| /* |
| * Copyright (C) 2011 Adam Barth. All Rights Reserved. |
| * Copyright (C) 2011 Daniel Bates (dbates@intudata.com). |
| * Copyright (C) 2017 Apple Inc. 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 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 "DecodeEscapeSequences.h" |
| #include "Document.h" |
| #include "DocumentLoader.h" |
| #include "FormData.h" |
| #include "Frame.h" |
| #include "FrameLoader.h" |
| #include "HTMLDocumentParser.h" |
| #include "HTMLNames.h" |
| #include "HTMLParamElement.h" |
| #include "HTMLParserIdioms.h" |
| #include "SVGNames.h" |
| #include "Settings.h" |
| #include "TextResourceDecoder.h" |
| #include "XLinkNames.h" |
| #include <wtf/ASCIICType.h> |
| #include <wtf/MainThread.h> |
| #include <wtf/NeverDestroyed.h> |
| #include <wtf/text/StringView.h> |
| |
| namespace WebCore { |
| |
| using namespace HTMLNames; |
| |
| 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. |
| // We also remove forward-slash, because it is common for some servers to collapse successive path components, eg, |
| // a//b becomes a/b. |
| // |
| // For instance: new String("http://localhost:8000") => new String("http:localhost:8"). |
| return (c == '\\' || c == '0' || c == '\0' || c == '/' || c >= 127); |
| } |
| |
| static bool isRequiredForInjection(UChar c) |
| { |
| return (c == '\'' || c == '"' || c == '<' || c == '>'); |
| } |
| |
| static bool isTerminatingCharacter(UChar c) |
| { |
| return (c == '&' || c == '/' || c == '"' || c == '\'' || c == '<' || c == '>' || c == ','); |
| } |
| |
| static bool isHTMLQuote(UChar c) |
| { |
| return (c == '"' || c == '\''); |
| } |
| |
| static bool isJSNewline(UChar c) |
| { |
| // Per ecma-262 section 7.3 Line Terminators. |
| return (c == '\n' || c == '\r' || c == 0x2028 || c == 0x2029); |
| } |
| |
| static bool startsHTMLCommentAt(const String& string, size_t start) |
| { |
| return (start + 3 < string.length() && string[start] == '<' && string[start + 1] == '!' && string[start + 2] == '-' && string[start + 3] == '-'); |
| } |
| |
| static bool startsSingleLineCommentAt(const String& string, size_t start) |
| { |
| return (start + 1 < string.length() && string[start] == '/' && string[start + 1] == '/'); |
| } |
| |
| static bool startsMultiLineCommentAt(const String& string, size_t start) |
| { |
| return (start + 1 < string.length() && string[start] == '/' && string[start + 1] == '*'); |
| } |
| |
| static bool startsOpeningScriptTagAt(const String& string, size_t start) |
| { |
| return start + 6 < string.length() && string[start] == '<' |
| && WTF::toASCIILowerUnchecked(string[start + 1]) == 's' |
| && WTF::toASCIILowerUnchecked(string[start + 2]) == 'c' |
| && WTF::toASCIILowerUnchecked(string[start + 3]) == 'r' |
| && WTF::toASCIILowerUnchecked(string[start + 4]) == 'i' |
| && WTF::toASCIILowerUnchecked(string[start + 5]) == 'p' |
| && WTF::toASCIILowerUnchecked(string[start + 6]) == 't'; |
| } |
| |
| // If other files need this, we should move this to HTMLParserIdioms.h |
| template<size_t inlineCapacity> |
| bool threadSafeMatch(const Vector<UChar, inlineCapacity>& vector, const QualifiedName& qname) |
| { |
| return equalIgnoringNullity(vector, qname.localName().impl()); |
| } |
| |
| static bool hasName(const HTMLToken& token, const QualifiedName& name) |
| { |
| return threadSafeMatch(token.name(), name); |
| } |
| |
| static bool findAttributeWithName(const HTMLToken& token, const QualifiedName& name, size_t& indexOfMatchingAttribute) |
| { |
| // Notice that we're careful not to ref the StringImpl here because we might be on a background thread. |
