[OpenWrt-Devel] [PATCH procd 4/4] ujail: rework fs jail part
Etienne CHAMPETIER
champetier.etienne at gmail.com
Sun Nov 22 19:39:24 EST 2015
this patch:
-add script (#!) dependencies detection (we add interpreter and it's dependencies)
-add dependencies detection for all files added with -r or -w (ELF and scripts)
-use PATH_MAX for path related buffers
-check magic ELF header before trying to parse the file
-search in /lib before /lib64
-add ELF interpreter (DT_INTERP)
we still don't handle
-DT_RPATH, DT_RUNPATH, nodeflib, ...
see http://man7.org/linux/man-pages/man8/ld.so.8.html
-musl ld conf file
-coffee :)
quickly run tested on DD r47603 (x86_64 kvm) and ubuntu
not tested yet on CC
should fix
https://dev.openwrt.org/ticket/20785
Signed-off-by: Etienne CHAMPETIER <champetier.etienne at gmail.com>
---
CMakeLists.txt | 2 +-
jail/elf.c | 132 +++++++++++++++---------------------------
jail/elf.h | 9 ++-
jail/fs.c | 179 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
jail/fs.h | 20 +++++++
jail/jail.c | 112 +++++++++++-------------------------
jail/jail.h | 18 ++++++
jail/log.h | 1 +
8 files changed, 303 insertions(+), 170 deletions(-)
create mode 100644 jail/fs.c
create mode 100644 jail/fs.h
create mode 100644 jail/jail.h
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d749c25..2718125 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -87,7 +87,7 @@ ADD_DEPENDENCIES(preload-seccomp syscall-names-h)
endif()
IF(JAIL_SUPPORT)
-ADD_EXECUTABLE(ujail jail/jail.c jail/elf.c jail/capabilities.c)
+ADD_EXECUTABLE(ujail jail/jail.c jail/elf.c jail/fs.c jail/capabilities.c)
TARGET_LINK_LIBRARIES(ujail ubox blobmsg_json)
INSTALL(TARGETS ujail
RUNTIME DESTINATION ${CMAKE_INSTALL_SBINDIR}
diff --git a/jail/elf.c b/jail/elf.c
index a26aa0b..c8d1221 100644
--- a/jail/elf.c
+++ b/jail/elf.c
@@ -12,26 +12,25 @@
*/
#define _GNU_SOURCE
-#include <sys/mman.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
-#include <libgen.h>
#include <glob.h>
#include <elf.h>
+#include <assert.h>
+#include <linux/limits.h>
#include <libubox/utils.h>
+#include "fs.h"
#include "elf.h"
+#include "log.h"
struct avl_tree libraries;
static LIST_HEAD(library_paths);
-void alloc_library_path(const char *path)
+static void alloc_library_path(const char *path)
{
struct stat s;
if (stat(path, &s))
@@ -51,7 +50,11 @@ void alloc_library_path(const char *path)
DEBUG("adding ld.so path %s\n", path);
}
-static void alloc_library(const char *path, const char *name)
+/*
+ * path = full path
+ * name = soname/avl key
+ */
+void alloc_library(const char *path, const char *name)
{
struct library *l;
char *_name, *_path;
@@ -66,52 +69,39 @@ static void alloc_library(const char *path, const char *name)
l->path = strcpy(_path, path);
avl_insert(&libraries, &l->avl);
- DEBUG("adding library %s/%s\n", path, name);
+ DEBUG("adding library %s (%s)\n", path, name);
}
-static int elf_open(char **dir, const char *file)
+int elf_open(char **fullpath, const char *file)
{
+ *fullpath = NULL;
+ assert(file[0] != '/');
+
struct library_path *p;
- char path[256];
+ char path[PATH_MAX];
int fd = -1;
- *dir = NULL;
-
list_for_each_entry(p, &library_paths, list) {
- if (strlen(p->path))
- snprintf(path, sizeof(path), "%s/%s", p->path, file);
- else
- strncpy(path, file, sizeof(path));
+ snprintf(path, sizeof(path), "%s/%s", p->path, file);
fd = open(path, O_RDONLY);
if (fd >= 0) {
- *dir = p->path;
+ *fullpath = strdup(path);
break;
}
}
- if (fd == -1)
- fd = open(file, O_RDONLY);
-
return fd;
}
char* find_lib(const char *file)
{
struct library *l;
- static char path[256];
- const char *p;
