Add utility functions for FUSE.

The CL adds utility functions to framework to parse FUSE messages
from the kernel. The library will be used from framework JNI and service
JNI.

Bug: 32260320
Test: libappfuse_test
Change-Id: Ib89b26d34789e6c26a3288beceb3ea145c1ae780

4 files changed, 425 insertions, 0 deletions

diff --git a/libappfuse/Android.bp b/libappfuse/Android.bp
new file mode 100644
index 000000000..8d24af10d
--- /dev/null
+++ b/libappfuse/Android.bp
@@ -0,0 +1,26 @@
+// Copyright 2016 The Android Open Source Project
+
+cc_defaults {
+    name: "libappfuse_defaults",
+    local_include_dirs: ["include"],
+    shared_libs: ["libbase"],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    clang: true
+}
+
+cc_library_shared {
+    name: "libappfuse",
+    defaults: ["libappfuse_defaults"],
+    export_include_dirs: ["include"],
+    srcs: ["AppFuse.cc"]
+}
+
+cc_test {
+    name: "libappfuse_test",
+    defaults: ["libappfuse_defaults"],
+    shared_libs: ["libappfuse"],
+    srcs: ["tests/AppFuseTest.cc"]
+}
diff --git a/libappfuse/AppFuse.cc b/libappfuse/AppFuse.cc
new file mode 100644
index 000000000..8701c4800
--- /dev/null
+++ b/libappfuse/AppFuse.cc
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specic language governing permissions and
+ * limitations under the License.
+ */
+
+#include "libappfuse/AppFuse.h"
+
+#include <inttypes.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <algorithm>
+
+#include <android-base/logging.h>
+#include <android-base/macros.h>
+
+namespace android {
+
+template <typename T, typename Header>
+bool FuseMessage<T, Header>::CheckHeaderLength() const {
+  if (sizeof(Header) <= header.len && header.len <= sizeof(T)) {
+    return true;
+  } else {
+    LOG(ERROR) << "Packet size is invalid=" << header.len;
+    return false;
+  }
+}
+
+template <typename T, typename Header>
+bool FuseMessage<T, Header>::CheckResult(
+    int result, const char* operation_name) const {
+  if (result >= 0 && static_cast<uint32_t>(result) == header.len) {
+    return true;
+  } else {
+    PLOG(ERROR) << "Failed to " << operation_name
+        << " a packet from FD. result=" << result << " header.len="
+        << header.len;
+    return false;
+  }
+}
+
+template <typename T, typename Header>
+bool FuseMessage<T, Header>::Read(int fd) {
+  const ssize_t result = TEMP_FAILURE_RETRY(::read(fd, this, sizeof(T)));
+  return CheckHeaderLength() && CheckResult(result, "read");
+}
+
+template <typename T, typename Header>
+bool FuseMessage<T, Header>::Write(int fd) const {
+  if (!CheckHeaderLength()) {
+    return false;
+  }
+  const ssize_t result = TEMP_FAILURE_RETRY(::write(fd, this, header.len));
+  return CheckResult(result, "write");
+}
+
+template struct FuseMessage<FuseRequest, fuse_in_header>;
+template struct FuseMessage<FuseResponse, fuse_out_header>;
+
+void FuseResponse::ResetHeader(
+    uint32_t data_length, int32_t error, uint64_t unique) {
+  CHECK_LE(error, 0) << "error should be zero or negative.";
+  header.len = sizeof(fuse_out_header) + data_length;
+  header.error = error;
+  header.unique = unique;
+}
+
+void FuseResponse::Reset(uint32_t data_length, int32_t error, uint64_t unique) {
+  memset(this, 0, sizeof(fuse_out_header) + data_length);
+  ResetHeader(data_length, error, unique);
+}
+
+void FuseBuffer::HandleInit() {
+  const fuse_init_in* const in = &request.init_in;
+
+  // Before writing |out|, we need to copy data from |in|.
