550 lines
16 KiB
Rust
550 lines
16 KiB
Rust
use super::Entry;
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use tower::http::{HeaderName, StatusCode, Method, Str};
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use bytes::{Buf, Bytes};
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use std::io::Cursor;
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use std::collections::VecDeque;
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/// Decodes headers using HPACK
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pub struct Decoder {
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// Protocol indicated that the max table size will update
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max_size_update: Option<usize>,
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table: Table,
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}
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/// Represents all errors that can be encountered while performing the decoding
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/// of an HPACK header set.
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#[derive(Debug, Copy, Clone, PartialEq)]
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pub enum DecoderError {
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InvalidRepresentation,
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InvalidIntegerPrefix,
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InvalidTableIndex,
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IntegerUnderflow,
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IntegerOverflow,
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}
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enum Representation {
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/// Indexed header field representation
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///
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/// An indexed header field representation identifies an entry in either the
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/// static table or the dynamic table (see Section 2.3).
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///
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/// # Header encoding
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///
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/// ```text
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/// 0 1 2 3 4 5 6 7
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/// +---+---+---+---+---+---+---+---+
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/// | 1 | Index (7+) |
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/// +---+---------------------------+
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/// ```
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Indexed,
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/// Literal Header Field with Incremental Indexing
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///
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/// A literal header field with incremental indexing representation results
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/// in appending a header field to the decoded header list and inserting it
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/// as a new entry into the dynamic table.
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///
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/// # Header encoding
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///
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/// ```text
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/// 0 1 2 3 4 5 6 7
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/// +---+---+---+---+---+---+---+---+
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/// | 0 | 1 | Index (6+) |
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/// +---+---+-----------------------+
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/// | H | Value Length (7+) |
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/// +---+---------------------------+
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/// | Value String (Length octets) |
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/// +-------------------------------+
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/// ```
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LiteralWithIndexing,
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/// Literal Header Field without Indexing
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///
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/// A literal header field without indexing representation results in
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/// appending a header field to the decoded header list without altering the
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/// dynamic table.
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///
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/// # Header encoding
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///
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/// ```text
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/// 0 1 2 3 4 5 6 7
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/// +---+---+---+---+---+---+---+---+
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/// | 0 | 0 | 0 | 0 | Index (4+) |
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/// +---+---+-----------------------+
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/// | H | Value Length (7+) |
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/// +---+---------------------------+
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/// | Value String (Length octets) |
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/// +-------------------------------+
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/// ```
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LiteralWithoutIndexing,
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/// Literal Header Field Never Indexed
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///
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/// A literal header field never-indexed representation results in appending
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/// a header field to the decoded header list without altering the dynamic
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/// table. Intermediaries MUST use the same representation for encoding this
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/// header field.
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///
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/// ```text
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/// 0 1 2 3 4 5 6 7
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/// +---+---+---+---+---+---+---+---+
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/// | 0 | 0 | 0 | 1 | Index (4+) |
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/// +---+---+-----------------------+
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/// | H | Value Length (7+) |
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/// +---+---------------------------+
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/// | Value String (Length octets) |
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/// +-------------------------------+
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/// ```
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LiteralNeverIndexed,
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/// Dynamic Table Size Update
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///
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/// A dynamic table size update signals a change to the size of the dynamic
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/// table.
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///
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/// # Header encoding
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///
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/// ```text
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/// 0 1 2 3 4 5 6 7
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/// +---+---+---+---+---+---+---+---+
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/// | 0 | 0 | 1 | Max size (5+) |
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/// +---+---------------------------+
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/// ```
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SizeUpdate,
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}
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struct Table {
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entries: VecDeque<Entry>,
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size: usize,
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max_size: usize,
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}
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// ===== impl Decoder =====
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impl Decoder {
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/// Creates a new `Decoder` with all settings set to default values.
