Check tasty file hash

Author: nicolasstucki

compiler/src/dotty/tools/backend/jvm/GenBCode.scala

@@ -26,6 +26,7 @@ import scala.tools.asm
 import scala.tools.asm.tree._
 import tpd._
 import StdNames._
+import dotty.tools.dotc.core.tasty.TastyPickler
 import dotty.tools.io._
 
 class GenBCode extends Phase {
@@ -221,9 +222,9 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
                 val outstream = new DataOutputStream(outTastyFile.bufferedOutput)
                 try outstream.write(binary)
                 finally outstream.close()
-                // TASTY attribute is created but 0 bytes are stored in it.
-                // A TASTY attribute has length 0 if and only if the .tasty file exists.
-                Array.empty[Byte]
+                // TASTY attribute is created but only the header bytes are stored in it.
+                // A TASTY attribute has length `headerSize` if and only if the .tasty file exists.
+                java.util.Arrays.copyOf(binary, TastyPickler.headerSize)
               } else {
                 // Create an empty file to signal that a tasty section exist in the corresponding .class
                 // This is much cheaper and simpler to check than doing classfile parsing

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -6,6 +6,7 @@ package classfile
 import Contexts._, Symbols._, Types._, Names._, StdNames._, NameOps._, Scopes._, Decorators._
 import SymDenotations._, unpickleScala2.Scala2Unpickler._, Constants._, Annotations._, util.Positions._
 import NameKinds.{ModuleClassName, DefaultGetterName}
+import dotty.tools.dotc.core.tasty.{TastyHeaderUnpickler, TastyPickler}
 import ast.tpd._
 import java.io.{ ByteArrayInputStream, ByteArrayOutputStream, DataInputStream, File, IOException }
 import java.nio
@@ -785,7 +786,10 @@ class ClassfileParser(
 
       if (scan(tpnme.TASTYATTR)) {
         val attrLen = in.nextInt
-        if (attrLen == 0) { // A tasty attribute implies the existence of the .tasty file
+        val bytes = in.nextBytes(attrLen)
+        val headerUnpickler = new TastyHeaderUnpickler(bytes)
+        headerUnpickler.readHeader()
+        if (headerUnpickler.isAtEnd) { // A tasty attribute with that has only a header implies the existence of the .tasty file
           val tastyBytes: Array[Byte] = classfile.underlyingSource match { // TODO: simplify when #3552 is fixed
             case None =>
               ctx.error("Could not load TASTY from .tasty for virtual file " + classfile)
@@ -816,10 +820,13 @@ class ClassfileParser(
                 Array.empty
               }
           }
-          if (tastyBytes.nonEmpty)
+          if (tastyBytes.nonEmpty) {
+            if (!tastyBytes.startsWith(bytes))
+              ctx.error("Header of TASTY file did not correspond to header in classfile. One of the files might be outdated or corrupted.")
             return unpickleTASTY(tastyBytes)
+          }
         }
-        else return unpickleTASTY(in.nextBytes(attrLen))
+        else return unpickleTASTY(bytes)
       }
 
       if (scan(tpnme.ScalaATTR) && !scalaUnpickleWhitelist.contains(classRoot.name)) {

compiler/src/dotty/tools/dotc/core/tasty/TastyHeaderUnpickler.scala

@@ -0,0 +1,31 @@
+package dotty.tools.dotc
+package core
+package tasty
+
+import java.util.UUID
+
+import dotty.tools.dotc.core.tasty.TastyFormat.{MajorVersion, MinorVersion, header}
+import dotty.tools.dotc.core.tasty.TastyUnpickler.UnpickleException
+
+class TastyHeaderUnpickler(reader: TastyReader) {
+  import reader._
+
+  def this(bytes: Array[Byte]) = this(new TastyReader(bytes))
+
+  def readHeader(): UUID = {
+    for (i <- 0 until header.length)
+      check(readByte() == header(i), "not a TASTy file")
+    val major = readNat()
+    val minor = readNat()
+    check(major == MajorVersion && minor <= MinorVersion,
+      s"""TASTy signature has wrong version.
+         | expected: $MajorVersion.$MinorVersion
+         | found   : $major.$minor""".stripMargin)
+    new UUID(readUncompressedLong(), readUncompressedLong())
+  }
+
+  def isAtEnd: Boolean = reader.isAtEnd
+
+  private def check(cond: Boolean, msg: => String): Unit =
+    if (!cond) throw new UnpickleException(msg)
+}

compiler/src/dotty/tools/dotc/core/tasty/TastyPickler.scala

@@ -29,12 +29,13 @@ class TastyPickler(val rootCls: ClassSymbol) {
     val uuidHi: Long = sections.iterator.map(x => pjwHash64(x._2.bytes)).fold(0L)(_ ^ _)
 
     val headerBuffer = {
-      val buf = new TastyBuffer(header.length + 24)
+      val buf = new TastyBuffer(TastyPickler.headerSize)
       for (ch <- header) buf.writeByte(ch.toByte)
       buf.writeNat(MajorVersion)
       buf.writeNat(MinorVersion)
       buf.writeUncompressedLong(uuidLow)
       buf.writeUncompressedLong(uuidHi)
+      assert(buf.length == TastyPickler.headerSize)
       buf
     }
 
@@ -90,3 +91,7 @@ class TastyPickler(val rootCls: ClassSymbol) {
     h
   }
 }
+
+object TastyPickler {
+  val headerSize = header.length + 18
+}

compiler/src/dotty/tools/dotc/core/tasty/TastyUnpickler.scala

@@ -35,9 +35,6 @@ class TastyUnpickler(reader: TastyReader) {
   private val sectionReader = new mutable.HashMap[String, TastyReader]
   val nameAtRef = new NameTable
 
-  private def check(cond: Boolean, msg: => String) =
-    if (!cond) throw new UnpickleException(msg)
-
   private def readName(): TermName = nameAtRef(readNameRef())
   private def readString(): String = readName().toString
 
@@ -73,19 +70,7 @@ class TastyUnpickler(reader: TastyReader) {
     result
   }
 
-  private def readHeader(): UUID = {
-    for (i <- 0 until header.length)
-      check(readByte() == header(i), "not a TASTy file")
-    val major = readNat()
-    val minor = readNat()
-    check(major == MajorVersion && minor <= MinorVersion,
-      s"""TASTy signature has wrong version.
-         | expected: $MajorVersion.$MinorVersion
-         | found   : $major.$minor""".stripMargin)
-    new UUID(readUncompressedLong(), readUncompressedLong())
-  }
-
-  private val uuid = readHeader()
+  new TastyHeaderUnpickler(reader).readHeader()
 
   locally {
     until(readEnd()) { nameAtRef.add(readNameContents()) }