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68 lines
2.7 KiB
TypeScript
68 lines
2.7 KiB
TypeScript
import { debug } from '@/lib/debug';
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/**
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* Extra headers plugins add to an outgoing message (OutgoingEmail.headers),
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* such as a classification label, as JMAP Email/set create properties
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* (RFC 8621 §4.1.3, `header:Name:asText`, which the server encodes and folds).
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*
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* Only headers of their own get through. Names the client writes from other
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* properties are dropped, because JMAP refuses a create that sets the same
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* header twice, and so are names that say who sent the mail or how it
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* travelled: a plugin must not change the sender or forge trace and
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* authentication headers.
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*/
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const RESERVED = new Set([
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'from', 'sender', 'reply-to', 'to', 'cc', 'bcc', 'subject', 'date',
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'message-id', 'in-reply-to', 'references', 'mime-version',
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'return-path', 'received', 'received-spf', 'authentication-results',
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'dkim-signature', 'domainkey-signature',
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'disposition-notification-to', 'importance', 'x-priority', 'priority',
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]);
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const RESERVED_PREFIXES = ['content-', 'resent-', 'arc-'];
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/** RFC 5322 §3.6.8 field-name: printable US-ASCII except the colon. */
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const FIELD_NAME = /^[\x21-\x39\x3b-\x7e]{1,76}$/;
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/** Line breaks or other control characters but tab (header injection). */
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function hasControlCharacter(value: string): boolean {
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for (let i = 0; i < value.length; i++) {
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const code = value.charCodeAt(i);
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if ((code < 0x20 && code !== 0x09) || code === 0x7f) return true;
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}
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return false;
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}
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const MAX_HEADERS = 20;
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// Room for an Autocrypt header with a whole key in it; the server folds it.
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const MAX_VALUE_LENGTH = 8192;
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function isReserved(lowerName: string): boolean {
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return RESERVED.has(lowerName) || RESERVED_PREFIXES.some((prefix) => lowerName.startsWith(prefix));
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}
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export function customHeaderProperties(headers: unknown): Record<string, string> {
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const out: Record<string, string> = {};
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if (!headers || typeof headers !== 'object' || Array.isArray(headers)) return out;
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const seen = new Set<string>();
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for (const [name, raw] of Object.entries(headers as Record<string, unknown>)) {
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const lower = name.toLowerCase();
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if (!FIELD_NAME.test(name) || isReserved(lower) || seen.has(lower)) {
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debug.warn(`Outgoing header "${name}" from a plugin was not sent`);
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continue;
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}
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if (typeof raw !== 'string') continue;
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const value = raw.trim();
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if (!value) continue;
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if (hasControlCharacter(value) || value.length > MAX_VALUE_LENGTH) {
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debug.warn(`Outgoing header "${name}" from a plugin was not sent: invalid value`);
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continue;
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}
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if (seen.size >= MAX_HEADERS) {
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debug.warn(`Outgoing header "${name}" from a plugin was not sent: more than ${MAX_HEADERS} headers`);
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continue;
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}
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seen.add(lower);
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out[`header:${name}:asText`] = value;
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}
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return out;
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}
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