Fixes access check and properly handling GID set

src/file.ts

@@ -1,6 +1,6 @@
 import type { FileReadResult } from 'node:fs/promises';
-import { O_APPEND, O_CREAT, O_EXCL, O_RDONLY, O_RDWR, O_SYNC, O_TRUNC, O_WRONLY, S_IFMT, size_max } from './emulation/constants.js';
 import { config } from './emulation/config.js';
+import { O_APPEND, O_CREAT, O_EXCL, O_RDONLY, O_RDWR, O_SYNC, O_TRUNC, O_WRONLY, S_IFMT, size_max } from './emulation/constants.js';
 import { Errno, ErrnoError } from './error.js';
 import type { FileSystem } from './filesystem.js';
 import './polyfills.js';

src/inode.ts

@@ -1,5 +1,5 @@
+import { deserialize, serialize, sizeof, struct, types as t } from 'utilium';
 import { Stats, type StatsLike } from './stats.js';
-import { types as t, struct, sizeof, serialize, deserialize } from 'utilium';
 
 /**
  * Alias for an ino.
@@ -108,8 +108,8 @@ export class Inode implements StatsLike {
 			hasChanged = true;
 		}
 
-		if (this.uid !== stats.uid) {
-			this.uid = stats.uid;
+		if (this.gid !== stats.gid) {
+			this.gid = stats.gid;
 			hasChanged = true;
 		}
 

src/stats.ts

@@ -1,6 +1,28 @@
 import type * as Node from 'node:fs';
 import { credentials, type Credentials } from './credentials.js';
-import { S_IFBLK, S_IFCHR, S_IFDIR, S_IFIFO, S_IFLNK, S_IFMT, S_IFREG, S_IFSOCK, S_IRWXG, S_IRWXO, S_IRWXU, size_max } from './emulation/constants.js';
+import {
+	R_OK,
+	S_IFBLK,
+	S_IFCHR,
+	S_IFDIR,
+	S_IFIFO,
+	S_IFLNK,
+	S_IFMT,
+	S_IFREG,
+	S_IFSOCK,
+	S_IRGRP,
+	S_IROTH,
+	S_IRUSR,
+	S_IWGRP,
+	S_IWOTH,
+	S_IWUSR,
+	S_IXGRP,
+	S_IXOTH,
+	S_IXUSR,
+	size_max,
+	W_OK,
+	X_OK,
+} from './emulation/constants.js';
 
 /**
  * Indicates the type of a file. Applied to 'mode'.
@@ -222,13 +244,35 @@ export abstract class StatsCommon<T extends number | bigint> implements Node.Sta
 	 */
 	public hasAccess(mode: number): boolean {
 		if (credentials.euid === 0 || credentials.egid === 0) {
-			//Running as root
+			// Running as root
 			return true;
 		}
 
-		// Mask for
-		const adjusted = (credentials.uid == this.uid ? S_IRWXU : 0) | (credentials.gid == this.gid ? S_IRWXG : 0) | S_IRWXO;
-		return (mode & this.mode & adjusted) == mode;
+		let perm = 0;
+
+		// Owner permissions
+		if (credentials.uid === this.uid) {
+			if (this.mode & S_IRUSR) perm |= R_OK;
+			if (this.mode & S_IWUSR) perm |= W_OK;
+			if (this.mode & S_IXUSR) perm |= X_OK;
+		}
+
+		// Group permissions
+		if (credentials.gid === this.gid) {
+			if (this.mode & S_IRGRP) perm |= R_OK;
+			if (this.mode & S_IWGRP) perm |= W_OK;
+			if (this.mode & S_IXGRP) perm |= X_OK;
+		}
+
+		// Others permissions
+		if (credentials.uid !== this.uid && credentials.gid !== this.gid) {
+			if (this.mode & S_IROTH) perm |= R_OK;
+			if (this.mode & S_IWOTH) perm |= W_OK;
+			if (this.mode & S_IXOTH) perm |= X_OK;
+		}
+
+		// Perform the access check
+		return (perm & mode) === mode;
 	}
 
 	/**

tests/fs/stat.test.ts

@@ -1,5 +1,6 @@
 import assert from 'node:assert';
 import { suite, test } from 'node:test';
+import { credentials } from '../../dist/credentials.js';
 import { Stats } from '../../dist/stats.js';
 import { fs } from '../common.js';
 
@@ -34,6 +35,47 @@ suite('Stats', () => {
 		fs.close(fd);
 	});
 
+	test('hasAccess for non-root access', () => {
+		const newFile = 'new.txt';
+
+		fs.writeFileSync(newFile, 'hello', {
+			mode: 0o640, // allow group access
+		});
+
+		const prevCredentials = {
+			...credentials,
+		};
+		const uid = 33;
+		const nonRootCredentials = {
+			uid,
+			gid: uid,
+			euid: uid,
+			egid: uid,
+			suid: uid,
+			sgid: uid,
+		};
+
+		fs.chownSync(newFile, 0, nonRootCredentials.gid); // creating with root-user so that non-root user can access
+
+		Object.assign(credentials, nonRootCredentials);
+		const stat = fs.statSync(newFile);
+
+		assert.equal(stat.gid, nonRootCredentials.gid);
+		assert.equal(stat.uid, 0);
+		assert.equal(stat.hasAccess(fs.constants.R_OK), true);
+		assert.equal(stat.hasAccess(fs.constants.W_OK), false);
+		assert.equal(stat.hasAccess(fs.constants.X_OK), false);
+		// changing group
+
+		Object.assign(credentials, { ...nonRootCredentials, gid: 44 });
+
+		assert.equal(stat.hasAccess(fs.constants.R_OK), false);
+		assert.equal(stat.hasAccess(fs.constants.W_OK), false);
+		assert.equal(stat.hasAccess(fs.constants.X_OK), false);
+
+		Object.assign(credentials, prevCredentials);
+	});
+
 	test('stat file', async () => {
 		const stats = await fs.promises.stat(existing_file);
 		assert(!stats.isDirectory());