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pub fn new() -> Decoder {
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Decoder {
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max_size_update: None,
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table: Table::new(4_096),
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}
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}
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/// Decodes the headers found in the given buffer.
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pub fn decode<F>(&mut self, src: &Bytes, mut f: F) -> Result<(), DecoderError>
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where F: FnMut(Entry)
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{
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use self::Representation::*;
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let mut buf = Cursor::new(src);
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while buf.has_remaining() {
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// At this point we are always at the beginning of the next block
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// within the HPACK data. The type of the block can always be
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// determined from the first byte.
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match try!(Representation::load(peek_u8(&mut buf))) {
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Indexed => {
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f(try!(self.decode_indexed(&mut buf)));
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}
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LiteralWithIndexing => {
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unimplemented!();
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}
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LiteralWithoutIndexing => {
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unimplemented!();
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}
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LiteralNeverIndexed => {
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unimplemented!();
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}
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SizeUpdate => {
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unimplemented!();
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}
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}
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}
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Ok(())
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}
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fn decode_indexed(&self, buf: &mut Cursor<&Bytes>) -> Result<Entry, DecoderError> {
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let index = try!(decode_int(buf, 7));
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self.table.get(index)
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}
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fn decode_literal(&self, buf: &mut Cursor<&Bytes>, index: bool) -> Result<Entry, DecoderError> {
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let prefix = if index {
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6
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} else {
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4
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};
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// Extract the table index for the name, or 0 if not indexed
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let table_idx = try!(decode_int(buf, prefix));
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unimplemented!();
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}
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}
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// ===== impl Representation =====
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impl Representation {
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pub fn load(byte: u8) -> Result<Representation, DecoderError> {
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const INDEXED: u8 = 0b10000000;
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const LITERAL_WITH_INDEXING: u8 = 0b01000000;
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const LITERAL_WITHOUT_INDEXING: u8 = 0b11110000;
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const LITERAL_NEVER_INDEXED: u8 = 0b00010000;
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const SIZE_UPDATE: u8 = 0b00100000;
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if byte & INDEXED == INDEXED {
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Ok(Representation::Indexed)
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} else if byte & LITERAL_WITH_INDEXING == LITERAL_WITH_INDEXING {
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Ok(Representation::LiteralWithIndexing)
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} else if byte & LITERAL_WITHOUT_INDEXING == 0 {
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Ok(Representation::LiteralWithIndexing)
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} else if byte & LITERAL_NEVER_INDEXED == LITERAL_NEVER_INDEXED {
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Ok(Representation::LiteralNeverIndexed)
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} else if byte & SIZE_UPDATE == SIZE_UPDATE {
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Ok(Representation::SizeUpdate)
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} else {
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Err(DecoderError::InvalidRepresentation)
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}
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}
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}
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fn decode_int<B: Buf>(buf: &mut B, prefix_size: u8) -> Result<usize, DecoderError> {
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// The octet limit is chosen such that the maximum allowed *value* can
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// never overflow an unsigned 32-bit integer. The maximum value of any
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// integer that can be encoded with 5 octets is ~2^28
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const MAX_BYTES: usize = 5;
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const VARINT_MASK: u8 = 0b01111111;
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const VARINT_FLAG: u8 = 0b10000000;
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if prefix_size < 1 || prefix_size > 8 {
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return Err(DecoderError::InvalidIntegerPrefix);
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}
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if !buf.has_remaining() {
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return Err(DecoderError::IntegerUnderflow);
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}
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let mask = if prefix_size == 8 {
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0xFF
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} else {
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(1u8 << prefix_size).wrapping_sub(1)
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};
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let mut ret = (buf.get_u8() & mask) as usize;
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if ret < mask as usize {
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// Value fits in the prefix bits
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return Ok(ret);
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}
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// The int did not fit in the prefix bits, so continue reading.
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//
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// The total number of bytes used to represent the int. The first byte was
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// the prefix, so start at 1.
