37 lines
1.1 KiB
Go
37 lines
1.1 KiB
Go
package acmecert
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import (
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"context"
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"fmt"
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"io"
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"net/http"
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"strings"
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)
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// wanIPServiceURL returns the caller's public IP as plain text. Overridden by tests.
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var wanIPServiceURL = "https://api.ipify.org"
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// DetectWANIP asks a public IP-echo service what address this host is reachable from,
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// for pre-filling the Let's Encrypt HTTP-01 "certificate for my IP" option. There's no
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// stdlib or local way to learn a WAN-facing IP from behind NAT/a cloud LB, so an
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// outbound HTTP call is the only option here.
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func DetectWANIP(ctx context.Context) (string, error) {
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req, err := http.NewRequestWithContext(ctx, http.MethodGet, wanIPServiceURL, nil)
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if err != nil {
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return "", err
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}
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resp, err := http.DefaultClient.Do(req)
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if err != nil {
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return "", fmt.Errorf("detect WAN IP: %w", err)
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}
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defer resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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return "", fmt.Errorf("detect WAN IP: unexpected status %s", resp.Status)
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}
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body, err := io.ReadAll(io.LimitReader(resp.Body, 256))
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if err != nil {
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return "", fmt.Errorf("detect WAN IP: %w", err)
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}
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return strings.TrimSpace(string(body)), nil
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}
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