xum/src/node/runtime/sshConfigParser.ts at main · coder/xum · GitHub

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/**

* SSH config parsing utilities (ssh-config wrapper).

import { spawnSync } from "child_process";

import * as fs from "fs/promises";

import * as os from "os";

import * as path from "path";

import SSHConfig, { glob } from "ssh-config";

import { log } from "@/node/services/log";

import { getErrorMessage } from "@/common/utils/errors";

interface ParsedValueToken {

val: string;

separator: string;

quoted?: boolean;

}

const DEFAULT_SSH_PORT = 22;

export interface ResolvedSSHConfig {

host: string;

hostName: string;

user?: string;

port: number;

identityFiles: string[];

proxyCommand?: string;

}

function getHomeDir(): string {

return process.env.USERPROFILE ?? os.homedir();

}

function getDefaultUsername(): string {

try {

return os.userInfo().username;

} catch {

return process.env.USER ?? process.env.USERNAME ?? "";

}

function expandHomePath(value: string, homeDir: string): string {

if (value === "~") {

return homeDir;

}

if (value.startsWith("~/") || value.startsWith("~\\")) {

return path.join(homeDir, value.slice(2));

}

return value;

}

function normalizeIdentityFile(value: string, homeDir: string): string {

const expanded = expandHomePath(value, homeDir);

if (path.isAbsolute(expanded)) {

return expanded;

}

return path.join(homeDir, expanded);

}

function parseHostAndUser(host: string): { host: string; user?: string } {

const trimmed = host.trim();

const atIndex = trimmed.lastIndexOf("@");

if (atIndex > 0) {

const user = trimmed.slice(0, atIndex).trim();

const hostname = trimmed.slice(atIndex + 1).trim();

if (user && hostname) {

return { host: hostname, user };

}

return { host: trimmed };

}

function isParsedValueToken(value: unknown): value is ParsedValueToken {

return typeof value === "object" && value !== null && "val" in value && "separator" in value;

}

function tokensToString(tokens: ParsedValueToken[]): string {

return tokens

.map(({ val, separator, quoted }) => {

const rendered = quoted ? `"${val}"` : val;

return `${separator}${rendered}`;

})

.join("")

.trimStart();

}

type ComputedConfigValue = string | string[] | ParsedValueToken[];

function getConfigValue(

config: Record<string, ComputedConfigValue>,

key: string

): ComputedConfigValue | undefined {

const match = Object.entries(config).find(

([configKey]) => configKey.toLowerCase() === key.toLowerCase()

);

return match?.[1];

}

function toStringValue(value: ComputedConfigValue | undefined): string | undefined {

if (typeof value === "string") {

return value;

}

if (Array.isArray(value)) {

const first = value[0];

if (typeof first === "string") {

return first;

}

if (isParsedValueToken(first)) {

return tokensToString(value as ParsedValueToken[]);

}

return undefined;

}

type MatchCriteriaValue = string | Array<{ val: string; separator: string; quoted?: boolean }>;

function getCriteriaValue(

criteria: Record<string, MatchCriteriaValue>,

key: string

): MatchCriteriaValue | undefined {

const match = Object.entries(criteria).find(

([criteriaKey]) => criteriaKey.toLowerCase() === key.toLowerCase()

);

return match?.[1];

}

function criteriaToString(value: MatchCriteriaValue | undefined): string | undefined {

if (typeof value === "string") {

return value;

}

if (Array.isArray(value)) {

return value[0]?.val;

}

return undefined;

}

function criteriaToStringArray(value: MatchCriteriaValue | undefined): string[] {

if (typeof value === "string") {

return [value];

}

if (Array.isArray(value)) {

return value.map(({ val }) => val);

}

return [];

}

function expandMatchExecTokens(command: string, hostName: string, user?: string): string {

return command.replace(/%(%|h|r)/g, (_match, token) => {

switch (token) {

case "%":

return "%";

case "h":

return hostName;

case "r":

return user ?? "";

default:

return _match;

}

});

}

/**

* Handle `Match host ... !exec ...` blocks that ssh-config doesn't evaluate.

