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79 lines
2.8 KiB
Go
79 lines
2.8 KiB
Go
package smtpclient_test
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import (
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"context"
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"crypto/tls"
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"log"
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"log/slog"
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"net"
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"slices"
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"strings"
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"github.com/mjl-/mox/dns"
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"github.com/mjl-/mox/sasl"
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"github.com/mjl-/mox/smtpclient"
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)
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func ExampleClient() {
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// Submit a message to an SMTP server, with authentication. The SMTP server is
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// responsible for getting the message delivered.
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// Make TCP connection to submission server.
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conn, err := net.Dial("tcp", "submit.example.org:465")
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if err != nil {
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log.Fatalf("dial submission server: %v", err)
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}
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defer conn.Close()
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// Initialize the SMTP session, with a EHLO, STARTTLS and authentication.
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// Verify the server TLS certificate with PKIX/WebPKI.
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ctx := context.Background()
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tlsVerifyPKIX := true
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opts := smtpclient.Opts{
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Auth: func(mechanisms []string, cs *tls.ConnectionState) (sasl.Client, error) {
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// If the server is known to support a SCRAM PLUS variant, you should only use
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// that, detecting and preventing authentication mechanism downgrade attacks
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// through TLS channel binding.
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username := "mjl"
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password := "test1234"
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// Prefer strongest authentication mechanism, allow up to older CRAM-MD5.
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if cs != nil && slices.Contains(mechanisms, "SCRAM-SHA-256-PLUS") {
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return sasl.NewClientSCRAMSHA256PLUS(username, password, *cs), nil
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}
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if slices.Contains(mechanisms, "SCRAM-SHA-256") {
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return sasl.NewClientSCRAMSHA256(username, password, true), nil
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}
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if cs != nil && slices.Contains(mechanisms, "SCRAM-SHA-1-PLUS") {
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return sasl.NewClientSCRAMSHA1PLUS(username, password, *cs), nil
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}
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if slices.Contains(mechanisms, "SCRAM-SHA-1") {
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return sasl.NewClientSCRAMSHA1(username, password, true), nil
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}
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if slices.Contains(mechanisms, "CRAM-MD5") {
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return sasl.NewClientCRAMMD5(username, password), nil
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}
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// No mutually supported mechanism found, connection will fail.
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return nil, nil
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},
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}
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localname := dns.Domain{ASCII: "localhost"}
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remotename := dns.Domain{ASCII: "submit.example.org"}
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client, err := smtpclient.New(ctx, slog.Default(), conn, smtpclient.TLSImmediate, tlsVerifyPKIX, localname, remotename, opts)
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if err != nil {
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log.Fatalf("initialize smtp to submission server: %v", err)
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}
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defer client.Close()
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// Send the message to the server, which will add it to its queue.
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req8bitmime := false // ASCII-only, so 8bitmime not required.
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reqSMTPUTF8 := false // No UTF-8 headers, so smtputf8 not required.
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requireTLS := false // Not supported by most servers at the time of writing.
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msg := "From: <mjl@example.org>\r\nTo: <other@example.org>\r\nSubject: hi\r\n\r\nnice to test you.\r\n"
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err = client.Deliver(ctx, "mjl@example.org", "other@example.com", int64(len(msg)), strings.NewReader(msg), req8bitmime, reqSMTPUTF8, requireTLS)
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if err != nil {
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log.Fatalf("submit message to smtp server: %v", err)
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}
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// Message has been submitted.
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}
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