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using System;
using System.Diagnostics.CodeAnalysis;
using VNLib.Utils.Memory;
using VNLib.Utils.Extensions;
using VNLib.Hashing;
using VNLib.Net.Http;
using VNLib.Plugins.Essentials.Extensions;
using VNLib.Plugins.Essentials.Sessions.Runtime;
using VNLib.Plugins.Essentials.Oauth.Applications;
using VNLib.Plugins.Sessions.Cache.Client;
using static VNLib.Plugins.Essentials.Oauth.OauthSessionExtensions;
namespace VNLib.Plugins.Essentials.Sessions.OAuth
{
/// <summary>
/// Generates secure OAuth2 session tokens and initalizes new OAuth2 sessions
/// </summary>
internal class OAuth2SessionIdProvider : IOauthSessionIdFactory
{
private readonly string SessionIdPrefix;
private readonly int _bufferSize;
private readonly int _tokenSize;
///<inheritdoc/>
public int MaxTokensPerApp { get; }
///<inheritdoc/>
public TimeSpan SessionValidFor { get; }
///<inheritdoc/>
string IOauthSessionIdFactory.TokenType => "Bearer";
public OAuth2SessionIdProvider(string sessionIdPrefix, int maxTokensPerApp, int tokenSize, TimeSpan validFor)
{
SessionIdPrefix = sessionIdPrefix;
MaxTokensPerApp = maxTokensPerApp;
SessionValidFor = validFor;
_tokenSize = tokenSize;
_bufferSize = tokenSize * 2;
}
///<inheritdoc/>
bool ISessionIdFactory.TryGetSessionId(IHttpEvent entity, [NotNullWhen(true)] out string? sessionId)
{
//Get authorization token and make sure its not too large to cause a buffer overflow
if (entity.Server.HasAuthorization(out string? token) && (token.Length + SessionIdPrefix.Length) <= _bufferSize)
{
//Compute session id from token
sessionId = ComputeSessionIdFromToken(token);
return true;
}
else
{
sessionId = null;
}
return false;
}
private string ComputeSessionIdFromToken(string token)
{
//Buffer to copy data to
using UnsafeMemoryHandle<char> buffer = Memory.UnsafeAlloc<char>(_bufferSize, true);
//Writer to accumulate data
ForwardOnlyWriter<char> writer = new(buffer.Span);
//Append session id prefix and token
writer.Append(SessionIdPrefix);
writer.Append(token);
//Compute base64 hash of token and
return ManagedHash.ComputeBase64Hash(writer.AsSpan(), HashAlg.SHA256);
}
///<inheritdoc/>
TokenAndSessionIdResult IOauthSessionIdFactory.GenerateTokensAndId()
{
//Alloc buffer for random data
using UnsafeMemoryHandle<byte> mem = Memory.UnsafeAlloc<byte>(_tokenSize, true);
//Generate token from random cng bytes
RandomHash.GetRandomBytes(mem);
//Token is the raw value
string token = Convert.ToBase64String(mem.Span);
//The session id is the HMAC of the token
string sessionId = ComputeSessionIdFromToken(token);
//Clear buffer
Memory.InitializeBlock(mem.Span);
//Return sessid result
return new(sessionId, token, null);
}
///<inheritdoc/>
void IOauthSessionIdFactory.InitNewSession(RemoteSession session, UserApplication app, IHttpEvent entity)
{
//Store session variables
session[APP_ID_ENTRY] = app.Id;
session[TOKEN_TYPE_ENTRY] = "client_credential,bearer";
session[SCOPES_ENTRY] = app.Permissions;
session.UserID = app.UserId;
}
}
}
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