Harden lightElf::Elf::getSectionHeader against malformed ELF headers

[Metastarx]

Summary

Running a bundle executes the packaged uab-header, which parses the ELF trailer of the running file itself, so every field of that ELF header is controlled by whoever produced the bundle. getSectionHeader() trusted e_shentsize and sh_name directly: it read e_shentsize bytes into a fixed SectionHeader on the stack, so a value larger than the struct overflowed it, and it built a string_view from an unchecked sh_name, so an offset outside the section-name string table scanned memory past the buffer. The section header table bounds were not validated either. The fix requires e_shentsize to match sizeof(SectionHeader), checks that e_shoff plus e_shnum entries lie inside the file, always reads exactly one SectionHeader, and resolves sh_name through a lookup that validates the offset and requires a NUL terminator, skipping malformed entries instead of dereferencing them.

Verification

ctest --test-dir build-release --output-on-failure - passed (100% tests passed, 0 tests failed out of 751)

Checklist

• I ran the verification described above
• The change is minimal and includes no unrelated files
• The repository contribution guidelines were followed

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.