Feat: added --install-known-hosts & Fix: Permissons for ssh-cert

This allows users to copy the Host CA Pub key hosts directly into their ~/.ssh/known_hosts

Implemented chmod 600 for /tmp/ssh-cert (CERT_FILE_PATH)

client/gatehouse-cli.py

@@ -279,6 +279,12 @@ def request_certificate():
             json_result = response.json().get('data', response.json())
             with open(CERT_FILE_PATH, 'w') as f:
                 f.write(json_result['certificate'])
+                
+            try:
+                os.chmod(CERT_FILE_PATH, 0o600)
+            except OSError:
+                pass
+                
             logger.info(f"Certificate signed successfully, located at {CERT_FILE_PATH}")
             logger.info(f"Valid for principals: {', '.join(json_result.get('principals', principals))}")
             logger.info("You can login to your destination server with the following command")
@@ -455,6 +461,51 @@ def checkCert():
         logger.warning("Certificate is not valid, renewal required")
         return 1
 
+def install_known_hosts():
+    """Fetch Host CA from the upstream server and install it into ~/.ssh/known_hosts."""
+    try:
+        response = requests.get(f"{SIGN_URL}/api/v1/ssh/ca/public-key?ca_type=host", headers=auth_headers())
+        if response.status_code != 200:
+            logger.error(f"Failed to fetch host CA public key: {response.status_code} - {response.text}")
+            exit(1)
+        
+        ca_data = response.json().get('data', {})
+        public_key = ca_data.get('public_key', '').strip()
+        if not public_key:
+            logger.error("No public key found in the response.")
+            exit(1)
+            
+        known_hosts_path = os.path.expanduser("~/.ssh/known_hosts")
+        ssh_dir = os.path.dirname(known_hosts_path)
+        
+        if not os.path.exists(ssh_dir):
+            os.makedirs(ssh_dir, mode=0o700)
+            
+        # Standard format for OpenSSH cert-authority
+        entry = f"@cert-authority * {public_key}\n"
+        
+        # Check if already present
+        if os.path.exists(known_hosts_path):
+            with open(known_hosts_path, 'r') as f:
+                content = f.read()
+            if public_key in content:
+                logger.info("Host CA public key is already in ~/.ssh/known_hosts. No changes made.")
+                return
+
+        with open(known_hosts_path, 'a') as f:
+            f.write(entry)
+            
+        try:
+            os.chmod(known_hosts_path, 0o600)
+        except OSError:
+            pass  # May not have permission to chmod if owned by root, but let's try
+            
+        logger.info(f"Successfully installed Host CA public key to {known_hosts_path} for all hosts (*)")
+    except Exception as e:
+        logger.error(f"Error during Host CA installation: {e}")
+        exit(1)
+
+
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(description='Sign an SSH key via a web service')
     parser.add_argument("-k", "--ssh-key", type=argparse.FileType('rb'), dest="sshkeyfile", help="Add an SSH Public Key to your user profile in gatehouse")
@@ -465,11 +516,12 @@ if __name__ == "__main__":
     parser.add_argument("--clear-cache", action='store_true', default=False, help="Remove the cached authentication token")
     parser.add_argument("--remove-key", nargs='?', const='', metavar='KEY_ID', help="Remove an SSH key from your profile. Omit KEY_ID to pick interactively.")
     parser.add_argument("--list-keys", action='store_true', default=False, help="List SSH keys in your profile")
+    parser.add_argument("--install-known-hosts", action='store_true', default=False, help="Fetch Host CA public key and install into ~/.ssh/known_hosts")
 
     args = parser.parse_args()
     if not (args.check_cert or args.request_cert or args.add_key or args.clear_cache
-            or args.remove_key is not None or args.list_keys):
+            or args.remove_key is not None or args.list_keys or args.install_known_hosts):
-        parser.error("At least one of --check-cert, --request-cert, --add-key, --list-keys, --remove-key, or --clear-cache must be provided.")
+        parser.error("At least one of --check-cert, --request-cert, --add-key, --list-keys, --remove-key, --clear-cache, or --install-known-hosts must be provided.")
     
 
     # Retrieve SSH key from environment variables if not provided via CLI
@@ -518,6 +570,10 @@ if __name__ == "__main__":
         add_ssh_key(ssh_key_file)                                                                                                              
         exit(0)                                                                                                                                                 
 
+    if args.install_known_hosts:
+        request_token()
+        install_known_hosts()
+        exit(0)
 
     if args.request_cert:
         request_token()