jail: add support for (ram-)overlayfs

Add support for running service with a read/write filesystem overlay.
This can either be a user-defined directory for persistency or reside
on a tmpfs with fixed size in the RAM.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

diff --git a/jail/jail.c b/jail/jail.c
index 78f0c6bbb6ceea6dcb150044df69fc0ed6036ef3..ec106d27147161f70d9ab6b098fe1fcebcf1837a 100644 (file)
--- a/jail/jail.c
+++ b/jail/jail.c
@@ -40,7 +40,7 @@
 #include <libubus.h>
 
 #define STACK_SIZE     (1024 * 1024)
-#define OPT_ARGS       "S:C:n:h:r:w:d:psulocU:G:NR:fF"
+#define OPT_ARGS       "S:C:n:h:r:w:d:psulocU:G:NR:fFO:T:"
 
 static struct {
        char *name;
@@ -51,6 +51,8 @@ static struct {
        char *user;
        char *group;
        char *extroot;
+       char *overlaydir;
+       char *tmpoverlaysize;
        int no_new_privs;
        int namespace;
        int procfs;
@@ -147,9 +149,46 @@ int mount_bind(const char *root, const char *path, int readonly, int error) {
        return _mount_bind(root, path, NULL, readonly, 0, error);
 }
 
+static int mount_overlay(char *jail_root, char *overlaydir) {
+       char *upperdir, *workdir, *optsstr;
+       const char mountoptsformat[] = "lowerdir=%s,upperdir=%s,workdir=%s";
+       int ret = -1;
+
+       if (asprintf(&upperdir, "%s%s", overlaydir, "/upper") < 0)
+               goto out;
+
+       if (asprintf(&workdir, "%s%s", overlaydir, "/work") < 0)
+               goto upper_printf;
+
+       if (asprintf(&optsstr, mountoptsformat, jail_root, upperdir, workdir) < 0)
+               goto work_printf;
+
+       if (mkdir_p(upperdir, 0755) || mkdir_p(workdir, 0755))
+               goto opts_printf;
+
+       DEBUG("mount -t overlay %s %s (%s)\n", jail_root, jail_root, optsstr);
+
+       if (mount(jail_root, jail_root, "overlay", MS_NOATIME, optsstr))
+               goto opts_printf;
+
+       ret = 0;
+
+opts_printf:
+       free(optsstr);
+work_printf:
+       free(workdir);
+upper_printf:
+       free(upperdir);
+out:
+       return ret;
+}
+
 static int build_jail_fs(void)
 {
        char jail_root[] = "/tmp/ujail-XXXXXX";
+       char tmpovdir[] = "/tmp/ujail-overlay-XXXXXX";
+       char *overlaydir = NULL;
+
        if (mkdtemp(jail_root) == NULL) {
                ERROR("mkdtemp(%s) failed: %m\n", jail_root);
                return -1;
@@ -173,6 +212,29 @@ static int build_jail_fs(void)
                }
        }
 
+       if (opts.tmpoverlaysize) {
+               char mountoptsstr[] = "mode=0755,size=XXXXXXXX";
+
+               snprintf(mountoptsstr, sizeof(mountoptsstr),
+                        "mode=0755,size=%s", opts.tmpoverlaysize);
+               if (mkdtemp(tmpovdir) == NULL) {
+                       ERROR("mkdtemp(%s) failed: %m\n", jail_root);
+                       return -1;
+               }
+               if (mount("tmpfs", tmpovdir, "tmpfs", MS_NOATIME,
+                         mountoptsstr)) {
+                       ERROR("failed to mount tmpfs for overlay (size=%s)\n", opts.tmpoverlaysize);
+                       return -1;
+               }
+               overlaydir = tmpovdir;
+       }
+
+       if (opts.overlaydir)
+               overlaydir = opts.overlaydir;
+
+       if (overlaydir)
+               mount_overlay(jail_root, overlaydir);
+
        if (chdir(jail_root)) {
                ERROR("chdir(%s) (jail_root) failed: %m\n", jail_root);
                return -1;
@@ -209,7 +271,15 @@ static int build_jail_fs(void)
        }
 
        snprintf(dirbuf, sizeof(dirbuf), "/old%s", jail_root);
+       umount2(dirbuf, MNT_DETACH);
        rmdir(dirbuf);
+       if (opts.tmpoverlaysize) {
+               char tmpdirbuf[sizeof(tmpovdir) + 4];
+               snprintf(tmpdirbuf, sizeof(tmpdirbuf), "/old%s", tmpovdir);
+               umount2(tmpdirbuf, MNT_DETACH);
+               rmdir(tmpdirbuf);
+       }
+
        umount2("/old", MNT_DETACH);
        rmdir("/old");
 
