6 files changed, 90 insertions, 4 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index d9ea7ada1378..f918a998a087 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -384,6 +384,7 @@ struct smb_version_operations {
         int (*clone_range)(const unsigned int, struct cifsFileInfo *src_file,
                         struct cifsFileInfo *target_file, u64 src_off, u64 len,
                         u64 dest_off);
+        int (*validate_negotiate)(const unsigned int, struct cifs_tcon *);
 };
 
 struct smb_version_values {
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index a3968eeb6fac..757da3e54d3d 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -1319,6 +1319,7 @@ struct smb_version_operations smb30_operations = {
         .create_lease_buf = smb3_create_lease_buf,
         .parse_lease_buf = smb3_parse_lease_buf,
         .clone_range = smb2_clone_range,
+        .validate_negotiate = smb3_validate_negotiate,
 };
 
 struct smb_version_values smb20_values = {
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 1e136eee3ea6..2013234b73ad 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -454,6 +454,81 @@ neg_exit:
         return rc;
 }
 
+int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
+{
+        int rc = 0;
+        struct validate_negotiate_info_req vneg_inbuf;
+        struct validate_negotiate_info_rsp *pneg_rsp;
+        u32 rsplen;
+
+        cifs_dbg(FYI, "validate negotiate\n");
+
+        /*
+         * validation ioctl must be signed, so no point sending this if we
+         * can not sign it.  We could eventually change this to selectively
+         * sign just this, the first and only signed request on a connection.
+         * This is good enough for now since a user who wants better security
+         * would also enable signing on the mount. Having validation of
+         * negotiate info for signed connections helps reduce attack vectors
+         */
+        if (tcon->ses->server->sign == false)
+                return 0; /* validation requires signing */
+
+        vneg_inbuf.Capabilities =
+                        cpu_to_le32(tcon->ses->server->vals->req_capabilities);
+        memcpy(vneg_inbuf.Guid, cifs_client_guid, SMB2_CLIENT_GUID_SIZE);
+
+        if (tcon->ses->sign)
+                vneg_inbuf.SecurityMode =
+                        cpu_to_le16(SMB2_NEGOTIATE_SIGNING_REQUIRED);
+        else if (global_secflags & CIFSSEC_MAY_SIGN)
+                vneg_inbuf.SecurityMode =
+                        cpu_to_le16(SMB2_NEGOTIATE_SIGNING_ENABLED);
+        else
+                vneg_inbuf.SecurityMode = 0;
+
+        vneg_inbuf.DialectCount = cpu_to_le16(1);
+        vneg_inbuf.Dialects[0] =
+                cpu_to_le16(tcon->ses->server->vals->protocol_id);
+
+        rc = SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
+                FSCTL_VALIDATE_NEGOTIATE_INFO, true /* is_fsctl */,
+                (char *)&vneg_inbuf, sizeof(struct validate_negotiate_info_req),
+                (char **)&pneg_rsp, &rsplen);
+
+        if (rc != 0) {
+                cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", rc);
+                return -EIO;
+        }
+
+        if (rsplen != sizeof(struct validate_negotiate_info_rsp)) {
+                cifs_dbg(VFS, "invalid size of protocol negotiate response\n");
+                return -EIO;
+        }
+
+        /* check validate negotiate info response matches what we got earlier */
+        if (pneg_rsp->Dialect !=
+                        cpu_to_le16(tcon->ses->server->vals->protocol_id))
+                goto vneg_out;
+
+        if (pneg_rsp->SecurityMode != cpu_to_le16(tcon->ses->server->sec_mode))
+                goto vneg_out;
+
+        /* do not validate server guid because not saved at negprot time yet */
+
+        if ((le32_to_cpu(pneg_rsp->Capabilities) | SMB2_NT_FIND |
+              SMB2_LARGE_FILES) != tcon->ses->server->capabilities)
+                goto vneg_out;
+
+        /* validate negotiate successful */
+        cifs_dbg(FYI, "validate negotiate info successful\n");
+        return 0;
+
+vneg_out:
+        cifs_dbg(VFS, "protocol revalidation - security settings mismatch\n");
+        return -EIO;
+}
+
 int
 SMB2_sess_setup(const unsigned int xid, struct cifs_ses *ses,
                 const struct nls_table *nls_cp)
@@ -829,6 +904,8 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
             ((tcon->share_flags & SHI1005_FLAGS_DFS) == 0))
                 cifs_dbg(VFS, "DFS capability contradicts DFS flag\n");
         init_copy_chunk_defaults(tcon);
+        if (tcon->ses->server->ops->validate_negotiate)
+                rc = tcon->ses->server->ops->validate_negotiate(xid, tcon);
 tcon_exit:
         free_rsp_buf(resp_buftype, rsp);
         kfree(unc_path);
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index f88320bbb477..2022c542ea3a 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -577,13 +577,19 @@ struct copychunk_ioctl_rsp {
         __le32 TotalBytesWritten;
 } __packed;
 
-/* Response and Request are the same format */
-struct validate_negotiate_info {
+struct validate_negotiate_info_req {
         __le32 Capabilities;
         __u8   Guid[SMB2_CLIENT_GUID_SIZE];
         __le16 SecurityMode;
         __le16 DialectCount;
-        __le16 Dialect[1];
+        __le16 Dialects[1]; /* dialect (someday maybe list) client asked for */
+} __packed;
+
+struct validate_negotiate_info_rsp {
+        __le32 Capabilities;
+        __u8   Guid[SMB2_CLIENT_GUID_SIZE];
+        __le16 SecurityMode;
+        __le16 Dialect; /* Dialect in use for the connection */
 } __packed;
 
 #define RSS_CAPABLE     0x00000001
diff --git a/fs/cifs/smb2proto.h b/fs/cifs/smb2proto.h
index b4eea105b08c..93adc64666f3 100644
--- a/fs/cifs/smb2proto.h
+++ b/fs/cifs/smb2proto.h
@@ -162,5 +162,6 @@ extern int smb2_lockv(const unsigned int xid, struct cifs_tcon *tcon,
                       struct smb2_lock_element *buf);
 extern int SMB2_lease_break(const unsigned int xid, struct cifs_tcon *tcon,
                             __u8 *lease_key, const __le32 lease_state);
+extern int smb3_validate_negotiate(const unsigned int, struct cifs_tcon *);
 
 #endif                  /* _SMB2PROTO_H */
diff --git a/fs/cifs/smbfsctl.h b/fs/cifs/smbfsctl.h
index a4b2391fe66e..0e538b5c9622 100644
--- a/fs/cifs/smbfsctl.h
+++ b/fs/cifs/smbfsctl.h
@@ -90,7 +90,7 @@
 #define FSCTL_LMR_REQUEST_RESILIENCY 0x001401D4 /* BB add struct */
 #define FSCTL_LMR_GET_LINK_TRACK_INF 0x001400E8 /* BB add struct */
 #define FSCTL_LMR_SET_LINK_TRACK_INF 0x001400EC /* BB add struct */
-#define FSCTL_VALIDATE_NEGOTIATE_INFO 0x00140204 /* BB add struct */
+#define FSCTL_VALIDATE_NEGOTIATE_INFO 0x00140204
 /* Perform server-side data movement */
 #define FSCTL_SRV_COPYCHUNK 0x001440F2
 #define FSCTL_SRV_COPYCHUNK_WRITE 0x001480F2