| const String& attrName = name.namespaceURI() == XLinkNames::xlinkNamespaceURI ? "xlink:" + name.localName().string() : name.localName().string(); |
| |
| for (size_t i = 0; i < token.attributes().size(); ++i) { |
| if (equalIgnoringNullity(token.attributes().at(i).name, attrName)) { |
| indexOfMatchingAttribute = i; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| static bool isNameOfInlineEventHandler(const Vector<UChar, 32>& name) |
| { |
| const size_t lengthOfShortestInlineEventHandlerName = 5; // To wit: oncut. |
| if (name.size() < lengthOfShortestInlineEventHandlerName) |
| return false; |
| return name[0] == 'o' && name[1] == 'n'; |
| } |
| |
| static bool isDangerousHTTPEquiv(const String& value) |
| { |
| String equiv = value.stripWhiteSpace(); |
| return equalLettersIgnoringASCIICase(equiv, "refresh") || equalLettersIgnoringASCIICase(equiv, "set-cookie"); |
| } |
| |
| static inline String decode16BitUnicodeEscapeSequences(const String& string) |
| { |
| // Note, the encoding is ignored since each %u-escape sequence represents a UTF-16 code unit. |
| return decodeEscapeSequences<Unicode16BitEscapeSequence>(string, UTF8Encoding()); |
| } |
| |
| static inline String decodeStandardURLEscapeSequences(const String& string, const TextEncoding& encoding) |
| { |
| // We use decodeEscapeSequences() instead of decodeURLEscapeSequences() (declared in URL.h) to |
| // avoid platform-specific URL decoding differences (e.g. URLGoogle). |
| return decodeEscapeSequences<URLEscapeSequence>(string, encoding); |
| } |
| |
| static String fullyDecodeString(const String& string, const TextEncoding& encoding) |
| { |
| size_t oldWorkingStringLength; |
| String workingString = string; |
| do { |
| oldWorkingStringLength = workingString.length(); |
| workingString = decode16BitUnicodeEscapeSequences(decodeStandardURLEscapeSequences(workingString, encoding)); |
| } while (workingString.length() < oldWorkingStringLength); |
| workingString.replace('+', ' '); |
| return workingString; |
| } |
| |
| static void truncateForSrcLikeAttribute(String& decodedSnippet) |
| { |
| // In HTTP URLs, characters following the first ?, #, or third slash may come from |
| // the page itself and can be merely ignored by an attacker's server when a remote |
| // script or script-like resource is requested. In data URLs, the payload starts at |
| // the first comma, and the first /*, //, or <!-- may introduce a comment. Also |
| // data URLs may use the same string literal tricks as with script content itself. |
| // In either case, content following this may come from the page and may be ignored |
| // when the script is executed. Also, any of these characters may now be represented |
| // by the (enlarged) set of HTML5 entities. |
| // For simplicity, we don't differentiate based on URL scheme, and stop at the first |
| // & (since it might be part of an entity for any of the subsequent punctuation) |
| // the first # or ?, the third slash, or the first slash, <, ', or " once a comma |
| // is seen. |
| int slashCount = 0; |
| bool commaSeen = false; |
| for (size_t currentLength = 0; currentLength < decodedSnippet.length(); ++currentLength) { |
| UChar currentChar = decodedSnippet[currentLength]; |
| if (currentChar == '&' |
| || currentChar == '?' |
| || currentChar == '#' |
| || ((currentChar == '/' || currentChar == '\\') && (commaSeen || ++slashCount > 2)) |
| || (currentChar == '<' && commaSeen) |
| || (currentChar == '\'' && commaSeen) |
| || (currentChar == '"' && commaSeen)) { |
| decodedSnippet.truncate(currentLength); |
| return; |
| } |
| if (currentChar == ',') |
