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third_party/google_input_tools/third_party/closure_library/closure/goog/html/safeurl.js

Index: third_party/google_input_tools/third_party/closure_library/closure/goog/html/safeurl.js
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+// Copyright 2013 The Closure Library Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS-IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/**
+ * @fileoverview The SafeUrl type and its builders.
+ *
+ * TODO(xtof): Link to document stating type contract.
+ */
+
+goog.provide('goog.html.SafeUrl');
+
+goog.require('goog.asserts');
+goog.require('goog.fs.url');
+goog.require('goog.i18n.bidi.Dir');
+goog.require('goog.i18n.bidi.DirectionalString');
+goog.require('goog.string.Const');
+goog.require('goog.string.TypedString');
+
+
+
+/**
+ * A string that is safe to use in URL context in DOM APIs and HTML documents.
+ *
+ * A SafeUrl is a string-like object that carries the security type contract
+ * that its value as a string will not cause untrusted script execution
+ * when evaluated as a hyperlink URL in a browser.
+ *
+ * Values of this type are guaranteed to be safe to use in URL/hyperlink
+ * contexts, such as, assignment to URL-valued DOM properties, or
+ * interpolation into a HTML template in URL context (e.g., inside a href
+ * attribute), in the sense that the use will not result in a
+ * Cross-Site-Scripting vulnerability.
+ *
+ * Note that, as documented in {@code goog.html.SafeUrl.unwrap}, this type's
+ * contract does not guarantee that instances are safe to interpolate into HTML
+ * without appropriate escaping.
+ *
+ * Note also that this type's contract does not imply any guarantees regarding
+ * the resource the URL refers to.  In particular, SafeUrls are <b>not</b>
+ * safe to use in a context where the referred-to resource is interpreted as
+ * trusted code, e.g., as the src of a script tag.
+ *
+ * Instances of this type must be created via the factory methods
+ * ({@code goog.html.SafeUrl.fromConstant}, {@code goog.html.SafeUrl.sanitize}),
+ * etc and not by invoking its constructor.  The constructor intentionally
+ * takes no parameters and the type is immutable; hence only a default instance
+ * corresponding to the empty string can be obtained via constructor invocation.
+ *
+ * @see goog.html.SafeUrl#fromConstant
+ * @see goog.html.SafeUrl#from
+ * @see goog.html.SafeUrl#sanitize
+ * @constructor
+ * @final
+ * @struct
+ * @implements {goog.i18n.bidi.DirectionalString}
+ * @implements {goog.string.TypedString}
+ */
+goog.html.SafeUrl = function() {
+  /**
+   * The contained value of this SafeUrl.  The field has a purposely ugly
+   * name to make (non-compiled) code that attempts to directly access this
+   * field stand out.
+   * @private {string}
+   */
+  this.privateDoNotAccessOrElseSafeHtmlWrappedValue_ = '';
+
+  /**
+   * A type marker used to implement additional run-time type checking.
+   * @see goog.html.SafeUrl#unwrap
+   * @const
+   * @private
+   */
+  this.SAFE_URL_TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ =
+      goog.html.SafeUrl.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_;
+};
+
+
+/**
+ * The innocuous string generated by goog.html.SafeUrl.sanitize when passed
+ * an unsafe URL.
+ *
+ * about:invalid is registered in
+ * http://www.w3.org/TR/css3-values/#about-invalid.
+ * http://tools.ietf.org/html/rfc6694#section-2.2.1 permits about URLs to
+ * contain a fragment, which is not to be considered when determining if an
+ * about URL is well-known.
+ *
+ * Using about:invalid seems preferable to using a fixed data URL, since
+ * browsers might choose to not report CSP violations on it, as legitimate
+ * CSS function calls to attr() can result in this URL being produced. It is
+ * also a standard URL which matches exactly the semantics we need:
+ * "The about:invalid URI references a non-existent document with a generic
+ * error condition. It can be used when a URI is necessary, but the default
+ * value shouldn't be resolveable as any type of document".
+ *
+ * @const {string}
+ */
+goog.html.SafeUrl.INNOCUOUS_STRING = 'about:invalid#zClosurez';
+
+
+/**
+ * @override
+ * @const
+ */
+goog.html.SafeUrl.prototype.implementsGoogStringTypedString = true;
+
+
+/**
+ * Returns this SafeUrl's value a string.
