New RSA encrypt/decrypt functions, and new base64.DecodeBytes function

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

conv/conv.go

@@ -132,6 +132,9 @@ func ToString(in interface{}) string {
 	if s, ok := in.(fmt.Stringer); ok {
 		return s.String()
 	}
+	if s, ok := in.([]byte); ok {
+		return string(s)
+	}
 
 	v, ok := printableValue(reflect.ValueOf(in))
 	if ok {

conv/conv_test.go

@@ -245,6 +245,7 @@ func TestToString(t *testing.T) {
 		{p, "foo"},
 		{fmt.Errorf("hi"), "hi"},
 		{n, "<nil>"},
+		{[]byte("hello world"), "hello world"},
 	}
 
 	for _, d := range testdata {

crypto/rsa.go

@@ -0,0 +1,104 @@
+package crypto
+
+import (
+	"bytes"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"strings"
+)
+
+// RSAEncrypt - use the given public key to encrypt the given plaintext. The key
+// should be a PEM-encoded RSA public key in PKIX, ASN.1 DER form, typically
+// beginning with "PUBLIC KEY". PKCS#1 format is also supported as a fallback.
+// The output will not be encoded, so consider base64-encoding it for display.
+func RSAEncrypt(key string, in []byte) ([]byte, error) {
+	block, _ := pem.Decode([]byte(key))
+	if block == nil {
+		return nil, fmt.Errorf("failed to read key %q: no key found", key)
+	}
+
+	pub, err := x509.ParsePKIXPublicKey(block.Bytes)
+	if err != nil {
+		if strings.Contains(err.Error(), "use ParsePKCS1PublicKey instead") {
+			pub, err = x509.ParsePKCS1PublicKey(block.Bytes)
+		}
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse public key: %w", err)
+		}
+	}
+	pubKey, ok := pub.(*rsa.PublicKey)
+	if !ok {
+		return nil, fmt.Errorf("public key in wrong format, was %T", pub)
+	}
+
+	out, err := rsa.EncryptPKCS1v15(rand.Reader, pubKey, in)
+	return out, err
+}
+
+// RSADecrypt - decrypt the ciphertext with the given private key. The key
+// must be a PEM-encoded RSA private key in PKCS#1, ASN.1 DER form, typically
+// beginning with "RSA PRIVATE KEY". The input text must be plain ciphertext,
+// not base64-encoded.
+func RSADecrypt(key string, in []byte) ([]byte, error) {
+	block, _ := pem.Decode([]byte(key))
+	if block == nil {
+		return nil, fmt.Errorf("failed to read key %q: no key found", key)
+	}
+
+	priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("invalid private key: %w", err)
+	}
+
+	out, err := priv.Decrypt(nil, in, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decrypt: %w", err)
+	}
+	return out, nil
+}
+
+// RSAGenerateKey -
+func RSAGenerateKey(bits int) ([]byte, error) {
+	priv, err := rsa.GenerateKey(rand.Reader, bits)
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate RSA private key: %w", err)
+	}
+	block := &pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(priv),
+	}
+	buf := &bytes.Buffer{}
+	err = pem.Encode(buf, block)
+	if err != nil {
+		return nil, fmt.Errorf("failed to encode generated RSA private key: pem encoding failed: %w", err)
+	}
+	return buf.Bytes(), nil
+}
+
+// RSADerivePublicKey -
+func RSADerivePublicKey(privateKey []byte) ([]byte, error) {
+	block, _ := pem.Decode(privateKey)
+	if block == nil {
+		return nil, fmt.Errorf("failed to read key: no key found")
+	}
+
+	priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("invalid private key: %w", err)
+	}
+
+	b, err := x509.MarshalPKIXPublicKey(&priv.PublicKey)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal PKIX public key: %w", err)
+	}
+
+	block = &pem.Block{
+		Type:  "PUBLIC KEY",
+		Bytes: b,
+	}
+
+	return pem.EncodeToMemory(block), nil
+}

