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Backported simple support for BIMI indicators
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| /** | ||
| * Brand Indicators for Message Identification (BIMI). | ||
| * https://datatracker.ietf.org/doc/draft-brand-indicators-for-message-identification/04/ | ||
| * | ||
| * BIMI implementation for a Mail User Agent (MUA). | ||
| * Gets the BIMI Indicator based on the information the receiving | ||
| * Mail Transfer Agent (MTA) writes into the headers of the message. | ||
| * | ||
| * This is not a complete implementation of BIMI. | ||
| * | ||
| * Copyright (c) 2023 Philippe Lieser | ||
| * | ||
| * This software is licensed under the terms of the MIT License. | ||
| * | ||
| * The above copyright and license notice shall be | ||
| * included in all copies or substantial portions of the Software. | ||
| */ | ||
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| // options for ESLint | ||
| /* global Components */ | ||
| /* global Logging */ | ||
| /* exported EXPORTED_SYMBOLS, BIMI */ | ||
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| "use strict"; | ||
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| var EXPORTED_SYMBOLS = [ | ||
| "BIMI" | ||
| ]; | ||
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| // @ts-ignore | ||
| const Cu = Components.utils; | ||
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| Cu.import("resource://dkim_verifier/logging.jsm.js"); | ||
| Cu.import("resource://dkim_verifier/ARHParser.jsm.js"); | ||
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| let BIMI = (function() { | ||
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| const log = Logging.getLogger("BIMI"); | ||
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| // WSP as specified in Appendix B.1 of RFC 5234 | ||
| const WSP_p = "[ \t]"; | ||
| // obs-FWS as specified in Section 4.2 of RFC 5322 | ||
| const obs_FWS_p = `(?:${WSP_p}+(?:\r\n${WSP_p}+)*)`; | ||
| // FWS as specified in Section 3.2.2 of RFC 5322 | ||
| const FWS_p = `(?:(?:(?:${WSP_p}*\r\n)?${WSP_p}+)|${obs_FWS_p})`; | ||
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| let that = { | ||
| /** | ||
| * Try to get the BIMI Indicator if available. | ||
| * | ||
| * @param {Map<string, string[]>} headers | ||
| * @param {ARHResinfo[]} arhBIMI - Trusted ARHs containing a BIMI result. | ||
| * @returns {string|null} | ||
| */ | ||
| getBimiIndicator: function(headers, arhBIMI) { | ||
| // Assuming: | ||
| // 1. We only get ARHs that can be trusted (i.e. from the receiving MTA). | ||
| // 2. If the receiving MTA does not supports BIMI, | ||
| // we will not see an ARH with a BIMI result (because of 1) | ||
| // 3. If the receiving MTA supports BIMI, | ||
| // it will make sure we only see his BIMI-Indicator headers (as required by the RFC). | ||
| // | ||
| // Given the above, it should be safe to trust the BIMI indicator from the BIMI-Indicator header | ||
| // if we have a passing BIMI result there the MTA claims to have checked the Authority Evidence. | ||
| const hasAuthorityPassBIMI = arhBIMI.some( | ||
| arh => arh.method === "bimi" && | ||
| arh.result === "pass" && | ||
| arh.propertys.policy.authority === "pass" | ||
| ); | ||
| if (!hasAuthorityPassBIMI) { | ||
| return null; | ||
| } | ||
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| const bimiIndicators = headers.get("bimi-indicator") || []; | ||
| if (bimiIndicators.length > 1) { | ||
| log.warn("Message contains more than one BIMI-Indicator header"); | ||
| return null; | ||
| } | ||
| let bimiIndicator = bimiIndicators[0]; | ||
| if (!bimiIndicator) { | ||
| log.warn("Message contains an ARH with passing BIMI but does not have a BIMI-Indicator header"); | ||
| return null; | ||
| } | ||
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| // TODO: If in the future we support ARC we might want to check the policy.indicator-hash | ||
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| // Remove header name and new line at end | ||
| bimiIndicator = bimiIndicator.slice("bimi-indicator:".length, -"\r\n".length); | ||
| // Remove all whitespace | ||
| bimiIndicator = bimiIndicator.replace(new RegExp(`${FWS_p}`, "g"), ""); | ||
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| return bimiIndicator; | ||
| } | ||
| }; | ||
| return that; | ||
| }()); |