From f9d6f26f1a674366da3d1adfe414ed66480e710f Mon Sep 17 00:00:00 2001
From: Ryan Schumacher <jschumacher@virtru.com>
Date: Tue, 5 Nov 2024 12:24:32 -0600
Subject: [PATCH] fix(sdk): reset reader after checking if IsNanoTDF (#1718)

Closes #1717
---
 sdk/sdk.go      | 12 ++++++------
 sdk/sdk_test.go | 12 ++++++++++++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/sdk/sdk.go b/sdk/sdk.go
index b57591a5a..7704dcc5b 100644
--- a/sdk/sdk.go
+++ b/sdk/sdk.go
@@ -291,7 +291,8 @@ func (t TdfType) String() string {
 	return string(t)
 }
 
-// String method to make the custom type printable
+// GetTdfType returns the type of TDF based on the reader.
+// Reader is reset after the check.
 func GetTdfType(reader io.ReadSeeker) TdfType {
 	isValidNanoTdf, _ := IsValidNanoTdf(reader)
 
@@ -348,13 +349,12 @@ func IsValidTdf(reader io.ReadSeeker) (bool, error) {
 	return true, nil
 }
 
+// IsValidNanoTdf detects whether, or not the reader is a valid Nano TDF.
+// Reader is reset after the check.
 func IsValidNanoTdf(reader io.ReadSeeker) (bool, error) {
 	_, _, err := NewNanoTDFHeaderFromReader(reader)
-	if err != nil {
-		return false, err
-	}
-
-	return true, nil
+	_, _ = reader.Seek(0, io.SeekStart) // Ignore the error as we're just checking if it's a valid nano TDF
+	return err == nil, err
 }
 
 func fetchPlatformConfiguration(platformEndpoint string, dialOptions []grpc.DialOption) (PlatformConfiguration, error) {
diff --git a/sdk/sdk_test.go b/sdk/sdk_test.go
index 7b578dc7c..35d1c7831 100644
--- a/sdk/sdk_test.go
+++ b/sdk/sdk_test.go
@@ -145,6 +145,12 @@ func TestNew_ShouldValidateGoodNanoTdf(t *testing.T) {
 	require.NoError(t, err)
 
 	assert.True(t, isValid)
+
+	// Try again to see if the reader has been reset
+	isValid, err = sdk.IsValidNanoTdf(in)
+	require.NoError(t, err)
+
+	assert.True(t, isValid)
 }
 
 func TestNew_ShouldNotValidateBadNanoTdf(t *testing.T) {
@@ -169,6 +175,12 @@ func TestNew_ShouldValidateStandardTdf(t *testing.T) {
 	require.NoError(t, err)
 
 	assert.True(t, isValid)
+
+	// Try again to see if the reader has been reset
+	isValid, err = sdk.IsValidTdf(in)
+	require.NoError(t, err)
+
+	assert.True(t, isValid)
 }
 
 func TestNew_ShouldNotValidateBadStandardTdf(t *testing.T) {