Pure Go implementation of Assuan IPC protocol.
Assuan protocol is used in GnuPG for communication between following components: gpg, gpg-agent, pinentry, dirmngr. All of them are running as separate processes and need a way to talk with each other. Assuan solves this problem.
Using this library you can talk to gpg-agent or dirmngr directly, invoke pinentry to get password prompt similar to GnuPG's one and even use Assuan as a protocol for your own IPC needs.
Assuan documentation: https://www.gnupg.org/documentation/manuals/assuan/index.html
Main unit of communication in Assuan is a command. Command consists of comamnd name (typically in uppercase) and one or more parameters (represented as one string). Each command sent by client have response with status ("OK" or error) and optional arbitrary data.
In additional to simple commands there are transactions (data inquiries). This is one way to send large data streams from client. Transaction is initiated by command and then server will request data using keywords (actually one keyword per stream). Client can cancel data transmission at any time. At the end of transaction server will send result (OK or error). go-assuan supports optional data stream as a result but this is not in use by any of protocol implementers.
Protocol also specifies file descriptor passing but this is not supported by library yet.
Client side example:
// Connect to dirmngr.
conn, _ := net.Dial("unix", ".gnupg/S.dirmngr")
ses, _ := assuan.Init(conn)
defer ses.Close()
// Search for my key on default keyserver.
data, _ := ses.SimpleCmd("KS_SEARCH", "foxcpp")
fmt.Println(string(data))
// data []byte = "info:1:1%0Apub:2499BEB8B47B0235009A5F0AEE8384B0561A25AF:..."
// More complex transaction: send key to keyserver.
ses.Transact("KS_PUT", "", map[string][]byte{
"KEYBLOCK": []byte{},
"KEYBLOCK_INFO": []byte{},
})Server code is much more complex, see it here.
MIT.