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logging: add replace filter for static value replacement (#4029)

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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
This commit is contained in:
Aaron Taylor 2021-03-12 15:01:34 -05:00 committed by GitHub
parent 2a127ac3d1
commit f137b82227
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 36 additions and 3 deletions
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5
caddytest/integration/caddyfile_adapt/log_filters.txt
View file

@ -5,7 +5,7 @@ log {
format filter {
wrap console
fields {
request>headers>Authorization delete
request>headers>Authorization replace REDACTED
request>headers>Server delete
request>remote_addr ip_mask {
ipv4 24
@ -30,7 +30,8 @@ log {
"encoder": {
"fields": {
"request\u003eheaders\u003eAuthorization": {
"filter": "delete"
"filter": "replace",
"value": "REDACTED"
},
"request\u003eheaders\u003eServer": {
"filter": "delete"

32
modules/logging/filters.go
View file

@ -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 {