| // 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(user): 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). |
| * |
| * Note that the returned value does not necessarily correspond to the string |
| * with which the SafeUrl was constructed, since goog.html.SafeUrl.sanitize |
| * will percent-encode many characters. |
| * |
| * @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 types that can have SafeUrls created from |
| * URL.createObjectURL(blob). Only matches image types, currently. |
| * @const |
| * @private |
| */ |
| goog.html.SAFE_BLOB_TYPE_PATTERN_ = |
| /^image\/(?:bmp|gif|jpeg|jpg|png|tiff|webp)$/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 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_BLOB_TYPE_PATTERN_.test(blob.type) ? |
| goog.fs.url.createObjectUrl(blob) : goog.html.SafeUrl.INNOCUOUS_STRING; |
| return goog.html.SafeUrl.createSafeUrlSecurityPrivateDoNotAccessOrElse(url); |
| }; |
| |
| |
| /** |
| * 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. "http" for "http". |
| * It also disallows HTML entities in the first path part of a relative path, |
| * e.g. "foo<bar/baz". Our existing escaping functions should not produce |
| * that. More importantly, it disallows masking of a colon, |
| * e.g. "javascript:...". |
| * |
| * @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; |
| } else { |
| url = goog.html.SafeUrl.normalize_(url); |
| } |
| return goog.html.SafeUrl.createSafeUrlSecurityPrivateDoNotAccessOrElse(url); |
| }; |
| |
| |
| /** |
| * Normalizes {@code url} the UTF-8 encoding of url, using a whitelist of |
| * characters. Whitelisted characters are not percent-encoded. |
| * @param {string} url The URL to normalize. |
| * @return {string} The normalized URL. |
| * @private |
| */ |
| goog.html.SafeUrl.normalize_ = function(url) { |
| try { |
| var normalized = encodeURI(url); |
| } catch (e) { // Happens if url contains invalid surrogate sequences. |
| return goog.html.SafeUrl.INNOCUOUS_STRING; |
| } |
| |
| return normalized.replace( |
| goog.html.SafeUrl.NORMALIZE_MATCHER_, |
| function(match) { |
| return goog.html.SafeUrl.NORMALIZE_REPLACER_MAP_[match]; |
| }); |
| }; |
| |
| |
| /** |
| * Matches characters and strings which need to be replaced in the string |
| * generated by encodeURI. Specifically: |
| * |
| * - '\'', '(' and ')' are not encoded. They are part of the reserved |
| * characters group in RFC 3986 but only appear in the obsolete mark |
| * production in Appendix D.2 of RFC 3986, so they can be encoded without |
| * changing semantics. |
| * - '[' and ']' are encoded by encodeURI, despite being reserved characters |
| * which can be used to represent IPv6 addresses. So they need to be decoded. |
| * - '%' is encoded by encodeURI. However, encoding '%' characters that are |
| * already part of a valid percent-encoded sequence changes the semantics of a |
| * URL, and hence we need to preserve them. Note that this may allow |
| * non-encoded '%' characters to remain in the URL (i.e., occurrences of '%' |
| * that are not part of a valid percent-encoded sequence, for example, |
| * 'ab%xy'). |
| * |
| * @const {!RegExp} |
| * @private |
| */ |
| goog.html.SafeUrl.NORMALIZE_MATCHER_ = /[()']|%5B|%5D|%25/g; |
| |
| |
| /** |
| * Map of replacements to be done in string generated by encodeURI. |
| * @const {!Object<string, string>} |
| * @private |
| */ |
| goog.html.SafeUrl.NORMALIZE_REPLACER_MAP_ = { |
| '\'': '%27', |
| '(': '%28', |
| ')': '%29', |
| '%5B': '[', |
| '%5D': ']', |
| '%25': '%' |
| }; |
| |
| |
| /** |
| * 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; |
| }; |