lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame] | 1 | #include "ares-test.h" |
| 2 | |
| 3 | #ifdef HAVE_CONTAINER |
| 4 | |
| 5 | #include <sys/mount.h> |
| 6 | #include <sys/types.h> |
| 7 | #include <sys/stat.h> |
| 8 | #include <fcntl.h> |
| 9 | |
| 10 | #include <iostream> |
| 11 | #include <functional> |
| 12 | #include <string> |
| 13 | #include <sstream> |
| 14 | #include <vector> |
| 15 | |
| 16 | namespace ares { |
| 17 | namespace test { |
| 18 | |
| 19 | namespace { |
| 20 | |
| 21 | struct ContainerInfo { |
| 22 | ContainerFilesystem* fs_; |
| 23 | std::string hostname_; |
| 24 | std::string domainname_; |
| 25 | VoidToIntFn fn_; |
| 26 | }; |
| 27 | |
| 28 | int EnterContainer(void *data) { |
| 29 | ContainerInfo *container = (ContainerInfo*)data; |
| 30 | |
| 31 | if (verbose) { |
| 32 | std::cerr << "Running function in container {chroot='" |
| 33 | << container->fs_->root() << "', hostname='" << container->hostname_ |
| 34 | << "', domainname='" << container->domainname_ << "'}" |
| 35 | << std::endl; |
| 36 | } |
| 37 | |
| 38 | // Ensure we are apparently root before continuing. |
| 39 | int count = 10; |
| 40 | while (getuid() != 0 && count > 0) { |
| 41 | usleep(100000); |
| 42 | count--; |
| 43 | } |
| 44 | if (getuid() != 0) { |
| 45 | std::cerr << "Child in user namespace has uid " << getuid() << std::endl; |
| 46 | return -1; |
| 47 | } |
| 48 | if (!container->fs_->mountpt().empty()) { |
| 49 | // We want to bind mount this inside the specified directory. |
| 50 | std::string innerdir = container->fs_->root() + container->fs_->mountpt(); |
| 51 | if (verbose) std::cerr << " mount --bind " << container->fs_->mountpt() |
| 52 | << " " << innerdir << std::endl; |
| 53 | int rc = mount(container->fs_->mountpt().c_str(), innerdir.c_str(), |
| 54 | "none", MS_BIND, 0); |
| 55 | if (rc != 0) { |
| 56 | std::cerr << "Warning: failed to bind mount " << container->fs_->mountpt() << " at " |
| 57 | << innerdir << ", errno=" << errno << std::endl; |
| 58 | } |
| 59 | } |
| 60 | |
| 61 | // Move into the specified directory. |
| 62 | if (chdir(container->fs_->root().c_str()) != 0) { |
| 63 | std::cerr << "Failed to chdir('" << container->fs_->root() |
| 64 | << "'), errno=" << errno << std::endl; |
| 65 | return -1; |
| 66 | } |
| 67 | // And make it the new root directory; |
| 68 | char buffer[PATH_MAX + 1]; |
| 69 | if (getcwd(buffer, PATH_MAX) == NULL) { |
| 70 | std::cerr << "failed to retrieve cwd, errno=" << errno << std::endl; |
| 71 | return -1; |
| 72 | } |
| 73 | buffer[PATH_MAX] = '\0'; |
| 74 | if (chroot(buffer) != 0) { |
| 75 | std::cerr << "chroot('" << buffer << "') failed, errno=" << errno << std::endl; |
| 76 | return -1; |
| 77 | } |
| 78 | |
| 79 | // Set host/domainnames if specified |
| 80 | if (!container->hostname_.empty()) { |
| 81 | if (sethostname(container->hostname_.c_str(), |
| 82 | container->hostname_.size()) != 0) { |
| 83 | std::cerr << "Failed to sethostname('" << container->hostname_ |
| 84 | << "'), errno=" << errno << std::endl; |
| 85 | return -1; |
| 86 | } |
| 87 | } |
| 88 | if (!container->domainname_.empty()) { |
| 89 | if (setdomainname(container->domainname_.c_str(), |
| 90 | container->domainname_.size()) != 0) { |
| 91 | std::cerr << "Failed to setdomainname('" << container->domainname_ |
| 92 | << "'), errno=" << errno << std::endl; |
| 93 | return -1; |
| 94 | } |
| 95 | } |
| 96 | |
| 97 | return container->fn_(); |
| 98 | } |
| 99 | |
| 100 | } // namespace |
| 101 | |
| 102 | // Run a function while: |
| 103 | // - chroot()ed into a particular directory |
| 104 | // - having a specified hostname/domainname |
