Add F2FS support for apexd

Filesystem type used for apex_payload is retrieved when opening an APEX.
Magic bytes are read are the expected offset in the filesystem.
If neither f2fs magic nor ext4 magic can be found, it fails.

Test: boot successfuly with ext4 apexes
install succesfuly ext4 / f2fs apexes
atest ApexTestCases

Bug: 158453869

Change-Id: If8eb9f6f28f81cdb0915c63f51482827138bf9f8
Merged-In: If8eb9f6f28f81cdb0915c63f51482827138bf9f8

1 files changed, 36 insertions, 2 deletions

diff --git a/apexd/apex_file.cpp b/apexd/apex_file.cpp
index f91b5d1..abcda7d 100644
--- a/apexd/apex_file.cpp
+++ b/apexd/apex_file.cpp
@@ -37,6 +37,7 @@
 #include "apexd_utils.h"
 #include "string_log.h"
 
+using android::base::borrowed_fd;
 using android::base::EndsWith;
 using android::base::Error;
 using android::base::ReadFullyAtOffset;
@@ -52,6 +53,28 @@ namespace {
 constexpr const char* kImageFilename = "apex_payload.img";
 constexpr const char* kBundledPublicKeyFilename = "apex_pubkey";
 
+struct FsMagic {
+  const char* type;
+  int32_t offset;
+  int16_t len;
+  const char* magic;
+};
+constexpr const FsMagic kFsType[] = {{"f2fs", 1024, 4, "\x10\x20\xf5\xf2"},
+                                     {"ext4", 1024 + 0x38, 2, "\123\357"}};
+
+Result<std::string> RetrieveFsType(borrowed_fd fd, int32_t image_offset) {
+  for (const auto& fs : kFsType) {
+    char buf[fs.len];
+    if (!ReadFullyAtOffset(fd, buf, fs.len, image_offset + fs.offset)) {
+      return ErrnoError() << "Couldn't read filesystem magic";
+    }
+    if (memcmp(buf, fs.magic, fs.len) == 0) {
+      return std::string(fs.type);
+    }
+  }
+  return Error() << "Couldn't find filesystem magic";
+}
+
 }  // namespace
 
 Result<ApexFile> ApexFile::Open(const std::string& path) {
@@ -63,7 +86,12 @@ Result<ApexFile> ApexFile::Open(const std::string& path) {
   ZipArchiveHandle handle;
   auto handle_guard =
       android::base::make_scope_guard([&handle] { CloseArchive(handle); });
-  int ret = OpenArchive(path.c_str(), &handle);
+  unique_fd fd(open(path.c_str(), O_RDONLY | O_BINARY | O_CLOEXEC));
+  if (fd < 0) {
+    return Error() << "Failed to open package " << path << ": "
+                   << "I/O error";
+  }
+  int ret = OpenArchiveFd(fd.get(), path.c_str(), &handle, false);
   if (ret < 0) {
     return Error() << "Failed to open package " << path << ": "
                    << ErrorCodeString(ret);
@@ -79,6 +107,12 @@ Result<ApexFile> ApexFile::Open(const std::string& path) {
   image_offset = entry.offset;
   image_size = entry.uncompressed_length;
 
+  auto fs_type = RetrieveFsType(fd, image_offset);
+  if (!fs_type.ok()) {
+    return Error() << "Failed to retrieve filesystem type for " << path << ": "
+                   << fs_type.error();
+  }
+
   ret = FindEntry(handle, kManifestFilenamePb, &entry);
   if (ret < 0) {
     return Error() << "Could not find entry \"" << kManifestFilenamePb
@@ -113,7 +147,7 @@ Result<ApexFile> ApexFile::Open(const std::string& path) {
   }
 
   return ApexFile(path, image_offset, image_size, std::move(*manifest), pubkey,
-                  isPathForBuiltinApexes(path));
+                  isPathForBuiltinApexes(path), *fs_type);
 }
 
 // AVB-related code.