cifs: Add a variable specific to NTLMSSP for key exchange.

Add a variable specific to NTLMSSP authentication to determine
whether to exchange keys during negotiation and authentication phases.

Since session key for smb1 is per smb connection, once a very first
sesion is established, there is no need for key exchange during
subsequent session setups. As a result, smb1 session setup code sets this
variable as false.

Since session key for smb2 and smb3 is per smb connection, we need to
exchange keys to generate session key for every sesion being established.
As a result, smb2/3 session setup code sets this variable as true.

Acked-by: Jeff Layton <jlayton@samba.org>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsglob.h

@@ -131,6 +131,7 @@ struct cifs_secmech {
 
 /* per smb session structure/fields */
 struct ntlmssp_auth {
+	bool sesskey_per_smbsess; /* whether session key is per smb session */
 	__u32 client_flags; /* sent by client in type 1 ntlmsssp exchange */
 	__u32 server_flags; /* sent by server in type 2 ntlmssp exchange */
 	unsigned char ciphertext[CIFS_CPHTXT_SIZE]; /* sent to server */

fs/cifs/sess.c

@@ -428,7 +428,8 @@ void build_ntlmssp_negotiate_blob(unsigned char *pbuffer,
 		NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_NEGOTIATE_EXTENDED_SEC;
 	if (ses->server->sign) {
 		flags |= NTLMSSP_NEGOTIATE_SIGN;
-		if (!ses->server->session_estab)
+		if (!ses->server->session_estab ||
+				ses->ntlmssp->sesskey_per_smbsess)
 			flags |= NTLMSSP_NEGOTIATE_KEY_XCH;
 	}
 
@@ -466,7 +467,8 @@ int build_ntlmssp_auth_blob(unsigned char *pbuffer,
 		NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_NEGOTIATE_EXTENDED_SEC;
 	if (ses->server->sign) {
 		flags |= NTLMSSP_NEGOTIATE_SIGN;
-		if (!ses->server->session_estab)
+		if (!ses->server->session_estab ||
+				ses->ntlmssp->sesskey_per_smbsess)
 			flags |= NTLMSSP_NEGOTIATE_KEY_XCH;
 	}
 
@@ -641,6 +643,8 @@ CIFS_SessSetup(const unsigned int xid, struct cifs_ses *ses,
 		ses->ntlmssp = kmalloc(sizeof(struct ntlmssp_auth), GFP_KERNEL);
 		if (!ses->ntlmssp)
 			return -ENOMEM;
+		ses->ntlmssp->sesskey_per_smbsess = false;
+
 	}
 
 ssetup_ntlmssp_authenticate:

fs/cifs/smb2pdu.c

@@ -491,6 +491,7 @@ SMB2_sess_setup(const unsigned int xid, struct cifs_ses *ses,
 	ses->ntlmssp = kmalloc(sizeof(struct ntlmssp_auth), GFP_KERNEL);
 	if (!ses->ntlmssp)
 		return -ENOMEM;
+	ses->ntlmssp->sesskey_per_smbsess = true;
 
 	/* FIXME: allow for other auth types besides NTLMSSP (e.g. krb5) */
 	ses->sectype = RawNTLMSSP;