Unexpected format result with Uuid ToString method

[ivila]

Problem

I found some unexpected results when using the ToString method of Uuid, In both optee_utee and optee_teec:

1. the output formation is different with input

the parse_str method require formation of neither 32 bytes or 36 bytes (just what the uuid crate defined), however, the realization of Display trait of optee_teec::Uuid and optee_utee::Uuid will output a str with 35 bytes.
for example:

fn test() {
    let uuid_str = "6bfaa402-50ed-42f2-9bde-b2aecfa216c2";
    let uuid = optee_teec::Uuid::parse_str(uuid_str).unwrap();
    let uuid_str2 = uuid.to_string();  // this is "6bfaa402-50ed-42f2-9bdeb2aecfa216c2", the last "-" is missing
}

2. missing the prefix zeros:

the formation teaclave use is "{:x}-{:x}-{:x}-{}", which will get an unexpected result when format number has zeros at front, for example:

fn main() {
    let uuids = vec![
        "00173366-2aca-49bc-beb7-10c975e6131e",
        "11173366-0aca-49bc-beb7-10c975e6131e",
        "11173366-2aca-09bc-beb7-10c975e6131e",
        "11173366-2aca-19bc-beb7-10c975e6131e",
    ];
    for (i, raw) in uuids.iter().enumerate() {
        let tmp = optee_teec::Uuid::parse_str(raw).unwrap();
        let formatted = tmp.to_string();
        let raw2 = to_same_format(raw);
        println!(
            "str {}\norigin: {}\nparsed: {}\nequal: {}\n",
            i,
            raw2,
            formatted,
            raw2.eq_ignore_ascii_case(&formatted),
        );
    }
}

fn to_same_format(origin: &str) -> String {
    assert_eq!(origin.len(), 36);
    let mut buffer = Vec::with_capacity(35);
    buffer.extend(origin.as_bytes()[0..23].iter());
    buffer.extend(origin.as_bytes()[24..36].iter());
    assert_eq!(buffer.len(), 35);
    String::from_utf8(buffer).unwrap()
}

the codes will produce:

str 0
origin: 00173366-2aca-49bc-beb710c975e6131e
parsed: 173366-2aca-49bc-beb710c975e6131e
equal: false

str 1
origin: 11173366-0aca-49bc-beb710c975e6131e
parsed: 11173366-aca-49bc-beb710c975e6131e
equal: false

str 2
origin: 11173366-2aca-09bc-beb710c975e6131e
parsed: 11173366-2aca-9bc-beb710c975e6131e
equal: false

str 3
origin: 11173366-2aca-19bc-beb710c975e6131e
parsed: 11173366-2aca-19bc-beb710c975e6131e
equal: true

Suggest Solution

I wish we could just produce output string as same as the input string(the 36 bytes format with no missing prefix zeros, as this is how tee-supplicant finds the TA), in short, just change the realization of Display traits, from:

impl fmt::Display for Uuid {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "{:x}-{:x}-{:x}-{}",
            self.raw.timeLow,
            self.raw.timeMid,
            self.raw.timeHiAndVersion,
            hex::encode(self.raw.clockSeqAndNode)
        )
    }
}

to

impl fmt::Display for Uuid {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "{:08x}-{:04x}-{:04x}-{}-{}",
            self.raw.timeLow,
            self.raw.timeMid,
            self.raw.timeHiAndVersion,
            hex::encode(&self.raw.clockSeqAndNode[0..2]),
            hex::encode(&self.raw.clockSeqAndNode[2..8]),
        )
    }
}

[DemesneGH]

Please feel free to open the PR, thanks!

[DemesneGH]

It's okay to have two commits in a single PR. Thanks!

[ivila]

@DemesneGH A PR was created, and the pipeline passed, can you take a look at it?