Sanitize upload path traversal
Sanitize an untrusted upload path so it cannot escape a base directory. Given a base directory like '/srv/uploads' and an untrusted relative path (which may contain '..', '.', leading slashes, or empty segments), resolve it WITHOUT touching the filesystem: split on '/', drop '.' and empty segments, and for each '..' pop the last accumulated segment (never popping above the base). Return the joined absolute path as base + '/' + the safe remainder. If the remainder is empty, return the base unchanged.
Implement
safe_join(base: str, untrusted: str) → strExamples
in
["/srv/uploads","a/b/c.txt"]out"/srv/uploads/a/b/c.txt"What a strong answer looks like
State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
0:00 of about 25 min
solution.py
InputExpectedGot
["/srv/uploads","a/b/c.txt"]"/srv/uploads/a/b/c.txt"not run yetsample