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get: harden repos.json save/load against empty/corrupted state #33

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160 changes: 126 additions & 34 deletions src/Get.cpp
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Original file line number Diff line number Diff line change
@@ -1,11 +1,21 @@
#include <algorithm>
#include <cstdarg>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <errno.h>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <sys/stat.h>
#include <sys/types.h>
#include <unordered_set>

#if !defined(WIN32) && !defined(_WIN32)
#include <fcntl.h>
#include <unistd.h>
#endif

#include "rapidjson/document.h"
#include "rapidjson/istreamwrapper.h"
#include "rapidjson/stringbuffer.h"
Expand Down Expand Up @@ -39,9 +49,12 @@ Get::Get(
// printf("--> Using \"./sdroot\" as local download root directory\n");
// my_mkdir("./sdroot");

my_mkdir(config_dir.data());
my_mkdir(mPkg_path.c_str());
my_mkdir(mTmp_path.c_str());
if (!mkpath(config_path))
printf("--> Could not create config dir %s\n", config_path.c_str());
if (!mkpath(mPkg_path))
printf("--> Could not create packages dir %s\n", mPkg_path.c_str());
if (!mkpath(mTmp_path))
printf("--> Could not create tmp dir %s\n", mTmp_path.c_str());

printf("--> Using \"%s\" as repo list\n", mRepos_path.c_str());

Expand Down Expand Up @@ -155,8 +168,11 @@ void Get::addAndRemoveReposByURL(
}
}

// Saves the repos from our current Get object to disk
// Saves the repos from our current Get object to disk, via a tmp file and
// atomic rename so a crash mid-write can't truncate repos.json.
void Get::saveRepos() {
std::string tmpPath = mRepos_path + ".tmp";

Document d;
d.SetObject();
Document::AllocatorType& allocator = d.GetAllocator();
Expand All @@ -165,10 +181,6 @@ void Get::saveRepos() {

for (auto& repo : repos) {
Value repoObj(kObjectType);
printf("--> Saving repo %s\n", repo->getName().c_str());
printf("--> Saving repo %s\n", repo->getUrl().c_str());
printf("--> Saving repo %s\n", repo->getType().c_str());

repoObj.AddMember("name", rapidjson::Value(repo->getName().c_str(), allocator), allocator);
repoObj.AddMember("url", rapidjson::Value(repo->getUrl().c_str(), allocator), allocator);
repoObj.AddMember("type", rapidjson::Value(repo->getType().c_str(), allocator), allocator);
Expand All @@ -178,55 +190,108 @@ void Get::saveRepos() {

d.AddMember("repos", reposOut, allocator);

std::ofstream file(mRepos_path);
StringBuffer buffer;
Writer<StringBuffer> writer(buffer);
d.Accept(writer);
std::cout << buffer.GetString() << std::endl;
file << buffer.GetString();
file.close();

{
std::ofstream file(tmpPath);
if (!file.is_open()) {
printf("--> Could not open %s for writing\n", tmpPath.c_str());
return;
}
file << buffer.GetString();
file.flush();
if (file.fail()) {
printf("--> Write failed for %s\n", tmpPath.c_str());
file.close();
std::remove(tmpPath.c_str());
return;
}
}

#if !defined(WIN32) && !defined(_WIN32)
// fsync so the new content reaches the SD card before the rename
int fd = open(tmpPath.c_str(), O_RDONLY);
if (fd >= 0) {
fsync(fd);
close(fd);
}
#endif

// std::filesystem::rename atomically replaces an existing destination on
// both POSIX and Windows; plain std::rename does not on Windows.
std::error_code ec;
std::filesystem::rename(tmpPath, mRepos_path, ec);
if (ec) {
printf("--> Could not rename %s to %s: %s\n", tmpPath.c_str(), mRepos_path.c_str(), ec.message().c_str());
std::filesystem::remove(tmpPath, ec);
return;
}

