AWS S3 Get signed URL

gistfile1.txt

<?php

if ( ! function_exists( 'el_crypto_hmacSHA1' ) ) {
	/**
	 * Calculate the HMAC SHA1 hash of a string.
	 *
	 * @param string $key The key to hash against
	 * @param string $data The data to hash
	 * @param int $blockSize Optional blocksize
	 * @return string HMAC SHA1
	 */
	function el_crypto_hmacSHA1( $key, $data, $blockSize = 64 )
	{
		if ( strlen( $key ) > $blockSize ) {
			$key = pack( 'H*', sha1( $key ) );
		}
		$key = str_pad( $key, $blockSize, chr( 0x00 ) );
		$ipad = str_repeat( chr( 0x36 ), $blockSize );
		$opad = str_repeat( chr( 0x5c ), $blockSize );
		$hmac = pack( 'H*', sha1( ( $key ^ $opad ) . pack( 'H*', sha1( ( $key ^ $ipad ) . $data ) ) ) );
		return base64_encode( $hmac );
	}
}


/**
 * Retrieve the download URL for the specified archive
 * @param string $fileName The name of the file to retrieve from S3. Must have the file extension!
 * @param bool $signUrl Whether or not to sign the download url. Defaults to false
 * @return string
 */
function aws3_getDownloadUrl( $fileName, $signUrl = false )
{
	$fileName = strtolower($fileName);
	return ( $signUrl ? aws3_getSignedUrl( $fileName ) : 'http://' . AWS3_BUCKET . '.s3.amazonaws.com/' . $fileName );
}

/**
 * Create signed URLs to your protected Amazon S3 files.
 *
 * @param string $fileName The name of the file. File extension must be provided!
 * @param array $customParams Key value pairs of custom parameters
 *
 * @return string Temporary signed Amazon S3 URL
 * @see http://awsdocs.s3.amazonaws.com/S3/20060301/s3-dg-20060301.pdf
 */
function aws3_getSignedUrl( $fileName, $customParams = array() )
{
	$archiveFileName = strtolower($fileName);
	# Calculate the expire time.
	$expires = time() + ( AWS3_EXPIRE_URL_TIME * 60 );
	# Create the object path for use in the signature.
	$objectPathForSignature = '/' . AWS3_BUCKET . '/' . $archiveFileName;
	# Create the S3 friendly string to sign.
	$stringToSign = implode( "\n", $pieces = array( 'GET', null, null, $expires, $objectPathForSignature ) );
	# Create the URL friendly string to use.
	$url = 'http://' . AWS3_BUCKET . '.s3.amazonaws.com/' . $fileName;
	# Custom parameters.
	$appendCharacter = '?'; // Default append character.
	# Loop through the custom query parameters (if any) and append them to the string-to-sign, and to the URL strings.
	if ( ! empty( $customParams ) ) {
		foreach ( $customParams as $paramKey => $paramValue ) {
			$stringToSign .= $appendCharacter . $paramKey . '=' . $paramValue;
			$url .= $appendCharacter . $paramKey . '=' . str_replace( array( '%2F', '%2B' ), array( '/', '+' ), rawurlencode( ltrim( $paramValue, '/' ) ) );
			$appendCharacter = '&';
		}
	}
	# Hash the string-to-sign to create the signature.
	$signature = el_crypto_hmacSHA1( AWS3_SECRET_KEY, $stringToSign );
	# Append generated AWS parameters to the URL.
	$queries = http_build_query( $pieces = array( 'AWSAccessKeyId' => AWS3_ACCESS_KEY, 'Expires' => $expires, 'Signature' => $signature, ) );
	$url .= $appendCharacter . $queries;
	return $url;
}