Run Docker container as current user (#1975)

Previously, mega-linter-runner ran the MegaLinter Docker image as root.
Users whose files became owned by root as a consequence of this
behavior will need to chown them to be owned by the appropriate user.
This change only affects POSIX platforms, because process.getuid and
process.getgid are only available there.

CHANGELOG.md

@@ -10,6 +10,7 @@ Note: Can be used with `oxsecurity/megalinter@beta` in your GitHub Action mega-l
 
 - Fixes
   - Change name of config file for powershell formatter to avoid collision with powershell linter config
+  - Run Docker container as current user rather than root ([#1975](https://github.com/oxsecurity/megalinter/issues/1975))
 
 - Linter versions upgrades
   - [prettier](https://prettier.io/) from 2.8.1 to **2.8.2** on 2023-01-07

mega-linter-runner/lib/runner.js

@@ -4,6 +4,7 @@ const optionsDefinition = require("./options");
 const { spawnSync } = require("child_process");
 const c = require("chalk");
 const path = require("path");
+const { getgid, getuid } = require("process");
 const which = require("which");
 const fs = require("fs-extra");
 const { MegaLinterUpgrader } = require("./upgrade");
@@ -127,6 +128,9 @@ ERROR: Docker engine has not been found on your system.
     if (options["containerName"]) {
       commandArgs.push(...["--name", options["containerName"]]);
     }
+    if (getuid && getgid) {
+      commandArgs.push(...["--user", `${getuid()}:${getgid()}`]);
+    }
     commandArgs.push(...["-v", "/var/run/docker.sock:/var/run/docker.sock:rw"]);
     commandArgs.push(...["-v", `${lintPath}:/tmp/lint:rw`]);
     if (options.fix === true) {