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Copy pathisolate.c
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1630 lines (1427 loc) · 36.3 KB
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/*
* A Process Isolator based on Linux Containers
*
* (c) 2012-2015 Martin Mares <mj@ucw.cz>
* (c) 2012-2014 Bernard Blackham <bernard@blackham.com.au>
*/
#define _GNU_SOURCE
#include "config.h"
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <stdint.h>
#include <unistd.h>
#include <getopt.h>
#include <sched.h>
#include <time.h>
#include <ftw.h>
#include <grp.h>
#include <mntent.h>
#include <limits.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/signal.h>
#include <sys/resource.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/quota.h>
#include <sys/vfs.h>
#include <sys/fsuid.h>
/* May not be defined in older glibc headers */
#ifndef MS_PRIVATE
#warning "Working around old glibc: no MS_PRIVATE"
#define MS_PRIVATE (1 << 18)
#endif
#ifndef MS_REC
#warning "Working around old glibc: no MS_REC"
#define MS_REC (1 << 14)
#endif
#define NONRET __attribute__((noreturn))
#define UNUSED __attribute__((unused))
#define ARRAY_SIZE(a) (int)(sizeof(a)/sizeof(a[0]))
static int timeout; /* milliseconds */
static int wall_timeout;
static int extra_timeout;
static int pass_environ;
static int verbose;
static int fsize_limit;
static int memory_limit;
static int stack_limit;
static int block_quota;
static int inode_quota;
static int max_processes = 1;
static char *redir_stdin, *redir_stdout, *redir_stderr;
static char *set_cwd;
static int share_net;
static int cg_enable;
static int cg_memory_limit;
static int cg_timing;
static int box_id;
static char box_dir[1024];
static pid_t box_pid;
static uid_t box_uid;
static gid_t box_gid;
static uid_t orig_uid;
static gid_t orig_gid;
static int partial_line;
static int cleanup_ownership;
static struct timeval start_time;
static int ticks_per_sec;
static int total_ms, wall_ms;
static volatile sig_atomic_t timer_tick;
static int error_pipes[2];
static int write_errors_to_fd;
static int read_errors_from_fd;
static void die(char *msg, ...) NONRET;
static void cg_stats(void);
static int get_wall_time_ms(void);
static int get_run_time_ms(struct rusage *rus);
static void chowntree(char *path, uid_t uid, gid_t gid);
/*** Meta-files ***/
static FILE *metafile;
static void
meta_open(const char *name)
{
if (!strcmp(name, "-"))
{
metafile = stdout;
return;
}
if (setfsuid(getuid()) < 0)
die("Failed to switch FS UID: %m");
metafile = fopen(name, "w");
if (setfsuid(geteuid()) < 0)
die("Failed to switch FS UID back: %m");
if (!metafile)
die("Failed to open metafile '%s'",name);
}
static void
meta_close(void)
{
if (metafile && metafile != stdout)
fclose(metafile);
}
static void __attribute__((format(printf,1,2)))
meta_printf(const char *fmt, ...)
{
if (!metafile)
return;
va_list args;
va_start(args, fmt);
vfprintf(metafile, fmt, args);
va_end(args);
}
static void
final_stats(struct rusage *rus)
{
total_ms = get_run_time_ms(rus);
wall_ms = get_wall_time_ms();
meta_printf("time:%d.%03d\n", total_ms/1000, total_ms%1000);
meta_printf("time-wall:%d.%03d\n", wall_ms/1000, wall_ms%1000);
meta_printf("max-rss:%ld\n", rus->ru_maxrss);
meta_printf("csw-voluntary:%ld\n", rus->ru_nvcsw);
meta_printf("csw-forced:%ld\n", rus->ru_nivcsw);
cg_stats();
}
/*** Messages and exits ***/
static void NONRET
box_exit(int rc)
{
if (box_pid > 0)
{
kill(-box_pid, SIGKILL);
kill(box_pid, SIGKILL);
meta_printf("killed:1\n");
struct rusage rus;
int p, stat;
do
p = wait4(box_pid, &stat, 0, &rus);
while (p < 0 && errno == EINTR);
if (p < 0)
fprintf(stderr, "UGH: Lost track of the process (%m)\n");
else
final_stats(&rus);
}
if (rc < 2 && cleanup_ownership)
chowntree("box", orig_uid, orig_gid);
meta_close();
exit(rc);
}
static void
flush_line(void)
{
if (partial_line)
fputc('\n', stderr);
partial_line = 0;
}
/* Report an error of the sandbox itself */
static void NONRET __attribute__((format(printf,1,2)))
die(char *msg, ...)
