/*
 * Copyright (C) 2008-2021 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
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
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 */

#include "config.h"
#include "CrossOriginAccessControl.h"

#include "CachedResourceRequest.h"
#include "CrossOriginEmbedderPolicy.h"
#include "CrossOriginPreflightResultCache.h"
#include "DocumentLoader.h"
#include "HTTPHeaderNames.h"
#include "HTTPParsers.h"
#include "LegacySchemeRegistry.h"
#include "OriginAccessPatterns.h"
#include "Page.h"
#include "ResourceRequest.h"
#include "RuntimeApplicationChecks.h"
#include "SecurityOrigin.h"
#include "SecurityPolicy.h"
#include <mutex>
#include <wtf/NeverDestroyed.h>
#include <wtf/text/AtomString.h>
#include <wtf/text/MakeString.h>
#include <wtf/text/StringBuilder.h>

namespace WebCore {

bool isOnAccessControlSimpleRequestMethodAllowlist(const String& method)
{
    return method == "GET"_s || method == "HEAD"_s || method == "POST"_s;
}

bool isSimpleCrossOriginAccessRequest(const String& method, const HTTPHeaderMap& headerMap)
{
    if (!isOnAccessControlSimpleRequestMethodAllowlist(method))
        return false;

    for (const auto& header : headerMap) {
        if (!header.keyAsHTTPHeaderName || !isCrossOriginSafeRequestHeader(header.keyAsHTTPHeaderName.value(), header.value))
            return false;
    }

    return true;
}

void updateRequestReferrer(ResourceRequest& request, ReferrerPolicy referrerPolicy, const URL& outgoingReferrerURL, const OriginAccessPatterns& patterns)
{
    String newOutgoingReferrer = SecurityPolicy::generateReferrerHeader(referrerPolicy, request.url(), outgoingReferrerURL, patterns);
    if (newOutgoingReferrer.isEmpty())
        request.clearHTTPReferrer();
    else
        request.setHTTPReferrer(newOutgoingReferrer);
}

void updateRequestForAccessControl(ResourceRequest& request, SecurityOrigin& securityOrigin, StoredCredentialsPolicy storedCredentialsPolicy)
{
    request.removeCredentials();
    if (request.allowCookies())
        request.setAllowCookies(storedCredentialsPolicy == StoredCredentialsPolicy::Use);
    request.setHTTPOrigin(securityOrigin.toString());
}

ResourceRequest createAccessControlPreflightRequest(const ResourceRequest& request, SecurityOrigin& securityOrigin, const String& referrer, bool includeFetchMetadata)
{
    ResourceRequest preflightRequest(request.url());
    static const double platformDefaultTimeout = 0;
    preflightRequest.setTimeoutInterval(platformDefaultTimeout);
    updateRequestForAccessControl(preflightRequest, securityOrigin, StoredCredentialsPolicy::DoNotUse);
    preflightRequest.setHTTPMethod("OPTIONS"_s);
    preflightRequest.setHTTPHeaderField(HTTPHeaderName::AccessControlRequestMethod, request.httpMethod());
    preflightRequest.setPriority(request.priority());
    preflightRequest.setFirstPartyForCookies(request.firstPartyForCookies());
    preflightRequest.setIsAppInitiated(request.isAppInitiated());
    if (!referrer.isNull())
        preflightRequest.setHTTPReferrer(referrer);

    const HTTPHeaderMap& requestHeaderFields = request.httpHeaderFields();

    if (!requestHeaderFields.isEmpty()) {
        Vector<String> unsafeHeaders;
        for (auto& headerField : requestHeaderFields) {
            if (!headerField.keyAsHTTPHeaderName || !isCrossOriginSafeRequestHeader(*headerField.keyAsHTTPHeaderName, headerField.value))
                unsafeHeaders.append(headerField.key.convertToASCIILowercase());
        }

        std::sort(unsafeHeaders.begin(), unsafeHeaders.end(), WTF::codePointCompareLessThan);

        StringBuilder headerBuffer;

        bool appendComma = false;
        for (const auto& headerField : unsafeHeaders) {
            if (appendComma)
                headerBuffer.append(',');
            else
                appendComma = true;

            headerBuffer.append(headerField);
        }
        if (!headerBuffer.isEmpty())
            preflightRequest.setHTTPHeaderField(HTTPHeaderName::AccessControlRequestHeaders, headerBuffer.toString());
    }

    if (includeFetchMetadata) {
        Ref requestOrigin = SecurityOrigin::create(request.url());
        if (requestOrigin->isPotentiallyTrustworthy()) {
            preflightRequest.setHTTPHeaderField(HTTPHeaderName::SecFetchMode, "cors"_s);
            preflightRequest.setHTTPHeaderField(HTTPHeaderName::SecFetchDest, "empty"_s);

