Jack Grigg
201 lines
6.4 KiB
Rust
201 lines
6.4 KiB
Rust
//! Serialization functions
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// Adapted from yubico-piv-tool:
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// <https://github.com/Yubico/yubico-piv-tool/>
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//
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// Copyright (c) 2014-2016 Yubico AB
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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//
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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use crate::{error::Error, Buffer, ObjectId, CB_OBJ_TAG_MIN};
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pub const OBJ_DISCOVERY: u32 = 0x7e;
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// TODO(tarcieri): refactor these into better serializers/message builders
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/// A Type-Length-Value object that has been parsed from a buffer.
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pub(crate) struct Tlv<'a> {
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pub(crate) tag: u8,
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pub(crate) value: &'a [u8],
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}
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impl<'a> Tlv<'a> {
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/// Parses a `Tlv` from a buffer, returning the remainder of the buffer.
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pub(crate) fn parse(buffer: &'a [u8]) -> Result<(&'a [u8], Self), Error> {
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if buffer.len() < CB_OBJ_TAG_MIN || !has_valid_length(&buffer[1..], buffer.len() - 1) {
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return Err(Error::SizeError);
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}
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let tag = buffer[0];
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let mut len = 0;
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let offset = 1 + get_length(&buffer[1..], &mut len);
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let (value, buffer) = buffer[offset..].split_at(len);
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Ok((buffer, Tlv { tag, value }))
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}
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/// Takes a [`Buffer`] containing a single `Tlv` with the given tag, and returns a
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/// `Buffer` containing only the value part of the `Tlv`.
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pub(crate) fn parse_single(mut buffer: Buffer, tag: u8) -> Result<Buffer, Error> {
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if buffer.len() < CB_OBJ_TAG_MIN || !has_valid_length(&buffer[1..], buffer.len() - 1) {
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return Err(Error::SizeError);
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}
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if tag != buffer[0] {
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return Err(Error::GenericError);
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};
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let mut len = 0;
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let offset = 1 + get_length(&buffer[1..], &mut len);
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buffer.copy_within(offset..offset + len, 0);
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buffer.truncate(len);
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Ok(buffer)
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}
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/// Writes a TLV to the given buffer.
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pub(crate) fn write(buffer: &mut [u8], tag: u8, value: &[u8]) -> Result<usize, Error> {
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if buffer.len() < CB_OBJ_TAG_MIN {
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return Err(Error::SizeError);
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}
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buffer[0] = tag;
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let offset = 1 + set_length(&mut buffer[1..], value.len())?;
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if buffer.len() < offset + value.len() {
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return Err(Error::SizeError);
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}
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buffer[offset..offset + value.len()].copy_from_slice(value);
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Ok(offset + value.len())
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}
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/// Writes a TLV to the given buffer.
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///
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/// `value` is guaranteed to be called with a mutable slice of length `length`.
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pub(crate) fn write_as<Gen>(
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buffer: &mut [u8],
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tag: u8,
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length: usize,
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value: Gen,
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) -> Result<usize, Error>
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where
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Gen: FnOnce(&mut [u8]),
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{
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if buffer.len() < CB_OBJ_TAG_MIN {
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return Err(Error::SizeError);
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}
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buffer[0] = tag;
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let offset = 1 + set_length(&mut buffer[1..], length)?;
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if buffer.len() < offset + length {
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return Err(Error::SizeError);
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}
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value(&mut buffer[offset..offset + length]);
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Ok(offset + length)
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}
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}
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/// Set length
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pub(crate) fn set_length(buffer: &mut [u8], length: usize) -> Result<usize, Error> {
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if length < 0x80 {
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if buffer.is_empty() {
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Err(Error::SizeError)
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} else {
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buffer[0] = length as u8;
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Ok(1)
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}
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} else if length < 0x100 {
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if buffer.len() < 2 {
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Err(Error::SizeError)
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} else {
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buffer[0] = 0x81;
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buffer[1] = length as u8;
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Ok(2)
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}
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} else if buffer.len() < 3 {
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Err(Error::SizeError)
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} else {
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buffer[0] = 0x82;
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buffer[1] = ((length >> 8) & 0xff) as u8;
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buffer[2] = (length & 0xff) as u8;
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Ok(3)
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}
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}
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/// Parse length tag, returning the size of the length tag itself as the
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/// returned value, and setting the len parameter to the parsed length.
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pub(crate) fn get_length(buffer: &[u8], len: &mut usize) -> usize {
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// This is not valid ASN.1 (0x80 is the indefinite length marker).
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// See comment in key::generate for more context.
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if buffer[0] < 0x81 {
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*len = buffer[0] as usize;
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1
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} else if (buffer[0] & 0x7f) == 1 {
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*len = buffer[1] as usize;
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2
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} else if (buffer[0] & 0x7f) == 2 {
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let tmp = buffer[1] as usize;
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*len = (tmp << 8) + buffer[2] as usize;
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3
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} else {
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0
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}
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}
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/// Is length valid?
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pub(crate) fn has_valid_length(buffer: &[u8], len: usize) -> bool {
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(buffer[0] < 0x81 && len > 0)
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|| ((buffer[0] & 0x7f) == 1 && len > 1)
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|| ((buffer[0] & 0x7f == 2) && (len > 2))
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}
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/// Set an object ID header value in the given buffer, returning a mutable
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/// slice immediately after the header.
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///
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/// Panics if the buffer is too small to contain the header.
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pub(crate) fn set_object(object_id: ObjectId, mut buffer: &mut [u8]) -> &mut [u8] {
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buffer[0] = 0x5c;
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if object_id == OBJ_DISCOVERY {
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buffer[1] = 1;
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buffer[2] = OBJ_DISCOVERY as u8;
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buffer = &mut buffer[3..];
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} else if object_id > 0xffff && object_id <= 0x00ff_ffff {
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buffer[1] = 3;
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buffer[2] = ((object_id >> 16) & 0xff) as u8;
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buffer[3] = ((object_id >> 8) & 0xff) as u8;
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buffer[4] = (object_id & 0xff) as u8;
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buffer = &mut buffer[5..];
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}
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buffer
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}
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