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Marius CiepluchandClaude Opus 5
9221ba8e40
contributor-scan 2.12. c/injection and c/memory carried zero sanitizers, so no C flow could ever be discharged: every `argv -> strcpy` entailed however carefully it was bounded. Which sinks can be discharged this way is read from the sink fact's own CWE rather than declared: CWE-121 is a stack buffer overflow, so gets/sprintf/strcat/strcpy qualify. It is the only overflow CWE in the fact tables and it is C-only, so no Python or JavaScript sink is touched and the pair corpus is unaffected -- gates byte-identical. Not a sanitizer list, because `strlen` appears in the guarded and the unguarded case alike; the discharge is a guard, not a call. **The first implementation required the bound to DOMINATE the sink, and it found nothing.** libpng guards `strcpy(outname+len, ".png")` with `(len = strlen(inname)) > 250`, but that check sits on an else-if chain whose sibling branch skips it entirely, and the protection reaches the sink through an `error` flag: `++error` in the guarded branch, `if (!error)` around the copy. Joern's dominator set for that sink has 89 calls and correctly excludes the bound; `controlledBy` returns none either. Verified against the CPG before the rule was changed rather than after it failed. So the bound is searched in the method, and the consequence is corroborated rather than silence. That is the honest rung: a bound on this variable means the graph has NOT shown the copy is unguarded, and it has not shown it is guarded either -- off-by-one being how bounds fail. The judge is asked. Proving the flag-mediated case needs path-sensitive reasoning this arbiter does not do. libpng entailed 3 -> 1 The survivor is also a false positive: `strcpy(output + len, ".icc")` in iccfrompng.c, where `output = malloc(len + 5)` makes it fit exactly. That is a different discharge shape -- allocated to size, not bounds-checked -- and it is recorded as 2.13 rather than chased. Both shapes were found on one repository, and extending a rule until that repository is clean is the overfitting Req 8 exists to prevent; 2.13 requires a second C checkout with a genuine CWE-121 so the change can be measured for what it silences as well as what it clears. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]> Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG