/*
* Copyright (C) 2008, 2009 Daniel Bates (dbates@intudata.com)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "XSSAuditor.h"
#include <wtf/StdLibExtras.h>
#include <wtf/Vector.h>
#include "Console.h"
#include "CString.h"
#include "DocumentLoader.h"
#include "DOMWindow.h"
#include "Frame.h"
#include "KURL.h"
#include "PreloadScanner.h"
#include "ResourceResponseBase.h"
#include "ScriptSourceCode.h"
#include "Settings.h"
#include "TextResourceDecoder.h"
using namespace WTF;
namespace WebCore {
static bool isNonCanonicalCharacter(UChar c)
{
// We remove all non-ASCII characters, including non-printable ASCII characters.
//
// Note, we don't remove backslashes like PHP stripslashes(), which among other things converts "\\0" to the \0 character.
// Instead, we remove backslashes and zeros (since the string "\\0" =(remove backslashes)=> "0"). However, this has the
// adverse effect that we remove any legitimate zeros from a string.
//
// For instance: new String("http://localhost:8000") => new String("http://localhost:8").
return (c == '\\' || c == '0' || c < ' ' || c >= 127);
}
static bool isIllegalURICharacter(UChar c)
{
// The characters described in section 2.4.3 of RFC 2396 <http://www.faqs.org/rfcs/rfc2396.html> in addition to the
// single quote character "'" are considered illegal URI characters. That is, the following characters cannot appear
// in a valid URI: ', ", <, >
//
// If the request does not contain these characters then we can assume that no inline scripts have been injected
// into the response page, because it is impossible to write an inline script of the form <script>...</script>
// without "<", ">".
return (c == '\'' || c == '"' || c == '<' || c == '>');
}
String XSSAuditor::CachingURLCanonicalizer::canonicalizeURL(const String& url, const TextEncoding& encoding, bool decodeEntities,
bool decodeURLEscapeSequencesTwice)
{
if (decodeEntities == m_decodeEntities && decodeURLEscapeSequencesTwice == m_decodeURLEscapeSequencesTwice
&& encoding == m_encoding && url == m_inputURL)
return m_cachedCanonicalizedURL;
m_cachedCanonicalizedURL = canonicalize(decodeURL(url, encoding, decodeEntities, decodeURLEscapeSequencesTwice));
m_inputURL = url;
m_encoding = encoding;
m_decodeEntities = decodeEntities;
m_decodeURLEscapeSequencesTwice = decodeURLEscapeSequencesTwice;
return m_cachedCanonicalizedURL;
}
XSSAuditor::XSSAuditor(Frame* frame)
: m_frame(frame)
{
}
XSSAuditor::~XSSAuditor()
{
}
bool XSSAuditor::isEnabled() const
{
Settings* settings = m_frame->settings();
return (settings && settings->xssAuditorEnabled());
}
bool XSSAuditor::canEvaluate(const String& code) const
{
if (!isEnabled())
return true;
FindTask task;
task.string = code;
task.decodeEntities = false;
task.allowRequestIfNoIllegalURICharacters = true;
if (findInRequest(task)) {
DEFINE_STATIC_LOCAL(String, consoleMessage, ("Refused to execute a JavaScript script. Source code of script found within request.\n"));
m_frame->domWindow()->console()->addMessage(JSMessageSource, LogMessageType, ErrorMessageLevel, consoleMessage, 1, String());
return false;
}
return true;
}
bool XSSAuditor::canEvaluateJavaScriptURL(const String& code) const
{
if (!isEnabled())
return true;
FindTask task;
task.string = code;
task.decodeURLEscapeSequencesTwice = true;
if (findInRequest(task)) {
DEFINE_STATIC_LOCAL(String, consoleMessage, ("Refused to execute a JavaScript script. Source code of script found within request.\n"));
m_frame->domWindow()->console()->addMessage(JSMessageSource, LogMessageType, ErrorMessageLevel, consoleMessage, 1, String());
return false;
}
return true;
}
bool XSSAuditor::canCreateInlineEventListener(const String&, const String& code) const
{
if (!isEnabled())
return true;
FindTask task;
task.string = code;
task.allowRequestIfNoIllegalURICharacters = true;
if (findInRequest(task)) {
DEFINE_STATIC_LOCAL(String, consoleMessage, ("Refused to execute a JavaScript script. Source code of script found within request.\n"));
