AWS S3 Signed URL

s3_signed_url.php

<?php
/** @file s3_signed_url.php - provides the s3_signed_url() function to produce time-limited URL's using AWS S3. 
 * Based off; http://dev.wattswork.com/make-signed-urls-for-amazon-s3-with-php/
 */

if ( !function_exists('s3_signed_url' ) ) {

    /**
     * Create signed URLs to your protected Amazon S3 files.
     *
     * @param string $awsAccessKey Your Amazon S3 access key
     * @param string $secretKey Your Amazon S3 secret key
     * @param string $bucket The bucket (mybucket.s3.amazonaws.com)
     * @param string $objectPath The target file path
     * @param int $expires In minutes
     * @return string Temporary signed Amazon S3 URL
     * @see http://awsdocs.s3.amazonaws.com/S3/20060301/s3-dg-20060301.pdf
     */
    function s3_signed_url( $awsAccessKey, $secretKey, $bucket, $objectPath, $expires = 5 ) {
        
        // Calculate the expire time.
        $expires = time() + intval( $expires * 60 );
        
        // Clean and url-encode the object path.
        // $objectPath = str_replace( array( '%2F', '%2B' ), array('/', '+'), rawurlencode( ltrim($objectPath, '/') ) );
        $objectPath = urlencode( trim( $objectPath ) );
        
        // Create the object path for use in the signature.
        $objectPathForSignature = '/'. $bucket .'/'. $objectPath;
        
        // Create the S3 friendly string to sign.
        $stringToSign = implode("\n", $pieces = array('GET', null, null, $expires, $objectPathForSignature));
        
        // Create the base URL to the object
        $url = 'http://' . $bucket . '.s3.amazonaws.com/' . $objectPath;
        
        // Hash the string-to-sign to create the signature.
        $signature = base64_encode( hash_hmac( 'sha1', $stringToSign, $secretKey, true ) );
        
        // Append generated AWS parameters to the URL.
        $queries = http_build_query( $pieces = array(
            'AWSAccessKeyId' => $awsAccessKey,
            'Expires' => $expires,
            'Signature' => $signature,
        ) );
        $url .= '?'. $queries;
        
        // Return the URL.
        return $url;
        
    }

}

/* Copyright (c) 2015, Zachary Scott <zscott.dev@gmail.com>
 *                                                                             
 * Permission is hereby granted, free of charge, to any person obtaining a copy 
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights 
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
 * copies of the Software, and to permit persons to whom the Software is 
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included 
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
 * DEALINGS IN THE SOFTWARE.
 */