chiark / gitweb /
core: always create /dev/kdbus/ns (and make it private 0700) after setting up the...
[elogind.git] / src / core / namespace.c
index da555cd..85147be 100644 (file)
 #include <sys/syscall.h>
 #include <limits.h>
 #include <linux/fs.h>
+#include <sys/file.h>
 
 #include "strv.h"
 #include "util.h"
+#include "path-util.h"
 #include "namespace.h"
 #include "missing.h"
+#include "execute.h"
+#include "loopback-setup.h"
 
-typedef enum PathMode {
+typedef enum MountMode {
         /* This is ordered by priority! */
         INACCESSIBLE,
         READONLY,
-        PRIVATE,
+        PRIVATE_TMP,
+        PRIVATE_VAR_TMP,
         READWRITE
-} PathMode;
+} MountMode;
 
-typedef struct Path {
+typedef struct BindMount {
         const char *path;
-        PathMode mode;
-} Path;
+        MountMode mode;
+        bool done;
+        bool ignore;
+} BindMount;
 
-static int append_paths(Path **p, char **strv, PathMode mode) {
+static int append_mounts(BindMount **p, char **strv, MountMode mode) {
         char **i;
 
+        assert(p);
+
         STRV_FOREACH(i, strv) {
 
+                (*p)->ignore = false;
+
+                if ((mode == INACCESSIBLE || mode == READONLY) && (*i)[0] == '-') {
+                        (*p)->ignore = true;
+                        (*i)++;
+                }
+
                 if (!path_is_absolute(*i))
                         return -EINVAL;
 
@@ -65,8 +81,8 @@ static int append_paths(Path **p, char **strv, PathMode mode) {
         return 0;
 }
 
-static int path_compare(const void *a, const void *b) {
-        const Path *p = a, *q = b;
+static int mount_path_compare(const void *a, const void *b) {
+        const BindMount *p = a, *q = b;
 
         if (path_equal(p->path, q->path)) {
 
@@ -90,257 +106,328 @@ static int path_compare(const void *a, const void *b) {
         return 0;
 }
 
-static void drop_duplicates(Path *p, unsigned *n, bool *need_inaccessible, bool *need_private) {
-        Path *f, *t, *previous;
+static void drop_duplicates(BindMount *m, unsigned *n) {
+        BindMount *f, *t, *previous;
 
-        assert(p);
+        assert(m);
         assert(n);
-        assert(need_inaccessible);
-        assert(need_private);
 
-        for (f = p, t = p, previous = NULL; f < p+*n; f++) {
+        for (f = m, t = m, previous = NULL; f < m+*n; f++) {
 
+                /* The first one wins */
                 if (previous && path_equal(f->path, previous->path))
                         continue;
 
                 t->path = f->path;
                 t->mode = f->mode;
 
-                if (t->mode == PRIVATE)
-                        *need_private = true;
-
-                if (t->mode == INACCESSIBLE)
-                        *need_inaccessible = true;
-
                 previous = t;
 
                 t++;
         }
 
-        *n = t - p;
+        *n = t - m;
 }
 
-static int apply_mount(Path *p, const char *root_dir, const char *inaccessible_dir, const char *private_dir, unsigned long flags) {
+static int apply_mount(
+                BindMount *m,
+                const char *tmp_dir,
+                const char *var_tmp_dir) {
+
         const char *what;
-        char *where;
         int r;
 
-        assert(p);
-        assert(root_dir);
-        assert(inaccessible_dir);
-        assert(private_dir);
+        assert(m);
 
-        if (!(where = strappend(root_dir, p->path)))
-                return -ENOMEM;
-
-        switch (p->mode) {
+        switch (m->mode) {
 
         case INACCESSIBLE:
-                what = inaccessible_dir;
-                flags |= MS_RDONLY;
+                what = "/run/systemd/inaccessible";
                 break;
 
         case READONLY:
-                flags |= MS_RDONLY;
-                /* Fall through */
-
         case READWRITE:
-                what = p->path;
+                what = m->path;
+                break;
+
+        case PRIVATE_TMP:
+                what = tmp_dir;
                 break;
 
-        case PRIVATE:
-                what = private_dir;
+        case PRIVATE_VAR_TMP:
+                what = var_tmp_dir;
                 break;
 
         default:
                 assert_not_reached("Unknown mode");
         }
 
-        if ((r = mount(what, where, NULL, MS_BIND|MS_REC, NULL)) >= 0) {
-                log_debug("Successfully mounted %s to %s", what, where);
+        assert(what);
 