            if (securityOrigin.isSameOriginAs(requestOrigin))
                preflightRequest.addHTTPHeaderField(HTTPHeaderName::SecFetchSite, "same-origin"_s);
            else if (securityOrigin.isSameSiteAs(requestOrigin))
                preflightRequest.addHTTPHeaderField(HTTPHeaderName::SecFetchSite, "same-site"_s);
            else
                preflightRequest.addHTTPHeaderField(HTTPHeaderName::SecFetchSite, "cross-site"_s);
        }
    }

    return preflightRequest;
}

// https://html.spec.whatwg.org/multipage/urls-and-fetching.html#create-a-potential-cors-request
CachedResourceRequest createPotentialAccessControlRequest(ResourceRequest&& request, ResourceLoaderOptions&& options, Document& document, const String& crossOriginAttribute, SameOriginFlag sameOriginFlag)
{
    ASSERT(options.mode == FetchOptions::Mode::NoCors);
    if (!crossOriginAttribute.isNull())
        options.mode = FetchOptions::Mode::Cors;
    else if (sameOriginFlag == SameOriginFlag::Yes)
        options.mode = FetchOptions::Mode::SameOrigin;

    if (options.mode != FetchOptions::Mode::NoCors) {
        if (auto* page = document.page()) {
            if (page->shouldDisableCorsForRequestTo(request.url()))
                options.mode = FetchOptions::Mode::NoCors;
        }
    }

    if (RefPtr documentLoader = document.loader())
        request.setIsAppInitiated(documentLoader->lastNavigationWasAppInitiated());

    if (crossOriginAttribute.isNull()) {
        CachedResourceRequest cachedRequest { WTFMove(request), WTFMove(options) };
        cachedRequest.setOrigin(document.securityOrigin());
        return cachedRequest;
    }

    FetchOptions::Credentials credentials = equalLettersIgnoringASCIICase(crossOriginAttribute, "omit"_s)
        ? FetchOptions::Credentials::Omit : equalLettersIgnoringASCIICase(crossOriginAttribute, "use-credentials"_s)
        ? FetchOptions::Credentials::Include : FetchOptions::Credentials::SameOrigin;
    options.credentials = credentials;
    switch (credentials) {
    case FetchOptions::Credentials::Include:
        options.storedCredentialsPolicy = StoredCredentialsPolicy::Use;
        break;
    case FetchOptions::Credentials::SameOrigin:
        options.storedCredentialsPolicy = document.securityOrigin().canRequest(request.url(), OriginAccessPatternsForWebProcess::singleton()) ? StoredCredentialsPolicy::Use : StoredCredentialsPolicy::DoNotUse;
        break;
    case FetchOptions::Credentials::Omit:
        options.storedCredentialsPolicy = StoredCredentialsPolicy::DoNotUse;
    }

    CachedResourceRequest cachedRequest { WTFMove(request), WTFMove(options) };
    updateRequestForAccessControl(cachedRequest.resourceRequest(), document.securityOrigin(), options.storedCredentialsPolicy);
    return cachedRequest;
}

String validateCrossOriginRedirectionURL(const URL& redirectURL)
{
    if (!LegacySchemeRegistry::shouldTreatURLSchemeAsCORSEnabled(redirectURL.protocol()))
        return "not allowed to follow a cross-origin CORS redirection with non CORS scheme"_s;

    if (redirectURL.hasCredentials())
        return makeString("redirection URL "_s, redirectURL.string(), " has credentials"_s);

    return { };
}

OptionSet<HTTPHeadersToKeepFromCleaning> httpHeadersToKeepFromCleaning(const HTTPHeaderMap& headers)
{
    OptionSet<HTTPHeadersToKeepFromCleaning> headersToKeep;
    if (headers.contains(HTTPHeaderName::AcceptEncoding))
        headersToKeep.add(HTTPHeadersToKeepFromCleaning::AcceptEncoding);
    if (headers.contains(HTTPHeaderName::CacheControl))
        headersToKeep.add(HTTPHeadersToKeepFromCleaning::CacheControl);
    if (headers.contains(HTTPHeaderName::ContentType))
        headersToKeep.add(HTTPHeadersToKeepFromCleaning::ContentType);
    if (headers.contains(HTTPHeaderName::Origin))
        headersToKeep.add(HTTPHeadersToKeepFromCleaning::Origin);
    if (headers.contains(HTTPHeaderName::Pragma))
        headersToKeep.add(HTTPHeadersToKeepFromCleaning::Pragma);
    if (headers.contains(HTTPHeaderName::Referer))
        headersToKeep.add(HTTPHeadersToKeepFromCleaning::Referer);
    if (headers.contains(HTTPHeaderName::UserAgent))
        headersToKeep.add(HTTPHeadersToKeepFromCleaning::UserAgent);
    return headersToKeep;
}

void cleanHTTPRequestHeadersForAccessControl(ResourceRequest& request, OptionSet<HTTPHeadersToKeepFromCleaning> headersToKeep)
{
    // Remove headers that may have been added by the network layer that cause access control to fail.
    if (!headersToKeep.contains(HTTPHeadersToKeepFromCleaning::ContentType)) {
        auto contentType = request.httpContentType();
        if (!contentType.isNull() && !isCrossOriginSafeRequestHeader(HTTPHeaderName::ContentType, contentType))
            request.clearHTTPContentType();
    }

    if (!headersToKeep.contains(HTTPHeadersToKeepFromCleaning::AcceptEncoding))
        request.clearHTTPAcceptEncoding();
    if (!headersToKeep.contains(HTTPHeadersToKeepFromCleaning::CacheControl))
        request.removeHTTPHeaderField(HTTPHeaderName::CacheControl);
    if (!headersToKeep.contains(HTTPHeadersToKeepFromCleaning::Origin))
        request.clearHTTPOrigin();
    if (!headersToKeep.contains(HTTPHeadersToKeepFromCleaning::Pragma))
        request.removeHTTPHeaderField(HTTPHeaderName::Pragma);
    if (!headersToKeep.contains(HTTPHeadersToKeepFromCleaning::Referer))
        request.clearHTTPReferrer();
    if (!headersToKeep.contains(HTTPHeadersToKeepFromCleaning::UserAgent))
        request.clearHTTPUserAgent();

    request.removeHTTPHeaderField(HTTPHeaderName::SecFetchDest);
    request.removeHTTPHeaderField(HTTPHeaderName::SecFetchMode);
    request.removeHTTPHeaderField(HTTPHeaderName::SecFetchSite);
}

CrossOriginAccessControlCheckDisabler& CrossOriginAccessControlCheckDisabler::singleton()
{
    ASSERT(!isInNetworkProcess());
    static NeverDestroyed<CrossOriginAccessControlCheckDisabler> disabler;
    return disabler.get();
}

void CrossOriginAccessControlCheckDisabler::setCrossOriginAccessControlCheckEnabled(bool enabled)
{
    ASSERT(!isInNetworkProcess());
    m_accessControlCheckEnabled = enabled;
}

bool CrossOriginAccessControlCheckDisabler::crossOriginAccessControlCheckEnabled() const
{
    ASSERT(!isInNetworkProcess());
    return m_accessControlCheckEnabled;
}

Expected<void, String> passesAccessControlCheck(const ResourceResponse& response, StoredCredentialsPolicy storedCredentialsPolicy, const SecurityOrigin& securityOrigin, const CrossOriginAccessControlCheckDisabler* checkDisabler)
{
    // A wildcard Access-Control-Allow-Origin can not be used if credentials are to be sent,
    // even with Access-Control-Allow-Credentials set to true.
    const String& accessControlOriginString = response.httpHeaderField(HTTPHeaderName::AccessControlAllowOrigin);
    bool starAllowed = storedCredentialsPolicy == StoredCredentialsPolicy::DoNotUse;
    if (!starAllowed)
        starAllowed = checkDisabler && !checkDisabler->crossOriginAccessControlCheckEnabled();
    if (accessControlOriginString == "*"_s && starAllowed)
        return { };

    String securityOriginString = securityOrigin.toString();
    if (accessControlOriginString != securityOriginString) {
        if (accessControlOriginString == "*"_s)
            return makeUnexpected("Cannot use wildcard in Access-Control-Allow-Origin when credentials flag is true."_s);
        if (accessControlOriginString.find(',') != notFound)
            return makeUnexpected("Access-Control-Allow-Origin cannot contain more than one origin."_s);
        return makeUnexpected(makeString("Origin "_s, securityOriginString, " is not allowed by Access-Control-Allow-Origin."_s, " Status code: "_s, response.httpStatusCode()));
    }

    if (storedCredentialsPolicy == StoredCredentialsPolicy::Use) {
        const String& accessControlCredentialsString = response.httpHeaderField(HTTPHeaderName::AccessControlAllowCredentials);
        if (accessControlCredentialsString != "true"_s)
            return makeUnexpected("Credentials flag is true, but Access-Control-Allow-Credentials is not \"true\"."_s);
    }

