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cifs: allow disabling insecure dialects in the config 

allow disabling cifs (SMB1 ie vers=1.0) and vers=2.0 in the
config for the build of cifs.ko if want to always prevent mounting
with these less secure dialects.

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Jeremy Allison <jra@samba.org>
This commit is contained in:
Steve French 2018-06-19 14:34:08 -05:00
parent 8505c8bfd8
commit 7420451f6a
2 changed files with 25 additions and 1 deletions
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17
fs/cifs/Kconfig
View File

@ -66,9 +66,24 @@ config CIFS_STATS2
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
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)

9
fs/cifs/connect.c
View File

@ -1174,6 +1174,7 @@ cifs_parse_smb_version(char *value, struct smb_vol *vol, bool is_smb3)
substring_t args[MAX_OPT_ARGS];
switch (match_token(value, cifs_smb_version_tokens, args)) {
#ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
case Smb_1:
if (disable_legacy_dialects) {
cifs_dbg(VFS, "mount with legacy dialect disabled\n");
@ -1198,6 +1199,14 @@ cifs_parse_smb_version(char *value, struct smb_vol *vol, bool is_smb3)
vol->ops = &smb20_operations;
vol->vals = &smb20_values;
break;
#else
case Smb_1:
cifs_dbg(VFS, "vers=1.0 (cifs) mount not permitted when legacy dialects disabled\n");
return 1;
case Smb_20:
cifs_dbg(VFS, "vers=2.0 mount not permitted when legacy dialects disabled\n");
return 1;
#endif /* CIFS_ALLOW_INSECURE_LEGACY */
case Smb_21:
vol->ops = &smb21_operations;
vol->vals = &smb21_values;