Do not execute the default_value expr until we need it in TLV deser #1588
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jkczyz
previously approved these changes
Jul 1, 2022
Codecov Report
@@ Coverage Diff @@
## main #1588 +/- ##
==========================================
- Coverage 91.07% 91.02% -0.05%
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Files 80 80
Lines 44128 44125 -3
Branches 44128 44125 -3
==========================================
- Hits 40190 40166 -24
- Misses 3938 3959 +21
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jkczyz
previously approved these changes
Jul 5, 2022
wpaulino
previously approved these changes
Jul 5, 2022
This fixes an insta-panic in `ChannelMonitor` deserialization where we always `unwrap` a previous value to determine the default value of a later field. However, because we always ran the `unwrap` before the previous field is read, we'd always panic. The fix is rather simple - use a `OptionDeserWrapper` for `default_value` fields and only fill in the default value if no value was read while walking the TLV stream. The only complexity comes from our desire to support `read_tlv_field` calls that use an explicit field rather than an `Option` of some sort, which requires some statement which can assign both an `OptionDeserWrapper<T>` variable and a `T` variable. We settle on `x = t.into()` and implement `From<T> for OptionDeserWrapper<T>` which works, though it requires users to specify types explicitly due to Rust determining expression types prior to macro execution, completely guessing with no knowlege for integer expressions (see rust-lang/rust#91369).
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wpaulino
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Jul 5, 2022
jkczyz
approved these changes
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This fixes an insta-panic in
ChannelMonitordeserialization wherewe always
unwrapa previous value to determine the default valueof a later field. However, because we always ran the
unwrapbefore the previous field is read, we'd always panic.
The fix is rather simple - use a
OptionDeserWrapperfordefault_valuefields and only fill in the default value if novalue was read while walking the TLV stream.
The only complexity comes from our desire to support
read_tlv_fieldcalls that use an explicit field rather than anOptionof some sort, which requires some statement which canassign both an
OptionDeserWrapper<T>variable and aTvariable.We settle on
x = t.into()and implementFrom<T> for OptionDeserWrapper<T>which works, though it requires users tospecify types explicitly due to Rust determining expression types
prior to macro execution, completely guessing with no knowlege for
integer expressions (see
rust-lang/rust#91369).
In lieu of an explicit and overly-restrictive test, we opt instead for a new fuzzer, which should exercise this code much better.