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validate_file() WP 1.0

Validates a file name and path against an allowed set of rules.

A return value of 1 means the file path contains directory traversal.

A return value of 2 means the file path contains a Windows drive path.

A return value of 3 means the file is not in the allowed files list.

✈ 1 time = 0.000018s = very fast | 50000 times = 0.01s = speed of light PHP 7.1.2, WP 4.7.5

No Hooks.

Return

Int. 0 means nothing is wrong, greater than 0 means something was wrong.

Usage

validate_file( $file, $allowed_files );
$file(string) (required)
File path.
$allowed_files(array)
List of allowed files.
Default: array()

Code of validate_file: wp-includes/functions.php VER 4.9.8

<?php
function validate_file( $file, $allowed_files = array() ) {
	// `../` on its own is not allowed:
	if ( '../' === $file ) {
		return 1;
	}

	// More than one occurence of `../` is not allowed:
	if ( preg_match_all( '#\.\./#', $file, $matches, PREG_SET_ORDER ) && ( count( $matches ) > 1 ) ) {
		return 1;
	}

	// `../` which does not occur at the end of the path is not allowed:
	if ( false !== strpos( $file, '../' ) && '../' !== mb_substr( $file, -3, 3 ) ) {
		return 1;
	}

	// Files not in the allowed file list are not allowed:
	if ( ! empty( $allowed_files ) && ! in_array( $file, $allowed_files ) )
		return 3;

	// Absolute Windows drive paths are not allowed:
	if (':' == substr( $file, 1, 1 ) )
		return 2;

	return 0;
}

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