| commaSeen = true; |
| } |
| } |
| |
| static void truncateForScriptLikeAttribute(String& decodedSnippet) |
| { |
| // Beware of trailing characters which came from the page itself, not the |
| // injected vector. Excluding the terminating character covers common cases |
| // where the page immediately ends the attribute, but doesn't cover more |
| // complex cases where there is other page data following the injection. |
| // Generally, these won't parse as JavaScript, so the injected vector |
| // typically excludes them from consideration via a single-line comment or |
| // by enclosing them in a string literal terminated later by the page's own |
| // closing punctuation. Since the snippet has not been parsed, the vector |
| // may also try to introduce these via entities. As a result, we'd like to |
| // stop before the first "//", the first <!--, the first entity, or the first |
| // quote not immediately following the first equals sign (taking whitespace |
| // into consideration). To keep things simpler, we don't try to distinguish |
| // between entity-introducing ampersands vs. other uses, nor do we bother to |
| // check for a second slash for a comment, nor do we bother to check for |
| // !-- following a less-than sign. We stop instead on any ampersand |
| // slash, or less-than sign. |
| size_t position = 0; |
| if ((position = decodedSnippet.find('=')) != notFound |
| && (position = decodedSnippet.find(isNotHTMLSpace, position + 1)) != notFound |
| && (position = decodedSnippet.find(isTerminatingCharacter, isHTMLQuote(decodedSnippet[position]) ? position + 1 : position)) != notFound) { |
| decodedSnippet.truncate(position); |
| } |
| } |
| |
| static bool isSemicolonSeparatedAttribute(const HTMLToken::Attribute& attribute) |
| { |
| return threadSafeMatch(attribute.name, SVGNames::valuesAttr); |
| } |
| |
| static bool semicolonSeparatedValueContainsJavaScriptURL(StringView semicolonSeparatedValue) |
| { |
| for (auto value : semicolonSeparatedValue.split(';')) { |
| if (protocolIsJavaScript(value)) |
| return true; |
| } |
| return false; |
| } |
| |
| XSSAuditor::XSSAuditor() |
| : m_isEnabled(false) |
| , m_xssProtection(XSSProtectionDisposition::Enabled) |
| , m_didSendValidXSSProtectionHeader(false) |
| , m_state(Uninitialized) |
| , m_scriptTagNestingLevel(0) |
| , m_encoding(UTF8Encoding()) |
| { |
| // Although tempting to call init() at this point, the various objects |
| // we want to reference might not all have been constructed yet. |
| } |
| |
| void XSSAuditor::initForFragment() |
| { |
| ASSERT(isMainThread()); |
| ASSERT(m_state == Uninitialized); |
| m_state = Initialized; |
| // When parsing a fragment, we don't enable the XSS auditor because it's |
| // too much overhead. |
| ASSERT(!m_isEnabled); |
| } |
| |
| void XSSAuditor::init(Document* document, XSSAuditorDelegate* auditorDelegate) |
| { |
| const size_t minimumLengthForSuffixTree = 512; // FIXME: Tune this parameter. |
| const int suffixTreeDepth = 5; |
| |
| ASSERT(isMainThread()); |
| if (m_state == Initialized) |
| return; |
| ASSERT(m_state == Uninitialized); |
| m_state = Initialized; |
| |
| if (Frame* frame = document->frame()) |
| m_isEnabled = frame->settings().xssAuditorEnabled(); |
| |
| if (!m_isEnabled) |
| return; |
| |
| m_documentURL = document->url().isolatedCopy(); |
| |
| // In theory, the Document could have detached from the Frame after the |
| // XSSAuditor was constructed. |
| if (!document->frame()) { |
| m_isEnabled = false; |
| return; |
| } |
| |
| if (m_documentURL.isEmpty()) { |
| // The URL can be empty when opening a new browser window or calling window.open(""). |
