Fix security vulnerabilities: CORS bypass, path traversal, and insecure file permissions

[Copilot]

Addresses multiple security vulnerabilities found during security audit of the codebase.

Changes

CORS Bypass in SSE Endpoint

• Removed hardcoded Access-Control-Allow-Origin: * from setSSEHeaders() that bypassed the CORS middleware configuration

Path Traversal Protection

• Added validateID() function enforcing pattern ^[a-zA-Z0-9]+(-[a-zA-Z0-9]+)*$
• Validates IDs are 1-255 chars, alphanumeric with single hyphens only
• Checks filepath.Base(id) == id to prevent directory traversal
• Applied to all storage operations: Create, Get, AddMessage, Save
• Both MemoryStore and FileStore implementations

File Permissions Hardening

• FileStore directories: 0755 → 0700
• Conversation files: 0644 → 0600

DevMode Warning

• Added log warning when DevMode enables wildcard CORS

Security Scan Results

• CodeQL: 0 alerts
• Dependencies: No known vulnerabilities

Example

// Previously, this would succeed and create files outside dataDir:
store.Create(ctx, "../../../etc/passwd")

// Now returns: invalid entity ID: invalid ID: must be 1-255 alphanumeric characters, may contain hyphens between characters

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• go.googlesource.com
  • Triggering command: /update-job-proxy /update-job-proxy /home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt rtcf�� 0.1-go1.25.0.linux-amd64/src/net 3xEX01Tdr pkg/mod/golang.org/toolchain@v0.0.1-go1.25.0.lin-o s (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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