cifs: try opening channels after mounting

After doing mount() successfully we call cifs_try_adding_channels()
which will open as many channels as it can.

Channels are closed when the master session is closed.

The master connection becomes the first channel.

,-------------> global cifs_tcp_ses_list <-------------------------.
|                                                                  |
'- TCP_Server_Info  <-->  TCP_Server_Info  <-->  TCP_Server_Info <-'
      (master con)           (chan#1 con)         (chan#2 con)
      |      ^                    ^                    ^
      v      '--------------------|--------------------'
   cifs_ses                       |
   - chan_count = 3               |
   - chans[] ---------------------'
   - smb3signingkey[]
      (master signing key)

Note how channel connections don't have sessions. That's because
cifs_ses can only be part of one linked list (list_head are internal
to the elements).

For signing keys, each channel has its own signing key which must be
used only after the channel has been bound. While it's binding it must
use the master session signing key.

For encryption keys, since channel connections do not have sessions
attached we must now find matching session by looping over all sessions
in smb2_get_enc_key().

Each channel is opened like a regular server connection but at the
session setup request step it must set the
SMB2_SESSION_REQ_FLAG_BINDING flag and use the session id to bind to.

Finally, while sending in compound_send_recv() for requests that
aren't negprot, ses-setup or binding related, use a channel by cycling
through the available ones (round-robin).

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 109 insertions, 27 deletions

diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
index c6ef52e44408..86501239cef5 100644
--- a/fs/cifs/smb2transport.c
+++ b/fs/cifs/smb2transport.c
@@ -98,6 +98,61 @@ err:
 	return rc;
 }
 
+
+static
+int smb2_get_sign_key(__u64 ses_id, struct TCP_Server_Info *server, u8 *key)
+{
+	struct cifs_chan *chan;
+	struct cifs_ses *ses = NULL;
+	int i;
+	int rc = 0;
+
+	spin_lock(&cifs_tcp_ses_lock);
+
+	list_for_each_entry(server, &cifs_tcp_ses_list, tcp_ses_list) {
+		list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
+			if (ses->Suid == ses_id)
+				goto found;
+		}
+	}
+	cifs_server_dbg(VFS, "%s: Could not find session 0x%llx\n",
+			__func__, ses_id);
+	rc = -ENOENT;
+	goto out;
+
+found:
+	if (ses->binding) {
+		/*
+		 * If we are in the process of binding a new channel
+		 * to an existing session, use the master connection
+		 * session key
+		 */
+		memcpy(key, ses->smb3signingkey, SMB3_SIGN_KEY_SIZE);
+		goto out;
+	}
+
+	/*
+	 * Otherwise, use the channel key.
+	 */
+
+	for (i = 0; i < ses->chan_count; i++) {
+		chan = ses->chans + i;
+		if (chan->server == server) {
+			memcpy(key, chan->signkey, SMB3_SIGN_KEY_SIZE);
+			goto out;
+		}
+	}
+
+	cifs_dbg(VFS,
+		 "%s: Could not find channel signing key for session 0x%llx\n",
+		 __func__, ses_id);
+	rc = -ENOENT;
+
+out:
+	spin_unlock(&cifs_tcp_ses_lock);
+	return rc;
+}
+
 static struct cifs_ses *
 smb2_find_smb_ses_unlocked(struct TCP_Server_Info *server, __u64 ses_id)
 {
@@ -328,21 +383,41 @@ generate_smb3signingkey(struct cifs_ses *ses,
 {
 	int rc;
 
-	rc = generate_key(ses, ptriplet->signing.label,
-			  ptriplet->signing.context, ses->smb3signingkey,
-			  SMB3_SIGN_KEY_SIZE);
-	if (rc)
-		return rc;
-
-	rc = generate_key(ses, ptriplet->encryption.label,
-			  ptriplet->encryption.context, ses->smb3encryptionkey,
-			  SMB3_SIGN_KEY_SIZE);
-	if (rc)
-		return rc;
+	/*
+	 * All channels use the same encryption/decryption keys but
+	 * they have their own signing key.
+	 *
+	 * When we generate the keys, check if it is for a new channel
+	 * (binding) in which case we only need to generate a signing
+	 * key and store it in the channel as to not overwrite the
+	 * master connection signing key stored in the session
+	 */
 