{
va_list args;
va_start(args, msg);
char buf[1024];
int n = vsnprintf(buf, sizeof(buf), msg, args);
if (write_errors_to_fd)
{
// We are inside the box, have to use error pipe for error reporting.
// We hope that the whole error message fits in PIPE_BUF bytes.
write(write_errors_to_fd, buf, n);
exit(2);
}
// Otherwise, we in the box keeper process, so we report errors normally
flush_line();
meta_printf("status:XX\nmessage:%s\n", buf);
fputs(buf, stderr);
fputc('\n', stderr);
box_exit(2);
}
/* Report an error of the program inside the sandbox */
static void NONRET __attribute__((format(printf,1,2)))
err(char *msg, ...)
{
va_list args;
va_start(args, msg);
flush_line();
if (msg[0] && msg[1] && msg[2] == ':' && msg[3] == ' ')
{
meta_printf("status:%c%c\n", msg[0], msg[1]);
msg += 4;
}
char buf[1024];
vsnprintf(buf, sizeof(buf), msg, args);
meta_printf("message:%s\n", buf);
fputs(buf, stderr);
fputc('\n', stderr);
box_exit(1);
}
/* Write a message, but only if in verbose mode */
static void __attribute__((format(printf,1,2)))
msg(char *msg, ...)
{
va_list args;
va_start(args, msg);
if (verbose)
{
int len = strlen(msg);
if (len > 0)
partial_line = (msg[len-1] != '\n');
vfprintf(stderr, msg, args);
fflush(stderr);
}
va_end(args);
}
/*** Utility functions ***/
static void *
xmalloc(size_t size)
{
void *p = malloc(size);
if (!p)
die("Out of memory");
return p;
}
static char *
xstrdup(char *str)
{
char *p = strdup(str);
if (!p)
die("Out of memory");
return p;
}
static int dir_exists(char *path)
{
struct stat st;
return (stat(path, &st) >= 0 && S_ISDIR(st.st_mode));
}
static int rmtree_helper(const char *fpath, const struct stat *sb,
int typeflag UNUSED, struct FTW *ftwbuf UNUSED)
{
if (S_ISDIR(sb->st_mode))
{
if (rmdir(fpath) < 0)
die("Cannot rmdir %s: %m", fpath);
}
else
{
if (unlink(fpath) < 0)
die("Cannot unlink %s: %m", fpath);
}
return FTW_CONTINUE;
}
static void
rmtree(char *path)
{
nftw(path, rmtree_helper, 32, FTW_MOUNT | FTW_PHYS | FTW_DEPTH);
}
static uid_t chown_uid;
static gid_t chown_gid;
static int chowntree_helper(const char *fpath, const struct stat *sb UNUSED,
int typeflag UNUSED, struct FTW *ftwbuf UNUSED)
{
if (lchown(fpath, chown_uid, chown_gid) < 0)
die("Cannot chown %s: %m", fpath);
else
return FTW_CONTINUE;
}
static void
chowntree(char *path, uid_t uid, gid_t gid)
{
chown_uid = uid;
chown_gid = gid;
nftw(path, chowntree_helper, 32, FTW_MOUNT | FTW_PHYS);
}
/*** Environment rules ***/
struct env_rule {
char *var; // Variable to match
char *val; // ""=clear, NULL=inherit
int var_len;
struct env_rule *next;
};
static struct env_rule *first_env_rule;
static struct env_rule **last_env_rule = &first_env_rule;
static struct env_rule default_env_rules[] = {
{ "LIBC_FATAL_STDERR_", "1" }
};
static int
set_env_action(char *a0)
{
struct env_rule *r = xmalloc(sizeof(*r) + strlen(a0) + 1);
char *a = (char *)(r+1);
strcpy(a, a0);
char *sep = strchr(a, '=');
if (sep == a)
return 0;
r->var = a;
if (sep)
{
*sep++ = 0;
r->val = sep;
}
else
r->val = NULL;
*last_env_rule = r;
last_env_rule = &r->next;
r->next = NULL;
return 1;
}
static int
match_env_var(char *env_entry, struct env_rule *r)
{
if (strncmp(env_entry, r->var, r->var_len))
return 0;
return (env_entry[r->var_len] == '=');
}
static void
apply_env_rule(char **env, int *env_sizep, struct env_rule *r)
{
// First remove the variable if already set
int pos = 0;
while (pos < *env_sizep && !match_env_var(env[pos], r))
pos++;
if (pos < *env_sizep)
{
(*env_sizep)--;
env[pos] = env[*env_sizep];
env[*env_sizep] = NULL;
}
// What is the new value?