    return { };
}

Expected<void, String> validatePreflightResponse(PAL::SessionID sessionID, const ResourceRequest& request, const ResourceResponse& response, StoredCredentialsPolicy storedCredentialsPolicy, const SecurityOrigin& securityOrigin, const CrossOriginAccessControlCheckDisabler* checkDisabler)
{
    if (!response.isSuccessful())
        return makeUnexpected(makeString("Preflight response is not successful. Status code: "_s, response.httpStatusCode()));

    auto accessControlCheckResult = passesAccessControlCheck(response, storedCredentialsPolicy, securityOrigin, checkDisabler);
    if (!accessControlCheckResult)
        return accessControlCheckResult;

    auto result = CrossOriginPreflightResultCacheItem::create(storedCredentialsPolicy, response);
    if (!result.has_value())
        return makeUnexpected(WTFMove(result.error()));

    auto entry = WTFMove(result.value());
    auto errorDescription = entry->validateMethodAndHeaders(request.httpMethod(), request.httpHeaderFields());
    CrossOriginPreflightResultCache::singleton().appendEntry(sessionID, securityOrigin.toString(), request.url(), entry.moveToUniquePtr());

    if (errorDescription)
        return makeUnexpected(WTFMove(*errorDescription));

    return { };
}

// https://fetch.spec.whatwg.org/#cross-origin-resource-policy-internal-check
static inline bool shouldCrossOriginResourcePolicyCancelLoad(CrossOriginEmbedderPolicyValue coep, const SecurityOrigin& origin, bool isResponseNull, const URL& responseURL, const String& crossOriginResourcePolicyHeaderValue, ForNavigation forNavigation, const OriginAccessPatterns& patterns)
{
    if (forNavigation == ForNavigation::Yes && coep != CrossOriginEmbedderPolicyValue::RequireCORP)
        return false;

    if (isResponseNull || origin.canRequest(responseURL, patterns))
        return false;

    auto policy = parseCrossOriginResourcePolicyHeader(crossOriginResourcePolicyHeaderValue);

    // https://fetch.spec.whatwg.org/#cross-origin-resource-policy-internal-check (step 4).
    if ((policy == CrossOriginResourcePolicy::None || policy == CrossOriginResourcePolicy::Invalid) && coep == CrossOriginEmbedderPolicyValue::RequireCORP)
        return true;

    if (policy == CrossOriginResourcePolicy::SameOrigin)
        return true;

    if (policy == CrossOriginResourcePolicy::SameSite) {
        if (origin.isOpaque())
            return true;
        if (!RegistrableDomain::uncheckedCreateFromHost(origin.host()).matches(responseURL))
            return true;
        if (origin.protocol() == "http"_s && responseURL.protocol() == "https"_s)
            return true;
    }

    return false;
}

std::optional<ResourceError> validateCrossOriginResourcePolicy(CrossOriginEmbedderPolicyValue coep, const SecurityOrigin& origin, const URL& requestURL, bool isResponseNull, const URL& responseURL, const String& crossOriginResourcePolicyHeaderValue, ForNavigation forNavigation, const OriginAccessPatterns& patterns)
{
    if (shouldCrossOriginResourcePolicyCancelLoad(coep, origin, isResponseNull, responseURL, crossOriginResourcePolicyHeaderValue, forNavigation, patterns))
        return ResourceError { errorDomainWebKitInternal, 0, requestURL, makeString("Cancelled load to "_s, responseURL.stringCenterEllipsizedToLength(), " because it violates the resource's Cross-Origin-Resource-Policy response header."_s), ResourceError::Type::AccessControl };
    return std::nullopt;
}

std::optional<ResourceError> validateCrossOriginResourcePolicy(CrossOriginEmbedderPolicyValue coep, const SecurityOrigin& origin, const URL& requestURL, const ResourceResponse& response, ForNavigation forNavigation, const OriginAccessPatterns& patterns)
{
    bool isReponseNull = response.isNull();
    String crossOriginResourcePolicyHeaderValue = isReponseNull ? nullString() : response.httpHeaderField(HTTPHeaderName::CrossOriginResourcePolicy);
    URL responseURL = isReponseNull ? URL { } : response.url();
    return validateCrossOriginResourcePolicy(coep, origin, requestURL, isReponseNull, responseURL, crossOriginResourcePolicyHeaderValue, forNavigation, patterns);
}

std::optional<ResourceError> validateRangeRequestedFlag(const ResourceRequest& request, const ResourceResponse& response)
{
    if (response.isRangeRequested() && response.httpStatusCode() == 206 && response.type() == ResourceResponse::Type::Opaque && !request.hasHTTPHeaderField(HTTPHeaderName::Range))
        return ResourceError({ }, 0, response.url(), { }, ResourceError::Type::General);
    return std::nullopt;
}

} // namespace WebCore
