Restrict RPC access to only htm1688 user

[Copilot]

This change implements user access restriction for the Bitcoin Core RPC interface by modifying the authentication system to only allow the user "htm1688" to authenticate, regardless of other configured users.

Changes Made

Modified the CheckUserAuthorized function in src/httprpc.cpp to add a username verification check at the beginning of the authentication process:

// Only allow htm1688 user to access RPC
if (user != "htm1688") {
    return false;
}

Behavior

Before: Any user with valid -rpcauth credentials could access the RPC interface
After: Only the user "htm1688" can access RPC, all other users are immediately rejected

Security Model

• ✅ User "htm1688" with valid password: AUTHORIZED
• ❌ User "htm1688" with invalid password: DENIED
• ❌ Any other username (admin, root, user1, etc.): IMMEDIATELY DENIED
• ❌ Case variations (HTM1688, Htm1688): DENIED (exact match required)

Implementation Details

The change is minimal and surgical:

• Only 4 lines of code added
• No existing functionality removed or modified
• Preserves all password validation logic for the authorized user
• Maintains timing-resistant security practices
• Username check occurs before expensive cryptographic operations

This implementation ensures that regardless of how many users are configured in -rpcauth settings, only "htm1688" will be able to successfully authenticate to the RPC interface.

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:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https (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)

Original prompt

just htm1688 can use.

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