@@ -361,6 +431,8 @@ static void usage(void)
        fprintf(stderr, "namespace jail options:\n");
        fprintf(stderr, "  -h <hostname>\tchange the hostname of the jail\n");
        fprintf(stderr, "  -N\t\tjail has network namespace\n");
+       fprintf(stderr, "  -f\t\tjail has user namespace\n");
+       fprintf(stderr, "  -F\t\tjail has cgroups namespace\n");
        fprintf(stderr, "  -r <file>\treadonly files that should be staged\n");
        fprintf(stderr, "  -w <file>\twriteable files that should be staged\n");
        fprintf(stderr, "  -p\t\tjail has /proc\n");
@@ -371,6 +443,8 @@ static void usage(void)
        fprintf(stderr, "  -G <name>\tgroup to run jailed process\n");
        fprintf(stderr, "  -o\t\tremont jail root (/) read only\n");
        fprintf(stderr, "  -R <dir>\texternal jail rootfs (system container)\n");
+       fprintf(stderr, "  -O <dir>\tdirectory for r/w overlayfs\n");
+       fprintf(stderr, "  -T <size>\tuse tmpfs r/w overlayfs with <size>\n");
        fprintf(stderr, "\nWarning: by default root inside the jail is the same\n\
 and he has the same powers as root outside the jail,\n\
 thus he can escape the jail and/or break stuff.\n\
@@ -614,12 +688,23 @@ int main(int argc, char **argv)
                case 'G':
                        opts.group = optarg;
                        break;
+               case 'O':
+                       opts.overlaydir = optarg;
+                       break;
+               case 'T':
+                       opts.tmpoverlaysize = optarg;
+                       break;
                }
        }
 
        if (opts.namespace)
                opts.namespace |= CLONE_NEWIPC | CLONE_NEWPID;
 
+       if (opts.tmpoverlaysize && strlen(opts.tmpoverlaysize) > 8) {
+               ERROR("size parameter too long: \"%s\"\n", opts.tmpoverlaysize);
+               return -1;
+       }
+
        /* no <binary> param found */
        if (argc - optind < 1) {
                usage();
@@ -644,11 +729,11 @@ int main(int argc, char **argv)
                        ERROR("failed to load dependencies\n");
                        return -1;
                }
+       }
 
-               if (opts.namespace && opts.seccomp && add_path_and_deps("libpreload-seccomp.so", 1, -1, 1)) {
-                       ERROR("failed to load libpreload-seccomp.so\n");
-                       return -1;
-               }
+       if (opts.namespace && opts.seccomp && add_path_and_deps("libpreload-seccomp.so", 1, -1, 1)) {
+               ERROR("failed to load libpreload-seccomp.so\n");
+               return -1;
        }
 
        if (opts.name)

diff --git a/service/instance.c b/service/instance.c
index d29aa0da53e249b5fa946772fb0ec3359615eef9..c941157eda457503c58ff1f635b4f18403915f05 100644 (file)
--- a/service/instance.c
+++ b/service/instance.c
@@ -63,6 +63,8 @@ enum {
        INSTANCE_ATTR_TERMTIMEOUT,
        INSTANCE_ATTR_FACILITY,
        INSTANCE_ATTR_EXTROOT,
+       INSTANCE_ATTR_OVERLAYDIR,
+       INSTANCE_ATTR_TMPOVERLAYSIZE,
        __INSTANCE_ATTR_MAX
 };
 
