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Restore ability to redirect xhr to image resources
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The ability to redirect xmlhttprequest to binary
resources was lost when redirectable/injectable
resources became immutable in commit
152cea2.

This commit restores the ability to redirect a
xmlhttprequest to a binary resource by making
it possible to derive a data: URI from the
content of binary resources such as images.

Addtionally a redirect to a data: URI can be
forced by prefixing the resource token with `%`.
This is a non-official feature at this point,
i.e. it could be removed at any time.
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@gorhill
gorhill committed Aug 6, 2019
1 parent a1b9995 commit 7ac7b02
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Showing 2 changed files with 168 additions and 163 deletions.
135 changes: 73 additions & 62 deletions src/js/assets.js
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Original file line number Diff line number Diff line change
Expand Up @@ -62,36 +62,8 @@ const fireNotification = function(topic, details) {

/******************************************************************************/

api.fetchText = function(url, onLoad, onError) {
const isExternal = reIsExternalPath.test(url);
let actualUrl = isExternal ? url : vAPI.getURL(url);

// https://github.com/gorhill/uBlock/issues/2592
// Force browser cache to be bypassed, but only for resources which have
// been fetched more than one hour ago.
//
// https://github.com/uBlockOrigin/uBlock-issues/issues/682#issuecomment-515197130
// Provide filter list authors a way to completely bypass
// the browser cache.
if ( isExternal ) {
const cacheBypassToken =
µBlock.hiddenSettings.updateAssetBypassBrowserCache
? Math.floor(Date.now() / 1000) % 86400
: Math.floor(Date.now() / 3600000) % 12;
const queryValue = `_=${cacheBypassToken}`;
if ( actualUrl.indexOf('?') === -1 ) {
actualUrl += '?';
} else {
actualUrl += '&';
}
actualUrl += queryValue;
}

if ( typeof onError !== 'function' ) {
onError = onLoad;
}

return new Promise(resolve => {
api.fetch = function(url, options = {}) {
return new Promise((resolve, reject) => {
// Start of executor

const timeoutAfter = µBlock.hiddenSettings.assetFetchTimeout * 1000 || 30000;
Expand All @@ -110,20 +82,6 @@ api.fetchText = function(url, onLoad, onError) {
}
};

const onResolve = function(details) {
if ( onLoad instanceof Function ) {
return onLoad(details);
}
resolve(details);
};

const onReject = function(details) {
if ( onError instanceof Function ) {
return onError(details);
}
resolve(details);
};

// https://github.com/gorhill/uMatrix/issues/15
const onLoadEvent = function() {
cleanup();
Expand All @@ -135,31 +93,20 @@ api.fetchText = function(url, onLoad, onError) {
statusText: this.statusText || ''
};
if ( details.statusCode < 200 || details.statusCode >= 300 ) {
return onReject(details);
}
// consider an empty result to be an error
if ( stringIsNotEmpty(this.responseText) === false ) {
return onReject(details);
}
// we never download anything else than plain text: discard if response
// appears to be a HTML document: could happen when server serves
// some kind of error page I suppose
const text = this.responseText.trim();
if ( text.startsWith('<') && text.endsWith('>') ) {
return onReject(details);
return reject(details);
}
details.content = this.responseText;
onResolve(details);
details.content = this.response;
resolve(details);
};

const onErrorEvent = function() {
cleanup();
µBlock.logger.writeOne({
realm: 'message',
type: 'error',
text: errorCantConnectTo.replace('{{msg}}', actualUrl)
text: errorCantConnectTo.replace('{{msg}}', url)
});
onReject({ url, content: '' });
reject({ url, content: '' });
};

const onTimeout = function() {
Expand All @@ -181,12 +128,12 @@ api.fetchText = function(url, onLoad, onError) {
// I am pretty sure it used to work, but now using a URL such as
// `file:///` on Chromium 40 results in an exception being thrown.
try {
xhr.open('get', actualUrl, true);
xhr.open('get', url, true);
xhr.addEventListener('load', onLoadEvent);
xhr.addEventListener('error', onErrorEvent);
xhr.addEventListener('abort', onErrorEvent);
xhr.addEventListener('progress', onProgressEvent);
xhr.responseType = 'text';
xhr.responseType = options.responseType || 'text';
xhr.send();
timeoutTimer = vAPI.setTimeout(onTimeout, timeoutAfter);
} catch (e) {
Expand All @@ -199,6 +146,70 @@ api.fetchText = function(url, onLoad, onError) {

/******************************************************************************/

api.fetchText = function(url, onLoad, onError) {
const isExternal = reIsExternalPath.test(url);
let actualUrl = isExternal ? url : vAPI.getURL(url);

// https://github.com/gorhill/uBlock/issues/2592
// Force browser cache to be bypassed, but only for resources which have
// been fetched more than one hour ago.
//
// https://github.com/uBlockOrigin/uBlock-issues/issues/682#issuecomment-515197130
// Provide filter list authors a way to completely bypass
// the browser cache.
if ( isExternal ) {
const cacheBypassToken =
µBlock.hiddenSettings.updateAssetBypassBrowserCache
? Math.floor(Date.now() / 1000) % 86400
: Math.floor(Date.now() / 3600000) % 12;
const queryValue = `_=${cacheBypassToken}`;
if ( actualUrl.indexOf('?') === -1 ) {
actualUrl += '?';
} else {
actualUrl += '&';
}
actualUrl += queryValue;
}

if ( typeof onError !== 'function' ) {
onError = onLoad;
}

const onResolve = function(details) {
if ( onLoad instanceof Function ) {
return onLoad(details);
}
return details;
};

const onReject = function(details) {
details.content = '';
if ( onError instanceof Function ) {
return onError(details);
}
return details;
};

return api.fetch(url).then(details => {
// consider an empty result to be an error
if ( stringIsNotEmpty(details.content) === false ) {
return onReject(details);
}
// we never download anything else than plain text: discard if response
// appears to be a HTML document: could happen when server serves
// some kind of error page I suppose
const text = details.content.trim();
if ( text.startsWith('<') && text.endsWith('>') ) {
return onReject(details);
}
return onResolve(details);
}).catch(details => {
return onReject(details);
});
};

/******************************************************************************/

// https://github.com/gorhill/uBlock/issues/3331
// Support the seamless loading of sublists.

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1 comment on commit 7ac7b02

@gorhill
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@gorhill gorhill commented on 7ac7b02 Aug 6, 2019

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I should have noted that I found only one instance of such xhr redirection to an image, which I removed when I refactored resource management:

uBlockOrigin/uAssets@1e0b6bb

I verified the filter was obsolete but it does show that the case for such filter can arise.

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