cifs: Add new mount option -o nounicode to disable SMB1 UNICODE mode

SMB1 protocol supports non-UNICODE (8-bit OEM character set) and
UNICODE (UTF-16) modes.

Linux SMB1 client implements both of them but currently does not allow to
choose non-UNICODE mode when SMB1 server announce UNICODE mode support.

This change adds a new mount option -o nounicode to disable UNICODE mode
and force usage of non-UNICODE (8-bit OEM character set) mode.

This allows to test non-UNICODE implementation of Linux SMB1 client against
any SMB1 server, including modern and recent Windows SMB1 server.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: pali

fs/smb/client/cifsfs.c

@@ -637,6 +637,10 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 					   cifs_sb->ctx->dir_mode);
 	if (cifs_sb->ctx->iocharset)
 		seq_printf(s, ",iocharset=%s", cifs_sb->ctx->iocharset);
+	if (tcon->ses->unicode == 0)
+		seq_puts(s, ",nounicode");
+	else if (tcon->ses->unicode == 1)
+		seq_puts(s, ",unicode");
 	if (tcon->seal)
 		seq_puts(s, ",seal");
 	else if (tcon->ses->server->ignore_signature)

fs/smb/client/cifsglob.h

@@ -653,6 +653,7 @@ struct smb_version_values {
 	unsigned int	cap_unix;
 	unsigned int	cap_nt_find;
 	unsigned int	cap_large_files;
+	unsigned int	cap_unicode;
 	__u16		signing_enabled;
 	__u16		signing_required;
 	size_t		create_lease_size;
@@ -1120,6 +1121,7 @@ struct cifs_ses {
 	bool sign;		/* is signing required? */
 	bool domainAuto:1;
 	bool expired_pwd;  /* track if access denied or expired pwd so can know if need to update */
+	int unicode;
 	unsigned int flags;
 	__u16 session_flags;
 	__u8 smb3signingkey[SMB3_SIGN_KEY_SIZE];

fs/smb/client/cifssmb.c

@@ -437,7 +437,10 @@ CIFSSMBNegotiate(const unsigned int xid,
 		return rc;
 
 	pSMB->hdr.Mid = get_next_mid(server);
-	pSMB->hdr.Flags2 |= (SMBFLG2_UNICODE | SMBFLG2_ERR_STATUS);
+	pSMB->hdr.Flags2 |= SMBFLG2_ERR_STATUS;
+
+	if (ses->unicode != 0)
+		pSMB->hdr.Flags2 |= SMBFLG2_UNICODE;
 
 	if (should_set_ext_sec_flag(ses->sectype)) {
 		cifs_dbg(FYI, "Requesting extended security\n");

fs/smb/client/connect.c

@@ -2351,6 +2351,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 	ses->cred_uid = ctx->cred_uid;
 	ses->linux_uid = ctx->linux_uid;
 
+	ses->unicode = ctx->unicode;
 	ses->sectype = ctx->sectype;
 	ses->sign = ctx->sign;
 
@@ -4123,7 +4124,7 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 		   struct TCP_Server_Info *server,
 		   struct nls_table *nls_info)
 {
-	int rc = -ENOSYS;
+	int rc = 0;
 	struct TCP_Server_Info *pserver = SERVER_IS_CHAN(server) ? server->primary_server : server;
 	struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *)&pserver->dstaddr;
 	struct sockaddr_in *addr = (struct sockaddr_in *)&pserver->dstaddr;
@@ -4175,6 +4176,26 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 		if (!linuxExtEnabled)
 			ses->capabilities &= (~server->vals->cap_unix);
 
+		/*
+		 * Check if the server supports specified encoding mode.
+		 * Zero value in vals->cap_unicode indidcates that chosen
+		 * protocol dialect does not support non-UNICODE mode.
+		 */
+		if (ses->unicode == 1 && server->vals->cap_unicode != 0 &&
+		    !(server->capabilities & server->vals->cap_unicode)) {
+			cifs_dbg(VFS, "Server does not support mounting in UNICODE mode\n");
+			rc = -EOPNOTSUPP;
+		} else if (ses->unicode == 0 && server->vals->cap_unicode == 0) {
+			cifs_dbg(VFS, "Server does not support mounting in non-UNICODE mode\n");
+			rc = -EOPNOTSUPP;
+		} else if (ses->unicode == 0) {
+			/*
+			 * When UNICODE mode was explicitly disabled then
+			 * do not announce client UNICODE capability.
+			 */
+			ses->capabilities &= (~server->vals->cap_unicode);
+		}
+
 		if (ses->auth_key.response) {
 			cifs_dbg(FYI, "Free previous auth_key.response = %p\n",
 				 ses->auth_key.response);
@@ -4187,8 +4208,12 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 	cifs_dbg(FYI, "Security Mode: 0x%x Capabilities: 0x%x TimeAdjust: %d\n",
 		 server->sec_mode, server->capabilities, server->timeAdj);
 
-	if (server->ops->sess_setup)
-		rc = server->ops->sess_setup(xid, ses, server, nls_info);
+	if (!rc) {
+		if (server->ops->sess_setup)
+			rc = server->ops->sess_setup(xid, ses, server, nls_info);
+		else
+			rc = -ENOSYS;
+	}
 
 	if (rc) {
 		cifs_server_dbg(VFS, "Send error in SessSetup = %d\n", rc);
@@ -4258,6 +4283,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 	ctx->seal = master_tcon->seal;
 	ctx->witness = master_tcon->use_witness;
 	ctx->dfs_root_ses = master_tcon->ses->dfs_root_ses;
+	ctx->unicode = master_tcon->ses->unicode;
 
 	rc = cifs_set_vol_auth(ctx, master_tcon->ses);
 	if (rc) {

fs/smb/client/fs_context.c

@@ -134,6 +134,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
 	fsparam_flag("compress", Opt_compress),
 	fsparam_flag("witness", Opt_witness),
 	fsparam_flag_no("nativesocket", Opt_nativesocket),
+	fsparam_flag_no("unicode", Opt_unicode),
 
 	/* Mount options which take uid or gid */
 	fsparam_uid("backupuid", Opt_backupuid),
@@ -963,6 +964,10 @@ static int smb3_verify_reconfigure_ctx(struct fs_context *fc,
 		cifs_errorf(fc, "can not change iocharset during remount\n");
 		return -EINVAL;
 	}
+	if (new_ctx->unicode != old_ctx->unicode) {
+		cifs_errorf(fc, "can not change unicode during remount\n");
+		return -EINVAL;
+	}
 
 	return 0;
 }
@@ -1638,6 +1643,10 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 		ctx->witness = true;
 		pr_warn_once("Witness protocol support is experimental\n");
 		break;
+	case Opt_unicode:
+		ctx->unicode = !result.negated;
+		cifs_dbg(FYI, "unicode set to %d\n", ctx->unicode);
+		break;
 	case Opt_rootfs:
 #ifndef CONFIG_CIFS_ROOT
 		cifs_dbg(VFS, "rootfs support requires CONFIG_CIFS_ROOT config option\n");
@@ -1939,6 +1948,8 @@ int smb3_init_fs_context(struct fs_context *fc)
 	ctx->symlink_type = CIFS_SYMLINK_TYPE_DEFAULT;
 	ctx->nonativesocket = 0;
 
+	ctx->unicode = -1; /* autodetect, but prefer UNICODE mode */
+
 /*
  *	short int override_uid = -1;
  *	short int override_gid = -1;

fs/smb/client/fs_context.h

@@ -135,6 +135,7 @@ enum cifs_param {
 	Opt_witness,
 	Opt_is_upcall_target_mount,
 	Opt_is_upcall_target_application,
+	Opt_unicode,
 
 	/* Mount options which take numeric value */
 	Opt_backupuid,
@@ -306,6 +307,7 @@ struct smb3_fs_context {
 	bool compress; /* enable SMB2 messages (READ/WRITE) de/compression */
 	bool rootfs:1; /* if it's a SMB root file system */
 	bool witness:1; /* use witness protocol */
+	int unicode;
 	char *leaf_fullpath;
 	struct cifs_ses *dfs_root_ses;
 	bool dfs_automount:1; /* set for dfs automount only */

fs/smb/client/sess.c

@@ -501,6 +501,7 @@ cifs_ses_add_channel(struct cifs_ses *ses,
 	ctx->password = ses->password;
 	ctx->sectype = ses->sectype;
 	ctx->sign = ses->sign;
+	ctx->unicode = ses->unicode;
 
 	/* UNC and paths */
 	/* XXX: Use ses->server->hostname? */

fs/smb/client/smb1ops.c

@@ -1170,6 +1170,7 @@ struct smb_version_values smb1_values = {
 	.cap_unix = CAP_UNIX,
 	.cap_nt_find = CAP_NT_SMBS | CAP_NT_FIND,
 	.cap_large_files = CAP_LARGE_FILES,
+	.cap_unicode = CAP_UNICODE,
 	.signing_enabled = SECMODE_SIGN_ENABLED,
 	.signing_required = SECMODE_SIGN_REQUIRED,
 };