lxc.h \
lxclock.h \
macro.h \
+ memory_utils.h \
monitor.h \
namespace.h \
raw_syscalls.h \
+ rexec.h \
start.h \
state.h \
storage/btrfs.h \
lxclock.c lxclock.h \
lxcseccomp.h \
macro.h \
+ memory_utils.h \
mainloop.c mainloop.h \
namespace.c namespace.h \
nl.c nl.h \
endif
if ENFORCE_MEMFD_REXEC
-liblxc_la_SOURCES += rexec.c
+liblxc_la_SOURCES += rexec.c rexec.h
endif
AM_CFLAGS = -DLXCROOTFSMOUNT=\"$(LXCROOTFSMOUNT)\" \
if ENABLE_TOOLS
lxc_attach_SOURCES = tools/lxc_attach.c \
+ rexec.c rexec.h \
tools/arguments.c tools/arguments.h
lxc_autostart_SOURCES = tools/lxc_autostart.c \
tools/arguments.c tools/arguments.h
#include "config.h"
#include "file_utils.h"
#include "macro.h"
+#include "memory_utils.h"
#include "string_utils.h"
+#include "utils.h"
int lxc_write_to_file(const char *filename, const void *buf, size_t count,
bool add_newline, mode_t mode)
int lxc_make_tmpfile(char *template, bool rm)
{
- int fd, ret;
+ __do_close_prot_errno int fd = -EBADF;
+ int ret;
mode_t msk;
msk = umask(0022);
if (fd < 0)
return -1;
+ if (lxc_set_cloexec(fd))
+ return -1;
+
if (!rm)
- return fd;
+ return move_fd(fd);
ret = unlink(template);
- if (ret < 0) {
- close(fd);
+ if (ret < 0)
return -1;
- }
- return fd;
+ return move_fd(fd);
}
bool is_fs_type(const struct statfs *fs, fs_type_magic magic_val)
return NULL;
}
+
+int fd_to_fd(int from, int to)
+{
+ for (;;) {
+ uint8_t buf[PATH_MAX];
+ uint8_t *p = buf;
+ ssize_t bytes_to_write;
+ ssize_t bytes_read;
+
+ bytes_read = lxc_read_nointr(from, buf, sizeof buf);
+ if (bytes_read < 0)
+ return -1;
+ if (bytes_read == 0)
+ break;
+
+ bytes_to_write = (size_t)bytes_read;
+ do {
+ ssize_t bytes_written;
+
+ bytes_written = lxc_write_nointr(to, p, bytes_to_write);
+ if (bytes_written < 0)
+ return -1;
+
+ bytes_to_write -= bytes_written;
+ p += bytes_written;
+ } while (bytes_to_write > 0);
+ }
+
+ return 0;
+}
* Copyright © 2018 Christian Brauner <christian.brauner@ubuntu.com>.
* Copyright © 2018 Canonical Ltd.
*
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2, as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+
+ * This library 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.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef __LXC_FILE_UTILS_H
extern ssize_t lxc_sendfile_nointr(int out_fd, int in_fd, off_t *offset,
size_t count);
extern char *file_to_buf(char *path, size_t *length);
+extern int fd_to_fd(int from, int to);
#endif /* __LXC_FILE_UTILS_H */
* Copyright © 2018 Christian Brauner <christian.brauner@ubuntu.com>.
* Copyright © 2018 Canonical Ltd.
*
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2, as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+
+ * This library 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.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef __LXC_MACRO_H
/* Maximum number of bytes sendfile() is able to send in one go. */
#define LXC_SENDFILE_MAX 0x7ffff000
+#define move_ptr(ptr) \
+ ({ \
+ typeof(ptr) __internal_ptr__ = (ptr); \
+ (ptr) = NULL; \
+ __internal_ptr__; \
+ })
+
+#define move_fd(fd) \
+ ({ \
+ int __internal_fd__ = (fd); \
+ (fd) = -EBADF; \
+ __internal_fd__; \
+ })
+
#endif /* __LXC_MACRO_H */
--- /dev/null
+/* liblxcapi
+ *
+ * Copyright © 2019 Christian Brauner <christian.brauner@ubuntu.com>.
+ * Copyright © 2019 Canonical Ltd.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+
+ * This library 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
+ * Lesser General Public License for more details.
