add two new log levels for tracing sensitive auth protocol messages, and bulk data messages

named "traceauth" and "tracedata".

with this, you can (almost) enable trace logging without fear of logging
sensitive data or ddos'ing your log server.

the caveat is that the imap login command has already printed the line as
regular trace before we can decide it should not be. can be fixed soon.

mlog/log.go

@@ -39,30 +39,36 @@ var Logfmt bool
 type Level int
 
 var LevelStrings = map[Level]string{
-	LevelPrint: "print",
-	LevelFatal: "fatal",
-	LevelError: "error",
-	LevelInfo:  "info",
-	LevelDebug: "debug",
-	LevelTrace: "trace",
+	LevelPrint:     "print",
+	LevelFatal:     "fatal",
+	LevelError:     "error",
+	LevelInfo:      "info",
+	LevelDebug:     "debug",
+	LevelTrace:     "trace",
+	LevelTraceauth: "traceauth",
+	LevelTracedata: "tracedata",
 }
 
 var Levels = map[string]Level{
-	"print": LevelPrint,
-	"fatal": LevelFatal,
-	"error": LevelError,
-	"info":  LevelInfo,
-	"debug": LevelDebug,
-	"trace": LevelTrace,
+	"print":     LevelPrint,
+	"fatal":     LevelFatal,
+	"error":     LevelError,
+	"info":      LevelInfo,
+	"debug":     LevelDebug,
+	"trace":     LevelTrace,
+	"traceauth": LevelTraceauth,
+	"tracedata": LevelTracedata,
 }
 
 const (
-	LevelPrint Level = 0 // Printed regardless of configured log level.
-	LevelFatal Level = 1 // Printed regardless of configured log level.
-	LevelError Level = 2
-	LevelInfo  Level = 3
-	LevelDebug Level = 4
-	LevelTrace Level = 5
+	LevelPrint     Level = 0 // Printed regardless of configured log level.
+	LevelFatal     Level = 1 // Printed regardless of configured log level.
+	LevelError     Level = 2
+	LevelInfo      Level = 3
+	LevelDebug     Level = 4
+	LevelTrace     Level = 5
+	LevelTraceauth Level = 6
+	LevelTracedata Level = 7
 )
 
 // Holds a map[string]Level, mapping a package (field pkg in logs) to a log level.
@@ -144,8 +150,8 @@ func (l *Log) MoreFields(fn func() []Pair) *Log {
 	return &nl
 }
 
-func (l *Log) Trace(text string) bool {
-	return l.logx(LevelTrace, nil, text)
+func (l *Log) Trace(traceLevel Level, text string) bool {
+	return l.logx(traceLevel, nil, text)
 }
 
 func (l *Log) Fatal(text string, fields ...Pair) { l.Fatalx(text, nil, fields...) }
@@ -181,9 +187,18 @@ func (l *Log) Errorx(text string, err error, fields ...Pair) bool {
 }
 
 func (l *Log) logx(level Level, err error, text string, fields ...Pair) bool {
-	if !l.match(level) {
+	if ok, high := l.match(level); ok {
+		// Nothing.
+	} else if high >= LevelTrace && level == LevelTraceauth {
+		text = "***"
+	} else if high >= LevelTrace && level == LevelTracedata {
+		text = "..."
+	} else {
 		return false
 	}
+	if level > LevelTrace {
+		level = LevelTrace
+	}
 	l.plog(level, err, text, fields...)
 	return true
 }
@@ -327,14 +342,15 @@ func (l *Log) plog(level Level, err error, text string, fields ...Pair) {
 	os.Stderr.Write(b.Bytes())
 }
 
-func (l *Log) match(level Level) bool {
+func (l *Log) match(level Level) (bool, Level) {
 	if level == LevelPrint || level == LevelFatal {
-		return true
+		return true, level
 	}
 
 	cl := config.Load().(map[string]Level)
 
 	seen := false
+	var high Level
 	for _, kv := range l.fields {
 		if kv.key != "pkg" {
 			continue
@@ -344,16 +360,22 @@ func (l *Log) match(level Level) bool {
 			continue
 		}
 		v, ok := cl[pkg]
+		if v > high {
+			high = v
+		}
 		if ok && v >= level {
-			return true
+			return true, high
 		}
 		seen = seen || ok
 	}
 	if seen {
-		return false
+		return false, high
 	}
 	v, ok := cl[""]
-	return ok && v >= level
+	if v > high {
+		high = v
+	}
+	return ok && v >= level, v
 }
 
 type errWriter struct {