git.stella-ops.org/src/__Libraries/StellaOps.Cryptography/DefaultCryptoProvider.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;

namespace StellaOps.Cryptography;

/// <summary>
/// Default in-process crypto provider exposing password hashing capabilities.
/// </summary>
public sealed class DefaultCryptoProvider : ICryptoProvider, ICryptoProviderDiagnostics
{
    private readonly ConcurrentDictionary<string, IPasswordHasher> passwordHashers;
    private readonly ConcurrentDictionary<string, CryptoSigningKey> signingKeys;
    private static readonly HashSet<string> SupportedSigningAlgorithms = new(StringComparer.OrdinalIgnoreCase)
    {
        SignatureAlgorithms.Es256
    };

    private static readonly HashSet<string> SupportedHashAlgorithms = new(StringComparer.OrdinalIgnoreCase)
    {
        HashAlgorithms.Sha256,
        HashAlgorithms.Sha384,
        HashAlgorithms.Sha512
    };

    public DefaultCryptoProvider()
    {
        passwordHashers = new ConcurrentDictionary<string, IPasswordHasher>(StringComparer.OrdinalIgnoreCase);
        signingKeys = new ConcurrentDictionary<string, CryptoSigningKey>(StringComparer.Ordinal);

        var argon = new Argon2idPasswordHasher();
        var pbkdf2 = new Pbkdf2PasswordHasher();

        passwordHashers.TryAdd(PasswordHashAlgorithm.Argon2id.ToString(), argon);
        passwordHashers.TryAdd(PasswordHashAlgorithms.Argon2id, argon);
        passwordHashers.TryAdd(PasswordHashAlgorithm.Pbkdf2.ToString(), pbkdf2);
        passwordHashers.TryAdd(PasswordHashAlgorithms.Pbkdf2Sha256, pbkdf2);
    }

    public string Name => "default";

    public bool Supports(CryptoCapability capability, string algorithmId)
    {
        if (string.IsNullOrWhiteSpace(algorithmId))
        {
            return false;
        }

        return capability switch
        {
            CryptoCapability.PasswordHashing => passwordHashers.ContainsKey(algorithmId),
            CryptoCapability.Signing or CryptoCapability.Verification => SupportedSigningAlgorithms.Contains(algorithmId),
            CryptoCapability.ContentHashing => SupportedHashAlgorithms.Contains(algorithmId),
            _ => false
        };
    }

    public IPasswordHasher GetPasswordHasher(string algorithmId)
    {
        if (!Supports(CryptoCapability.PasswordHashing, algorithmId))
        {
            throw new InvalidOperationException($"Password hashing algorithm '{algorithmId}' is not supported by provider '{Name}'.");
        }

        return passwordHashers[algorithmId];
    }

    public ICryptoHasher GetHasher(string algorithmId)
    {
        if (!Supports(CryptoCapability.ContentHashing, algorithmId))
        {
            throw new InvalidOperationException($"Hash algorithm '{algorithmId}' is not supported by provider '{Name}'.");
        }

        return new DefaultCryptoHasher(algorithmId);
    }

    public ICryptoSigner GetSigner(string algorithmId, CryptoKeyReference keyReference)
    {
        ArgumentNullException.ThrowIfNull(keyReference);

        if (!Supports(CryptoCapability.Signing, algorithmId))
        {
            throw new InvalidOperationException($"Signing algorithm '{algorithmId}' is not supported by provider '{Name}'.");
        }

        if (!signingKeys.TryGetValue(keyReference.KeyId, out var signingKey))
        {
            throw new KeyNotFoundException($"Signing key '{keyReference.KeyId}' is not registered with provider '{Name}'.");
        }

        if (!string.Equals(signingKey.AlgorithmId, algorithmId, StringComparison.OrdinalIgnoreCase))
        {
            throw new InvalidOperationException(
                $"Signing key '{keyReference.KeyId}' is registered for algorithm '{signingKey.AlgorithmId}', not '{algorithmId}'.");
        }

        return EcdsaSigner.Create(signingKey);
    }

    public ICryptoSigner CreateEphemeralVerifier(string algorithmId, ReadOnlySpan<byte> publicKeyBytes)
    {
        if (!Supports(CryptoCapability.Verification, algorithmId))
        {
            throw new InvalidOperationException($"Verification algorithm '{algorithmId}' is not supported by provider '{Name}'.");
        }

        return EcdsaSigner.CreateVerifierFromPublicKey(algorithmId, publicKeyBytes);
    }

    public void UpsertSigningKey(CryptoSigningKey signingKey)
    {
        ArgumentNullException.ThrowIfNull(signingKey);
        EnsureSigningSupported(signingKey.AlgorithmId);
        if (signingKey.Kind != CryptoSigningKeyKind.Ec)
        {
            throw new InvalidOperationException($"Provider '{Name}' only accepts EC signing keys.");
        }
        ValidateSigningKey(signingKey);

        signingKeys.AddOrUpdate(signingKey.Reference.KeyId, signingKey, (_, _) => signingKey);
    }

    public bool RemoveSigningKey(string keyId)
    {
        if (string.IsNullOrWhiteSpace(keyId))
        {
            return false;
        }

        return signingKeys.TryRemove(keyId, out _);
    }

    public IReadOnlyCollection<CryptoSigningKey> GetSigningKeys()
        => signingKeys.Values.ToArray();

    public IEnumerable<CryptoProviderKeyDescriptor> DescribeKeys()
    {
        foreach (var key in signingKeys.Values)
        {
            var metadata = new Dictionary<string, string?>(StringComparer.OrdinalIgnoreCase)
            {
                ["kind"] = key.Kind.ToString(),
                ["createdAt"] = key.CreatedAt.UtcDateTime.ToString("O"),
                ["providerHint"] = key.Reference.ProviderHint,
                ["provider"] = Name
            };

            if (key.ExpiresAt.HasValue)
            {
                metadata["expiresAt"] = key.ExpiresAt.Value.UtcDateTime.ToString("O");
            }

            foreach (var pair in key.Metadata)
            {
                metadata[$"meta.{pair.Key}"] = pair.Value;
            }

            yield return new CryptoProviderKeyDescriptor(
                Name,
                key.Reference.KeyId,
                key.AlgorithmId,
                metadata);
        }
    }

    private static void EnsureSigningSupported(string algorithmId)
    {
        if (!SupportedSigningAlgorithms.Contains(algorithmId))
        {
            throw new InvalidOperationException($"Signing algorithm '{algorithmId}' is not supported by provider 'default'.");
        }
    }

    private static void ValidateSigningKey(CryptoSigningKey signingKey)
    {
        if (!string.Equals(signingKey.AlgorithmId, SignatureAlgorithms.Es256, StringComparison.OrdinalIgnoreCase))
        {
            throw new InvalidOperationException($"Only ES256 signing keys are currently supported by provider 'default'.");
        }

        var expected = ECCurve.NamedCurves.nistP256;
        var curve = signingKey.PrivateParameters.Curve;
        if (!curve.IsNamed || !string.Equals(curve.Oid.Value, expected.Oid.Value, StringComparison.Ordinal))
        {
            throw new InvalidOperationException("ES256 signing keys must use the NIST P-256 curve.");
        }
    }
}