@@ -91,6 +93,8 @@ static const struct blobmsg_policy instance_attr[__INSTANCE_ATTR_MAX] = {
        [INSTANCE_ATTR_TERMTIMEOUT] = { "term_timeout", BLOBMSG_TYPE_INT32 },
        [INSTANCE_ATTR_FACILITY] = { "facility", BLOBMSG_TYPE_STRING },
        [INSTANCE_ATTR_EXTROOT] = { "extroot", BLOBMSG_TYPE_STRING },
+       [INSTANCE_ATTR_OVERLAYDIR] = { "overlaydir", BLOBMSG_TYPE_STRING },
+       [INSTANCE_ATTR_TMPOVERLAYSIZE] = { "tmpoverlaysize", BLOBMSG_TYPE_STRING },
 };
 
 enum {
@@ -275,6 +279,16 @@ jail_run(struct service_instance *in, char **argv)
                argv[argc++] = in->extroot;
        }
 
+       if (in->overlaydir) {
+               argv[argc++] = "-O";
+               argv[argc++] = in->overlaydir;
+       }
+
+       if (in->tmpoverlaysize) {
+               argv[argc++] = "-T";
+               argv[argc++] = in->tmpoverlaysize;
+       }
+
        blobmsg_list_for_each(&jail->mount, var) {
                const char *type = blobmsg_data(var->data);
 
@@ -906,9 +920,14 @@ instance_jail_parse(struct service_instance *in, struct blob_attr *attr)
        if (in->group)
                jail->argc += 2;
 
-       if (in->extroot) {
+       if (in->extroot)
+               jail->argc += 2;
+
+       if (in->overlaydir)
+               jail->argc += 2;
+
+       if (in->tmpoverlaysize)
                jail->argc += 2;
-       }
 
        if (in->no_new_privs)
                jail->argc++;
@@ -1024,6 +1043,12 @@ instance_config_parse(struct service_instance *in)
        if (tb[INSTANCE_ATTR_EXTROOT])
                in->extroot = strdup(blobmsg_get_string(tb[INSTANCE_ATTR_EXTROOT]));
 
+       if (tb[INSTANCE_ATTR_OVERLAYDIR])
+               in->overlaydir = strdup(blobmsg_get_string(tb[INSTANCE_ATTR_OVERLAYDIR]));
+
+       if (tb[INSTANCE_ATTR_TMPOVERLAYSIZE])
+               in->tmpoverlaysize = strdup(blobmsg_get_string(tb[INSTANCE_ATTR_TMPOVERLAYSIZE]));
+
        if (tb[INSTANCE_ATTR_PIDFILE]) {
                char *pidfile = blobmsg_get_string(tb[INSTANCE_ATTR_PIDFILE]);
                if (pidfile)
@@ -1173,6 +1198,8 @@ instance_free(struct service_instance *in)
        free(in->user);
        free(in->group);
        free(in->extroot);
+       free(in->overlaydir);
+       free(in->tmpoverlaysize);
        free(in->jail.name);
        free(in->jail.hostname);
        free(in->seccomp);
@@ -1298,6 +1325,11 @@ void instance_dump(struct blob_buf *b, struct service_instance *in, int verbose)
                        blobmsg_add_string(b, "hostname", in->jail.hostname);
                if (in->extroot)
                        blobmsg_add_string(b, "extroot", in->extroot);
+               if (in->overlaydir)
+                       blobmsg_add_string(b, "overlaydir", in->overlaydir);
+               if (in->tmpoverlaysize)
+                       blobmsg_add_string(b, "tmpoverlaysize", in->tmpoverlaysize);
+
                blobmsg_add_u8(b, "procfs", in->jail.procfs);
                blobmsg_add_u8(b, "sysfs", in->jail.sysfs);
                blobmsg_add_u8(b, "ubus", in->jail.ubus);

diff --git a/service/instance.h b/service/instance.h
index 7e80c61946516112bef33b6f2a96761f52d5d826..43a65613f1e1aadabdc73df17f4ea7f42d1b1df6 100644 (file)
--- a/service/instance.h
+++ b/service/instance.h
@@ -67,6 +67,8 @@ struct service_instance {
        char *seccomp;
        char *pidfile;
        char *extroot;
+       char *overlaydir;
+       char *tmpoverlaysize;
        int syslog_facility;
        int exit_code;