fix: update GetType to check the first 4 bytes (#1736)

### Proposed Changes

This pull request updates the GetType to only check max first 4 bytes of
the reader to see if we a nanotdf or zip(tdf).

### Checklist

- [ ] I have added or updated unit tests
- [ ] I have added or updated integration tests (if appropriate)
- [ ] I have added or updated documentation

### Testing Instructions

Author: strantalis

sdk/sdk.go

@@ -1,6 +1,7 @@
 package sdk
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
 	_ "embed"
@@ -291,21 +292,43 @@ func (t TdfType) String() string {
 	return string(t)
 }
 
+var (
+	// ZIP file Signature
+	zipSignature = []byte{0x50, 0x4B, 0x03, 0x04}
+	// Nano TDF Signature
+	nanoSignature = []byte{0x4C, 0x31, 0x4C}
+)
+
 // 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)
+	numBytes := 4
+	buffer := make([]byte, numBytes)
+	n, err := reader.Read(buffer)
+	if err != nil {
+		return Invalid
+	}
 
-	if isValidNanoTdf {
-		return Nano
+	// Reset the reader to its original position
+	_, err = reader.Seek(0, io.SeekStart)
+	if err != nil {
+		return Invalid
 	}
 
-	isValidStandardTdf, _ := IsValidTdf(reader)
+	if n < numBytes {
+		return Invalid
+	}
 
-	if isValidStandardTdf {
+	// Check if the first 4 bytes match the ZIP signature
+	if bytes.Equal(buffer, zipSignature) {
 		return Standard
 	}
 
+	// Check if the first 3 bytes match the Nano signature
+	if bytes.Equal(buffer[:3], nanoSignature) {
+		return Nano
+	}
+
 	return Invalid
 }
 

sdk/sdk_test.go

@@ -330,3 +330,43 @@ func Test_ShouldSanitizePlatformEndpoint(t *testing.T) {
 		})
 	}
 }
+
+func Test_GetType_NanoTDF(t *testing.T) {
+	nano := "TDFMABJsb2NhbGhvc3Q6ODA4MC9rYXOAAQIA2qvjMRfg7b27lT2kf9SwHRkDIg8ZXtfRoiIvdMUHq/gL5AUMfmv4Di8sKCyLkmUm/WITVj5hDeV/z4JmQ0JL7ZxqSmgZoK6TAHvkKhUly4zMEWMRXH8IktKhFKy1+fD+3qwDopqWAO5Nm2nYQqi75atEFckstulpNKg3N+Ul22OHr/ZuR127oPObBDYNRfktBdzoZbEQcPlr8q1B57q6y5SPZFjEzL9weK+uS5bUJWkF3nsHASo2bZw7IPhTZxoFVmCDjwvj6MbxNa7zG6aClHJ162zKxLLnD9TtIHuZ59R7LgiSieipXeExj+ky9OgIw5DfwyUuxsQLtKpMIAFPmLY9Hy2naUJxke0MT1EUBgastCq+YtFGslV9LJo/A8FtrRqludwtM0O+Z9FlAkZ1oNL7M7uOkLrh7eRrv+C1AAAX6FaBQoOtqnmyu6Jp+VzkxDddEeLRUyI="
+	nanoDecoded, err := base64.StdEncoding.DecodeString(nano)
+	require.NoError(t, err)
+
+	in := bytes.NewReader(nanoDecoded)
+	tdfType := sdk.GetTdfType(in)
+
+	assert.Equal(t, sdk.Nano, tdfType)
+}
+
+func Test_GetType_TDF(t *testing.T) {
+	tdf := "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"
+	tdfDecoded, err := base64.StdEncoding.DecodeString(tdf)
+	require.NoError(t, err)
+
+	in := bytes.NewReader(tdfDecoded)
+	tdfType := sdk.GetTdfType(in)
+
+	assert.Equal(t, sdk.Standard, tdfType)
+}
+
+func Test_GetType_InvalidTDF(t *testing.T) {
+	tdf := ""
+	in := bytes.NewReader([]byte(tdf))
+
+	tdfType := sdk.GetTdfType(in)
+
+	assert.Equal(t, sdk.Invalid, tdfType)
+}
+
+func Test_GetType_Invalid2Bytes(t *testing.T) {
+	tdf := "UE"
+	in := bytes.NewReader([]byte(tdf))
+
+	tdfType := sdk.GetTdfType(in)
+
+	assert.Equal(t, sdk.Invalid, tdfType)
+}