m_frame->domWindow()->console()->addMessage(JSMessageSource, LogMessageType, ErrorMessageLevel, consoleMessage, 1, String());
return false;
}
return true;
}
bool XSSAuditor::canLoadExternalScriptFromSrc(const String& context, const String& url) const
{
if (!isEnabled())
return true;
if (isSameOriginResource(url))
return true;
FindTask task;
task.context = context;
task.string = url;
if (findInRequest(task)) {
DEFINE_STATIC_LOCAL(String, consoleMessage, ("Refused to execute a JavaScript script. Source code of script found within request.\n"));
m_frame->domWindow()->console()->addMessage(JSMessageSource, LogMessageType, ErrorMessageLevel, consoleMessage, 1, String());
return false;
}
return true;
}
bool XSSAuditor::canLoadObject(const String& url) const
{
if (!isEnabled())
return true;
if (isSameOriginResource(url))
return true;
FindTask task;
task.string = url;
task.allowRequestIfNoIllegalURICharacters = true;
if (findInRequest(task)) {
String consoleMessage = String::format("Refused to load an object. URL found within request: \"%s\".\n", url.utf8().data());
m_frame->domWindow()->console()->addMessage(JSMessageSource, LogMessageType, ErrorMessageLevel, consoleMessage, 1, String());
return false;
}
return true;
}
bool XSSAuditor::canSetBaseElementURL(const String& url) const
{
if (!isEnabled())
return true;
if (isSameOriginResource(url))
return true;
FindTask task;
task.string = url;
task.allowRequestIfNoIllegalURICharacters = true;
if (findInRequest(task)) {
DEFINE_STATIC_LOCAL(String, consoleMessage, ("Refused to load from document base URL. URL found within request.\n"));
m_frame->domWindow()->console()->addMessage(JSMessageSource, LogMessageType, ErrorMessageLevel, consoleMessage, 1, String());
return false;
}
return true;
}
String XSSAuditor::canonicalize(const String& string)
{
String result = decodeHTMLEntities(string);
return result.removeCharacters(&isNonCanonicalCharacter);
}
String XSSAuditor::decodeURL(const String& string, const TextEncoding& encoding, bool decodeEntities, bool decodeURLEscapeSequencesTwice)
{
String result;
String url = string;
url.replace('+', ' ');
result = decodeURLEscapeSequences(url);
CString utf8Url = result.utf8();
String decodedResult = encoding.decode(utf8Url.data(), utf8Url.length());
if (!decodedResult.isEmpty())
result = decodedResult;
if (decodeURLEscapeSequencesTwice) {
result = decodeURLEscapeSequences(result);
utf8Url = result.utf8();
decodedResult = encoding.decode(utf8Url.data(), utf8Url.length());
if (!decodedResult.isEmpty())
result = decodedResult;
}
if (decodeEntities)
result = decodeHTMLEntities(result);
return result;
}
String XSSAuditor::decodeHTMLEntities(const String& string, bool leaveUndecodableEntitiesUntouched)
{
SegmentedString source(string);
SegmentedString sourceShadow;
Vector<UChar> result;
while (!source.isEmpty()) {
UChar cc = *source;
source.advance();
if (cc != '&') {
result.append(cc);
continue;
}
if (leaveUndecodableEntitiesUntouched)
sourceShadow = source;
bool notEnoughCharacters = false;
unsigned entity = PreloadScanner::consumeEntity(source, notEnoughCharacters);
// We ignore notEnoughCharacters because we might as well use this loop
// to copy the remaining characters into |result|.
if (entity > 0xFFFF) {
result.append(U16_LEAD(entity));
result.append(U16_TRAIL(entity));
} else if (entity && (!leaveUndecodableEntitiesUntouched || entity != 0xFFFD)){
result.append(entity);
} else {
result.append('&');
if (leaveUndecodableEntitiesUntouched)
source = sourceShadow;
}
}
return String::adopt(result);
}
bool XSSAuditor::isSameOriginResource(const String& url) const
{
// If the resource is loaded from the same URL as the enclosing page, it's
// probably not an XSS attack, so we reduce false positives by allowing the
// request. If the resource has a query string, we're more suspicious,
// however, because that's pretty rare and the attacker might be able to
// trick a server-side script into doing something dangerous with the query
// string.
