// Mgmt
// Copyright (C) James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
// Additional permission under GNU GPL version 3 section 7
//
// If you modify this program, or any covered work, by linking or combining it
// with embedded mcl code and modules (and that the embedded mcl code and
// modules which link with this program, contain a copy of their source code in
// the authoritative form) containing parts covered by the terms of any other
// license, the licensors of this program grant you additional permission to
// convey the resulting work. Furthermore, the licensors of this program grant
// the original author, James Shubin, additional permission to update this
// additional permission if he deems it necessary to achieve the goals of this
// additional permission.

package util

import (
	"fmt"
	"strings"

	securefilepath "github.com/cyphar/filepath-securejoin"
)

// SecureJoin joins the two given path components (similar to filepath.Join)
// except that the returned path is guaranteed to be scoped inside the provided
// root path (when evaluated). Any symbolic links in the path are evaluated with
// the given root treated as the root of the filesystem, similar to a chroot.
//
// Note that the guarantees provided by this function only apply if the path
// components in the returned string are not modified (in other words are not
// replaced with symlinks on the filesystem) after this function has returned.
// Such a symlink race is necessarily out-of-scope of SecureJoin.
//
// The root param must be a dir that ends with a slash.
func SecureJoin(root, unsafePath string) (string, error) {
	cleanRoot := strings.TrimSuffix(root, "/") // needed for SecureJoin
	if root == cleanRoot {
		return "", fmt.Errorf("root was not a directory")
	}
	// XXX: pull this dep in tree?
	return securefilepath.SecureJoin(cleanRoot, unsafePath)
}