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let mut bytes = 1;
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// The rest of the int is stored as a varint -- 7 bits for the value and 1
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// bit to indicate if it is the last byte.
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let mut shift = 0;
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while buf.has_remaining() {
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let b = buf.get_u8();
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bytes += 1;
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ret += ((b & VARINT_MASK) as usize) << shift;
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shift += 7;
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if b & VARINT_FLAG == VARINT_FLAG {
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return Ok(ret);
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}
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if bytes == MAX_BYTES {
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// The spec requires that this situation is an error
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return Err(DecoderError::IntegerOverflow);
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}
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}
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Err(DecoderError::IntegerUnderflow)
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}
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fn peek_u8<B: Buf>(buf: &mut B) -> u8 {
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buf.bytes()[0]
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}
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// ===== impl Table =====
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impl Table {
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fn new(max_size: usize) -> Table {
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Table {
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entries: VecDeque::new(),
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size: 0,
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max_size: max_size,
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}
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}
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fn max_size(&self) -> usize {
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self.max_size
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}
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/// Returns the entry located at the given index.
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///
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/// The table is 1-indexed and constructed in such a way that the first
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/// entries belong to the static table, followed by entries in the dynamic
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/// table. They are merged into a single index address space, though.
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///
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/// This is according to the [HPACK spec, section 2.3.3.]
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/// (http://http2.github.io/http2-spec/compression.html#index.address.space)
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pub fn get(&self, index: usize) -> Result<Entry, DecoderError> {
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if index == 0 {
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return Err(DecoderError::InvalidTableIndex);
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}
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if index <= 61 {
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return Ok(get_static(index));
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}
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// Convert the index for lookup in the entries structure.
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match self.entries.get(index - 62) {
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Some(e) => Ok(e.clone()),
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None => Err(DecoderError::InvalidTableIndex),
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}
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}
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fn insert(&mut self, entry: Entry) {
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let len = entry.len();
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self.reserve(len);
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self.size += len;
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// Track the entry
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self.entries.push_front(entry);
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}
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fn reserve(&mut self, size: usize) {
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debug_assert!(size <= self.max_size);
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while self.size + size > self.max_size {
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let last = self.entries.pop_back()
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.expect("size of table != 0, but no headers left!");
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self.size -= last.len();
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}
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}
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}
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/// Get an entry from the static table
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pub fn get_static(idx: usize) -> Entry {
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use tower::http::StandardHeader::*;
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match idx {
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1 => Entry::Authority(Str::new()),
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2 => Entry::Method(Method::Get),
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3 => Entry::Method(Method::Post),
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4 => Entry::Path(Str::from_static("/")),
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5 => Entry::Path(Str::from_static("/index.html")),
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6 => Entry::Scheme(Str::from_static("http")),
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7 => Entry::Scheme(Str::from_static("https")),
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8 => Entry::Status(StatusCode::Ok),
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9 => Entry::Status(StatusCode::NoContent),
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10 => Entry::Status(StatusCode::PartialContent),
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11 => Entry::Status(StatusCode::NotModified),
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12 => Entry::Status(StatusCode::BadRequest),
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13 => Entry::Status(StatusCode::NotFound),
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14 => Entry::Status(StatusCode::InternalServerError),
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15 => Entry::Header {
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name: AcceptCharset.into(),
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value: Str::new(),
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},
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16 => Entry::Header {
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name: AcceptEncoding.into(),
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value: Str::from_static("gzip, deflate"),
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},
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17 => Entry::Header {
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name: AcceptLanguage.into(),
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value: Str::new(),
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},
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18 => Entry::Header {
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name: AcceptRanges.into(),
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value: Str::new(),
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},
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19 => Entry::Header {
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name: Accept.into(),
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value: Str::new(),
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},
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20 => Entry::Header {
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name: AccessControlAllowOrigin.into(),
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value: Str::new(),
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},
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21 => Entry::Header {
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name: Age.into(),
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value: Str::new(),
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},
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22 => Entry::Header {
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name: Allow.into(),
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value: Str::new(),
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},
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23 => Entry::Header {
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name: Authorization.into(),
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value: Str::new(),
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},
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24 => Entry::Header {
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name: CacheControl.into(),
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value: Str::new(),
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},
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25 => Entry::Header {
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name: ContentDisposition.into(),
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value: Str::new(),
