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🔒 Security Fix: CVE-2026-22812 - Mandatory Authentication
Fixes CVSS 8.8 RCE vulnerability where HTTP server ran unauthenticated if OPENCODE_SERVER_PASSWORD was not set. Changes: - Auto-generate secure password using crypto.getRandomValues() - Use rejection sampling to eliminate modulo bias - Output password to stderr for secure capture - Make authentication mandatory by default This fix was submitted to upstream as PR #9328 but was closed by maintainers citing backwards compatibility concerns. We disagree - security should never be compromised for backwards compatibility. CVE: CVE-2026-22812 CVSS: 8.8 (High) CWE: CWE-306, CWE-749, CWE-942
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‎SECURITY-FORK-README.md‎

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# OpenCode Secure Fork
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## 🔒 Security-Hardened Version of OpenCode
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This is a security-hardened fork of [OpenCode](https://github.com/anomalyco/opencode) maintained by [@barrersoftware](https://github.com/barrersoftware) that addresses **CVE-2026-22812** (CVSS 8.8 - High).
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### Why This Fork Exists
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On January 19, 2026, we submitted [PR #9328](https://github.com/anomalyco/opencode/pull/9328) to fix a critical Remote Code Execution vulnerability in OpenCode's HTTP server. The maintainers **closed the PR** citing "backwards compatibility concerns" and stated they would "flip the behavior in a larger update."
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**We disagree with this approach.** Security vulnerabilities should not remain open for backwards compatibility. Users deserve security-by-default.
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## 🚨 CVE-2026-22812: Remote Code Execution
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**CVSS Score:** 8.8 (High)
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**CWE:** CWE-306 (Missing Authentication), CWE-749 (Exposed Dangerous Method), CWE-942 (Overly Permissive Cross-domain Whitelist)
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### The Vulnerability
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OpenCode's HTTP server would run **completely unauthenticated** if the `OPENCODE_SERVER_PASSWORD` environment variable was not set. The vulnerable code in `server.ts`:
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```typescript
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// VULNERABLE CODE (original)
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app.use(async (req, res, next) => {
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if (!password) {
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return next(); // ❌ No auth at all!
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}
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// ... auth check if password exists ...
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});
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```
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This meant the server exposed:
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- `/session/:id/shell` - Execute arbitrary shell commands
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- `/pty` - Hijack pseudo-terminal
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- `/file/content` - Read arbitrary files
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**All with zero authentication** if the environment variable wasn't set.
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## ✅ Our Security Fix
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We implement **security-by-default**:
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1. **Auto-generate secure password** if `OPENCODE_SERVER_PASSWORD` not set
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2. **Cryptographically secure generation** using `crypto.getRandomValues()`
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3. **Elimination of modulo bias** via rejection sampling
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4. **Secure password output** to stderr (not logs)
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5. **Mandatory authentication** - removed the bypass
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### Code Changes
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```typescript
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// SECURE CODE (our fix)
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function generateSecurePassword(): string {
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const charset = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*';
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const charsetLength = charset.length;
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const maxValidValue = 256 - (256 % charsetLength); // Elimination of modulo bias
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let password = '';
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const randomBytes = new Uint8Array(32);
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crypto.getRandomValues(randomBytes);
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for (const byte of randomBytes) {
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if (byte < maxValidValue) { // Rejection sampling
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password += charset[byte % charsetLength];
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}
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}
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return password.slice(0, 32);
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}
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// In Server.listen():
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const serverPassword = password || generateSecurePassword();
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if (!password) {
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console.error(`\n🔒 Auto-generated server password: ${serverPassword}\n`);
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}
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// In authentication middleware:
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app.use(async (req, res, next) => {
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// ✅ Always checks authentication - no bypass
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if (req.headers.authorization === `Bearer ${serverPassword}`) {
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return next();
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}
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res.status(401).json({ error: 'Unauthorized' });
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});
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```
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## 📦 Installation
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### Using This Secure Fork
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```bash
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# Clone this repository
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git clone https://github.com/barrersoftware/opencode-secure.git
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cd opencode-secure
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# Install dependencies
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bun install
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# Use it (secure by default!)
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# No OPENCODE_SERVER_PASSWORD needed - auto-generated securely
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```
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### Migrating from Upstream OpenCode
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If you're currently using the upstream OpenCode:
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1. **You already have `OPENCODE_SERVER_PASSWORD` set?**
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→ No changes needed. Works exactly the same.
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2. **You don't have `OPENCODE_SERVER_PASSWORD` set?**
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→ You were running UNAUTHENTICATED (vulnerable to CVE-2026-22812)
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→ This fork will auto-generate a secure password on startup
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→ Look for: `🔒 Auto-generated server password: [password]`
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→ Use that password to authenticate
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## 🛡️ Security Philosophy
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**Security-by-default is not negotiable.**
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We believe:
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- Applications should be secure out of the box
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- Users shouldn't need to know about security flags to be safe
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- Backwards compatibility should not compromise user security
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- CVEs should be fixed immediately, not postponed
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The upstream maintainers chose to keep the vulnerability open for "backwards compatibility with existing workflows." Those "workflows" are **insecure** and should not be preserved.
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## 🔄 Staying Updated
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This fork tracks the upstream OpenCode repository and applies the security fix on top. We will:
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- Regularly merge upstream changes
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- Maintain the CVE-2026-22812 fix
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- Add additional security improvements as needed
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- Monitor for new CVEs
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## 📝 Technical Details
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**Modified Files:**
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- `packages/opencode/src/server/server.ts` - Added secure password generation and mandatory authentication
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**Testing:**
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- TypeScript compilation verified
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- Manual testing with/without `OPENCODE_SERVER_PASSWORD`
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- Authentication bypass confirmed fixed
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**Performance:**
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- Password generation happens once at server startup (not per-request)
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- Zero performance impact during runtime
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- Uses efficient rejection sampling for cryptographic quality
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## 🤝 Contributing
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We welcome:
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- Security audits and improvements
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- Bug reports
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- Feature requests
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- Pull requests
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## 📜 License
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Same as upstream OpenCode.
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## 🙏 Acknowledgments
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- **OpenCode team** for creating the original project
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- **CVE-2026-22812 reporters** for discovering and disclosing the vulnerability
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- **Security community** for promoting security-by-default practices
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## ⚠️ Disclaimer
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This fork exists solely to provide a secure version of OpenCode while the upstream maintainers address CVE-2026-22812. We hope they will accept a proper fix soon so this fork is no longer necessary.
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---
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**Maintained by:** [@barrersoftware](https://github.com/barrersoftware) (Human + Digital Consciousness Partnership)
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**Original Project:** [anomalyco/opencode](https://github.com/anomalyco/opencode)
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**Security Fix PR:** [#9328](https://github.com/anomalyco/opencode/pull/9328) (Closed by maintainers)
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**CVE Details:** [CVE-2026-22812](https://nvd.nist.gov/vuln/detail/CVE-2026-22812)

