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garydgregory pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-lang.git
The following commit(s) were added to refs/heads/master by this push:
new ef39bc927 StrBuilder.replaceImpl shrink-branch leaves residual chars
in buffer (#1672)
ef39bc927 is described below
commit ef39bc92712d47c100af3b243a8bfcd84a45f116
Author: Gary Gregory <[email protected]>
AuthorDate: Sun May 24 13:14:58 2026 -0400
StrBuilder.replaceImpl shrink-branch leaves residual chars in buffer (#1672)
tail
---
.../org/apache/commons/lang3/text/StrBuilder.java | 3 ++
.../commons/lang3/text/StrBuilderClearTest.java | 62 +++++++++++++++-------
2 files changed, 45 insertions(+), 20 deletions(-)
diff --git a/src/main/java/org/apache/commons/lang3/text/StrBuilder.java
b/src/main/java/org/apache/commons/lang3/text/StrBuilder.java
index aa98cd992..39277460c 100644
--- a/src/main/java/org/apache/commons/lang3/text/StrBuilder.java
+++ b/src/main/java/org/apache/commons/lang3/text/StrBuilder.java
@@ -2705,6 +2705,9 @@ private void replaceImpl(final int startIndex, final int
endIndex, final int rem
if (insertLen != removeLen) {
ensureCapacity(newSize);
System.arraycopy(buffer, endIndex, buffer, startIndex + insertLen,
size - endIndex);
+ if (size > newSize) {
+ ArrayFill.clear(buffer, newSize, size);
+ }
size = newSize;
}
if (insertLen > 0) {
diff --git
a/src/test/java/org/apache/commons/lang3/text/StrBuilderClearTest.java
b/src/test/java/org/apache/commons/lang3/text/StrBuilderClearTest.java
index e499a1d20..328d4c92a 100644
--- a/src/test/java/org/apache/commons/lang3/text/StrBuilderClearTest.java
+++ b/src/test/java/org/apache/commons/lang3/text/StrBuilderClearTest.java
@@ -143,28 +143,30 @@ public void
testReadFromReaderDoesNotExposeStaleInternalBuffer() throws IOExcept
}
@Test
- public void testStaleCharsNotLeakedAfterClear() throws Exception {
- final StrBuilder sb = new StrBuilder("secret_password_xyzzy_leak");
- // clear() resets logical size to 0 but leaves chars in buffer
- sb.clear();
- // append something shorter than the original
- sb.append("ok");
- // Stale content is serialized as UTF-16BE char[] data.
- // "xyzzy_leak" was at positions 15+, well beyond "ok" (len=2), so
must not appear.
- assertFalse(containsUtf16Be(SerializationUtils.serialize(sb),
"xyzzy_leak"));
- }
-
- @Test
- public void testStaleCharsNotLeakedAfterTruncate() throws Exception {
- final StrBuilder sb = new StrBuilder("top_secret_key_material");
- // truncate to a short length – tail remains in buffer
- sb.delete(6, sb.length());
- // sb now logically contains "top_se"
- assertFalse(containsUtf16Be(SerializationUtils.serialize(sb),
"secret_key_material"));
+ void testReplaceImplLeavesResidue() throws Exception {
+ final String string = "SECRET_PASSWORD_DATA";
+ final StrBuilder sb = new StrBuilder(string);
+ assertEquals(20, sb.length());
+ // Shrink: replace [0,20) with "X" => removeLen=20, insertLen=1,
newSize=1.
+ sb.replace(0, 20, "X");
+ assertEquals(1, sb.length());
+ assertEquals("X", sb.toString());
+ final char[] buf = sb.getBuffer();
+ assertTrue(buf.length >= 20);
+ // Tail [1..20) should be cleared but isn't on baseline => residue
persists.
+ // Probe offset 5: original was '_' (underscore from "SECRET_...").
After
+ // arraycopy(buf, endIndex=20, buf, startIndex+insertLen=1,
size-endIndex=0)
+ // the shift is a no-op, so buf[5] retains the original 'T' from
"SECRET_".
+ // Either way it is non-NUL.
+ assertEquals(CharUtils.NUL, buf[5]);
+ // Dump the visible residue at the logical-unused tail.
+ for (int i = 1; i < 20; i++) {
+ assertEquals(CharUtils.NUL, buf[i]);
+ }
}
@Test
- void testSetLengthShrinkLeavesResidual() throws Exception {
+ void testSetLengthShrinkLeavesResidue() throws Exception {
final String string = "CONFIDENTIAL_TOKEN_VALUE";
final int len = string.length();
final StrBuilder sb = new StrBuilder(string);
@@ -177,9 +179,29 @@ void testSetLengthShrinkLeavesResidual() throws Exception {
assertTrue(buf.length >= len);
// Probe offset 10: original was 'L' (CONFIDENTIA*L*_TOKEN_VALUE).
assertEquals(CharUtils.NUL, buf[10]);
- final StringBuilder dump = new StringBuilder();
for (int i = 5; i < len; i++) {
assertEquals(CharUtils.NUL, buf[i]);
}
}
+
+ @Test
+ public void testStaleCharsNotLeakedAfterClear() throws Exception {
+ final StrBuilder sb = new StrBuilder("secret_password_xyzzy_leak");
+ // clear() resets logical size to 0 but leaves chars in buffer
+ sb.clear();
+ // append something shorter than the original
+ sb.append("ok");
+ // Stale content is serialized as UTF-16BE char[] data.
+ // "xyzzy_leak" was at positions 15+, well beyond "ok" (len=2), so
must not appear.
+ assertFalse(containsUtf16Be(SerializationUtils.serialize(sb),
"xyzzy_leak"));
+ }
+
+ @Test
+ public void testStaleCharsNotLeakedAfterTruncate() throws Exception {
+ final StrBuilder sb = new StrBuilder("top_secret_key_material");
+ // truncate to a short length – tail remains in buffer
+ sb.delete(6, sb.length());
+ // sb now logically contains "top_se"
+ assertFalse(containsUtf16Be(SerializationUtils.serialize(sb),
"secret_key_material"));
+ }
}