char *new;
if (r->val)
{
if (!r->val[0])
return;
new = xmalloc(r->var_len + 1 + strlen(r->val) + 1);
sprintf(new, "%s=%s", r->var, r->val);
}
else
{
pos = 0;
while (environ[pos] && !match_env_var(environ[pos], r))
pos++;
if (!(new = environ[pos]))
return;
}
// Add it at the end of the array
env[(*env_sizep)++] = new;
env[*env_sizep] = NULL;
}
static char **
setup_environment(void)
{
// Link built-in rules with user rules
for (int i=ARRAY_SIZE(default_env_rules)-1; i >= 0; i--)
{
default_env_rules[i].next = first_env_rule;
first_env_rule = &default_env_rules[i];
}
// Scan the original environment
char **orig_env = environ;
int orig_size = 0;
while (orig_env[orig_size])
orig_size++;
// For each rule, reserve one more slot and calculate length
int num_rules = 0;
for (struct env_rule *r = first_env_rule; r; r=r->next)
{
num_rules++;
r->var_len = strlen(r->var);
}
// Create a new environment
char **env = xmalloc((orig_size + num_rules + 1) * sizeof(char *));
int size;
if (pass_environ)
{
memcpy(env, environ, orig_size * sizeof(char *));
size = orig_size;
}
else
size = 0;
env[size] = NULL;
// Apply the rules one by one
for (struct env_rule *r = first_env_rule; r; r=r->next)
apply_env_rule(env, &size, r);
// Return the new env and pass some gossip
if (verbose > 1)
{
fprintf(stderr, "Passing environment:\n");
for (int i=0; env[i]; i++)
fprintf(stderr, "\t%s\n", env[i]);
}
return env;
}
/*** Directory rules ***/
struct dir_rule {
char *inside; // A relative path
char *outside; // This can be an absolute path or a relative path starting with "./"
unsigned int flags; // DIR_FLAG_xxx
struct dir_rule *next;
};
enum dir_rule_flags {
DIR_FLAG_RW = 1,
DIR_FLAG_NOEXEC = 2,
DIR_FLAG_FS = 4,
DIR_FLAG_MAYBE = 8,
DIR_FLAG_DEV = 16,
};
static const char * const dir_flag_names[] = { "rw", "noexec", "fs", "maybe", "dev" };
static struct dir_rule *first_dir_rule;
static struct dir_rule **last_dir_rule = &first_dir_rule;
static int add_dir_rule(char *in, char *out, unsigned int flags)
{
// Make sure that "in" is relative
while (in[0] == '/')
in++;
if (!*in)
return 0;
// Check "out"
if (flags & DIR_FLAG_FS)
{
if (!out || out[0] == '/')
return 0;
}
else
{
if (out && out[0] != '/' && strncmp(out, "./", 2))
return 0;
}
// Override an existing rule
struct dir_rule *r;
for (r = first_dir_rule; r; r = r->next)
if (!strcmp(r->inside, in))
break;
// Add a new rule
if (!r)
{
r = xmalloc(sizeof(*r));
r->inside = in;
*last_dir_rule = r;
last_dir_rule = &r->next;
r->next = NULL;
}
r->outside = out;
r->flags = flags;
return 1;
}
static unsigned int parse_dir_option(char *opt)
{
for (unsigned int i = 0; i < ARRAY_SIZE(dir_flag_names); i++)
if (!strcmp(opt, dir_flag_names[i]))
return 1U << i;
die("Unknown directory option %s", opt);
}
static int set_dir_action(char *arg)
{
arg = xstrdup(arg);
char *colon = strchr(arg, ':');
unsigned int flags = 0;
while (colon)
{
*colon++ = 0;
char *next = strchr(colon, ':');
if (next)
*next = 0;
flags |= parse_dir_option(colon);
colon = next;
}
char *eq = strchr(arg, '=');
if (eq)
{
*eq++ = 0;
return add_dir_rule(arg, (*eq ? eq : NULL), flags);
}
else
{
char *out = xmalloc(1 + strlen(arg) + 1);
sprintf(out, "/%s", arg);
return add_dir_rule(arg, out, flags);
}
}
static void init_dir_rules(void)
{
set_dir_action("box=./box:rw");
set_dir_action("bin");
set_dir_action("dev:dev");
