diff --git a/config/interpolate_funcs.go b/config/interpolate_funcs.go
index 5538763c0ced..0ca16b56cd6a 100644
--- a/config/interpolate_funcs.go
+++ b/config/interpolate_funcs.go
@@ -2,7 +2,9 @@ package config
 
 import (
 	"bytes"
+	"crypto/sha1"
 	"encoding/base64"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"io/ioutil"
@@ -38,6 +40,7 @@ func init() {
 		"lower":        interpolationFuncLower(),
 		"replace":      interpolationFuncReplace(),
 		"split":        interpolationFuncSplit(),
+		"sha1":         interpolationFuncSha1(),
 		"base64encode": interpolationFuncBase64Encode(),
 		"base64decode": interpolationFuncBase64Decode(),
 		"upper":        interpolationFuncUpper(),
@@ -586,3 +589,17 @@ func interpolationFuncUpper() ast.Function {
 		},
 	}
 }
+
+func interpolationFuncSha1() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			s := args[0].(string)
+			h := sha1.New()
+			h.Write([]byte(s))
+			hash := hex.EncodeToString(h.Sum(nil))
+			return hash, nil
+		},
+	}
+}