SSH: Support executing commands and interactive shell with port forwarding

[GGonryun]

This PR enables

• interactive shells & port forwarding: p0 ssh <instance> -L 56789:80
• executing commands & port forwarding: p0 ssh <instance> sleep 10 -L 56789:80
• performing a port forward without allowing commands: p0 ssh <instance> -NL 56789:80

In order to support this behavior a new package ps-tree was added to ensure that grandchild processes spawned by the AWS CLI are cleaned up.

Solves:
https://linear.app/p0-security/issue/ENG-1651/support-p0-ssh-n
https://linear.app/p0-security/issue/ENG-1653/p0-cli-ssh-support-executing-commands-with-port-forwarding

[nbrahms]

Can you remove the package-lock.json please?

[nbrahms]

More stable I think as

Suggested change

	const createSsmCommands = (args: Omit<SsmArgs, "requestId">): string[][] => {
	const createSsmCommands = (args: Omit<SsmArgs, "requestId">): {
	interactiveShellCommand: string[];
	portForwardingCommand: string[];
	} => {

[GGonryun]

I renamed to {shellCommand, subCommand} because the shell command sometimes wont be interactive. It can be the portforwarding command for example p0 ssh <instance> -NL <ports>

[nbrahms]

The type casting here is a little sus. It would be nicer to use typescript overloading. You could get away with just the two variants that you actually used:

const spawnChildProcess = (credential: AwsCredentials, command: string[], stdio: [StdioNull, StdioPipe, StdioPipe]): ChildProcessByStdio<null, Readable, Readable>;
const spawnChildProcess = (credential: AwsCredentials, command: string[], stdio: [StdioNull, StdioNull, StdioNull]): ChildProcessByStdio<null, null, null>;
const spanwChildProcess = (credential: AwsCredentials, command: string[], stdio: [StdioNull, StdioNull | StdioPipe, StdioNull | StdioPipe]): ChildProcessByStdio<null, Readable, Readable> | ChildProcessByStdio<null, null, null> => {
  ...
}

[GGonryun]

TIL! This is much neater.

[GGonryun]

Can you remove the package-lock.json please?

I removed it and I reran yarn add ps-tree because I had previously installed it with npm.

[GGonryun]

TIL! This is much neater.

[GGonryun]

I renamed to {shellCommand, subCommand} because the shell command sometimes wont be interactive. It can be the portforwarding command for example p0 ssh <instance> -NL <ports>

[nbrahms]

Lookin' good 👌