From f137b82227f7b32b2ca036a89068c806a29a5ac7 Mon Sep 17 00:00:00 2001 From: Aaron Taylor Date: Fri, 12 Mar 2021 15:01:34 -0500 Subject: logging: add replace filter for static value replacement (#4029) This filter is intended to be useful in scenarios where you may want to redact a value with a static string, giving you information that the field did previously exist and was present, but not revealing the value itself in the logs. This was inspired by work on adding more complete support for removing sensitive values from logs [1]. An example use case would be the Authorization header in request log output, for which the value should usually not be logged, but it may be quite useful for debugging to confirm that the header was present in the request. [1] https://github.com/caddyserver/caddy/issues/3958 --- modules/logging/filters.go | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'modules/logging') diff --git a/modules/logging/filters.go b/modules/logging/filters.go index a5a917d..a4e3c73 100644 --- a/modules/logging/filters.go +++ b/modules/logging/filters.go @@ -25,6 +25,7 @@ import ( func init() { caddy.RegisterModule(DeleteFilter{}) + caddy.RegisterModule(ReplaceFilter{}) caddy.RegisterModule(IPMaskFilter{}) } @@ -57,6 +58,37 @@ func (DeleteFilter) Filter(in zapcore.Field) zapcore.Field { return in } +// ReplaceFilter is a Caddy log field filter that +// replaces the field with the indicated string. +type ReplaceFilter struct { + Value string `json:"value,omitempty"` +} + +// CaddyModule returns the Caddy module information. +func (ReplaceFilter) CaddyModule() caddy.ModuleInfo { + return caddy.ModuleInfo{ + ID: "caddy.logging.encoders.filter.replace", + New: func() caddy.Module { return new(ReplaceFilter) }, + } +} + +// UnmarshalCaddyfile sets up the module from Caddyfile tokens. +func (f *ReplaceFilter) UnmarshalCaddyfile(d *caddyfile.Dispenser) error { + for d.Next() { + if d.NextArg() { + f.Value = d.Val() + } + } + return nil +} + +// Filter filters the input field with the replacement value. +func (f *ReplaceFilter) Filter(in zapcore.Field) zapcore.Field { + in.Type = zapcore.StringType + in.String = f.Value + return in +} + // IPMaskFilter is a Caddy log field filter that // masks IP addresses. type IPMaskFilter struct { -- cgit v1.2.3