Add steam ticket parser

src/Prospect.Server.Api/Controllers/ClientController.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using Microsoft.AspNetCore.Mvc;
 using Prospect.Server.Api.Models.Client;
 using Prospect.Server.Api.Models.Client.Data;
+using Prospect.Server.Steam;
 
 namespace Prospect.Server.Api.Controllers
 {
@@ -22,6 +23,9 @@ namespace Prospect.Server.Api.Controllers
             var publisherId = "850902E5B40508ED";
             
             if (!string.IsNullOrEmpty(request.SteamTicket))
+            {
+                var ticket = AppTicket.Parse(request.SteamTicket);
+                if (ticket.IsValid && ticket.HasValidSignature)
                 {
                     return Ok(new ClientResponse<FServerLoginResult>
                     {
@@ -72,6 +76,7 @@ namespace Prospect.Server.Api.Controllers
                         }
                     });
                 }
+            }
             
             return BadRequest(new ClientResponse
             {

src/Prospect.Server.Api/Prospect.Server.Api.csproj

@@ -8,4 +8,8 @@
       <PackageReference Include="Serilog.AspNetCore" Version="4.1.0" />
     </ItemGroup>
 
+    <ItemGroup>
+      <ProjectReference Include="..\Prospect.Server.Steam\Prospect.Server.Steam.csproj" />
+    </ItemGroup>
+
 </Project>

src/Prospect.Server.Steam/AppDlc.cs

@@ -0,0 +1,11 @@
+using System.Collections.Generic;
+
+namespace Prospect.Server.Steam
+{
+    public class AppDlc
+    {
+        public uint AppId { get; set; }
+        
+        public List<uint> Licenses { get; set; }
+    }
+}