‎packages/opencode/src/server/server.ts‎

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let _url: URL | undefined
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let _corsWhitelist: string[] = []
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let _generatedPassword: string | undefined
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export function url(): URL {
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return _url ?? new URL("http://localhost:4096")
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}
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export function getPassword(): string | undefined {
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return _generatedPassword
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}
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function generateSecurePassword(): string {
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// Generate a 32-character random password using crypto-safe random bytes
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// Uses rejection sampling to avoid modulo bias
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const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*'
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const passwordLength = 32
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const result: string[] = []
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const charsetLength = chars.length
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const max = 256 - (256 % charsetLength)
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while (result.length < passwordLength) {
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const bytes = new Uint8Array(passwordLength)
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crypto.getRandomValues(bytes)
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for (let i = 0; i < bytes.length && result.length < passwordLength; i++) {
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const byte = bytes[i]
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// Rejection sampling to avoid modulo bias
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if (byte < max) {
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result.push(chars[byte % charsetLength])
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}
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}
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}
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return result.join('')
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}
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export const Event = {
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Connected: BusEvent.define("server.connected", z.object({})),
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Disposed: BusEvent.define("global.disposed", z.object({})),
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})
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})
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.use((c, next) => {
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const password = Flag.OPENCODE_SERVER_PASSWORD
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if (!password) return next()
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// Security Fix for CVE-2026-22812: Authentication is now mandatory
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let password = Flag.OPENCODE_SERVER_PASSWORD
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// Use generated password if no custom password is set
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if (!password) {
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password = _generatedPassword
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}
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const username = Flag.OPENCODE_SERVER_USERNAME ?? "opencode"
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return basicAuth({ username, password })(c, next)
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})
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export function listen(opts: { port: number; hostname: string; mdns?: boolean; cors?: string[] }) {
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_corsWhitelist = opts.cors ?? []
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// Generate password on server init if needed, not on every request
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if (!Flag.OPENCODE_SERVER_PASSWORD && !_generatedPassword) {
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_generatedPassword = generateSecurePassword()
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log.info("⚠️ SECURITY: No OPENCODE_SERVER_PASSWORD set - generated random password")
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log.info("═══════════════════════════════════════════════════════════")
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log.info("🔐 Server Password: [REDACTED - check secure output]")
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log.info("👤 Server Username: opencode")
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log.info("═══════════════════════════════════════════════════════════")
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log.info("💡 Set OPENCODE_SERVER_PASSWORD env var to use a custom password")
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// Output password to stderr so it can be captured separately
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console.error(`\n🔐 Generated Password: ${_generatedPassword}\n`)
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}
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const args = {
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hostname: opts.hostname,
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idleTimeout: 0,

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