branca decode does not handle binary data

[rhizoome]

1. Take another branca implementation (eg. pybranca)
2. Encode binary data

f = Branca(fromstring(key))
ct = f.encode(b"\x80")

3. Pass ct do decode in this implementation

-> it will return b'\xef\xbf\xbd'

The spec allows binary data:

..... serialized by MessagePack or Protocol Buffers. from branca.io

[brycx]

This seems to be due to the expectation that the encoded data is valid UTF-8:

branca/src/lib.rs

Line 448 in 34758ab

Ok(String::from_utf8_lossy(&buf_crypt).into())

This is compatible with this implementation's encode function, which takes &str. But if another implementation is used to encode non-valid UTF-8, then the above happens (playground).

decode() could return Vec<u8> instead of String to solve this.

In terms of spec-compliance, then encode should probably also take raw bytes instead of &str:

"Payload itself is an arbitrary sequence of bytes."

[J-F-Liu]

@brycx Suggest use AsRef<[u8]> in encode function.

pub fn encode<T: AsRef<[u8]>>(data: T, key: &[u8], timestamp: u32) -> Result<String, BrancaError>

[brycx]

@J-F-Liu Thank you for the suggestion. I think your proposal could be a good idea. However, @return currently is very busy and has given me permission to merge and update the crate with the purpose of fixing current bugs. As there were no generic parameters used in function signatures before, I will not add these now. This is simply to change as little as possible in order to fix the issue and stick to the current API as much as possible. I will open an issue for generic parameters, which @return can then decide upon once they have time again.