-	rc = generate_key(ses, ptriplet->decryption.label,
-			  ptriplet->decryption.context,
-			  ses->smb3decryptionkey, SMB3_SIGN_KEY_SIZE);
+	if (ses->binding) {
+		rc = generate_key(ses, ptriplet->signing.label,
+				  ptriplet->signing.context,
+				  cifs_ses_binding_channel(ses)->signkey,
+				  SMB3_SIGN_KEY_SIZE);
+		if (rc)
+			return rc;
+	} else {
+		rc = generate_key(ses, ptriplet->signing.label,
+				  ptriplet->signing.context,
+				  ses->smb3signingkey,
+				  SMB3_SIGN_KEY_SIZE);
+		if (rc)
+			return rc;
+		rc = generate_key(ses, ptriplet->encryption.label,
+				  ptriplet->encryption.context,
+				  ses->smb3encryptionkey,
+				  SMB3_SIGN_KEY_SIZE);
+		rc = generate_key(ses, ptriplet->decryption.label,
+				  ptriplet->decryption.context,
+				  ses->smb3decryptionkey,
+				  SMB3_SIGN_KEY_SIZE);
+		if (rc)
+			return rc;
+	}
 
 	if (rc)
 		return rc;
@@ -431,21 +506,19 @@ smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 	unsigned char *sigptr = smb3_signature;
 	struct kvec *iov = rqst->rq_iov;
 	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)iov[0].iov_base;
-	struct cifs_ses *ses;
 	struct shash_desc *shash = &server->secmech.sdesccmacaes->shash;
 	struct smb_rqst drqst;
+	u8 key[SMB3_SIGN_KEY_SIZE];
 
-	ses = smb2_find_smb_ses(server, shdr->SessionId);
-	if (!ses) {
-		cifs_server_dbg(VFS, "%s: Could not find session\n", __func__);
+	rc = smb2_get_sign_key(shdr->SessionId, server, key);
+	if (rc)
 		return 0;
-	}
 
 	memset(smb3_signature, 0x0, SMB2_CMACAES_SIZE);
 	memset(shdr->Signature, 0x0, SMB2_SIGNATURE_SIZE);
 
 	rc = crypto_shash_setkey(server->secmech.cmacaes,
-				 ses->smb3signingkey, SMB2_CMACAES_SIZE);
+				 key, SMB2_CMACAES_SIZE);
 	if (rc) {
 		cifs_server_dbg(VFS, "%s: Could not set key for cmac aes\n", __func__);
 		return rc;
@@ -494,16 +567,25 @@ static int
 smb2_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 {
 	int rc = 0;
-	struct smb2_sync_hdr *shdr =
-			(struct smb2_sync_hdr *)rqst->rq_iov[0].iov_base;
+	struct smb2_sync_hdr *shdr;
+	struct smb2_sess_setup_req *ssr;
+	bool is_binding;
+	bool is_signed;
 
-	if (!(shdr->Flags & SMB2_FLAGS_SIGNED) ||
-	    server->tcpStatus == CifsNeedNegotiate)
-		return rc;
+	shdr = (struct smb2_sync_hdr *)rqst->rq_iov[0].iov_base;
+	ssr = (struct smb2_sess_setup_req *)shdr;
+
+	is_binding = shdr->Command == SMB2_SESSION_SETUP &&
+		(ssr->Flags & SMB2_SESSION_REQ_FLAG_BINDING);
+	is_signed = shdr->Flags & SMB2_FLAGS_SIGNED;
 
-	if (!server->session_estab) {
+	if (!is_signed)
+		return 0;
+	if (server->tcpStatus == CifsNeedNegotiate)
+		return 0;
+	if (!is_binding && !server->session_estab) {
 		strncpy(shdr->Signature, "BSRSPYL", 8);
-		return rc;
+		return 0;
 	}
 
 	rc = server->ops->calc_signature(rqst, server);