| m_isEnabled = false; |
| return; |
| } |
| |
| if (m_documentURL.protocolIsData()) { |
| m_isEnabled = false; |
| return; |
| } |
| |
| if (document->decoder()) |
| m_encoding = document->decoder()->encoding(); |
| |
| m_decodedURL = canonicalize(m_documentURL.string(), TruncationStyle::None); |
| if (m_decodedURL.find(isRequiredForInjection) == notFound) |
| m_decodedURL = String(); |
| |
| String httpBodyAsString; |
| if (DocumentLoader* documentLoader = document->frame()->loader().documentLoader()) { |
| static NeverDestroyed<String> XSSProtectionHeader(MAKE_STATIC_STRING_IMPL("X-XSS-Protection")); |
| String headerValue = documentLoader->response().httpHeaderField(XSSProtectionHeader); |
| String errorDetails; |
| unsigned errorPosition = 0; |
| String parsedReportURL; |
| URL reportURL; |
| m_xssProtection = parseXSSProtectionHeader(headerValue, errorDetails, errorPosition, parsedReportURL); |
| m_didSendValidXSSProtectionHeader = !headerValue.isNull() && m_xssProtection != XSSProtectionDisposition::Invalid; |
| |
| if ((m_xssProtection == XSSProtectionDisposition::Enabled || m_xssProtection == XSSProtectionDisposition::BlockEnabled) && !parsedReportURL.isEmpty()) { |
| reportURL = document->completeURL(parsedReportURL); |
| if (MixedContentChecker::isMixedContent(document->securityOrigin(), reportURL)) { |
| errorDetails = "insecure reporting URL for secure page"; |
| m_xssProtection = XSSProtectionDisposition::Invalid; |
| reportURL = URL(); |
| m_didSendValidXSSProtectionHeader = false; |
| } |
| } |
| if (m_xssProtection == XSSProtectionDisposition::Invalid) { |
| document->addConsoleMessage(MessageSource::Security, MessageLevel::Error, "Error parsing header X-XSS-Protection: " + headerValue + ": " + errorDetails + " at character position " + String::format("%u", errorPosition) + ". The default protections will be applied."); |
| m_xssProtection = XSSProtectionDisposition::Enabled; |
| } |
| |
| if (auditorDelegate) |
| auditorDelegate->setReportURL(reportURL.isolatedCopy()); |
| FormData* httpBody = documentLoader->originalRequest().httpBody(); |
| if (httpBody && !httpBody->isEmpty()) { |
| httpBodyAsString = httpBody->flattenToString(); |
| if (!httpBodyAsString.isEmpty()) { |
| m_decodedHTTPBody = canonicalize(httpBodyAsString, TruncationStyle::None); |
| if (m_decodedHTTPBody.find(isRequiredForInjection) == notFound) |
| m_decodedHTTPBody = String(); |
| if (m_decodedHTTPBody.length() >= minimumLengthForSuffixTree) |
| m_decodedHTTPBodySuffixTree = std::make_unique<SuffixTree<ASCIICodebook>>(m_decodedHTTPBody, suffixTreeDepth); |
| } |
| } |
| } |
| |
| if (m_decodedURL.isEmpty() && m_decodedHTTPBody.isEmpty()) { |
| m_isEnabled = false; |
| return; |
| } |
| } |
| |
| std::unique_ptr<XSSInfo> XSSAuditor::filterToken(const FilterTokenRequest& request) |
| { |
| ASSERT(m_state == Initialized); |
| if (!m_isEnabled || m_xssProtection == XSSProtectionDisposition::Disabled) |
| return nullptr; |
| |
| bool didBlockScript = false; |
| if (request.token.type() == HTMLToken::StartTag) |
| didBlockScript = filterStartToken(request); |
| else if (m_scriptTagNestingLevel) { |
| if (request.token.type() == HTMLToken::Character) |
| didBlockScript = filterCharacterToken(request); |
| else if (request.token.type() == HTMLToken::EndTag) |
| filterEndToken(request); |
| } |
| |
| if (!didBlockScript) |
| return nullptr; |
| |
| bool didBlockEntirePage = m_xssProtection == XSSProtectionDisposition::BlockEnabled; |
| return std::make_unique<XSSInfo>(m_documentURL, didBlockEntirePage, m_didSendValidXSSProtectionHeader); |
| } |