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},
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26 => Entry::Header {
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name: ContentEncoding.into(),
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value: Str::new(),
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},
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27 => Entry::Header {
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name: ContentLanguage.into(),
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value: Str::new(),
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},
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28 => Entry::Header {
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name: ContentLength.into(),
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value: Str::new(),
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},
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29 => Entry::Header {
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name: ContentLocation.into(),
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value: Str::new(),
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},
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30 => Entry::Header {
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name: ContentRange.into(),
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value: Str::new(),
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},
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31 => Entry::Header {
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name: ContentType.into(),
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value: Str::new(),
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},
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32 => Entry::Header {
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name: Cookie.into(),
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value: Str::new(),
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},
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33 => Entry::Header {
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name: Date.into(),
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value: Str::new(),
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},
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34 => Entry::Header {
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name: Etag.into(),
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value: Str::new(),
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},
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35 => Entry::Header {
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name: Expect.into(),
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value: Str::new(),
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},
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36 => Entry::Header {
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name: Expires.into(),
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value: Str::new(),
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},
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37 => Entry::Header {
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name: From.into(),
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value: Str::new(),
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},
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38 => Entry::Header {
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name: Host.into(),
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value: Str::new(),
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},
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39 => Entry::Header {
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name: IfMatch.into(),
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value: Str::new(),
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},
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40 => Entry::Header {
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name: IfModifiedSince.into(),
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value: Str::new(),
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},
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41 => Entry::Header {
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name: IfNoneMatch.into(),
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value: Str::new(),
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},
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42 => Entry::Header {
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name: IfRange.into(),
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value: Str::new(),
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},
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43 => Entry::Header {
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name: IfUnmodifiedSince.into(),
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value: Str::new(),
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},
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44 => Entry::Header {
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name: LastModified.into(),
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value: Str::new(),
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},
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45 => Entry::Header {
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name: Link.into(),
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value: Str::new(),
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},
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46 => Entry::Header {
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name: Location.into(),
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value: Str::new(),
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},
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47 => Entry::Header {
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name: MaxForwards.into(),
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value: Str::new(),
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},
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48 => Entry::Header {
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name: ProxyAuthenticate.into(),
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value: Str::new(),
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},
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49 => Entry::Header {
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name: ProxyAuthorization.into(),
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value: Str::new(),
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},
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50 => Entry::Header {
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name: Range.into(),
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value: Str::new(),
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},
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51 => Entry::Header {
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name: Referer.into(),
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value: Str::new(),
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},
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52 => Entry::Header {
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name: Refresh.into(),
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value: Str::new(),
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},
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53 => Entry::Header {
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name: RetryAfter.into(),
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value: Str::new(),
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},
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54 => Entry::Header {
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name: Server.into(),
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value: Str::new(),
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},
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55 => Entry::Header {
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name: SetCookie.into(),
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value: Str::new(),
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},
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56 => Entry::Header {
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name: StrictTransportSecurity.into(),
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value: Str::new(),
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},
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57 => Entry::Header {
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name: TransferEncoding.into(),
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value: Str::new(),
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},
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58 => Entry::Header {
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name: UserAgent.into(),
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value: Str::new(),
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},
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59 => Entry::Header {
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name: Vary.into(),
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value: Str::new(),
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},
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60 => Entry::Header {
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name: Via.into(),
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value: Str::new(),
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},
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61 => Entry::Header {
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name: WwwAuthenticate.into(),
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value: Str::new(),
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},
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_ => unreachable!(),
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}
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}
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