GH-155: Delegate opening mTLS cert files to build()

Author: rtadepalli

flight/flight-core/src/main/java/org/apache/arrow/flight/FlightServer.java

@@ -190,9 +190,18 @@ public static final class Builder {
     private int maxInboundMessageSize = MAX_GRPC_MESSAGE_SIZE;
     private int maxHeaderListSize = MAX_GRPC_MESSAGE_SIZE;
     private int backpressureThreshold = DEFAULT_BACKPRESSURE_THRESHOLD;
+
+    /*
+    TODO: Remove certChain/key/mTlsCACert as instance vars and make them local vars in build() after they are
+    no longer being set in the builder methods.
+     */
+    private File certChainFile;
     private InputStream certChain;
+    private File keyFile;
     private InputStream key;
+    private File mTlsCACertFile;
     private InputStream mTlsCACert;
+
     private SslContext sslContext;
     private final List<KeyFactory<?>> interceptors;
     // Keep track of inserted interceptors
@@ -213,6 +222,16 @@ public static final class Builder {
 
     /** Create the server for this builder. */
     public FlightServer build() {
+      // Get TLS info in order if the server is being configured to use mTLS.
+      try {
+        prepareTlsSettings();
+      } catch (IOException e) {
+        closeMTlsCACert();
+        closeCertChain();
+        closeKey();
+        throw new RuntimeException("Could not create FlightServer with mTLS", e);
+      }
+
       // Add the auth middleware if applicable.
       if (headerAuthenticator != CallHeaderAuthenticator.NO_OP) {
         this.middleware(
@@ -442,11 +461,8 @@ private void closeMTlsCACert() {
      * @param key The private key to use.
      */
     public Builder useTls(final File certChain, final File key) throws IOException {
-      closeCertChain();
-      this.certChain = new FileInputStream(certChain);
-
-      closeKey();
-      this.key = new FileInputStream(key);
+      this.certChainFile = certChain;
+      this.keyFile = key;
 
       return this;
     }
@@ -457,8 +473,8 @@ public Builder useTls(final File certChain, final File key) throws IOException {
      * @param mTlsCACert The CA certificate to use for verifying clients.
      */
     public Builder useMTlsClientVerification(final File mTlsCACert) throws IOException {
-      closeMTlsCACert();
-      this.mTlsCACert = new FileInputStream(mTlsCACert);
+      this.mTlsCACertFile = mTlsCACert;
+
       return this;
     }
 
@@ -468,6 +484,7 @@ public Builder useMTlsClientVerification(final File mTlsCACert) throws IOExcepti
      * @param certChain The certificate chain to use.
      * @param key The private key to use.
      */
+    @Deprecated(forRemoval = true, since = "18.4.0")
     public Builder useTls(final InputStream certChain, final InputStream key) throws IOException {
       closeCertChain();
       this.certChain = certChain;
@@ -483,6 +500,7 @@ public Builder useTls(final InputStream certChain, final InputStream key) throws
      *
      * @param mTlsCACert The CA certificate to use for verifying clients.
      */
+    @Deprecated(forRemoval = true, since = "18.4.0")
     public Builder useMTlsClientVerification(final InputStream mTlsCACert) throws IOException {
       closeMTlsCACert();
       this.mTlsCACert = mTlsCACert;
@@ -552,5 +570,20 @@ public Builder producer(FlightProducer producer) {
       this.producer = Preconditions.checkNotNull(producer);
       return this;
     }
+
+    private void prepareTlsSettings() throws IOException {
+      if (this.keyFile != null) {
+        closeKey();
+        this.key = new FileInputStream(this.keyFile);
+      }
+      if (this.certChainFile != null) {
+        closeCertChain();
+        this.certChain = new FileInputStream(this.certChainFile);
+      }
+      if (this.mTlsCACertFile != null) {
+        closeMTlsCACert();
+        this.mTlsCACert = new FileInputStream(this.mTlsCACertFile);
+      }
+    }
   }
 }