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Fix unknown handling in impl_writeable_tlv_based_enum_upgradable #2969

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merged 3 commits into from
Apr 8, 2024
Merged

Fix unknown handling in impl_writeable_tlv_based_enum_upgradable #2969

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cc78b77
Fix unknown handling in `impl_writeable_tlv_based_enum_upgradable`
TheBlueMatt Mar 26, 2024
d6770d4
Ensure we read the full TLV stream length when maybe-reading `None`
TheBlueMatt Mar 28, 2024
f852d16
Allow `MaybeReadable` to not fully read in `upgradable_option`
TheBlueMatt Mar 28, 2024
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6 changes: 5 additions & 1 deletion lightning/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,9 @@ pub use std::io;
pub use core2::io;

#[cfg(not(feature = "std"))]
mod io_extras {
#[doc(hidden)]
/// IO utilities public only for use by in-crate macros. These should not be used externally
pub mod io_extras {
use core2::io::{self, Read, Write};

/// A writer which will move data into the void.
Expand Down Expand Up @@ -154,6 +156,8 @@ mod io_extras {
}

#[cfg(feature = "std")]
#[doc(hidden)]
/// IO utilities public only for use by in-crate macros. These should not be used externally
mod io_extras {
pub fn read_to_end<D: ::std::io::Read>(mut d: D) -> Result<Vec<u8>, ::std::io::Error> {
let mut buf = Vec::new();
Expand Down
69 changes: 50 additions & 19 deletions lightning/src/util/ser_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -354,58 +354,78 @@ macro_rules! _check_missing_tlv {
#[doc(hidden)]
#[macro_export]
macro_rules! _decode_tlv {
($reader: expr, $field: ident, (default_value, $default: expr)) => {{
$crate::_decode_tlv!($reader, $field, required)
($outer_reader: expr, $reader: expr, $field: ident, (default_value, $default: expr)) => {{
$crate::_decode_tlv!($outer_reader, $reader, $field, required)
}};
($reader: expr, $field: ident, (static_value, $value: expr)) => {{
($outer_reader: expr, $reader: expr, $field: ident, (static_value, $value: expr)) => {{
}};
($reader: expr, $field: ident, required) => {{
($outer_reader: expr, $reader: expr, $field: ident, required) => {{
$field = $crate::util::ser::Readable::read(&mut $reader)?;
}};
($reader: expr, $field: ident, (required: $trait: ident $(, $read_arg: expr)?)) => {{
($outer_reader: expr, $reader: expr, $field: ident, (required: $trait: ident $(, $read_arg: expr)?)) => {{
$field = $trait::read(&mut $reader $(, $read_arg)*)?;
}};
($reader: expr, $field: ident, required_vec) => {{
($outer_reader: expr, $reader: expr, $field: ident, required_vec) => {{
let f: $crate::util::ser::WithoutLength<Vec<_>> = $crate::util::ser::Readable::read(&mut $reader)?;
$field = f.0;
}};
($reader: expr, $field: ident, option) => {{
($outer_reader: expr, $reader: expr, $field: ident, option) => {{
$field = Some($crate::util::ser::Readable::read(&mut $reader)?);
}};
($reader: expr, $field: ident, optional_vec) => {{
($outer_reader: expr, $reader: expr, $field: ident, optional_vec) => {{
let f: $crate::util::ser::WithoutLength<Vec<_>> = $crate::util::ser::Readable::read(&mut $reader)?;
$field = Some(f.0);
}};
// `upgradable_required` indicates we're reading a required TLV that may have been upgraded
// without backwards compat. We'll error if the field is missing, and return `Ok(None)` if the
// field is present but we can no longer understand it.
// Note that this variant can only be used within a `MaybeReadable` read.
($reader: expr, $field: ident, upgradable_required) => {{
($outer_reader: expr, $reader: expr, $field: ident, upgradable_required) => {{
$field = match $crate::util::ser::MaybeReadable::read(&mut $reader)? {
Some(res) => res,
_ => return Ok(None)
None => {
// If we successfully read a value but we don't know how to parse it, we give up
// and immediately return `None`. However, we need to make sure we read the correct
// number of bytes for this TLV stream, which is implicitly the end of the stream.
// Thus, we consume everything left in the `$outer_reader` here, ensuring that if
// we're being read as a part of another TLV stream we don't spuriously fail to
// deserialize the outer object due to a TLV length mismatch.
$crate::io_extras::copy($outer_reader, &mut $crate::io_extras::sink()).unwrap();
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Why do we use $crate::io_extras::copy but $reader.eat_remaining()? below?

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We're not reading the inner reader (which is always a LengthLimitingReader for just the specific TLV's value and thus supports eat_remaining()) but rather the outer reader, which may be of any type and thus we can't assume eat_remaining is available.

