fix(security): block HOME and ZDOTDIR env override injection

This commit is contained in:
Peter Steinberger
2026-02-22 09:41:55 +01:00
parent ccc00d874c
commit c2c7114ed3
6 changed files with 55 additions and 3 deletions

View File

@@ -25,6 +25,10 @@ enum HostEnvSanitizer {
"LD_",
"BASH_FUNC_",
]
private static let blockedOverrideKeys: Set<String> = [
"HOME",
"ZDOTDIR",
]
private static func isBlocked(_ upperKey: String) -> Bool {
if self.blockedKeys.contains(upperKey) { return true }
@@ -49,6 +53,7 @@ enum HostEnvSanitizer {
// PATH is part of the security boundary (command resolution + safe-bin checks). Never
// allow request-scoped PATH overrides from agents/gateways.
if upper == "PATH" { continue }
if self.blockedOverrideKeys.contains(upper) { continue }
if self.isBlocked(upper) { continue }
merged[key] = value
}

View File

@@ -15,5 +15,6 @@
"IFS",
"SSLKEYLOGFILE"
],
"blockedOverrideKeys": ["HOME", "ZDOTDIR"],
"blockedPrefixes": ["DYLD_", "LD_", "BASH_FUNC_"]
}

View File

@@ -4,6 +4,7 @@ import { describe, expect, it } from "vitest";
type HostEnvSecurityPolicy = {
blockedKeys: string[];
blockedOverrideKeys?: string[];
blockedPrefixes: string[];
};
@@ -27,12 +28,17 @@ describe("host env security policy parity", () => {
const swiftSource = fs.readFileSync(swiftPath, "utf8");
const swiftBlockedKeys = parseSwiftStringArray(swiftSource, "private static let blockedKeys");
const swiftBlockedOverrideKeys = parseSwiftStringArray(
swiftSource,
"private static let blockedOverrideKeys",
);
const swiftBlockedPrefixes = parseSwiftStringArray(
swiftSource,
"private static let blockedPrefixes",
);
expect(swiftBlockedKeys).toEqual(policy.blockedKeys);
expect(swiftBlockedOverrideKeys).toEqual(policy.blockedOverrideKeys ?? []);
expect(swiftBlockedPrefixes).toEqual(policy.blockedPrefixes);
});
});

View File

@@ -1,5 +1,6 @@
import { describe, expect, it } from "vitest";
import {
isDangerousHostEnvOverrideVarName,
isDangerousHostEnvVarName,
normalizeEnvVarKey,
sanitizeHostExecEnv,
@@ -39,10 +40,13 @@ describe("sanitizeHostExecEnv", () => {
const env = sanitizeHostExecEnv({
baseEnv: {
PATH: "/usr/bin:/bin",
HOME: "/tmp/home",
HOME: "/tmp/trusted-home",
ZDOTDIR: "/tmp/trusted-zdotdir",
},
overrides: {
PATH: "/tmp/evil",
HOME: "/tmp/evil-home",
ZDOTDIR: "/tmp/evil-zdotdir",
BASH_ENV: "/tmp/pwn.sh",
SAFE: "ok",
},
@@ -51,7 +55,8 @@ describe("sanitizeHostExecEnv", () => {
expect(env.PATH).toBe("/usr/bin:/bin");
expect(env.BASH_ENV).toBeUndefined();
expect(env.SAFE).toBe("ok");
expect(env.HOME).toBe("/tmp/home");
expect(env.HOME).toBe("/tmp/trusted-home");
expect(env.ZDOTDIR).toBe("/tmp/trusted-zdotdir");
});
it("drops non-portable env key names", () => {
@@ -72,6 +77,15 @@ describe("sanitizeHostExecEnv", () => {
});
});
describe("isDangerousHostEnvOverrideVarName", () => {
it("matches override-only blocked keys case-insensitively", () => {
expect(isDangerousHostEnvOverrideVarName("HOME")).toBe(true);
expect(isDangerousHostEnvOverrideVarName("zdotdir")).toBe(true);
expect(isDangerousHostEnvOverrideVarName("BASH_ENV")).toBe(false);
expect(isDangerousHostEnvOverrideVarName("FOO")).toBe(false);
});
});
describe("normalizeEnvVarKey", () => {
it("normalizes and validates keys", () => {
expect(normalizeEnvVarKey(" OPENROUTER_API_KEY ")).toBe("OPENROUTER_API_KEY");

View File

@@ -4,6 +4,7 @@ const PORTABLE_ENV_VAR_KEY = /^[A-Za-z_][A-Za-z0-9_]*$/;
type HostEnvSecurityPolicy = {
blockedKeys: string[];
blockedOverrideKeys?: string[];
blockedPrefixes: string[];
};
@@ -15,7 +16,13 @@ export const HOST_DANGEROUS_ENV_KEY_VALUES: readonly string[] = Object.freeze(
export const HOST_DANGEROUS_ENV_PREFIXES: readonly string[] = Object.freeze(
HOST_ENV_SECURITY_POLICY.blockedPrefixes.map((prefix) => prefix.toUpperCase()),
);
export const HOST_DANGEROUS_OVERRIDE_ENV_KEY_VALUES: readonly string[] = Object.freeze(
(HOST_ENV_SECURITY_POLICY.blockedOverrideKeys ?? []).map((key) => key.toUpperCase()),
);
export const HOST_DANGEROUS_ENV_KEYS = new Set<string>(HOST_DANGEROUS_ENV_KEY_VALUES);
export const HOST_DANGEROUS_OVERRIDE_ENV_KEYS = new Set<string>(
HOST_DANGEROUS_OVERRIDE_ENV_KEY_VALUES,
);
export function normalizeEnvVarKey(
rawKey: string,
@@ -43,6 +50,14 @@ export function isDangerousHostEnvVarName(rawKey: string): boolean {
return HOST_DANGEROUS_ENV_PREFIXES.some((prefix) => upper.startsWith(prefix));
}
export function isDangerousHostEnvOverrideVarName(rawKey: string): boolean {
const key = normalizeEnvVarKey(rawKey);
if (!key) {
return false;
}
return HOST_DANGEROUS_OVERRIDE_ENV_KEYS.has(key.toUpperCase());
}
export function sanitizeHostExecEnv(params?: {
baseEnv?: Record<string, string | undefined>;
overrides?: Record<string, string> | null;
@@ -82,7 +97,7 @@ export function sanitizeHostExecEnv(params?: {
if (blockPathOverrides && upper === "PATH") {
continue;
}
if (isDangerousHostEnvVarName(upper)) {
if (isDangerousHostEnvVarName(upper) || isDangerousHostEnvOverrideVarName(upper)) {
continue;
}
merged[key] = value;

View File

@@ -26,6 +26,17 @@ describe("node-host sanitizeEnv", () => {
});
});
it("blocks dangerous override-only env keys", () => {
withEnv({ HOME: "/Users/trusted", ZDOTDIR: "/Users/trusted/.zdot" }, () => {
const env = sanitizeEnv({
HOME: "/tmp/evil-home",
ZDOTDIR: "/tmp/evil-zdotdir",
});
expect(env.HOME).toBe("/Users/trusted");
expect(env.ZDOTDIR).toBe("/Users/trusted/.zdot");
});
});
it("drops dangerous inherited env keys even without overrides", () => {
withEnv({ PATH: "/usr/bin:/bin", BASH_ENV: "/tmp/pwn.sh" }, () => {
const env = sanitizeEnv(undefined);