crypto/rsa_test.go

@@ -0,0 +1,109 @@
+package crypto
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func genPKCS1PrivKey() (*rsa.PrivateKey, string) {
+	rsaPriv, _ := rsa.GenerateKey(rand.Reader, 4096)
+	privBlock := &pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(rsaPriv),
+	}
+	return rsaPriv, string(pem.EncodeToMemory(privBlock))
+}
+
+func derivePKIXPrivKey(priv *rsa.PrivateKey) string {
+	privBlock := &pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(priv),
+	}
+	return string(pem.EncodeToMemory(privBlock))
+}
+
+func derivePKIXPubKey(priv *rsa.PrivateKey) string {
+	b, _ := x509.MarshalPKIXPublicKey(&priv.PublicKey)
+	pubBlock := &pem.Block{
+		Type:  "PUBLIC KEY",
+		Bytes: b,
+	}
+	testPubKey := string(pem.EncodeToMemory(pubBlock))
+	return testPubKey
+}
+
+func derivePKCS1PubKey(priv *rsa.PrivateKey) string {
+	b := x509.MarshalPKCS1PublicKey(&priv.PublicKey)
+	pubBlock := &pem.Block{
+		Type:  "RSA PUBLIC KEY",
+		Bytes: b,
+	}
+	testPubKey := string(pem.EncodeToMemory(pubBlock))
+	return testPubKey
+}
+
+func TestRSACrypt(t *testing.T) {
+	priv, testPrivKey := genPKCS1PrivKey()
+	testPubKey := derivePKIXPubKey(priv)
+
+	in := []byte("hello world")
+	key := "bad key"
+	_, err := RSAEncrypt(key, in)
+	assert.Error(t, err)
+
+	_, err = RSADecrypt(key, in)
+	assert.Error(t, err)
+
+	key = ""
+	_, err = RSAEncrypt(key, in)
+	assert.Error(t, err)
+	_, err = RSADecrypt(key, in)
+	assert.Error(t, err)
+
+	enc, err := RSAEncrypt(testPubKey, in)
+	assert.NoError(t, err)
+	dec, err := RSADecrypt(testPrivKey, enc)
+	assert.NoError(t, err)
+	assert.Equal(t, in, dec)
+
+	testPubKey = derivePKCS1PubKey(priv)
+	enc, err = RSAEncrypt(testPubKey, in)
+	assert.NoError(t, err)
+	dec, err = RSADecrypt(testPrivKey, enc)
+	assert.NoError(t, err)
+	assert.Equal(t, in, dec)
+}
+
+func TestRSAGenerateKey(t *testing.T) {
+	_, err := RSAGenerateKey(0)
+	assert.Error(t, err)
+
+	key, err := RSAGenerateKey(12)
+	assert.NoError(t, err)
+	assert.True(t, strings.HasPrefix(string(key),
+		"-----BEGIN RSA PRIVATE KEY-----"))
+	assert.True(t, strings.HasSuffix(string(key),
+		"-----END RSA PRIVATE KEY-----\n"))
+}
+
+func TestRSADerivePublicKey(t *testing.T) {
+	_, err := RSADerivePublicKey(nil)
+	assert.Error(t, err)
+
+	_, err = RSADerivePublicKey([]byte(`-----BEGIN FOO-----
+-----END FOO-----`))
+	assert.Error(t, err)
+
+	priv, privKey := genPKCS1PrivKey()
+	expected := derivePKIXPubKey(priv)
+
+	actual, err := RSADerivePublicKey([]byte(privKey))
+	assert.NoError(t, err)
+	assert.Equal(t, expected, string(actual))
+}

docs-src/content/functions/base64.yml

@@ -4,7 +4,7 @@ funcs:
   - name: base64.Encode
     description: |
       Encode data as a Base64 string. Specifically, this uses the standard Base64 encoding as defined in [RFC4648 §4](https://tools.ietf.org/html/rfc4648#section-4) (and _not_ the URL-safe encoding).
-    pipeline: false
+    pipeline: true
     arguments:
       - name: input
         required: true
@@ -20,8 +20,10 @@ funcs:
     description: |
       Decode a Base64 string. This supports both standard ([RFC4648 §4](https://tools.ietf.org/html/rfc4648#section-4)) and URL-safe ([RFC4648 §5](https://tools.ietf.org/html/rfc4648#section-5)) encodings.
 
-      This implementation outputs the data as a string, so it may not be appropriate for decoding binary data. If this functionality is desired, [file an issue](https://github.com/hairyhenderson/gomplate/issues/new).
-    pipeline: false
+      This function outputs the data as a string, so it may not be appropriate
+      for decoding binary data. Use [`base64.DecodeBytes`](#base64.DecodeBytes)
+      for binary data.
+    pipeline: true
     arguments:
       - name: input
         required: true
@@ -33,3 +35,22 @@ funcs:
       - |
         $ gomplate -i '{{ "aGVsbG8gd29ybGQ=" | base64.Decode }}'
         hello world
+  - name: base64.DecodeBytes
+    description: |
+      Decode a Base64 string. This supports both standard ([RFC4648 §4](https://tools.ietf.org/html/rfc4648#section-4)) and URL-safe ([RFC4648 §5](https://tools.ietf.org/html/rfc4648#section-5)) encodings.
+
+      This function outputs the data as a byte array, so it's most useful for
+      outputting binary data that will be processed further.
+      Use [`base64.Decode`](#base64.Decode) to output a plain string.
+    pipeline: false
+    arguments:
+      - name: input
+        required: true
+        description: The base64 string to decode
+    examples:
+      - |
+        $ gomplate -i '{{ base64.DecodeBytes "aGVsbG8gd29ybGQ=" }}'
+        [104 101 108 108 111 32 119 111 114 108 100]
+      - |
+        $ gomplate -i '{{ "aGVsbG8gd29ybGQ=" | base64.DecodeBytes | conv.ToString }}'
+        hello world