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//! Handling ASCII Armor (see [RFC 4880, section
//! 6](https://tools.ietf.org/html/rfc4880#section-6)).
extern crate base64;
use std::io::Write;
use std::io::{Error, ErrorKind};
use std::cmp::min;
/// The encoded output stream must be represented in lines of no more
/// than 76 characters each (see (see [RFC 4880, section
/// 6.3](https://tools.ietf.org/html/rfc4880#section-6.3). GnuPG uses
/// 64.
const LINE_LENGTH: usize = 64;
const LINE_ENDING: &str = "\n";
/// Specifies the type of data that is to be encoded (see [RFC 4880,
/// section 6.2](https://tools.ietf.org/html/rfc4880#section-6.2)).
pub enum Kind {
/// A generic OpenPGP message.
Message,
/// A transferable public key.
PublicKey,
/// A transferable secret key.
PrivateKey,
/// Alias for PrivateKey.
SecretKey,
/// A detached signature.
Signature,
/// A generic file. This is a GnuPG extension.
File,
}
impl Kind {
fn blurb(&self) -> &str {
match self {
&Kind::Message => "MESSAGE",
&Kind::PublicKey => "PUBLIC KEY BLOCK",
&Kind::PrivateKey => "PRIVATE KEY BLOCK",
&Kind::SecretKey => "PRIVATE KEY BLOCK",
&Kind::Signature => "SIGNATURE",
&Kind::File => "ARMORED FILE",
}
}
}
/// A filter that applies ASCII Armor to the data written to it.
pub struct Writer<'a, W: 'a + Write> {
sink: &'a mut W,
kind: Kind,
stash: Vec<u8>,
column: usize,
crc: CRC,
initialized: bool,
finalized: bool,
}
impl<'a, W: Write> Writer<'a, W> {
/// Construct a new filter for the given type of data.
pub fn new(inner: &'a mut W, kind: Kind) -> Self {
Writer {
sink: inner,
kind: kind,
stash: Vec::<u8>::with_capacity(3),
column: 0,
crc: CRC::new(),
initialized: false,
finalized: false,
}
}
/// Write the header if not already done.
fn initialize(&mut self) -> Result<(), Error> {
if self.initialized { return Ok(()) }
write!(self.sink, "-----BEGIN PGP {}-----{}{}", self.kind.blurb(),
LINE_ENDING, LINE_ENDING)?;
self.initialized = true;
Ok(())
}
/// Write the footer. No more data can be written after this
/// call. If this is not called explicitly, the header is written
/// once the writer is dropped.
pub fn finalize(&mut self) -> Result<(), Error> {
if self.finalized {
return Err(Error::new(ErrorKind::BrokenPipe, "Writer is finalized."));
}
// Write any stashed bytes and pad.
if self.stash.len() > 0 {
self.sink.write_all(base64::encode_config(&self.stash,
base64::STANDARD).as_bytes())?;
self.column += 4;
}
self.linebreak()?;
if self.column > 0 {
write!(self.sink, "{}", LINE_ENDING)?;
}
let crc = self.crc.finalize();
let bytes: [u8; 3] = [
(crc >> 16) as u8,
(crc >> 8) as u8,
(crc >> 0) as u8,
];
// CRC and footer.
write!(self.sink, "={}{}-----END PGP {}-----{}",
base64::encode_config(&bytes, base64::STANDARD_NO_PAD),
LINE_ENDING, self.kind.blurb(), LINE_ENDING)?;
self.finalized = true;
Ok(())
}
/// Insert a line break if necessary.
fn linebreak(&mut self) -> Result<(), Error> {
assert!(self.column <= LINE_LENGTH);
if self.column == LINE_LENGTH {
write!(self.sink, "{}", LINE_ENDING)?;
self.column = 0;
}
Ok(())
}
}
impl<'a, W: Write> Write for Writer<'a, W> {
fn write(&mut self, buf: &[u8]) -> Result<usize, Error> {
self.initialize()?;
if self.finalized {
return Err(Error::new(ErrorKind::BrokenPipe, "Writer is finalized."));
}
// Update CRC on the unencoded data.
self.crc.update(buf);
let mut input = buf;
let mut written = 0;
// First of all, if there are stashed bytes, fill the stash
// and encode it.
if self.stash.len() > 0 {
while self.stash.len() < 3 {
self.stash.push(input[0]);
input = &input[1..];
written += 1;
}
self.sink.write_all(base64::encode_config(&self.stash,
base64::STANDARD_NO_PAD).as_bytes())?;
self.column += 4;
self.linebreak()?;
self.stash.clear();
}
// Ensure that a multiple of 3 bytes are encoded, stash the
// rest from the end of input.
while input.len() % 3 > 0 {
self.stash.push(input[input.len()-1]);
input = &input[..input.len()-1];
written += 1;
}
// We popped values from the end of the input, fix the order.
self.stash.reverse();
// We know that we have a multiple of 3 bytes, encode them and write them out.
assert!(input.len() % 3 == 0);
let encoded = base64::encode_config(input, base64::STANDARD_NO_PAD);
let mut enc = encoded.as_bytes();
while enc.len() > 0 {
let n = min(LINE_LENGTH - self.column, enc.len());
self.sink.write_all(&enc[..n])?;
enc = &enc[n..];
written += n;
self.column += n;
self.linebreak()?;
}
Ok(written)
}
fn flush(&mut self) -> Result<(), Error> {
self.sink.flush()
}
}
impl<'a, W: Write> Drop for Writer<'a, W> {
fn drop(&mut self) {
let _ = self.finalize();
}
}
const CRC24_INIT: u32 = 0xB704CE;
const CRC24_POLY: u32 = 0x1864CFB;
struct CRC {
n: u32,
}
/// Computes the CRC-24, (see [RFC 4880, section
/// 6.1](https://tools.ietf.org/html/rfc4880#section-6.1)).
impl CRC
|