android/vendor/rustls-0.21.10/src/x509.rs

// Additional x509/asn1 functions to those provided in webpki/ring.

use ring::io::der;

pub(crate) fn wrap_in_asn1_len(bytes: &mut Vec<u8>) {
    let len = bytes.len();

    if len <= 0x7f {
        bytes.insert(0, len as u8);
    } else {
        bytes.insert(0, 0x80u8);
        let mut left = len;
        while left > 0 {
            let byte = (left & 0xff) as u8;
            bytes.insert(1, byte);
            bytes[0] += 1;
            left >>= 8;
        }
    }
}

/// Prepend stuff to `bytes` to put it in a DER SEQUENCE.
pub(crate) fn wrap_in_sequence(bytes: &mut Vec<u8>) {
    wrap_in_asn1_len(bytes);
    bytes.insert(0, der::Tag::Sequence as u8);
}

#[test]
fn test_empty() {
    let mut val = Vec::new();
    wrap_in_sequence(&mut val);
    assert_eq!(vec![0x30, 0x00], val);
}

#[test]
fn test_small() {
    let mut val = Vec::new();
    val.insert(0, 0x00);
    val.insert(1, 0x11);
    val.insert(2, 0x22);
    val.insert(3, 0x33);
    wrap_in_sequence(&mut val);
    assert_eq!(vec![0x30, 0x04, 0x00, 0x11, 0x22, 0x33], val);
}

#[test]
fn test_medium() {
    let mut val = Vec::new();
    val.resize(255, 0x12);
    wrap_in_sequence(&mut val);
    assert_eq!(vec![0x30, 0x81, 0xff, 0x12, 0x12, 0x12], val[..6].to_vec());
}

#[test]
fn test_large() {
    let mut val = Vec::new();
    val.resize(4660, 0x12);
    wrap_in_sequence(&mut val);
    assert_eq!(vec![0x30, 0x82, 0x12, 0x34, 0x12, 0x12], val[..6].to_vec());
}

#[test]
fn test_huge() {
    let mut val = Vec::new();
    val.resize(0xffff, 0x12);
    wrap_in_sequence(&mut val);
    assert_eq!(vec![0x30, 0x82, 0xff, 0xff, 0x12, 0x12], val[..6].to_vec());
    assert_eq!(val.len(), 0xffff + 4);
}

#[test]
fn test_gigantic() {
    let mut val = Vec::new();
    val.resize(0x100000, 0x12);
    wrap_in_sequence(&mut val);
    assert_eq!(
        vec![0x30, 0x83, 0x10, 0x00, 0x00, 0x12, 0x12],
        val[..7].to_vec()
    );
    assert_eq!(val.len(), 0x100000 + 5);
}

#[test]
fn test_ludicrous() {
    let mut val = Vec::new();
    val.resize(0x1000000, 0x12);
    wrap_in_sequence(&mut val);
    assert_eq!(
        vec![0x30, 0x84, 0x01, 0x00, 0x00, 0x00, 0x12, 0x12],
        val[..8].to_vec()
    );
    assert_eq!(val.len(), 0x1000000 + 6);
}