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- SSL certs are no longer stored in the host database. This was done not only for security reasons but there is simply no need to do such thing anymore. - The host will longer support multiple SSL certs and will instead have just a single cert for all TCP connections. This required a change to the client header format that simply replaced the the common name with padding. The host will also no longer send the HOST_CERT type id during session initialization. HOST_CERT was also removed as a type id. - The cert and privite key are now pointed to files in the local file system by the environment variables: MRCI_PRIV_KEY and MRCI_PUB_KEY. - The host will still create a default self-signed cert if a valid cert and private key is not defined in the above environmental vars. Since the host only support single certs now, the default cert needed to be expanded to include subject alternative names. The host will try to detect it's WAN ip address using ipify.org and then assign SANs for all detected local LAN interfaces. - Since the cert is now handled by environmental vars and nothing related to it stored in the database, all the core commands related to cert management were removed.
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1.1 The Protocol
The main goal of this application is to transport data from remote TCP clients to the Modules defined in the host. How the data is processed and/or returned back to the client depends entirely on the type of data being transported or the module itself. The data format that the host understands for data transport is referred to as MRCI frames described below in section 1.2.
Before any MRCI frames can be transported, both the host and client need basic information about each other. This is done by having the client send a fixed length client header when it successfully connects to the host and the host will reply with it's own fixed length host header. Descriptions of these headers can be found in sections 1.4 and 1.5.
1.2 MRCI Frames
[type_id][cmd_id][branch_id][data_len][payload]
type_id - 1byte - 8bit little endian integer type id of the payload.
cmd_id - 2bytes - 16bit little endian integer command id.
branch_id - 2bytes - 16bit little endian integer branch id.
data_len - 3bytes - 24bit little endian integer size of the payload.
payload - variable - the actual data to be processed.
notes:
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A full description of the type id's can be found in the Type_IDs.md document.
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Modules call commands via a command name but the host will assign a unique command id to all command names so clients can call them using a simple 2 byte integer instead of full text. The command ids can change as the modules change so it is recommended for clients to not depend on consistant command ids but depend on the ASYNC_ADD_CMD and ASYNC_RM_CMD async commands.
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The branch id is an id that can be assigned by the client itself to run muliple instances of the same command. Commands sent by a certain branch id will result in data sent back to the client from the module with that same branch id.
1.3 Versioning System
The host uses a 4 number versioning system that indicate rev numbers for the host application itself, the tcp interface and the module interface:
[Major][Minor][TCP_Rev][Mod_Rev]
3 . 2 . 1 . 0
Major - this indicate any changes to the host application that would cause
clients to need to change behaviour to maintain compatibility.
changes to the core command names, type id format changes, etc.
will cause the version major to increment.
Minor - this indicate any changes to the host application that clients will
not see and would not need behaviour changes to maintain
compatibility. documentation changes, bug fixes, security patches,
etc. will cause the version minor to increment.
TCP_Rev - this indicate any changes to the MRCI protocol that interface the
host with the clients via the TCP connection. any changes to the
MRCI frames, host/client headers, etc. will cause this rev to
increment.
Mod_Rev - this indicate any changes to the IPC protocol that interface the
host with the modules via named pipes. any changes to the IPC
frames, NEW_CMD/CMD_ID type ids, etc. will cause this rev to
increment.
Any increments to the Major resets the Minor to 0. Any 3rd party client applications connecting to a MRCI host need to be aware of this versioning but does not need to adopt it as it's own version number.
1.4 Client Header
[tag][appName][padding]
tag - 4bytes - 0x4D, 0x52, 0x43, 0x49 (MRCI)
appName - 134bytes - UTF16LE string (padded with 0x00)
padding - 272bytes - padding of 0x00 bytes reserved for future expansion
notes:
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The tag is just a fixed ascii string "MRCI" that indicates to the host that the client is indeed attempting to use the MRCI protocol.
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The appName is the name of the client application that is connected to the host. It can also contain the client's app version if needed because it doesn't follow any particular standard. This string is accessable to all modules so the commands themselves can be made aware of what app the user is currently using.
1.5 Host Header
Format:
[reply][major][minor][tcp_rev][mod_rev][sesId]
reply - 1byte - 8bit little endian unsigned int
major - 2bytes - 16bit little endian unsigned int
minor - 2bytes - 16bit little endian unsigned int
tcp_rev - 2bytes - 16bit little endian unsigned int
mod_rev - 2bytes - 16bit little endian unsigned int
sesId - 28bytes - 224bit sha3 hash
notes:
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reply is a numeric value that the host returns in it's header to communicate to the client if SSL need to initated or not.
- reply = 1, means SSL is not required so the client doesn't need to take any further action.
- reply = 2, means SSL is required to continue so the client needs to send a STARTLS signal.
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sesId is the session id. It is a unique 224bit sha3 hash generated against the current date and time of session creation (down to the msec) and the machine id of the host. This can be used by the host or client to uniquely identify the current session or past sessions.