Use URL for S3.

Thanks to Oscar Mira <valldrac@molly.im> for bringing this to our attention.

app/src/main/java/org/thoughtcrime/securesms/s3/S3.kt

@@ -1,6 +1,7 @@
 package org.thoughtcrime.securesms.s3
 
 import android.content.Context
+import androidx.annotation.VisibleForTesting
 import androidx.annotation.WorkerThread
 import okhttp3.Request
 import okhttp3.Response
@@ -20,6 +21,9 @@ import java.io.File
 import java.io.FileOutputStream
 import java.io.IOException
 import java.io.OutputStream
+import java.net.URI
+import java.net.URISyntaxException
+import java.net.URL
 import java.nio.charset.Charset
 import java.security.MessageDigest
 import java.util.regex.Matcher
@@ -31,9 +35,8 @@ import java.util.regex.Pattern
 object S3 {
   private val TAG = Log.tag(S3::class.java)
 
-  private val okHttpClient = AppDependencies.signalOkHttpClient
+  private val okHttpClient by lazy { AppDependencies.signalOkHttpClient }
 
-  private const val S3_BASE = "https://updates2.signal.org"
   const val DYNAMIC_PATH = "/dynamic"
   const val STATIC_PATH = "/static"
 
@@ -78,6 +81,8 @@ object S3 {
 
   /**
    * Retrieves an S3 object from the given endpoint.
+   *
+   * @param endpoint Must be an absolute path to the resource
    */
   @WorkerThread
   @JvmStatic
@@ -85,7 +90,7 @@ object S3 {
   fun getObject(endpoint: String): Response {
     val request = Request.Builder()
       .get()
-      .url("$S3_BASE$endpoint")
+      .url(s3Url(endpoint))
       .build()
 
     return okHttpClient.newCall(request).execute()
@@ -191,12 +196,14 @@ object S3 {
 
   /**
    * Downloads and parses the ETAG from an S3 object, utilizing a HEAD request.
+   *
+   * @param endpoint Must be an absolute path to the resource
    */
   @WorkerThread
   fun getObjectMD5(endpoint: String): ByteArray? {
     val request = Request.Builder()
       .head()
-      .url("$S3_BASE$endpoint")
+      .url(s3Url(endpoint))
       .build()
 
     try {
@@ -229,5 +236,15 @@ object S3 {
     }
   }
 
+  @Throws(IOException::class)
+  @VisibleForTesting
+  fun s3Url(path: String): URL {
+    try {
+      return URI("https", "updates2.signal.org", path, null).toURL()
+    } catch (e: URISyntaxException) {
+      throw IOException(e)
+    }
+  }
+
   class Md5FailureException : IOException("Failed to getting or comparing MD5")
 }