LibAudio: Handle stream errors in FlacLoader

The FlacLoader already has numerous checks for invalid data reads and
for invalid stream states, but it never actually handles the stream
errors on the stream object. By handling them properly we can actually
run FuzzFlacLoader for longer than a few seconds before it hits the
first assertion :^).

Userland/Libraries/LibAudio/FlacLoader.cpp

@@ -11,6 +11,7 @@
 #include <AK/FlyString.h>
 #include <AK/Format.h>
 #include <AK/Math.h>
+#include <AK/ScopeGuard.h>
 #include <AK/Stream.h>
 #include <AK/String.h>
 #include <AK/StringBuilder.h>
@@ -33,6 +34,8 @@ FlacLoaderPlugin::FlacLoaderPlugin(const StringView& path)
 
     m_stream = make<FlacInputStream>(Core::InputFileStream(*m_file));
     reset();
+    if (!m_valid)
+        return;
 
     m_resampler = make<ResampleHelper<double>>(m_sample_rate, 44100);
 }
@@ -49,6 +52,8 @@ FlacLoaderPlugin::FlacLoaderPlugin(const ByteBuffer& buffer)
     if (!m_valid)
         return;
     reset();
+    if (!m_valid)
+        return;
 
     m_resampler = make<ResampleHelper<double>>(m_sample_rate, 44100);
 }
@@ -70,10 +75,12 @@ bool FlacLoaderPlugin::parse_header()
         }
         return InputBitStream(m_stream->get<InputMemoryStream>());
     }();
+    ScopeGuard clear_bit_input_errors([&bit_input] { bit_input.handle_any_error(); });
 
 #define CHECK_OK(msg)                                                      \
     do {                                                                   \
         if (!ok) {                                                         \
+            m_stream->handle_any_error();                                  \
             m_error_string = String::formatted("Parsing failed: {}", msg); \
             return {};                                                     \
         }                                                                  \
@@ -94,6 +101,7 @@ bool FlacLoaderPlugin::parse_header()
     CHECK_OK("First block type");
     InputMemoryStream streaminfo_data_memory(streaminfo.data.bytes());
     InputBitStream streaminfo_data(streaminfo_data_memory);
+    ScopeGuard clear_streaminfo_errors([&streaminfo_data] { streaminfo_data.handle_any_error(); });
 
     // STREAMINFO block
     m_min_block_size = streaminfo_data.read_bits_big_endian(16);
@@ -125,9 +133,13 @@ bool FlacLoaderPlugin::parse_header()
     }
 
     m_total_samples = streaminfo_data.read_bits_big_endian(36);
+    ok = ok && (m_total_samples > 0);
+    CHECK_OK("Number of samples");
     // Parse checksum into a buffer first
     ByteBuffer md5_checksum = ByteBuffer::create_uninitialized(128 / 8);
-    streaminfo_data.read(md5_checksum);
+    auto md5_bytes_read = streaminfo_data.read(md5_checksum);
+    ok = ok && (md5_bytes_read == md5_checksum.size());
+    CHECK_OK("MD5 Checksum");
     md5_checksum.bytes().copy_to({ m_md5_checksum, sizeof(m_md5_checksum) });
 
     // Parse other blocks
@@ -143,6 +155,11 @@ bool FlacLoaderPlugin::parse_header()
         CHECK_OK(m_error_string);
     }
 
+    if (m_stream->handle_any_error()) {
+        m_error_string = "Parsing failed: Stream";
+        return false;
+    }
+
     if constexpr (AFLACLOADER_DEBUG) {
         // HACK: u128 should be able to format itself
         StringBuilder checksum_string;
@@ -203,11 +220,13 @@ void FlacLoaderPlugin::reset()
 
 void FlacLoaderPlugin::seek(const int position)
 {
-    m_stream->seek(position);
+    if (!m_stream->seek(position)) {
+        m_error_string = String::formatted("Invalid seek position {}", position);
+        m_valid = false;
+    }
 }
 
-// TODO implement these
-RefPtr<Buffer> FlacLoaderPlugin::get_more_samples([[maybe_unused]] size_t max_bytes_to_read_from_input)
+RefPtr<Buffer> FlacLoaderPlugin::get_more_samples(size_t max_bytes_to_read_from_input)
 {
     Vector<Frame> samples;
     ssize_t remaining_samples = m_total_samples - m_loaded_samples;
@@ -220,7 +239,7 @@ RefPtr<Buffer> FlacLoaderPlugin::get_more_samples([[maybe_unused]] size_t max_by
         if (!m_current_frame.has_value()) {
             next_frame();
             if (!m_error_string.is_empty()) {
-                dbgln("Frame parsing error: {}", m_error_string);
+                m_error_string = String::formatted("Frame parsing error: {}", m_error_string);
                 return nullptr;
             }
             // HACK: Test the start of the next subframe
@@ -248,6 +267,7 @@ void FlacLoaderPlugin::next_frame()
         if (!ok) {                                                                                                         \
             m_error_string = String::formatted("Frame parsing failed: {}", msg);                                           \
             bit_stream.align_to_byte_boundary();                                                                           \
+            bit_stream.handle_any_error();                                                                                 \
             dbgln_if(AFLACLOADER_DEBUG, "Crash in FLAC loader: next bytes are {:x}", bit_stream.read_bits_big_endian(32)); \
             return;                                                                                                        \
         }                                                                                                                  \
@@ -834,5 +854,4 @@ i32 rice_to_signed(u32 x)
     // copies the sign's sign onto the actual magnitude of x
     return (i32)(sign ^ (x >> 1));
 }
-
 }

Userland/Libraries/LibAudio/FlacLoader.h

@@ -22,11 +22,26 @@ class FlacInputStream : public Variant<Core::InputFileStream, InputMemoryStream>
 public:
     using Variant<Core::InputFileStream, InputMemoryStream>::Variant;
 
-    void seek(size_t pos)
+    bool seek(size_t pos)
     {
-        this->visit(
-            [&](auto& stream) {
+        return this->visit(
+            [&](Core::InputFileStream& stream) {
+                return stream.seek(pos);
+            },
+            [&](InputMemoryStream& stream) {
+                if (pos >= stream.bytes().size()) {
+                    return false;
+                }
                 stream.seek(pos);
+                return true;
+            });
+    }
+
+    bool handle_any_error()
+    {
+        return this->visit(
+            [&](auto& stream) {
+                return stream.handle_any_error();
             });
     }
 
@@ -56,6 +71,11 @@ class FlacLoaderPlugin : public LoaderPlugin {
 public:
     FlacLoaderPlugin(const StringView& path);
     FlacLoaderPlugin(const ByteBuffer& buffer);
+    ~FlacLoaderPlugin()
+    {
+        if (m_stream)
+            m_stream->handle_any_error();
+    }
 
     virtual bool sniff() override;