perf(backend): cache additional regex patterns (#89)

* perf(backend): cache regex patterns for better performance

- TransmissionBase: add static VersionRegex, share with Transmission
- SearchCriteriaBase: cache RepeatingPlusRegex
- SearchMovieComparer: cache QueryYearRegex
- XbmcMetadata: cache WatchedRegex

Avoids regex compilation on each method call.

Partially addresses #36

* fix(security): add regex timeout to prevent ReDoS vulnerabilities

All cached regex patterns now include TimeSpan.FromSeconds(1) timeout
to prevent potential denial of service from malicious input patterns.

---------

Co-authored-by: admin <admin@ardentleatherworks.com>

src/NzbDrone.Core/Download/Clients/Transmission/Transmission.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text.RegularExpressions;
 using FluentValidation.Results;
 using NLog;
 using NzbDrone.Common.Disk;
@@ -78,7 +77,7 @@ protected override ValidationFailure ValidateVersion()
 
             _logger.Debug("Transmission version information: {0}", versionString);
 
-            var versionResult = Regex.Match(versionString, @"(?<!\(|(\d|\.)+)(\d|\.)+(?!\)|(\d|\.)+)").Value;
+            var versionResult = VersionRegex.Match(versionString).Value;
             var version = Version.Parse(versionResult);
 
             if (version < new Version(2, 40))

src/NzbDrone.Core/Download/Clients/Transmission/TransmissionBase.cs

@@ -19,6 +19,8 @@ namespace NzbDrone.Core.Download.Clients.Transmission
 {
     public abstract class TransmissionBase : TorrentClientBase<TransmissionSettings>
     {
+        protected static readonly Regex VersionRegex = new Regex(@"(?<!\(|(\d|\.)+)(\d|\.)+(?!\)|(\d|\.)+)", RegexOptions.Compiled, TimeSpan.FromSeconds(1));
+
         public abstract bool SupportsLabels { get; }
 
         protected readonly ITransmissionProxy _proxy;
@@ -331,7 +333,7 @@ protected bool HasClientVersion(int major, int minor)
         {
             var rawVersion = _proxy.GetClientVersion(Settings);
 
-            var versionResult = Regex.Match(rawVersion, @"(?<!\(|(\d|\.)+)(\d|\.)+(?!\)|(\d|\.)+)").Value;
+            var versionResult = VersionRegex.Match(rawVersion).Value;
             var clientVersion = Version.Parse(versionResult);
 
             return clientVersion >= new Version(major, minor);

src/NzbDrone.Core/Extras/Metadata/Consumers/Xbmc/XbmcMetadata.cs

@@ -51,6 +51,7 @@ public XbmcMetadata(IDetectXbmcNfo detectNfo,
 
         private static readonly Regex MovieImagesRegex = new Regex(@"^(?<type>poster|banner|fanart|clearart|discart|keyart|landscape|logo|backdrop|clearlogo)\.(?:png|jpe?g)", RegexOptions.Compiled | RegexOptions.IgnoreCase);
         private static readonly Regex MovieFileImageRegex = new Regex(@"(?<type>-thumb|-poster|-banner|-fanart|-clearart|-discart|-keyart|-landscape|-logo|-backdrop|-clearlogo)\.(?:png|jpe?g)", RegexOptions.Compiled | RegexOptions.IgnoreCase);
+        private static readonly Regex WatchedRegex = new Regex("<watched>true</watched>", RegexOptions.Compiled, TimeSpan.FromSeconds(1));
 
         public override string Name => "Kodi (XBMC) / Emby";
 
@@ -489,7 +490,7 @@ private bool GetExistingWatchedStatus(Movie movie, string movieFilePath)
 
             var fileContent = _diskProvider.ReadAllText(fullPath);
 
-            return Regex.IsMatch(fileContent, "<watched>true</watched>");
+            return WatchedRegex.IsMatch(fileContent);
         }
     }
 }

src/NzbDrone.Core/IndexerSearch/Definitions/SearchCriteriaBase.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text.RegularExpressions;
@@ -12,6 +13,7 @@ public abstract class SearchCriteriaBase
         private static readonly Regex SpecialCharacter = new Regex(@"['.\u0060\u00B4\u2018\u2019]", RegexOptions.IgnoreCase | RegexOptions.Compiled);
         private static readonly Regex NonWord = new Regex(@"[\W]", RegexOptions.IgnoreCase | RegexOptions.Compiled);
         private static readonly Regex BeginningThe = new Regex(@"^the\s", RegexOptions.IgnoreCase | RegexOptions.Compiled);
+        private static readonly Regex RepeatingPlusRegex = new Regex(@"\+{2,}", RegexOptions.Compiled, TimeSpan.FromSeconds(1));
 
         public Movie Movie { get; set; }
         public List<string> SceneTitles { get; set; }
@@ -32,7 +34,7 @@ public static string GetCleanSceneTitle(string title)
             cleanTitle = NonWord.Replace(cleanTitle, "+");
 
             // remove any repeating +s
-            cleanTitle = Regex.Replace(cleanTitle, @"\+{2,}", "+");
+            cleanTitle = RepeatingPlusRegex.Replace(cleanTitle, "+");
             cleanTitle = cleanTitle.RemoveAccent();
             return cleanTitle.Trim('+', ' ');
         }

src/NzbDrone.Core/MetadataSource/SearchMovieComparer.cs

@@ -11,6 +11,7 @@ public class SearchMovieComparer : IComparer<Movie>
         private static readonly Regex RegexCleanPunctuation = new Regex("[-._:]", RegexOptions.Compiled);
         private static readonly Regex RegexCleanCountryYearPostfix = new Regex(@"(?<=.+)( \([A-Z]{2}\)| \(\d{4}\)| \([A-Z]{2}\) \(\d{4}\))$", RegexOptions.Compiled);
         private static readonly Regex ArticleRegex = new Regex(@"^(a|an|the)\s", RegexOptions.IgnoreCase | RegexOptions.Compiled);
+        private static readonly Regex QueryYearRegex = new Regex(@"^(?<query>.+)\s+(?:\((?<year>\d{4})\)|(?<year>\d{4}))$", RegexOptions.Compiled, TimeSpan.FromSeconds(1));
 
         public string SearchQuery { get; private set; }
 
@@ -21,7 +22,7 @@ public SearchMovieComparer(string searchQuery)
         {
             SearchQuery = searchQuery;
 
-            var match = Regex.Match(SearchQuery, @"^(?<query>.+)\s+(?:\((?<year>\d{4})\)|(?<year>\d{4}))$");
+            var match = QueryYearRegex.Match(SearchQuery);
             if (match.Success)
             {
                 _searchQueryWithoutYear = match.Groups["query"].Value.ToLowerInvariant();