From 35076fdc4ecdfdac27d6e48c0c563716507fb6b9 Mon Sep 17 00:00:00 2001
From: Rose Hogenson <rosehogenson@posteo.net>
Date: Mon, 26 Jan 2026 07:09:07 -0800
Subject: Make sure to reject a 32 byte message

---
 oae2.go      |  9 ++++++++-
 oae2_test.go | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/oae2.go b/oae2.go
index e2bb1c1..ff59b76 100644
--- a/oae2.go
+++ b/oae2.go
@@ -306,7 +306,14 @@ func (r *Reader) initialize() error {
 	}
 	// Decrypt the first segment now to make sure we validate the
 	// additional data
-	return r.fillBuf()
+	if err := r.fillBuf(); err != nil {
+		if err == io.EOF {
+			r.err = io.ErrUnexpectedEOF
+			return r.err
+		}
+		return err
+	}
+	return nil
 }
 
 func (r *Reader) init() error {
diff --git a/oae2_test.go b/oae2_test.go
index 4099aa7..f0ed37f 100644
--- a/oae2_test.go
+++ b/oae2_test.go
@@ -2,6 +2,7 @@ package oae2
 
 import (
 	"bytes"
+	"crypto/rand"
 	"io"
 	"strings"
 	"testing"
@@ -57,6 +58,19 @@ func TestReadFromWriteTo(t *testing.T) {
 	}
 }
 
+func TestInvalid(t *testing.T) {
+	t.Parallel()
+
+	const (
+		msg = "01234567890123456789012345678901"
+		key = "asdf"
+	)
+	_, err := io.ReadAll(NewReader(strings.NewReader(msg), []byte(key), 1, nil))
+	if err == nil {
+		t.Errorf("Message %q passed validation, want error", msg)
+	}
+}
+
 func TestReader_Seek(t *testing.T) {
 	t.Parallel()
 	const (
@@ -196,6 +210,37 @@ func FuzzReadFromWriteTo(f *testing.F) {
 	})
 }
 
+func FuzzReadInvalid(f *testing.F) {
+	f.Add(1, "", "")
+	f.Add(1, "01234567890123456789012345678901", "")
+	f.Fuzz(func(t *testing.T, segmentSize int, msg string, additionalData string) {
+		if segmentSize <= 0 {
+			return
+		}
+		password := make([]byte, 32)
+		// Get a random password so that we can be sure msg is invalid
+		rand.Read(password)
+		if _, err := io.ReadAll(NewReader(strings.NewReader(msg), password, segmentSize, []byte(additionalData))); err == nil {
+			t.Errorf("Reader.Read: message passed validation")
+		}
+	})
+}
+
+func FuzzWriteToInvalid(f *testing.F) {
+	f.Add(1, "", "")
+	f.Add(1, "01234567890123456789012345678901", "")
+	f.Fuzz(func(t *testing.T, segmentSize int, msg string, additionalData string) {
+		if segmentSize <= 0 {
+			return
+		}
+		password := make([]byte, 32)
+		rand.Read(password)
+		if _, err := NewReader(strings.NewReader(msg), password, segmentSize, []byte(additionalData)).WriteTo(io.Discard); err == nil {
+			t.Errorf("Reader.WriteTo: message passed validation")
+		}
+	})
+}
+
 func FuzzSeekStart(f *testing.F) {
 	f.Add(1, []byte("Hello World!"), 6)
 	f.Add(30, []byte("000000"), 6)
-- 
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