Help with Signature Verification

[jceddy]

I am running into an issue with a simple C# program testing signature verification with a self-hosted server...I think I have everything set up correctly, but verification fails.

Was wondering whether someone could take a look at my C# code and maybe point me in the direction of what my issue might be?

Here is my test Program.cs:
(KeygenSettings.PublicKeyBase64 is the key from the accounts API - meta.publicKeys.ed25519)

using NSec.Cryptography;
using RestSharp;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;

namespace KeygenSignatureVerification
{
	internal partial class Program
	{
		[GeneratedRegex("signature=\"([^\"]+)\"")]
		private static partial Regex SignatureRegex();

		static void Main(string[] args)
		{
			var publicKeyBase64 = KeygenSettings.PublicKeyBase64;
			var host = KeygenSettings.Host;
			var licenseKey = "E34A96-112639-84ECE3-1725AD-40AB22-V3";
			var licenseId = "69aa8195-1729-43f2-b890-d060edbf9890";
			var request = $"/v1/licenses/{licenseId}/entitlements";

			RestClient client = new(new RestClientOptions($"https://{host}")
			{
				RemoteCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => true
			});
			var restRequest = new RestRequest(request);

			restRequest.AddHeader("Authorization", $"License {licenseKey}");
			restRequest.AddHeader("Accept", "application/vnd.api+json");

			var response = client.Execute(restRequest);

			var responseBody = response.Content ?? string.Empty;
			Console.WriteLine(responseBody);

			if(response.Headers == null)
			{
				Console.WriteLine("Response has no Headers");
				Environment.Exit(1);
			}
			var dateHeaderObject = response.Headers.Where(x => x.Name == "Date").First().Value;
			if(dateHeaderObject == null)
			{
				Console.WriteLine("No Date Header Found");
				Environment.Exit(1);
			}
			var dateHeader = dateHeaderObject.ToString();
			Console.WriteLine(dateHeader);

			var keygenSignatureHeaderObject = response.Headers.Where(x => x.Name == "Keygen-Signature").First().Value;
			if (keygenSignatureHeaderObject == null)
			{
				Console.WriteLine("No Keygen-Signature Header Found");
				Environment.Exit(1);
			}
			var keygenSignatureHeader = keygenSignatureHeaderObject.ToString() ?? string.Empty;
			Console.WriteLine(keygenSignatureHeader);

			var requestTarget = $"get {request}";

			var signature = SignatureRegex().Match(keygenSignatureHeader).Groups[1].Value;
			var signatureBytes = Convert.FromBase64String(signature);

			var digestBytes = SHA256.HashData(Encoding.UTF8.GetBytes(responseBody));
			var encDigest = Convert.ToBase64String(digestBytes);

			var signingData = $"(request target): {requestTarget}\nhost: {host}\ndate: {dateHeader}\ndigest: sha-256={encDigest}";
			var signingDataBytes = Encoding.UTF8.GetBytes(signingData);

			var algorithm = SignatureAlgorithm.Ed25519;

			var publicKeyBytes = Convert.FromHexString(Encoding.UTF8.GetString(Convert.FromBase64String(publicKeyBase64)));
			var publicKey = PublicKey.Import(algorithm, publicKeyBytes, KeyBlobFormat.RawPublicKey);

			var valid = algorithm.Verify(publicKey, signingDataBytes, signatureBytes);

			if(valid)
			{
				Console.WriteLine("data is valid");
			}
			else
			{
				Console.WriteLine("data is invalid");
			}
		}
	}
}

The output of which is:

{"data":[{"id":"3ff1059d-804c-4676-94a0-c65cdece6252","type":"entitlements","attributes":{"name":"Feature #2","code":"FEATURE_2","metadata":{},"created":"2024-06-20T18:30:26.075Z","updated":"2024-06-20T18:30:26.075Z"},"relationships":{"account":{"links":{"related":"/v1/accounts/bb420bd7-5e98-4147-831e-a41b990eeccd"},"data":{"type":"accounts","id":"bb420bd7-5e98-4147-831e-a41b990eeccd"}}},"links":{"self":"/v1/accounts/bb420bd7-5e98-4147-831e-a41b990eeccd/entitlements/3ff1059d-804c-4676-94a0-c65cdece6252"}},{"id":"764fb084-0e97-4ee6-a906-33b556a1c3bb","type":"entitlements","attributes":{"name":"Feature #1","code":"FEATURE_1","metadata":{},"created":"2024-06-20T18:30:18.288Z","updated":"2024-06-20T18:30:18.288Z"},"relationships":{"account":{"links":{"related":"/v1/accounts/bb420bd7-5e98-4147-831e-a41b990eeccd"},"data":{"type":"accounts","id":"bb420bd7-5e98-4147-831e-a41b990eeccd"}}},"links":{"self":"/v1/accounts/bb420bd7-5e98-4147-831e-a41b990eeccd/entitlements/764fb084-0e97-4ee6-a906-33b556a1c3bb"}}]}
Fri, 28 Jun 2024 21:32:32 GMT
keyid="bb420bd7-5e98-4147-831e-a41b990eeccd", algorithm="ed25519", signature="vbe//u4f0hXd0t2RldWexw8OZr3OZs0EOXmbiCQV4L74MB0lP5fMpa0pT/NjhbHatSAJJBK5FFwnbS5Kk/STBQ==", headers="(request-target) host date digest"
data is invalid

[ezekg]

I'm AFK, so I haven't tested it, but the code looks good. Are you sure you have the public key correct? Typically, an Ed25519 public key is hex encoded, not base64 encoded.

[jceddy]

When you call the accounts API the meta.publicKeys.ed25519 field of the response has a base64-encoded string that decodes to a 65-character hex string that is a valid ed25519 key.

I assume this is the correct public key for the process, but not 100% sure.

The system is singleplayer and that is the account associated with the license.

[ezekg]

That should be correct, yeah. You can get the hex public key via this command in the console:

puts Account.sole.ed25519_public_key

Traveling rm but I can try to help further later tonight.

[jceddy]

That would be great. I have a feeling I am missing something simple, but don't know what.

The way the system is set up makes it a real PITA to get at the console, which is why I am grabbing the value from the API, but I might need to do that just so I can verify the public key is correct.

[ezekg]

In your signing data, you have (request target), but it should be (request-target).

[jceddy]

Oh God, thank you! 😂

…

On Sun, Jun 30, 2024, 12:32 PM Zeke Gabrielse ***@***.***> wrote: In your signing data, you have (request target), but it should be (request-target). — Reply to this email directly, view it on GitHub <#146 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAJ5557ZZR5XZ7XPPSACHG3ZKA6MRAVCNFSM6AAAAABKCRM3LSVHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TSMJYGE2DQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>