DER canonical encoding for INTEGERs #1395
Description
Trying to decode a simple DER payload [0x02, 0x00] as an INTEGER, I get an ASN.1 INTEGER not canonically encoded as DER error. Obviously [0x02, 0x01, 0x00] works correctly and decode as 0.
I took a look at ITU-T X.690 specification and I was not able to find a section describing this restriction, neither in paragraph 9 (Canonical Encoding Rules), nor in paragraph 10 (Distinguished encoding rules). There are some restrictions on Length form, but it seems there is nothing that doesn't allow to have only one byte for length with value 0x00, as is specified in section 8.1.3.4 (short form) instead.
Now, thinking about DER, i suppose that this could make sense, but i would not be wondered if next code succeded:
assert_eq!(i32::from_der(&[0x02, 0x00]), Ok(0));