From 1980072d12a32c58f4c0a51ceab784afa0e48a96 Mon Sep 17 00:00:00 2001
From: Vladimir Lagunov <vladimir.lagunov@jetbrains.com>
Date: Wed, 16 Mar 2022 14:02:40 +0700
Subject: [PATCH] Throw IOE instead of NPE if OpenSSHKeyV1KeyFile reads an
 empty file

There is a contract that FileKeyProvider.readKey throws an IOException if something goes wrong. Throwing an NPE is not expected by API users. Also, it is much more difficult to find out if the NPE is thrown due to a broken key file, or due to an internal bug.
---
 .../sshj/userauth/keyprovider/OpenSSHKeyV1KeyFile.java   | 3 +++
 .../net/schmizz/sshj/keyprovider/OpenSSHKeyFileTest.java | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/src/main/java/com/hierynomus/sshj/userauth/keyprovider/OpenSSHKeyV1KeyFile.java b/src/main/java/com/hierynomus/sshj/userauth/keyprovider/OpenSSHKeyV1KeyFile.java
index 15348bac..a9d6eb55 100644
--- a/src/main/java/com/hierynomus/sshj/userauth/keyprovider/OpenSSHKeyV1KeyFile.java
+++ b/src/main/java/com/hierynomus/sshj/userauth/keyprovider/OpenSSHKeyV1KeyFile.java
@@ -218,6 +218,9 @@ private boolean checkHeader(final BufferedReader reader) throws IOException {
         while (line != null && !line.startsWith(BEGIN)) {
             line = reader.readLine();
         }
+        if (line == null) {
+            return false;
+        }
         line = line.substring(BEGIN.length());
         return line.startsWith(OPENSSH_PRIVATE_KEY);
     }
diff --git a/src/test/java/net/schmizz/sshj/keyprovider/OpenSSHKeyFileTest.java b/src/test/java/net/schmizz/sshj/keyprovider/OpenSSHKeyFileTest.java
index d406198c..3ebfe164 100644
--- a/src/test/java/net/schmizz/sshj/keyprovider/OpenSSHKeyFileTest.java
+++ b/src/test/java/net/schmizz/sshj/keyprovider/OpenSSHKeyFileTest.java
@@ -39,6 +39,7 @@
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
+import java.io.StringReader;
 import java.math.BigInteger;
 import java.security.GeneralSecurityException;
 import java.security.PrivateKey;
@@ -443,6 +444,14 @@ public void notTrimmedKeys() throws IOException {
                      corruptedKeyFile.getPublic());
     }
 
+    @Test
+    public void emptyPrivateKey() {
+        FileKeyProvider keyProvider = new OpenSSHKeyV1KeyFile();
+        keyProvider.init(new StringReader(""));
+
+        assertThrows("This key is not in 'openssh-key-v1' format", IOException.class, keyProvider::getPrivate);
+    }
+
     @Before
     public void checkBCRegistration() {
         if (!SecurityUtils.isBouncyCastleRegistered()) {