dovecot: Dovecot authentication package

This patch adds a new package which implements two basic primitives for
authenticating against dovecot ("user exists", and "check password").

It is still experimental/work in progress.

cmd/dovecot-auth-cli/dovecot-auth-cli.go

@@ -0,0 +1,36 @@
+// CLI used for testing the dovecot authentication package.
+//
+// NOT for production use.
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"blitiri.com.ar/go/chasquid/internal/dovecot"
+)
+
+func main() {
+	a := dovecot.NewAuth(os.Args[1]+"-userdb", os.Args[1]+"-client")
+
+	var ok bool
+	var err error
+
+	switch os.Args[2] {
+	case "exists":
+		ok, err = a.Exists(os.Args[3])
+	case "auth":
+		ok, err = a.Authenticate(os.Args[3], os.Args[4])
+	default:
+		fmt.Printf("unknown subcommand\n")
+		os.Exit(1)
+	}
+
+	if ok {
+		fmt.Printf("yes\n")
+		return
+	}
+
+	fmt.Printf("no: %v\n", err)
+	os.Exit(1)
+}