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cifs: allow disabling less secure legacy dialects

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To improve security it may be helpful to have additional ways to restrict the
ability to override the default dialects (SMB2.1, SMB3 and SMB3.02) on mount
with old dialects (CIFS/SMB1 and SMB2) since vers=1.0 (CIFS/SMB1) and vers=2.0
are weaker and less secure.

Add a module parameter "disable_legacy_dialects"
(/sys/module/cifs/parameters/disable_legacy_dialects) which can be set to
1 (or equivalently Y) to forbid use of vers=1.0 or vers=2.0 on mount.

Also cleans up a few build warnings about globals for various module parms.

Signed-off-by: Steve French <smfrench@gmail.com>
This commit is contained in:
Steve French 2018-05-24 04:11:07 -05:00
parent 11911b956f
commit f92a720ee9
3 changed files with 29 additions and 9 deletions
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10
fs/cifs/cifsfs.c
View File

@ -58,6 +58,7 @@ bool traceSMB;
bool enable_oplocks = true;
bool linuxExtEnabled = true;
bool lookupCacheEnabled = true;
bool disable_legacy_dialects; /* false by default */
unsigned int global_secflags = CIFSSEC_DEF;
/* unsigned int ntlmv2_support = 0; */
unsigned int sign_CIFS_PDUs = 1;
@ -83,6 +84,15 @@ MODULE_PARM_DESC(cifs_max_pending, "Simultaneous requests to server for "
module_param(enable_oplocks, bool, 0644);
MODULE_PARM_DESC(enable_oplocks, "Enable or disable oplocks. Default: y/Y/1");
module_param(disable_legacy_dialects, bool, 0644);
MODULE_PARM_DESC(disable_legacy_dialects, "To improve security it may be "
"helpful to restrict the ability to "
"override the default dialects (SMB2.1, "
"SMB3 and SMB3.02) on mount with old "
"dialects (CIFS/SMB1 and SMB2) since "
"vers=1.0 (CIFS/SMB1) and vers=2.0 are weaker"
" and less secure. Default: n/N/0");
extern mempool_t *cifs_sm_req_poolp;
extern mempool_t *cifs_req_poolp;
extern mempool_t *cifs_mid_poolp;

19
fs/cifs/cifsglob.h
View File

@ -1700,16 +1700,17 @@ GLOBAL_EXTERN atomic_t smBufAllocCount;
GLOBAL_EXTERN atomic_t midCount;
/* Misc globals */
GLOBAL_EXTERN bool enable_oplocks; /* enable or disable oplocks */
GLOBAL_EXTERN bool lookupCacheEnabled;
GLOBAL_EXTERN unsigned int global_secflags; /* if on, session setup sent
extern bool enable_oplocks; /* enable or disable oplocks */
extern bool lookupCacheEnabled;
extern unsigned int global_secflags; /* if on, session setup sent
with more secure ntlmssp2 challenge/resp */
GLOBAL_EXTERN unsigned int sign_CIFS_PDUs; /* enable smb packet signing */
GLOBAL_EXTERN bool linuxExtEnabled;/*enable Linux/Unix CIFS extensions*/
GLOBAL_EXTERN unsigned int CIFSMaxBufSize; /* max size not including hdr */
GLOBAL_EXTERN unsigned int cifs_min_rcv; /* min size of big ntwrk buf pool */
GLOBAL_EXTERN unsigned int cifs_min_small; /* min size of small buf pool */
GLOBAL_EXTERN unsigned int cifs_max_pending; /* MAX requests at once to server*/
extern unsigned int sign_CIFS_PDUs; /* enable smb packet signing */
extern bool linuxExtEnabled;/*enable Linux/Unix CIFS extensions*/
extern unsigned int CIFSMaxBufSize; /* max size not including hdr */
extern unsigned int cifs_min_rcv; /* min size of big ntwrk buf pool */
extern unsigned int cifs_min_small; /* min size of small buf pool */
extern unsigned int cifs_max_pending; /* MAX requests at once to server*/
extern bool disable_legacy_dialects; /* forbid vers=1.0 and vers=2.0 mounts */
#ifdef CONFIG_CIFS_ACL
GLOBAL_EXTERN struct rb_root uidtree;

9
fs/cifs/connect.c
View File

@ -61,6 +61,7 @@
#define RFC1001_PORT 139
extern mempool_t *cifs_req_poolp;
extern bool disable_legacy_dialects;
/* FIXME: should these be tunable? */
#define TLINK_ERROR_EXPIRE (1 * HZ)
@ -1146,10 +1147,18 @@ cifs_parse_smb_version(char *value, struct smb_vol *vol)
switch (match_token(value, cifs_smb_version_tokens, args)) {
case Smb_1:
if (disable_legacy_dialects) {
cifs_dbg(VFS, "mount with legacy dialect disabled\n");
return 1;
}
vol->ops = &smb1_operations;
vol->vals = &smb1_values;
break;
case Smb_20:
if (disable_legacy_dialects) {
cifs_dbg(VFS, "mount with legacy dialect disabled\n");
return 1;
}
vol->ops = &smb20_operations;
vol->vals = &smb20_values;
break;