-                /* The bind mount will always inherit the original
-                 * flags. If we want to set any flag we need
-                 * to do so in a second independent step. */
-                if (flags)
-                        r = mount(NULL, where, NULL, MS_REMOUNT|MS_BIND|MS_REC|flags, NULL);
+        r = mount(what, m->path, NULL, MS_BIND|MS_REC, NULL);
+        if (r >= 0)
+                log_debug("Successfully mounted %s to %s", what, m->path);
+        else if (m->ignore && errno == ENOENT)
+                r = 0;
 
-                /* Avoid exponential growth of trees */
-                if (r >= 0 && path_equal(p->path, "/"))
-                        r = mount(NULL, where, NULL, MS_REMOUNT|MS_BIND|MS_UNBINDABLE|flags, NULL);
+        return r;
+}
 
-                if (r < 0) {
-                        r = -errno;
-                        umount2(where, MNT_DETACH);
-                }
-        }
+static int make_read_only(BindMount *m) {
+        int r;
 
-        free(where);
-        return r;
+        assert(m);
+
+        if (m->mode != INACCESSIBLE && m->mode != READONLY)
+                return 0;
+
+        r = mount(NULL, m->path, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY|MS_REC, NULL);
+        if (r < 0 && !(m->ignore && errno == ENOENT))
+                return -errno;
+
+        return 0;
 }
 
 int setup_namespace(
-                char **writable,
-                char **readable,
-                char **inaccessible,
-                bool private_tmp,
-                unsigned long flags) {
-
-        char
-                tmp_dir[] = "/tmp/systemd-namespace-XXXXXX",
-                root_dir[] = "/tmp/systemd-namespace-XXXXXX/root",
-                old_root_dir[] = "/tmp/systemd-namespace-XXXXXX/root/tmp/old-root-XXXXXX",
-                inaccessible_dir[] = "/tmp/systemd-namespace-XXXXXX/inaccessible",
-                private_dir[] = "/tmp/systemd-namespace-XXXXXX/private";
-
-        Path *paths, *p;
+                char** read_write_dirs,
+                char** read_only_dirs,
+                char** inaccessible_dirs,
+                char* tmp_dir,
+                char* var_tmp_dir,
+                unsigned mount_flags) {
+
+        BindMount *m, *mounts = NULL;
         unsigned n;
-        bool need_private = false, need_inaccessible = false;
-        bool remove_tmp = false, remove_root = false, remove_old_root = false, remove_inaccessible = false, remove_private = false;
-        int r;
-        const char *t;
+        int r = 0;
 
-        n =
-                strv_length(writable) +
-                strv_length(readable) +
-                strv_length(inaccessible) +
-                (private_tmp ? 2 : 1);
+        if (mount_flags == 0)
+                mount_flags = MS_SHARED;
 
-        if (!(paths = new(Path, n)))
-                return -ENOMEM;
+        if (unshare(CLONE_NEWNS) < 0)
+                return -errno;
 
-        p = paths;
-        if ((r = append_paths(&p, writable, READWRITE)) < 0 ||
-            (r = append_paths(&p, readable, READONLY)) < 0 ||
-            (r = append_paths(&p, inaccessible, INACCESSIBLE)) < 0)
-                goto fail;
+        n = !!tmp_dir + !!var_tmp_dir +
+                strv_length(read_write_dirs) +
+                strv_length(read_only_dirs) +
+                strv_length(inaccessible_dirs);
+
+        if (n > 0) {
+                m = mounts = (BindMount *) alloca(n * sizeof(BindMount));
+                r = append_mounts(&m, read_write_dirs, READWRITE);
+                if (r < 0)
+                        return r;
+
+                r = append_mounts(&m, read_only_dirs, READONLY);
+                if (r < 0)
+                        return r;
+
+                r = append_mounts(&m, inaccessible_dirs, INACCESSIBLE);
+                if (r < 0)
+                        return r;
+
+                if (tmp_dir) {
+                        m->path = "/tmp";
+                        m->mode = PRIVATE_TMP;
+                        m++;
+                }
 
