Strip request origin (#710)

* Add web request permissions

* Create fetch wrapper that anonymizes the request

* Fix Firefox not supporting 'extraHeaders' option

1 files changed, 133 insertions, 0 deletions

diff --git a/ext/bg/js/request-builder.js b/ext/bg/js/request-builder.js
new file mode 100644
index 00000000..011d6bb8
--- /dev/null
+++ b/ext/bg/js/request-builder.js
@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2020  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+class RequestBuilder {
+    constructor() {
+        this._extraHeadersSupported = null;
+        this._onBeforeSendHeadersExtraInfoSpec = ['blocking', 'requestHeaders', 'extraHeaders'];
+    }
+
+    async fetchAnonymous(url, init) {
+        const originURL = this._getOriginURL(url);
+        const modifications = [
+            ['cookie', null],
+            ['origin', {name: 'Origin', value: originURL}]
+        ];
+        return this.fetchModifyHeaders(url, init, modifications);
+    }
+
+    async fetchModifyHeaders(url, init, modifications) {
+        const matchURL = this._getMatchURL(url);
+
+        let done = false;
+        const callback = (details) => {
+            if (done || details.url !== url) { return {}; }
+            done = true;
+
+            const requestHeaders = details.requestHeaders;
+            this._modifyHeaders(requestHeaders, modifications);
+            return {requestHeaders};
+        };
+        const filter = {
+            urls: [matchURL],
+            types: ['xmlhttprequest']
+        };
+
+        let needsCleanup = false;
+        try {
+            this._onBeforeSendHeadersAddListener(callback, filter);
+            needsCleanup = true;
+        } catch (e) {
+            // NOP
+        }
+
+        try {
+            return await fetch(url, init);
+        } finally {
+            if (needsCleanup) {
+                try {
+                    chrome.webRequest.onBeforeSendHeaders.removeListener(callback);
+                } catch (e) {
+                    // NOP
+                }
+            }
+        }
+    }
+
+    // Private
+
+    _onBeforeSendHeadersAddListener(callback, filter) {
+        const extraInfoSpec = this._onBeforeSendHeadersExtraInfoSpec;
+        for (let i = 0; i < 2; ++i) {
+            try {
+                chrome.webRequest.onBeforeSendHeaders.addListener(callback, filter, extraInfoSpec);
+                if (this._extraHeadersSupported === null) {
+                    this._extraHeadersSupported = true;
+                }
+                break;
+            } catch (e) {
+                // Firefox doesn't support the 'extraHeaders' option and will throw the following error:
+                // Type error for parameter extraInfoSpec (Error processing 2: Invalid enumeration value "extraHeaders") for webRequest.onBeforeSendHeaders.
+                if (this._extraHeadersSupported !== null || !`${e.message}`.includes('extraHeaders')) {
+                    throw e;
+                }
+            }
+
+            // addListener failed; remove 'extraHeaders' from extraInfoSpec.
+            this._extraHeadersSupported = false;
+            const index = extraInfoSpec.indexOf('extraHeaders');
+            if (index >= 0) { extraInfoSpec.splice(index, 1); }
+        }
+    }
+
+    _getMatchURL(url) {
+        const url2 = new URL(url);
+        return `${url2.protocol}//${url2.host}${url2.pathname}`;
+    }
+
+    _getOriginURL(url) {
+        const url2 = new URL(url);
+        return `${url2.protocol}//${url2.host}`;
+    }
+
+    _modifyHeaders(headers, modifications) {
+        modifications = new Map(modifications);
+
+        for (let i = 0, ii = headers.length; i < ii; ++i) {
+            const header = headers[i];
+            const name = header.name.toLowerCase();
+            const modification = modifications.get(name);
+            if (typeof modification === 'undefined') { continue; }
+
+            modifications.delete(name);
+
+            if (modification === null) {
+                headers.splice(i, 1);
+                --i;
+                --ii;
+            } else {
+                headers[i] = modification;
+            }
+        }
+
+        for (const header of modifications.values()) {
+            if (header !== null) {
+                headers.push(header);
+            }
+        }
+    }
+}