Problem with the nextObject method of the ASN1Parser class

[GrzegorzMalina94]

Description

The method nextObjectof the ASN1Parserclass doesn't work correctly when objects with an extended tag's value are encoded in bytes. I looked at the method code. In my opinion there are two errors there.

1. The _position field is not updated when an object with an extended tag value is returned.
2. To the ASN1Object.fromBytes constructor of an object with an extended tag value, all parser bytes (_bytes) are passed. In my opinion _bytes.sublist(_position) should be passed.

To Reproduce

I prepared a small test allowing to reproduce the problem. Test will fail due to malfunction of the nextObject method.

import  'dart:typed_data';   

import  'package:asn1lib/asn1lib.dart';    
import  'package:test/test.dart';      

void  main() {    
final  sampleBytes  =  Uint8List.fromList([    
0x5f,    
0x29,    
0x01,    
0x00,    
0x42,    
0x08,    
0xfd,    
0x45,    
0x43,    
0x20,    
0x01,    
0xff,    
0xff,    
0x01,    
0x5f,    
0x4c,    
0x07,    
0xff,    
0x53,    
0x4d,    
0x52,    
0x44,    
0x54,    
0xd,    
]); 

test(    
"Test ASN1Parser.nextObject method when objects with an extended tag's "    
'value are encoded in bytes. ', () {    
final  parser  =  ASN1Parser(sampleBytes);

final  firstObj  =  parser.nextObject();    
final  secondObj  =  parser.nextObject();    
final  thirdObj  =  parser.nextObject(); 

final  expected1stObjValueBytes  =  Uint8List.fromList([  
0x00,    
]);      

final  expected2ndObjValueBytes  =  Uint8List.fromList([   
0xfd,    
0x45,    
0x43,    
0x20,    
0x01,    
0xff,    
0xff,    
0x01,    
]);

final  expected3rdObjValueBytes  =  Uint8List.fromList([   
0xff,    
0x53,    
0x4d,    
0x52,    
0x44,    
0x54,    
0x0d,   
]);         

expect(firstObj.valueBytes(), orderedEquals(expected1stObjValueBytes));    
expect(secondObj.valueBytes(), orderedEquals(expected2ndObjValueBytes));    
expect(thirdObj.valueBytes(), orderedEquals(expected3rdObjValueBytes));    
    });
}

Relevant Files

asn1Parser.dart

Tasks

They all refer to the nextObject() method of the ASN1Parser class

• [ ] Introduce an update to the _position field when an object with an extended tag value is returned.
• [ ] Correct the value passed to the ASN1Object.fromBytes() constructor when returning an object with an extended tag value.

[wstrange]

Thank you for the detailed bug report!

Are you interested in submitting a PR for this? If not - I can probably take a look at this tomorrow

[GrzegorzMalina94]

If you can, take a look at it.

[wstrange]

Just pushed 1.5.3 . Let me know if that works for you

[GrzegorzMalina94]

Yes, problem solved. Thanks.