systemd/src/import/import-common.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <sched.h>
#include <sys/prctl.h>
#include <sys/stat.h>
#include <unistd.h>

#include "alloc-util.h"
#include "btrfs-util.h"
#include "capability-util.h"
#include "chattr-util.h"
#include "dirent-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hostname-util.h"
#include "import-common.h"
#include "os-util.h"
#include "process-util.h"
#include "selinux-util.h"
#include "signal-util.h"
#include "stat-util.h"
#include "tmpfile-util.h"

int import_fork_tar_x(const char *path, pid_t *ret) {
        _cleanup_close_pair_ int pipefd[2] = PIPE_EBADF;
        bool use_selinux;
        pid_t pid;
        int r;

        assert(path);
        assert(ret);

        if (pipe2(pipefd, O_CLOEXEC) < 0)
                return log_error_errno(errno, "Failed to create pipe for tar: %m");

        use_selinux = mac_selinux_use();

        r = safe_fork_full("(tar)",
                           (int[]) { pipefd[0], -EBADF, STDERR_FILENO },
                           NULL, 0,
                           FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_DEATHSIG|FORK_REARRANGE_STDIO|FORK_LOG, &pid);
        if (r < 0)
                return r;
        if (r == 0) {
                const char *cmdline[] = {
                       "tar",
                       "--ignore-zeros",
                       "--numeric-owner",
                       "-C", path,
                       "-pxf",
                       "-",
                       "--xattrs",
                       "--xattrs-include=*",
                       use_selinux ? "--selinux" : "--no-selinux",
                       NULL
                };

                uint64_t retain =
                        (1ULL << CAP_CHOWN) |
                        (1ULL << CAP_FOWNER) |
                        (1ULL << CAP_FSETID) |
                        (1ULL << CAP_MKNOD) |
                        (1ULL << CAP_SETFCAP) |
                        (1ULL << CAP_DAC_OVERRIDE);

                /* Child */

                if (unshare(CLONE_NEWNET) < 0)
                        log_warning_errno(errno, "Failed to lock tar into network namespace, ignoring: %m");

                r = capability_bounding_set_drop(retain, true);
                if (r < 0)
                        log_warning_errno(r, "Failed to drop capabilities, ignoring: %m");

                /* Try "gtar" before "tar". We only test things upstream with GNU tar. Some distros appear to
                 * install a different implementation as "tar" (in particular some that do not support the
                 * same command line switches), but then provide "gtar" as alias for the real thing, hence
                 * let's prefer that. (Yes, it's a bad idea they do that, given they don't provide equivalent
                 * command line support, but we are not here to argue, let's just expose the same
                 * behaviour/implementation everywhere.) */
                execvp("gtar", (char* const*) cmdline);
                execvp("tar", (char* const*) cmdline);

                log_error_errno(errno, "Failed to execute tar: %m");
                _exit(EXIT_FAILURE);
        }

        *ret = pid;

        return TAKE_FD(pipefd[1]);
}

int import_fork_tar_c(const char *path, pid_t *ret) {
        _cleanup_close_pair_ int pipefd[2] = PIPE_EBADF;
        bool use_selinux;
        pid_t pid;
        int r;

        assert(path);
        assert(ret);

        if (pipe2(pipefd, O_CLOEXEC) < 0)
                return log_error_errno(errno, "Failed to create pipe for tar: %m");

        use_selinux = mac_selinux_use();

        r = safe_fork_full("(tar)",
                           (int[]) { -EBADF, pipefd[1], STDERR_FILENO },
                           NULL, 0,
                           FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_DEATHSIG|FORK_REARRANGE_STDIO|FORK_LOG, &pid);
        if (r < 0)
                return r;
        if (r == 0) {
                const char *cmdline[] = {
                        "tar",
                        "-C", path,
                        "-c",
                        "--xattrs",
                        "--xattrs-include=*",
                       use_selinux ? "--selinux" : "--no-selinux",
                        ".",
                        NULL
                };

                uint64_t retain = (1ULL << CAP_DAC_OVERRIDE);

                /* Child */

                if (unshare(CLONE_NEWNET) < 0)
                        log_error_errno(errno, "Failed to lock tar into network namespace, ignoring: %m");

                r = capability_bounding_set_drop(retain, true);
                if (r < 0)
                        log_error_errno(r, "Failed to drop capabilities, ignoring: %m");

                execvp("gtar", (char* const*) cmdline);
                execvp("tar", (char* const*) cmdline);

                log_error_errno(errno, "Failed to execute tar: %m");
                _exit(EXIT_FAILURE);
        }

        *ret = pid;

        return TAKE_FD(pipefd[0]);
}

int import_mangle_os_tree(const char *path) {
        _cleanup_free_ char *child = NULL, *t = NULL, *joined = NULL;
        _cleanup_closedir_ DIR *d = NULL, *cd = NULL;
        struct dirent *dent;
        struct stat st;
        int r;

        assert(path);

