Add a sha256(...) interpolation function.

config/interpolate_funcs.go

@@ -3,6 +3,7 @@ package config
 import (
 	"bytes"
 	"crypto/sha1"
+	"crypto/sha256"
 	"encoding/base64"
 	"encoding/hex"
 	"errors"
@@ -39,6 +40,7 @@ func Funcs() map[string]ast.Function {
 		"replace":      interpolationFuncReplace(),
 		"split":        interpolationFuncSplit(),
 		"sha1":         interpolationFuncSha1(),
+		"sha256":       interpolationFuncSha256(),
 		"base64encode": interpolationFuncBase64Encode(),
 		"base64decode": interpolationFuncBase64Decode(),
 		"upper":        interpolationFuncUpper(),
@@ -601,3 +603,17 @@ func interpolationFuncSha1() ast.Function {
 		},
 	}
 }
+
+func interpolationFuncSha256() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			s := args[0].(string)
+			h := sha256.New()
+			h.Write([]byte(s))
+			hash := hex.EncodeToString(h.Sum(nil))
+			return hash, nil
+		},
+	}
+}

config/interpolate_funcs_test.go

@@ -846,6 +846,18 @@ func TestInterpolateFuncSha1(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncSha256(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${sha256("test")}`,
+				"9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08",
+				false,
+			},
+		},
+	})
+}
+
 type testFunctionConfig struct {
 	Cases []testFunctionCase
 	Vars  map[string]ast.Variable

website/source/docs/configuration/interpolation.html.md

@@ -80,10 +80,14 @@ The supported built-in functions are:
   * `base64encode(string)` - Returns a base64-encoded representation of the
     given string.
 
-  * `sha1(string)` - Returns a sha1 hash representation of the
+  * `sha1(string)` - Returns a SHA-1 hash representation of the
     given string.
     Example: `"${sha1(concat(aws_vpc.default.tags.customer, "-s3-bucket"))}"`
 
+  * `sha256(string)` - Returns a SHA-256 hash representation of the
+    given string.
+    Example: `"${sha256(concat(aws_vpc.default.tags.customer, "-s3-bucket"))}"`
+
   * `cidrhost(iprange, hostnum)` - Takes an IP address range in CIDR notation
     and creates an IP address with the given host number. For example,
     ``cidrhost("10.0.0.0/8", 2)`` returns ``10.0.0.2``.