[PATCH 5.15 100/128] ksmbd: disable SMB2_GLOBAL_CAP_ENCRYPTION for SMB 3.1.1

Greg Kroah-Hartman
2021-12-27T15:48:13Z

From: Marcos Del Sol Vives <marcos@orca.pet>

commit 83912d6d55be10d65b5268d1871168b9ebe1ec4b upstream.

According to the official Microsoft MS-SMB2 document section 3.3.5.4, this
flag should be used only for 3.0 and 3.0.2 dialects. Setting it for 3.1.1
is a violation of the specification.

This causes my Windows 10 client to detect an anomaly in the negotiation,
and disable encryption entirely despite being explicitly enabled in ksmbd,
causing all data transfers to go in plain text.

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org # v5.15
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Marcos Del Sol Vives <marcos@orca.pet>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ksmbd/smb2ops.c | 3 ---
fs/ksmbd/smb2pdu.c | 25 +++++++++++++++++++++----
2 files changed, 21 insertions(+), 7 deletions(-)

--- a/fs/ksmbd/smb2ops.c
+++ b/fs/ksmbd/smb2ops.c
@@ -272,9 +272,6 @@ int init_smb3_11_server(struct ksmbd_con
if (server_conf.flags & KSMBD_GLOBAL_FLAG_SMB2_LEASES)
conn->vals->capabilities |= SMB2_GLOBAL_CAP_LEASING;

- if (conn->cipher_type)
- conn->vals->capabilities |= SMB2_GLOBAL_CAP_ENCRYPTION;
-
if (server_conf.flags & KSMBD_GLOBAL_FLAG_SMB3_MULTICHANNEL)
conn->vals->capabilities |= SMB2_GLOBAL_CAP_MULTI_CHANNEL;

--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -917,6 +917,25 @@ static void decode_encrypt_ctxt(struct k
}
}

+/**
+ * smb3_encryption_negotiated() - checks if server and client agreed on enabling encryption
+ * @conn: smb connection
+ *
+ * Return: true if connection should be encrypted, else false
+ */
+static bool smb3_encryption_negotiated(struct ksmbd_conn *conn)
+{
+ if (!conn->ops->generate_encryptionkey)
+ return false;
+
+ /*
+ * SMB 3.0 and 3.0.2 dialects use the SMB2_GLOBAL_CAP_ENCRYPTION flag.
+ * SMB 3.1.1 uses the cipher_type field.
+ */
+ return (conn->vals->capabilities & SMB2_GLOBAL_CAP_ENCRYPTION) ||
+ conn->cipher_type;
+}
+
static void decode_compress_ctxt(struct ksmbd_conn *conn,
struct smb2_compression_ctx *pneg_ctxt)
{
@@ -1471,8 +1490,7 @@ static int ntlm_authenticate(struct ksmb
(req->SecurityMode & SMB2_NEGOTIATE_SIGNING_REQUIRED))
sess->sign = true;

- if (conn->vals->capabilities & SMB2_GLOBAL_CAP_ENCRYPTION &&
- conn->ops->generate_encryptionkey &&
+ if (smb3_encryption_negotiated(conn) &&
!(req->Flags & SMB2_SESSION_REQ_FLAG_BINDING)) {
rc = conn->ops->generate_encryptionkey(sess);
if (rc) {
@@ -1562,8 +1580,7 @@ static int krb5_authenticate(struct ksmb
(req->SecurityMode & SMB2_NEGOTIATE_SIGNING_REQUIRED))
sess->sign = true;

- if ((conn->vals->capabilities & SMB2_GLOBAL_CAP_ENCRYPTION) &&
- conn->ops->generate_encryptionkey) {
+ if (smb3_encryption_negotiated(conn)) {
retval = conn->ops->generate_encryptionkey(sess);
if (retval) {
ksmbd_debug(SMB,