ksmbd: add buffer validation in session setup

Make sure the security buffer's length/offset are valid with regards to
the packet length.
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Marios Makassikis <mmakassikis@freebox.fr>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/auth.c

@@ -298,8 +298,8 @@ int ksmbd_decode_ntlmssp_auth_blob(struct authenticate_message *authblob,
 				   int blob_len, struct ksmbd_session *sess)
 {
 	char *domain_name;
-	unsigned int lm_off, nt_off;
-	unsigned short nt_len;
+	unsigned int nt_off, dn_off;
+	unsigned short nt_len, dn_len;
 	int ret;
 
 	if (blob_len < sizeof(struct authenticate_message)) {
@@ -314,15 +314,17 @@ int ksmbd_decode_ntlmssp_auth_blob(struct authenticate_message *authblob,
 		return -EINVAL;
 	}
 
-	lm_off = le32_to_cpu(authblob->LmChallengeResponse.BufferOffset);
 	nt_off = le32_to_cpu(authblob->NtChallengeResponse.BufferOffset);
 	nt_len = le16_to_cpu(authblob->NtChallengeResponse.Length);
+	dn_off = le32_to_cpu(authblob->DomainName.BufferOffset);
+	dn_len = le16_to_cpu(authblob->DomainName.Length);
+
+	if (blob_len < (u64)dn_off + dn_len || blob_len < (u64)nt_off + nt_len)
+		return -EINVAL;
 
 	/* TODO : use domain name that imported from configuration file */
-	domain_name = smb_strndup_from_utf16((const char *)authblob +
-			le32_to_cpu(authblob->DomainName.BufferOffset),
-			le16_to_cpu(authblob->DomainName.Length), true,
-			sess->conn->local_nls);
+	domain_name = smb_strndup_from_utf16((const char *)authblob + dn_off,
+					     dn_len, true, sess->conn->local_nls);
 	if (IS_ERR(domain_name))
 		return PTR_ERR(domain_name);
 

fs/ksmbd/smb2pdu.c

@@ -1257,19 +1257,13 @@ static int generate_preauth_hash(struct ksmbd_work *work)
 	return 0;
 }
 
-static int decode_negotiation_token(struct ksmbd_work *work,
-				    struct negotiate_message *negblob)
+static int decode_negotiation_token(struct ksmbd_conn *conn,
+				    struct negotiate_message *negblob,
+				    size_t sz)
 {
-	struct ksmbd_conn *conn = work->conn;
-	struct smb2_sess_setup_req *req;
-	int sz;
-
 	if (!conn->use_spnego)
 		return -EINVAL;
 
-	req = work->request_buf;
-	sz = le16_to_cpu(req->SecurityBufferLength);
-
 	if (ksmbd_decode_negTokenInit((char *)negblob, sz, conn)) {
 		if (ksmbd_decode_negTokenTarg((char *)negblob, sz, conn)) {
 			conn->auth_mechs |= KSMBD_AUTH_NTLMSSP;
@@ -1281,9 +1275,9 @@ static int decode_negotiation_token(struct ksmbd_work *work,
 }
 
 static int ntlm_negotiate(struct ksmbd_work *work,
-			  struct negotiate_message *negblob)
+			  struct negotiate_message *negblob,
+			  size_t negblob_len)
 {
-	struct smb2_sess_setup_req *req = work->request_buf;
 	struct smb2_sess_setup_rsp *rsp = work->response_buf;
 	struct challenge_message *chgblob;
 	unsigned char *spnego_blob = NULL;
@@ -1292,8 +1286,7 @@ static int ntlm_negotiate(struct ksmbd_work *work,
 	int sz, rc;
 
 	ksmbd_debug(SMB, "negotiate phase\n");
-	sz = le16_to_cpu(req->SecurityBufferLength);
-	rc = ksmbd_decode_ntlmssp_neg_blob(negblob, sz, work->sess);
+	rc = ksmbd_decode_ntlmssp_neg_blob(negblob, negblob_len, work->sess);
 	if (rc)
 		return rc;
 
@@ -1361,12 +1354,23 @@ static struct ksmbd_user *session_user(struct ksmbd_conn *conn,
 	struct authenticate_message *authblob;
 	struct ksmbd_user *user;
 	char *name;
-	int sz;
+	unsigned int auth_msg_len, name_off, name_len, secbuf_len;
 
+	secbuf_len = le16_to_cpu(req->SecurityBufferLength);
+	if (secbuf_len < sizeof(struct authenticate_message)) {
+		ksmbd_debug(SMB, "blob len %d too small\n", secbuf_len);
+		return NULL;
+	}
 	authblob = user_authblob(conn, req);
-	sz = le32_to_cpu(authblob->UserName.BufferOffset);
-	name = smb_strndup_from_utf16((const char *)authblob + sz,
-				      le16_to_cpu(authblob->UserName.Length),
+	name_off = le32_to_cpu(authblob->UserName.BufferOffset);
+	name_len = le16_to_cpu(authblob->UserName.Length);
+	auth_msg_len = le16_to_cpu(req->SecurityBufferOffset) + secbuf_len;
+
+	if (auth_msg_len < (u64)name_off + name_len)
+		return NULL;
+
+	name = smb_strndup_from_utf16((const char *)authblob + name_off,
+				      name_len,
 				      true,
 				      conn->local_nls);
 	if (IS_ERR(name)) {
@@ -1612,6 +1616,7 @@ int smb2_sess_setup(struct ksmbd_work *work)
 	struct smb2_sess_setup_rsp *rsp = work->response_buf;
 	struct ksmbd_session *sess;
 	struct negotiate_message *negblob;
+	unsigned int negblob_len, negblob_off;
 	int rc = 0;
 
 	ksmbd_debug(SMB, "Received request for session setup\n");
@@ -1692,10 +1697,16 @@ int smb2_sess_setup(struct ksmbd_work *work)
 	if (sess->state == SMB2_SESSION_EXPIRED)
 		sess->state = SMB2_SESSION_IN_PROGRESS;
 
+	negblob_off = le16_to_cpu(req->SecurityBufferOffset);
+	negblob_len = le16_to_cpu(req->SecurityBufferLength);
+	if (negblob_off < (offsetof(struct smb2_sess_setup_req, Buffer) - 4) ||
+	    negblob_len < offsetof(struct negotiate_message, NegotiateFlags))
+		return -EINVAL;
+
 	negblob = (struct negotiate_message *)((char *)&req->hdr.ProtocolId +
-			le16_to_cpu(req->SecurityBufferOffset));
+			negblob_off);
 
-	if (decode_negotiation_token(work, negblob) == 0) {
+	if (decode_negotiation_token(conn, negblob, negblob_len) == 0) {
 		if (conn->mechToken)
 			negblob = (struct negotiate_message *)conn->mechToken;
 	}
@@ -1719,7 +1730,7 @@ int smb2_sess_setup(struct ksmbd_work *work)
 			sess->Preauth_HashValue = NULL;
 		} else if (conn->preferred_auth_mech == KSMBD_AUTH_NTLMSSP) {
 			if (negblob->MessageType == NtLmNegotiate) {
-				rc = ntlm_negotiate(work, negblob);
+				rc = ntlm_negotiate(work, negblob, negblob_len);
 				if (rc)
 					goto out_err;
 				rsp->hdr.Status =