deployment - Where do I store my Azure role settings that are not to be stored as plain text?

Question

Looks like the standard way of storing settings of Azure roles is under <ConfigurationSettings> tag in the .cscfg file. Looks convenient, but the file is not encrypted in any way - it is an XML that is uploaded to the Azure portal as plain text and is stored as plain text and can be edited at any time.

In my application I'll need settings that should not be stored as plain text - like for example a password to my SQL Azure database. I'd rather not have a plaintext XML file with that password. How do I store such role settings?

Answer 1

The typical way to do this on-premises is to use DPAPI on a single machine. Of course, this has problems on a web farm. To work around this, you can share a single key on each machine and encrypt. The easiest way to do this is to use certificate based encryption.

Nothing against the SQL Azure posts referenced by Michael, but that had to be the longest series ever to tell you to use the PKCS12 configuration provider. The only reason to use that provider is that it works in conjuction with the built-in tooling from ASP.NET that can read from appSettings automatically. It doesn't help with ServiceConfiguration that needs to change.

If all you want to do is securely protect a setting (typically in ServiceConfig) and you don't mind writing a utility class to do it, then you can use these two functions with any certificate (with private key) uploaded to Windows Azure. This is exactly how the password for remote access is encrypted in the Service Configuration.

Encrypt:

var passwordBytes = UTF8Encoding.UTF8.GetBytes("p@ssw0rd");
var contentInfo = new ContentInfo(passwordBytes);
var thumb = "F49E41878B6D63A8DD6B3650030C1A06DEBB5E77";

var env = new EnvelopedCms(contentInfo);

X509Store store = null;

try
{
    store = new X509Store(StoreName.My, StoreLocation.CurrentUser);

    store.Open(OpenFlags.ReadOnly);
    var cert = store.Certificates.Cast<X509Certificate2>().Where (xc => xc.Thumbprint == thumb).Single();

    env.Encrypt(new CmsRecipient(cert));

    Convert.ToBase64String(env.Encode()).Dump();
}
finally
{
    if (store != null)
        store.Close();
}

Decrypt:

var thumb = "F49E41878B6D63A8DD6B3650030C1A06DEBB5E77";

var cipherText = "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";

X509Store store = null;

try
{
    store = new X509Store(StoreName.My, StoreLocation.CurrentUser);

    store.Open(OpenFlags.ReadOnly);
    var cert = store.Certificates.Cast<X509Certificate2>().Where (xc => xc.Thumbprint == thumb).Single();

    var bytes = Convert.FromBase64String(cipherText);
    var env = new EnvelopedCms();
    env.Decode(bytes);
    env.Decrypt();
    Encoding.UTF8.GetString(env.ContentInfo.Content).Dump();
}
finally
{
    if (store != null)
        store.Close();
}