src/Prospect.Server.Steam/AppTicket.cs

@@ -0,0 +1,167 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Net;
+
+namespace Prospect.Server.Steam
+{
+    public class AppTicket
+    {
+        private AppTicket()
+        {
+            
+        }
+
+        /// <summary>
+        ///     Full appticket, with a GC token and session header.
+        /// </summary>
+        public byte[] AuthTicket { get; set; }
+        
+        public ulong GcToken { get; set; }
+        
+        public DateTimeOffset TokenGenerated { get; set; }
+        
+        private IPAddress SessionExternalIp { get; set; }
+        
+        /// <summary>
+        ///     Time the client has been connected to Steam in ms.
+        /// </summary>
+        public uint ClientConnectionTime { get; set; }
+        
+        /// <summary>
+        ///     How many servers the client has connected to.
+        /// </summary>
+        public uint ClientConnectionCount { get; set; }
+        
+        public uint Version { get; set; }
+        
+        public ulong SteamId { get; set; }
+        
+        public uint AppId { get; set; }
+        
+        public IPAddress OwnershipTicketExternalIp { get; set; }
+        
+        public IPAddress OwnershipTicketInternalIp { get; set; }
+        
+        public uint OwnershipFlags { get; set; }
+        
+        public DateTimeOffset OwnershipTicketGenerated { get; set; }
+        
+        public DateTimeOffset OwnershipTicketExpires { get; set; }
+        
+        public List<uint> Licenses { get; set; }
+        
+        public List<AppDlc> Dlc { get; set; }
+
+        public byte[] Signature { get; set; }
+        
+        public bool IsExpired { get; set; }
+        
+        public bool HasValidSignature { get; set; }
+        
+        public bool IsValid { get; set; }
+        
+        public static AppTicket Parse(string ticketHex)
+        {
+            var result = new AppTicket();
+            var ticketBytes = Convert.FromHexString(ticketHex);
+
+            using (var stream = new MemoryStream(ticketBytes))
+            using (var ticketReader = new BinaryReader(stream))
+            {
+                // AuthTicket
+                var initialLength = ticketReader.ReadUInt32();
+                if (initialLength == 20)
+                {
+                    result.AuthTicket = ticketBytes.AsSpan(0, 52).ToArray();
+                    result.GcToken = ticketReader.ReadUInt64();
+
+                    ticketReader.BaseStream.Position += 8;
+
+                    result.TokenGenerated = DateTimeOffset.FromUnixTimeSeconds(ticketReader.ReadUInt32());
+
+                    if (ticketReader.ReadUInt32() != 24)
+                    {
+                        return null;
+                    }
+
+                    ticketReader.BaseStream.Position += 8;
+                    
+                    result.SessionExternalIp = new IPAddress(BitConverter.GetBytes(ticketReader.ReadUInt32()));
+                    
+                    ticketReader.BaseStream.Position += 4;
+
+                    result.ClientConnectionTime = ticketReader.ReadUInt32();
+                    result.ClientConnectionCount = ticketReader.ReadUInt32();
+
+                    if (ticketReader.ReadUInt32() + ticketReader.BaseStream.Position != ticketReader.BaseStream.Length)
+                    {
+                        return null;
+                    }
+                }
+                else
+                {
+                    ticketReader.BaseStream.Position -= 4;
+                }
+                
+                // Ownership ticket
+                var ownershipTicketOffset = ticketReader.BaseStream.Position;
+                var ownershipTicketLength = ticketReader.ReadUInt32();
+                if (ownershipTicketOffset + ownershipTicketLength != ticketReader.BaseStream.Length &&
+                    ownershipTicketOffset + ownershipTicketLength + 128 != ticketReader.BaseStream.Length)
+                {
+                    return null;
+                }
+
+                result.Version = ticketReader.ReadUInt32();
+                result.SteamId = ticketReader.ReadUInt64();
+                result.AppId = ticketReader.ReadUInt32();
+                result.OwnershipTicketExternalIp = new IPAddress(BitConverter.GetBytes(ticketReader.ReadUInt32()));
+                result.OwnershipTicketInternalIp = new IPAddress(BitConverter.GetBytes(ticketReader.ReadUInt32()));
+                result.OwnershipFlags = ticketReader.ReadUInt32();
+                result.OwnershipTicketGenerated  = DateTimeOffset.FromUnixTimeSeconds(ticketReader.ReadUInt32());
+                result.OwnershipTicketExpires  = DateTimeOffset.FromUnixTimeSeconds(ticketReader.ReadUInt32());
+                result.Licenses = new List<uint>();
+
+                var licenseCount = ticketReader.ReadUInt16();
+                for (var i = 0; i < licenseCount; i++)
+                {
+                    result.Licenses.Add(ticketReader.ReadUInt32());
+                }
+
+                result.Dlc = new List<AppDlc>();
+                
+                var dlcCount = ticketReader.ReadUInt16();
+                for (var i = 0; i < dlcCount; i++)
+                {
+                    var dlc = new AppDlc();
+
+                    dlc.AppId = ticketReader.ReadUInt32();
+                    dlc.Licenses = new List<uint>();
+
+                    var dlcLicenseCount = ticketReader.ReadUInt16();
+                    for (var j = 0; j < dlcLicenseCount; j++)
+                    {
+                        dlc.Licenses.Add(ticketReader.ReadUInt32());
+                    }
+                    
+                    result.Dlc.Add(dlc);
+                }
+
+                ticketReader.ReadUInt16();
+
+                if (ticketReader.BaseStream.Position + 128 == ticketReader.BaseStream.Length)
+                {
+                    result.Signature = ticketBytes.AsSpan((int)ticketReader.BaseStream.Position, 128).ToArray();
+                }
+
+                var date = DateTimeOffset.UtcNow;
+                result.IsExpired = result.OwnershipTicketExpires < date;
+                result.HasValidSignature = result.Signature != null && SteamCrypto.VerifySignature(ticketBytes.AsSpan((int)ownershipTicketOffset, (int)ownershipTicketLength).ToArray(), result.Signature);
+                result.IsValid = !result.IsExpired && (result.Signature == null || result.HasValidSignature);
+            }
+            
+            return result;
+        }
+    }
+}

