explicitly check for assumptions in api/dns.rs

[anonrig]

No description provided.

[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

This PR adds bounds checks to parse_caa_record and parse_naptr_record to convert panics from out-of-bounds slice indexing into proper Err returns. Since panics across CXX abort the process, this is a good hardening change.

Issues (by severity):

1. Medium: parse_replacement has the same class of bug. The function at line 95 does input[offset_index..length + offset_index] where length is parsed from untrusted hex input. A malicious or malformed length value will cause a panic. Since parse_replacement is called from parse_naptr_record (line 264), this is reachable from JS via the same path. The same hardening applied in this PR should be extended there:

   if length + offset_index > input.len() {
       return Err(DnsParserError::InvalidDnsResponse(
           "replacement data too short for declared frame length".to_owned(),
       ));
   }
   let subset = input[offset_index..length + offset_index].to_vec();

2. Low: Redundant check in parse_caa_record. The data.len() < 2 check on line 154 is technically always true when parts.len() == 3 (since the first guard already ensured parts.len() >= 3, and data = parts[2..]). This is defensible as defense-in-depth, so just flagging for awareness — no action needed.

[ask-bonk]

Review posted successfully on PR #6311. Here's a summary of what I found:

1 actionable issue:

• Medium severity: parse_replacement (line 95) has the exact same unchecked slice indexing vulnerability that this PR fixes in the other two functions. A malformed length value parsed from untrusted hex input can cause a panic, which aborts across CXX. Since parse_replacement is called from parse_naptr_record, this is reachable from JS. I suggested the same bounds-check pattern be applied there.

1 informational note:

• The data.len() < 2 check in parse_caa_record is logically redundant given the earlier parts.len() < 3 guard, but it's fine as defense-in-depth.

github run

[tewaro]

Lgtm