| 105 | |
| 106 | int RunInContainer(ContainerFilesystem* fs, const std::string& hostname, |
| 107 | const std::string& domainname, VoidToIntFn fn) { |
| 108 | const int stack_size = 1024 * 1024; |
| 109 | std::vector<byte> stack(stack_size, 0); |
| 110 | ContainerInfo container = {fs, hostname, domainname, fn}; |
| 111 | |
| 112 | // Start a child process in a new user and UTS namespace |
| 113 | pid_t child = clone(EnterContainer, stack.data() + stack_size, |
| 114 | CLONE_VM|CLONE_NEWNS|CLONE_NEWUSER|CLONE_NEWUTS|SIGCHLD, |
| 115 | (void *)&container); |
| 116 | if (child < 0) { |
| 117 | std::cerr << "Failed to clone(), errno=" << errno << std::endl; |
| 118 | return -1; |
| 119 | } |
| 120 | |
| 121 | // Build the UID map that makes us look like root inside the namespace. |
| 122 | std::stringstream mapfiless; |
| 123 | mapfiless << "/proc/" << child << "/uid_map"; |
| 124 | std::string mapfile = mapfiless.str(); |
| 125 | int fd = open(mapfile.c_str(), O_CREAT|O_WRONLY|O_TRUNC, 0644); |
| 126 | if (fd < 0) { |
| 127 | std::cerr << "Failed to create '" << mapfile << "'" << std::endl; |
| 128 | return -1; |
| 129 | } |
| 130 | std::stringstream contentss; |
| 131 | contentss << "0 " << getuid() << " 1" << std::endl; |
| 132 | std::string content = contentss.str(); |
| 133 | int rc = write(fd, content.c_str(), content.size()); |
| 134 | if (rc != (int)content.size()) { |
| 135 | std::cerr << "Failed to write uid map to '" << mapfile << "'" << std::endl; |
| 136 | } |
| 137 | close(fd); |
| 138 | |
| 139 | // Wait for the child process and retrieve its status. |
| 140 | int status; |
| 141 | waitpid(child, &status, 0); |
| 142 | if (rc <= 0) { |
| 143 | std::cerr << "Failed to waitpid(" << child << ")" << std::endl; |
| 144 | return -1; |
| 145 | } |
| 146 | if (!WIFEXITED(status)) { |
| 147 | std::cerr << "Child " << child << " did not exit normally" << std::endl; |
| 148 | return -1; |
| 149 | } |
| 150 | return status; |
| 151 | } |
| 152 | |
| 153 | ContainerFilesystem::ContainerFilesystem(NameContentList files, const std::string& mountpt) { |
| 154 | rootdir_ = TempNam(nullptr, "ares-chroot"); |
| 155 | mkdir(rootdir_.c_str(), 0755); |
| 156 | dirs_.push_front(rootdir_); |
| 157 | for (const auto& nc : files) { |
| 158 | std::string fullpath = rootdir_ + nc.first; |
| 159 | int idx = fullpath.rfind('/'); |
| 160 | std::string dir = fullpath.substr(0, idx); |
| 161 | EnsureDirExists(dir); |
| 162 | files_.push_back(std::unique_ptr<TransientFile>( |
| 163 | new TransientFile(fullpath, nc.second))); |
| 164 | } |
| 165 | if (!mountpt.empty()) { |
| 166 | char buffer[PATH_MAX + 1]; |
| 167 | if (realpath(mountpt.c_str(), buffer)) { |
| 168 | mountpt_ = buffer; |
| 169 | std::string fullpath = rootdir_ + mountpt_; |
| 170 | EnsureDirExists(fullpath); |
| 171 | } |
| 172 | } |
| 173 | } |
| 174 | |
| 175 | ContainerFilesystem::~ContainerFilesystem() { |
| 176 | files_.clear(); |
| 177 | for (const std::string& dir : dirs_) { |
| 178 | rmdir(dir.c_str()); |
| 179 | } |
| 180 | } |
| 181 | |
| 182 | void ContainerFilesystem::EnsureDirExists(const std::string& dir) { |
| 183 | if (std::find(dirs_.begin(), dirs_.end(), dir) != dirs_.end()) { |
| 184 | return; |
| 185 | } |
| 186 | size_t idx = dir.rfind('/'); |
| 187 | if (idx != std::string::npos) { |
| 188 | std::string prevdir = dir.substr(0, idx); |
| 189 | EnsureDirExists(prevdir); |
| 190 | } |
| 191 | // Ensure this directory is in the list before its ancestors. |
| 192 | mkdir(dir.c_str(), 0755); |
| 193 | dirs_.push_front(dir); |
| 194 | } |
| 195 | |
| 196 | } // namespace test |
| 197 | } // namespace ares |
| 198 | |
| 199 | #endif |