fix: accept loopback addresses for DoH and add IP SANs to TLS cert

The DoH endpoint rejected requests with Host: 127.0.0.1/::1/localhost,
and the generated TLS cert had no IP SANs — so browsers couldn't use
https://127.0.0.1/dns-query even with the CA trusted.

- is_doh_host now accepts 127.0.0.1, ::1, localhost (with optional port)
- TLS cert includes 127.0.0.1 and ::1 IP SANs, plus bare TLD DNS SAN

Closes #87

src/doh.rs

@@ -49,16 +49,25 @@ pub async fn doh_post(State(state): State<super::proxy::DohState>, req: Request)
 }
 
 fn is_doh_host(host: Option<&str>, tld: &str) -> bool {
-    match host {
-        Some(h) if h == tld => true,
-        Some(h) => {
-            h.len() == 2 * tld.len() + 1
+    let h = match host {
+        Some(h) => h,
+        None => return false,
+    };
+    is_doh_name(h, tld)
+        || h.rsplit_once(':').is_some_and(|(base, port)| {
+            port.bytes().all(|b| b.is_ascii_digit()) && is_doh_name(base, tld)
+        })
+}
+
+fn is_doh_name(h: &str, tld: &str) -> bool {
+    h == tld
+        || (h.len() == 2 * tld.len() + 1
             && h.starts_with(tld)
             && h.as_bytes().get(tld.len()) == Some(&b'.')
-                && h.ends_with(tld)
-        }
-        None => false,
-    }
+            && h.ends_with(tld))
+        || h == "127.0.0.1"
+        || h == "::1"
+        || h == "localhost"
 }
 
 async fn resolve_doh(
@@ -148,6 +157,10 @@ mod tests {
     fn is_doh_host_matches_tld() {
         assert!(is_doh_host(Some("numa"), "numa"));
         assert!(is_doh_host(Some("numa.numa"), "numa"));
+        assert!(is_doh_host(Some("127.0.0.1"), "numa"));
+        assert!(is_doh_host(Some("127.0.0.1:443"), "numa"));
+        assert!(is_doh_host(Some("::1"), "numa"));
+        assert!(is_doh_host(Some("localhost"), "numa"));
         assert!(!is_doh_host(Some("foo.numa"), "numa"));
         assert!(!is_doh_host(None, "numa"));
     }

src/tls.rs

@@ -186,6 +186,20 @@ fn generate_service_cert(
         }
     }
 
+    // Loopback IP SANs so browsers can reach DoH at https://127.0.0.1/dns-query
+    sans.push(SanType::IpAddress(std::net::IpAddr::V4(
+        std::net::Ipv4Addr::LOCALHOST,
+    )));
+    sans.push(SanType::IpAddress(std::net::IpAddr::V6(
+        std::net::Ipv6Addr::LOCALHOST,
+    )));
+
+    // Bare TLD (e.g. "numa") for DoH via https://numa/dns-query
+    match tld.to_string().try_into() {
+        Ok(ia5) => sans.push(SanType::DnsName(ia5)),
+        Err(e) => warn!("invalid SAN {}: {}", tld, e),
+    }
+
     if sans.is_empty() {
         return Err("no valid service names for TLS cert".into());
     }