg (depending on the
value of /proc/fs/cifs/cifsFYI, see fs/cifs/README for more details).
These additional statistics may have a minor effect on performance
and memory utilization.
Unless you are a developer or are doing network performance analysis
or tuning, say N.
config CIFS_ALLOW_INSECURE_LEGACY
bool "Support legacy servers which use less secure dialects"
depends on CIFS
default y
help
Modern dialects, SMB2.1 and later (including SMB3 and 3.1.1), have
additional security features, including protection against
man-in-the-middle attacks and stronger crypto hashes, so the use
of legacy dialects (SMB1/CIFS and SMB2.0) is discouraged.
Disabling this option prevents users from using vers=1.0 or vers=2.0
on mounts with cifs.ko
If unsure, say Y.
config CIFS_WEAK_PW_HASH
bool "Support legacy servers which use weaker LANMAN security"
depends on CIFS && CIFS_ALLOW_INSECURE_LEGACY
help
Modern CIFS servers including Samba and most Windows versions
(since 1997) support stronger NTLM (and even NTLMv2 and Kerberos)
security mechanisms. These hash the password more securely
than the mechanisms used in the older LANMAN version of the
SMB protocol but LANMAN based authentication is needed to
establish sessions with some old SMB servers.
Enabling this option allows the cifs module to mount to older
LANMAN based servers such as OS/2 and Windows 95, but such
mounts may be less secure than mounts using NTLM or more recent
security mechanisms if you are on a public network. Unless you
have a need to access old SMB servers (and are on a private
network) you probably want to say N. Even if this support
is enabled in the kernel build, LANMAN authentication will not be
used automatically. At runtime LANMAN mounts are disabled but
can be set to required (or optional) either in
/proc/fs/cifs (see fs/cifs/README for more detail) or via an
option on the mount command. This support is disabled by
default in order to reduce the possibility of a downgrade
attack.
If unsure, say N.
config CIFS_UPCALL
bool "Kerberos/SPNEGO advanced session setup"
depends on CIFS && KEYS
select DNS_RESOLVER
help
Enables an upcall mechanism for CIFS which accesses userspace helper
utilities to provide SPNEGO packaged (RFC 4178) Kerberos tickets
which are needed to mount to certain secure servers (for which more
secure Kerberos authentication is required). If unsure, say Y.
config CIFS_XATTR
bool "CIFS extended attributes"
depends on CIFS
help
Extended attributes are name:value pairs associated with inodes by
the kernel or by users (see the attr(5) manual page for details).
CIFS maps the name of extended attributes beginning with the user
namespace prefix to SMB/CIFS EAs. EAs are stored on Windows
servers without the user namespace prefix, but their names are
seen by Linux cifs clients prefaced by the user namespace prefix.
The system namespace (used by some filesystems to store ACLs) is
not supported at this time.
If unsure, say Y.
config CIFS_POSIX
bool "CIFS POSIX Extensions"
depends on CIFS && CIFS_ALLOW_INSECURE_LEGACY && CIFS_XATTR
help
Enabling this option will cause the cifs client to attempt to
negotiate a newer dialect with servers, such as Samba 3.0.5
or later, that optionally can handle more POSIX like (rather
than Windows like) file behavior. It also enables
support for POSIX ACLs (getfacl and setfacl) to servers
(such as Samba 3.10 and later) which can negotiate
CIFS POSIX ACL support. If unsure, say N.
config CIFS_ACL
bool "Provide CIFS ACL support"
depends on CIFS_XATTR && KEYS
help
Allows fetching CIFS/NTFS ACL from the server. The DACL blob
is handed over to the application/caller. See the man
page for getcifsacl for more information. If unsure, say Y.
config CIFS_DEBUG
bool "Enable CIFS debugging routines"
default y
depends on CIFS
help
Enabling this option adds helpful debugging messages to
the cifs code which increases the size of the cifs module.
If unsure, say Y.
config CIFS_DEBUG2
bool "Enable additional CIFS debugging routines"
depends on CIFS_DEBUG
help
Enabling this option adds a few more debugging routines
to the cifs code which slightly increases the size of
the cifs module and can cause additional logging of debug
messages in some error paths, slowing performance. This
option can be turned off unless you are debugging
cifs problems. If unsure, say N.
config CIFS_DEBUG_DUMP_KEYS
bool "Dump encryption keys for offline decryption (Unsafe)"
depends on CIFS_DEBUG
help
Enabling this will dump the encryption and decryption keys
used to communicate on an encrypted share connection on the
console. This allows Wireshark to decrypt and dissect
encrypted network captures. Enable this carefully.
If unsure, say N.
config CIFS_DFS_UPCALL
bool "DFS feature support"
depends on CIFS && KEYS
select DNS_RESOLVER
help
Distributed File System (DFS) support is used to access shares
transparently in an enterprise name space, even if the share
moves to a different server. This feature also enables
an upcall mechanism for CIFS which contacts userspace helper
utilities to provide server name resolution (host names to
IP addresses) which is needed in order to reconnect to
servers if their addresses change or for implicit mounts of
DFS junction points. If unsure, say Y.
config CIFS_NFSD_EXPORT
bool "Allow nfsd to export CIFS file system"
depends on CIFS && BROKEN
help
Allows NFS server to export a CIFS mounted share (nfsd over cifs)
config CIFS_SMB_DIRECT
bool "SMB Direct support (Experimental)"
depends on CIFS=m && INFINIBAND && INFINIBAND_ADDR_TRANS || CIFS=y && INFINIBAND=y && INFINIBAND_ADDR_TRANS=y
help
Enables SMB Direct experimental support for SMB 3.0, 3.02 and 3.1.1.
SMB Direct allows transferring SMB packets over RDMA. If unsure,
say N.
config CIFS_FSCACHE
bool "Provide CIFS client caching support"
depends on CIFS=m && FSCACHE || CIFS=y && FSCACHE=y
help
Makes CIFS FS-Cache capable. Say Y here if you want your CIFS data
to be cached locally on disk through the general filesystem cache
manager. If unsure, say N.
