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steamns: add -H switch to behave like chome

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Taeyeon Mori 4 years ago
parent 7c46de9fa4
commit d7a566f5f8
2 changed files with 96 additions and 38 deletions
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  1. 29
      src/kofs.hpp
  2. 105
      src/steamns.cpp

29
src/kofs.hpp
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@ -9,6 +9,7 @@
#include <dirent.h>
#include <unistd.h>
#include <stdlib.h>
#include <string>
#include <filesystem>
@ -18,6 +19,7 @@ using namespace std::filesystem;
/**
* Helper struct for functions that require a c-string path
* @note Does not copy or own contents. original string/path object must be kept alive.
*/
struct cpath {
const char *path;
@ -107,4 +109,31 @@ public:
return iterator(*this, true);
}
};
/**
* Like Python tempfile.mkdtemp().
* User-callable function to create and return a unique temporary
* directory. The return value is the pathname of the directory.
* @param prefix If given, the file name will begin with that prefix, otherwise a default prefix is used.
* @param dir If given, the file will be created in that directory, otherwise a default directory is used.
* The directory is readable, writable, and searchable only by the creating user.
* Caller is responsible for deleting the directory when done with it.
*/
fs::path create_temporary_directory(std::string prefix={}, fs::path dir={}) {
if (prefix.empty()) prefix = program_invocation_name;
if (dir.empty()) dir = fs::temp_directory_path();
auto ec = std::error_code{};
if (!dir.is_absolute()) dir = fs::absolute(dir, ec);
if (ec)
return {};
auto dirname = dir.string();
auto size = dirname.length()+1+prefix.length()+1+6+1;
char buf[size];
if (snprintf(buf, size, "%s/%s-XXXXXX", dirname.c_str(), prefix.c_str())<0)
return {};
if (::mkdtemp(buf) == nullptr)
return {};
return {buf};
}
} // namespace ko::fs