| |
| bool XSSAuditor::filterStartToken(const FilterTokenRequest& request) |
| { |
| bool didBlockScript = eraseDangerousAttributesIfInjected(request); |
| |
| if (hasName(request.token, scriptTag)) { |
| didBlockScript |= filterScriptToken(request); |
| ASSERT(request.shouldAllowCDATA || !m_scriptTagNestingLevel); |
| m_scriptTagNestingLevel++; |
| } else if (hasName(request.token, objectTag)) |
| didBlockScript |= filterObjectToken(request); |
| else if (hasName(request.token, paramTag)) |
| didBlockScript |= filterParamToken(request); |
| else if (hasName(request.token, embedTag)) |
| didBlockScript |= filterEmbedToken(request); |
| else if (hasName(request.token, appletTag)) |
| didBlockScript |= filterAppletToken(request); |
| else if (hasName(request.token, iframeTag) || hasName(request.token, frameTag)) |
| didBlockScript |= filterFrameToken(request); |
| else if (hasName(request.token, metaTag)) |
| didBlockScript |= filterMetaToken(request); |
| else if (hasName(request.token, baseTag)) |
| didBlockScript |= filterBaseToken(request); |
| else if (hasName(request.token, formTag)) |
| didBlockScript |= filterFormToken(request); |
| else if (hasName(request.token, inputTag)) |
| didBlockScript |= filterInputToken(request); |
| else if (hasName(request.token, buttonTag)) |
| didBlockScript |= filterButtonToken(request); |
| |
| return didBlockScript; |
| } |
| |
| void XSSAuditor::filterEndToken(const FilterTokenRequest& request) |
| { |
| ASSERT(m_scriptTagNestingLevel); |
| if (hasName(request.token, scriptTag)) { |
| m_scriptTagNestingLevel--; |
| ASSERT(request.shouldAllowCDATA || !m_scriptTagNestingLevel); |
| } |
| } |
| |
| bool XSSAuditor::filterCharacterToken(const FilterTokenRequest& request) |
| { |
| ASSERT(m_scriptTagNestingLevel); |
| if (m_wasScriptTagFoundInRequest && isContainedInRequest(canonicalizedSnippetForJavaScript(request))) { |
| request.token.clear(); |
| LChar space = ' '; |
| request.token.appendToCharacter(space); // Technically, character tokens can't be empty. |
| return true; |
| } |
| return false; |
| } |
| |
| bool XSSAuditor::filterScriptToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, scriptTag)); |
| |
| m_wasScriptTagFoundInRequest = isContainedInRequest(canonicalizedSnippetForTagName(request)); |
| |
| bool didBlockScript = false; |
| if (m_wasScriptTagFoundInRequest) { |
| didBlockScript |= eraseAttributeIfInjected(request, srcAttr, blankURL().string(), TruncationStyle::SrcLikeAttribute); |
| didBlockScript |= eraseAttributeIfInjected(request, XLinkNames::hrefAttr, blankURL().string(), TruncationStyle::SrcLikeAttribute); |
| } |
| |
| return didBlockScript; |
| } |
| |
| bool XSSAuditor::filterObjectToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, objectTag)); |
| |
| bool didBlockScript = false; |
| if (isContainedInRequest(canonicalizedSnippetForTagName(request))) { |
| didBlockScript |= eraseAttributeIfInjected(request, dataAttr, blankURL().string(), TruncationStyle::SrcLikeAttribute); |
| didBlockScript |= eraseAttributeIfInjected(request, typeAttr); |
| didBlockScript |= eraseAttributeIfInjected(request, classidAttr); |
| } |
| return didBlockScript; |
| } |
| |
| bool XSSAuditor::filterParamToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, paramTag)); |
| |
| size_t indexOfNameAttribute; |
| if (!findAttributeWithName(request.token, nameAttr, indexOfNameAttribute)) |
| return false; |
| |
| const HTMLToken::Attribute& nameAttribute = request.token.attributes().at(indexOfNameAttribute); |
| if (!HTMLParamElement::isURLParameter(String(nameAttribute.value))) |
| return false; |