+
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef __LXC_MEMORY_UTILS_H
+#define __LXC_MEMORY_UTILS_H
+
+#include <dirent.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "macro.h"
+
+static inline void __auto_free__(void *p)
+{
+ free(*(void **)p);
+}
+
+static inline void __auto_fclose__(FILE **f)
+{
+ if (*f)
+ fclose(*f);
+}
+
+static inline void __auto_closedir__(DIR **d)
+{
+ if (*d)
+ closedir(*d);
+}
+
+#define close_prot_errno_disarm(fd) \
+ if (fd >= 0) { \
+ int _e_ = errno; \
+ close(fd); \
+ errno = _e_; \
+ fd = -EBADF; \
+ }
+
+static inline void __auto_close__(int *fd)
+{
+ close_prot_errno_disarm(*fd);
+}
+
+#define __do_close_prot_errno __attribute__((__cleanup__(__auto_close__)))
+#define __do_free __attribute__((__cleanup__(__auto_free__)))
+#define __do_fclose __attribute__((__cleanup__(__auto_fclose__)))
+#define __do_closedir __attribute__((__cleanup__(__auto_closedir__)))
+
+#endif /* __LXC_MEMORY_UTILS_H */
* Copyright © 2019 Christian Brauner <christian.brauner@ubuntu.com>.
* Copyright © 2019 Canonical Ltd.
*
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2, as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+
+ * This library 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.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <unistd.h>
#include "config.h"
#include "file_utils.h"
+#include "macro.h"
+#include "memory_utils.h"
#include "raw_syscalls.h"
#include "string_utils.h"
#include "syscall_wrappers.h"
return num;
}
-static int parse_exec_params(char ***argv, char ***envp)
+static int parse_argv(char ***argv)
{
+ __do_free char *cmdline = NULL;
int ret;
- char *cmdline = NULL, *env = NULL;
- size_t cmdline_size, env_size;
+ size_t cmdline_size;
cmdline = file_to_buf("/proc/self/cmdline", &cmdline_size);
if (!cmdline)
- goto on_error;
-
- env = file_to_buf("/proc/self/environ", &env_size);
- if (!env)
- goto on_error;
+ return -1;
ret = push_vargs(cmdline, cmdline_size, argv);
if (ret <= 0)
- goto on_error;
-
- ret = push_vargs(env, env_size, envp);
- if (ret <= 0)
- goto on_error;
+ return -1;
+ move_ptr(cmdline);
return 0;
-
-on_error:
- free(env);
- free(cmdline);
-
- return -1;
}
static int is_memfd(void)
{
- int fd, saved_errno, seals;
+ __do_close_prot_errno int fd = -EBADF;
+ int seals;
fd = open("/proc/self/exe", O_RDONLY | O_CLOEXEC);
if (fd < 0)
return -ENOTRECOVERABLE;
seals = fcntl(fd, F_GET_SEALS);
- saved_errno = errno;
- close(fd);
- errno = saved_errno;
- if (seals < 0)
+ if (seals < 0) {
+ struct stat s = {0};
+
+ if (fstat(fd, &s) == 0)
+ return (s.st_nlink == 0);
+
return -EINVAL;
+ }
return seals == LXC_MEMFD_REXEC_SEALS;
}
static void lxc_rexec_as_memfd(char **argv, char **envp, const char *memfd_name)
{
- int saved_errno;
- ssize_t bytes_sent;
- int fd = -1, memfd = -1;
+ __do_close_prot_errno int execfd = -EBADF, fd = -EBADF, memfd = -EBADF,
+ tmpfd = -EBADF;
+ int ret;
+ ssize_t bytes_sent = 0;
+ struct stat st = {0};
memfd = memfd_create(memfd_name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
- if (memfd < 0)
- return;
+ if (memfd < 0) {
+ char template[PATH_MAX];
+
+ ret = snprintf(template, sizeof(template),
+ P_tmpdir "/.%s_XXXXXX", memfd_name);
+ if (ret < 0 || (size_t)ret >= sizeof(template))
+ return;
+
+ tmpfd = lxc_make_tmpfile(template, true);
+ if (tmpfd < 0)
+ return;
+
+ ret = fchmod(tmpfd, 0700);
+ if (ret)
+ return;
+ }
fd = open("/proc/self/exe", O_RDONLY | O_CLOEXEC);
if (fd < 0)
- goto on_error;
+ return;
/* sendfile() handles up to 2GB. */
- bytes_sent = lxc_sendfile_nointr(memfd, fd, NULL, LXC_SENDFILE_MAX);
- saved_errno = errno;
- close(fd);
- errno = saved_errno;
- if (bytes_sent < 0)
- goto on_error;
-
- if (fcntl(memfd, F_ADD_SEALS, LXC_MEMFD_REXEC_SEALS))
- goto on_error;
-
- fexecve(memfd, argv, envp);
-
-on_error:
- saved_errno = errno;
- close(memfd);
- errno = saved_errno;
+ ret = fstat(fd, &st);
+ if (ret)
+ return;
+
+ while (bytes_sent < st.st_size) {
+ ssize_t sent;
+
+ sent = lxc_sendfile_nointr(memfd >= 0 ? memfd : tmpfd, fd, NULL,
+ st.st_size - bytes_sent);
+ if (sent < 0) {
+ /* Fallback to shoveling data between kernel- and
+ * userspace.