+  const uint64_t unique = request.header.unique;
+  const uint32_t minor = in->minor;
+  const uint32_t max_readahead = in->max_readahead;
+
+  // Kernel 2.6.16 is the first stable kernel with struct fuse_init_out
+  // defined (fuse version 7.6). The structure is the same from 7.6 through
+  // 7.22. Beginning with 7.23, the structure increased in size and added
+  // new parameters.
+  if (in->major != FUSE_KERNEL_VERSION || in->minor < 6) {
+    LOG(ERROR) << "Fuse kernel version mismatch: Kernel version " << in->major
+        << "." << in->minor << " Expected at least " << FUSE_KERNEL_VERSION
+        << ".6";
+    response.Reset(0, -EPERM, unique);
+    return;
+  }
+
+  // We limit ourselves to 15 because we don't handle BATCH_FORGET yet
+  size_t response_size = sizeof(fuse_init_out);
+#if defined(FUSE_COMPAT_22_INIT_OUT_SIZE)
+  // FUSE_KERNEL_VERSION >= 23.
+
+  // If the kernel only works on minor revs older than or equal to 22,
+  // then use the older structure size since this code only uses the 7.22
+  // version of the structure.
+  if (minor <= 22) {
+    response_size = FUSE_COMPAT_22_INIT_OUT_SIZE;
+  }
+#endif
+
+  response.Reset(response_size, kFuseSuccess, unique);
+  fuse_init_out* const out = &response.init_out;
+  out->major = FUSE_KERNEL_VERSION;
+  // We limit ourselves to 15 because we don't handle BATCH_FORGET yet.
+  out->minor = std::min(minor, 15u);
+  out->max_readahead = max_readahead;
+  out->flags = FUSE_ATOMIC_O_TRUNC | FUSE_BIG_WRITES;
+  out->max_background = 32;
+  out->congestion_threshold = 32;
+  out->max_write = kFuseMaxWrite;
+}
+
+void FuseBuffer::HandleNotImpl() {
+  LOG(VERBOSE) << "NOTIMPL op=" << request.header.opcode << " uniq="
+      << request.header.unique << " nid=" << request.header.nodeid;
+  const uint64_t unique = request.header.unique;
+  response.Reset(0, -ENOSYS, unique);
+}
+
+}  // namespace android
diff --git a/libappfuse/include/libappfuse/AppFuse.h b/libappfuse/include/libappfuse/AppFuse.h
new file mode 100644
index 000000000..b6af48d78
--- /dev/null
+++ b/libappfuse/include/libappfuse/AppFuse.h
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specic language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_LIBAPPFUSE_APPFUSE_H_
+#define ANDROID_LIBAPPFUSE_APPFUSE_H_
+
+#include <linux/fuse.h>
+
+namespace android {
+
+// The numbers came from sdcard.c.
+// Maximum number of bytes to write/read in one request/one reply.
+constexpr size_t kFuseMaxWrite = 256 * 1024;
+constexpr size_t kFuseMaxRead = 128 * 1024;
+constexpr int32_t kFuseSuccess = 0;
+
+template<typename T, typename Header>
+struct FuseMessage {
+  Header header;
+  bool Read(int fd);
+  bool Write(int fd) const;
+ private:
+  bool CheckHeaderLength() const;
+  bool CheckResult(int result, const char* operation_name) const;
+};
+
+struct FuseRequest : public FuseMessage<FuseRequest, fuse_in_header> {
+  union {
+    struct {
+      fuse_write_in write_in;
+      char write_data[kFuseMaxWrite];
+    };
+    fuse_open_in open_in;
+    fuse_init_in init_in;
+    fuse_read_in read_in;
+    char lookup_name[];
+  };
+};
+
+struct FuseResponse : public FuseMessage<FuseResponse, fuse_out_header> {
+  union {
+    fuse_init_out init_out;
+    fuse_entry_out entry_out;
+    fuse_attr_out attr_out;
+    fuse_open_out open_out;
+    char read_data[kFuseMaxRead];
+    fuse_write_out write_out;
+  };
+  void Reset(uint32_t data_length, int32_t error, uint64_t unique);
+  void ResetHeader(uint32_t data_length, int32_t error, uint64_t unique);
+};
+
+union FuseBuffer {
+  FuseRequest request;
+  FuseResponse response;
+
+  void HandleInit();
+  void HandleNotImpl();
+};
+
+}  // namespace android
+
+#endif  // ANDROID_LIBAPPFUSE_APPFUSE_H_
diff --git a/libappfuse/tests/AppFuseTest.cc b/libappfuse/tests/AppFuseTest.cc
new file mode 100644
index 000000000..8c2cc4712
--- /dev/null
+++ b/libappfuse/tests/AppFuseTest.cc
@@ -0,0 +1,187 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specic language governing permissions and
+ * limitations under the License.
