From 2a02f6eb6ba545e35f4701b760a046d3e649675a Mon Sep 17 00:00:00 2001
From: sideshowbarker <mike@w3.org>
Date: Sun, 21 Jun 2026 16:45:32 +0900
Subject: [PATCH] =?UTF-8?q?LibWeb:=20Don=E2=80=99t=20crash=20on=20a=20deta?=
 =?UTF-8?q?ched=20publicExponent=20in=20generateKey?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Problem: Crash when generating an RSA key — or serializing one —
whose publicExponent is a typed array whose backing ArrayBuffer has
been detached; for example, by calling transfer() on it.

Cause: Two places with big_integer_from_api_big_integer() reading the
bytes of the backing ArrayBuffer directly. But reading the bytes of a
detached buffer aborts.

Fix: Read the bytes with WebIDL get_buffer_source_copy() — which yields
an empty copy for a detached, or OOB resizable, buffer. The empty array
is already mapped to zero — so generation rejects the zero exponent with
an error, rather than crashing.

Fixes https://github.com/LadybirdBrowser/ladybird/issues/9991
---
 Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp  |  3 +--
 Libraries/LibWeb/Crypto/CryptoKey.cpp         |  3 ++-
 ...o-generateKey-detached-public-exponent.txt |  1 +
 ...ructuredClone-detached-public-exponent.txt |  1 +
 ...-generateKey-detached-public-exponent.html | 25 +++++++++++++++++++
 ...ucturedClone-detached-public-exponent.html | 22 ++++++++++++++++
 6 files changed, 52 insertions(+), 3 deletions(-)
 create mode 100644 Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-generateKey-detached-public-exponent.txt
 create mode 100644 Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-structuredClone-detached-public-exponent.txt
 create mode 100644 Tests/LibWeb/Text/input/Crypto/SubtleCrypto-generateKey-detached-public-exponent.html
 create mode 100644 Tests/LibWeb/Text/input/Crypto/SubtleCrypto-structuredClone-detached-public-exponent.html

diff --git a/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp b/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
index 000c148200486..1459e94445ad9 100644
--- a/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
+++ b/Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp
@@ -91,8 +91,7 @@ static ::Crypto::UnsignedBigInteger big_integer_from_api_big_integer(GC::Ptr<JS:
     // (that is, at most 7 leading zero bits, except the value 0 which shall have length 8 bits).
     // The API SHALL accept values with any number of leading zero bits, including the empty array, which represents zero.
 
-    auto buffer = big_integer->viewed_array_buffer()->bytes();
-
+    auto buffer = MUST(WebIDL::get_buffer_source_copy(*big_integer));
     if (!buffer.is_empty())
         return ::Crypto::UnsignedBigInteger::import_data(buffer);
     return ::Crypto::UnsignedBigInteger(0);
diff --git a/Libraries/LibWeb/Crypto/CryptoKey.cpp b/Libraries/LibWeb/Crypto/CryptoKey.cpp
index 3dc3905a65b1e..a8e5ff8d8e438 100644
--- a/Libraries/LibWeb/Crypto/CryptoKey.cpp
+++ b/Libraries/LibWeb/Crypto/CryptoKey.cpp
@@ -14,6 +14,7 @@
 #include <LibWeb/Crypto/CryptoKey.h>
 #include <LibWeb/Crypto/KeyAlgorithms.h>
 #include <LibWeb/HTML/StructuredSerialize.h>
+#include <LibWeb/WebIDL/AbstractOperations.h>
 
 namespace Web::Crypto {
 
@@ -44,7 +45,7 @@ enum class KeyAlgorithmTag : u8 {
 
 ::Crypto::UnsignedBigInteger big_integer_from_api_big_integer(JS::Uint8Array const& big_integer)
 {
-    auto buffer = big_integer.viewed_array_buffer()->bytes().slice(big_integer.byte_offset(), big_integer.byte_length().length());
+    auto buffer = MUST(WebIDL::get_buffer_source_copy(big_integer));
     if (!buffer.is_empty())
         return ::Crypto::UnsignedBigInteger::import_data(buffer);
     return ::Crypto::UnsignedBigInteger(0);
diff --git a/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-generateKey-detached-public-exponent.txt b/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-generateKey-detached-public-exponent.txt
new file mode 100644
index 0000000000000..563bb83b204b3
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-generateKey-detached-public-exponent.txt
@@ -0,0 +1 @@
+rejected: OperationError
diff --git a/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-structuredClone-detached-public-exponent.txt b/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-structuredClone-detached-public-exponent.txt
new file mode 100644
index 0000000000000..96ad8180ac729
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/Crypto/SubtleCrypto-structuredClone-detached-public-exponent.txt
@@ -0,0 +1 @@
+PASS (didn't crash): cloned
diff --git a/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-generateKey-detached-public-exponent.html b/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-generateKey-detached-public-exponent.html
new file mode 100644
index 0000000000000..b9112b249956c
--- /dev/null
+++ b/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-generateKey-detached-public-exponent.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<script src="../include.js"></script>
+<script>
+    asyncTest(async done => {
+        const exponentBuffer = new ArrayBuffer(3);
+        const publicExponent = new Uint8Array(exponentBuffer);
+        publicExponent.set([0x01, 0x00, 0x01]);
+
+        // transfer() detaches exponentBuffer, so publicExponent views a detached buffer (byteLength 0).
+        exponentBuffer.transfer();
+
+        try {
+            await crypto.subtle.generateKey({
+                name: "RSASSA-PKCS1-v1_5",
+                modulusLength: 1024,
+                publicExponent,
+                hash: "SHA-256",
+            }, true, ["sign", "verify"]);
+            println("resolved");
+        } catch (e) {
+            println("rejected: " + e.name);
+        }
+        done();
+    });
+</script>
diff --git a/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-structuredClone-detached-public-exponent.html b/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-structuredClone-detached-public-exponent.html
new file mode 100644
index 0000000000000..25878b9f93013
--- /dev/null
+++ b/Tests/LibWeb/Text/input/Crypto/SubtleCrypto-structuredClone-detached-public-exponent.html
@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<script src="../include.js"></script>
+<script>
+    asyncTest(async done => {
+        const keyPair = await crypto.subtle.generateKey({
+            name: "RSASSA-PKCS1-v1_5",
+            modulusLength: 1024,
+            publicExponent: new Uint8Array([0x01, 0x00, 0x01]),
+            hash: "SHA-256",
+        }, true, ["sign", "verify"]);
+
+        // Detach the buffer backing the stored publicExponent, then serialize the key by cloning it.
+        keyPair.publicKey.algorithm.publicExponent.buffer.transfer();
+        try {
+            structuredClone(keyPair.publicKey);
+            println("PASS (didn't crash): cloned");
+        } catch (e) {
+            println("PASS (didn't crash): " + e.name);
+        }
+        done();
+    });
+</script>