AK: Add roundtrip fuzzer for Base64

Meta/Lagom/Fuzzers/FuzzBase64Roundtrip.cpp

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2023, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Base64.h>
+#include <stdio.h>
+
+extern "C" int LLVMFuzzerTestOneInput(uint8_t const* data, size_t size)
+{
+    AK::set_debug_enabled(false);
+    auto input = ReadonlyBytes { data, size };
+
+    auto encoded = MUST(encode_base64(input));
+    auto decoded = MUST(decode_base64(encoded));
+
+    VERIFY(decoded == input);
+
+    return 0;
+}

Meta/Lagom/Fuzzers/fuzzers.cmake

@@ -1,5 +1,6 @@
 set(FUZZER_TARGETS
     ASN1
+    Base64Roundtrip
     BLAKE2b
     BMPLoader
     Brotli

Userland/Utilities/test-fuzz.cpp

@@ -13,6 +13,7 @@
 // TODO: Look into generating this from the authoritative list of fuzzing targets in fuzzer.cmake.
 #define ENUMERATE_TARGETS(T) \
     T(ASN1)                  \
+    T(Base64Roundtrip)       \
     T(BLAKE2b)               \
     T(BMPLoader)             \
     T(Brotli)                \