l = avl_find_element(&libraries, file, l, avl);
if (!l)
return NULL;
- p = l->path;
- if (strstr(p, "local"))
- p = "/lib";
-
- snprintf(path, sizeof(path), "%s/%s", p, file);
-
- return path;
+ return l->path;
}
static int elf64_find_section(const char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
@@ -201,7 +191,7 @@ static int elf32_scan_dynamic(const char *map, int dyn_offset, int dyn_size, int
if (curr->d_tag != DT_NEEDED)
continue;
- if (elf_load_deps(&strtab[curr->d_un.d_val]))
+ if (add_path_and_deps(&strtab[curr->d_un.d_val], 1, -1, 1) == -1)
return -1;
}
@@ -235,85 +225,48 @@ static int elf64_scan_dynamic(const char *map, int dyn_offset, int dyn_size, int
if (curr->d_tag != DT_NEEDED)
continue;
- if (elf_load_deps(&strtab[curr->d_un.d_val]))
+ if (add_path_and_deps(&strtab[curr->d_un.d_val], 1, -1, 1) == -1)
return -1;
}
return 0;
}
-int elf_load_deps(const char *library)
+int elf_load_deps(const char *path, const char *map)
{
unsigned int dyn_offset, dyn_size;
unsigned int load_offset, load_vaddr;
- struct stat s;
- char *map = NULL, *dir = NULL;
- int clazz, fd, ret = -1;
-
- if (avl_find(&libraries, library))
- return 0;
-
- fd = elf_open(&dir, library);
-
- if (fd < 0) {
- ERROR("failed to open %s\n", library);
- return -1;
- }
-
- if (fstat(fd, &s) == -1) {
- ERROR("failed to stat %s\n", library);
- ret = -1;
- goto err_out;
- }
-
- map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
- if (map == MAP_FAILED) {
- ERROR("failed to mmap %s\n", library);
- ret = -1;
- goto err_out;
- }
+ unsigned int interp_offset;
if (elf_find_section(map, PT_LOAD, &load_offset, NULL, &load_vaddr)) {
- ERROR("failed to load the .load section from %s\n", library);
- ret = -1;
- goto err_out;
+ ERROR("failed to load the .load section from %s\n", path);
+ return -1;
}
if (elf_find_section(map, PT_DYNAMIC, &dyn_offset, &dyn_size, NULL)) {
- ERROR("failed to load the .dynamic section from %s\n", library);
- ret = -1;
- goto err_out;
+ ERROR("failed to load the .dynamic section from %s\n", path);
+ return -1;
}
- if (dir) {
- alloc_library(dir, library);
- } else {
- char *elf1 = strdup(library);
- char *elf2 = strdup(library);
-
- alloc_library(dirname(elf1), basename(elf2));
- free(elf1);
- free(elf2);
+ if (elf_find_section(map, PT_INTERP, &interp_offset, NULL, NULL) == 0) {
+ add_path_and_deps(map+interp_offset, 1, -1, 0);
}
- clazz = map[EI_CLASS];
+
+ int clazz = map[EI_CLASS];
if (clazz == ELFCLASS32)
- ret = elf32_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
+ return elf32_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
else if (clazz == ELFCLASS64)
- ret = elf64_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
-
-err_out:
- if (map)
- munmap(map, s.st_size);
- close(fd);
+ return elf64_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
- return ret;
+ ERROR("unknown elf format %d\n", clazz);
+ return -1;
}
-void load_ldso_conf(const char *conf)
+static void load_ldso_conf(const char *conf)
{
FILE* fp = fopen(conf, "r");
- char line[256];
+ char line[PATH_MAX];
if (!fp) {
DEBUG("failed to open %s\n", conf);
@@ -323,7 +276,7 @@ void load_ldso_conf(const char *conf)
while (!feof(fp)) {
int len;
- if (!fgets(line, 256, fp))
+ if (!fgets(line, sizeof(line), fp))
break;
len = strlen(line);
if (len < 2)
@@ -355,3 +308,12 @@ void load_ldso_conf(const char *conf)
fclose(fp);
}
+
+void init_library_path(void)
+{
+ avl_init(&libraries, avl_strcmp, false, NULL);
+ alloc_library_path("/lib");
+ alloc_library_path("/lib64");
+ alloc_library_path("/usr/lib");
+ load_ldso_conf("/etc/ld.so.conf");
+}
diff --git a/jail/elf.h b/jail/elf.h
index 6c14c39..ea67837 100644