| |
| return eraseAttributeIfInjected(request, valueAttr, blankURL().string(), TruncationStyle::SrcLikeAttribute); |
| } |
| |
| bool XSSAuditor::filterEmbedToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, embedTag)); |
| |
| bool didBlockScript = false; |
| if (isContainedInRequest(canonicalizedSnippetForTagName(request))) { |
| didBlockScript |= eraseAttributeIfInjected(request, codeAttr, String(), TruncationStyle::SrcLikeAttribute); |
| didBlockScript |= eraseAttributeIfInjected(request, srcAttr, blankURL().string(), TruncationStyle::SrcLikeAttribute); |
| didBlockScript |= eraseAttributeIfInjected(request, typeAttr); |
| } |
| return didBlockScript; |
| } |
| |
| bool XSSAuditor::filterAppletToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, appletTag)); |
| |
| bool didBlockScript = false; |
| if (isContainedInRequest(canonicalizedSnippetForTagName(request))) { |
| didBlockScript |= eraseAttributeIfInjected(request, codeAttr, String(), TruncationStyle::SrcLikeAttribute); |
| didBlockScript |= eraseAttributeIfInjected(request, objectAttr); |
| } |
| return didBlockScript; |
| } |
| |
| bool XSSAuditor::filterFrameToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, iframeTag) || hasName(request.token, frameTag)); |
| |
| bool didBlockScript = eraseAttributeIfInjected(request, srcdocAttr, String(), TruncationStyle::ScriptLikeAttribute); |
| if (isContainedInRequest(canonicalizedSnippetForTagName(request))) |
| didBlockScript |= eraseAttributeIfInjected(request, srcAttr, String(), TruncationStyle::SrcLikeAttribute); |
| |
| return didBlockScript; |
| } |
| |
| bool XSSAuditor::filterMetaToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, metaTag)); |
| |
| return eraseAttributeIfInjected(request, http_equivAttr); |
| } |
| |
| bool XSSAuditor::filterBaseToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, baseTag)); |
| |
| return eraseAttributeIfInjected(request, hrefAttr); |
| } |
| |
| bool XSSAuditor::filterFormToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, formTag)); |
| |
| return eraseAttributeIfInjected(request, actionAttr, blankURL().string()); |
| } |
| |
| bool XSSAuditor::filterInputToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, inputTag)); |
| |
| return eraseAttributeIfInjected(request, formactionAttr, blankURL().string(), TruncationStyle::SrcLikeAttribute); |
| } |
| |
| bool XSSAuditor::filterButtonToken(const FilterTokenRequest& request) |
| { |
| ASSERT(request.token.type() == HTMLToken::StartTag); |
| ASSERT(hasName(request.token, buttonTag)); |
| |
| return eraseAttributeIfInjected(request, formactionAttr, blankURL().string(), TruncationStyle::SrcLikeAttribute); |
| } |
| |
| bool XSSAuditor::eraseDangerousAttributesIfInjected(const FilterTokenRequest& request) |
| { |
| static NeverDestroyed<String> safeJavaScriptURL(MAKE_STATIC_STRING_IMPL("javascript:void(0)")); |
| |
| bool didBlockScript = false; |
| for (size_t i = 0; i < request.token.attributes().size(); ++i) { |
| const HTMLToken::Attribute& attribute = request.token.attributes().at(i); |
| bool isInlineEventHandler = isNameOfInlineEventHandler(attribute.name); |
| // FIXME: It would be better if we didn't create a new String for every attribute in the document. |
| String strippedValue = stripLeadingAndTrailingHTMLSpaces(String(attribute.value)); |
| bool valueContainsJavaScriptURL = (!isInlineEventHandler && protocolIsJavaScript(strippedValue)) || (isSemicolonSeparatedAttribute(attribute) && semicolonSeparatedValueContainsJavaScriptURL(strippedValue)); |
| if (!isInlineEventHandler && !valueContainsJavaScriptURL) |
| continue; |
