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// Copyright 2019 Alexandros Frantzis
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.
//
// SPDX-License-Identifier: MPL-2.0
//! Base64 and quoted-printable decoding.
use crate::Result;
const PAD: u8 = 64; // The pseudo-index of the PAD character.
const INV: u8 = 99; // An invalid index.
static BASE64_INDICES: &'static [u8] = &[
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
/* 0 */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* 1 */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* 2 */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, 62, INV, INV, INV, 63,
/* 3 */ 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, INV, INV, INV, PAD, INV, INV,
/* 4 */ INV, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
/* 5 */ 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, INV, INV, INV, INV, INV,
/* 6 */ INV, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
/* 7 */ 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, INV, INV, INV, INV, INV,
/* 8 */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* 9 */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* A */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* B */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* C */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* D */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* E */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
/* F */ INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV, INV,
];
/// Decodes base64 encoded data, appending the decoded data to a Vec<u8>.
///
/// During decoding all line breaks and invalid characters are ignored.
/// If an error is encountered during decoding, the already decoded data in the
/// output buffer is left intact. It's up to the caller to deal with the partial
/// decoded data in case of failure.
pub fn base64_decode_into_buf(input: &[u8], output: &mut Vec<u8>) -> Result<()> {
let mut num_chars = 0;
let mut cur_triplet = 0;
let mut valid_chars = 0;
for c in input {
let ci = BASE64_INDICES[*c as usize];
match ci {
// rfc2045: All line breaks or other characters not
// found in Table 1 must be ignored by decoding software.
INV => continue,
_ if ci < PAD => valid_chars += 1,
_ => {}
}
cur_triplet = cur_triplet << 6 | ((ci & 0x3f) as u32);
num_chars += 1;
if num_chars == 4 {
match valid_chars {
2 => output.push((cur_triplet >> 16) as u8),
3 => output.extend(
&[(cur_triplet >> 16) as u8, (cur_triplet >> 8) as u8]
),
4 => output.extend(
&[(cur_triplet >> 16) as u8,
(cur_triplet >> 8) as u8,
cur_triplet as u8
]
),
_ => return Err("Invalid base64 encoding".into()),
}
cur_triplet = 0;
num_chars = 0;
valid_chars = 0;
}
}
// rfc2045: A full encoding quantum is always completed at the end of a body.
if num_chars != 0 {
return Err("Unpadded input".into());
}
Ok(())
}
/// Converts an ascii byte representing a hex digit to it's numerical value.
fn hexdigit_to_num(mut a: u8) -> Option<u8> {
if a.is_ascii_digit() {
return Some(a - b'0');
}
a.make_ascii_lowercase();
if a >= b'a' && a <= b'f' {
return Some(a - b'a' + 10);
}
None
}
/// Decodes quoted-printable encoded data, appending the decoding data to a
/// Vec<u8>.
///
/// During decoding all line breaks and invalid characters are ignored.
/// If an error is encountered during decoding, the already decoded data in the
/// output buffer is left intact. It's up to the caller to deal with the partial
/// decoded data in case of failure.
pub fn qp_decode_into_buf(input: &[u8], output: &mut Vec<u8>) -> Result<()> {
let mut iter = input.iter().peekable();
'outer: loop {
loop {
match iter.next() {
Some(b'=') => break,
Some(c) => output.push(*c),
None => break 'outer,
}
}
// At this point we have encountered a '=', so check
// to see what follows.
if let Some(&first) = iter.next() {
// A CRLF/LF after '=' marks a line continuation, and
// is effectively dropped.
if first == b'\r' {
if iter.peek() == Some(&&b'\n') {
iter.next();
continue;
}
} else if first == b'\n' {
continue;
} else if let Some(first_num) = hexdigit_to_num(first) {
// A valid pair of hexdigits represent the raw byte value.
if let Some(&&second) = iter.peek() {
if let Some(second_num) = hexdigit_to_num(second) {
output.push(first_num * 16 + second_num);
iter.next();
continue;
}
}
}
// Emit the raw sequence if it's not one of the special
// special cases checked above.
output.extend(&[b'=', first]);
} else {
// Last character in the input was an '=', just emit it.
output.push(b'=');
}
}
Ok(())
}
#[cfg(test)]
mod test_base64 {
use crate::decode::base64_decode_into_buf;
#[test]
fn decodes_full_length() {
let mut decoded = Vec::new();
assert!(base64_decode_into_buf("YWJj".as_bytes(), &mut decoded).is_ok());
assert_eq!(decoded, &[b'a', b'b', b'c']);
}
#[test]
fn decodes_with_two_padding() {
let mut decoded = Vec::new();
assert!(base64_decode_into_buf("YWJjZA==".as_bytes(), &mut decoded).is_ok());
assert_eq!(decoded, &[b'a', b'b', b'c', b'd']);
}
#[test]
fn decodes_with_one_padding() {
let mut decoded = Vec::new();
assert!(base64_decode_into_buf("YWJjZGU=".as_bytes(), &mut decoded).is_ok());
assert_eq!(decoded, &[b'a', b'b', b'c', b'd', b'e']);
}
#[test]
fn error_with_invalid_paddings() {
let mut decoded = Vec::new();
assert!(base64_decode_into_buf("YWJj====".as_bytes(), &mut decoded).is_err());
assert!(base64_decode_into_buf("YWJjZ===".as_bytes(), &
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