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code review: simplify CSP injection code

pull/2/head
gorhill 8 years ago
parent
commit
4765db4d86
  1. 94
      src/js/traffic.js

94
src/js/traffic.js

@ -19,7 +19,6 @@
Home: https://github.com/gorhill/uMatrix
*/
/* global chrome, µMatrix */
/* jshint boss: true */
'use strict';
@ -296,8 +295,6 @@ var foilRefererHeaders = function(µm, toHostname, details) {
// https://github.com/gorhill/httpswitchboard/issues/35
var onHeadersReceived = function(details) {
// console.debug('onHeadersReceived()> "%s": %o', details.url, details);
// Ignore schemes other than 'http...'
var requestURL = details.url;
if ( requestURL.lastIndexOf('http', 0) !== 0 ) {
@ -328,96 +325,23 @@ var onHeadersReceived = function(details) {
// We block only inline-script tags, all the external javascript will be
// blocked by our request handler.
// https://github.com/gorhill/uMatrix/issues/129
// https://github.com/gorhill/uMatrix/issues/320
// Modernize CSP injection:
// - Do not overwrite blindly possibly already present CSP header
// - Add CSP directive to block inline script ONLY if needed
// - If we end up modifying the an existing CSP, strip out `report-uri`
// to prevent spurious CSP violations.
var headers = details.responseHeaders;
// Is there a CSP header present?
// If not, inject a script-src CSP directive to prevent inline javascript
// from executing.
var i = headerIndexFromName('content-security-policy', headers);
if ( i === -1 ) {
headers.push({
'name': 'Content-Security-Policy',
'value': "script-src 'unsafe-eval' *"
});
return { responseHeaders: headers };
var csp = "script-src 'unsafe-eval' *",
headers = details.responseHeaders,
i = headerIndexFromName('content-security-policy', headers);
// A CSP header is already present: just add our own directive as a
// separate disposition (i.e. use comma).
if ( i !== -1 ) {
csp = headers[i].value.trim() + ', ' + csp;
headers.splice(i, 1);
}
// A CSP header is already present.
// Remove the CSP header, we will re-inject it after processing it.
// TODO: We are currently forced to add the CSP header at the end of the
// headers array, because this is what the platform specific code
// expect (Firefox).
var csp = headers.splice(i, 1)[0].value.trim();
// Is there a script-src directive in the CSP header?
// If not, we simply need to append our script-src directive.
// https://github.com/gorhill/uMatrix/issues/320
// Since we are modifying an existing CSP header, we need to strip out
// 'report-uri' if it is present, to prevent spurious reporting of CSP
// violation, and thus the leakage of information to the remote site.
var matches = reScriptsrc.exec(csp);
if ( matches === null ) {
headers.push({
'name': 'Content-Security-Policy',
'value': cspStripReporturi(csp + "; script-src 'unsafe-eval' *")
});
return { responseHeaders: headers };
}
// A `script-src' directive is already present. Extract it.
var scriptsrc = matches[0];
// Is there at least one 'unsafe-inline' or 'nonce-' token in the
// script-src?
// If not we have no further processing to perform: inline scripts are
// already forbidden by the site.
if ( reUnsafeinline.test(scriptsrc) === false ) {
headers.push({
'name': 'Content-Security-Policy',
'value': csp
});
return { responseHeaders: headers };
}
// There are tokens enabling inline script tags in the script-src
// directive, so we have to strip them out.
// Strip out whole script-src directive, remove the offending tokens
// from it, then append the resulting script-src directive to the original
// CSP header.
// https://github.com/gorhill/uMatrix/issues/320
// Since we are modifying an existing CSP header, we need to strip out
// 'report-uri' if it is present, to prevent spurious reporting of CSP
// violation, and thus the leakage of information to the remote site.
// https://github.com/gorhill/uMatrix/issues/538
// We will replace in-place the script-src directive with our own.
headers.push({
'name': 'Content-Security-Policy',
'value': cspStripReporturi(
csp.slice(0, matches.index) +
scriptsrc.replace(reUnsafeinline, '') +
csp.slice(matches.index + scriptsrc.length)
)
});
headers.push({ name: 'Content-Security-Policy', value: csp });
return { responseHeaders: headers };
};
var cspStripReporturi = function(csp) {
return csp.replace(reReporturi, '');
};
var reReporturi = /report-uri[^;]*;?\s*/;
var reScriptsrc = /script-src[^;]*;?\s*/;
var reUnsafeinline = /'unsafe-inline'\s*|'nonce-[^']+'\s*/g;
/******************************************************************************/
var headerValue = function(headers, name) {

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