eof: fix multi-container-section case

[pdobacz]

Credit to @chfast to find the case via fuzzing, as well as suggest this version of the fix (alternative version in comment, not sure which is cleaner anymore)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.29%. Comparing base (85ded61) to head (0855eb1).
Report is 1 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@ ## master #978 +/- ## ======================================= Coverage 94.29% 94.29% ======================================= Files 143 143 Lines 16145 16148 +3 ======================================= + Hits 15224 15227 +3  Misses 921 921 

Flag	Coverage Δ
eof_execution_spec_tests	16.67% <66.66%> (+<0.01%)	⬆️
ethereum_tests	26.91% <66.66%> (+<0.01%)	⬆️
ethereum_tests_silkpre	18.67% <0.00%> (-0.01%)	⬇️
execution_spec_tests	17.71% <0.00%> (-0.01%)	⬇️
unittests	89.74% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
lib/evmone/eof.cpp	85.68% <100.00%> (+0.02%)	⬆️
test/unittests/eof_validation_test.cpp	99.36% <100.00%> (+<0.01%)	⬆️

[chfast]

Let me try one more thing here.

[chfast]

I pushed an alternative fix where we check id != expected twice but the helper get_section_missing_error() remains sane.

[chfast]

This issue was found indirectly by fuzzing: I was debugging the fuzzer mutation and noticed this weird EOF header. This indicates this validation issue may not be exploitable. Yet, it is a serious bug.