(WIP) tlshook: Support non-dehydrated certificates.

tlshook/tlshook.go

@@ -43,7 +43,74 @@ func DomainValueHookTLS(qname string, ncv *ncdomain.Value) (err error) {
 
 			}
 
-			// TODO: support non-dehydrated certificates
+			// For non-dehydrated certificates
+			// TODO: test this code.
+			//       since this code has not been tested yet, it's disabled for safety reasons.
+			//if len(port.TLSA) > 0 {
+			if false {
+
+				log.Info("Just saw a TLS port 443 capable domain request for ", qname, "!")
+
+				for index, cert := range port.TLSA {
+
+					// cert usage 3 is end-entity cert that need not pass CA-based validation
+					// cert selector 0 is a full certificate (not just public key)
+					// cert matching type 0 is exact match (not hashed)
+					if cert.Usage == 3 && cert.Selector == 0 && cert.MatchingType == 0 {
+
+						log.Info("Certificate # ", index, " is usable with hex value ", cert.Certificate)
+
+						origCertBytes, err:= hex.DecodeString(cert.Certificate)
+						if err != nil {
+							log.Info("Failed to decode hex string of TLSA certificate, ", err)
+							continue
+						}
+
+						origCert, err := x509.ParseCertificate(origCertBytes)
+						if err != nil {
+							log.Info("Failed to parse TLSA certificate, ", err)
+							continue
+						}
+
+						// TODO: look into being a bit more flexible with cert serial number, validity period, and subject serial number.
+						//       The uniformity in those fields is due to compression rather than security concerns.
+						//       So we could possibly pass those through in cases like this.
+						//       Subject serial number is also there due to transparency concerns, so maybe don't allow customizing it.
+
+						dehydrated, err := certdehydrate.DehydrateCert(origCert)
+						if err != nil {
+							log.Info("Failed to dehydrate TLSA certificate, ", err)
+							continue
+						}
+
+						rehydrated, err := certdehydrate.RehydrateCert(dehydrated)
+						if err != nil {
+							log.Info("Failed to rehydrate TLSA certificate, ", err)
+							continue
+						}
+
+						rehydratedDerBytes, err := certdehydrate.FillRehydratedCertTemplate(*rehydrated, qname)
+						if err != nil {
+							log.Info("Failed to fill rehydrated TLSA certificate, ", err)
+							continue
+						}
+
+						if ! bytes.Equal(origCertBytes, rehydratedDerBytes) {
+							log.Info("TLSA certificate didn't conform to dehydration template; skipping certificate.")
+							continue
+						}
+
+						// TODO: check return value
+						certinject.InjectCert(rehydratedDerBytes)
+
+					} else {
+
+						log.Info("Certificate # ", index, " is not usable because we cannot recover the full end-entity certificate from the TLSA record.")
+
+					}
+
+				}
+			}
 		}
 	}