Merge #20405: p2p: avoid calculating onion address checksum when vers…

…ion is not 3

d355a30 Break circuit earlier (lontivero)

Pull request description:

  Currently when parsing an onion v3 address the pubic key checksum is calculated in order to compare it with the received address checksum. However this step is not necessary if the address version byte is not 3, in which case the method can return with false immediately.

ACKs for top commit:
  jonatack:
    ACK d355a30
  practicalswift:
    ACK d355a30 -- patch looks correct
  hebasto:
    ACK d355a30, I have reviewed the code and it looks OK, I agree it can be merged.
  sipa:
    utACK d355a30

Tree-SHA512: 9e4506793b7f4a62ce8edc41a260a8c125ae81ed2f90cd850eb2a9214d323c446edc7586c7b0590dcbf3aed5be534718b77bb19c45b48f8f52553d32a3663a65

src/netaddress.cpp

@@ -255,10 +255,14 @@ bool CNetAddr::SetSpecial(const std::string& str)
         Span<const uint8_t> input_checksum{input.data() + ADDR_TORV3_SIZE, torv3::CHECKSUM_LEN};
         Span<const uint8_t> input_version{input.data() + ADDR_TORV3_SIZE + torv3::CHECKSUM_LEN, sizeof(torv3::VERSION)};
 
+        if (input_version != torv3::VERSION) {
+            return false;
+        }
+
         uint8_t calculated_checksum[torv3::CHECKSUM_LEN];
         torv3::Checksum(input_pubkey, calculated_checksum);
 
-        if (input_checksum != calculated_checksum || input_version != torv3::VERSION) {
+        if (input_checksum != calculated_checksum) {
             return false;
         }