25 lines
598 B
Go
25 lines
598 B
Go
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package dns01
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import (
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"fmt"
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"strings"
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"github.com/miekg/dns"
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)
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// ExtractSubDomain extracts the subdomain part from a domain and a zone.
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func ExtractSubDomain(domain, zone string) (string, error) {
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canonDomain := dns.Fqdn(domain)
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canonZone := dns.Fqdn(zone)
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if canonDomain == canonZone {
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return "", fmt.Errorf("no subdomain because the domain and the zone are identical: %s", canonDomain)
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}
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if !dns.IsSubDomain(canonZone, canonDomain) {
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return "", fmt.Errorf("%s is not a subdomain of %s", canonDomain, canonZone)
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}
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return strings.TrimSuffix(canonDomain, "."+canonZone), nil
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}
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