如何使用预设策略加密Amazon CloudFront签名以进行私有内容访问

Question

有没有人使用.net实际上制定了如何成功签署一个与CloudFront私有内容一起使用的签名？经过几天的尝试,我只能获得Access Denied.

我一直在使用以下代码的变体,并尝试使用OpenSSL.Net和AWSSDK,但还没有RSA-SHA1的签名方法.

签名(数据)看起来像这样

{"Statement":[{"Resource":"http://xxxx.cloudfront.net/xxxx.jpg","Condition":?{"DateLessThan":?{"AWS:EpochTime":1266922799}}}]}

更新:通过删除上述签名中的单个空格解决所有这些问题.

如果我之前只注意到它!

此方法尝试对签名进行签名以在固定URL中使用.因此,变量包括chand在has中使用的填充,并在签名之前反转byte [],因为OpenSSL就是这样做的.

public string Sign(string data)
{
   using (SHA1Managed SHA1 = new SHA1Managed())
   {
      RSACryptoServiceProvider provider = new RSACryptoServiceProvider();
      RSACryptoServiceProvider.UseMachineKeyStore = false;

      // Amazon PEM converted to XML using OpenSslKey
      provider.FromXmlString("<RSAKeyValue><Modulus>....."); 

      byte[] plainbytes = System.Text.Encoding.UTF8.GetBytes(data);

      byte[] hash = SHA1.ComputeHash(plainbytes);
      //Array.Reverse(sig); // I have see some examples that reverse the hash

      byte[] sig = provider.SignHash(hash, "SHA1");

     return Convert.ToBase64String(sig);
   }
}

通过使用我的CloudBerry Explorer生成CloudFront固定策略URL,我注意到我已经验证了在S3和CloudFront中正确设置了内容.他们是如何做到的呢？

任何想法将不胜感激.谢谢

Answer 1

如果有兴趣的话,这里是完整的代码:

internal class CloudFrontSecurityProvider
{
    private readonly RSACryptoServiceProvider privateKey;
    private readonly string privateKeyId;
    private readonly SHA1Managed sha1 = new SHA1Managed();

    public CloudFrontSecurityProvider(string privateKeyId, string privateKey)
    {
        this.privateKey = new RSACryptoServiceProvider();
        RSACryptoServiceProvider.UseMachineKeyStore = false;

        this.privateKey.FromXmlString( privateKey );
        this.privateKeyId = privateKeyId;
    }
    private static int GetUnixTime(DateTime time)
    {
        DateTime referenceTime = new DateTime(1970, 1,1);
        return (int) (time - referenceTime).TotalSeconds;

    }

    public string GetCannedUrl(string url, DateTime expiration)
    {

        string expirationEpoch = GetUnixTime( expiration ).ToString();

        string policy =
            @"{""Statement"":[{""Resource"":""<url>"",""Condition"":{""DateLessThan"":{""AWS:EpochTime"":<expiration>}}}]}".
                Replace( "<url>", url ).
                Replace( "<expiration>", expirationEpoch );


        string signature = GetUrlSafeString( Sign( policy ) );

        return url + string.Format("?Expires={0}&Signature={1}&Key-Pair-Id={2}", expirationEpoch, signature, this.privateKeyId);
    }

    private static string GetUrlSafeString(byte[] data)
    {
        return Convert.ToBase64String( data ).Replace( '+', '-' ).Replace( '=', '_' ).Replace( '/', '~' );
    }

    private byte[] Sign(string data)
    {
            byte[] plainbytes = Encoding.UTF8.GetBytes(data);

            byte[] hash = sha1.ComputeHash(plainbytes);

            return this.privateKey.SignHash(hash, "SHA1");
    }

}