add test function for ParseRSAPrivateKey

in_toto/keylib.go

@@ -57,7 +57,7 @@ func ParseRSAPrivateKeyFromPEM(pemBytes []byte) (*rsa.PrivateKey, error) {
 	// Should we handle it / fail / say something about it?
 	data, _ := pem.Decode(pemBytes)
 	if data == nil {
-		return nil, fmt.Errorf("Could not find a Private key PEM block")
+		return nil, fmt.Errorf("Could not find a private key PEM block")
 	}
 
 	priv, err := x509.ParsePKCS1PrivateKey(data.Bytes)

in_toto/keylib_test.go

@@ -57,6 +57,32 @@ yMxdI/24LUOOQ71cHW3ITIDImm6I8KmrXFM2NewTARKfAgMBAAE=
 	}
 }
 
+func TestParseRSAPrivateKeyFromPEM(t *testing.T) {
+	// Test parsing errors:
+	// - Missing pem headers,
+	// - Missing pem body
+	// We only support RSA private keys, therefore we don't need to check for other keys.
+	// Other keys should fail at ParsePKCS1 stage already.
+	invalidRSA := []string{
+		"not a PEM block",
+		`-----BEGIN PRIVATE KEY-----
+
+-----END PRIVATE KEY-----`,
+	}
+	expectedErrors := []string{
+		"Could not find a private key PEM block",
+		"truncated",
+	}
+
+	for i := 0; i < len(invalidRSA); i++ {
+		result, err := ParseRSAPrivateKeyFromPEM([]byte(invalidRSA[i]))
+		if err == nil || !strings.Contains(err.Error(), expectedErrors[i]) {
+			t.Errorf("ParseRSAPrivateKeyFromPEM returned (%p, %s), expected '%s'"+
+				" error", result, err, expectedErrors[i])
+		}
+	}
+}
+
 func TestLoadRSAPublicKey(t *testing.T) {
 	// Test loading valid public rsa key from pem-formatted file
 	var key Key