mirror of
https://github.com/foxcpp/maddy.git
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67 lines
2.1 KiB
Go
67 lines
2.1 KiB
Go
/*
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Maddy Mail Server - Composable all-in-one email server.
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Copyright © 2019-2020 Max Mazurov <fox.cpp@disroot.org>, Maddy Mail Server contributors
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package dns
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import (
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"strings"
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"golang.org/x/net/idna"
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"golang.org/x/text/unicode/norm"
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)
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// ForLookup converts the domain into a canonical form suitable for table
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// lookups and other comparisons.
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//
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// TL;DR Use this instead of strings.ToLower to prepare domain for lookups.
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//
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// Domains that contain invalid UTF-8 or invalid A-label
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// domains are simply converted to local-case using strings.ToLower, but the
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// error is also returned.
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func ForLookup(domain string) (string, error) {
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uDomain, err := idna.ToUnicode(domain)
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if err != nil {
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return strings.ToLower(domain), err
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}
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// Side note: strings.ToLower does not support full case-folding, so it is
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// important to apply NFC normalization first.
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uDomain = norm.NFC.String(uDomain)
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uDomain = strings.ToLower(uDomain)
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uDomain = strings.TrimSuffix(uDomain, ".")
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return uDomain, nil
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}
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// Equal reports whether domain1 and domain2 are equivalent as defined by
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// IDNA2008 (RFC 5890).
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//
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// TL;DR Use this instead of strings.EqualFold to compare domains.
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//
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// Equivalence for malformed A-label domains is defined using regular
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// byte-string comparison with case-folding applied.
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func Equal(domain1, domain2 string) bool {
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// Short circult. If they are bit-equivalent, then they are also semantically
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// equivalent.
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if domain1 == domain2 {
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return true
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}
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uDomain1, _ := ForLookup(domain1)
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uDomain2, _ := ForLookup(domain2)
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return uDomain1 == uDomain2
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}
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