--- a/modules/libjar/nsIZipReader.idl
+++ b/modules/libjar/nsIZipReader.idl
@@ -6,17 +6,17 @@
 
 #include "nsISupports.idl"
 
 interface nsIUTF8StringEnumerator;
 interface nsIInputStream;
 interface nsIFile;
 interface nsICertificatePrincipal;
 
-[scriptable, uuid(e1c028bc-c478-11da-95a8-00e08161165f)]
+[scriptable, uuid(fad6f72f-13d8-4e26-9173-53007a4afe71)]
 interface nsIZipEntry : nsISupports
 {
     /**
      * The type of compression used for the item.  The possible values and
      * their meanings are defined in the zip file specification at
      * http://www.pkware.com/business_and_developers/developer/appnote/
      */
     readonly attribute unsigned short   compression;
@@ -46,16 +46,20 @@ interface nsIZipEntry : nsISupports
      * entry represents a directory within the zip file which has no
      * corresponding entry within the zip file.  For example, the entry for the
      * directory foo/ in a zip containing exactly one entry for foo/bar.txt
      * is synthetic.  If the zip file contains an actual entry for a directory,
      * this attribute will be false for the nsIZipEntry for that directory.
      * It is impossible for a file to be synthetic.
      */
     readonly attribute boolean          isSynthetic;
+    /**
+     * The UNIX style file permissions of this item.
+     */
+    readonly attribute unsigned long    permissions;
 };
 
 [scriptable, uuid(38d6d07a-8a58-4fe7-be8b-ef6472fa83ff)]
 interface nsIZipReader : nsISupports
 {
     /**
      * Opens a zip file for reading.
      * It is allowed to open with another file, 

--- a/modules/libjar/nsJAR.cpp
+++ b/modules/libjar/nsJAR.cpp
@@ -906,16 +906,17 @@ nsJAREnumerator::GetNext(nsACString& aRe
 NS_IMPL_ISUPPORTS1(nsJARItem, nsIZipEntry)
 
 nsJARItem::nsJARItem(nsZipItem* aZipItem)
     : mSize(aZipItem->Size()),
       mRealsize(aZipItem->RealSize()),
       mCrc32(aZipItem->CRC32()),
       mLastModTime(aZipItem->LastModTime()),
       mCompression(aZipItem->Compression()),
+      mPermissions(aZipItem->Mode()),
       mIsDirectory(aZipItem->IsDirectory()),
       mIsSynthetic(aZipItem->isSynthetic)
 {
 }
 
 //------------------------------------------
 // nsJARItem::GetCompression
 //------------------------------------------
@@ -995,16 +996,28 @@ NS_IMETHODIMP
 nsJARItem::GetLastModifiedTime(PRTime* aLastModTime)
 {
     NS_ENSURE_ARG_POINTER(aLastModTime);
 
     *aLastModTime = mLastModTime;
     return NS_OK;
 }
 
+//------------------------------------------
+// nsJARItem::GetPermissions
+//------------------------------------------
+NS_IMETHODIMP
+nsJARItem::GetPermissions(uint32_t* aPermissions)
+{
+    NS_ENSURE_ARG_POINTER(aPermissions);
+
+    *aPermissions = mPermissions;
+    return NS_OK;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // nsIZipReaderCache
 
 NS_IMPL_ISUPPORTS3(nsZipReaderCache, nsIZipReaderCache, nsIObserver, nsISupportsWeakReference)
 
 nsZipReaderCache::nsZipReaderCache()
   : mLock("nsZipReaderCache.mLock")
   , mZips(16)

--- a/modules/libjar/nsJAR.h
+++ b/modules/libjar/nsJAR.h
@@ -137,16 +137,17 @@ public:
     virtual ~nsJARItem() {}
 
 private:
     uint32_t     mSize;             /* size in original file */
     uint32_t     mRealsize;         /* inflated size */
     uint32_t     mCrc32;
     PRTime       mLastModTime;
     uint16_t     mCompression;
+    uint32_t     mPermissions;
     bool mIsDirectory; 
     bool mIsSynthetic;
 };
 