-        if (private_tmp) {
-                p->path = "/tmp";
-                p->mode = PRIVATE;
-                p++;
-        }
+                if (var_tmp_dir) {
+                        m->path = "/var/tmp";
+                        m->mode = PRIVATE_VAR_TMP;
+                        m++;
+                }
 
-        p->path = "/";
-        p->mode = READWRITE;
-        p++;
+                assert(mounts + n == m);
 
-        assert(paths + n == p);
+                qsort(mounts, n, sizeof(BindMount), mount_path_compare);
+                drop_duplicates(mounts, &n);
+        }
 
-        qsort(paths, n, sizeof(Path), path_compare);
-        drop_duplicates(paths, &n, &need_inaccessible, &need_private);
+        /* Remount / as SLAVE so that nothing now mounted in the namespace
+           shows up in the parent */
+        if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0)
+                return -errno;
 
-        if (!mkdtemp(tmp_dir)) {
-                r = -errno;
-                goto fail;
+        for (m = mounts; m < mounts + n; ++m) {
+                r = apply_mount(m, tmp_dir, var_tmp_dir);
+                if (r < 0)
+                        goto fail;
         }
-        remove_tmp = true;
 
-        memcpy(root_dir, tmp_dir, sizeof(tmp_dir)-1);
-        if (mkdir(root_dir, 0777) < 0) {
+        for (m = mounts; m < mounts + n; ++m) {
+                r = make_read_only(m);
+                if (r < 0)
+                        goto fail;
+        }
+
+        /* Remount / as the desired mode */
+        if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) {
                 r = -errno;
                 goto fail;
         }
-        remove_root = true;
 
-        if (need_inaccessible) {
-                memcpy(inaccessible_dir, tmp_dir, sizeof(tmp_dir)-1);
-                if (mkdir(inaccessible_dir, 0) < 0) {
-                        r = -errno;
-                        goto fail;
-                }
-                remove_inaccessible = true;
-        }
+        return 0;
 
-        if (need_private) {
-                mode_t u;
+fail:
+        for (m = mounts; m < mounts + n; ++m)
+                if (m->done)
+                        umount2(m->path, MNT_DETACH);
 
-                memcpy(private_dir, tmp_dir, sizeof(tmp_dir)-1);
+        return r;
+}
 
-                u = umask(0000);
-                if (mkdir(private_dir, 0777 + S_ISVTX) < 0) {
-                        umask(u);
+static int setup_one_tmp_dir(const char *id, const char *prefix, char **path) {
+        _cleanup_free_ char *x = NULL;
+        char bid[SD_ID128_STRING_MAX];
+        sd_id128_t boot_id;
+        int r;
 
-                        r = -errno;
-                        goto fail;
-                }
+        assert(id);
+        assert(prefix);
+        assert(path);
 
-                umask(u);
-                remove_private = true;
-        }
+        /* We include the boot id in the directory so that after a
+         * reboot we can easily identify obsolete directories. */
 
-        if (unshare(CLONE_NEWNS) < 0) {
-                r = -errno;
-                goto fail;
-        }
+        r = sd_id128_get_boot(&boot_id);
+        if (r < 0)
+                return r;
 
-        /* Remount / as SLAVE so that nothing mounted in the namespace
-           shows up in the parent */
-        if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0) {
-                r = -errno;
-                goto fail;
-        }
+        x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX", NULL);
+        if (!x)
+                return -ENOMEM;
 
-        for (p = paths; p < paths + n; p++)
-                if ((r = apply_mount(p, root_dir, inaccessible_dir, private_dir, flags)) < 0)
-                        goto undo_mounts;
+        RUN_WITH_UMASK(0077)
+                if (!mkdtemp(x))
+                        return -errno;
 
-        memcpy(old_root_dir, tmp_dir, sizeof(tmp_dir)-1);
-        if (!mkdtemp(old_root_dir)) {
-                r = -errno;
-                goto undo_mounts;
-        }
-        remove_old_root = true;
+        RUN_WITH_UMASK(0000) {
+                char *y;
 
-        if (chdir(root_dir) < 0) {
-                r = -errno;
-                goto undo_mounts;
+                y = strappenda(x, "/tmp");
+
+                if (mkdir(y, 0777 | S_ISVTX) < 0)
+                        return -errno;
         }
 
