lib,permission: handle buffer on fs.symlink

PR-URL: https://github.com/nodejs/node/pull/51212
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>

lib/fs.js

@@ -40,6 +40,7 @@ const {
   StringPrototypeCharCodeAt,
   StringPrototypeIndexOf,
   StringPrototypeSlice,
+  uncurryThis,
 } = primordials;
 
 const { fs: constants } = internalBinding('constants');
@@ -66,6 +67,8 @@ const binding = internalBinding('fs');
 const { createBlobFromFilePath } = require('internal/blob');
 
 const { Buffer } = require('buffer');
+const { isBuffer: BufferIsBuffer } = Buffer;
+const BufferToString = uncurryThis(Buffer.prototype.toString);
 const {
   aggregateTwoErrors,
   codes: {
@@ -1721,7 +1724,12 @@ function symlink(target, path, type_, callback_) {
   if (permission.isEnabled()) {
     // The permission model's security guarantees fall apart in the presence of
     // relative symbolic links. Thus, we have to prevent their creation.
-    if (typeof target !== 'string' || !isAbsolute(toPathIfFileURL(target))) {
+    if (BufferIsBuffer(target)) {
+      if (!isAbsolute(BufferToString(target))) {
+        callback(new ERR_ACCESS_DENIED('relative symbolic link target'));
+        return;
+      }
+    } else if (typeof target !== 'string' || !isAbsolute(toPathIfFileURL(target))) {
       callback(new ERR_ACCESS_DENIED('relative symbolic link target'));
       return;
     }

test/parallel/test-permission-fs-symlink-relative.js

@@ -5,6 +5,7 @@ const common = require('../common');
 common.skipIfWorker();
 
 const assert = require('assert');
+const path = require('path');
 const { symlinkSync, symlink, promises: { symlink: symlinkAsync } } = require('fs');
 
 const error = {
@@ -25,3 +26,16 @@ for (const targetString of ['a', './b/c', '../d', 'e/../f', 'C:drive-relative',
     }
   }
 }
+
+// Absolute should not throw
+for (const targetString of [path.resolve('.')]) {
+  for (const target of [targetString, Buffer.from(targetString)]) {
+    for (const path of [__filename]) {
+      symlink(target, path, common.mustCall((err) => {
+        assert(err);
+        assert.strictEqual(err.code, 'EEXIST');
+        assert.match(err.message, /file already exists/);
+      }));
+    }
+  }
+}