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5b20cba50a
we don't want external software to include internal details like mlog. slog.Logger is/will be the standard. we still have mlog for its helper functions, and its handler that logs in concise logfmt used by mox. packages that are not meant for reuse still pass around mlog.Log for convenience. we use golang.org/x/exp/slog because we also support the previous Go toolchain version. with the next Go release, we'll switch to the builtin slog.
48 lines
1.5 KiB
Go
48 lines
1.5 KiB
Go
package mox
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import (
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"crypto/tls"
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"fmt"
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"golang.org/x/exp/slog"
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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", slog.Any("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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