-        if (pivot_root(root_dir, old_root_dir) < 0) {
-                r = -errno;
-                goto undo_mounts;
+        *path = x;
+        x = NULL;
+
+        return 0;
+}
+
+int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) {
+        char *a, *b;
+        int r;
+
+        assert(id);
+        assert(tmp_dir);
+        assert(var_tmp_dir);
+
+        r = setup_one_tmp_dir(id, "/tmp", &a);
+        if (r < 0)
+                return r;
+
+        r = setup_one_tmp_dir(id, "/var/tmp", &b);
+        if (r < 0) {
+                char *t;
+
+                t = strappenda(a, "/tmp");
+                rmdir(t);
+                rmdir(a);
+
+                free(a);
+                return r;
         }
 
-        t = old_root_dir + sizeof(root_dir) - 1;
-        if (umount2(t, MNT_DETACH) < 0)
-                /* At this point it's too late to turn anything back,
-                 * since we are already in the new root. */
-                return -errno;
+        *tmp_dir = a;
+        *var_tmp_dir = b;
 
-        if (rmdir(t) < 0)
+        return 0;
+}
+
+int setup_netns(int netns_storage_socket[2]) {
+        _cleanup_close_ int netns = -1;
+        union {
+                struct cmsghdr cmsghdr;
+                uint8_t buf[CMSG_SPACE(sizeof(int))];
+        } control = {};
+        struct msghdr mh = {
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
+        };
+        struct cmsghdr *cmsg;
+        int r;
+
+        assert(netns_storage_socket);
+        assert(netns_storage_socket[0] >= 0);
+        assert(netns_storage_socket[1] >= 0);
+
+        /* We use the passed socketpair as a storage buffer for our
+         * namespace reference fd. Whatever process runs this first
+         * shall create a new namespace, all others should just join
+         * it. To serialize that we use a file lock on the socket
+         * pair.
+         *
+         * It's a bit crazy, but hey, works great! */
+
+        if (lockf(netns_storage_socket[0], F_LOCK, 0) < 0)
                 return -errno;
 
-        return 0;
+        if (recvmsg(netns_storage_socket[0], &mh, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) < 0) {
+                if (errno != EAGAIN) {
+                        r = -errno;
+                        goto fail;
+                }
 
-undo_mounts:
+                /* Nothing stored yet, so let's create a new namespace */
 
-        for (p--; p >= paths; p--) {
-                char full_path[PATH_MAX];
+                if (unshare(CLONE_NEWNET) < 0) {
+                        r = -errno;
+                        goto fail;
+                }
 
-                snprintf(full_path, sizeof(full_path), "%s%s", root_dir, p->path);
-                char_array_0(full_path);
+                loopback_setup();
 
-                umount2(full_path, MNT_DETACH);
-        }
+                netns = open("/proc/self/ns/net", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+                if (netns < 0) {
+                        r = -errno;
+                        goto fail;
+                }
 
-fail:
-        if (remove_old_root)
-                rmdir(old_root_dir);
+                r = 1;
+        } else {
+                /* Yay, found something, so let's join the namespace */
 
-        if (remove_inaccessible)
-                rmdir(inaccessible_dir);
+                for (cmsg = CMSG_FIRSTHDR(&mh); cmsg; cmsg = CMSG_NXTHDR(&mh, cmsg)) {
+                        if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
+                                assert(cmsg->cmsg_len == CMSG_LEN(sizeof(int)));
+                                netns = *(int*) CMSG_DATA(cmsg);
+                        }
+                }
 
-        if (remove_private)
-                rmdir(private_dir);
+                if (setns(netns, CLONE_NEWNET) < 0) {
+                        r = -errno;
+                        goto fail;
+                }
 
-        if (remove_root)
-                rmdir(root_dir);
+                r = 0;
+        }
+
+        cmsg = CMSG_FIRSTHDR(&mh);
+        cmsg->cmsg_level = SOL_SOCKET;
+        cmsg->cmsg_type = SCM_RIGHTS;
+        cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+        memcpy(CMSG_DATA(cmsg), &netns, sizeof(int));
+        mh.msg_controllen = cmsg->cmsg_len;
 
-        if (remove_tmp)
-                rmdir(tmp_dir);
+        if (sendmsg(netns_storage_socket[1], &mh, MSG_DONTWAIT|MSG_NOSIGNAL) < 0) {
+                r = -errno;
+                goto fail;
+        }
 
-             free(paths);
+fail:
+        lockf(netns_storage_socket[0], F_ULOCK, 0);
 
         return r;
 }