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Diffstat (limited to '')
| -rw-r--r-- | src/c-ares/test/ares-test-ns.cc | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/src/c-ares/test/ares-test-ns.cc b/src/c-ares/test/ares-test-ns.cc new file mode 100644 index 00000000..c3c45521 --- /dev/null +++ b/src/c-ares/test/ares-test-ns.cc @@ -0,0 +1,199 @@ +#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 |