Hostname validation

.github/workflows/ci.yml

@@ -30,6 +30,7 @@ jobs:
       run: |
         meson setup build
         ninja -C build install
+        ninja -C build test
 
   lint:
     runs-on: ubuntu-latest

meson.build

@@ -36,3 +36,4 @@ subdir('common')
 subdir('daemon')
 subdir('src')
 subdir('data')
+subdir('test')

src/HostnameValidator.vala

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2018-2022 System76 <[email protected]>
+ * Copyright 2024 elementary, Inc. (https://elementary.io)
+ * SPDX-License-Identifier: MIT
+ */
+
+namespace Utils {
+    private bool hostname_is_valid_char (char c) {
+        return (c.isalnum () ||
+                c == '-' ||
+                c == '.');
+    }
+
+    // Based on https://github.com/pop-os/hostname-validator/blob/458fa5a1df98cb663f0456dffb542e1a907861c9/src/lib.rs#L29
+    /// Validate a hostname according to [IETF RFC 1123](https://tools.ietf.org/html/rfc1123).
+    ///
+    /// A hostname is valid if the following condition are true:
+    ///
+    /// - It does not start or end with `-` or `.`.
+    /// - It does not contain any characters outside of the alphanumeric range, except for `-` and `.`.
+    /// - It is not empty.
+    /// - It is 253 or fewer characters.
+    /// - Its labels (characters separated by `.`) are not empty.
+    /// - Its labels are 63 or fewer characters.
+    /// - Its labels do not start or end with '-' or '.'.
+    public bool hostname_is_valid (string hostname) {
+        for (int i = 0; i < hostname.char_count (); i++) {
+            char c = hostname[i];
+            if (!hostname_is_valid_char (c)) {
+                return false;
+            }
+        }
+
+        string[] labels = hostname.split (".", -1);
+        foreach (string label in labels) {
+            if (label.char_count () == 0 || label.length > 63 || label[0] == '-' || label[label.length - 1] == '-') {
+                return false;
+            }
+        }
+
+        return !(hostname.char_count () == 0 || hostname.length > 253);
+    }
+}

src/Utils.vala

@@ -267,7 +267,7 @@ namespace Utils {
         // If the automatic hostname logic fails in some way, it's possible we may generate an invalid
         // hostname. We could fix this by trimming traling/leading hyphens or other invalid characters.
         // But it's probably a bad hostname anyway, so just fallback
-        if (!Distinst.validate_hostname (hostname)) {
+        if (!hostname_is_valid (hostname)) {
             hostname = "elementary-os";
         }
 

src/meson.build

@@ -1,5 +1,6 @@
 vala_files = [
     'Application.vala',
+    'HostnameValidator.vala',
     'MainWindow.vala',
     'Utils.vala',
     'Helpers/InstallerDaemon.vala',

test/HostnameValidatorTest.vala

@@ -0,0 +1,24 @@
+void add_hostname_validator_tests () {
+    Test.add_func ("/valid", () => {
+        assert (Utils.hostname_is_valid ("VaLiD-HoStNaMe"));
+        assert (Utils.hostname_is_valid ("50-name"));
+        assert (Utils.hostname_is_valid ("235235"));
+        assert (Utils.hostname_is_valid ("example.com"));
+        assert (Utils.hostname_is_valid ("VaLid.HoStNaMe"));
+        assert (Utils.hostname_is_valid ("123.456"));
+    });
+
+    Test.add_func ("/invalid", () => {
+        assert (!Utils.hostname_is_valid ("-invalid-name"));
+        assert (!Utils.hostname_is_valid ("also-invalid-"));
+        assert (!Utils.hostname_is_valid ("asdf@fasd"));
+        assert (!Utils.hostname_is_valid ("@asdfl"));
+        assert (!Utils.hostname_is_valid ("asd f@"));
+        assert (!Utils.hostname_is_valid (".invalid"));
+        assert (!Utils.hostname_is_valid ("invalid.name."));
+        assert (!Utils.hostname_is_valid ("foo.label-is-way-to-longgggggggggggggggggggggggggggggggggggggggggggg.org"));
+        assert (!Utils.hostname_is_valid ("invalid.-starting.char"));
+        assert (!Utils.hostname_is_valid ("invalid.ending-.char"));
+        assert (!Utils.hostname_is_valid ("empty..label"));
+    });
+}

test/Test.vala

@@ -0,0 +1,5 @@
+void main (string[] args) {
+    Test.init (ref args);
+    add_hostname_validator_tests ();
+    Test.run ();
+}

test/meson.build

@@ -0,0 +1,13 @@
+test_dependencies = [
+    glib_dep,
+]
+
+tests = executable(
+    meson.project_name() + '-tests',
+    'HostnameValidatorTest.vala',
+    'Test.vala',
+    meson.project_source_root() + '/src/HostnameValidator.vala',
+    dependencies: test_dependencies
+)
+
+test('Test', tests)