[PATCH 3.14 04/20] fs/cifs: correctly to anonymous authentication via NTLMSSP

Greg Kroah-Hartman
2016-05-30T22:10:18Z

From: Stefan Metzmacher <metze@samba.org>

commit cfda35d98298131bf38fbad3ce4cd5ecb3cf18db upstream.

See [MS-NLMP] 3.2.5.1.2 Server Receives an AUTHENTICATE_MESSAGE from the Client:

...
Set NullSession to FALSE
If (AUTHENTICATE_MESSAGE.UserNameLen == 0 AND
AUTHENTICATE_MESSAGE.NtChallengeResponse.Length == 0 AND
(AUTHENTICATE_MESSAGE.LmChallengeResponse == Z(1)
OR
AUTHENTICATE_MESSAGE.LmChallengeResponse.Length == 0))
-- Special case: client requested anonymous authentication
Set NullSession to TRUE
...

Only server which map unknown users to guest will allow
access using a non-null NTChallengeResponse.

For Samba it's the "map to guest = bad user" option.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11913

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/cifs/sess.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)

--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -399,19 +399,27 @@ int build_ntlmssp_auth_blob(unsigned cha
sec_blob->LmChallengeResponse.MaximumLength = 0;

sec_blob->NtChallengeResponse.BufferOffset = cpu_to_le32(tmp - pbuffer);
- rc = setup_ntlmv2_rsp(ses, nls_cp);
- if (rc) {
- cifs_dbg(VFS, "Error %d during NTLMSSP authentication\n", rc);
- goto setup_ntlmv2_ret;
- }
- memcpy(tmp, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
- ses->auth_key.len - CIFS_SESS_KEY_SIZE);
- tmp += ses->auth_key.len - CIFS_SESS_KEY_SIZE;
+ if (ses->user_name != NULL) {
+ rc = setup_ntlmv2_rsp(ses, nls_cp);
+ if (rc) {
+ cifs_dbg(VFS, "Error %d during NTLMSSP authentication\n", rc);
+ goto setup_ntlmv2_ret;
+ }
+ memcpy(tmp, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
+ ses->auth_key.len - CIFS_SESS_KEY_SIZE);
+ tmp += ses->auth_key.len - CIFS_SESS_KEY_SIZE;

- sec_blob->NtChallengeResponse.Length =
- cpu_to_le16(ses->auth_key.len - CIFS_SESS_KEY_SIZE);
- sec_blob->NtChallengeResponse.MaximumLength =
- cpu_to_le16(ses->auth_key.len - CIFS_SESS_KEY_SIZE);
+ sec_blob->NtChallengeResponse.Length =
+ cpu_to_le16(ses->auth_key.len - CIFS_SESS_KEY_SIZE);
+ sec_blob->NtChallengeResponse.MaximumLength =
+ cpu_to_le16(ses->auth_key.len - CIFS_SESS_KEY_SIZE);
+ } else {
+ /*
+ * don't send an NT Response for anonymous access
+ */
+ sec_blob->NtChallengeResponse.Length = 0;
+ sec_blob->NtChallengeResponse.MaximumLength = 0;
+ }

if (ses->domainName == NULL) {
sec_blob->DomainName.BufferOffset = cpu_to_le32(tmp - pbuffer);