bitlocker/
guid.rs

1//! Microsoft mixed-endian GUID formatting.
2//!
3//! A Windows GUID stores its first three fields little-endian and its final
4//! eight bytes big-endian. Formatting is pure string work (no crypto), so it is
5//! hand-written here rather than pulling in a dependency — it renders identically
6//! to the canonical `8-4-4-4-12` form `libbde`/`pybde` print.
7
8use std::fmt::Write;
9
10use crate::bytes::{le_u16, le_u32};
11
12/// Render a 16-byte Microsoft GUID in canonical `8-4-4-4-12` lowercase form.
13#[must_use]
14pub fn format_guid(raw: &[u8; 16]) -> String {
15    let d1 = le_u32(raw, 0);
16    let d2 = le_u16(raw, 4);
17    let d3 = le_u16(raw, 6);
18    let mut tail = String::with_capacity(20);
19    for (i, b) in raw[8..16].iter().enumerate() {
20        if i == 2 {
21            tail.push('-');
22        }
23        // `write!` to a String is infallible.
24        let _ = write!(tail, "{b:02x}");
25    }
26    format!("{d1:08x}-{d2:04x}-{d3:04x}-{tail}")
27}
28
29#[cfg(test)]
30mod tests {
31    use super::*;
32
33    #[test]
34    fn formats_mixed_endian_guid() {
35        // On-disk bytes of the BitLocker To Go identifier as seen in bdetogo.raw
36        // (offset 424): 3bd66749 292e d84a 8399 f6a339e3d001.
37        let raw = [
38            0x3b, 0xd6, 0x67, 0x49, 0x29, 0x2e, 0xd8, 0x4a, 0x83, 0x99, 0xf6, 0xa3, 0x39, 0xe3,
39            0xd0, 0x01,
40        ];
41        assert_eq!(format_guid(&raw), "4967d63b-2e29-4ad8-8399-f6a339e3d001");
42    }
43
44    #[test]
45    fn formats_zero_guid() {
46        assert_eq!(
47            format_guid(&[0u8; 16]),
48            "00000000-0000-0000-0000-000000000000"
49        );
50    }
51}
bitlocker/guid.rs

bitlocker/
guid.rs
