259 lines
8.6 KiB
JavaScript
259 lines
8.6 KiB
JavaScript
'use strict';
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/**
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* 零依赖 SMTP 提交客户端（587 + STARTTLS + AUTH PLAIN）。
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*
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* 与服务器端实现相同的关键纪律：
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* **DATA 段必须按字节写出，且除 dot-stuffing 外不得改动任何字节。**
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* 中文乱码的历史根因就是这里用了 ASCII 编码写 DATA —— 本实现只做：
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* ① 行尾统一成 CRLF；② 行首的点做 dot-stuffing；③ 结尾补 CRLF + "." + CRLF。
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* 绝不碰正文的其它字节，也绝不重新编码。
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*/
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const tls = require('node:tls');
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const net = require('node:net');
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const { EventEmitter } = require('node:events');
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class SmtpError extends Error {
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constructor(message, info = {}) {
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super(message);
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this.name = 'SmtpError';
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this.code = info.code || null;
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this.stage = info.stage || null;
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this.detail = info.detail || '';
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}
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}
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/** 行尾统一为 CRLF（不动其它字节，UTF-8 原样保留） */
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function normalizeCrlf(buffer) {
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const out = Buffer.alloc(buffer.length + 16);
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let n = 0;
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let i = 0;
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while (i < buffer.length) {
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const c = buffer[i];
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if (c === 0x0d) {
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out[n++] = 0x0d; out[n++] = 0x0a;
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i += (i + 1 < buffer.length && buffer[i + 1] === 0x0a) ? 2 : 1;
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continue;
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}
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if (c === 0x0a) { out[n++] = 0x0d; out[n++] = 0x0a; i++; continue; }
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out[n++] = c; i++;
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}
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let bytes = out.subarray(0, n);
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if (!(bytes.length >= 2 && bytes[bytes.length - 2] === 0x0d && bytes[bytes.length - 1] === 0x0a)) {
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bytes = Buffer.concat([bytes, Buffer.from('\r\n')]);
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}
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return bytes;
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}
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/** dot-stuffing：仅当行首是 "." 时补一个点 */
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function dotStuff(normalized) {
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const parts = [Buffer.from('')];
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let start = 0;
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for (let i = 0; i < normalized.length; i++) {
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const atLineStart = i === 0 || normalized[i - 1] === 0x0a;
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if (atLineStart && normalized[i] === 0x2e) {
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parts.push(normalized.subarray(start, i));
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parts.push(Buffer.from('.'));
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start = i;
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}
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}
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parts.push(normalized.subarray(start));
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return Buffer.concat(parts);
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}
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/** 生成 DATA 段要写出的完整字节 */
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function encodeData(raw) {
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const normalized = normalizeCrlf(raw);
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const stuffed = dotStuff(normalized);
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return Buffer.concat([stuffed, Buffer.from('.\r\n')]);
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}
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class SmtpClient extends EventEmitter {
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/**
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* @param {object} opts
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* @param {string} opts.host
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* @param {number} [opts.port=587]
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* @param {string} opts.user
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* @param {string} opts.password
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* @param {boolean} [opts.startTls=true]
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* @param {string} [opts.heloName] 默认取本机主机名
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* @param {number} [opts.timeoutMs=30000]
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* @param {boolean} [opts.debug=false]
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*/
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constructor(opts) {
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super();
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this.opts = Object.assign({ port: 587, startTls: true, timeoutMs: 30000, debug: false }, opts);
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this.socket = null;
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this.buffer = '';
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this.waiters = [];
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this.capabilities = [];
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this.on('error', () => {});
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}
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_log(dir, text) {
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if (!this.opts.debug) return;
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process.stderr.write(`[smtp ${dir}] ${String(text).replace(/\r?\n/g, '\\n').slice(0, 300)}\n`);
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}
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async connect() {
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const { host, port, timeoutMs } = this.opts;
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this.socket = await new Promise((resolve, reject) => {
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const sock = net.connect({ host, port }, () => resolve(sock));
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sock.setTimeout(timeoutMs, () => reject(new SmtpError(`连接 ${host}:${port} 超时`)));
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sock.once('error', (err) => reject(new SmtpError(`连接 ${host}:${port} 失败：${err.message}`)));
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});
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this.socket.setTimeout(0);
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this._attach(this.socket);
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const greeting = await this.readResponse();
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if (greeting.code !== 220) throw new SmtpError(`问候语异常：${greeting.text}`, { code: greeting.code });
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return greeting;
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}
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_attach(sock) {
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sock.setNoDelay(true);
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sock.on('data', (chunk) => this._onData(chunk));
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sock.on('error', (err) => this._failAll(err));
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sock.on('close', () => { this.closed = true; this._failAll(new SmtpError('连接已关闭', { stage: 'close' })); });
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}
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_onData(chunk) {
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this.buffer += chunk.toString('latin1');
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this._drain();
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}
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_drain() {
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for (;;) {
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// 找到「最后一行」：形如 "250 xxx\r\n"
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const idx = this.buffer.indexOf('\r\n');
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if (idx < 0) return;
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const line = this.buffer.slice(0, idx);
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this.buffer = this.buffer.slice(idx + 2);
