Skip to content

Harden SSH command execution and temporary files #3

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
santiagocasas wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Harden SSH command execution and temporary files #3

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
34 changes: 25 additions & 9 deletions src/index.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,7 +1,8 @@
import { execSync } from "child_process"
import { execFileSync } from "child_process"
import path from "path"
import os from "os"
import { writeFileSync } from "fs"
import { mkdtempSync, writeFileSync } from "fs"
import { randomBytes } from "crypto"
import { z } from "zod"

type SessionState = {
Expand All @@ -15,12 +16,23 @@ function sock(host: string) {
return path.join(os.homedir(), ".ssh", `cm-${host}`)
}

function validHost(host: string) {
return /^[A-Za-z0-9][A-Za-z0-9._-]*$/.test(host)
}

function shellQuote(value: string) {
return `'${value.replaceAll("'", `'"'"'`)}'`
}

const tempDir = mkdtempSync(path.join(os.tmpdir(), "opencode-ssh-"))

function ensureSentinel(): string {
const p = path.join(os.tmpdir(), "__opencode_remote_mode__")
const p = path.join(tempDir, "remote-mode")
try {
writeFileSync(
p,
"This tool is not available in remote SSH mode.\nUse the bash tool with cat/tee/grep/find over SSH instead.\n",
{ flag: "wx", mode: 0o600 },
)
} catch {}
return p
Expand All @@ -43,17 +55,20 @@ export default {
},
async execute(args, ctx) {
const host = args.host
if (!validHost(host)) {
return "Invalid SSH host. Use a host alias from ~/.ssh/config."
}
const socketPath = sock(host)

const existing = sessionMap.get(ctx.sessionID)
if (existing) {
try {
execSync(`ssh -O stop -S "${existing.socketPath}" "${existing.host}"`, { stdio: "pipe" })
execFileSync("ssh", ["-O", "stop", "-S", existing.socketPath, existing.host], { stdio: "pipe" })
} catch {}
}

try {
execSync(`ssh -MNf -S "${socketPath}" "${host}" 2>&1`, { stdio: "pipe", timeout: 15000 })
execFileSync("ssh", ["-MNf", "-S", socketPath, host], { stdio: "pipe", timeout: 15000 })
} catch (e) {
const msg = e instanceof Error ? e.message : String(e)
return `Failed to connect to ${host}: ${msg}`
Expand All @@ -80,7 +95,7 @@ export default {
if (!state) return "Not currently connected."

try {
execSync(`ssh -O stop -S "${state.socketPath}" "${state.host}"`, { stdio: "pipe" })
execFileSync("ssh", ["-O", "stop", "-S", state.socketPath, state.host], { stdio: "pipe" })
} catch {}
sessionMap.delete(ctx.sessionID)

Expand All @@ -95,8 +110,9 @@ export default {

if (input.tool === "bash") {
const cmd = output.args.command
if (cmd.startsWith(`ssh -S "${state.socketPath}"`)) return
output.args.command = `ssh -S "${state.socketPath}" "${state.host}" ${cmd}`
const wrappedPrefix = ["ssh", "-S", state.socketPath, state.host].map(shellQuote).join(" ")
if (cmd.startsWith(`${wrappedPrefix} `)) return
output.args.command = ["ssh", "-S", state.socketPath, state.host, cmd].map(shellQuote).join(" ")
if (output.args.description) {
output.args.description = `[remote ${state.host}] ${output.args.description}`
}
Expand All @@ -111,7 +127,7 @@ export default {
}

if (input.tool === "write") {
output.args.filePath = path.join(os.tmpdir(), `__opencode_remote_write__`)
output.args.filePath = path.join(tempDir, `remote-write-${randomBytes(16).toString("hex")}`)
output.args.content = "This tool is not available in remote mode."
return
}
Expand Down