Ilker ManapandClaude Opus 5.5
ebf437a36a
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
65 lines
2.2 KiB
Go
65 lines
2.2 KiB
Go
package onboard
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import (
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"bytes"
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"context"
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"os/exec"
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"runtime"
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)
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// Remote runs a shell command on the machine being onboarded, with input.
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type Remote interface {
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Run(ctx context.Context, script string, stdin []byte) ([]byte, error)
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}
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// SSH is Remote through the system's ssh, so the operator's keys, agent and
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// ~/.ssh/config apply exactly as they do when they log in by hand.
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type SSH struct {
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Addr, User string
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}
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// sshOptions never prompt: a question nobody is there to answer would hang
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// onboarding instead of failing it.
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//
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// accept-new rather than refusing unknown host keys: a machine provisioned a
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// minute ago has a key nobody has seen, and the risk guarded against is a
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// substituted machine, whose changed key is still refused.
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var sshOptions = []string{
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"-o", "BatchMode=yes",
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"-o", "ConnectTimeout=10",
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"-o", "StrictHostKeyChecking=accept-new",
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"-o", "ServerAliveInterval=15",
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// "Permanently added … to the list of known hosts" and the like are
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// for a person at a prompt; here they would be read as the answer.
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"-o", "LogLevel=ERROR",
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}
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// Run runs script with sh on the machine. Files travel on standard input,
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// not scp, which a hardened sshd may not offer.
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func (s *SSH) Run(ctx context.Context, script string, stdin []byte) ([]byte, error) {
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target := s.Addr
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if s.User != "" {
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target = s.User + "@" + s.Addr
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}
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// "--" before the target: an address beginning with "-" is not read as
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// an option.
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args := append(append([]string{}, sshOptions...), "--", target, "sh", "-c", shellQuote(script))
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cmd := exec.CommandContext(ctx, "ssh", args...)
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if stdin != nil {
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cmd.Stdin = bytes.NewReader(stdin)
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}
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// The answer is standard output alone: ssh and the machine's login
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// scripts write to standard error, and mixed in they were taken for the
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// answer — the first connection's "Warning: Permanently added" read as
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// the machine's hostname. Standard error comes back only with a failure,
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// where it is usually the reason.
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var stdout, stderr bytes.Buffer
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cmd.Stdout, cmd.Stderr = &stdout, &stderr
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if err := cmd.Run(); err != nil {
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return append(stdout.Bytes(), stderr.Bytes()...), err
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}
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return stdout.Bytes(), nil
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}
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func hostArch() string { return runtime.GOARCH }
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