| if (!isContainedInRequest(canonicalize(snippetFromAttribute(request, attribute), TruncationStyle::ScriptLikeAttribute))) |
| continue; |
| request.token.eraseValueOfAttribute(i); |
| if (valueContainsJavaScriptURL) |
| request.token.appendToAttributeValue(i, safeJavaScriptURL.get()); |
| didBlockScript = true; |
| } |
| return didBlockScript; |
| } |
| |
| bool XSSAuditor::eraseAttributeIfInjected(const FilterTokenRequest& request, const QualifiedName& attributeName, const String& replacementValue, TruncationStyle truncationStyle) |
| { |
| size_t indexOfAttribute = 0; |
| if (!findAttributeWithName(request.token, attributeName, indexOfAttribute)) |
| return false; |
| |
| const HTMLToken::Attribute& attribute = request.token.attributes().at(indexOfAttribute); |
| if (!isContainedInRequest(canonicalize(snippetFromAttribute(request, attribute), truncationStyle))) |
| return false; |
| |
| if (threadSafeMatch(attributeName, srcAttr)) { |
| if (isLikelySafeResource(String(attribute.value))) |
| return false; |
| } else if (threadSafeMatch(attributeName, http_equivAttr)) { |
| if (!isDangerousHTTPEquiv(String(attribute.value))) |
| return false; |
| } |
| |
| request.token.eraseValueOfAttribute(indexOfAttribute); |
| if (!replacementValue.isEmpty()) |
| request.token.appendToAttributeValue(indexOfAttribute, replacementValue); |
| return true; |
| } |
| |
| String XSSAuditor::canonicalizedSnippetForTagName(const FilterTokenRequest& request) |
| { |
| // Grab a fixed number of characters equal to the length of the token's name plus one (to account for the "<"). |
| return canonicalize(request.sourceTracker.source(request.token).substring(0, request.token.name().size() + 1), TruncationStyle::None); |
| } |
| |
| String XSSAuditor::snippetFromAttribute(const FilterTokenRequest& request, const HTMLToken::Attribute& attribute) |
| { |
| // The range doesn't include the character which terminates the value. So, |
| // for an input of |name="value"|, the snippet is |name="value|. For an |
| // unquoted input of |name=value |, the snippet is |name=value|. |
| // FIXME: We should grab one character before the name also. |
| return request.sourceTracker.source(request.token, attribute.startOffset, attribute.endOffset); |
| } |
| |
| String XSSAuditor::canonicalize(const String& snippet, TruncationStyle truncationStyle) |
| { |
| String decodedSnippet = fullyDecodeString(snippet, m_encoding); |
| if (truncationStyle != TruncationStyle::None) { |
| decodedSnippet.truncate(kMaximumFragmentLengthTarget); |
| if (truncationStyle == TruncationStyle::SrcLikeAttribute) |
| truncateForSrcLikeAttribute(decodedSnippet); |
| else if (truncationStyle == TruncationStyle::ScriptLikeAttribute) |
| truncateForScriptLikeAttribute(decodedSnippet); |
| } |
| return decodedSnippet.removeCharacters(&isNonCanonicalCharacter); |
| } |
| |
| String XSSAuditor::canonicalizedSnippetForJavaScript(const FilterTokenRequest& request) |
| { |
| String string = request.sourceTracker.source(request.token); |
| size_t startPosition = 0; |
| size_t endPosition = string.length(); |
| size_t foundPosition = notFound; |
| size_t lastNonSpacePosition = notFound; |
| |
| // Skip over initial comments to find start of code. |
| while (startPosition < endPosition) { |
| while (startPosition < endPosition && isHTMLSpace(string[startPosition])) |
| startPosition++; |
| |
| // Under SVG/XML rules, only HTML comment syntax matters and the parser returns |
| // these as a separate comment tokens. Having consumed whitespace, we need not look |
| // further for these. |
| if (request.shouldAllowCDATA) |
| break; |
