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https://blitiri.com.ar/repos/chasquid
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2943f994e7
There are a few context.WithDeadline calls that can be simplified by using context.WithTimeout. At the time they were added, WithTimeout was too new so we didn't want to depend on it. But now that the minimum Go version has been raised to 1.9, we can simplify the calls. This patch does that simplification, which is purely mechanical, and does not change the logic itself.
106 lines
2.8 KiB
Go
106 lines
2.8 KiB
Go
package courier
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import (
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"bytes"
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"context"
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"fmt"
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"os/exec"
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"strings"
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"syscall"
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"time"
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"unicode"
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"blitiri.com.ar/go/chasquid/internal/envelope"
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"blitiri.com.ar/go/chasquid/internal/trace"
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)
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var (
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errTimeout = fmt.Errorf("operation timed out")
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)
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// Procmail delivers local mail by executing a local binary, like procmail or
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// maildrop. It is named after procmail just for reference, it works with any
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// binary that:
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// - Receives the email to deliver via stdin.
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// - Exits with code EX_TEMPFAIL (75) for transient issues.
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type Procmail struct {
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Binary string // Path to the binary.
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Args []string // Arguments to pass.
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Timeout time.Duration // Timeout for each invocation.
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}
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// Deliver an email. On failures, returns an error, and whether or not it is
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// permanent.
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func (p *Procmail) Deliver(from string, to string, data []byte) (error, bool) {
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tr := trace.New("Courier.Procmail", to)
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defer tr.Finish()
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// Sanitize, just in case.
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from = sanitizeForProcmail(from)
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to = sanitizeForProcmail(to)
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tr.Debugf("%s -> %s", from, to)
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// Prepare the command, replacing the necessary arguments.
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replacer := strings.NewReplacer(
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"%from%", from,
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"%from_user%", envelope.UserOf(from),
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"%from_domain%", envelope.DomainOf(from),
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"%to%", to,
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"%to_user%", envelope.UserOf(to),
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"%to_domain%", envelope.DomainOf(to),
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)
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args := []string{}
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for _, a := range p.Args {
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args = append(args, replacer.Replace(a))
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}
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tr.Debugf("%s %q", p.Binary, args)
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ctx, cancel := context.WithTimeout(context.Background(), p.Timeout)
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defer cancel()
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cmd := exec.CommandContext(ctx, p.Binary, args...)
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cmd.Stdin = bytes.NewReader(data)
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output, err := cmd.CombinedOutput()
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if ctx.Err() == context.DeadlineExceeded {
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return tr.Error(errTimeout), false
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}
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if err != nil {
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// Determine if the error is permanent or not.
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// Default to permanent, but error code 75 is transient by general
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// convention (/usr/include/sysexits.h), and commonly relied upon.
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permanent := true
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if exiterr, ok := err.(*exec.ExitError); ok {
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if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
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permanent = status.ExitStatus() != 75
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}
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}
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err = tr.Errorf("procmail failed: %v - %q", err, string(output))
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return err, permanent
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}
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tr.Debugf("delivered")
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return nil, false
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}
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// sanitizeForProcmail cleans the string, removing characters that could be
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// problematic considering we will run an external command.
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//
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// The server does not rely on this to do substitution or proper filtering,
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// that's done at a different layer; this is just for defense in depth.
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func sanitizeForProcmail(s string) string {
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valid := func(r rune) rune {
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switch {
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case unicode.IsSpace(r), unicode.IsControl(r),
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strings.ContainsRune("/;\"'\\|*&$%()[]{}`!", r):
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return rune(-1)
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default:
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return r
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}
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}
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return strings.Map(valid, s)
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}
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