From 688b913218ec1de2a0ac286803e4d17ddd19ae37 Mon Sep 17 00:00:00 2001
From: arimu1 <19286898+arimu1@users.noreply.github.com>
Date: Sun, 13 Sep 2026 06:10:15 +0700
Subject: [PATCH] fix(streamingaead): return -1 at EOF on empty seekable
 plaintext

When plaintext size is zero, read() never decrypted the last segment so
reachedEnd() stayed false and callers spun on 0 forever. Decrypt the final
segment when at end-of-plaintext with no bytes transferred.

Fixes #79
---
 .../subtle/StreamingAeadSeekableDecryptingChannel.java     | 3 +++
 .../streamingaead/AesCtrHmacStreamingKeyManagerTest.java   | 7 +------
 .../streamingaead/AesGcmHkdfStreamingKeyManagerTest.java   | 7 +------
 3 files changed, 5 insertions(+), 12 deletions(-)

diff --git a/src/main/java/com/google/crypto/tink/subtle/StreamingAeadSeekableDecryptingChannel.java b/src/main/java/com/google/crypto/tink/subtle/StreamingAeadSeekableDecryptingChannel.java
index 32371bebf..a38520833 100644
--- a/src/main/java/com/google/crypto/tink/subtle/StreamingAeadSeekableDecryptingChannel.java
+++ b/src/main/java/com/google/crypto/tink/subtle/StreamingAeadSeekableDecryptingChannel.java
@@ -342,6 +342,9 @@ public synchronized int read(ByteBuffer dst) throws IOException {
       }
     }
     int read = dst.position() - startPos;
+    if (read == 0 && !reachedEnd() && plaintextPosition >= plaintextSize) {
+      tryLoadSegment(numberOfSegments - 1);
+    }
     if (read == 0 && reachedEnd()) {
       return -1;
     }
diff --git a/src/test/java/com/google/crypto/tink/streamingaead/AesCtrHmacStreamingKeyManagerTest.java b/src/test/java/com/google/crypto/tink/streamingaead/AesCtrHmacStreamingKeyManagerTest.java
index b3766ec68..0e5bb44cc 100644
--- a/src/test/java/com/google/crypto/tink/streamingaead/AesCtrHmacStreamingKeyManagerTest.java
+++ b/src/test/java/com/google/crypto/tink/streamingaead/AesCtrHmacStreamingKeyManagerTest.java
@@ -312,11 +312,6 @@ public void decryptSeekableByteChannel_works(
         .isEqualTo(Arrays.copyOfRange(v.getPlaintext(), start, start + len));
     // There must be no more data available.
     ByteBuffer endOfStreamChecker = ByteBuffer.allocate(1);
-    if (v.getPlaintext().length != 0) {
-      assertThat(plaintextChannel.read(endOfStreamChecker)).isEqualTo(-1);
-    } else {
-      // TODO: b/390077226 - This should return -1.
-      assertThat(plaintextChannel.read(endOfStreamChecker)).isEqualTo(0);
-    }
+    assertThat(plaintextChannel.read(endOfStreamChecker)).isEqualTo(-1);
   }
 }
diff --git a/src/test/java/com/google/crypto/tink/streamingaead/AesGcmHkdfStreamingKeyManagerTest.java b/src/test/java/com/google/crypto/tink/streamingaead/AesGcmHkdfStreamingKeyManagerTest.java
index 5da4b0723..f2f159a0d 100644
--- a/src/test/java/com/google/crypto/tink/streamingaead/AesGcmHkdfStreamingKeyManagerTest.java
+++ b/src/test/java/com/google/crypto/tink/streamingaead/AesGcmHkdfStreamingKeyManagerTest.java
@@ -406,11 +406,6 @@ public void decryptSeekableByteChannel_works(
         .isEqualTo(Arrays.copyOfRange(v.getPlaintext(), start, start + len));
     // There must be no more data available.
     ByteBuffer endOfStreamChecker = ByteBuffer.allocate(1);
-    if (v.getPlaintext().length != 0) {
-      assertThat(plaintextChannel.read(endOfStreamChecker)).isEqualTo(-1);
-    } else {
-      // TODO: b/390077226 - This should return -1.
-      assertThat(plaintextChannel.read(endOfStreamChecker)).isEqualTo(0);
-    }
+    assertThat(plaintextChannel.read(endOfStreamChecker)).isEqualTo(-1);
   }
 }