#if !defined(WIN32) && !defined(_WIN32)
// fsync the directory so the rename itself survives a power-off
std::string parentDir = dir_name(mRepos_path);
if (parentDir.empty()) parentDir = ".";
int dirFd = open(parentDir.c_str(), O_RDONLY);
if (dirFd >= 0) {
fsync(dirFd);
close(dirFd);
}
#endif
}

/**
Load any repos from a config file into the repos vector.
Load any repos from a config file into the repos vector. Regenerates the
default repo when the file is missing/empty/corrupted, or when it parses to
a valid but empty repos array.
**/
void Get::loadRepos()
{
repos.clear();

auto& config_path = mRepos_path;
std::ifstream ifs(config_path);

if (!ifs.good() || ifs.peek() == std::ifstream::traits_type::eof())
{
printf("--> Could not load repos from %s, generating default GET repos.json\n", config_path.c_str());
auto generateDefault = [&](const char* reason, bool writeToDisk = true) {
printf("--> Generating default repos.json (%s)\n", reason);

#if defined(WII) || defined(_3DS) || defined(WII_MOCK)
auto defaultRepo = GetRepo::createRepo("Default Repo", this->mDefaultRepo, true, this->mDefaultRepoType, mPkg_path);
#else
auto defaultRepo = std::make_unique<GetRepo>("Default Repo", this->mDefaultRepo, true);
#endif

Document d;
d.Parse(Repo::generateRepoJson(*defaultRepo).c_str());
if (writeToDisk)
{
Document d;
d.Parse(Repo::generateRepoJson(*defaultRepo).c_str());

std::ofstream file(config_path);
StringBuffer buffer;
Writer<StringBuffer> writer(buffer);
d.Accept(writer);
file << buffer.GetString();
file.close();
std::ofstream file(config_path);
if (file.is_open())
{
StringBuffer buffer;
Writer<StringBuffer> writer(buffer);
d.Accept(writer);
file << buffer.GetString();
file.close();
}
else
{
printf("--> Could not write default to %s, using in-memory only\n", config_path.c_str());
}
}

ifs = std::ifstream(config_path);
// keep an in-memory default even if the disk write failed or was skipped
repos.clear();
repos.push_back(std::move(defaultRepo));
};

if (!ifs.good())
{
printf("--> Could not generate a new repos.json\n");
std::ifstream ifs(config_path);

// manually create a repo, no file access (so we append now, since we won't be able to load later)
repos.push_back(std::move(defaultRepo));
return;
}
if (!ifs.good() || ifs.peek() == std::ifstream::traits_type::eof())
{
generateDefault("file missing or empty");
return;
}

IStreamWrapper isw(ifs);
Expand All @@ -236,7 +301,28 @@ void Get::loadRepos()

if (!ok || !doc.HasMember("repos"))
{
printf("--> Invalid format in %s", config_path.c_str());
printf("--> Invalid JSON in %s\n", config_path.c_str());
ifs.close();

// preserve the corrupted file so the user can recover from it manually;
// fall back to a timestamped name so a previous .bad isn't clobbered
std::string badPath = config_path + ".bad";
std::error_code ec;
if (std::filesystem::exists(badPath, ec))
badPath = config_path + ".bad." + std::to_string(time(nullptr));

std::filesystem::rename(config_path, badPath, ec);
if (ec)
{
// can't preserve safely; leave the bad file alone and only run an in-memory default
printf("--> Could not preserve corrupted file (%s); leaving %s untouched\n", ec.message().c_str(), config_path.c_str());
generateDefault("invalid JSON, no on-disk write", false);
}
else
{
printf("--> Moved corrupted file to %s\n", badPath.c_str());
generateDefault("invalid JSON");
}
return;
}

Expand Down Expand Up @@ -268,6 +354,12 @@ void Get::loadRepos()
repos.push_back(std::move(repo));
}
}

if (repos.empty())
{
ifs.close();
generateDefault("repos array was empty");
}
}

void Get::update()
Expand Down
1 change: 1 addition & 0 deletions src/Utils.hpp
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
#endif

#include <algorithm>
#include <cstdint>
#include <stdio.h>
#include <string>

Expand Down
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