| |
| // Under HTML rules, both the HTML and JS comment synatx matters, and the HTML |
| // comment ends at the end of the line, not with -->. |
| if (startsHTMLCommentAt(string, startPosition) || startsSingleLineCommentAt(string, startPosition)) { |
| while (startPosition < endPosition && !isJSNewline(string[startPosition])) |
| startPosition++; |
| } else if (startsMultiLineCommentAt(string, startPosition)) { |
| if (startPosition + 2 < endPosition && (foundPosition = string.find("*/", startPosition + 2)) != notFound) |
| startPosition = foundPosition + 2; |
| else |
| startPosition = endPosition; |
| } else |
| break; |
| } |
| |
| String result; |
| while (startPosition < endPosition && !result.length()) { |
| // Stop at next comment (using the same rules as above for SVG/XML vs HTML), when we encounter a comma, |
| // when we hit an opening <script> tag, or when we exceed the maximum length target. The comma rule |
| // covers a common parameter concatenation case performed by some web servers. |
| lastNonSpacePosition = notFound; |
| for (foundPosition = startPosition; foundPosition < endPosition; foundPosition++) { |
| if (!request.shouldAllowCDATA) { |
| if (startsSingleLineCommentAt(string, foundPosition) |
| || startsMultiLineCommentAt(string, foundPosition) |
| || startsHTMLCommentAt(string, foundPosition)) { |
| break; |
| } |
| } |
| if (string[foundPosition] == ',') |
| break; |
| |
| if (lastNonSpacePosition != notFound && startsOpeningScriptTagAt(string, foundPosition)) { |
| foundPosition = lastNonSpacePosition + 1; |
| break; |
| } |
| if (foundPosition > startPosition + kMaximumFragmentLengthTarget) { |
| // After hitting the length target, we can only stop at a point where we know we are |
| // not in the middle of a %-escape sequence. For the sake of simplicity, approximate |
| // not stopping inside a (possibly multiply encoded) %-escape sequence by breaking on |
| // whitespace only. We should have enough text in these cases to avoid false positives. |
| if (isHTMLSpace(string[foundPosition])) |
| break; |
| } |
| |
| if (!isHTMLSpace(string[foundPosition])) |
| lastNonSpacePosition = foundPosition; |
| } |
| |
| result = canonicalize(string.substring(startPosition, foundPosition - startPosition), TruncationStyle::None); |
| startPosition = foundPosition + 1; |
| } |
| return result; |
| } |
| |
| bool XSSAuditor::isContainedInRequest(const String& decodedSnippet) |
| { |
| if (decodedSnippet.isEmpty()) |
| return false; |
| if (m_decodedURL.find(decodedSnippet, 0, false) != notFound) |
| return true; |
| if (m_decodedHTTPBodySuffixTree && !m_decodedHTTPBodySuffixTree->mightContain(decodedSnippet)) |
| return false; |
| return m_decodedHTTPBody.find(decodedSnippet, 0, false) != notFound; |
| } |
| |
| bool XSSAuditor::isLikelySafeResource(const String& url) |
| { |
| // Give empty URLs and about:blank a pass. Making a resourceURL from an |
| // empty string below will likely later fail the "no query args test" as |
| // it inherits the document's query args. |
| if (url.isEmpty() || url == blankURL().string()) |
| return true; |
| |
| // If the resource is loaded from the same host as the enclosing page, it's |
| // probably not an XSS attack, so we reduce false positives by allowing the |
| // request, ignoring scheme and port considerations. 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. |
| if (m_documentURL.host().isEmpty()) |
| return false; |
| |
| URL resourceURL(m_documentURL, url); |
| return (m_documentURL.host() == resourceURL.host() && resourceURL.query().isEmpty()); |
| } |
| |
| } // namespace WebCore |