--- a/jail/elf.h
+++ b/jail/elf.h
@@ -15,8 +15,6 @@
#include <libubox/avl.h>
#include <libubox/avl-cmp.h>
-#include "log.h"
-
struct library {
struct avl_node avl;
char *name;
@@ -30,9 +28,10 @@ struct library_path {
struct avl_tree libraries;
-void alloc_library_path(const char *path);
-int elf_load_deps(const char *library);
+void alloc_library(const char *path, const char *name);
+int elf_open(char **fullpath, const char *file);
+int elf_load_deps(const char *path, const char *map);
char* find_lib(const char *file);
-void load_ldso_conf(const char *conf);
+void init_library_path(void);
#endif
diff --git a/jail/fs.c b/jail/fs.c
new file mode 100644
index 0000000..c1ae1da
--- /dev/null
+++ b/jail/fs.c
@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 2015 John Crispin <blogic at openwrt.org>
+ * Copyright (C) 2015 Etienne Champetier <champetier.etienne at gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2.1
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#define _GNU_SOURCE
+
+#include <assert.h>
+#include <elf.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <libubox/avl.h>
+#include <libubox/avl-cmp.h>
+
+#include "elf.h"
+#include "fs.h"
+#include "jail.h"
+#include "log.h"
+
+struct mount {
+ struct avl_node avl;
+ const char *path;
+ int readonly;
+ int error;
+};
+
+struct avl_tree mounts;
+
+static int add_mount(const char *path, int readonly, int error)
+{
+ if (avl_find(&mounts, path))
+ return 1;
+
+ struct mount *m;
+ m = calloc(1, sizeof(struct mount));
+ assert(m != NULL);
+ m->avl.key = m->path = strdup(path);
+ m->readonly = readonly;
+ m->error = error;
+
+ avl_insert(&mounts, &m->avl);
+ DEBUG("adding mount %s ro(%d) err(%d)\n", m->path, m->readonly, m->error != 0);
+ return 0;
+}
+
+int mount_all(const char *jailroot) {
+ struct library *l;
+ struct mount *m;
+
+ avl_for_each_element(&libraries, l, avl)
+ add_mount(l->path, 1, -1);
+
+ avl_for_each_element(&mounts, m, avl)
+ if (mount_bind(jailroot, m->path, m->readonly, m->error))
+ return -1;
+
+ return 0;
+}
+
+void mount_list_init(void) {
+ avl_init(&mounts, avl_strcmp, false, NULL);
+}
+
+static int add_script_interp(const char *path, const char *map, int size)
+{
+ int start = 2;
+ while (start < size && map[start] != '/') {
+ start++;
+ }
+ if (start >= size) {
+ ERROR("bad script interp (%s)", path);
+ return -1;
+ }
+ int stop = start + 1;
+ while (stop < size && map[stop] > 0x20 && map[stop] <= 0x7e) {
+ stop++;
+ }
+ if (stop >= size || (stop-start) > PATH_MAX) {
+ ERROR("bad script interp (%s)", path);
+ return -1;
+ }
+ char buf[PATH_MAX];
+ strncpy(buf, map+start, stop-start);
+ return add_path_and_deps(buf, 1, -1, 0);
+}
+
+int add_path_and_deps(const char *path, int readonly, int error, int lib)
+{
+ assert(path != NULL);
+
+ if (lib == 0 && path[0] != '/') {
+ ERROR("%s is not an absolute path\n", path);
+ return error;
+ }
+
+ char *map = NULL;
+ int fd, ret = -1;
+ if (path[0] == '/') {
+ if (avl_find(&mounts, path))
+ return 0;
+ fd = open(path, O_RDONLY);
+ if (fd == -1)
+ return error;
+ add_mount(path, readonly, error);
+ } else {
+ if (avl_find(&libraries, path))
+ return 0;
+ char *fullpath;
+ fd = elf_open(&fullpath, path);
+ if (fd == -1)
+ return error;
+ if (fullpath) {
+ alloc_library(fullpath, path);
+ free(fullpath);
+ }
+ }
+
+ struct stat s;
+ if (fstat(fd, &s) == -1) {
+ ERROR("fstat(%s) failed: %s\n", path, strerror(errno));
+ ret = error;
+ goto out;
+ }
+
+ if (!S_ISREG(s.st_mode)) {
+ ret = 0;
+ goto out;
+ }
+
+ /* too small to be an ELF or a script */
+ if (s.st_size < 4) {
+ ret = 0;
+ goto out;
+ }
+
