Allow "wasm-unsafe-eval" in CSP

If a page has a Content Security Policy header and the `script-src` (or
`default-src`) directive does not contain neither `wasm-unsafe-eval` nor
`unsafe-eval` loading and executing WebAssembly is blocked in the page
(although it is still possible to load and execute WebAssembly in a
worker thread).

Although the Nextcloud classes to manage the CSP already supported
allowing `unsafe-eval` this affects not only WebAssembly, but also the
`eval` operation in JavaScript.

To make possible to allow WebAssembly execution without allowing
JavaScript `eval` this commit adds support for allowing
`wasm-unsafe-eval`.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

Author: danxuliu

lib/private/Security/CSP/ContentSecurityPolicy.php

@@ -64,6 +64,20 @@ public function setEvalScriptAllowed(bool $evalScriptAllowed) {
 		$this->evalScriptAllowed = $evalScriptAllowed;
 	}
 
+	/**
+	 * @return boolean
+	 */
+	public function isEvalWasmAllowed(): ?bool {
+		return $this->evalWasmAllowed;
+	}
+
+	/**
+	 * @param boolean $evalWasmAllowed
+	 */
+	public function setEvalWasmAllowed(bool $evalWasmAllowed): void {
+		$this->evalWasmAllowed = $evalWasmAllowed;
+	}
+
 	/**
 	 * @return array
 	 */

lib/public/AppFramework/Http/ContentSecurityPolicy.php

@@ -44,6 +44,8 @@ class ContentSecurityPolicy extends EmptyContentSecurityPolicy {
 	protected $inlineScriptAllowed = false;
 	/** @var bool Whether eval in JS scripts is allowed */
 	protected $evalScriptAllowed = false;
+	/** @var bool Whether WebAssembly compilation is allowed */
+	protected ?bool $evalWasmAllowed = false;
 	/** @var bool Whether strict-dynamic should be set */
 	protected $strictDynamicAllowed = false;
 	/** @var array Domains from which scripts can get loaded */

lib/public/AppFramework/Http/EmptyContentSecurityPolicy.php

@@ -49,6 +49,8 @@ class EmptyContentSecurityPolicy {
 	 * @link https://github.com/owncloud/core/issues/11925
 	 */
 	protected $evalScriptAllowed = null;
+	/** @var bool Whether WebAssembly compilation is allowed */
+	protected ?bool $evalWasmAllowed = null;
 	/** @var array Domains from which scripts can get loaded */
 	protected $allowedScriptDomains = null;
 	/**
@@ -130,6 +132,17 @@ public function allowEvalScript($state = true) {
 		return $this;
 	}
 
+	/**
+	 * Whether WebAssembly compilation is allowed or forbidden
+	 * @param bool $state
+	 * @return $this
+	 * @since 27.0.0
+	 */
+	public function allowEvalWasm(bool $state = true) {
+		$this->evalWasmAllowed = $state;
+		return $this;
+	}
+
 	/**
 	 * Allows to execute JavaScript files from a specific domain. Use * to
 	 * allow JavaScript from all domains.
@@ -447,7 +460,7 @@ public function buildPolicy() {
 		$policy .= "base-uri 'none';";
 		$policy .= "manifest-src 'self';";
 
-		if (!empty($this->allowedScriptDomains) || $this->inlineScriptAllowed || $this->evalScriptAllowed) {
+		if (!empty($this->allowedScriptDomains) || $this->inlineScriptAllowed || $this->evalScriptAllowed || $this->evalWasmAllowed) {
 			$policy .= 'script-src ';
 			if (is_string($this->useJsNonce)) {
 				if ($this->strictDynamicAllowed) {
@@ -470,6 +483,9 @@ public function buildPolicy() {
 			if ($this->evalScriptAllowed) {
 				$policy .= ' \'unsafe-eval\'';
 			}
+			if ($this->evalWasmAllowed) {
+				$policy .= ' \'wasm-unsafe-eval\'';
+			}
 			$policy .= ';';
 		}
 

lib/public/AppFramework/Http/StrictContentSecurityPolicy.php

@@ -46,6 +46,8 @@ class StrictContentSecurityPolicy extends EmptyContentSecurityPolicy {
 	protected $inlineScriptAllowed = false;
 	/** @var bool Whether eval in JS scripts is allowed */
 	protected $evalScriptAllowed = false;
+	/** @var bool Whether WebAssembly compilation is allowed */
+	protected ?bool $evalWasmAllowed = false;
 	/** @var array Domains from which scripts can get loaded */
 	protected $allowedScriptDomains = [
 		'\'self\'',

tests/lib/AppFramework/Http/ContentSecurityPolicyTest.php

@@ -472,6 +472,13 @@ public function testGetPolicyUnsafeEval() {
 		$this->assertSame($expectedPolicy, $this->contentSecurityPolicy->buildPolicy());
 	}
 
+	public function testGetPolicyUnsafeWasmEval() {
+		$expectedPolicy = "default-src 'none';base-uri 'none';manifest-src 'self';script-src 'self' 'wasm-unsafe-eval';style-src 'self' 'unsafe-inline';img-src 'self' data: blob:;font-src 'self' data:;connect-src 'self';media-src 'self';frame-ancestors 'self';form-action 'self'";
+
+		$this->contentSecurityPolicy->allowEvalWasm(true);
+		$this->assertSame($expectedPolicy, $this->contentSecurityPolicy->buildPolicy());
+	}
+
 	public function testGetPolicyNonce() {
 		$nonce = 'my-nonce';
 		$expectedPolicy = "default-src 'none';base-uri 'none';manifest-src 'self';script-src 'nonce-".base64_encode($nonce) . "';style-src 'self' 'unsafe-inline';img-src 'self' data: blob:;font-src 'self' data:;connect-src 'self';media-src 'self';frame-ancestors 'self';form-action 'self'";

tests/lib/AppFramework/Http/EmptyContentSecurityPolicyTest.php

@@ -91,6 +91,13 @@ public function testGetPolicyScriptAllowInlineAndEval() {
 		$this->assertSame($expectedPolicy, $this->contentSecurityPolicy->buildPolicy());
 	}
 
+	public function testGetPolicyScriptAllowWasmEval() {
+		$expectedPolicy = "default-src 'none';base-uri 'none';manifest-src 'self';script-src  'wasm-unsafe-eval';frame-ancestors 'none'";
+
+		$this->contentSecurityPolicy->allowEvalWasm(true);
+		$this->assertSame($expectedPolicy, $this->contentSecurityPolicy->buildPolicy());
+	}
+
 	public function testGetPolicyStyleDomainValid() {
 		$expectedPolicy = "default-src 'none';base-uri 'none';manifest-src 'self';style-src www.owncloud.com;frame-ancestors 'none'";