5 files changed, 36 insertions, 8 deletions
diff --git a/src/parser/lexer.h b/src/parser/lexer.h
index 83cbcfc53..37c3fe04a 100644
--- a/src/parser/lexer.h
+++ b/src/parser/lexer.h
@@ -25,6 +25,7 @@
 
 #include "support/name.h"
 #include "support/result.h"
+#include "support/string.h"
 
 #ifndef parser_lexer_h
 #define parser_lexer_h
@@ -124,11 +125,11 @@ public:
   std::optional<std::string> takeString();
 
   std::optional<Name> takeName() {
-    // TODO: Validate UTF.
-    if (auto str = takeString()) {
-      return Name(*str);
+    auto str = takeString();
+    if (!str || !String::isUTF8(*str)) {
+      return std::nullopt;
     }
-    return std::nullopt;
+    return Name(*str);
   }
 
   bool takeSExprStart(std::string_view expected) {
diff --git a/src/support/string.cpp b/src/support/string.cpp
index 31d0e9170..01fe4e522 100644
--- a/src/support/string.cpp
+++ b/src/support/string.cpp
@@ -195,9 +195,21 @@ std::optional<uint32_t> takeWTF8CodePoint(std::string_view& str) {
   }
 
   str = str.substr(1 + trailingBytes);
+
   if (!valid) {
     return std::nullopt;
   }
+
+  size_t expectedTrailing = u < 0x80       ? 0
+                            : u < 0x800    ? 1
+                            : u < 0x10000  ? 2
+                            : u < 0x110000 ? 3
+                                           : -1;
+  if (trailingBytes != expectedTrailing) {
+    // Overlong encoding or overlarge code point.
+    return std::nullopt;
+  }
+
   return u;
 }
 
@@ -404,4 +416,14 @@ std::ostream& printEscapedJSON(std::ostream& os, std::string_view str) {
   return os << '"';
 }
 
+bool isUTF8(std::string_view str) {
+  while (str.size()) {
+    auto u = takeWTF8CodePoint(str);
+    if (!u || (0xD800 <= *u && *u < 0xE000)) {
+      return false;
+    }
+  }
+  return true;
+}
+
 } // namespace wasm::String
diff --git a/src/support/string.h b/src/support/string.h
index af120ab4e..24eb570c2 100644
--- a/src/support/string.h
+++ b/src/support/string.h
@@ -99,6 +99,9 @@ bool convertWTF16ToWTF8(std::ostream& os, std::string_view str);
 // unit. Returns `true` if the input was valid UTF-16.
 bool convertUTF16ToUTF8(std::ostream& os, std::string_view str);
 
+// Whether the string is valid UTF-8.
+bool isUTF8(std::string_view str);
+
 } // namespace wasm::String
 
 #endif // wasm_support_string_h
diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index 46d81064e..9ce9bf181 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -1505,7 +1505,7 @@ public:
   HeapType getIndexedHeapType();
 
   Type getConcreteType();
-  Name getInlineString();
+  Name getInlineString(bool requireValid = true);
   void verifyInt8(int8_t x);
   void verifyInt16(int16_t x);
   void verifyInt32(int32_t x);
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index cd1ca7dfd..dc97dbbc3 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -2201,11 +2201,13 @@ Type WasmBinaryReader::getConcreteType() {
   return type;
 }
 
-Name WasmBinaryReader::getInlineString() {
+Name WasmBinaryReader::getInlineString(bool requireValid) {
   BYN_TRACE("<==\n");
   auto len = getU32LEB();
   auto data = getByteView(len);
-
+  if (requireValid && !String::isUTF8(data)) {
+    throwError("invalid UTF-8 string");
+  }
   BYN_TRACE("getInlineString: " << data << " ==>\n");
   return Name(data);
 }
@@ -3027,7 +3029,7 @@ void WasmBinaryReader::readStrings() {
   }
   size_t num = getU32LEB();
   for (size_t i = 0; i < num; i++) {
-    auto string = getInlineString();
+    auto string = getInlineString(false);
     // Re-encode from WTF-8 to WTF-16.
     std::stringstream wtf16;
     if (!String::convertWTF8ToWTF16(wtf16, string.str)) {