+ map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+ if (map == MAP_FAILED) {
+ ERROR("failed to mmap %s\n", path);
+ ret = -1;
+ goto out;
+ }
+
+ if (map[0] == '#' && map[1] == '!') {
+ ret = add_script_interp(path, map, s.st_size);
+ goto out;
+ }
+
+ if (map[0] == ELFMAG0 && map[1] == ELFMAG1 && map[2] == ELFMAG2 && map[3] == ELFMAG3) {
+ ret = elf_load_deps(path, map);
+ goto out;
+ }
+
+ ret = 0;
+
+out:
+ if (fd >= 0)
+ close(fd);
+ if (map)
+ munmap(map, s.st_size);
+
+ return ret;
+}
+
diff --git a/jail/fs.h b/jail/fs.h
new file mode 100644
index 0000000..0839d5c
--- /dev/null
+++ b/jail/fs.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2015 Etienne Champetier <champetier.etienne at gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2.1
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _FS_H__
+
+int add_path_and_deps(const char *path, int readonly, int error, int lib);
+int mount_all(const char *jailroot);
+void mount_list_init(void);
+
+#endif
diff --git a/jail/jail.c b/jail/jail.c
index 08babde..db74504 100644
--- a/jail/jail.c
+++ b/jail/jail.c
@@ -18,19 +18,20 @@
#include <stdlib.h>
#include <unistd.h>
-#include <values.h>
#include <errno.h>
-#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <libgen.h>
#include <sched.h>
+#include <linux/limits.h>
-#include "elf.h"
#include "capabilities.h"
+#include "elf.h"
+#include "fs.h"
+#include "jail.h"
+#include "log.h"
-#include <libubox/list.h>
#include <libubox/uloop.h>
#define STACK_SIZE (1024 * 1024)
@@ -48,16 +49,6 @@ static struct {
int sysfs;
} opts;
-struct extra {
- struct list_head list;
-
- const char *path;
- const char *name;
- int readonly;
-};
-
-static LIST_HEAD(extras);
-
extern int pivot_root(const char *new_root, const char *put_old);
int debug = 0;
@@ -89,32 +80,23 @@ static int mkdir_p(char *dir, mode_t mask)
return ret;
}
-static int mount_bind(const char *root, const char *path, const char *name, int readonly, int error)
+int mount_bind(const char *root, const char *path, int readonly, int error)
{
- const char *p = path;
struct stat s;
- char old[256];
- char new[256];
+ char new[PATH_MAX];
int fd;
- if (strstr(p, "local"))
- p = "/lib";
-
- snprintf(old, sizeof(old), "%s/%s", path, name);
- snprintf(new, sizeof(new), "%s%s", root, p);
-
- mkdir_p(new, 0755);
-
- snprintf(new, sizeof(new), "%s%s/%s", root, p, name);
-
- if (stat(old, &s)) {
- ERROR("%s does not exist\n", old);
+ if (stat(path, &s)) {
+ ERROR("%s does not exist\n", path);
return error;
}
+ snprintf(new, sizeof(new), "%s%s", root, path);
if (S_ISDIR(s.st_mode)) {
mkdir_p(new, 0755);
} else {
+ mkdir_p(dirname(new), 0755);
+ snprintf(new, sizeof(new), "%s%s", root, path);
fd = creat(new, 0644);
if (fd == -1) {
ERROR("failed to create %s: %s\n", new, strerror(errno));
@@ -123,8 +105,8 @@ static int mount_bind(const char *root, const char *path, const char *name, int
close(fd);
}
- if (mount(old, new, NULL, MS_BIND, NULL)) {
- ERROR("failed to mount -B %s %s: %s\n", old, new, strerror(errno));
+ if (mount(path, new, NULL, MS_BIND, NULL)) {
+ ERROR("failed to mount -B %s %s: %s\n", path, new, strerror(errno));
return -1;
}
@@ -133,16 +115,13 @@ static int mount_bind(const char *root, const char *path, const char *name, int
return -1;
}
- DEBUG("mount -B %s %s\n", old, new);
+ DEBUG("mount -B %s %s\n", path, new);
return 0;
}
-static int build_jail_fs()
+static int build_jail_fs(void)
{
- struct library *l;
- struct extra *m;
-
if (mount("tmpfs", opts.path, "tmpfs", MS_NOATIME, "mode=0755")) {
ERROR("tmpfs mount failed %s\n", strerror(errno));
return -1;
@@ -153,29 +132,20 @@ static int build_jail_fs()
return -1;
