From 2631306da61de29379b23d10442f8cd9fd1f7086 Mon Sep 17 00:00:00 2001
From: Ari Kauppi <kauppi@papupata.org>
Date: Wed, 1 Jan 2025 23:28:50 +0400
Subject: [PATCH] Fix ASN1Parser length parsing

The current length parsing is comparing offset in parsed bytestream to sub-object length.
Sometimes this leads to last branch being taken for an object in middle of ASN1Sequence.
Due to that, excess bytes are included to encodedBytes.

It looks like the intention of the if construct is a bounds check. Fix that.
---
 lib/asn1/asn1_parser.dart       |  2 +-
 test/asn1/asn1_parser_test.dart | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/lib/asn1/asn1_parser.dart b/lib/asn1/asn1_parser.dart
index 55884043..e1313358 100644
--- a/lib/asn1/asn1_parser.dart
+++ b/lib/asn1/asn1_parser.dart
@@ -63,7 +63,7 @@ class ASN1Parser {
     if (length == -1) {
       length = ASN1Utils.calculateIndefiniteLength(bytes!, _position) + 2;
       isIndefiniteLength = true;
-    } else if (_position < length + valueStartPosition) {
+    } else if (bytes!.length - _position > length + valueStartPosition) {
       length = length + valueStartPosition;
     } else {
       length = bytes!.length - _position;
diff --git a/test/asn1/asn1_parser_test.dart b/test/asn1/asn1_parser_test.dart
index b642c02e..58343259 100644
--- a/test/asn1/asn1_parser_test.dart
+++ b/test/asn1/asn1_parser_test.dart
@@ -176,6 +176,7 @@ void main() {
     expect(set1.elements!.elementAt(0) is ASN1Sequence, true);
 
     var seq1 = set1.elements!.elementAt(0) as ASN1Sequence;
+    expect(seq1.encodedBytes!.length, seq1.totalEncodedByteLength);
     expect(seq1.elements!.length, 2);
     expect(seq1.elements!.elementAt(0) is ASN1ObjectIdentifier, true);
     expect(seq1.elements!.elementAt(1) is ASN1PrintableString, true);
@@ -189,6 +190,7 @@ void main() {
     expect(set2.elements!.elementAt(0) is ASN1Sequence, true);
 
     var seq2 = set2.elements!.elementAt(0) as ASN1Sequence;
+    expect(seq2.encodedBytes!.length, seq2.totalEncodedByteLength);
     expect(seq2.elements!.length, 2);
     expect(seq2.elements!.elementAt(0) is ASN1ObjectIdentifier, true);
     expect(seq2.elements!.elementAt(1) is ASN1PrintableString, true);
@@ -202,6 +204,7 @@ void main() {
     expect(set3.elements!.elementAt(0) is ASN1Sequence, true);
 
     var seq3 = set3.elements!.elementAt(0) as ASN1Sequence;
+    expect(seq3.encodedBytes!.length, seq3.totalEncodedByteLength);
     expect(seq3.elements!.length, 2);
     expect(seq3.elements!.elementAt(0) is ASN1ObjectIdentifier, true);
     expect(seq3.elements!.elementAt(1) is ASN1PrintableString, true);
@@ -215,6 +218,7 @@ void main() {
     expect(set4.elements!.elementAt(0) is ASN1Sequence, true);
 
     var seq4 = set4.elements!.elementAt(0) as ASN1Sequence;
+    expect(seq4.encodedBytes!.length, seq4.totalEncodedByteLength);
     expect(seq4.elements!.length, 2);
     expect(seq4.elements!.elementAt(0) is ASN1ObjectIdentifier, true);
     expect(seq4.elements!.elementAt(1) is ASN1PrintableString, true);
@@ -286,6 +290,7 @@ RVTxIJddHhpHfW5c2lX+ERf3Ni0fcJqcCZBPyGHUDSYqNrDwRLQ6dyVxz1Jl0oAc
 
     expect(e1.elements!.length, 8);
     expect(e1.totalEncodedByteLength, 1444);
+    expect(e1.encodedBytes!.length, 1444);
     expect(e1.valueByteLength, 1440);
     expect(e1.elements!.elementAt(1) is ASN1Integer, true);
     expect(e1.elements!.elementAt(2) is ASN1Sequence, true);
@@ -309,8 +314,15 @@ RVTxIJddHhpHfW5c2lX+ERf3Ni0fcJqcCZBPyGHUDSYqNrDwRLQ6dyVxz1Jl0oAc
     expect(
         integer2.integer.toString(), '49732821766751726239505489314635506967');
 
+    var seq1 = e1.elements!.elementAt(2) as ASN1Sequence;
+    expect(seq1.encodedBytes!.length, seq1.totalEncodedByteLength);
+
+    var seq2 = e1.elements!.elementAt(3) as ASN1Sequence;
+    expect(seq2.encodedBytes!.length, seq2.totalEncodedByteLength);
+
     expect(e2.elements!.length, 2);
     expect(e2.totalEncodedByteLength, 15);
+    expect(e2.encodedBytes!.length, 15);
     expect(e2.valueByteLength, 13);
     expect(e2.elements!.elementAt(0) is ASN1ObjectIdentifier, true);
     expect(e2.elements!.elementAt(1) is ASN1Null, true);