+ */
+
+#include "libappfuse/AppFuse.h"
+
+#include <fcntl.h>
+#include <string.h>
+#include <sys/socket.h>
+
+#include <android-base/unique_fd.h>
+#include <gtest/gtest.h>
+
+namespace android {
+
+constexpr char kTempFile[] = "/data/local/tmp/appfuse_test_dump";
+
+void OpenTempFile(android::base::unique_fd* fd) {
+  fd->reset(open(kTempFile, O_CREAT | O_RDWR));
+  ASSERT_NE(-1, *fd) << strerror(errno);
+  unlink(kTempFile);
+  ASSERT_NE(-1, *fd) << strerror(errno);
+}
+
+void TestReadInvalidLength(size_t headerSize, size_t write_size) {
+  android::base::unique_fd fd;
+  OpenTempFile(&fd);
+
+  char buffer[std::max(headerSize, sizeof(FuseRequest))];
+  FuseRequest* const packet = reinterpret_cast<FuseRequest*>(buffer);
+  packet->header.len = headerSize;
+  ASSERT_NE(-1, write(fd, packet, write_size)) << strerror(errno);
+
+  lseek(fd, 0, SEEK_SET);
+  EXPECT_FALSE(packet->Read(fd));
+}
+
+void TestWriteInvalidLength(size_t size) {
+  android::base::unique_fd fd;
+  OpenTempFile(&fd);
+
+  char buffer[std::max(size, sizeof(FuseRequest))];
+  FuseRequest* const packet = reinterpret_cast<FuseRequest*>(buffer);
+  packet->header.len = size;
+  EXPECT_FALSE(packet->Write(fd));
+}
+
+// Use FuseRequest as a template instance of FuseMessage.
+
+TEST(FuseMessageTest, ReadAndWrite) {
+  android::base::unique_fd fd;
+  OpenTempFile(&fd);
+
+  FuseRequest request;
+  request.header.len = sizeof(FuseRequest);
+  request.header.opcode = 1;
+  request.header.unique = 2;
+  request.header.nodeid = 3;
+  request.header.uid = 4;
+  request.header.gid = 5;
+  request.header.pid = 6;
+  strcpy(request.lookup_name, "test");
+
+  ASSERT_TRUE(request.Write(fd));
+
+  memset(&request, 0, sizeof(FuseRequest));
+  lseek(fd, 0, SEEK_SET);
+
+  ASSERT_TRUE(request.Read(fd));
+  EXPECT_EQ(sizeof(FuseRequest), request.header.len);
+  EXPECT_EQ(1u, request.header.opcode);
+  EXPECT_EQ(2u, request.header.unique);
+  EXPECT_EQ(3u, request.header.nodeid);
+  EXPECT_EQ(4u, request.header.uid);
+  EXPECT_EQ(5u, request.header.gid);
+  EXPECT_EQ(6u, request.header.pid);
+  EXPECT_STREQ("test", request.lookup_name);
+}
+
+TEST(FuseMessageTest, Read_InconsistentLength) {
+  TestReadInvalidLength(sizeof(fuse_in_header), sizeof(fuse_in_header) + 1);
+}
+
+TEST(FuseMessageTest, Read_TooLong) {
+  TestReadInvalidLength(sizeof(FuseRequest) + 1, sizeof(FuseRequest) + 1);
+}
+
+TEST(FuseMessageTest, Read_TooShort) {
+  TestReadInvalidLength(sizeof(fuse_in_header) - 1, sizeof(fuse_in_header) - 1);
+}
+
+TEST(FuseMessageTest, Write_TooLong) {
+  TestWriteInvalidLength(sizeof(FuseRequest) + 1);
+}
+
+TEST(FuseMessageTest, Write_TooShort) {
+  TestWriteInvalidLength(sizeof(fuse_in_header) - 1);
+}
+
+TEST(FuseResponseTest, Reset) {
+  FuseResponse response;
+  // Write 1 to the first ten bytes.
