niko
84 lines
3.6 KiB
C#
84 lines
3.6 KiB
C#
using System.Collections.Concurrent;
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namespace Campus_live_rewrite.api.server
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{
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/// <summary>
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/// Short-lived codes for linking a Discord account to a Campus account.
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///
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/// FLOW: the website Settings > Discord tab (SiteController, site-cookie authed) calls
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/// <see cref="Generate"/> for the signed-in account and shows the code; the player runs
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/// `/link <code>` with the Discord bot (BotCommands), which calls <see cref="TryResolve"/>
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/// then <see cref="Consume"/> to bind their Discord id.
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///
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/// This is DELIBERATELY its own single-purpose store, isolated from the admin session gate
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/// (AdminGate) and everything else: redeeming a code ONLY records a Discord<->account link
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/// (PlayerDB.SetDiscordLink) and can never mint an admin session or grant any privilege. That is
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/// the whole point of keeping it separate - linking Discord must never be a path into the admin
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/// panel.
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/// </summary>
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public static class DiscordLinkCodes
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{
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private const int TtlSeconds = 600; // 10 minutes
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// Unambiguous alphabet (no 0/O/1/I) so a 6-char code is easy to read off a screen and type.
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private const string Alphabet = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
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private static readonly ConcurrentDictionary<string, (ulong accountId, long expires)> _codes = new();
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private static readonly Random _rng = new();
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/// <summary>Mint a fresh code for this account (replacing any it already had), valid for 10 min.</summary>
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public static (string code, int ttlSeconds) Generate(ulong accountId)
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{
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Sweep();
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// Drop any outstanding code for this account so only the newest one works.
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foreach (var kv in _codes)
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if (kv.Value.accountId == accountId) _codes.TryRemove(kv.Key, out _);
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string code;
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do
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{
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var chars = new char[6];
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lock (_rng)
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for (int i = 0; i < chars.Length; i++) chars[i] = Alphabet[_rng.Next(Alphabet.Length)];
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code = new string(chars);
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} while (_codes.ContainsKey(code));
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long expires = DateTimeOffset.UtcNow.ToUnixTimeSeconds() + TtlSeconds;
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_codes[code] = (accountId, expires);
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return (code, TtlSeconds);
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}
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/// <summary>Look up (without consuming) the account a live code belongs to. False if unknown/expired.</summary>
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public static bool TryResolve(string? code, out ulong accountId)
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{
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accountId = 0;
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if (string.IsNullOrWhiteSpace(code)) return false;
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code = code.Trim().ToUpperInvariant();
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if (!_codes.TryGetValue(code, out var entry)) return false;
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if (DateTimeOffset.UtcNow.ToUnixTimeSeconds() > entry.expires)
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{
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_codes.TryRemove(code, out _);
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return false;
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}
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accountId = entry.accountId;
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return true;
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}
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/// <summary>Burn a code after a successful link so it can't be reused.</summary>
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public static void Consume(string? code)
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{
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if (string.IsNullOrWhiteSpace(code)) return;
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_codes.TryRemove(code.Trim().ToUpperInvariant(), out _);
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}
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private static long _lastSweep;
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private static void Sweep()
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{
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long now = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
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if (now - Interlocked.Read(ref _lastSweep) < 60) return;
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Interlocked.Exchange(ref _lastSweep, now);
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foreach (var kv in _codes)
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if (now > kv.Value.expires) _codes.TryRemove(kv.Key, out _);
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}
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}
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}
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