config: Add new interpolation function - md5

config/interpolate_funcs.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"bytes"
+	"crypto/md5"
 	"crypto/sha1"
 	"crypto/sha256"
 	"encoding/base64"
@@ -40,6 +41,7 @@ func Funcs() map[string]ast.Function {
 		"join":         interpolationFuncJoin(),
 		"length":       interpolationFuncLength(),
 		"lower":        interpolationFuncLower(),
+		"md5":          interpolationFuncMd5(),
 		"replace":      interpolationFuncReplace(),
 		"sha1":         interpolationFuncSha1(),
 		"sha256":       interpolationFuncSha256(),
@@ -599,6 +601,20 @@ func interpolationFuncLower() ast.Function {
 	}
 }
 
+func interpolationFuncMd5() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			s := args[0].(string)
+			h := md5.New()
+			h.Write([]byte(s))
+			hash := hex.EncodeToString(h.Sum(nil))
+			return hash, nil
+		},
+	}
+}
+
 // interpolationFuncUpper implements the "upper" function that does
 // string upper casing.
 func interpolationFuncUpper() ast.Function {

config/interpolate_funcs_test.go

@@ -923,6 +923,28 @@ func TestInterpolateFuncBase64Sha256(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncMd5(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${md5("tada")}`,
+				"ce47d07243bb6eaf5e1322c81baf9bbf",
+				false,
+			},
+			{ // Confirm that we're not trimming any whitespaces
+				`${md5(" tada ")}`,
+				"aadf191a583e53062de2d02c008141c4",
+				false,
+			},
+			{ // We accept empty string too
+				`${md5("")}`,
+				"d41d8cd98f00b204e9800998ecf8427e",
+				false,
+			},
+		},
+	})
+}
+
 type testFunctionConfig struct {
 	Cases []testFunctionCase
 	Vars  map[string]ast.Variable