All of a sudden, my Amazon S3 HTTP requests aren't working. Signature Does Not Match error. Help?

Question

My code was working just fine a couple days ago. Then, all of a sudden, BAM: it stopped working. My PUTs stopped going through, with a SignatureDoesNotMatch error. Help?

require_once 'Crypt/HMAC.php';
require_once 'HTTP/Request.php';


function uploadFile($path_to_file, $store_file_as, $bucket, $debugmode = false) {

        $S3_URL = "http://s3.amazonaws.com/";
        $filePath = $path_to_file;
        $contentType = 'audio/mpeg';
        $keyId = 'THISISMYKEY, YES I DOUBLE CHECKED IT';
        $secretKey = 'THIS IS MYSECRET, YES I DOUBLED CHECKED IT';
        $key = $store_file_as;
        $resource = $bucket . "/" . $key;
        $acl = "public-read";
        $verb = "PUT";
    $httpDate = gmdate("D, d M Y H:i:s T");
    $stringToSign = "PUT\n\naudio/mpeg\n$httpDate\nx-amz-acl:$acl\n/$resource";
    $hasher =& new Crypt_HMAC($secretKey, "sha1");
    $str =  $hasher->hash($stringToSign);
    $raw = '';
    for ($i=0; $i < strlen($str); $i+=2) {
        $raw .= chr(hexdec(substr($str, $i, 2)));
    }
    $signature = base64_encode($raw);

    $req =& new HTTP_Request($S3_URL . $resource);
    $req->setMethod('PUT');
    $req->addHeader("content-type", $contentType);
    $req->addHeader("Date", $httpDate);
    $req->addHeader("x-amz-acl", $acl);
    $req->addHeader("Authorization", "AWS " . $keyId . ":" . $signature);
    $req->setBody(file_get_contents($filePath));  
    $req->sendRequest();
   echo $req->getResponseBody();
   }

Answer 1

Run your signature against the Amazon S3 JavaScript signature tester.

If the two signatures do not match, you know something is wrong with the keys or signing procedure.

If the two match, your keys and signing process are correct and the problem is somewhere else.

The JS tester is invaluable for troubleshooting signature generation problems.