remctl To-Do List

Protocol:

• Add support for running commands as filters, passing standard input asynchronously from the client. This requires significant re-engineering of the client loop and should wait for better configuration since we don't want to do this with every command. It also introduces out-of-order responses and possible deadlocks to the protocol. docs/protocol-v4 has an initial draft.

• Add a capabilities command to the protocol so that the client can retrieve the list of supported commands rather than assuming based on the protocol version.

• Support locating remctl services via SRV records, probably _remctl._tcp.<hostname>. This will need linking with a resolver library that allows SRV queries. libresolv and res_search is probably the best approach, since that should be portable to any system.

• Modify the server to not allow MESSAGE_COMMAND split in the middle of a length element and require that commands be split in the middle or at the end of argument data.

Server:

• Add a way of explicitly specifying the null command or subcommand in the remctl configuration annd then permit it rather than returning a syntax error.

• Maximum argument count, maximum data size in MESSAGE_COMMAND, and inactivity timeouts for commands should be configurable parameters of the server rather than hard-coded values.

• Support LDAP-based ACLs in addition to file system ACLs. Probably need to support both entitlement and group-based ACLs.

• Add support for external ACL checking programs. If the program exits with a zero status, access is granted. If it exits 1, access is not granted but checking continues. If it exits with any other exit status, access is not granted and checking aborts.

  Ideally, for writing generic ACL checking programs, the program should get the type and service of the remctl command as well as any arguments. However, it would also be good to support passing other arguments into the program as specified in the ACL file.

• Sort the files in a directory before processing them so that the order is deterministic. Affects both configuration (earlier entries override later ones) and ACL rules in the presence of deny ACLs.

• Add a timeout for commands after which the server kills the command.

• The server should call gss_inquire_context to retrieve the mechanism OID and then pass that in to calls to gssapi_error_string rather than hard-coding the Kerberos v5 OID.

• Add option to mask all arguments.

• Track all the children spawned by remctld in stand-alone mode. On receipt of SIGTERM or SIGINT, send SIGUSR1 to all children. In the children, on receipt of SIGUSR1, exit as soon as the current command in progress (if any) stops running. (SIGTERM or SIGINT directly to a child should kill it outright.)

• Support masking the argument following a particular string so that the argument to a particular flag can be masked regardless of its location on the command line.

• Add server support for persistent child processes that the server communicates with over a UNIX domain socket. The best protocol for communication is probably FastCGI, since that will allow the child processes to be written in a wide variety of languages and take advantage of existing libraries. This will probably require a new implementation of the FastCGI server-side protocol.

• In long-running remctld processes, check for configuration file changes and reload the configuration automatically.

• Consider dropping the client remctl connection when the client's authentication credentials have expired. Otherwise, remctld potentially violates the security properties of the Kerberos protocol by using authenticators beyond their stated lifetime.

• Move the core server protocol code into a library so that one can embed a remctl server in other programs.

• Clean up the argv generation code for commands in the server.

Client:

• Implement file upload in the remctl client.

• Add readline support to the remctl client for multiple commands to the same server in the same authenticated session.

• Add an option that prompts the user, with echo disabled, for a piece of secure data, prompting twice to ensure both times match, and then sends that as the last argument to the command. This would be useful for remctl interfaces to change passwords.

• Allow sending the empty command in the command-line client once the server supports it.

• Allow multiple comma-separated hosts to be specified on the command line, resulting in the remctl command being run on each host in turn.

Client library:

• The client should ideally not specify an OID for the authentication mechanism and instead permit GSS-API to negotiate an appropriate mechanism. It should then call gss_inquire_context to retrieve the mechanism OID and then pass that in to calls to gssapi_error_string rather than hard-coding the Kerberos v5 OID.

Go library:

• Incorporate the Go library developed by Thomas Kula.

Perl library:

• Add Net::Remctl::Backend support for obtaining a Kerberos ticket from a given keytab file before running a command.

• Add Net::Remctl::Backend support for creating a PAG and obtaining AFS tokens before running a command.

• Add support for per-command help (possibly extracted from the POD documentation with some additional markup) to implement the help server configuration.

Python library:

• Revise for better Python coding style.

• Sort out type handling fully and stop being so aggressive about supporting multiple ways to specify the commands, instead just requiring an iterable of str or bytes.

• Add enums for streams and protocol error codes.

• Add proper mypy stubs to typeshed and to this package.

• Move API documentation to proper docstrings and use Sphinx to generate the documentation.

• Fix or drop module version information.

• Use a named tuple for the return value of output().

• Use a dataclass for RemctlSimpleResult.

• Add a Python equivalent to Net::Remctl::Backend.

Ruby library:

• Revise for better Ruby coding style.

Rust library:

• Write one.

Language bindings:

• Incorporate the Go bindings for the client library.

Documentation:

• Remove the description of the version 1 remctl protocol from the current protocol specification and put it in its own, separate specification document. Most people will no longer care how this works.

• Submit the remctl protocol as an IETF Internet-Draft.

• Document conventions for the configuration in the remctld manual.

• Rewrite the documentation and protocol specification as a proper manual and format it with Sphinx.

Portability layer:

• Refactor getopt to be easier to understand and less deeply nested.

Test suite:

• Fix tests on a host with only IPv6 addresses. Right now, the test suite assumes remctld will always bind to 127.0.0.1. While fixing this problem, it may be possible to also fix remctld binding to public IP addresses while the test suite runs.

• Incorporate a program that can generate a Kerberos ticket cache from a keytab and use that for running the Kerberos tests instead of requiring the user to generate a keytab.

• Add tests to ensure that no child processes of the remctld server are still running when the test command finishes for cases like server/timeout or server/invalid where we've previously stranded child processes for long periods.

Java implementation:

• Integrate the new Java client implementation.

• Integrate the Java build into the rest of the build system so that it is enabled using an --enable-java flag similar to the bindings, finds maven and a JAVA_HOME in configure, and does the JAR build in the main Makefile using maven.

• Java cannot obtain tickets from a ticket cache created using the k5.conf file included in the java directory using the current MIT Kerberos on Debian. It has to prompt for a password and get tickets itself. Figure out why and fix it.