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use std::io::Write;
use crate::Result;
use crate::der::{self, Tag};
pub struct Der<'a, W: Write + 'a> {
writer: &'a mut W,
}
impl<'a, W: Write> Der<'a, W> {
pub fn new(writer: &'a mut W) -> Self {
Der { writer: writer }
}
fn write_len(&mut self, len: usize) -> Result<()> {
if len >= 128 {
let n = der::length_of_length(len);
self.writer.write_all(&[0x80 | n])?;
for i in (1..n + 1).rev() {
self.writer.write_all(&[(len >> ((i - 1) * 8)) as u8])?;
}
} else {
self.writer.write_all(&[len as u8])?;
}
Ok(())
}
pub fn null(&mut self) -> Result<()> {
Ok(self.writer.write_all(&[Tag::Null as u8, 0])?)
}
pub fn element(&mut self, tag: Tag, input: &[u8]) -> Result<()> {
self.writer.write_all(&[tag as u8])?;
self.write_len(input.len())?;
self.writer.write_all(input)?;
Ok(())
}
pub fn integer(&mut self, input: &[u8]) -> Result<()> {
self.writer.write_all(&[Tag::Integer as u8])?;
self.write_len(input.len())?;
self.writer.write_all(input)?;
Ok(())
}
pub fn positive_integer(&mut self, input: &[u8]) -> Result<()> {
self.writer.write_all(&[Tag::Integer as u8])?;
let push_zero = if input.len() > 0 {
input[0] & 0x80 == 0x80
} else {
false
};
self.write_len(input.len() + push_zero as usize)?;
if push_zero {
self.writer.write_all(&[0x00])?;
}
self.writer.write_all(input)?;
Ok(())
}
pub fn nested<F: FnOnce(&mut Der<Vec<u8>>) -> Result<()>>(
&mut self,
tag: Tag,
func: F,
) -> Result<()> {
let mut buf = Vec::new();
{
let mut inner = Der::new(&mut buf);
func(&mut inner)?;
}
self.writer.write_all(&[tag as u8])?;
self.write_len(buf.len())?;
Ok(self.writer.write_all(&buf)?)
}
pub fn sequence<F: FnOnce(&mut Der<Vec<u8>>) -> Result<()>>(&mut self, func: F) -> Result<()> {
self.nested(Tag::Sequence, func)
}
pub fn oid(&mut self, input: &[u8]) -> Result<()> {
self.writer.write_all(&[Tag::Oid as u8])?;
self.write_len(input.len())?;
self.writer.write_all(&input)?;
Ok(())
}
pub fn raw(&mut self, input: &[u8]) -> Result<()> {
Ok(self.writer.write_all(input)?)
}
pub fn bit_string(&mut self, unused_bits: u8, bit_string: &[u8]) -> Result<()> {
self.writer.write_all(&[Tag::BitString as u8])?;
self.write_len(bit_string.len() + 1)?;
self.writer.write_all(&[unused_bits])?;
self.writer.write_all(&bit_string)?;
Ok(())
}
pub fn octet_string(&mut self, octet_string: &[u8]) -> Result<()> {
self.writer.write_all(&[Tag::OctetString as u8])?;
self.write_len(octet_string.len())?;
self.writer.write_all(&octet_string)?;
Ok(())
}
}
#[cfg(test)]
mod test {
use super::*;
use untrusted::Input;
use crate::Error;
static RSA_2048_PKCS1: &'static [u8] = include_bytes!("../tests/rsa-2048.pkcs1.der");
#[test]
fn write_pkcs1() {
let input = Input::from(RSA_2048_PKCS1);
let (n, e) = input
.read_all(Error::Read, |input| {
der::nested(input, Tag::Sequence, |input| {
let n = der::positive_integer(input)?;
let e = der::positive_integer(input)?;
Ok((n.as_slice_less_safe(), e.as_slice_less_safe()))
})
})
.unwrap();
let mut buf = Vec::new();
{
let mut der = Der::new(&mut buf);
der.sequence(|der| {
der.positive_integer(n)?;
der.positive_integer(e)
})
.unwrap();
}
assert_eq!(buf.as_slice(), RSA_2048_PKCS1);
}
#[test]
fn write_octet_string() {
let mut buf = Vec::new();
{
let mut der = Der::new(&mut buf);
der.octet_string(&[]).unwrap();
}
assert_eq!(&buf, &[0x04, 0x00]);
let mut buf = Vec::new();
{
let mut der = Der::new(&mut buf);
der.octet_string(&[0x0a, 0x0b, 0x0c]).unwrap();
}
assert_eq!(&buf, &[0x04, 0x03, 0x0a, 0x0b, 0x0c]);
}
}