add PKCS1 and PKCS8 support for pem files (#2)

Code of both `createPrivateKeyFromPemPkcs*` methods is copied from
http://magnus-k-karlsson.blogspot.com/2018/05/how-to-read-pem-pkcs1-or-pkcs8-encoded.html.

Note: It was permitted to use the code by Magnus via email on 4th
February 2020 11:29am CET. Additinally he asked for adding him as
co-writer. Therefore I committed this code using Magnus as author.
Thanks for allowing this!

Signed-off-by: Magnus Karlsson <[email protected]>

Author: magnuskkarlsson

build.gradle.kts

@@ -53,7 +53,7 @@ dependencies {
 tasks {
     withType<JavaCompile> {
         options.encoding = "UTF-8"
-        options.compilerArgs.addAll(listOf("-Xlint:all", "-Werror", "-Xlint:-processing"))
+        options.compilerArgs.addAll(listOf("-Xlint:all", "-Werror", "-Xlint:-processing", "-XDenableSunApiLintControl"))
     }
 
     withType<Jar> {

src/main/java/de/aaschmid/taskwarrior/client/KeyStoreBuilder.java

@@ -4,6 +4,7 @@
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
+import java.math.BigInteger;
 import java.nio.file.Files;
 import java.security.KeyFactory;
 import java.security.KeyStore;
@@ -19,7 +20,9 @@
 import java.security.spec.InvalidKeySpecException;
 import java.security.spec.KeySpec;
 import java.security.spec.PKCS8EncodedKeySpec;
+import java.security.spec.RSAPrivateCrtKeySpec;
 import java.util.ArrayList;
+import java.util.Base64;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -135,6 +138,35 @@ private PrivateKey createPrivateKeyFor(File privateKeyFile) {
         }
     }
 
+    @SuppressWarnings("sunapi")
+    private PrivateKey createPrivateKeyFromPemPkcs1(String privateKeyContent) throws IOException {
+        try {
+            byte[] bytes = Base64.getDecoder().decode(privateKeyContent);
+
+            sun.security.util.DerInputStream derReader = new sun.security.util.DerInputStream(bytes);
+            sun.security.util.DerValue[] seq = derReader.getSequence(0);
+            // skip version seq[0];
+            BigInteger modulus = seq[1].getBigInteger();
+            BigInteger publicExp = seq[2].getBigInteger();
+            BigInteger privateExp = seq[3].getBigInteger();
+            BigInteger prime1 = seq[4].getBigInteger();
+            BigInteger prime2 = seq[5].getBigInteger();
+            BigInteger exp1 = seq[6].getBigInteger();
+            BigInteger exp2 = seq[7].getBigInteger();
+            BigInteger crtCoef = seq[8].getBigInteger();
+
+            RSAPrivateCrtKeySpec keySpec = new RSAPrivateCrtKeySpec(modulus, publicExp, privateExp, prime1, prime2, exp1, exp2, crtCoef);
+            return createPrivateKey(privateKeyFile, keySpec);
+        } catch (Error | Exception e) {
+            throw new TaskwarriorKeyStoreException("Could not use required but proprietary 'sun.security.util' package on this platform.", e);
+        }
+    }
+
+    private PrivateKey createPrivateKeyFromPemPkcs8(String privateKeyContent) {
+        byte[] bytes = Base64.getDecoder().decode(privateKeyContent);
+        return createPrivateKey(privateKeyFile, new PKCS8EncodedKeySpec(bytes));
+    }
+
     private PrivateKey createPrivateKeyFromPkcs8Der(byte[] privateKeyBytes) {
         return createPrivateKey(privateKeyFile, new PKCS8EncodedKeySpec(privateKeyBytes));
     }