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if (!this.curLines) this.curLines = [];
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this.curLines.push(line);
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this._log('<', line);
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if (/^\d{3} /.test(line) || !/^\d{3}-/.test(line)) {
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const lines = this.curLines;
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this.curLines = null;
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const code = Number(lines[0].slice(0, 3));
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const w = this.waiters.shift();
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const resp = { code, lines, text: lines.map((l) => l.slice(4)).join('\n') };
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if (w) w.resolve(resp);
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else this.emit('unsolicited', resp);
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}
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}
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}
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_failAll(err) {
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const ws = this.waiters;
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this.waiters = [];
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for (const w of ws) { clearTimeout(w.timer); w.reject(err); }
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}
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readResponse(timeoutMs = this.opts.timeoutMs) {
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return new Promise((resolve, reject) => {
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const timer = setTimeout(() => {
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const i = this.waiters.findIndex((w) => w.resolve === resolve);
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if (i >= 0) this.waiters.splice(i, 1);
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reject(new SmtpError('等待服务器应答超时', { stage: 'read' }));
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}, timeoutMs);
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this.waiters.push({ resolve, reject, timer });
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});
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}
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async command(text, expectCodes, stage) {
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this._log('>', text);
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this.socket.write(text + '\r\n');
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const resp = await this.readResponse();
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if (expectCodes && !expectCodes.includes(resp.code)) {
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throw new SmtpError(`${stage || text.split(' ')[0]} 失败：${resp.code} ${resp.text}`,
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{ code: resp.code, stage: stage || text.split(' ')[0], detail: resp.text });
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}
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return resp;
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}
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_parseEhlo(resp) {
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const caps = [];
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for (const line of resp.lines.slice(1)) {
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const t = line.slice(4).trim();
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if (t) caps.push(t);
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}
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this.capabilities = caps;
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return caps;
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}
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/** EHLO → STARTTLS → EHLO → AUTH PLAIN */
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async hello() {
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const hostname = this.opts.heloName || require('node:os').hostname();
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let resp = await this.command(`EHLO ${hostname}`, [250], 'EHLO');
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this._parseEhlo(resp);
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if (this.opts.startTls) {
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const hasStartTls = this.capabilities.some((c) => /^STARTTLS/i.test(c));
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if (!hasStartTls) throw new SmtpError('服务器未广告 STARTTLS', { stage: 'STARTTLS' });
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await this.command('STARTTLS', [220], 'STARTTLS');
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await this._upgrade();
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resp = await this.command(`EHLO ${hostname}`, [250], 'EHLO');
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this._parseEhlo(resp);
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}
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return this.capabilities;
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}
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_upgrade() {
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const { host } = this.opts;
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return new Promise((resolve, reject) => {
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const secured = tls.connect({ socket: this.socket, servername: host }, () => {
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this.socket = secured;
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this.buffer = '';
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this.curLines = null;
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secured.removeAllListeners('data');
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secured.removeAllListeners('error');
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secured.removeAllListeners('close');
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this._attach(secured);
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resolve();
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});
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secured.once('error', reject);
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});
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}
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async auth() {
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const { user, password } = this.opts;
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if (!user) return false;
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const token = Buffer.from(`\u0000${user}\u0000${password}`, 'utf8').toString('base64');
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const resp = await this.command(`AUTH PLAIN ${token}`, [235], 'AUTH');
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return resp.code === 235;
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}
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/**
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* 发一封信。
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* @param {string} from 信封发件人（通常与 From 头一致）
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* @param {string[]} to 收件人（含抄送/密送，密送不进头部）
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* @param {Buffer} rawMessage 完整 MIME 报文（UTF-8 字节）
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*/
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async sendMail(from, to, rawMessage) {
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await this.command(`MAIL FROM:<${from}>`, [250, 251], 'MAIL FROM');
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for (const rcpt of to) {
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await this.command(`RCPT TO:<${rcpt}>`, [250, 251], `RCPT TO ${rcpt}`);
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}
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await this.command('DATA', [354], 'DATA');
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const payload = encodeData(rawMessage);
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this._log('>', `<DATA ${payload.length} 字节>`);
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this.socket.write(payload);
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const resp = await this.readResponse(120000);
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this._log('<', `${resp.code} ${resp.text}`);
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if (resp.code !== 250) {
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throw new SmtpError(`邮件正文被拒：${resp.code} ${resp.text}`, { code: resp.code, stage: 'DATA', detail: resp.text });
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}
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return resp;
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}
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async quit() {
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try {
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if (this.socket && !this.socket.destroyed) await this.command('QUIT', [221], 'QUIT');
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} catch { /* 忽略 */ }
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try { this.socket?.destroy(); } catch { /* 忽略 */ }
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}
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}
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module.exports = { SmtpClient, SmtpError, encodeData, normalizeCrlf, dotStuff };
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