commit e0f9ede83a282e2f8f02c81124b8f4ae800492c4
author Andrei Litvin <andy314@gmail.com> Thu May 02 15:06:07 2024 -0400
committer GitHub <noreply@github.com> Thu May 02 19:06:07 2024 +0000
tree de70e4a40bac35a9bcd0fd3f3f925f6e8ce0e8de
parent 74c95db031b0bbd44ff12de6d844dc6d3621d128

Fix off-by-one in look checks for QName iterators. (#33273)

Unit test sizes for the string `test` were off by one which
masked a off-by-one comparison in QName handling.

Update unit test and comparisons. This will disallow
backward references to "self" for qnames.

Co-authored-by: Andrei Litvin <andreilitvin@google.com>

src/lib/dnssd/minimal_mdns/core/QName.cpp

diff --git a/src/lib/dnssd/minimal_mdns/core/QName.cpp b/src/lib/dnssd/minimal_mdns/core/QName.cpp
index 2cc6488..880c9ea 100644
--- a/src/lib/dnssd/minimal_mdns/core/QName.cpp
+++ b/src/lib/dnssd/minimal_mdns/core/QName.cpp
@@ -61,7 +61,7 @@
             }
 
             size_t offset = static_cast<size_t>(((*mCurrentPosition & 0x3F) << 8) | *(mCurrentPosition + 1));
-            if (offset > mLookBehindMax)
+            if (offset >= mLookBehindMax)
             {
                 // Potential infinite recursion.
                 mIsValid = false;

src/lib/dnssd/minimal_mdns/core/tests/TestQName.cpp

diff --git a/src/lib/dnssd/minimal_mdns/core/tests/TestQName.cpp b/src/lib/dnssd/minimal_mdns/core/tests/TestQName.cpp
index 5f430bd..46c0b51 100644
--- a/src/lib/dnssd/minimal_mdns/core/tests/TestQName.cpp
+++ b/src/lib/dnssd/minimal_mdns/core/tests/TestQName.cpp
@@ -135,7 +135,7 @@
 
     {
         // Infinite recursion
-        static const uint8_t kData[] = "\03test\xc0\x00";
+        static const uint8_t kData[] = "\04test\xc0\x00";
         SerializedQNameIterator it   = AsSerializedQName(kData);
 
         EXPECT_TRUE(it.Next());
@@ -145,7 +145,7 @@
 
     {
         // Infinite recursion by referencing own element (inside the stream)
-        static const uint8_t kData[] = "\03test\xc0\x05";
+        static const uint8_t kData[] = "\04test\xc0\x05";
         SerializedQNameIterator it   = AsSerializedQName(kData);
 
         EXPECT_TRUE(it.Next());
@@ -164,7 +164,7 @@
 
     {
         // Reference that goes forwad instead of backward
-        static const uint8_t kData[] = "\03test\xc0\x07";
+        static const uint8_t kData[] = "\04test\xc0\x07";
         SerializedQNameIterator it   = AsSerializedQName(kData);
 
         EXPECT_TRUE(it.Next());