Support auto-expansion of attachment jars on disk.

core/src/main/kotlin/core/Utils.kt

@@ -8,10 +8,12 @@
 
 package core
 
+import com.google.common.io.ByteStreams
 import com.google.common.util.concurrent.ListenableFuture
 import com.google.common.util.concurrent.MoreExecutors
 import com.google.common.util.concurrent.SettableFuture
 import org.slf4j.Logger
+import java.io.BufferedInputStream
 import java.io.InputStream
 import java.nio.file.Files
 import java.nio.file.Path
@@ -21,6 +23,7 @@ import java.time.temporal.Temporal
 import java.util.concurrent.Executor
 import java.util.concurrent.locks.Lock
 import java.util.concurrent.locks.ReentrantLock
+import java.util.zip.ZipInputStream
 import kotlin.concurrent.withLock
 import kotlin.reflect.KProperty
 
@@ -122,3 +125,31 @@ class TransientProperty<T>(private val initializer: () -> T) {
         return v!!
     }
 }
+
+/**
+ * Given a path to a zip file, extracts it to the given directory.
+ */
+fun extractZipFile(zipPath: Path, toPath: Path) {
+    if (!Files.exists(toPath))
+        Files.createDirectories(toPath)
+
+    ZipInputStream(BufferedInputStream(Files.newInputStream(zipPath))).use { zip ->
+        while (true) {
+            val e = zip.nextEntry ?: break
+            val outPath = toPath.resolve(e.name)
+
+            // Security checks: we should reject a zip that contains tricksy paths that try to escape toPath.
+            if (!outPath.normalize().startsWith(toPath))
+                throw IllegalStateException("ZIP contained a path that resolved incorrectly: ${e.name}")
+
+            if (e.isDirectory) {
+                Files.createDirectories(outPath)
+                continue
+            }
+            Files.newOutputStream(outPath).use { out ->
+                ByteStreams.copy(zip, out)
+            }
+            zip.closeEntry()
+        }
+    }
+}

src/main/kotlin/core/node/NodeAttachmentStorage.kt

@@ -15,11 +15,13 @@ import com.google.common.io.CountingInputStream
 import core.Attachment
 import core.AttachmentStorage
 import core.crypto.SecureHash
+import core.extractZipFile
 import core.utilities.loggerFor
 import java.io.FilterInputStream
 import java.io.InputStream
 import java.nio.file.Files
 import java.nio.file.Path
+import java.nio.file.Paths
 import java.nio.file.StandardCopyOption
 import java.util.*
 import java.util.jar.JarInputStream
@@ -35,6 +37,13 @@ class NodeAttachmentStorage(val storePath: Path) : AttachmentStorage {
     @VisibleForTesting
     var checkAttachmentsOnLoad = true
 
+    /**
+     * If true, newly inserted attachments will be unzipped to a subdirectory of the [storePath]. This is intended for
+     * human browsing convenience: the attachment itself will still be the file (that is, edits to the extracted directory
+     * will not have any effect).
+     */
+    @Volatile var automaticallyExtractAttachments = false
+
     init {
         require(Files.isDirectory(storePath)) { "$storePath must be a directory" }
     }
@@ -102,14 +111,29 @@ class NodeAttachmentStorage(val storePath: Path) : AttachmentStorage {
             Files.deleteIfExists(tmp)
         }
         log.info("Stored new attachment $id")
+        if (automaticallyExtractAttachments) {
+            val extractTo = storePath.resolve("${id}.jar")
+            try {
+                Files.createDirectory(extractTo)
+                extractZipFile(finalPath, extractTo)
+            } catch(e: Exception) {
+                log.error("Failed to extract attachment jar $id, ", e)
+                // TODO: Delete the extractTo directory here.
+            }
+        }
         return id
     }
 
     private fun checkIsAValidJAR(path: Path) {
         // Just iterate over the entries with verification enabled: should be good enough to catch mistakes.
         JarInputStream(Files.newInputStream(path), true).use { stream ->
-            var cursor = stream.nextJarEntry
-            while (cursor != null) cursor = stream.nextJarEntry
+            while (true) {
+                val cursor = stream.nextJarEntry ?: break
+                val entryPath = Paths.get(cursor.name)
+                // Security check to stop zips trying to escape their rightful place.
+                if (entryPath.isAbsolute || entryPath.normalize() != entryPath)
+                    throw IllegalArgumentException("Path is either absolute or non-normalised: $entryPath")
+            }
         }
     }
 }