set_dir_action("lib");
set_dir_action("lib64:maybe");
set_dir_action("proc=proc:fs");
set_dir_action("usr");
}
static void make_dir(char *path)
{
char *sep = (path[0] == '/' ? path+1 : path);
for (;;)
{
sep = strchr(sep, '/');
if (sep)
*sep = 0;
if (!dir_exists(path) && mkdir(path, 0777) < 0)
die("Cannot create directory %s: %m\n", path);
if (!sep)
return;
*sep++ = '/';
}
}
static void apply_dir_rules(void)
{
for (struct dir_rule *r = first_dir_rule; r; r=r->next)
{
char *in = r->inside;
char *out = r->outside;
if (!out)
{
msg("Not binding anything on %s\n", r->inside);
continue;
}
if ((r->flags & DIR_FLAG_MAYBE) && !dir_exists(out))
{
msg("Not binding %s on %s (does not exist)\n", out, r->inside);
continue;
}
char root_in[1024];
snprintf(root_in, sizeof(root_in), "root/%s", in);
make_dir(root_in);
unsigned long mount_flags = 0;
if (!(r->flags & DIR_FLAG_RW))
mount_flags |= MS_RDONLY;
if (r->flags & DIR_FLAG_NOEXEC)
mount_flags |= MS_NOEXEC;
if (!(r->flags & DIR_FLAG_DEV))
mount_flags |= MS_NODEV;
if (r->flags & DIR_FLAG_FS)
{
msg("Mounting %s on %s (flags %lx)\n", out, in, mount_flags);
if (mount("none", root_in, out, mount_flags, "") < 0)
die("Cannot mount %s on %s: %m", out, in);
}
else
{
mount_flags |= MS_BIND | MS_NOSUID;
msg("Binding %s on %s (flags %lx)\n", out, in, mount_flags);
// Most mount flags need remount to work
if (mount(out, root_in, "none", mount_flags, "") < 0 ||
mount(out, root_in, "none", MS_REMOUNT | mount_flags, "") < 0)
die("Cannot mount %s on %s: %m", out, in);
}
}
}
/*** Control groups ***/
struct cg_controller_desc {
const char *name;
int optional;
};
typedef enum {
CG_MEMORY = 0,
CG_CPUACCT,
CG_CPUSET,
CG_NUM_CONTROLLERS,
} cg_controller;
static const struct cg_controller_desc cg_controllers[CG_NUM_CONTROLLERS+1] = {
[CG_MEMORY] = { "memory", 0 },
[CG_CPUACCT] = { "cpuacct", 0 },
[CG_CPUSET] = { "cpuset", 1 },
[CG_NUM_CONTROLLERS] = { NULL, 0 },
};
#define FOREACH_CG_CONTROLLER(_controller) \
for (cg_controller (_controller) = 0; \
(_controller) < CG_NUM_CONTROLLERS; (_controller)++)
static const char *cg_controller_name(cg_controller c)
{
return cg_controllers[c].name;
}
static int cg_controller_optional(cg_controller c)
{
return cg_controllers[c].optional;
}
static char cg_name[256];
#define CG_BUFSIZE 1024
static void
cg_makepath(char *buf, size_t len, cg_controller c, const char *attr)
{
const char *cg_root = CONFIG_ISOLATE_CGROUP_ROOT;
snprintf(buf, len, "%s/%s/%s/%s", cg_root, cg_controller_name(c), cg_name, attr);
}
static int
cg_read(cg_controller controller, const char *attr, char *buf)
{
int result = 0;
int maybe = 0;
if (attr[0] == '?')
{
attr++;
maybe = 1;
}
char path[256];
cg_makepath(path, sizeof(path), controller, attr);
int fd = open(path, O_RDONLY);
if (fd < 0)
{
if (maybe)
goto fail;
die("Cannot read %s: %m", path);
}
int n = read(fd, buf, CG_BUFSIZE);
if (n < 0)
{
if (maybe)
goto fail_close;
die("Cannot read %s: %m", path);
}
if (n >= CG_BUFSIZE - 1)
die("Attribute %s too long", path);
if (n > 0 && buf[n-1] == '\n')
n--;
buf[n] = 0;
if (verbose > 1)
msg("CG: Read %s = %s\n", attr, buf);
result = 1;
fail_close:
close(fd);
fail:
return result;
}
static void __attribute__((format(printf,3,4)))
cg_write(cg_controller controller, const char *attr, const char *fmt, ...)
{
int maybe = 0;
if (attr[0] == '?')
