x/crypto/ssh client.NewSession: Provide initial data or an already open channel?
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glenn
Apr 26, 2022, 6:31:31 PM4/26/22
to golang-nuts
I would like to send some initial data when creating a new ssh session. Is there any reason why NewSession doesn't allow callers to do this? Session doesn't export the underlying channel either, so opening a channel and directly initializing the Session isn't an option either.
func (c *Client) NewSession() (*Session, error) {
ch, in, err := c.OpenChannel("session", nil)
if err != nil {
return nil, er
}
return newSession(ch, in)
}
Brian Candler
Apr 27, 2022, 1:48:29 AM4/27/22
to golang-nuts
> Session doesn't export the underlying channel either, so opening a channel and directly initializing the Session isn't an option
Because it isn't meaningful to do this.
As far as I understand it, a session is a type of channel. When you want to open a session, actually you open a channel of type "session". One channel cannot carry multiple sessions, because a session *is* a channel. Equally, you cannot open an untyped channel and then "convert" it to a session later; you have to specify this at the time you create it.
See:
Note that "opening a session" is simply a variant of SSH_MSG_CHANNEL_OPEN, with type "session".
> I would like to send some initial data when creating a new ssh session. Is there any reason why NewSession doesn't allow callers to do this?
Presumably because the session open could fail. You need to wait for the session to be opened successfully before sending data on it.
See:
The remote side then decides whether it can open the channel, and
responds with either SSH_MSG_CHANNEL_OPEN_CONFIRMATION or
SSH_MSG_CHANNEL_OPEN_FAILURE.
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