send-mail/node_modules/nodemailer/dist/esm/dkim/relaxed-body.js

// streams through a message body and calculates relaxed body hash
import { Transform } from 'node:stream';
import crypto from 'node:crypto';
const CHAR_CR = 0x0d;
const CHAR_LF = 0x0a;
const CHAR_SPACE = 0x20;
const CHAR_TAB = 0x09;
const CRLF = Buffer.from('\r\n');
// a run of empty lines is hashed from this buffer in slices
const EMPTY_LINES = Buffer.alloc(4096, CRLF);
/**
 * Passes the message body through unchanged and hashes its relaxed
 * canonicalization (RFC 6376 section 3.4.4) on the side: whitespace at the end
 * of a line is dropped, runs of whitespace within a line become a single space,
 * every line ends with CRLF, empty lines at the end of the body are ignored and
 * a non-empty body always ends with CRLF. Bytes are canonicalized as they arrive,
 * so a line of any length costs constant memory.
 */
export default class RelaxedBody extends Transform {
    constructor(options) {
        super();
        options = options || {};
        this.bodyHash = crypto.createHash(options.hashAlgo || 'sha256');
        this.byteLength = 0;
        this.debug = options.debug;
        this._debugBody = options.debug ? [] : false;
        this._lineHasContent = false;
        this._pendingWsp = false;
        this._pendingCr = false;
        this._pendingEmptyLines = 0;
    }
    /** @internal */
    _hashCanonical(data) {
        if (!data.length) {
            return;
        }
        this.bodyHash.update(data);
        if (this._debugBody) {
            this._debugBody.push(Buffer.from(data));
        }
    }
    /** @internal */
    _hashEmptyLines() {
        while (this._pendingEmptyLines > 0) {
            const count = Math.min(this._pendingEmptyLines, EMPTY_LINES.length / 2);
            this._hashCanonical(EMPTY_LINES.subarray(0, count * 2));
            this._pendingEmptyLines -= count;
        }
    }
    /**
     * Writes a content byte, with the space a pending run of whitespace collapses to,
     * into the output buffer and returns the new write position. Kept a method rather
     * than a closure so the write position stays a plain local in the byte loop
     * @internal
     */
    _emitContent(out, outPos, c) {
        if (!this._lineHasContent) {
            if (this._pendingEmptyLines) {
                // the first content byte of a line is where the empty lines before it
                // become part of the body, so hash what is in the buffer before them
                this._hashCanonical(out.subarray(0, outPos));
                outPos = 0;
                this._hashEmptyLines();
            }
            this._lineHasContent = true;
        }
        if (this._pendingWsp) {
            out[outPos++] = CHAR_SPACE;
            this._pendingWsp = false;
        }
        out[outPos++] = c;
        return outPos;
    }
    updateHash(chunk, final) {
        // every byte contributes itself at most once, plus a CR for a bare LF
        // and, once per chunk, a pending space and CR carried over from before
        const out = Buffer.allocUnsafe(chunk.length * 2 + 2);
        let outPos = 0;
        for (let i = 0; i < chunk.length; i++) {
            const c = chunk[i];
            if (c === CHAR_LF) {
                // end of line, a CR right before it and any trailing whitespace are dropped
                if (this._lineHasContent) {
                    out[outPos++] = CHAR_CR;
                    out[outPos++] = CHAR_LF;
                    this._lineHasContent = false;
                }
                else {
                    this._pendingEmptyLines++;
                }
                this._pendingWsp = false;
                this._pendingCr = false;
                continue;
            }
            if (this._pendingCr) {
                // not followed by LF, so the CR is content
                outPos = this._emitContent(out, outPos, CHAR_CR);
                this._pendingCr = false;
            }
            if (c === CHAR_CR) {
                this._pendingCr = true;
            }
            else if (c === CHAR_SPACE || c === CHAR_TAB) {
                this._pendingWsp = true;
            }
            else {
                outPos = this._emitContent(out, outPos, c);
            }
        }
        if (final && this._pendingCr) {
            // a CR at the very end of the body is content
            outPos = this._emitContent(out, outPos, CHAR_CR);
            this._pendingCr = false;
        }
        this._hashCanonical(out.subarray(0, outPos));
    }
    /** @internal */
    _transform(chunk, encoding, callback) {
        if (!chunk || !chunk.length) {
            return callback();
        }
        if (typeof chunk === 'string') {
            chunk = Buffer.from(chunk, encoding);
        }
        this.updateHash(chunk);
        this.byteLength += chunk.length;
        this.push(chunk);
        callback();
    }
    /** @internal */
    _flush(callback) {
        this.updateHash(Buffer.alloc(0), true);
        if (this._lineHasContent) {
            // the body does not end with a line break, add one
            this._hashCanonical(CRLF);
        }
        this.emit('hash', this.bodyHash.digest('base64'), this.debug ? Buffer.concat(this._debugBody) : false);
        callback();
    }
}