NTLM auth and sign - Define crypto hash functions and create and send keys needed for key exchange

Mark dependency on crypto modules in Kconfig.

Defining per structures sdesc and cifs_secmech which are used to store
crypto hash functions and contexts.  They are stored per smb connection
and used for all auth mechs to genereate hash values and signatures.

Allocate crypto hashing functions, security descriptiors, and respective
contexts when a smb/tcp connection is established.
Release them when a tcp/smb connection is taken down.

md5 and hmac-md5 are two crypto hashing functions that are used
throught the life of an smb/tcp connection by various functions that
calcualte signagure and ntlmv2 hash, HMAC etc.

structure ntlmssp_auth is defined as per smb connection.

ntlmssp_auth holds ciphertext which is genereated by rc4/arc4 encryption of
secondary key, a nonce using ntlmv2 session key and sent in the session key
field of the type 3 message sent by the client during ntlmssp
negotiation/exchange

A key is exchanged with the server if client indicates so in flags in
type 1 messsage and server agrees in flag in type 2 message of ntlmssp
negotiation.  If both client and agree, a key sent by client in
type 3 message of ntlmssp negotiation in the session key field.
The key is a ciphertext generated off of secondary key, a nonce, using
ntlmv2 hash via rc4/arc4.

Signing works for ntlmssp in this patch. The sequence number within
the server structure needs to be zero until session is established
i.e. till type 3 packet of ntlmssp exchange of a to be very first
smb session on that smb connection is sent.

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 19 insertions, 7 deletions

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index b2934683bd08..d998c4f7aae5 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -404,7 +404,7 @@ static int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len,
         /* In particular we can examine sign flags */
         /* BB spec says that if AvId field of MsvAvTimestamp is populated then
                 we must set the MIC field of the AUTHENTICATE_MESSAGE */
-
+        ses->ntlmssp.server_flags = le32_to_cpu(pblob->NegotiateFlags);
         tioffset = cpu_to_le16(pblob->TargetInfoArray.BufferOffset);
         tilen = cpu_to_le16(pblob->TargetInfoArray.Length);
         ses->tilen = tilen;
@@ -440,10 +440,12 @@ static void build_ntlmssp_negotiate_blob(unsigned char *pbuffer,
                 NTLMSSP_NEGOTIATE_128 | NTLMSSP_NEGOTIATE_UNICODE |
                 NTLMSSP_NEGOTIATE_NTLM;
         if (ses->server->secMode &
-           (SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED))
+                        (SECMODE_SIGN_REQUIRED | SECMODE_SIGN_ENABLED)) {
                 flags |= NTLMSSP_NEGOTIATE_SIGN;
-        if (ses->server->secMode & SECMODE_SIGN_REQUIRED)
-                flags |= NTLMSSP_NEGOTIATE_ALWAYS_SIGN;
+                if (!ses->server->session_estab)
+                        flags |= NTLMSSP_NEGOTIATE_KEY_XCH |
+                                NTLMSSP_NEGOTIATE_EXTENDED_SEC;
+        }
 
         sec_blob->NegotiateFlags |= cpu_to_le32(flags);
 
@@ -543,9 +545,19 @@ static int build_ntlmssp_auth_blob(unsigned char *pbuffer,
         sec_blob->WorkstationName.MaximumLength = 0;
         tmp += 2;
 
-        sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
-        sec_blob->SessionKey.Length = 0;
-        sec_blob->SessionKey.MaximumLength = 0;
+        if ((ses->ntlmssp.server_flags & NTLMSSP_NEGOTIATE_KEY_XCH) &&
+                        !calc_seckey(ses)) {
+                memcpy(tmp, ses->ntlmssp.ciphertext, CIFS_CPHTXT_SIZE);
+                sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
+                sec_blob->SessionKey.Length = cpu_to_le16(CIFS_CPHTXT_SIZE);
+                sec_blob->SessionKey.MaximumLength =
+                                cpu_to_le16(CIFS_CPHTXT_SIZE);
+                tmp += CIFS_CPHTXT_SIZE;
+        } else {
+                sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - pbuffer);
+                sec_blob->SessionKey.Length = 0;
+                sec_blob->SessionKey.MaximumLength = 0;
+        }
 
 setup_ntlmv2_ret:
         *buflen = tmp - pbuffer;