Implement createWriteStream for Linux

index.js

@@ -1,5 +1,5 @@
 const fs = require('fs')
-const { spawn } = require('child_process')
+const { spawn, spawnSync } = require('child_process')
 const EventEmitter = require('events')
 const binding = require('./build/Release/fs_admin.node')
 const fsAdmin = module.exports
@@ -149,6 +149,45 @@ switch (process.platform) {
       }
     })
     break
+
+  case 'linux':
+    Object.assign(fsAdmin, {
+      clearAuthorizationCache () {
+        spawnSync('/bin/pkcheck', ['--revoke-temp'])
+      },
+
+      createWriteStream (filePath) {
+        // Prompt for credentials synchronously to avoid creating multiple simultaneous prompts.
+        if (!fsAdmin.testMode && spawnSync('/usr/bin/pkexec', ['/bin/dd']).status !== 0) {
+          const result = new EventEmitter()
+          result.write = result.end = function () {}
+          process.nextTick(() => result.emit('error', new Error('Failed to obtain credentials')))
+          return result
+        }
+
+        const dd = fsAdmin.testMode
+          ? spawn('/bin/dd', ['of=' + filePath])
+          : spawn('/usr/bin/pkexec', ['/bin/dd', 'of=' + filePath])
+
+        const stream = new EventEmitter()
+        stream.write = (chunk, encoding, callback) => {
+          dd.stdin.write(chunk, encoding, callback)
+        }
+        stream.end = (callback) => {
+          if (callback) stream.on('finish', callback)
+          dd.stdin.end()
+        }
+        dd.on('exit', (exitCode) => {
+          if (exitCode !== 0) {
+            stream.emit('error', new Error('dd exited with code ' + exitCode))
+          }
+          stream.emit('finish')
+        })
+
+        return stream
+      }
+    })
+    break
 }
 
 function wrapCallback (commandName, callback) {

test/fs-admin.test.js

@@ -7,10 +7,6 @@ const fsAdmin = require('..')
 // Comment this out to test with actual privilege escalation.
 fsAdmin.testMode = true
 
-if (process.platform !== 'win32' && process.platform !== 'darwin') {
-  process.exit(0)
-}
-
 describe('fs-admin', function () {
   let dirPath, filePath
 
@@ -23,7 +19,7 @@ describe('fs-admin', function () {
   if (!fsAdmin.testMode) this.timeout(10000)
 
   describe('createWriteStream', () => {
-    if (process.platform !== 'darwin') return
+    if (process.platform === 'win32') return
 
     it('writes to the given file as the admin user', (done) => {
       fs.writeFileSync(filePath, '')
@@ -74,6 +70,8 @@ describe('fs-admin', function () {
   })
 
   describe('makeTree', () => {
+    if (process.platform === 'linux') return
+
     it('creates a directory at the given path as the admin user', (done) => {
       const pathToCreate = path.join(dirPath, 'dir1', 'dir2', 'dir3')
 
@@ -92,6 +90,8 @@ describe('fs-admin', function () {
   })
 
   describe('unlink', () => {
+    if (process.platform === 'linux') return
+
     it('deletes the given file as the admin user', (done) => {
       fs.writeFileSync(filePath, '')
 
@@ -126,6 +126,8 @@ describe('fs-admin', function () {
   })
 
   describe('symlink', () => {
+    if (process.platform === 'linux') return
+
     it('creates a symlink at the given path as the admin user', (done) => {
       fsAdmin.symlink(__filename, filePath, (error) => {
         assert.strictEqual(error, null)
@@ -141,6 +143,8 @@ describe('fs-admin', function () {
   })
 
   describe('recursiveCopy', () => {
+    if (process.platform === 'linux') return
+
     it('copies the given folder to the given location as the admin user', (done) => {
       const sourcePath = path.join(dirPath, 'src-dir')
       fs.mkdirSync(sourcePath)