src/java.base/share/classes/java/util/zip/ZipFile.java

@@ -1120,34 +1120,40 @@
                             comment = new byte[comlen];
                             if (readFullyAt(comment, 0, comlen, end.endpos + ENDHDR) != comlen) {
                                 zerror("zip comment read failed");
                             }
                         }
-                        if (end.cenlen == ZIP64_MAGICVAL ||
-                            end.cenoff == ZIP64_MAGICVAL ||
-                            end.centot == ZIP64_MAGICCOUNT)
-                        {
-                            // need to find the zip64 end;
+                        // must check for a zip64 end record; it is always permitted to be present
                             try {
                                 byte[] loc64 = new byte[ZIP64_LOCHDR];
-                                if (readFullyAt(loc64, 0, loc64.length, end.endpos - ZIP64_LOCHDR)
+                            if (end.endpos < ZIP64_LOCHDR ||
+                                readFullyAt(loc64, 0, loc64.length, end.endpos - ZIP64_LOCHDR)
                                     != loc64.length || GETSIG(loc64) != ZIP64_LOCSIG) {
                                     return end;
                                 }
                                 long end64pos = ZIP64_LOCOFF(loc64);
                                 byte[] end64buf = new byte[ZIP64_ENDHDR];
                                 if (readFullyAt(end64buf, 0, end64buf.length, end64pos)
                                     != end64buf.length || GETSIG(end64buf) != ZIP64_ENDSIG) {
                                     return end;
                                 }
-                                // end64 found, re-calcualte everything.
-                                end.cenlen = ZIP64_ENDSIZ(end64buf);
-                                end.cenoff = ZIP64_ENDOFF(end64buf);
-                                end.centot = (int)ZIP64_ENDTOT(end64buf); // assume total < 2g
+                            // end64 candidate found, 
+                            long cenlen64 = ZIP64_ENDSIZ(end64buf);
+                            long cenoff64 = ZIP64_ENDOFF(end64buf);
+                            long centot64 = ZIP64_ENDTOT(end64buf);
+                            // double-check
+                            if (cenlen64 != end.cenlen && end.cenlen != ZIP64_MAGICVAL ||
+                                cenoff64 != end.cenoff && end.cenoff != ZIP64_MAGICVAL ||
+                                centot64 != end.centot && end.centot != ZIP64_MAGICCOUNT) {
+                                return end;
+                            }
+                            // to use the end64 values
+                            end.cenlen = cenlen64;
+                            end.cenoff = cenoff64;
+                            end.centot = (int)centot64; // assume total < 2g
                                 end.endpos = end64pos;
                             } catch (IOException x) {}    // no zip64 loc/end
-                        }
                         return end;
                     }
                 }
             }
             zerror("zip END header not found");