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fix(csp): require explicit allowlist for external-pad framing (#102) #116

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Merged
Jaggob merged 1 commit into from
Jun 2, 2026
Merged

fix(csp): require explicit allowlist for external-pad framing (#102) #116

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11 changes: 8 additions & 3 deletions lib/Listeners/CSPListener.php
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Original file line number Diff line number Diff line change
Expand Up @@ -53,9 +53,14 @@ private function getAllowedFrameDomains(): array {

$rawAllowlist = trim((string)$this->config->getAppValue('etherpad_nextcloud', 'external_pad_allowlist', ''));
if ($rawAllowlist === '') {
// Empty allowlist means "allow all public HTTPS hosts" for external pad linking.
// Mirror that behavior in CSP so valid external pads can actually load in the iframe.
$domains['https:'] = true;
// An empty allowlist means "allow all public HTTPS hosts" for the
// server-side snapshot fetch (see ExternalPadExportFetcher), but we
// must NOT mirror that into CSP: this listener handles *every*
// AddContentSecurityPolicyEvent, so emitting `https:` here would
// relax frame-src/child-src on all of Nextcloud, not just pad pages.
// External pads are shown as locally rendered snapshots (no live
// iframe to the external host), so framing them is unnecessary;
// only concrete allowlisted hosts ever get a frame relaxation.
return array_keys($domains);
}

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51 changes: 42 additions & 9 deletions tests/phpunit/unit/CSPListenerTest.php
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Expand Up @@ -46,7 +46,10 @@ static function (string $app, string $key, string $default = ''): string {
], $policies[0]->getAllowedChildSrcDomains());
}

public function testHandleAllowsAllHttpsWhenExternalAllowlistIsEmpty(): void {
public function testHandleNeverEmitsBlanketHttpsWhenExternalAllowlistIsEmpty(): void {
// Regression for #102: external pads enabled + empty allowlist must NOT
// relax frame-src/child-src to `https:` globally. Only the concrete
// configured Etherpad host is allowed to be framed.
$config = $this->createMock(IConfig::class);
$config->method('getAppValue')->willReturnCallback(
static function (string $app, string $key, string $default = ''): string {
Expand All @@ -70,13 +73,43 @@ static function (string $app, string $key, string $default = ''): string {

$policies = $event->getPolicies();
$this->assertCount(1, $policies);
$this->assertSame([
'https://pad.jaggob.uber.space',
'https:',
], $policies[0]->getAllowedFrameDomains());
$this->assertSame([
'https://pad.jaggob.uber.space',
'https:',
], $policies[0]->getAllowedChildSrcDomains());
$this->assertSame(
['https://pad.jaggob.uber.space'],
$policies[0]->getAllowedFrameDomains()
);
$this->assertSame(
['https://pad.jaggob.uber.space'],
$policies[0]->getAllowedChildSrcDomains()
);
$this->assertNotContains('https:', $policies[0]->getAllowedFrameDomains());
$this->assertNotContains('https:', $policies[0]->getAllowedChildSrcDomains());
}

public function testHandleEmitsNoPolicyWhenOnlyExternalEmptyAllowlistAndNoLocalHost(): void {
// With no local Etherpad host and an empty external allowlist there is
// nothing concrete to allow, so the listener must add no policy at all
// (rather than a blanket `https:`).
$config = $this->createMock(IConfig::class);
$config->method('getAppValue')->willReturnCallback(
static function (string $app, string $key, string $default = ''): string {
if ($app !== 'etherpad_nextcloud') {
return $default;
}

return match ($key) {
'etherpad_host' => '',
'allow_external_pads' => 'yes',
'external_pad_allowlist' => '',
default => $default,
};
}
);

$listener = new CSPListener($config);
$event = new AddContentSecurityPolicyEvent();

$listener->handle($event);

$this->assertSame([], $event->getPolicies());
}
}