}
- avl_init(&libraries, avl_strcmp, false, NULL);
- alloc_library_path("/lib64");
- alloc_library_path("/lib");
- alloc_library_path("/usr/lib");
- load_ldso_conf("/etc/ld.so.conf");
-
- if (elf_load_deps(*opts.jail_argv)) {
+ if (add_path_and_deps(*opts.jail_argv, 1, -1, 0)) {
ERROR("failed to load dependencies\n");
return -1;
}
- if (opts.seccomp && elf_load_deps("libpreload-seccomp.so")) {
+ if (opts.seccomp && add_path_and_deps("libpreload-seccomp.so", 1, -1, 1)) {
ERROR("failed to load libpreload-seccomp.so\n");
return -1;
}
- avl_for_each_element(&libraries, l, avl)
- if (mount_bind(opts.path, l->path, l->name, 1, -1))
- return -1;
-
- list_for_each_entry(m, &extras, list)
- if (mount_bind(opts.path, m->path, m->name, m->readonly, 0))
- return -1;
+ if (mount_all(opts.path)) {
+ ERROR("mount_all() failed\n");
+ return -1;
+ }
char *mpoint;
if (asprintf(&mpoint, "%s/old", opts.path) < 0) {
@@ -209,8 +179,8 @@ static int build_jail_fs()
static char** build_envp(const char *seccomp)
{
static char *envp[MAX_ENVP];
- static char preload_var[64];
- static char seccomp_var[64];
+ static char preload_var[PATH_MAX];
+ static char seccomp_var[PATH_MAX];
static char debug_var[] = "LD_DEBUG=all";
char *preload_lib = find_lib("libpreload-seccomp.so");
int count = 0;
@@ -256,7 +226,7 @@ ujail will not use namespace/build a jail,\n\
and will only drop capabilities/apply seccomp filter.\n\n");
}
-static int exec_jail()
+static int exec_jail(void)
{
char **envp = build_envp(opts.seccomp);
if (!envp)
@@ -306,24 +276,6 @@ static struct uloop_process jail_process = {
.cb = jail_process_handler,
};
-static void add_extra(char *name, int readonly)
-{
- struct extra *f;
-
- if (*name != '/') {
- ERROR("%s is not an absolute path\n", name);
- return;
- }
-
- f = calloc(1, sizeof(struct extra));
-
- f->name = basename(name);
- f->path = dirname(strdup(name));
- f->readonly = readonly;
-
- list_add_tail(&f->list, &extras);
-}
-
int main(int argc, char **argv)
{
uid_t uid = getuid();
@@ -338,6 +290,8 @@ int main(int argc, char **argv)
}
umask(022);
+ mount_list_init();
+ init_library_path();
while ((ch = getopt(argc, argv, OPT_ARGS)) != -1) {
switch (ch) {
@@ -358,11 +312,11 @@ int main(int argc, char **argv)
break;
case 'S':
opts.seccomp = optarg;
- add_extra(optarg, 1);
+ add_path_and_deps(optarg, 1, -1, 0);
break;
case 'C':
opts.capabilities = optarg;
- add_extra(optarg, 1);
+ add_path_and_deps(optarg, 1, -1, 0);
break;
case 'P':
opts.namespace = 1;
@@ -373,19 +327,19 @@ int main(int argc, char **argv)
break;
case 'r':
opts.namespace = 1;
- add_extra(optarg, 1);
+ add_path_and_deps(optarg, 1, 0, 0);
break;
case 'w':
opts.namespace = 1;
- add_extra(optarg, 0);
+ add_path_and_deps(optarg, 0, 0, 0);
break;
case 'u':
opts.namespace = 1;
- add_extra(ubus, 0);
+ add_path_and_deps(ubus, 0, -1, 0);
break;
case 'l':
opts.namespace = 1;
- add_extra(log, 0);
+ add_path_and_deps(log, 0, -1, 0);
break;
}
}
diff --git a/jail/jail.h b/jail/jail.h
new file mode 100644
index 0000000..fc69ef6
--- /dev/null
+++ b/jail/jail.h
@@ -0,0 +1,18 @@
+/*
+ * Copyright (C) 2015 Etienne Champetier <champetier.etienne at gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2.1
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _JAIL_H__
+
+int mount_bind(const char *root, const char *path, int readonly, int error);
+
+#endif
diff --git a/jail/log.h b/jail/log.h
index b1d201e..e56fc6a 100644
--- a/jail/log.h
+++ b/jail/log.h
@@ -12,6 +12,7 @@
*/
extern int debug;
+#include <stdio.h>
#include <syslog.h>
#define INFO(fmt, ...) do { \
--
1.9.1
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