+ *
+ * IMPORTANT: In code where it is security relevant that an object's type is
+ * indeed {@code SafeUrl}, use {@code goog.html.SafeUrl.unwrap} instead of this
+ * method. If in doubt, assume that it's security relevant. In particular, note
+ * that goog.html functions which return a goog.html type do not guarantee that
+ * the returned instance is of the right type. For example:
+ *
+ * <pre>
+ * var fakeSafeHtml = new String('fake');
+ * fakeSafeHtml.__proto__ = goog.html.SafeHtml.prototype;
+ * var newSafeHtml = goog.html.SafeHtml.htmlEscape(fakeSafeHtml);
+ * // newSafeHtml is just an alias for fakeSafeHtml, it's passed through by
+ * // goog.html.SafeHtml.htmlEscape() as fakeSafeHtml instanceof
+ * // goog.html.SafeHtml.
+ * </pre>
+ *
+ * IMPORTANT: The guarantees of the SafeUrl type contract only extend to the
+ * behavior of browsers when interpreting URLs. Values of SafeUrl objects MUST
+ * be appropriately escaped before embedding in a HTML document. Note that the
+ * required escaping is context-sensitive (e.g. a different escaping is
+ * required for embedding a URL in a style property within a style
+ * attribute, as opposed to embedding in a href attribute).
+ *
+ * @see goog.html.SafeUrl#unwrap
+ * @override
+ */
+goog.html.SafeUrl.prototype.getTypedStringValue = function() {
+  return this.privateDoNotAccessOrElseSafeHtmlWrappedValue_;
+};
+
+
+/**
+ * @override
+ * @const
+ */
+goog.html.SafeUrl.prototype.implementsGoogI18nBidiDirectionalString = true;
+
+
+/**
+ * Returns this URLs directionality, which is always {@code LTR}.
+ * @override
+ */
+goog.html.SafeUrl.prototype.getDirection = function() {
+  return goog.i18n.bidi.Dir.LTR;
+};
+
+
+if (goog.DEBUG) {
+  /**
+   * Returns a debug string-representation of this value.
+   *
+   * To obtain the actual string value wrapped in a SafeUrl, use
+   * {@code goog.html.SafeUrl.unwrap}.
+   *
+   * @see goog.html.SafeUrl#unwrap
+   * @override
+   */
+  goog.html.SafeUrl.prototype.toString = function() {
+    return 'SafeUrl{' + this.privateDoNotAccessOrElseSafeHtmlWrappedValue_ +
+        '}';
+  };
+}
+
+
+/**
+ * Performs a runtime check that the provided object is indeed a SafeUrl
+ * object, and returns its value.
+ *
+ * IMPORTANT: The guarantees of the SafeUrl type contract only extend to the
+ * behavior of  browsers when interpreting URLs. Values of SafeUrl objects MUST
+ * be appropriately escaped before embedding in a HTML document. Note that the
+ * required escaping is context-sensitive (e.g. a different escaping is
+ * required for embedding a URL in a style property within a style
+ * attribute, as opposed to embedding in a href attribute).
+ *
+ * @param {!goog.html.SafeUrl} safeUrl The object to extract from.
+ * @return {string} The SafeUrl object's contained string, unless the run-time
+ *     type check fails. In that case, {@code unwrap} returns an innocuous
+ *     string, or, if assertions are enabled, throws
+ *     {@code goog.asserts.AssertionError}.
+ */
+goog.html.SafeUrl.unwrap = function(safeUrl) {
+  // Perform additional Run-time type-checking to ensure that safeUrl is indeed
+  // an instance of the expected type.  This provides some additional protection
+  // against security bugs due to application code that disables type checks.
+  // Specifically, the following checks are performed:
+  // 1. The object is an instance of the expected type.
+  // 2. The object is not an instance of a subclass.
+  // 3. The object carries a type marker for the expected type. "Faking" an
+  // object requires a reference to the type marker, which has names intended
+  // to stand out in code reviews.
