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/*
* Copyright (C) The c-ares project
*
* Permission to use, copy, modify, and distribute this
* software and its documentation for any purpose and without
* fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright
* notice and this permission notice appear in supporting
* documentation, and that the name of M.I.T. not be used in
* advertising or publicity pertaining to distribution of the
* software without specific, written prior permission.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is"
* without express or implied warranty.
*
* SPDX-License-Identifier: MIT
*/
#include "ares-test.h"
#ifdef HAVE_CONTAINER
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <iostream>
#include <functional>
#include <string>
#include <sstream>
#include <vector>
namespace ares {
namespace test {
namespace {
struct ContainerInfo {
ContainerFilesystem* fs_;
std::string hostname_;
std::string domainname_;
VoidToIntFn fn_;
};
int EnterContainer(void *data) {
ContainerInfo *container = (ContainerInfo*)data;
if (verbose) {
std::cerr << "Running function in container {chroot='"
<< container->fs_->root() << "', hostname='" << container->hostname_
<< "', domainname='" << container->domainname_ << "'}"
<< std::endl;
}
// Ensure we are apparently root before continuing.
int count = 10;
while (getuid() != 0 && count > 0) {
usleep(100000);
count--;
}
if (getuid() != 0) {
std::cerr << "Child in user namespace has uid " << getuid() << std::endl;
return -1;
}
if (!container->fs_->mountpt().empty()) {
// We want to bind mount this inside the specified directory.
std::string innerdir = container->fs_->root() + container->fs_->mountpt();
if (verbose) std::cerr << " mount --bind " << container->fs_->mountpt()
<< " " << innerdir << std::endl;
int rc = mount(container->fs_->mountpt().c_str(), innerdir.c_str(),
"none", MS_BIND, 0);
if (rc != 0) {
std::cerr << "Warning: failed to bind mount " << container->fs_->mountpt() << " at "
<< innerdir << ", errno=" << errno << std::endl;
}
}
// Move into the specified directory.
if (chdir(container->fs_->root().c_str()) != 0) {
std::cerr << "Failed to chdir('" << container->fs_->root()
<< "'), errno=" << errno << std::endl;
return -1;
}
// And make it the new root directory;
char buffer[PATH_MAX + 1];
if (getcwd(buffer, PATH_MAX) == NULL) {
std::cerr << "failed to retrieve cwd, errno=" << errno << std::endl;
return -1;
}
buffer[PATH_MAX] = '\0';
if (chroot(buffer) != 0) {
std::cerr << "chroot('" << buffer << "') failed, errno=" << errno << std::endl;
return -1;
}
// Set host/domainnames if specified
if (!container->hostname_.empty()) {
if (sethostname(container->hostname_.c_str(),
container->hostname_.size()) != 0) {
std::cerr << "Failed to sethostname('" << container->hostname_
<< "'), errno=" << errno << std::endl;
return -1;
}
}
if (!container->domainname_.empty()) {
if (setdomainname(container->domainname_.c_str(),
container->domainname_.size()) != 0) {
std::cerr << "Failed to setdomainname('" << container->domainname_
<< "'), errno=" << errno << std::endl;
return -1;
}
}
return container->fn_();
}
} // namespace
// Run a function while:
// - chroot()ed into a particular directory
// - having a specified hostname/domainname
int RunInContainer(ContainerFilesystem* fs, const std::string& hostname,
const std::string& domainname, VoidToIntFn fn) {
const int stack_size = 1024 * 1024;
std::vector<byte> stack(stack_size, 0);
ContainerInfo container = {fs, hostname, domainname, fn};
// Start a child process in a new user and UTS namespace
pid_t child = clone(EnterContainer, stack.data() + stack_size,
CLONE_VM|CLONE_NEWNS|CLONE_NEWUSER|CLONE_NEWUTS|SIGCHLD,
(void *)&container);
if (child < 0) {
std::cerr << "Failed to clone(), errno=" << errno << std::endl;
return -1;
}
// Build the UID map that makes us look like root inside the namespace.
std::stringstream mapfiless;
mapfiless << "/proc/" << child << "/uid_map";
std::string mapfile = mapfiless.str();
int fd = open(mapfile.c_str(), O_CREAT|O_WRONLY|O_TRUNC, 0644);
if (fd < 0) {
std::cerr << "Failed to create '" << mapfile << "'" << std::endl;
return -1;
}
std::stringstream contentss;
contentss << "0 " << getuid() << " 1" << std::endl;
std::string content = contentss.str();
int rc = write(fd, content.c_str(), content.size());
if (rc != (int)content.size()) {
std::cerr << "Failed to write uid map to '" << mapfile << "'" << std::endl;
}
close(fd);
// Wait for the child process and retrieve its status.
int status;
waitpid(child, &status, 0);
if (rc <= 0) {
std::cerr << "Failed to waitpid(" << child << ")" << std::endl;
return -1;
}
if (!WIFEXITED(status)) {
std::cerr << "Child " << child << " did not exit normally" << std::endl;
return -1;
}
return status;
}
ContainerFilesystem::ContainerFilesystem(NameContentList files, const std::string& mountpt) {
rootdir_ = TempNam(nullptr, "ares-chroot");
mkdir(rootdir_.c_str(), 0755);
dirs_.push_front(rootdir_);
for (const auto& nc : files) {
std::string fullpath = rootdir_ + nc.first;
int idx = fullpath.rfind('/');
std::string dir = fullpath.substr(0, idx);
EnsureDirExists(dir);
files_.push_back(std::unique_ptr<TransientFile>(
new TransientFile(fullpath, nc.second)));
}
if (!mountpt.empty()) {
char buffer[PATH_MAX + 1];
if (realpath(mountpt.c_str(), buffer)) {
mountpt_ = buffer;
std::string fullpath = rootdir_ + mountpt_;
EnsureDirExists(fullpath);
}
}
}
ContainerFilesystem::~ContainerFilesystem() {
files_.clear();
for (const std::string& dir : dirs_) {
rmdir(dir.c_str());
}
}
void ContainerFilesystem::EnsureDirExists(const std::string& dir) {
if (std::find(dirs_.begin(), dirs_.end(), dir) != dirs_.end()) {
return;
}
size_t idx = dir.rfind('/');
if (idx != std::string::npos) {
std::string prevdir = dir.substr(0, idx);
EnsureDirExists(prevdir);
}
// Ensure this directory is in the list before its ancestors.
mkdir(dir.c_str(), 0755);
dirs_.push_front(dir);
}
} // namespace test
} // namespace ares
#endif
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