socks: Make SafeSocks refuse SOCKS4 and accept SOCKS4a

The logic was inverted. Introduced in commit
9155e084.

This was reported through our bug bounty program on H1. It fixes the
TROVE-2022-002.

Fixes #40730

Signed-off-by: David Goulet <dgoulet@torproject.org>

changes/ticket40730

+  o Major bugfixes (TROVE-2022-002, client):
+    - The SafeSocks option had its logic inverted for SOCKS4 and SOCKS4a. It
+      would let the unsafe SOCKS4 pass but not the safe SOCKS4a one. This is
+      TROVE-2022-002 which was reported on Hackerone by "cojabo". Fixes bug
+      40730; bugfix on 0.3.5.1-alpha.

src/core/proto/proto_socks.c

@@ -233,7 +233,7 @@ static socks_result_t
 process_socks4_request(const socks_request_t *req, int is_socks4a,
                        int log_sockstype, int safe_socks)
 {
-  if (is_socks4a && !addressmap_have_mapping(req->address, 0)) {
+  if (!is_socks4a && !addressmap_have_mapping(req->address, 0)) {
     log_unsafe_socks_warning(4, req->address, req->port, safe_socks);
 
     if (safe_socks)