[UB] Access out-of-bounds data when parsing invalid metadata items

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
cpp
Domain
tooling

Research direction

Inspect bintool/metadata.h around the linked lines, starting with how metadata item lengths are validated before the parser accesses data[i+1]. Exercise the parser with an invalid metadata item and confirm that it no longer performs an out-of-bounds access; the issue does not identify a test file.

Written by the indexing model from the issue text.

Description

This code effectively accesses the data at i and at i+1:

https://github.com/raspberrypi/picotool/blob/de8ae5ac334e1126993f72a5c67949712fd1e1a4/bintool/metadata.h#L257-L261

However, the code does not ensure that data[1] will be valid:

https://github.com/raspberrypi/picotool/blob/de8ae5ac334e1126993f72a5c67949712fd1e1a4/bintool/metadata.h#L237-L242

From https://en.cppreference.com/w/cpp/container/vector/operator_at:

No bounds checking is performed.

Therefore, no guarantee that this will throw an exception (which might be expected), and as a result, clearly getting into undefined behavior.....

Dominant language
C++
Stars
999
Forks
189
No merged PRs in 30d

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