+  memset(response.read_data, 'a', 10);
+
+  response.Reset(0, -1, 2);
+  EXPECT_EQ(sizeof(fuse_out_header), response.header.len);
+  EXPECT_EQ(-1, response.header.error);
+  EXPECT_EQ(2u, response.header.unique);
+  EXPECT_EQ('a', response.read_data[0]);
+  EXPECT_EQ('a', response.read_data[9]);
+
+  response.Reset(5, -4, 3);
+  EXPECT_EQ(sizeof(fuse_out_header) + 5, response.header.len);
+  EXPECT_EQ(-4, response.header.error);
+  EXPECT_EQ(3u, response.header.unique);
+  EXPECT_EQ(0, response.read_data[0]);
+  EXPECT_EQ(0, response.read_data[1]);
+  EXPECT_EQ(0, response.read_data[2]);
+  EXPECT_EQ(0, response.read_data[3]);
+  EXPECT_EQ(0, response.read_data[4]);
+  EXPECT_EQ('a', response.read_data[5]);
+}
+
+TEST(FuseResponseTest, ResetHeader) {
+  FuseResponse response;
+  // Write 1 to the first ten bytes.
+  memset(response.read_data, 'a', 10);
+
+  response.ResetHeader(0, -1, 2);
+  EXPECT_EQ(sizeof(fuse_out_header), response.header.len);
+  EXPECT_EQ(-1, response.header.error);
+  EXPECT_EQ(2u, response.header.unique);
+  EXPECT_EQ('a', response.read_data[0]);
+  EXPECT_EQ('a', response.read_data[9]);
+
+  response.ResetHeader(5, -4, 3);
+  EXPECT_EQ(sizeof(fuse_out_header) + 5, response.header.len);
+  EXPECT_EQ(-4, response.header.error);
+  EXPECT_EQ(3u, response.header.unique);
+  EXPECT_EQ('a', response.read_data[0]);
+  EXPECT_EQ('a', response.read_data[9]);
+}
+
+TEST(FuseBufferTest, HandleInit) {
+  FuseBuffer buffer;
+  memset(&buffer, 0, sizeof(FuseBuffer));
+
+  buffer.request.header.opcode = FUSE_INIT;
+  buffer.request.init_in.major = FUSE_KERNEL_VERSION;
+  buffer.request.init_in.minor = FUSE_KERNEL_MINOR_VERSION;
+
+  buffer.HandleInit();
+
+  ASSERT_EQ(sizeof(fuse_out_header) + sizeof(fuse_init_out),
+            buffer.response.header.len);
+  EXPECT_EQ(kFuseSuccess, buffer.response.header.error);
+  EXPECT_EQ(static_cast<unsigned int>(FUSE_KERNEL_VERSION),
+            buffer.response.init_out.major);
+  EXPECT_EQ(15u, buffer.response.init_out.minor);
+  EXPECT_EQ(static_cast<unsigned int>(FUSE_ATOMIC_O_TRUNC | FUSE_BIG_WRITES),
+      buffer.response.init_out.flags);
+  EXPECT_EQ(kFuseMaxWrite, buffer.response.init_out.max_write);
+}
+
+TEST(FuseBufferTest, HandleNotImpl) {
+  FuseBuffer buffer;
+  memset(&buffer, 0, sizeof(FuseBuffer));
+
+  buffer.HandleNotImpl();
+
+  ASSERT_EQ(sizeof(fuse_out_header), buffer.response.header.len);
+  EXPECT_EQ(-ENOSYS, buffer.response.header.error);
+}
+}
+  // namespace android