mirror of
https://github.com/mjl-/mox.git
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47 lines
1.5 KiB
Go
47 lines
1.5 KiB
Go
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package message
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import (
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"crypto/tls"
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"fmt"
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"github.com/mjl-/mox/mlog"
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)
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// TLSReceivedComment returns a comment about TLS of the connection for use in a Receive header.
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func TLSReceivedComment(log *mlog.Log, cs tls.ConnectionState) []string {
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// todo future: we could use the "tls" clause for the Received header as specified in ../rfc/8314:496. however, the text implies it is only for submission, not regular smtp. and it cannot specify the tls version. for now, not worth the trouble.
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// Comments from other mail servers:
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// gmail.com: (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128)
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// yahoo.com: (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256)
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// proton.me: (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested)
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// outlook.com: (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384)
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var l []string
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add := func(s string) {
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l = append(l, s)
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}
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versions := map[uint16]string{
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tls.VersionTLS10: "TLS1.0",
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tls.VersionTLS11: "TLS1.1",
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tls.VersionTLS12: "TLS1.2",
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tls.VersionTLS13: "TLS1.3",
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}
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if version, ok := versions[cs.Version]; ok {
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add(version)
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} else {
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log.Info("unknown tls version identifier", mlog.Field("version", cs.Version))
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add(fmt.Sprintf("TLS identifier %x", cs.Version))
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}
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add(tls.CipherSuiteName(cs.CipherSuite))
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// Make it a comment.
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l[0] = "(" + l[0]
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l[len(l)-1] = l[len(l)-1] + ")"
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return l
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}
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