Provided by: greetd_0.9.0-4ubuntu1_amd64 
NAME
greetd-ipc - IPC protocol for greetd
DESCRIPTION
This details the interprocess communication (IPC) protocol for greetd(1). This IPC protocol can be used
to create and manage sessions under greetd.
The IPC protocol uses a UNIX socket as a method of communication. The path to the socket is stored in the
environment variable GREETD_SOCK.
MESSAGE AND REPLY FORMAT
The format for messages and replies is:
<payload-length> <payload>
Where
<payload-length> is a 32-bit integer in native byte order
<payload> is a UTF-8-encoded JSON string.
For example, sending the "create_session" command would look like the following hexdump:
00000000 2c 00 00 00 7b 22 74 79 70 65 22 3a 20 22 63 72 |,...{"type": "cr|
00000010 65 61 74 65 5f 73 65 73 73 69 6f 6e 22 2c 20 22 |eate_session", "|
00000020 75 73 65 72 6e 61 6d 65 22 3a 20 22 6d 65 22 7d |username": "me"}|
MESSAGES
Requests
┌────────────────────────────┬──────────────────────────────┬───────────────────────────────────────────┐
│ MESSAGE TYPE │ FIELDS │ PURPOSE │
├────────────────────────────┼──────────────────────────────┼───────────────────────────────────────────┤
│ create_session │ username (string) │ Creates a session and initiates a login │
│ │ │ attempted for the given user. The session │
│ │ │ is ready to be started if a success is │
│ │ │ returned. │
├────────────────────────────┼──────────────────────────────┼───────────────────────────────────────────┤
│ post_auth_message_response │ response (string, optional) │ Answers an authentication message. If the │
│ │ │ message was informative (info, error), │
│ │ │ then a response does not need to be set │
│ │ │ in this message. The session is ready to │
│ │ │ be started if a success is returned. │
├────────────────────────────┼──────────────────────────────┼───────────────────────────────────────────┤
│ start_session │ cmd (array of strings), env │ Requests for the session to be started │
│ │ (array of strings) │ using the provided command line, adding │
│ │ │ the supplied environment to that created │
│ │ │ by PAM. The session will start after the │
│ │ │ greeter process terminates. │
├────────────────────────────┼──────────────────────────────┼───────────────────────────────────────────┤
│ cancel_session │ │ Cancels the session that is currently │
│ │ │ under configuration. │
└────────────────────────────┴──────────────────────────────┴───────────────────────────────────────────┘
Responses
┌──────────────┬──────────────────────────────┬─────────────────────────────────────────────────────────┐
│ MESSAGE TYPE │ FIELDS │ PURPOSE │
├──────────────┼──────────────────────────────┼─────────────────────────────────────────────────────────┤
│ success │ │ Indicates that the request succeeded. │
├──────────────┼──────────────────────────────┼─────────────────────────────────────────────────────────┤
│ error │ error_type (enum as string), │ Indicates that the request failed. │
│ │ description (string) │ │
├──────────────┼──────────────────────────────┼─────────────────────────────────────────────────────────┤
│ auth_message │ auth_message_type (enum as │ Indicates that an authentication message needs to be │
│ │ string), auth_message │ answered to continue through the authentication flow. │
│ │ (string) │ There are no limits on the number and type of messages │
│ │ │ that may be required for authentication to succeed, and │
│ │ │ a greeter should not make any assumptions about the │
│ │ │ messages. Must be answered with either │
│ │ │ post_auth_message_response or cancel_session. │
└──────────────┴──────────────────────────────┴─────────────────────────────────────────────────────────┘
Authentication message type enums
┌───────────────────┬───────────────────────────────────────┐
│ AUTH MESSAGE TYPE │ PURPOSE │
├───────────────────┼───────────────────────────────────────┤
│ visible │ Indicates that input from the user │
│ │ should be visible when they answer │
│ │ this question. │
├───────────────────┼───────────────────────────────────────┤
│ secret │ Indicates that input from the user │
│ │ should be considered secret when they │
│ │ answer this question. │
├───────────────────┼───────────────────────────────────────┤
│ info │ Indicates that this message is │
│ │ informative, not a question. │
├───────────────────┼───────────────────────────────────────┤
│ error │ Indicates that this message is an │
│ │ error, not a question. │
└───────────────────┴───────────────────────────────────────┘
Error enums
┌────────────┬───────────────────────────────────────┐
│ ERROR TYPE │ PURPOSE │
├────────────┼───────────────────────────────────────┤
│ auth_error │ Indicates that authentication failed. │
│ │ This is not a fatal error, and is │
│ │ likely caused by incorrect │
│ │ credentials. Handle as appropriate. │
├────────────┼───────────────────────────────────────┤
│ error │ A general error. See the error │
│ │ description for more information. │
└────────────┴───────────────────────────────────────┘
AUTHORS
Maintained by Kenny Levinsen <contact@kl.wtf>. For more information about greetd development, see
https://git.sr.ht/~kennylevinsen/greetd.
SEE ALSO
greetd(1)
2023-10-06 greetd-ipc(7)