From 7442ea2be09fc5d4eebd1c3fa679ff3422f405a7 Mon Sep 17 00:00:00 2001
From: Eugene Blikh <bigbes@gmail.com>
Date: Sat, 16 May 2026 00:15:51 +0300
Subject: [PATCH] wire: reject illegal wire types 6/7 in decode_tag
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Wire types 6 and 7 are never assigned in the protobuf wire format; only
0 (VARINT), 1 (I64), 2 (LEN), 3/4 (SGROUP/EGROUP, proto2-only), and 5
(I32) are valid. skip_field already rejected them for unknown fields,
but the decode loop in codec.lua and inline.go dispatched to a typed
reader whenever the field ID was known — the reader ignored wt and
called the value-specific decoder anyway, accepting bytes that should
have been a parse error.

Moves the check into decode_tag so every parser path — codec, generated
inline code, lazy, and map sub-fields — rejects 6/7 uniformly.

Drops 24 entries from test/conformance/known_failures.txt.
---
 runtime/pb/wire.lua                 |  8 ++++++--
 test/conformance/known_failures.txt | 24 ------------------------
 2 files changed, 6 insertions(+), 26 deletions(-)

diff --git a/runtime/pb/wire.lua b/runtime/pb/wire.lua
index 62e82c4a489a821201ed9a450c35096f6ddb1e70..a6150a66aa4ecc5b0c98d604106b497b0c73ceda 100644
--- a/runtime/pb/wire.lua
+++ b/runtime/pb/wire.lua
@@ -138,11 +138,15 @@ local function decode_tag(buf, pos)
     local b = buf:byte(pos)
     if b == nil then error("truncated varint at offset " .. pos, 0) end
     if b < 0x80 then
-        return bit.rshift(b, 3), bit.band(b, 7), pos + 1
+        local wt = bit.band(b, 7)
+        if wt >= 6 then error("illegal wire type " .. wt, 0) end
+        return bit.rshift(b, 3), wt, pos + 1
     end
     local v, npos = decode_varint(buf, pos)
     v = tonumber(v)
-    return bit.rshift(v, 3), bit.band(v, 7), npos
+    local wt = bit.band(v, 7)
+    if wt >= 6 then error("illegal wire type " .. wt, 0) end
+    return bit.rshift(v, 3), wt, npos
 end
 M.decode_tag = decode_tag
 
diff --git a/test/conformance/known_failures.txt b/test/conformance/known_failures.txt
index 4d6465b4c719ad7ea870d5e8de65d1fd807fea59..e15f5793a5132a4e5a82340d6394ec32a927c14a 100644
--- a/test/conformance/known_failures.txt
+++ b/test/conformance/known_failures.txt
@@ -80,29 +80,5 @@ Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.FLOAT
 Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.SFIXED32
 Required.Proto3.ProtobufInput.PrematureEofInsideUnknownValue.SFIXED64
 Required.Proto3.ProtobufInput.RepeatedScalarMessageMerge.ProtobufOutput
-Required.Proto3.ProtobufInput.UnknownWireType6_Field1_Version0
-Required.Proto3.ProtobufInput.UnknownWireType6_Field1_Version1
-Required.Proto3.ProtobufInput.UnknownWireType6_Field1_Version2
-Required.Proto3.ProtobufInput.UnknownWireType6_Field1_Version3
-Required.Proto3.ProtobufInput.UnknownWireType6_Field2_Version0
-Required.Proto3.ProtobufInput.UnknownWireType6_Field2_Version1
-Required.Proto3.ProtobufInput.UnknownWireType6_Field2_Version2
-Required.Proto3.ProtobufInput.UnknownWireType6_Field2_Version3
-Required.Proto3.ProtobufInput.UnknownWireType6_Field3_Version0
-Required.Proto3.ProtobufInput.UnknownWireType6_Field3_Version1
-Required.Proto3.ProtobufInput.UnknownWireType6_Field3_Version2
-Required.Proto3.ProtobufInput.UnknownWireType6_Field3_Version3
-Required.Proto3.ProtobufInput.UnknownWireType7_Field1_Version0
-Required.Proto3.ProtobufInput.UnknownWireType7_Field1_Version1
-Required.Proto3.ProtobufInput.UnknownWireType7_Field1_Version2
-Required.Proto3.ProtobufInput.UnknownWireType7_Field1_Version3
-Required.Proto3.ProtobufInput.UnknownWireType7_Field2_Version0
-Required.Proto3.ProtobufInput.UnknownWireType7_Field2_Version1
-Required.Proto3.ProtobufInput.UnknownWireType7_Field2_Version2
-Required.Proto3.ProtobufInput.UnknownWireType7_Field2_Version3
-Required.Proto3.ProtobufInput.UnknownWireType7_Field3_Version0
-Required.Proto3.ProtobufInput.UnknownWireType7_Field3_Version1
-Required.Proto3.ProtobufInput.UnknownWireType7_Field3_Version2
-Required.Proto3.ProtobufInput.UnknownWireType7_Field3_Version3
 Required.Proto3.ProtobufInput.ValidDataOneof.MESSAGE.Merge.ProtobufOutput
 Required.Proto3.TimestampProtoNegativeNanos.JsonOutput