@launchdarkly/mcp-server
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The local [Model Context Protocol (MCP)](https://modelcontextprotocol.io/) server for [LaunchDarkly](https://launchdarkly.com/) federal and European Union (EU) environments.
192 lines • 7.76 kB
JavaScript
import { createHash, X509Certificate } from "node:crypto";
import tls from "node:tls";
/*
* INC-289: rejects TLS chains that go through the compromised eMudhra
* intermediates (https://emudhra.we-have-a-problem.com/). Go 1.26.10, Node.js
* 22.23.4 / 24.22.1 / 26.12.1 and Bun (unreleased, oven-sh/bun#46300) block
* the same keys natively. This check covers runtimes that predate those fixes.
* It is installed only by the `mcp start` CLI, never for library consumers.
*/
/**
* SHA-256 of the DER SubjectPublicKeyInfo of each compromised intermediate.
* Identical to Node.js's kBlockedSPKIs (nodejs/node#66871) and Go's fix
* (CVE-2026-111943). Each key was issued twice, under emSign Root TLS/CS CA -
* G3 and under Sectigo's AAA Certificate Services, so hashing the key rather
* than the certificate covers both.
*/
export const BLOCKED_SPKI_SHA256 = new Set([
"43bffa19d6ef651451f6841e019931e96f6f2eaeff28ab4b6f1ce4576de2717b",
"49dd353dc2b919a3770645117d0e60c16115e7d1bc259eefe734b00ea434fe5f",
"5c0660a2b164910d8ff589c18e14552e9e0ec237dcefe2cb736d41a4811f81a0",
"63ecefee431d49523bc1136c4e72d0206a477086caf606cd5cf025686c109cf8",
"92c063d67e8f14db71d288e11266ffdaf69cbf115f7bab14f3bc2f68d25e0e30",
"e0254c7fcdc265e2f0f8a428dabb75ab4ae039b4872d62f5ee57f0877d5a8a41",
"ebed6475c2c2d80fcb199f3fe8dd6e6b3ce60b77eb15d4e42c3dec0c6f5b5105",
"ec4ffa1ad0ac88081314b7aaffef6a91f97cd57291bb5ba686c5415f5eb4f6b6",
]);
/**
* Common names of the compromised intermediates. Every one of them has
* pathlen:0, so any leaf signed with one of their keys must name the
* intermediate as its issuer. Bun's fetch only exposes the leaf to
* checkServerIdentity, so the issuer name is what blocks these chains there.
*/
const BLOCKED_ISSUER_CN = /^em (dv|ov|ev) (tls|cs) ca - g3[bc]$/;
/**
* Node.js releases that block these keys natively, by major version. Lines
* newer than the highest entry are treated as patched; any other line is
* treated as unpatched.
*/
const FIXED_NODE_VERSIONS = {
22: [22, 23, 4],
24: [24, 22, 1],
26: [26, 12, 1],
};
/**
* First Bun release that blocks these keys natively. Set this once one ships
* (the fix is oven-sh/bun#46300). While it is undefined, every Bun version
* gets the warning.
*/
const FIXED_BUN_VERSION = undefined;
export const BLOCKED_CERT_ERROR_CODE = "ERR_TLS_CERT_BLOCKED";
// Captured before installTlsBlocklist() replaces tls.checkServerIdentity.
const defaultCheckServerIdentity = tls.checkServerIdentity;
function normalizeName(value) {
return value.normalize("NFKC").toLowerCase().replace(/\s+/g, " ").trim();
}
export function isBlockedIssuerName(cn) {
const names = Array.isArray(cn) ? cn : cn === undefined ? [] : [cn];
return names.some((name) => BLOCKED_ISSUER_CN.test(normalizeName(name)));
}
export function spkiSha256(raw) {
const spki = new X509Certificate(raw).publicKey.export({
type: "spki",
format: "der",
});
return createHash("sha256").update(spki).digest("hex");
}
/**
* Walks the peer chain (the full chain on Node.js, the leaf only on Bun) and
* returns a description of the first blocked certificate, if any.
