silverstripe-environmentcheck/code/checks/FileWriteableCheck.php

<?php

/**
 * Check that the given file is writable.
 */
class FileWriteableCheck implements EnvironmentCheck
{
    /**
     * @var string
     */
    protected $path;

    /**
     * @param string $path The full path. If a relative path, it will relative to the BASE_PATH.
     */
    public function __construct($path)
    {
        $this->path = $path;
    }

    /**
     * @inheritdoc
     *
     * @return array
     */
    public function check()
    {
        if ($this->path[0] == '/') {
            $filename = $this->path;
        } else {
            $filename = BASE_PATH . DIRECTORY_SEPARATOR . str_replace('/', DIRECTORY_SEPARATOR, $this->path);
        }
        
        if (file_exists($filename)) {
            $isWriteable = is_writeable($filename);
        } else {
            $isWriteable = is_writeable(dirname($filename));
        }
        
        if (!$isWriteable) {
            if (function_exists('posix_getgroups')) {
                $userID = posix_geteuid();
                $user = posix_getpwuid($userID);

                $currentOwnerID = fileowner(file_exists($filename) ? $filename : dirname($filename));
                $currentOwner = posix_getpwuid($currentOwnerID);

                $message = "User '$user[name]' needs to be able to write to this file:\n$filename\n\nThe file is currently owned by '$currentOwner[name]'.  ";

                if ($user['name'] == $currentOwner['name']) {
                    $message .= "We recommend that you make the file writeable.";
                } else {
                    $groups = posix_getgroups();
                    $groupList = array();
                    foreach ($groups as $group) {
                        $groupInfo = posix_getgrgid($group);
                        if (in_array($currentOwner['name'], $groupInfo['members'])) {
                            $groupList[] = $groupInfo['name'];
                        }
                    }
                    if ($groupList) {
                        $message .= "	We recommend that you make the file group-writeable and change the group to one of these groups:\n - ". implode("\n - ", $groupList)
                            . "\n\nFor example:\nchmod g+w $filename\nchgrp " . $groupList[0] . " $filename";
                    } else {
                        $message .= "  There is no user-group that contains both the web-server user and the owner of this file.  Change the ownership of the file, create a new group, or temporarily make the file writeable by everyone during the install process.";
                    }
                }
            } else {
                $message = "The webserver user needs to be able to write to this file:\n$filename";
            }
            
            return array(EnvironmentCheck::ERROR, $message);
        }

        return array(EnvironmentCheck::OK,'');
    }
}