Add templating support (#23)

Author: joohoi

README.md

@@ -8,21 +8,22 @@ it is required to apply multiple encodings to a payload (and possibly inserting
 
 ## Installation
 ```
-go get -u github.com/ffuf/pencode/cmd/pencode
+go install github.com/ffuf/pencode/cmd/pencode
 ```
 
 ### Usage
 
 ```
-pencode - complex payload encoder v0.1
+pencode - complex payload encoder v0.2
 
-Usage: pencode ENCODER1 ENCODER2 ENCODER3...
+Usage: ./pencode ENCODER1 ENCODER2 ENCODER3...
 
-pencode reads input from stdin, which is typically piped from another process.
+./pencode reads input from stdin, which is typically piped from another process.
 
 Available encoders:
   b64decode         - Base64 decoder
   b64encode         - Base64 encoder
+  filename.tmpl     - Replaces string #PAYLOAD# in content of a file that has .tmpl extension.
   hexdecode         - Hex string decoder
   hexencode         - Hex string encoder
   jsonescape        - JSON escape
@@ -36,6 +37,7 @@ Available encoders:
   utf16be           - UTF-16 encoder (Big Endian)
   xmlescape         - XML escape
   xmlunescape       - XML unescape
+
 ```
 
 To urlencode, base64encode and hex encode a string:
@@ -63,6 +65,11 @@ $ echo 'what%ever'|pencode urlencode b64encode hexencode
 - XML escape encoder (reserved characters)
 - XML escape decoder
 
+### Templating
+
+Any command line parameter that is a file path ending with `.tmpl` is considered as a template file by
+pencode. It attempts to read the file content and to replace instances of a string `#PAYLOAD#` within the file with
+the input in the current encoder chain.
 
 ### Shell completion
 

go.mod

@@ -1,3 +1,3 @@
-module "github.com/ffuf/pencode"
+module github.com/ffuf/pencode
 
 go 1.14

pkg/pencode/constants.go

@@ -1,3 +1,3 @@
 package pencode
 
-const VERSION = "0.1"
+const VERSION = "0.2"

pkg/pencode/encoders.go

@@ -8,6 +8,7 @@ import (
 var availableEncoders = map[string]Encoder{
 	"b64encode":        Base64Encoder{},
 	"b64decode":        Base64Decoder{},
+	"filename.tmpl":    Template{},
 	"hexencode":        HexEncoder{},
 	"hexdecode":        HexDecoder{},
 	"jsonescape":       JSONEscaper{},
@@ -40,8 +41,19 @@ func (c *Chain) Initialize(actions []string) error {
 	c.actions = actions
 	c.Encoders = make([]Encoder, 0)
 	for _, a := range actions {
-		if c.HasEncoder(a) {
-			c.Encoders = append(c.Encoders, availableEncoders[a])
+		if ok, err := c.HasEncoder(a); ok {
+			// Templates are a bit special
+			if isTemplate(a) {
+				tenc, err := NewTemplateEncoder(a)
+				if err != nil {
+					return err
+				}
+				c.Encoders = append(c.Encoders, tenc)
+			} else {
+				c.Encoders = append(c.Encoders, availableEncoders[a])
+			}
+		} else if err != nil {
+			return err
 		} else {
 			return fmt.Errorf("Encoder %s requested but not found.\n", a)
 		}
@@ -65,11 +77,15 @@ func (c *Chain) Encode(input []byte) ([]byte, error) {
 }
 
 //HasEncoder returns true if encoder with a specified name is configured
-func (c *Chain) HasEncoder(name string) bool {
+func (c *Chain) HasEncoder(name string) (bool, error) {
 	if _, ok := availableEncoders[name]; ok {
-		return true
+		return true, nil
 	}
-	return false
+	// Check for template
+	if isTemplate(name) {
+		return hasTemplate(name)
+	}
+	return false, nil
 }
 
 func (c *Chain) GetEncoders() []string {

pkg/pencode/template.go

@@ -0,0 +1,47 @@
+package pencode
+
+import (
+	"io/ioutil"
+	"os"
+	"strings"
+)
+
+//isTemplate checks if the name ends with string ".tmpl"
+func isTemplate(name string) bool {
+	return strings.HasSuffix(name, ".tmpl")
+}
+
+//hasTemplate checks if the name points to an existing file
+func hasTemplate(name string) (bool, error) {
+	if _, err := os.Stat(name); err == nil {
+		return true, nil
+	} else {
+		return false, err
+	}
+}
+
+type Template struct {
+	Data []byte
+	Keyword string
+}
+
+func NewTemplateEncoder(name string) (Encoder, error) {
+	var ok bool
+	var err error
+	t := Template{}
+	// Using static keyword for now
+	t.Keyword = "#PAYLOAD#"
+
+	if ok, err = hasTemplate(name); ok {
+		t.Data, err = ioutil.ReadFile(name)
+	}
+	return t, err
+}
+
+func (t Template) Encode(input []byte) ([]byte, error) {
+	return []byte(strings.ReplaceAll(string(t.Data), t.Keyword, string(input))), nil
+}
+
+func (t Template) HelpText() string {
+	return "Replaces string #PAYLOAD# in content of a file that has .tmpl extension."
+}