tilde-oauth/publicSshToPem.js

103 lines
2.6 KiB
JavaScript

/* eslint no-bitwise: 0 */
function wrap(text, len) {
const length = len || 72;
let result = "";
for (let i = 0; i < text.length; i += length) {
result += text.slice(i, i + length);
result += "\n";
}
return result;
}
function pemPublicKey(key) {
return `---- BEGIN RSA PUBLIC KEY ----\n${wrap(key, 65)}---- END RSA PUBLIC KEY ----`;
}
function integerToOctet(n) {
const result = [];
for (let i = n; i > 0; i >>= 8) {
result.push(i & 0xff);
}
return result.reverse();
}
function asnEncodeLen(n) {
let result = [];
if (n >> 7) {
result = integerToOctet(n);
result.unshift(0x80 + result.length);
} else {
result.push(n);
}
return result;
}
function checkHighestBit(v) {
if (v[0] >> 7 === 1) {
v.unshift(0); // add leading zero if first bit is set
}
return v;
}
function asn1Int(int) {
const v = checkHighestBit(int);
const len = asnEncodeLen(v.length);
return [0x02].concat(len, v); // int tag is 0x02
}
function asn1Seq(seq) {
const len = asnEncodeLen(seq.length);
return [0x30].concat(len, seq); // seq tag is 0x30
}
function arrayToPem(a) {
return window.btoa(a.map(c => String.fromCharCode(c)).join(""));
}
function arrayToString(a) {
return String.fromCharCode.apply(null, a);
}
function stringToArray(s) {
return s.split("").map(c => c.charCodeAt());
}
function pemToArray(pem) {
return stringToArray(window.atob(pem));
}
function arrayToLen(a) {
let result = 0;
for (let i = 0; i < a.length; i += 1) {
result = result * 256 + a[i];
}
return result;
}
function decodePublicKey(s) {
const split = s.split(" ");
const prefix = split[0];
if (prefix !== "ssh-rsa") {
throw new Error(`Unknown prefix: ${prefix}`);
}
const buffer = pemToArray(split[1]);
const nameLen = arrayToLen(buffer.splice(0, 4));
const type = arrayToString(buffer.splice(0, nameLen));
if (type !== "ssh-rsa") {
throw new Error(`Unknown key type: ${type}`);
}
const exponentLen = arrayToLen(buffer.splice(0, 4));
const exponent = buffer.splice(0, exponentLen);
const keyLen = arrayToLen(buffer.splice(0, 4));
const key = buffer.splice(0, keyLen);
return { type, exponent, key, name: split[2] };
}
function publicSshToPem(publicKey) {
const { key, exponent } = decodePublicKey(publicKey);
const seq = [key, exponent].map(asn1Int).reduce((acc, a) => acc.concat(a));
return pemPublicKey(arrayToPem(asn1Seq(seq)));
}
module.exports = { publicSshToPem };