From 3908f144229eed4df24bd569d16e5991ace44970 Mon Sep 17 00:00:00 2001
From: Simon Pichugin <simon.pichugin@gmail.com>
Date: Fri, 16 Jan 2026 08:57:23 -0800
Subject: [PATCH] Merge commit from fork

Add limit of 20 continuation octets per OID arc to prevent a potential memory
exhaustion from excessive continuation bytes input.
---
 pyasn1/codec/ber/decoder.py     |  20 ++++-
 tests/codec/ber/test_decoder.py | 130 ++++++++++++++++++++++++++++++++
 2 files changed, 149 insertions(+), 1 deletion(-)

Index: pyasn1-0.5.0/pyasn1/codec/ber/decoder.py
===================================================================
--- pyasn1-0.5.0.orig/pyasn1/codec/ber/decoder.py
+++ pyasn1-0.5.0/pyasn1/codec/ber/decoder.py
@@ -32,6 +32,10 @@ noValue = base.noValue
 
 SubstrateUnderrunError = error.SubstrateUnderrunError
 
+# Maximum number of continuation octets (high-bit set) allowed per OID arc.
+# 20 octets allows up to 140-bit integers, supporting UUID-based OIDs
+MAX_OID_ARC_CONTINUATION_OCTETS = 20
+
 
 class AbstractPayloadDecoder(object):
     protoComponent = None
@@ -428,7 +432,14 @@ class ObjectIdentifierPayloadDecoder(Abs
                 # Construct subid from a number of octets
                 nextSubId = subId
                 subId = 0
+                continuationOctetCount = 0
                 while nextSubId >= 128:
+                    continuationOctetCount += 1
+                    if continuationOctetCount > MAX_OID_ARC_CONTINUATION_OCTETS:
+                        raise error.PyAsn1Error(
+                            'OID arc exceeds maximum continuation octets limit (%d) '
+                            'at position %d' % (MAX_OID_ARC_CONTINUATION_OCTETS, index)
+                        )
                     subId = (subId << 7) + (nextSubId & 0x7F)
                     if index >= substrateLen:
                         raise error.SubstrateUnderrunError(
Index: pyasn1-0.5.0/tests/codec/ber/test_decoder.py
===================================================================
--- pyasn1-0.5.0.orig/tests/codec/ber/test_decoder.py
+++ pyasn1-0.5.0/tests/codec/ber/test_decoder.py
@@ -483,6 +483,72 @@ class RealDecoderTestCase(BaseTestCase):
         else:
             assert 0, 'accepted too-short real'
 
+    def testExcessiveContinuationOctets(self):
+        """Test that OID arcs with excessive continuation octets are rejected."""
+        # Create a payload with 25 continuation octets (exceeds 20 limit)
+        # 0x81 bytes are continuation octets, 0x01 terminates
+        malicious_payload = bytes([0x06, 26]) + bytes([0x81] * 25) + bytes([0x01])
+        try:
+            decoder.decode(malicious_payload)
+        except error.PyAsn1Error:
+            pass
+        else:
+            assert 0, 'Excessive continuation octets tolerated'
+
+    def testMaxAllowedContinuationOctets(self):
+        """Test that OID arcs at the maximum continuation octets limit work."""
+        # Create a payload with exactly 20 continuation octets (at limit)
+        # This should succeed
+        payload = bytes([0x06, 21]) + bytes([0x81] * 20) + bytes([0x01])
+        try:
+            decoder.decode(payload)
+        except error.PyAsn1Error:
+            assert 0, 'Valid OID with 20 continuation octets rejected'
+
+    def testOneOverContinuationLimit(self):
+        """Test boundary: 21 continuation octets (one over limit) is rejected."""
+        payload = bytes([0x06, 22]) + bytes([0x81] * 21) + bytes([0x01])
+        try:
+            decoder.decode(payload)
+        except error.PyAsn1Error:
+            pass
+        else:
+            assert 0, '21 continuation octets tolerated (should be rejected)'
+
+    def testExcessiveContinuationInSecondArc(self):
+        """Test that limit applies to subsequent arcs, not just the first."""
+        # First arc: valid simple byte (0x55 = 85, decodes to arc 2.5)
+        # Second arc: excessive continuation octets
+        payload = bytes([0x06, 27]) + bytes([0x55]) + bytes([0x81] * 25) + bytes([0x01])
+        try:
+            decoder.decode(payload)
+        except error.PyAsn1Error:
+            pass
+        else:
+            assert 0, 'Excessive continuation in second arc tolerated'
+
+    def testMultipleArcsAtLimit(self):
+        """Test multiple arcs each at the continuation limit work correctly."""
+        # Two arcs, each with 20 continuation octets (both at limit)
+        arc1 = bytes([0x81] * 20) + bytes([0x01])  # 21 bytes
+        arc2 = bytes([0x81] * 20) + bytes([0x01])  # 21 bytes
+        payload = bytes([0x06, 42]) + arc1 + arc2
+        try:
+            decoder.decode(payload)
+        except error.PyAsn1Error:
+            assert 0, 'Multiple valid arcs at limit rejected'
+
+    def testExcessiveContinuationWithMaxBytes(self):
+        """Test with 0xFF continuation bytes (maximum value, not just 0x81)."""
+        # 0xFF bytes are also continuation octets (high bit set)
+        malicious_payload = bytes([0x06, 26]) + bytes([0xFF] * 25) + bytes([0x01])
+        try:
+            decoder.decode(malicious_payload)
+        except error.PyAsn1Error:
+            pass
+        else:
+            assert 0, 'Excessive 0xFF continuation octets tolerated'
+
 
 class UniversalStringDecoderTestCase(BaseTestCase):
     def testDecoder(self):