config: reject hostnames whose last label is too long

`valid_domain()` measured a label when it found the terminating dot, so the last one was never checked and `1.2.3.4 test.<64 characters>` passed. dnsmasq rejects labels above 63 characters, so with `dns.hostsLocal` such an entry produced a `local=` line that makes the resolver refuse to start.

Signed-off-by: DL6ER <dl6er@dl6er.de>

Author: DL6ER

src/tools/gravity-parseList.c

@@ -98,6 +98,11 @@ inline bool __attribute__((pure)) valid_domain(const char *domain, const size_t
 
 	// TLD checks
 
+	// The last label is not followed by a dot, so the loop above never
+	// checked its length
+	if(len - (size_t)(last_dot + 1) > 63)
+		return false;
+
 	// There must be at least two labels (i.e. one dot)
 	// e.g., "example.com" but not "localhost" for exact domain
 	// We do not enforce this for ABP domains and domainlist input

test/test_suite.bats

@@ -1630,6 +1630,12 @@ setup() {
   assert_line --index 0 'Invalid value: dns.hosts[2]: entry does not have at least one hostname ("1.2.3.4")'
   assert_failure 3
 
+  # The final label is subject to the 63 character limit as well
+  long_label="$(printf 'a%.0s' {1..64})"
+  run bash -c "./pihole-FTL --config dns.hosts '[\"1.2.3.4 test.${long_label}\"]'"
+  assert_line --index 0 "Invalid value: dns.hosts[0]: invalid hostname (\"test.${long_label}\")"
+  assert_failure 3
+
   run bash -c './pihole-FTL --config dns.revServers "[\"abc,def,ghi\"]"'
   assert_line --index 0 'Invalid value: dns.revServers[0]: <enabled> not a boolean ("abc")'
   assert_failure 3