+  if (safeUrl instanceof goog.html.SafeUrl &&
+      safeUrl.constructor === goog.html.SafeUrl &&
+      safeUrl.SAFE_URL_TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ ===
+          goog.html.SafeUrl.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_) {
+    return safeUrl.privateDoNotAccessOrElseSafeHtmlWrappedValue_;
+  } else {
+    goog.asserts.fail('expected object of type SafeUrl, got \'' +
+                      safeUrl + '\'');
+    return 'type_error:SafeUrl';
+
+  }
+};
+
+
+/**
+ * Creates a SafeUrl object from a compile-time constant string.
+ *
+ * Compile-time constant strings are inherently program-controlled and hence
+ * trusted.
+ *
+ * @param {!goog.string.Const} url A compile-time-constant string from which to
+ *         create a SafeUrl.
+ * @return {!goog.html.SafeUrl} A SafeUrl object initialized to {@code url}.
+ */
+goog.html.SafeUrl.fromConstant = function(url) {
+  return goog.html.SafeUrl.createSafeUrlSecurityPrivateDoNotAccessOrElse(
+      goog.string.Const.unwrap(url));
+};
+
+
+/**
+ * A pattern that matches Blob or data types that can have SafeUrls created
+ * from URL.createObjectURL(blob) or via a data: URI.  Only matches image and
+ * video types, currently.
+ * @const
+ * @private
+ */
+goog.html.SAFE_MIME_TYPE_PATTERN_ =
+    /^(?:image\/(?:bmp|gif|jpeg|jpg|png|tiff|webp)|video\/(?:mpeg|mp4|ogg|webm))$/i;
+
+
+/**
+ * Creates a SafeUrl wrapping a blob URL for the given {@code blob}.
+ *
+ * The blob URL is created with {@code URL.createObjectURL}. If the MIME type
+ * for {@code blob} is not of a known safe image or video MIME type, then the
+ * SafeUrl will wrap {@link #INNOCUOUS_STRING}.
+ *
+ * @see http://www.w3.org/TR/FileAPI/#url
+ * @param {!Blob} blob
+ * @return {!goog.html.SafeUrl} The blob URL, or an innocuous string wrapped
+ *   as a SafeUrl.
+ */
+goog.html.SafeUrl.fromBlob = function(blob) {
+  var url = goog.html.SAFE_MIME_TYPE_PATTERN_.test(blob.type) ?
+      goog.fs.url.createObjectUrl(blob) : goog.html.SafeUrl.INNOCUOUS_STRING;
+  return goog.html.SafeUrl.createSafeUrlSecurityPrivateDoNotAccessOrElse(url);
+};
+
+
+/**
+ * Matches a base-64 data URL, with the first match group being the MIME type.
+ * @const
+ * @private
+ */
+goog.html.DATA_URL_PATTERN_ = /^data:([^;,]*);base64,[a-z0-9+\/]+=*$/i;
+
+
+/**
+ * Creates a SafeUrl wrapping a data: URL, after validating it matches a
+ * known-safe image or video MIME type.
+ *
+ * @param {string} dataUrl A valid base64 data URL with one of the whitelisted
+ *     image or video MIME types.
+ * @return {!goog.html.SafeUrl} A matching safe URL, or {@link INNOCUOUS_STRING}
+ *     wrapped as a SafeUrl if it does not pass.
+ */
+goog.html.SafeUrl.fromDataUrl = function(dataUrl) {
+  // There's a slight risk here that a browser sniffs the content type if it
+  // doesn't know the MIME type and executes HTML within the data: URL. For this
+  // to cause XSS it would also have to execute the HTML in the same origin
+  // of the page with the link. It seems unlikely that both of these will
+  // happen, particularly in not really old IEs.
+  var match = dataUrl.match(goog.html.DATA_URL_PATTERN_);
+  var valid = match && goog.html.SAFE_MIME_TYPE_PATTERN_.test(match[1]);
+  return goog.html.SafeUrl.createSafeUrlSecurityPrivateDoNotAccessOrElse(
+      valid ? dataUrl : goog.html.SafeUrl.INNOCUOUS_STRING);
+};
+
+
+/**
+ * A pattern that recognizes a commonly useful subset of URLs that satisfy
+ * the SafeUrl contract.
+ *
+ * This regular expression matches a subset of URLs that will not cause script
+ * execution if used in URL context within a HTML document. Specifically, this
+ * regular expression matches if (comment from here on and regex copied from
+ * Soy's EscapingConventions):
+ * (1) Either a protocol in a whitelist (http, https, mailto or ftp).
