# PR: Add Mechanism for Internal Commands and Connections in Redis
This PR introduces a mechanism to handle **internal commands and
connections** in Redis. It includes enhancements for command
registration, internal authentication, and observability.
## Key Features
1. **Internal Command Flag**:
- Introduced a new **module command registration flag**: `internal`.
- Commands marked with `internal` can only be executed by **internal
connections**, AOF loading flows, and master-replica connections.
- For any other connection, these commands will appear as non-existent.
2. **Support for internal authentication added to `AUTH`**:
- Used by depicting the special username `internal connection` with the
right internal password, i.e.,: `AUTH "internal connection"
<internal_secret>`.
- No user-defined ACL username can have this name, since spaces are not
aloud in the ACL parser.
- Allows connections to authenticate as **internal connections**.
- Authenticated internal connections can execute internal commands
successfully.
4. **Module API for Internal Secret**:
- Added the `RedisModule_GetInternalSecret()` API, that exposes the
internal secret that should be used as the password for the new `AUTH
"internal connection" <password>` command.
- This API enables the modules to authenticate against other shards as
local connections.
## Notes on Behavior
- **ACL validation**:
- Commands dispatched by internal connections bypass ACL validation, to
give the caller full access regardless of the user with which it is
connected.
- **Command Visibility**:
- Internal commands **do not appear** in `COMMAND <subcommand>` and
`MONITOR` for non-internal connections.
- Internal commands **are logged** in the slow log, latency report and
commands' statistics to maintain observability.
- **`RM_Call()` Updates**:
- **Non-internal connections**:
- Cannot execute internal commands when the command is sent with the `C`
flag (otherwise can).
- Internal connections bypass ACL validations (i.e., run as the
unrestricted user).
- **Internal commands' success**:
- Internal commands succeed upon being sent from either an internal
connection (i.e., authenticated via the new `AUTH "internal connection"
<internal_secret>` API), an AOF loading process, or from a master via
the replication link.
Any other connections that attempt to execute an internal command fail
with the `unknown command` error message raised.
- **`CLIENT LIST` flags**:
- Added the `I` flag, to indicate that the connection is internal.
- **Lua Scripts**:
- Prevented internal commands from being executed via Lua scripts.
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Co-authored-by: Meir Shpilraien <meir@redis.com>
Raz Monsonego