Merge pull request #215 from hig-dev/master

Support parsing of nested objects with indefinite lengths
bcgit · Jan 11, 2024 · 4ff2c40 · 4ff2c40
2 parents 59e0602 + ef4818e
commit 4ff2c40
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Showing 3 changed files with 152 additions and 2 deletions.
diff --git a/lib/asn1/asn1_parser.dart b/lib/asn1/asn1_parser.dart
@@ -57,7 +57,13 @@ class ASN1Parser {
 
     var valueStartPosition =
         ASN1Utils.calculateValueStartPosition(bytes!.sublist(_position));
-    if (_position < length + valueStartPosition) {
+
+    var isIndefiniteLength = false;
+
+    if (length == -1) {
+      length = ASN1Utils.calculateIndefiniteLength(bytes!, _position) + 2;
+      isIndefiniteLength = true;
+    } else if (_position < length + valueStartPosition) {
       length = length + valueStartPosition;
     } else {
       length = bytes!.length - _position;
@@ -83,7 +89,8 @@ class ASN1Parser {
     }
 
     // Update the position
-    _position = _position + obj.totalEncodedByteLength;
+    _position =
+        _position + obj.totalEncodedByteLength + (isIndefiniteLength ? 2 : 0);
     return obj;
   }
 

diff --git a/lib/asn1/asn1_utils.dart b/lib/asn1/asn1_utils.dart
@@ -119,6 +119,46 @@ class ASN1Utils {
     return false;
   }
 
+  ///
+  /// Calculates the indefinite length of the ASN1 object.
+  /// Throws an [ArgumentError] if the end of content octets is not found.
+  ///
+  static int calculateIndefiniteLength(Uint8List bytes, int startPosition) {
+    var currentPosition = startPosition;
+    var indefiniteLengthObjects = 0;
+    while (currentPosition < bytes.length - 1) {
+      if (bytes[currentPosition] == 0x00 &&
+          bytes[currentPosition + 1] == 0x00) {
+        indefiniteLengthObjects--;
+        if (indefiniteLengthObjects == 0) {
+          return currentPosition - startPosition;
+        }
+        currentPosition += 2;
+      } else {
+        final nextLength =
+            ASN1Utils.decodeLength(bytes.sublist(currentPosition));
+        final valueStartPosition = ASN1Utils.calculateValueStartPosition(
+            bytes.sublist(currentPosition));
+        if (nextLength == 0) {
+          throw ArgumentError('Invalid length of zero.');
+        }
+        if (valueStartPosition <= 0) {
+          throw ArgumentError(
+              'Invalid value start position: $valueStartPosition');
+        }
+
+        if (nextLength == -1) {
+          indefiniteLengthObjects++;
+          currentPosition += valueStartPosition;
+        } else {
+          currentPosition += valueStartPosition + nextLength;
+        }
+      }
+    }
+
+    throw ArgumentError('End of content octets not found');
+  }
+
   static Uint8List getBytesFromPEMString(String pem,
       {bool checkHeader = true}) {
     var lines = LineSplitter.split(pem)

diff --git a/test/asn1/primitives/asn1_sequence_test.dart b/test/asn1/primitives/asn1_sequence_test.dart
@@ -1,6 +1,7 @@
 import 'dart:typed_data';
 
 import 'package:pointycastle/asn1/primitives/asn1_ia5_string.dart';
+import 'package:pointycastle/asn1/primitives/asn1_integer.dart';
 import 'package:pointycastle/asn1/primitives/asn1_null.dart';
 import 'package:pointycastle/asn1/primitives/asn1_object_identifier.dart';
 import 'package:pointycastle/asn1/primitives/asn1_sequence.dart';
@@ -59,6 +60,108 @@ void main() {
     expect(asn1Object.elements!.elementAt(1) is ASN1Null, true);
   });
 
+  test('Test named constructor fromBytes with nested indefinite length', () {
+    /*
+    SEQUENCE (3 elem, indefinite length)
+      INTEGER 1
+      SEQUENCE (1 elem, indefinite length)
+        OBJECT IDENTIFIER 1.2.840.113549.1.7.1 data (PKCS #7)
+      INTEGER 1
+    */
+    var bytes = Uint8List.fromList([
+      0x30,
+      0x80,
+      0x02,
+      0x01,
+      0x01,
+      0x30,
+      0x80,
+      0x06,
+      0x09,
+      0x2A,
+      0x86,
+      0x48,
+      0x86,
+      0xF7,
+      0x0D,
+      0x01,
+      0x07,
+      0x01,
+      0x00,
+      0x00,
+      0x02,
+      0x01,
+      0x01,
+      0x00,
+      0x00
+    ]);
+
+    var valueBytes = Uint8List.fromList([
+      0x02,
+      0x01,
+      0x01,
+      0x30,
+      0x80,
+      0x06,
+      0x09,
+      0x2A,
+      0x86,
+      0x48,
+      0x86,
+      0xF7,
+      0x0D,
+      0x01,
+      0x07,
+      0x01,
+      0x00,
+      0x00,
+      0x02,
+      0x01,
+      0x01,
+    ]);
+
+    var innerSequenceBytes = Uint8List.fromList([
+      0x30,
+      0x80,
+      0x06,
+      0x09,
+      0x2A,
+      0x86,
+      0x48,
+      0x86,
+      0xF7,
+      0x0D,
+      0x01,
+      0x07,
+      0x01,
+      0x00,
+      0x00
+    ]);
+
+    var innerSequenceValueBytes = Uint8List.fromList(
+        [0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x01]);
+
+    var asn1Object = ASN1Sequence.fromBytes(bytes);
+    expect(asn1Object.tag, 48);
+    expect(asn1Object.isConstructed, true);
+    expect(asn1Object.encodedBytes, bytes);
+    expect(asn1Object.valueByteLength, 21);
+    expect(asn1Object.valueStartPosition, 2);
+    expect(asn1Object.valueBytes, valueBytes);
+    expect(asn1Object.elements!.length, 3);
+    expect(asn1Object.elements!.elementAt(0) is ASN1Integer, true);
+    expect(asn1Object.elements!.elementAt(1) is ASN1Sequence, true);
+    expect(asn1Object.elements!.elementAt(2) is ASN1Integer, true);
+
+    final innerSequence = asn1Object.elements!.elementAt(1) as ASN1Sequence;
+    expect(innerSequence.tag, 48);
+    expect(innerSequence.isConstructed, true);
+    expect(innerSequence.encodedBytes, innerSequenceBytes);
+    expect(innerSequence.valueByteLength, 11);
+    expect(innerSequence.valueStartPosition, 2);
+    expect(innerSequence.valueBytes, innerSequenceValueBytes);
+  });
+
   test('Test encode', () {
     // Test encoding with zero elements given
     var asn1Object = ASN1Sequence(elements: []);