+ */
+ lseek(fd, 0, SEEK_SET);
+ if (fd_to_fd(fd, memfd >= 0 ? memfd : tmpfd))
+ break;
+
+ return;
+ }
+ bytes_sent += sent;
+ }
+ close_prot_errno_disarm(fd);
+
+ if (memfd >= 0) {
+ if (fcntl(memfd, F_ADD_SEALS, LXC_MEMFD_REXEC_SEALS))
+ return;
+
+ execfd = memfd;
+ } else {
+ char procfd[LXC_PROC_PID_FD_LEN];
+
+ ret = snprintf(procfd, sizeof(procfd), "/proc/self/fd/%d", tmpfd);
+ if (ret < 0 || (size_t)ret >= sizeof(procfd))
+ return;
+
+ execfd = open(procfd, O_PATH | O_CLOEXEC);
+ close_prot_errno_disarm(tmpfd);
+
+ }
+ if (execfd < 0)
+ return;
+
+ fexecve(execfd, argv, envp);
}
-static int lxc_rexec(const char *memfd_name)
+/*
+ * Get cheap access to the environment. This must be declared by the user as
+ * mandated by POSIX. The definition is located in unistd.h.
+ */
+extern char **environ;
+
+int lxc_rexec(const char *memfd_name)
{
int ret;
- char **argv = NULL, **envp = NULL;
+ char **argv = NULL;
ret = is_memfd();
if (ret < 0 && ret == -ENOTRECOVERABLE) {
return 0;
}
- ret = parse_exec_params(&argv, &envp);
+ ret = parse_argv(&argv);
if (ret < 0) {
fprintf(stderr,
"%s - Failed to parse command line parameters\n",
return -1;
}
- lxc_rexec_as_memfd(argv, envp, memfd_name);
+ lxc_rexec_as_memfd(argv, environ, memfd_name);
fprintf(stderr, "%s - Failed to rexec as memfd\n", strerror(errno));
return -1;
}
*/
__attribute__((constructor)) static void liblxc_rexec(void)
{
- if (lxc_rexec("liblxc")) {
+ if (getenv("LXC_MEMFD_REXEC") && lxc_rexec("liblxc")) {
fprintf(stderr, "Failed to re-execute liblxc via memory file descriptor\n");
_exit(EXIT_FAILURE);
}
--- /dev/null
+/* liblxcapi
+ *
+ * Copyright © 2019 Christian Brauner <christian.brauner@ubuntu.com>.
+ * Copyright © 2019 Canonical Ltd.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+
+ * This library 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
+ * Lesser General Public License for more details.
+
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef __LXC_REXEC_H
+#define __LXC_REXEC_H
+
+extern int lxc_rexec(const char *memfd_name);
+
+#endif /* __LXC_REXEC_H */
#include "config.h"
#include "confile.h"
#include "log.h"
+#include "rexec.h"
#include "utils.h"
lxc_log_define(lxc_attach, lxc);
+/**
+ * This function will copy any binary that calls liblxc into a memory file and
+ * will use the memfd to rexecute the binary. This is done to prevent attacks
+ * through the /proc/self/exe symlink to corrupt the host binary when host and
+ * container are in the same user namespace or have set up an identity id
+ * mapping: CVE-2019-5736.
+ */
+#ifdef ENFORCE_MEMFD_REXEC
+__attribute__((constructor)) static void lxc_attach_rexec(void)
+{
+ if (!getenv("LXC_MEMFD_REXEC") && lxc_rexec("lxc-attach")) {
+ fprintf(stderr, "Failed to re-execute lxc-attach via memory file descriptor\n");
+ _exit(EXIT_FAILURE);
+ }
+}
+#endif
+
static int my_parser(struct lxc_arguments *args, int c, char *arg);
static int add_to_simple_array(char ***array, ssize_t *capacity, char *value);
static bool stdfd_is_pty(void);
projects / thirdparty / lxc.git / commitdiff
