Skip to content

[Unsafe] Guard JNI string lengths #13043

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
simonrozsival merged 2 commits into from
Oct 9, 2026
Merged

[Unsafe] Guard JNI string lengths #13043

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
29eeb65
[Mono.Android] Guard JNI string lengths
simonrozsival Oct 8, 2026
d897f22
Add check for zero length in JNIEnv.cs
simonrozsival Oct 9, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 10 additions & 3 deletions src/Mono.Android/Android.Runtime/JNIEnv.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -484,13 +484,20 @@ public static unsafe IntPtr NewString (string? text)
return JniEnvironment.Strings.NewString (text).Handle;
}

public static unsafe IntPtr NewString (char[]? text, int length)
public static IntPtr NewString (char[]? text, int length)
{
if (text == null)
return IntPtr.Zero;

fixed (char *s = text)
return JniEnvironment.Strings.NewString (s, length).Handle;
if (length < 0 || length > text.Length)
throw new ArgumentOutOfRangeException (nameof (length));
Comment thread
Copilot marked this conversation as resolved.
if (length == 0)
return JniEnvironment.Strings.NewString ("").Handle;

unsafe {
fixed (char *s = text)
return JniEnvironment.Strings.NewString (s, length).Handle;
}
}

static void AssertCompatibleArrayTypes (Type srcElementType, IntPtr destArray)
Expand Down
14 changes: 14 additions & 0 deletions tests/Mono.Android-Tests/Mono.Android-Tests/Java.Interop/JnienvTest.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,20 @@ namespace Java.InteropTests
[TestFixture]
public class JnienvTest
{
[Test]
[Category ("JniStringLength")]
public void NewStringValidatesLengthAndSupportsPrefix ()
{
var text = new[] { 'f', 'o', 'o' };

Assert.Throws<ArgumentOutOfRangeException> (() => JNIEnv.NewString (text, -1));
Assert.Throws<ArgumentOutOfRangeException> (() => JNIEnv.NewString (text, text.Length + 1));
Assert.AreEqual (IntPtr.Zero, JNIEnv.NewString ((char[]?) null, -1));

IntPtr handle = JNIEnv.NewString (text, 2);
Assert.AreEqual ("fo", JNIEnv.GetString (handle, JniHandleOwnership.TransferLocalRef));
}

[Test]
public void TestMyPaintColor ()
{
Expand Down
Loading