src/Prospect.Server.Steam/Prospect.Server.Steam.csproj

@@ -0,0 +1,7 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net5.0</TargetFramework>
+    </PropertyGroup>
+
+</Project>

src/Prospect.Server.Steam/SteamCrypto.cs

@@ -0,0 +1,33 @@
+using System.Security.Cryptography;
+
+namespace Prospect.Server.Steam
+{
+    internal static class SteamCrypto
+    {
+        private const string SystemCertificate = "-----BEGIN PUBLIC KEY-----\n" +
+                                                 "MIGdMA0GCSqGSIb3DQEBAQUAA4GLADCBhwKBgQDf7BrWLBBmLBc1OhSwfFkRf53T\n" +
+                                                 "2Ct64+AVzRkeRuh7h3SiGEYxqQMUeYKO6UWiSRKpI2hzic9pobFhRr3Bvr/WARvY\n" +
+                                                 "gdTckPv+T1JzZsuVcNfFjrocejN1oWI0Rrtgt4Bo+hOneoo3S57G9F1fOpn5nsQ6\n" +
+                                                 "6WOiu4gZKODnFMBCiQIBEQ==\n" +
+                                                 "-----END PUBLIC KEY-----" ;
+        
+        public static bool VerifySignature(byte[] data, byte[] signature)
+        {
+            var rsa = new RSACryptoServiceProvider();
+            var hash = new SHA1Managed();
+            
+            rsa.ImportFromPem(SystemCertificate);
+            
+            var dataOk = rsa.VerifyData(data, CryptoConfig.MapNameToOID("SHA1")!, signature);
+            if (!dataOk)
+            {
+                return false;
+            }
+            
+            var dataHashed = hash.ComputeHash(data);
+            var dataVerified = rsa.VerifyHash(dataHashed, CryptoConfig.MapNameToOID("SHA1")!, signature);
+
+            return dataVerified;
+        }
+    }
+}

src/Prospect.sln

@@ -9,6 +9,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Prospect.Launcher", "Prospe
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Prospect.Server.Api", "Prospect.Server.Api\Prospect.Server.Api.csproj", "{A539B020-8BEC-497F-9176-DC2665D927A1}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Prospect.Server.Steam", "Prospect.Server.Steam\Prospect.Server.Steam.csproj", "{CF1CFAE8-B0B3-401A-9706-35AF54249E67}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|x64 = Debug|x64
@@ -39,6 +41,14 @@ Global
 		{A539B020-8BEC-497F-9176-DC2665D927A1}.Release|x64.Build.0 = Release|Any CPU
 		{A539B020-8BEC-497F-9176-DC2665D927A1}.Release|x86.ActiveCfg = Release|Any CPU
 		{A539B020-8BEC-497F-9176-DC2665D927A1}.Release|x86.Build.0 = Release|Any CPU
+		{CF1CFAE8-B0B3-401A-9706-35AF54249E67}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{CF1CFAE8-B0B3-401A-9706-35AF54249E67}.Debug|x64.Build.0 = Debug|Any CPU
+		{CF1CFAE8-B0B3-401A-9706-35AF54249E67}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{CF1CFAE8-B0B3-401A-9706-35AF54249E67}.Debug|x86.Build.0 = Debug|Any CPU
+		{CF1CFAE8-B0B3-401A-9706-35AF54249E67}.Release|x64.ActiveCfg = Release|Any CPU
+		{CF1CFAE8-B0B3-401A-9706-35AF54249E67}.Release|x64.Build.0 = Release|Any CPU
+		{CF1CFAE8-B0B3-401A-9706-35AF54249E67}.Release|x86.ActiveCfg = Release|Any CPU
+		{CF1CFAE8-B0B3-401A-9706-35AF54249E67}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE