smbd: add create_conn_struct_tos[_cwd]() helper functions

This makes it more obvious that the returned connection_struct
is only temporary (and allocated on talloc_tos()!)
It will never allow async requests on a long term
tevent context! So we create a short term event context.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

source3/smbd/msdfs.c

@@ -448,6 +448,131 @@ NTSTATUS create_conn_struct_cwd(TALLOC_CTX *ctx,
 	return NT_STATUS_OK;
 }
 
+static int conn_struct_tos_destructor(struct conn_struct_tos *c)
+{
+	if (c->oldcwd_fname != NULL) {
+		vfs_ChDir(c->conn, c->oldcwd_fname);
+		TALLOC_FREE(c->oldcwd_fname);
+	}
+	SMB_VFS_DISCONNECT(c->conn);
+	conn_free(c->conn);
+	return 0;
+}
+
+/********************************************************
+ Fake up a connection struct for the VFS layer, for use in
+ applications (such as the python bindings), that do not want the
+ global working directory changed under them.
+
+ SMB_VFS_CONNECT requires root privileges.
+ This temporary uses become_root() and unbecome_root().
+
+ But further impersonation has to be cone by the caller.
+*********************************************************/
+NTSTATUS create_conn_struct_tos(struct messaging_context *msg,
+				int snum,
+				const char *path,
+				const struct auth_session_info *session_info,
+				struct conn_struct_tos **_c)
+{
+	struct conn_struct_tos *c = NULL;
+	struct tevent_context *ev = NULL;
+	NTSTATUS status;
+
+	*_c = NULL;
+
+	c = talloc_zero(talloc_tos(), struct conn_struct_tos);
+	if (c == NULL) {
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	ev = samba_tevent_context_init(c);
+	if (ev == NULL) {
+		TALLOC_FREE(c);
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	status = create_conn_struct(c,
+				    ev,
+				    msg,
+				    &c->conn,
+				    snum,
+				    path,
+				    session_info);
+	if (!NT_STATUS_IS_OK(status)) {
+		TALLOC_FREE(c);
+		return status;
+	}
+	talloc_steal(c, c->conn);
+
+	talloc_set_destructor(c, conn_struct_tos_destructor);
+
+	*_c = c;
+	return NT_STATUS_OK;
+}
+
+/********************************************************
+ Fake up a connection struct for the VFS layer.
+ Note: this performs a vfs connect and CHANGES CWD !!!! JRA.
+
+ See also the comment for create_conn_struct_tos() above!
+
+ The CWD change is reverted by the destructor of
+ conn_struct_tos when the current talloc_tos() is destroyed.
+*********************************************************/
+NTSTATUS create_conn_struct_tos_cwd(struct messaging_context *msg,
+				    int snum,
+				    const char *path,
+				    const struct auth_session_info *session_info,
+				    struct conn_struct_tos **_c)
+{
+	struct conn_struct_tos *c = NULL;
+	struct smb_filename smb_fname_connectpath = {0};
+	NTSTATUS status;
+
+	*_c = NULL;
+
+	status = create_conn_struct_tos(msg,
+					snum,
+					path,
+					session_info,
+					&c);
+	if (!NT_STATUS_IS_OK(status)) {
+		return status;
+	}
+
+	/*
+	 * Windows seems to insist on doing trans2getdfsreferral() calls on
+	 * the IPC$ share as the anonymous user. If we try to chdir as that
+	 * user we will fail.... WTF ? JRA.
+	 */
+
+	c->oldcwd_fname = vfs_GetWd(c, c->conn);
+	if (c->oldcwd_fname == NULL) {
+		status = map_nt_error_from_unix(errno);
+		DEBUG(3, ("vfs_GetWd failed: %s\n", strerror(errno)));
+		TALLOC_FREE(c);
+		return status;
+	}
+
+	smb_fname_connectpath = (struct smb_filename) {
+		.base_name = c->conn->connectpath
+	};
+
+	if (vfs_ChDir(c->conn, &smb_fname_connectpath) != 0) {
+		status = map_nt_error_from_unix(errno);
+		DBG_NOTICE("Can't ChDir to new conn path %s. "
+			   "Error was %s\n",
+			   c->conn->connectpath, strerror(errno));
+		TALLOC_FREE(c->oldcwd_fname);
+		TALLOC_FREE(c);
+		return status;
+	}
+
+	*_c = c;
+	return NT_STATUS_OK;
+}
+
 static void shuffle_strlist(char **list, int count)
 {
 	int i;

source3/smbd/proto.h

@@ -514,6 +514,22 @@ NTSTATUS create_conn_struct_cwd(TALLOC_CTX *ctx,
 				const char *path,
 				const struct auth_session_info *session_info,
 				struct smb_filename **poldcwd_fname);
+struct connection_struct;
+struct smb_filename;
+struct conn_struct_tos {
+	struct connection_struct *conn;
+	struct smb_filename *oldcwd_fname;
+};
+NTSTATUS create_conn_struct_tos(struct messaging_context *msg,
+				int snum,
+				const char *path,
+				const struct auth_session_info *session_info,
+				struct conn_struct_tos **_c);
+NTSTATUS create_conn_struct_tos_cwd(struct messaging_context *msg,
+				    int snum,
+				    const char *path,
+				    const struct auth_session_info *session_info,
+				    struct conn_struct_tos **_c);
 
 /* The following definitions come from smbd/negprot.c  */