105
src/steamns.cpp
Unescape View File

@ -18,7 +18,7 @@ namespace fs = std::filesystem;
// TODO: XDG_RUNTIME_DIR etc
constexpr auto ROOT_DIR = ".local/steam";
constexpr auto DEFAULT_CMD = (const char*[]){"/bin/bash", nullptr};
constexpr auto DEFAULT_CMD = std::array<char const *const, 2>{"/bin/bash", nullptr};
constexpr auto STEAM_USER = "steamuser";
// Helpers
@ -98,7 +98,7 @@ namespace nsproc {
fs::path root_path, home_path, pwd;
char *const *exec_argv; // must be nullptr-terminated
uid_t uid, gid;
bool mounts, gui_mounts, system_ro, keep_root, dummy_mode, pid_ns;
bool mounts, gui_mounts, system_ro, keep_root, dummy_mode, pid_ns, use_host_root;
std::optional<fs::path> setup_exec;
int ns_path_fd;
};
@ -192,22 +192,59 @@ namespace nsproc {
int nsproc_create(const config &conf, proc_future<int> *report) {
// Mount Namespace
fs::path root = conf.root_path;
if (conf.mounts) {
// Slightly hacky
auto run_media_path = ko::util::str("/run/media/", getenv("USER"));
auto [err, where] = ko::util::cvshort()
// Mount base system: /, /proc, /sys, /dev, /tmp, /run
.then(ko::ns::mount::mount_core, conf.root_path)
// Mount /usr readonly because file permissions are useless in a single-uid namespace
.ifthen(conf.system_ro && fs::exists(conf.root_path / "usr"),
ko::ns::mount::protect_path, conf.root_path / "usr")
.ifthen(conf.system_ro && fs::exists(conf.root_path / "etc"),
ko::ns::mount::protect_path, conf.root_path / "etc")
// Recursively bind in /media and /run/media/$USER for games
.ifthen("bind_media", fs::exists("/media") && fs::exists(conf.root_path / "media"),
ko::os::bind, "/media", conf.root_path / "media", MS_REC)
.ifthen("bind_run_media", fs::exists(run_media_path), [&conf, &run_media_path] () {
auto target_path = conf.root_path / "run/media" / STEAM_USER;
.then([&conf, &root]() -> ko::util::cvresult {
if (conf.use_host_root) {
root = ko::fs::create_temporary_directory();
auto rel_home = conf.home_path.relative_path();
if (root.empty())
return {1, "create temporary directory"};
return ko::util::cvshort()
.then("bind_host_root",
ko::os::bind, "/", root, MS_REC|MS_SLAVE)
// Make / read-only
.ifthen("remount_ro", conf.system_ro,
ko::os::bind, "/", root, MS_REMOUNT|MS_RDONLY)
.ifthen("mount_tmp", fs::exists(root / "tmp"),
ko::os::mount, "tmp", root / "tmp", "tmpfs", 0, nullptr)
.ifthen("mount_run", fs::exists(root / "run"),
ko::os::mount, "run", root / "run", "tmpfs", 0, nullptr)
.then("bind_home",
ko::os::bind, conf.root_path / rel_home, root / rel_home, MS_REC|MS_SLAVE);
} else {
return ko::util::cvshort()
.then(ko::ns::mount::mount_core, root)
// Mount /usr readonly because file permissions are useless in a single-uid namespace
.ifthen(conf.system_ro && fs::exists(root / "usr"),
ko::ns::mount::protect_path, root / "usr")
.ifthen(conf.system_ro && fs::exists(root / "etc"),
ko::ns::mount::protect_path, root / "etc")
// Recursively bind in /media and /run/media/$USER for games
.ifthen("bind_media", fs::exists("/media") && fs::exists(root / "media"),
ko::os::bind, "/media", root / "media", MS_REC)
// Add a dummy user to /etc/passwd
.then("bind_passwd", [&conf, &root]() {
auto etc_passwd = root / "etc/passwd";
auto tmp_passwd = root / "tmp/passwd";
if (fs::exists(etc_passwd)) {
fs::copy(etc_passwd, tmp_passwd);
auto s = std::fstream(tmp_passwd, std::fstream::out | std::fstream::app);
s << std::endl << STEAM_USER << ":x:" << conf.uid << ":" << conf.gid << ":Steam Container User:" << conf.home_path.native() << ":/bin/bash" << std::endl;
s.close();
return ko::os::bind(tmp_passwd, etc_passwd);
}
return 0;
});
}
})
.ifthen("bind_run_media", fs::exists(run_media_path), [&conf, &root, &run_media_path] () {
auto target_path = conf.use_host_root ? (root / run_media_path) : (root / "run/media" / STEAM_USER);
std::error_code ec;
fs::create_directories(target_path, ec);
if (ec)
@ -216,23 +253,9 @@ namespace nsproc {
})
// Mount different things required by gui apps
.ifthen(conf.gui_mounts,
ko::ns::mount::mount_gui, conf.root_path, conf.home_path.relative_path(), ko::util::str("run/user/", conf.uid))
// Add a dummy user to /etc/passwd
.then("bind_passwd", [&conf]() {
auto etc_passwd = conf.root_path / "etc/passwd";
auto tmp_passwd = conf.root_path / "tmp/passwd";
if (fs::exists(etc_passwd)) {
fs::copy(etc_passwd, tmp_passwd);
auto s = std::fstream(tmp_passwd, std::fstream::out | std::fstream::app);
s << std::endl << STEAM_USER << ":x:" << conf.uid << ":" << conf.gid << ":Steam Container User:" << conf.home_path.native() << ":/bin/bash" << std::endl;
s.close();
return ko::os::bind(tmp_passwd, etc_passwd);
}
return 0;
})
ko::ns::mount::mount_gui, root, conf.home_path.relative_path(), ko::util::str("run/user/", conf.uid))
// Finally, pivot_root
.then(ko::ns::mount::pivot_root, conf.root_path, "mnt", conf.keep_root);
.then(ko::ns::mount::pivot_root, root, "mnt", conf.keep_root);
if (err) {
if (report) report->post(1);
@ -299,6 +322,7 @@ void usage(const char *prog) {
<< std::endl
<< "Namespace Creation Options:" << std::endl
<< " -r Run in fakeroot mode (implies -W)" << std::endl
<< " -H Use host rootfs (only mount steamns home" << std::endl
<< " -p <path> Use custom root path" << std::endl
<< " -M Don't set up mouts (implies -G)" << std::endl
<< " -G Don't set up GUI-related mounts" << std::endl
@ -312,7 +336,7 @@ void usage(const char *prog) {
struct config {
fs::path root_path;
const char *const *exec_argv = DEFAULT_CMD;
const char *const *exec_argv = DEFAULT_CMD.data();
bool fakeroot = false,
mounts = true,
gui_mounts = true,
@ -321,7 +345,8 @@ struct config {
dummy_mode = false,
pid_ns = true,
ns_create = false,
system_ro = true;
system_ro = true,
use_host_root = false;
std::optional<fs::path> ns_path,
ns_setup_exec;
};
@ -329,9 +354,8 @@ struct config {
// Parse commandline arguments
// returns -1 on success, exit code otherwise
int parse_cmdline(config &conf, int argc, const char *const *argv) {
constexpr auto spec = "+hp:rkwWMGe:c:j:D";
constexpr auto spec = "+hp:rHkwWMGe:c:j:D";
bool custom_root_path = false;
std::optional<fs::path> create_path, join_path;
while (true) {
@ -348,10 +372,8 @@ int parse_cmdline(config &conf, int argc, const char *const *argv) {
conf.fakeroot = true;
conf.system_ro = false;
}
else if (opt == 'p') {
else if (opt == 'p')
conf.root_path = ::optarg;
custom_root_path = true;
}
else if (opt == 'M')
conf.mounts = false;
else if (opt == 'G')
@ -370,6 +392,8 @@ int parse_cmdline(config &conf, int argc, const char *const *argv) {
join_path = ::optarg;
else if (opt == 'D')
conf.dummy_mode = true;
else if (opt == 'H')
conf.use_host_root = true;
}
// Check sanity
@ -381,7 +405,7 @@ int parse_cmdline(config &conf, int argc, const char *const *argv) {
}
// NOTE: let -p slip by to facilitate '-p<path> -j-' use-case
if (!conf.dummy_mode && (!conf.mounts || !conf.gui_mounts || conf.keep_root)) {
if (!conf.dummy_mode && (!conf.mounts || !conf.gui_mounts || conf.keep_root || conf.use_host_root)) {
std::cerr << "Error: -j cannot be combined with any namespace setup options (-MGk) unless -D is given" << std::endl;
good = false;
}
@ -399,6 +423,10 @@ int parse_cmdline(config &conf, int argc, const char *const *argv) {
std::cerr << "Error: -r cannot be combined with -c or -j" << std::endl;
good = false;
}
if (conf.use_host_root) {
std::cerr << "Error: -H cannot be combined with -c or -j" << std::endl;
good = false;
}
// - Special default in -j and -c
if (*conf.ns_path == "-")
@ -533,8 +561,9 @@ int main(int argc, char **argv) {
.keep_root = conf.keep_root,
.dummy_mode = conf.dummy_mode,
.pid_ns = conf.pid_ns,
.use_host_root = conf.use_host_root,
.setup_exec = conf.ns_setup_exec,
.ns_path_fd = ns_path_fd
.ns_path_fd = ns_path_fd,
};
constexpr auto stacksize = 1024*1024;

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