From 99c93ec5afe499a5080ab453293a1143fd7ae0e3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Isma=C3=ABl=20Mej=C3=ADa?= <iemejia@apache.org>
Date: Sat, 22 Aug 2026 19:58:30 +0200
Subject: [PATCH] AVRO-4346: [csharp] Validate enum symbols and protocol names
 at parse time

AVRO-4314 added Avro name-grammar validation for record/fixed/enum names,
field names and aliases, and message names, but two parse-time paths were
left unvalidated:

- Enum symbols read from JSON: EnumSchema.NewInstance only checked for
  duplicates and never called ValidateSymbolName (that ran only on the
  programmatic Create() path). An out-of-spec symbol was carried through
  and emitted verbatim as an enum member identifier by the code generator.
- Protocol names: Protocol.Parse never validated the protocol name, which
  is emitted as generated class names.

Validate enum symbols on the JSON parse path (surfacing a SchemaParseException
with the JSON path, consistent with the duplicate-symbol error) and validate
the protocol name via SchemaName.ValidateName (surfacing a ProtocolParseException,
consistent with message-name handling). Adds tests for out-of-spec enum symbols
and protocol names.
---
 lang/csharp/src/apache/main/Protocol/Protocol.cs     |  8 ++++++++
 lang/csharp/src/apache/main/Schema/EnumSchema.cs     |  9 +++++++++
 lang/csharp/src/apache/test/Protocol/ProtocolTest.cs | 11 +++++++++++
 lang/csharp/src/apache/test/Schema/SchemaTests.cs    |  6 ++++++
 4 files changed, 34 insertions(+)

diff --git a/lang/csharp/src/apache/main/Protocol/Protocol.cs b/lang/csharp/src/apache/main/Protocol/Protocol.cs
index 94ae1268a0d..241fe13bb41 100644
--- a/lang/csharp/src/apache/main/Protocol/Protocol.cs
+++ b/lang/csharp/src/apache/main/Protocol/Protocol.cs
@@ -126,6 +126,14 @@ public static Protocol Parse(string jstring)
         private static Protocol Parse(JToken jtok)
         {
             string name = JsonHelper.GetRequiredString(jtok, "protocol");
+            try
+            {
+                SchemaName.ValidateName(name, "protocol");
+            }
+            catch (SchemaParseException e)
+            {
+                throw new ProtocolParseException($"Invalid protocol name: {name}", e);
+            }
             string space = JsonHelper.GetOptionalString(jtok, "namespace");
             string doc = JsonHelper.GetOptionalString(jtok, "doc");
 
diff --git a/lang/csharp/src/apache/main/Schema/EnumSchema.cs b/lang/csharp/src/apache/main/Schema/EnumSchema.cs
index 225780310a6..9bec3cca353 100644
--- a/lang/csharp/src/apache/main/Schema/EnumSchema.cs
+++ b/lang/csharp/src/apache/main/Schema/EnumSchema.cs
@@ -102,6 +102,15 @@ internal static EnumSchema NewInstance(JToken jtok, PropertyMap props, SchemaNam
                 if (symbolMap.ContainsKey(s))
                     throw new SchemaParseException($"Duplicate symbol: {s} at '{jtok.Path}'");
 
+                try
+                {
+                    ValidateSymbolName(s);
+                }
+                catch (AvroException e)
+                {
+                    throw new SchemaParseException($"{e.Message} at '{jtok.Path}'", e);
+                }
+
                 symbolMap[s] = i++;
                 symbols.Add(s);
             }
diff --git a/lang/csharp/src/apache/test/Protocol/ProtocolTest.cs b/lang/csharp/src/apache/test/Protocol/ProtocolTest.cs
index 47f8d98ef00..1e1501a2f69 100644
--- a/lang/csharp/src/apache/test/Protocol/ProtocolTest.cs
+++ b/lang/csharp/src/apache/test/Protocol/ProtocolTest.cs
@@ -198,6 +198,17 @@ public static void TestInvalidMessageName(string str)
             Assert.Throws<ProtocolParseException>(() => Protocol.Parse(str));
         }
 
+        [TestCase(@"{ ""protocol"": ""9bad"", ""types"": [], ""messages"": {} }",
+            TestName = "ProtocolNameLeadingDigit")]
+        [TestCase(@"{ ""protocol"": ""bad name"", ""types"": [], ""messages"": {} }",
+            TestName = "ProtocolNameWithSpace")]
+        [TestCase(@"{ ""protocol"": ""x; class Evil"", ""types"": [], ""messages"": {} }",
+            TestName = "ProtocolNameInjection")]
+        public static void TestInvalidProtocolName(string str)
+        {
+            Assert.Throws<ProtocolParseException>(() => Protocol.Parse(str));
+        }
+
         // Protocols match
         [TestCase(
 @"{
diff --git a/lang/csharp/src/apache/test/Schema/SchemaTests.cs b/lang/csharp/src/apache/test/Schema/SchemaTests.cs
index d2958a82042..e20c2231811 100644
--- a/lang/csharp/src/apache/test/Schema/SchemaTests.cs
+++ b/lang/csharp/src/apache/test/Schema/SchemaTests.cs
@@ -85,6 +85,12 @@ public class SchemaTests
             typeof(SchemaParseException), Description = "No name")]
         [TestCase("{\"type\": \"enum\", \"name\": \"Test\", \"symbols\" : [\"AA\", \"AA\"]}",
             typeof(SchemaParseException), Description = "Duplicate symbol")]
+        [TestCase("{\"type\": \"enum\", \"name\": \"Test\", \"symbols\" : [\"1A\"]}",
+            typeof(SchemaParseException), Description = "Symbol with leading digit")]
+        [TestCase("{\"type\": \"enum\", \"name\": \"Test\", \"symbols\" : [\"A B\"]}",
+            typeof(SchemaParseException), Description = "Symbol with space")]
+        [TestCase("{\"type\": \"enum\", \"name\": \"Test\", \"symbols\" : [\"A-B\"]}",
+            typeof(SchemaParseException), Description = "Symbol with hyphen")]
 
         // Array
         [TestCase("{\"type\": \"array\", \"items\": \"long\"}")]