post filtering

Author: cjimti

cfg.yml

@@ -11,4 +11,15 @@ postBan:
 urlBan:
   [
     'fun',
-  ]
+  ]
+postFilter:
+  -
+    name: taco
+    description: "Match taco."
+    match: 'taco'
+    template: '{{ .Match | shuffle }}'
+  -
+    name: space
+    description: "Match good times."
+    match: 'good.+times'
+    template: '{{ .Match | upper | nospace }}'

rweng/rweng.go

@@ -7,22 +7,38 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"text/template"
 
+	"github.com/Masterminds/sprig"
 	"github.com/go-yaml/yaml"
 	"go.uber.org/zap"
 )
 
+type FilterCfg struct {
+	Name     string `yaml:"name"`
+	Match    string `yaml:"match"`
+	Template string `yaml:"template"`
+}
+
+type FilterTemplate struct {
+	Name     string
+	Match    string
+	Template *template.Template
+}
+
 // EngCfg defines an engine configuration
 type EngCfg struct {
-	PostBan []string `yaml:"postBan"`
-	UrlBan  []string `yaml:"urlBan"`
+	PostBan []string    `yaml:"postBan"`
+	UrlBan  []string    `yaml:"urlBan"`
+	Filter  []FilterCfg `yaml:"postFilter"`
 }
 
 // Eng http.Request rule engine.
 type Eng struct {
 	cfg     EngCfg
 	postBan []*regexp.Regexp
 	urlBan  []*regexp.Regexp
+	filter  map[*regexp.Regexp]FilterTemplate
 	logger  *zap.Logger
 }
 
@@ -32,6 +48,27 @@ func (e *Eng) ProcessRequest(w http.ResponseWriter, r *http.Request) {
 	b, _ := ioutil.ReadAll(r.Body)
 	r.Body.Close()
 
+	// run filter if there is a body
+	if len(b) > 0 {
+		for rgx, filter := range e.filter {
+
+			// find the match first and populate data structure
+			matches := rgx.FindAll(bytes.ToLower(b), len(b))
+			for _, match := range matches {
+				filter.Match = string(match)
+				// send the match to the template
+				var tplReturn bytes.Buffer
+				if err := filter.Template.Execute(&tplReturn, filter); err != nil {
+					// something bad happened
+					e.logger.Error("Filter failed: " + err.Error())
+					continue
+				}
+
+				b = rgx.ReplaceAll(b, tplReturn.Bytes())
+			}
+		}
+	}
+
 	// search for qstring contraband
 	for _, rgx := range e.urlBan {
 		buri := bytes.ToLower([]byte(r.RequestURI))
@@ -89,10 +126,26 @@ func NewEngFromYml(filename string, logger *zap.Logger) (*Eng, error) {
 		urlBan = append(urlBan, rxp)
 	}
 
+	filter := make(map[*regexp.Regexp]FilterTemplate, 0)
+
+	for _, filterCfg := range engCfg.Filter {
+		rxp := regexp.MustCompile(strings.ToLower(filterCfg.Match))
+		tmpl, err := template.New(filterCfg.Name).Funcs(sprig.TxtFuncMap()).Parse(filterCfg.Template)
+		if err != nil {
+			logger.Error("Template parsing error: " + err.Error())
+		}
+
+		filter[rxp] = FilterTemplate{
+			Name:     filterCfg.Name,
+			Template: tmpl,
+		}
+	}
+
 	eng := &Eng{
 		cfg:     engCfg,
 		postBan: postBan,
 		urlBan:  urlBan,
+		filter:  filter,
 		logger:  logger,
 	}