Improve domain name parsing and comparison

SmartHomeOS · Jul 18, 2024 · 7f1c237 · 7f1c237
1 parent e512e35
commit 7f1c237
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Showing 9 changed files with 46 additions and 12 deletions.
diff --git a/TinyDNS/Cache/ResolverCache.cs b/TinyDNS/Cache/ResolverCache.cs
@@ -15,7 +15,7 @@ public void Store(IEnumerable<ResourceRecord> records)
 
         public void Store(ResourceRecord record)
         {
-            HashSet<ResourceRecord> recordSet = cache.GetOrAdd(record.Name, new HashSet<ResourceRecord>());
+            HashSet<ResourceRecord> recordSet = cache.GetOrAdd(record.Name.ToLowerInvariant(), new HashSet<ResourceRecord>());
             lock (recordSet)
             {
                 DateTime now = DateTime.Now;
@@ -26,7 +26,7 @@ public void Store(ResourceRecord record)
 
         public ResourceRecord[]? Search(QuestionRecord question)
         {
-            if (cache.TryGetValue(string.Join('.', question.Name), out HashSet<ResourceRecord>? recordSet))
+            if (cache.TryGetValue(string.Join('.', question.Name).ToLowerInvariant(), out HashSet<ResourceRecord>? recordSet))
             {
                 lock (recordSet)
                 {

diff --git a/TinyDNS/DNSResolver.cs b/TinyDNS/DNSResolver.cs
@@ -203,7 +203,7 @@ public async Task<List<IPAddress>> ResolveHostV6(string hostname)
                         }
                         foreach (ResourceRecord additional in response.Additionals)
                         {
-                            if (question.Name.SequenceEqual(additional.Labels) && additional.Type == question.Type)
+                            if (question.Name.SequenceEqual(additional.Labels, new DomainEqualityComparer()) && additional.Type == question.Type)
                                 return response;
                         }
 

diff --git a/TinyDNS/DomainEqualityComparer.cs b/TinyDNS/DomainEqualityComparer.cs
@@ -0,0 +1,12 @@
+namespace TinyDNS
+{
+    public class DomainEqualityComparer : EqualityComparer<String>
+    {
+        public override bool Equals(string? d1, string? d2)
+        {
+           return string.Equals(d1, d2, StringComparison.OrdinalIgnoreCase);
+        }
+
+        public override int GetHashCode(string box) => box.GetHashCode();
+    }
+}
diff --git a/TinyDNS/DomainParser.cs b/TinyDNS/DomainParser.cs
@@ -10,6 +10,7 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+using System.Globalization;
 using System.Text;
 
 namespace TinyDNS
@@ -80,10 +81,31 @@ public static void Write(List<string> labels, Span<byte> buffer, ref int pos)
             buffer[pos++] = ROOT;
         }
 
-        internal static List<string> Parse(string domain)
+        public static List<string> Parse(string domain)
         {
-            //TODO - Handle escaped chars
-            return domain.Split('.', StringSplitOptions.TrimEntries).ToList();
+            List<string> labels = new List<string>();
+            StringBuilder label = new StringBuilder();
+            for (int i = 0; i < domain.Length; i++)
+            {
+                if (domain[i] == '\\')
+                {
+                    //Escaped char follows
+                    if (char.IsAsciiHexDigit(domain[++i]))
+                        label.Append((char)int.Parse(domain.AsSpan().Slice(i++, 2), NumberStyles.HexNumber)); //2 digit char code
+                    else
+                        label.Append(domain[i]); //single character
+                }
+                else if (domain[i] == '.')
+                {
+                    labels.Add(label.ToString());
+                    label.Clear();
+                }
+                else
+                    label.Append(domain[i]);
+            }
+            if (label.Length > 0)
+                labels.Add(label.ToString());
+            return labels;
         }
     }
 }
diff --git a/TinyDNS/Records/CNameRecord.cs b/TinyDNS/Records/CNameRecord.cs
@@ -27,7 +27,7 @@ internal CNameRecord(ResourceRecordHeader header, Span<byte> buffer, ref int pos
 
         public CNameRecord(string cname, List<string> labels, DNSClass @class, uint ttl) : base(labels, DNSRecordType.CNAME, @class, ttl)
         {
-            CNameLabels = new List<string>(cname.Split('.'));
+            CNameLabels = DomainParser.Parse(cname);
         }
 
         public CNameRecord(ResourceRecordHeader header, string rdata) : base(header)

diff --git a/TinyDNS/Records/NSRecord.cs b/TinyDNS/Records/NSRecord.cs
@@ -25,9 +25,9 @@ internal NSRecord(ResourceRecordHeader header, Span<byte> buffer, ref int pos) :
             NSDomainLabels = DomainParser.Read(buffer, ref pos);
         }
 
-        public NSRecord(string cname, List<string> labels, DNSClass @class, uint ttl) : base(labels, DNSRecordType.NS, @class, ttl)
+        public NSRecord(string ns, List<string> labels, DNSClass @class, uint ttl) : base(labels, DNSRecordType.NS, @class, ttl)
         {
-            NSDomainLabels = new List<string>(cname.Split('.'));
+            NSDomainLabels = DomainParser.Parse(ns);
         }
 
         public NSRecord(ResourceRecordHeader header, string rdata) : base(header)

diff --git a/TinyDNS/Records/PtrRecord.cs b/TinyDNS/Records/PtrRecord.cs
@@ -27,7 +27,7 @@ internal PtrRecord(ResourceRecordHeader header, Span<byte> buffer, ref int pos)
 
         public PtrRecord(string domain, List<string> labels, DNSClass @class, uint ttl) : base(labels, DNSRecordType.PTR, @class, ttl)
         {
-            DomainLabels = new List<string>(domain.Split('.'));
+            DomainLabels = DomainParser.Parse(domain);
         }
 
         public PtrRecord(ResourceRecordHeader header, string rdata) : base(header)

diff --git a/TinyDNS/Records/QuestionRecord.cs b/TinyDNS/Records/QuestionRecord.cs
@@ -21,7 +21,7 @@ public class QuestionRecord : IEquatable<QuestionRecord>
         public DNSRecordType Type { get; set; }
         public DNSClass Class { get; set; }
         public bool UnicastResponse { get; set; }
-        public QuestionRecord(string domain, DNSRecordType recordType, bool unicastResponse) : this(new List<string>(domain.Split('.')), recordType, unicastResponse) {  }
+        public QuestionRecord(string domain, DNSRecordType recordType, bool unicastResponse) : this(DomainParser.Parse(domain), recordType, unicastResponse) {  }
 
         public QuestionRecord(List<string> domain, DNSRecordType recordType, bool unicastResponse)
         { 

diff --git a/TinyDNS/Records/SRVRecord.cs b/TinyDNS/Records/SRVRecord.cs
@@ -37,7 +37,7 @@ internal SRVRecord(ResourceRecordHeader header, Span<byte> buffer, ref int pos)
 
         public SRVRecord(string service, ushort priority, ushort port, ushort weight, List<string> labels, DNSClass @class, uint ttl) : base(labels, DNSRecordType.SRV, @class, ttl)
         {
-            TargetLabels = new List<string>(service.Split('.'));
+            TargetLabels = DomainParser.Parse(service);
             Priority = priority;
             Port = port;
             Weight = weight;