+ * (2) or no protocol.  A protocol must be followed by a colon. The below
+ *     allows that by allowing colons only after one of the characters [/?#].
+ *     A colon after a hash (#) must be in the fragment.
+ *     Otherwise, a colon after a (?) must be in a query.
+ *     Otherwise, a colon after a single solidus (/) must be in a path.
+ *     Otherwise, a colon after a double solidus (//) must be in the authority
+ *     (before port).
+ *
+ * The pattern disallows &, used in HTML entity declarations before
+ * one of the characters in [/?#]. This disallows HTML entities used in the
+ * protocol name, which should never happen, e.g. "h&#116;tp" for "http".
+ * It also disallows HTML entities in the first path part of a relative path,
+ * e.g. "foo&lt;bar/baz".  Our existing escaping functions should not produce
+ * that. More importantly, it disallows masking of a colon,
+ * e.g. "javascript&#58;...".
+ *
+ * @private
+ * @const {!RegExp}
+ */
+goog.html.SAFE_URL_PATTERN_ =
+    /^(?:(?:https?|mailto|ftp):|[^&:/?#]*(?:[/?#]|$))/i;
+
+
+/**
+ * Creates a SafeUrl object from {@code url}. If {@code url} is a
+ * goog.html.SafeUrl then it is simply returned. Otherwise the input string is
+ * validated to match a pattern of commonly used safe URLs. The string is
+ * converted to UTF-8 and non-whitelisted characters are percent-encoded. The
+ * string wrapped by the created SafeUrl will thus contain only ASCII printable
+ * characters.
+ *
+ * {@code url} may be a URL with the http, https, mailto or ftp scheme,
+ * or a relative URL (i.e., a URL without a scheme; specifically, a
+ * scheme-relative, absolute-path-relative, or path-relative URL).
+ *
+ * {@code url} is converted to UTF-8 and non-whitelisted characters are
+ * percent-encoded. Whitelisted characters are '%' and, from RFC 3986,
+ * unreserved characters and reserved characters, with the exception of '\'',
+ * '(' and ')'. This ensures the the SafeUrl contains only ASCII-printable
+ * characters and reduces the chance of security bugs were it to be
+ * interpolated into a specific context without the necessary escaping.
+ *
+ * If {@code url} fails validation or does not UTF-16 decode correctly
+ * (JavaScript strings are UTF-16 encoded), this function returns a SafeUrl
+ * object containing an innocuous string, goog.html.SafeUrl.INNOCUOUS_STRING.
+ *
+ * @see http://url.spec.whatwg.org/#concept-relative-url
+ * @param {string|!goog.string.TypedString} url The URL to validate.
+ * @return {!goog.html.SafeUrl} The validated URL, wrapped as a SafeUrl.
+ */
+goog.html.SafeUrl.sanitize = function(url) {
+  if (url instanceof goog.html.SafeUrl) {
+    return url;
+  }
+  else if (url.implementsGoogStringTypedString) {
+    url = url.getTypedStringValue();
+  } else {
+    url = String(url);
+  }
+  if (!goog.html.SAFE_URL_PATTERN_.test(url)) {
+    url = goog.html.SafeUrl.INNOCUOUS_STRING;
+  }
+  return goog.html.SafeUrl.createSafeUrlSecurityPrivateDoNotAccessOrElse(url);
+};
+
+
+/**
+ * Type marker for the SafeUrl type, used to implement additional run-time
+ * type checking.
+ * @const
+ * @private
+ */
+goog.html.SafeUrl.TYPE_MARKER_GOOG_HTML_SECURITY_PRIVATE_ = {};
+
+
+/**
+ * Package-internal utility method to create SafeUrl instances.
+ *
+ * @param {string} url The string to initialize the SafeUrl object with.
+ * @return {!goog.html.SafeUrl} The initialized SafeUrl object.
+ * @package
+ */
+goog.html.SafeUrl.createSafeUrlSecurityPrivateDoNotAccessOrElse = function(
+    url) {
+  var safeUrl = new goog.html.SafeUrl();
+  safeUrl.privateDoNotAccessOrElseSafeHtmlWrappedValue_ = url;
+  return safeUrl;
+};