KURL resourceURL(m_frame->document()->url(), url);
return (m_frame->document()->url().host() == resourceURL.host() && resourceURL.query().isEmpty());
}
bool XSSAuditor::shouldFullPageBlockForXSSProtectionHeader() const
{
// If we detect an XSS attack and find the HTTP header "X-XSS-Protection: 12" then
// we will stop loading the page as opposed to ignoring the script. The value "12"
// came from a personal communication, see <https://bugs.webkit.org/show_bug.cgi?id=27312>
// for more details.
DEFINE_STATIC_LOCAL(String, XSSProtectionHeader, ("X-XSS-Protection"));
Frame* frame = m_frame;
if (frame->document()->url() == blankURL())
frame = m_frame->tree()->parent();
// We strip any whitespace characters to conform to the behavior in Internet Explorer.
String xssProtectionValue = frame->loader()->documentLoader()->response().httpHeaderField(XSSProtectionHeader).stripWhiteSpace();
return (xssProtectionValue.length() >= 2 && xssProtectionValue[0] == '1' && xssProtectionValue[1] == '2');
}
bool XSSAuditor::findInRequest(const FindTask& task) const
{
bool result = false;
Frame* parentFrame = m_frame->tree()->parent();
Frame* blockFrame = parentFrame;
if (parentFrame && m_frame->document()->url() == blankURL())
result = findInRequest(parentFrame, task);
if (!result) {
result = findInRequest(m_frame, task);
blockFrame = m_frame;
}
if (result && blockFrame && shouldFullPageBlockForXSSProtectionHeader()) {
blockFrame->loader()->stopAllLoaders();
blockFrame->redirectScheduler()->scheduleLocationChange(blankURL(), String());
}
return result;
}
bool XSSAuditor::findInRequest(Frame* frame, const FindTask& task) const
{
ASSERT(frame->document());
if (!frame->document()->decoder()) {
// Note, JavaScript URLs do not have a charset.
return false;
}
if (task.string.isEmpty())
return false;
FormData* formDataObj = frame->loader()->documentLoader()->originalRequest().httpBody();
const bool hasFormData = formDataObj && !formDataObj->isEmpty();
String pageURL = frame->document()->url().string();
String canonicalizedString;
if (!hasFormData && task.string.length() > 2 * pageURL.length()) {
// Q: Why do we bother to do this check at all?
// A: Canonicalizing large inline scripts can be expensive. We want to
// reduce the size of the string before we call canonicalize below,
// since it could result in an unneeded allocation and memcpy.
//
// Q: Why do we multiply by two here?
// A: We attempt to detect reflected XSS even when the server
// transforms the attacker's input with addSlashes. The best the
// attacker can do get the server to inflate his/her input by a
// factor of two by sending " characters, which the server
// transforms to \".
canonicalizedString = task.string.substring(0, 2 * pageURL.length());
} else
canonicalizedString = task.string;
if (frame->document()->url().protocolIs("data"))
return false;
canonicalizedString = canonicalize(canonicalizedString);
if (canonicalizedString.isEmpty())
return false;
if (!task.context.isEmpty())
canonicalizedString = task.context + canonicalizedString;
String decodedPageURL = m_cache.canonicalizeURL(pageURL, frame->document()->decoder()->encoding(), task.decodeEntities, task.decodeURLEscapeSequencesTwice);
if (task.allowRequestIfNoIllegalURICharacters && !hasFormData && decodedPageURL.find(&isIllegalURICharacter, 0) == -1)
return false; // Injection is impossible because the request does not contain any illegal URI characters.
if (decodedPageURL.find(canonicalizedString, 0, false) != -1)
return true; // We've found the string in the GET data.
if (hasFormData) {
String decodedFormData = m_cache.canonicalizeURL(formDataObj->flattenToString(), frame->document()->decoder()->encoding(), task.decodeEntities, task.decodeURLEscapeSequencesTwice);
if (decodedFormData.find(canonicalizedString, 0, false) != -1)
return true; // We found the string in the POST data.
}
return false;
}
} // namespace WebCore