* Limitation: Only applies ProxyCommand from matching Match blocks. Other directives

* like User, Port, IdentityFile in the same block are ignored. This is sufficient for

* Coder configs which only set ProxyCommand in Match blocks.

function applyNegatedExecMatch(

config: SSHConfig,

hostName: string,

user: string | undefined,

computed: Record<string, ComputedConfigValue>

): void {

if (getConfigValue(computed, "ProxyCommand")) {

return;

}

for (const line of config) {

if (line.type !== SSHConfig.DIRECTIVE || line.param !== "Match") {

continue;

}

if (!("criteria" in line)) {

continue;

}

const criteria = line.criteria as Record<string, MatchCriteriaValue>;

const hostCriterion = getCriteriaValue(criteria, "host");

const negatedExec = getCriteriaValue(criteria, "!exec");

if (!hostCriterion || !negatedExec) {

continue;

}

const hostPatterns = criteriaToStringArray(hostCriterion);

if (!glob(hostPatterns, hostName)) {

continue;

}

const execCommand = criteriaToString(negatedExec);

if (!execCommand) {

continue;

}

const expandedCommand = expandMatchExecTokens(execCommand, hostName, user);

const execResult = spawnSync(expandedCommand, { shell: true });

if (execResult.status === 0) {

continue;

}

const proxyLine = line.config.find(

(subline) =>

subline.type === SSHConfig.DIRECTIVE && subline.param.toLowerCase() === "proxycommand"

);

if (proxyLine?.type === SSHConfig.DIRECTIVE) {

computed.ProxyCommand = proxyLine.value as ComputedConfigValue;

return;

}

function toStringArray(value: ComputedConfigValue | undefined): string[] {

if (typeof value === "string") {

return [value];

}

if (Array.isArray(value)) {

const first = value[0];

if (typeof first === "string") {

return value as string[];

}

if (isParsedValueToken(first)) {

return [tokensToString(value as ParsedValueToken[])];

}

return [];

}

async function loadSSHConfig(): Promise<SSHConfig | null> {

const homeDir = getHomeDir();

const configPath = path.join(homeDir, ".ssh", "config");

try {

const content = await fs.readFile(configPath, "utf8");

const parsed = SSHConfig.parse(content);

return parsed;

} catch (error) {

if ((error as NodeJS.ErrnoException | undefined)?.code !== "ENOENT") {

log.debug("Failed to read SSH config", {

configPath,

error: getErrorMessage(error),

});

}

return null;

}

export async function resolveSSHConfig(host: string): Promise<ResolvedSSHConfig> {

const { host: hostAlias, user: userOverride } = parseHostAndUser(host);

const homeDir = getHomeDir();

const config = await loadSSHConfig();

const computed = config

? userOverride

? config.compute({ Host: hostAlias, User: userOverride })

: config.compute(hostAlias)

: {};

const hostName = toStringValue(getConfigValue(computed, "HostName")) ?? hostAlias;

const userFromConfig = toStringValue(getConfigValue(computed, "User"));

if (config) {

// Default to local username for %r expansion if no User is specified

const matchExecUser = userOverride ?? userFromConfig ?? getDefaultUsername();

applyNegatedExecMatch(config, hostName, matchExecUser, computed);

}

const portValue = toStringValue(getConfigValue(computed, "Port"));

const identityValues = toStringArray(getConfigValue(computed, "IdentityFile"));

const proxyCommandRaw = toStringValue(getConfigValue(computed, "ProxyCommand"));

const port = portValue ? Number.parseInt(portValue, 10) : DEFAULT_SSH_PORT;

const identityFiles = identityValues.map((value) => normalizeIdentityFile(value, homeDir));

const proxyCommand =

proxyCommandRaw && proxyCommandRaw.toLowerCase() !== "none"

? proxyCommandRaw.trim()

: undefined;

return {

host: hostAlias,

hostName,

user: userOverride ?? userFromConfig,

port: Number.isFinite(port) ? port : DEFAULT_SSH_PORT,

identityFiles,

proxyCommand,

};

}

xum/src/node/runtime/sshConfigParser.ts at main · coder/xum · GitHub

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