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Ah, I see. Makes sense.

return Ok(None)
},
};
}};
// `upgradable_option` indicates we're reading an Option-al TLV that may have been upgraded
// without backwards compat. $field will be None if the TLV is missing or if the field is present
// but we can no longer understand it.
($reader: expr, $field: ident, upgradable_option) => {{
($outer_reader: expr, $reader: expr, $field: ident, upgradable_option) => {{
$field = $crate::util::ser::MaybeReadable::read(&mut $reader)?;
if $field.is_none() {
#[cfg(not(debug_assertions))] {
// In general, MaybeReadable implementations are required to consume all the bytes
// of the object even if they don't understand it, but due to a bug in the
// serialization format for `impl_writeable_tlv_based_enum_upgradable` we sometimes
// don't know how many bytes that is. In such cases, we'd like to spuriously allow
// TLV length mismatches, which we do here by calling `eat_remaining` so that the
// `s.bytes_remain()` check in `_decode_tlv_stream_range` doesn't fail.
$reader.eat_remaining()?;
}
}
}};
($reader: expr, $field: ident, (option: $trait: ident $(, $read_arg: expr)?)) => {{
($outer_reader: expr, $reader: expr, $field: ident, (option: $trait: ident $(, $read_arg: expr)?)) => {{
$field = Some($trait::read(&mut $reader $(, $read_arg)*)?);
}};
($reader: expr, $field: ident, (option, encoding: ($fieldty: ty, $encoding: ident, $encoder:ty))) => {{
$crate::_decode_tlv!($reader, $field, (option, encoding: ($fieldty, $encoding)));
($outer_reader: expr, $reader: expr, $field: ident, (option, encoding: ($fieldty: ty, $encoding: ident, $encoder:ty))) => {{
$crate::_decode_tlv!($outer_reader, $reader, $field, (option, encoding: ($fieldty, $encoding)));
}};
($reader: expr, $field: ident, (option, encoding: ($fieldty: ty, $encoding: ident))) => {{
($outer_reader: expr, $reader: expr, $field: ident, (option, encoding: ($fieldty: ty, $encoding: ident))) => {{
$field = {
let field: $encoding<$fieldty> = ser::Readable::read(&mut $reader)?;
Some(field.0)
};
}};
($reader: expr, $field: ident, (option, encoding: $fieldty: ty)) => {{
$crate::_decode_tlv!($reader, $field, option);
($outer_reader: expr, $reader: expr, $field: ident, (option, encoding: $fieldty: ty)) => {{
$crate::_decode_tlv!($outer_reader, $reader, $field, option);
}};
}

Expand Down Expand Up @@ -539,7 +559,7 @@ macro_rules! _decode_tlv_stream_range {
let mut s = ser::FixedLengthReader::new(&mut stream_ref, length.0);
match typ.0 {
$(_t if $crate::_decode_tlv_stream_match_check!(_t, $type, $fieldty) => {
$crate::_decode_tlv!(s, $field, $fieldty);
$crate::_decode_tlv!($stream, s, $field, $fieldty);
if s.bytes_remain() {
s.eat_remaining()?; // Return ShortRead if there's actually not enough bytes
return Err(DecodeError::InvalidValue);
Expand Down Expand Up @@ -1065,6 +1085,10 @@ macro_rules! impl_writeable_tlv_based_enum {
/// when [`MaybeReadable`] is practical instead of just [`Readable`] as it provides an upgrade path for
/// new variants to be added which are simply ignored by existing clients.
///
/// Note that only struct and unit variants (not tuple variants) will support downgrading, thus any
/// new odd variants MUST be non-tuple (i.e. described using `$variant_id` and `$variant_name` not
/// `$tuple_variant_id` and `$tuple_variant_name`).
///
/// [`MaybeReadable`]: crate::util::ser::MaybeReadable
/// [`Writeable`]: crate::util::ser::Writeable
/// [`DecodeError::UnknownRequiredFeature`]: crate::ln::msgs::DecodeError::UnknownRequiredFeature
Expand Down Expand Up @@ -1102,7 +1126,14 @@ macro_rules! impl_writeable_tlv_based_enum_upgradable {
$($($tuple_variant_id => {
Ok(Some($st::$tuple_variant_name(Readable::read(reader)?)))
}),*)*
_ if id % 2 == 1 => Ok(None),
_ if id % 2 == 1 => {
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// Assume that a $variant_id was written, not a $tuple_variant_id, and read
// the length prefix and discard the correct number of bytes.
let tlv_len: $crate::util::ser::BigSize = $crate::util::ser::Readable::read(reader)?;
let mut rd = $crate::util::ser::FixedLengthReader::new(reader, tlv_len.0);
rd.eat_remaining().map_err(|_| $crate::ln::msgs::DecodeError::ShortRead)?;
Ok(None)
},
_ => Err($crate::ln::msgs::DecodeError::UnknownRequiredFeature),
}
}
Expand Down