*/
export function findBlockedCertificate(cert) {
const seen = new Set();
for (let current = cert; current && !seen.has(current); current = current.issuerCertificate) {
seen.add(current);
if (isBlockedIssuerName(current.issuer?.CN)) {
return `certificate issued by "${String(current.issuer?.CN)}"`;
}
if (current.raw && current.raw.length > 0) {
const hash = spkiSha256(current.raw);
if (BLOCKED_SPKI_SHA256.has(hash)) {
return `certificate with blocked public key sha256/${hash}`;
}
}
}
return undefined;
}
/**
* A tls checkServerIdentity replacement: rejects blocked chains, then runs
* the runtime's normal hostname verification.
*/
export function checkServerIdentity(hostname, cert) {
let blocked;
try {
blocked = findBlockedCertificate(cert);
}
catch (err) {
blocked = `certificate that could not be parsed (${String(err)})`;
}
if (blocked) {
return Object.assign(new Error(`Refusing TLS connection to ${hostname}: the chain contains a ${blocked}, ` +
"which belongs to a compromised eMudhra intermediate CA."), { code: BLOCKED_CERT_ERROR_CODE });
}
return defaultCheckServerIdentity(hostname, cert);
}
let installed = false;
/**
* Installs the blocklist for this process. On Node.js, global fetch (undici)
* and node:https read tls.checkServerIdentity when they connect. Bun's fetch
* ignores it, so on Bun global fetch is wrapped to pass the check through
* Bun's `tls` fetch option.
*/
export function installTlsBlocklist() {
if (installed)
return;
installed = true;
if (isBun()) {
const originalFetch = globalThis.fetch;
const wrapped = (input, init) => {
const tlsOptions = init?.tls;
const callerCheck = tlsOptions?.checkServerIdentity;
const combined = callerCheck
? (hostname, cert) => checkServerIdentity(hostname, cert) ?? callerCheck(hostname, cert)
: checkServerIdentity;
return originalFetch(input, {
...init,
tls: { ...tlsOptions, checkServerIdentity: combined },
});
};
globalThis.fetch = Object.assign(wrapped, originalFetch);
}
else {
tls.checkServerIdentity =
checkServerIdentity;
}
}
function isBun() {
return typeof globalThis.Bun !== "undefined";
}
function parseVersion(version) {
const match = /^v?(\d+)\.(\d+)\.(\d+)/.exec(version);
if (!match)
return undefined;
return [Number(match[1]), Number(match[2]), Number(match[3])];
}
function compareVersions(a, b) {
return a[0] - b[0] || a[1] - b[1] || a[2] - b[2];
}
export function isNodeVersionPatched(version) {
const parsed = parseVersion(version);
if (!parsed)
return false;
const fixed = FIXED_NODE_VERSIONS[parsed[0]];
if (fixed)
return compareVersions(parsed, fixed) >= 0;
const newestLine = Math.max(...Object.keys(FIXED_NODE_VERSIONS).map(Number));
return parsed[0] > newestLine;
}
export function isBunVersionPatched(version) {
if (FIXED_BUN_VERSION === undefined)
return false;
const parsed = parseVersion(version);
const fixed = parseVersion(FIXED_BUN_VERSION);
return !!parsed && !!fixed && compareVersions(parsed, fixed) >= 0;
}
/**
* Returns a warning when the current runtime does not block the compromised
* eMudhra intermediates natively, or undefined when it does.
*/
export function unpatchedRuntimeWarning(versions = process.versions) {
let runtime;
let upgrade;
if (versions.bun !== undefined) {
if (isBunVersionPatched(versions.bun))
return undefined;
runtime = `Bun ${versions.bun}`;
upgrade =
"run the server with Node.js 22.23.4, 24.22.1, 26.12.1 or later, or use the Docker image";
}
else if (versions.node !== undefined) {
if (isNodeVersionPatched(versions.node))
return undefined;
runtime = `Node.js ${versions.node}`;
upgrade = "upgrade to Node.js 22.23.4, 24.22.1, 26.12.1 or later";
}
else {
return undefined;
}
return (`WARNING: ${runtime} does not block the compromised eMudhra intermediate CAs. ` +
"The LaunchDarkly MCP server rejects them for its own requests, but the runtime does not; " +
`${upgrade}. See https://github.com/launchdarkly/mcp-server#runtime-requirements\n`);
}
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