drop dirCache for symlink on all platforms

lib/unpack.js

@@ -523,13 +523,13 @@ class Unpack extends Parser {
     // then that means we are about to delete the directory we created
     // previously, and it is no longer going to be a directory, and neither
     // is any of its children.
-    // If a symbolic link is encountered on Windows, all bets are off.
-    // There is no reasonable way to sanitize the cache in such a way
-    // we will be able to avoid having filesystem collisions.  If this
-    // happens with a non-symlink entry, it'll just fail to unpack,
-    // but a symlink to a directory, using an 8.3 shortname, can evade
-    // detection and lead to arbitrary writes to anywhere on the system.
-    if (isWindows && entry.type === 'SymbolicLink')
+    // If a symbolic link is encountered, all bets are off.  There is no
+    // reasonable way to sanitize the cache in such a way we will be able to
+    // avoid having filesystem collisions.  If this happens with a non-symlink
+    // entry, it'll just fail to unpack, but a symlink to a directory, using an
+    // 8.3 shortname or certain unicode attacks, can evade detection and lead
+    // to arbitrary writes to anywhere on the system.
+    if (entry.type === 'SymbolicLink')
       dropCache(this.dirCache)
     else if (entry.type !== 'Directory')
       pruneCache(this.dirCache, entry.absolute)

test/unpack.js

@@ -2719,6 +2719,10 @@ t.test('dirCache pruning unicode normalized collisions', {
       path: Buffer.from([0x63, 0x61, 0x66, 0x65, 0xcc, 0x81]).toString(),
       linkpath: 'foo',
     },
+    {
+      type: 'Directory',
+      path: 'foo',
+    },
     {
       type: 'File',
       path: Buffer.from([0x63, 0x61, 0x66, 0xc3, 0xa9]).toString() + '/bar',
@@ -2732,7 +2736,6 @@ t.test('dirCache pruning unicode normalized collisions', {
   const check = (path, dirCache, t) => {
     path = path.replace(/\\/g, '/')
     t.strictSame([...dirCache.entries()], [
-      [path, true],
       [`${path}/foo`, true],
     ])
     t.equal(fs.readFileSync(path + '/foo/bar', 'utf8'), 'x')