        /* Some tarballs contain a single top-level directory that contains the actual OS directory tree. Try to
         * recognize this, and move the tree one level up. */

        r = path_is_os_tree(path);
        if (r < 0)
                return log_error_errno(r, "Failed to determine whether '%s' is an OS tree: %m", path);
        if (r > 0) {
                log_debug("Directory tree '%s' is a valid OS tree.", path);
                return 0;
        }

        log_debug("Directory tree '%s' is not recognizable as OS tree, checking whether to rearrange it.", path);

        d = opendir(path);
        if (!d)
                return log_error_errno(r, "Failed to open directory '%s': %m", path);

        errno = 0;
        dent = readdir_no_dot(d);
        if (!dent) {
                if (errno != 0)
                        return log_error_errno(errno, "Failed to iterate through directory '%s': %m", path);

                log_debug("Directory '%s' is empty, leaving it as it is.", path);
                return 0;
        }

        child = strdup(dent->d_name);
        if (!child)
                return log_oom();

        errno = 0;
        dent = readdir_no_dot(d);
        if (dent) {
                if (errno != 0)
                        return log_error_errno(errno, "Failed to iterate through directory '%s': %m", path);

                log_debug("Directory '%s' does not look like an OS tree, and has multiple children, leaving as it is.", path);
                return 0;
        }

        if (fstatat(dirfd(d), child, &st, AT_SYMLINK_NOFOLLOW) < 0)
                return log_debug_errno(errno, "Failed to stat file '%s/%s': %m", path, child);
        r = stat_verify_directory(&st);
        if (r < 0) {
                log_debug_errno(r, "Child '%s' of directory '%s' is not a directory, leaving things as they are.", child, path);
                return 0;
        }

        joined = path_join(path, child);
        if (!joined)
                return log_oom();
        r = path_is_os_tree(joined);
        if (r == -ENOTDIR) {
                log_debug("Directory '%s' does not look like an OS tree, and contains a single regular file only, leaving as it is.", path);
                return 0;
        }
        if (r < 0)
                return log_error_errno(r, "Failed to determine whether '%s' is an OS tree: %m", joined);
        if (r == 0) {
                log_debug("Neither '%s' nor '%s' is a valid OS tree, leaving them as they are.", path, joined);
                return 0;
        }

        /* Nice, we have checked now:
         *
         * 1. The top-level directory does not qualify as OS tree
         * 1. The top-level directory only contains one item
         * 2. That item is a directory
         * 3. And that directory qualifies as OS tree
         *
         * Let's now rearrange things, moving everything in the inner directory one level up */

        cd = xopendirat(dirfd(d), child, O_NOFOLLOW);
        if (!cd)
                return log_error_errno(errno, "Can't open directory '%s': %m", joined);

        log_info("Rearranging '%s', moving OS tree one directory up.", joined);

        /* Let's rename the child to an unguessable name so that we can be sure all files contained in it can be
         * safely moved up and won't collide with the name. */
        r = tempfn_random(child, NULL, &t);
        if (r < 0)
                return log_oom();
        r = rename_noreplace(dirfd(d), child, dirfd(d), t);
        if (r < 0)
                return log_error_errno(r, "Unable to rename '%s' to '%s/%s': %m", joined, path, t);

        FOREACH_DIRENT_ALL(de, cd, return log_error_errno(errno, "Failed to iterate through directory '%s': %m", joined)) {
                if (dot_or_dot_dot(de->d_name))
                        continue;

                r = rename_noreplace(dirfd(cd), de->d_name, dirfd(d), de->d_name);
                if (r < 0)
                        return log_error_errno(r, "Unable to move '%s/%s/%s' to '%s/%s': %m", path, t, de->d_name, path, de->d_name);
        }

        if (unlinkat(dirfd(d), t, AT_REMOVEDIR) < 0)
                return log_error_errno(errno, "Failed to remove temporary directory '%s/%s': %m", path, t);

        r = futimens(dirfd(d), (struct timespec[2]) { st.st_atim, st.st_mtim });
        if (r < 0)
                log_debug_errno(r, "Failed to adjust top-level timestamps '%s', ignoring: %m", path);

        r = fchmod_and_chown(dirfd(d), st.st_mode, st.st_uid, st.st_gid);
        if (r < 0)
                return log_error_errno(r, "Failed to adjust top-level directory mode/ownership '%s': %m", path);

        log_info("Successfully rearranged OS tree.");

        return 0;
}

bool import_validate_local(const char *name, ImportFlags flags) {

        /* By default we insist on a valid hostname for naming images. But optionally we relax that, in which
         * case it can be any path name */

        if (FLAGS_SET(flags, IMPORT_DIRECT))
                return path_is_valid(name);

        return hostname_is_valid(name, 0);
}

static int interrupt_signal_handler(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) {
        log_notice("Transfer aborted.");
        sd_event_exit(sd_event_source_get_event(s), EINTR);
        return 0;
}

int import_allocate_event_with_signals(sd_event **ret) {
        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
        int r;

        assert(ret);

        r = sd_event_default(&event);
        if (r < 0)
                return log_error_errno(r, "Failed to allocate event loop: %m");

        assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
        (void) sd_event_add_signal(event, NULL, SIGTERM, interrupt_signal_handler,  NULL);
        (void) sd_event_add_signal(event, NULL, SIGINT, interrupt_signal_handler, NULL);

        *ret = TAKE_PTR(event);
        return 0;
}