codekingpro/portable-devtools

1"use strict";
2/*
3Copyright 2023 The Sigstore Authors.
4
5Licensed under the Apache License, Version 2.0 (the "License");
6you may not use this file except in compliance with the License.
7You may obtain a copy of the License at
8
9    http://www.apache.org/licenses/LICENSE-2.0
10
11Unless required by applicable law or agreed to in writing, software
12distributed under the License is distributed on an "AS IS" BASIS,
13WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14See the License for the specific language governing permissions and
15limitations under the License.
16*/
17Object.defineProperty(exports, "__esModule", { value: true });
18exports.decodeLength = decodeLength;
19exports.encodeLength = encodeLength;
20const error_1 = require("./error");
21// Decodes the length of a DER-encoded ANS.1 element from the supplied stream.
22// https://learn.microsoft.com/en-us/windows/win32/seccertenroll/about-encoded-length-and-value-bytes
23function decodeLength(stream) {
24    const buf = stream.getUint8();
25    // If the most significant bit is UNSET the length is just the value of the
26    // byte.
27    if ((buf & 0x80) === 0x00) {
28        return buf;
29    }
30    // Otherwise, the lower 7 bits of the first byte indicate the number of bytes
31    // that follow to encode the length.
32    const byteCount = buf & 0x7f;
33    // Ensure the encoded length can safely fit in a JS number.
34    if (byteCount > 6) {
35        throw new error_1.ASN1ParseError('length exceeds 6 byte limit');
36    }
37    // Iterate over the bytes that encode the length.
38    let len = 0;
39    for (let i = 0; i < byteCount; i++) {
40        len = len * 256 + stream.getUint8();
41    }
42    // This is a valid ASN.1 length encoding, but we don't support it.
43    if (len === 0) {
44        throw new error_1.ASN1ParseError('indefinite length encoding not supported');
45    }
46    return len;
47}
48// Translates the supplied value to a DER-encoded length.
49function encodeLength(len) {
50    if (len < 128) {
51        return Buffer.from([len]);
52    }
53    // Bitwise operations on large numbers are not supported in JS, so we need to
54    // use BigInts.
55    let val = BigInt(len);
56    const bytes = [];
57    while (val > 0n) {
58        bytes.unshift(Number(val & 255n));
59        val = val >> 8n;
60    }
61    return Buffer.from([0x80 | bytes.length, ...bytes]);
62}
63