 /**
  * nsJAREnumerator
  *
  * Enumerates a list of files in a zip archive 

--- a/modules/libjar/zipwriter/src/nsZipHeader.cpp
+++ b/modules/libjar/zipwriter/src/nsZipHeader.cpp
@@ -122,16 +122,26 @@ NS_IMETHODIMP nsZipHeader::GetLastModifi
 NS_IMETHODIMP nsZipHeader::GetIsSynthetic(bool *aIsSynthetic)
 {
     NS_ASSERTION(mInited, "Not initalised");
 
     *aIsSynthetic = false;
     return NS_OK;
 }
 
+/* readonly attribute unsigned long permissions; */
+NS_IMETHODIMP nsZipHeader::GetPermissions(uint32_t *aPermissions)
+{
+    NS_ASSERTION(mInited, "Not initalised");
+
+    // Always give user read access at least, this matches nsIZipReader's behaviour
+    *aPermissions = ((mEAttr >> 16) & 0xfff | 0x100);
+    return NS_OK;
+}
+
 void nsZipHeader::Init(const nsACString & aPath, PRTime aDate, uint32_t aAttr,
                        uint32_t aOffset)
 {
     NS_ASSERTION(!mInited, "Already initalised");
 
     PRExplodedTime time;
     PR_ExplodeTime(aDate, PR_LocalTimeParameters, &time);
 

--- a/modules/libjar/zipwriter/test/unit/test_zippermissions.js
+++ b/modules/libjar/zipwriter/test/unit/test_zippermissions.js
@@ -5,17 +5,17 @@
 
 const DATA = "ZIP WRITER TEST DATA";
 
 var TESTS = [];
 
 function build_tests() {
   var id = 0;
 
-  // Minimum mode is 0400
+  // Minimum mode is 0o400
   for (let u = 4; u <= 7; u++) {
     for (let g = 0; g <= 7; g++) {
       for (let o = 0; o <= 7; o++) {
         TESTS[id] = {
           name: "test" + u + g + o,
           permission: (u << 6) + (g << 3) + o
         };
         id++;
@@ -48,26 +48,36 @@ function run_test() {
     // This reduces the coverage of the test but there isn't much we can do
     var perm = file.permissions & 0xfff;
     if (TESTS[i].permission != perm) {
       dump("File permissions for " + TESTS[i].name + " were " + perm.toString(8) + "\n");
       TESTS[i].permission = perm;
     }
 
     zipW.addEntryFile(TESTS[i].name, Ci.nsIZipWriter.COMPRESSION_NONE, file, false);
-    file.permissions = 0600;
+    do_check_eq(zipW.getEntry(TESTS[i].name).permissions, TESTS[i].permission | 0o400);
+    file.permissions = 0o600;
     file.remove(true);
   }
   zipW.close();
 
+  zipW.open(tmpFile, PR_RDWR);
+  for (let i = 0; i < TESTS.length; i++) {
+    dump("Testing zipwriter file permissions for " + TESTS[i].name + "\n");
+    do_check_eq(zipW.getEntry(TESTS[i].name).permissions, TESTS[i].permission | 0o400);
+  }
+  zipW.close();
+
   var zipR = new ZipReader(tmpFile);
   for (let i = 0; i < TESTS.length; i++) {
+    dump("Testing zipreader file permissions for " + TESTS[i].name + "\n");
+    do_check_eq(zipR.getEntry(TESTS[i].name).permissions, TESTS[i].permission | 0o400);
+    dump("Testing extracted file permissions for " + TESTS[i].name + "\n");
     zipR.extract(TESTS[i].name, file);
-    dump("Testing file permissions for " + TESTS[i].name + "\n");
     do_check_eq(file.permissions & 0xfff, TESTS[i].permission);
     do_check_false(file.isDirectory());
-    file.permissions = 0600;
+    file.permissions = 0o600;
     file.remove(true);
   }
   zipR.close();
 
   tmp.remove(true);
 }