Added SSL fix (since I'm not sure letsencryptcraft has a liteloader version)

src/hdskins/java/com/voxelmodpack/hdskins/LiteModHDSkins.java

@@ -17,6 +17,7 @@ import com.voxelmodpack.hdskins.gui.HDSkinsConfigPanel;
 import com.voxelmodpack.hdskins.gui.RenderPlayerModel;
 import com.voxelmodpack.hdskins.server.*;
 import com.voxelmodpack.hdskins.upload.GLWindow;
+import com.voxelmodpack.hdskins.util.SslHelper;
 
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.gui.ScaledResolution;
@@ -46,6 +47,9 @@ public class LiteModHDSkins implements InitCompleteListener, ViewportListener, C
     @Expose
     public String lastChosenFile = "";
 
+    @Expose
+    public boolean skipLetsEncrypt = false;
+
     public LiteModHDSkins() {
         instance = this;
     }
@@ -72,6 +76,10 @@ public class LiteModHDSkins implements InitCompleteListener, ViewportListener, C
 
         IReloadableResourceManager irrm = (IReloadableResourceManager) Minecraft.getMinecraft().getResourceManager();
         irrm.registerReloadListener(HDSkinManager.INSTANCE);
+
+        if (!skipLetsEncrypt) {
+            SslHelper.doStuff(HDSkinManager.logger);
+        }
     }
 
     @Override

src/hdskins/java/com/voxelmodpack/hdskins/server/ValhallaSkinServer.java

@@ -36,6 +36,9 @@ public class ValhallaSkinServer implements SkinServer {
     private transient String accessToken;
 
     public ValhallaSkinServer(String address) {
+        if (address.startsWith("http:")) {
+            address = address.replace("http:", "https:");
+        }
         this.address = address;
     }
 

src/hdskins/java/com/voxelmodpack/hdskins/util/SslHelper.java

@@ -0,0 +1,101 @@
+package com.voxelmodpack.hdskins.util;
+
+import java.io.*;
+import java.net.URL;
+import java.net.URLConnection;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.*;
+import java.security.KeyStore;
+import java.security.cert.Certificate;
+import java.security.cert.CertificateFactory;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import javax.net.ssl.SSLContext;
+import javax.net.ssl.TrustManagerFactory;
+
+import org.apache.logging.log4j.Logger;
+
+/**
+ * Credit to https://github.com/Cloudhunter/LetsEncryptCraft
+ */
+public class SslHelper {
+
+    public static void addLetsEncryptCertificate() throws Exception {
+        InputStream cert = SslHelper.class.getResourceAsStream("lets-encrypt-x3-cross-signed.der");
+
+        KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
+        Path ksPath = Paths.get(System.getProperty("java.home"),"lib", "security", "cacerts");
+        keyStore.load(Files.newInputStream(ksPath), "changeit".toCharArray());
+
+        CertificateFactory cf = CertificateFactory.getInstance("X.509");
+
+        InputStream caInput = new BufferedInputStream(cert);
+        Certificate crt = cf.generateCertificate(caInput);
+
+        keyStore.setCertificateEntry("lets-encrypt-x3-cross-signed", crt);
+
+        TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
+        tmf.init(keyStore);
+        SSLContext sslContext = SSLContext.getInstance("TLS");
+        sslContext.init(null, tmf.getTrustManagers(), null);
+        SSLContext.setDefault(sslContext);
+    }
+
+    public static void doStuff(Logger mod) {
+        String version = System.getProperty("java.version");
+        Pattern p = Pattern.compile("^(\\d+\\.\\d+).*?_(\\d+).*");
+        Matcher matcher = p.matcher(version);
+        String majorVersion;
+        int minorVersion;
+        if (matcher.matches())
+        {
+            majorVersion = matcher.group(1);
+            minorVersion = Integer.valueOf(matcher.group(2));
+        } else {
+            majorVersion = "1.7";
+            minorVersion = 110;
+            mod.info("Regex to parse Java version failed - applying LetsEncrypt anyway.");
+        }
+
+        switch (majorVersion)
+        {
+            case "1.7":
+                if (minorVersion >= 111)
+                {
+                    mod.info("LetsEncrypt is not needed as Java version is at least Java 7u111.");
+                    return;
+                }
+                break;
+            case "1.8":
+                if (minorVersion >= 101)
+                {
+                    mod.info("LetsEncrypt is not needed as Java version is at least Java 8u101.");
+                    return;
+                }
+                break;
+        }
+
+        String body = "";
+        try {
+            mod.info("Adding Let's Encrypt certificate...");
+            addLetsEncryptCertificate();
+            mod.info("Done, attempting to connect to https://helloworld.letsencrypt.org...");
+            URL url = new URL("https://helloworld.letsencrypt.org");
+            URLConnection conn = url.openConnection();
+            conn.setConnectTimeout(5000);
+            conn.setReadTimeout(5000);
+            try (BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8))) {
+                body = reader.readLine();
+            }
+        } catch (Exception e) {
+            mod.error("An error occurred whilst adding the Let's Encrypt root certificate. I'm afraid you wont be able to access resources with a Let's Encrypt certificate D:", e);
+        }
+
+        if (body.isEmpty()) {
+            mod.error("An unknown error occurred whilst adding the Let's Encrypt root certificate. I'm afraid you may not be able to access resources with a Let's Encrypt certificate D:");
+        } else {
+            mod.info("Done - you are now able to access resources with a Let's Encrypt certificate :D");
+        }
+    }
+}