{
attr++;
maybe = 1;
}
va_list args;
va_start(args, fmt);
char buf[CG_BUFSIZE];
int n = vsnprintf(buf, sizeof(buf), fmt, args);
if (n >= CG_BUFSIZE)
die("cg_write: Value for attribute %s is too long", attr);
if (verbose > 1)
msg("CG: Write %s = %s", attr, buf);
char path[256];
cg_makepath(path, sizeof(path), controller, attr);
int fd = open(path, O_WRONLY | O_TRUNC);
if (fd < 0)
{
if (maybe)
goto fail;
else
die("Cannot write %s: %m", path);
}
int written = write(fd, buf, n);
if (written < 0)
{
if (maybe)
goto fail_close;
else
die("Cannot set %s to %s: %m", path, buf);
}
if (written != n)
die("Short write to %s (%d out of %d bytes)", path, written, n);
fail_close:
close(fd);
fail:
va_end(args);
}
static void
cg_init(void)
{
if (!cg_enable)
return;
char *cg_root = CONFIG_ISOLATE_CGROUP_ROOT;
if (!dir_exists(cg_root))
die("Control group filesystem at %s not mounted", cg_root);
snprintf(cg_name, sizeof(cg_name), "box-%d", box_id);
msg("Using control group %s\n", cg_name);
}
static void
cg_prepare(void)
{
if (!cg_enable)
return;
struct stat st;
char buf[CG_BUFSIZE];
char path[256];
FOREACH_CG_CONTROLLER(controller)
{
cg_makepath(path, sizeof(path), controller, "");
if (stat(path, &st) >= 0 || errno != ENOENT)
{
msg("Control group %s already exists, trying to empty it.\n", path);
if (rmdir(path) < 0)
die("Failed to reset control group %s: %m", path);
}
if (mkdir(path, 0777) < 0 && !cg_controller_optional(controller))
die("Failed to create control group %s: %m", path);
}
// If cpuset module is enabled, copy allowed cpus and memory nodes from parent group
if (cg_read(CG_CPUSET, "?cpuset.cpus", buf))
cg_write(CG_CPUSET, "cpuset.cpus", "%s", buf);
if (cg_read(CG_CPUSET, "?cpuset.mems", buf))
cg_write(CG_CPUSET, "cpuset.mems", "%s", buf);
}
static void
cg_enter(void)
{
if (!cg_enable)
return;
msg("Entering control group %s\n", cg_name);
FOREACH_CG_CONTROLLER(controller)
{
if (cg_controller_optional(controller))
cg_write(controller, "?tasks", "%d\n", (int) getpid());
else
cg_write(controller, "tasks", "%d\n", (int) getpid());
}
if (cg_memory_limit)
{
cg_write(CG_MEMORY, "memory.limit_in_bytes", "%lld\n", (long long) cg_memory_limit << 10);
cg_write(CG_MEMORY, "?memory.memsw.limit_in_bytes", "%lld\n", (long long) cg_memory_limit << 10);
}
if (cg_timing)
cg_write(CG_CPUACCT, "cpuacct.usage", "0\n");
}
static int
cg_get_run_time_ms(void)
{
if (!cg_enable)
return 0;
char buf[CG_BUFSIZE];
cg_read(CG_CPUACCT, "cpuacct.usage", buf);
unsigned long long ns = atoll(buf);
return ns / 1000000;
}
static void
cg_stats(void)
{
if (!cg_enable)
return;
char buf[CG_BUFSIZE];
// Memory usage statistics
unsigned long long mem=0, memsw=0;
if (cg_read(CG_MEMORY, "?memory.max_usage_in_bytes", buf))
mem = atoll(buf);
if (cg_read(CG_MEMORY, "?memory.memsw.max_usage_in_bytes", buf))
{
memsw = atoll(buf);
if (memsw > mem)
mem = memsw;
}
if (mem)
meta_printf("cg-mem:%lld\n", mem >> 10);
}
static void
cg_remove(void)
{
char buf[CG_BUFSIZE];
if (!cg_enable)
return;
FOREACH_CG_CONTROLLER(controller)
{
if (cg_controller_optional(controller))
{
if (!cg_read(controller, "?tasks", buf))
continue;
}
else
cg_read(controller, "tasks", buf);
if (buf[0])
die("Some tasks left in controller %s of cgroup %s, failed to remove it",
cg_controller_name(controller), cg_name);
char path[256];
cg_makepath(path, sizeof(path), controller, "");
if (rmdir(path) < 0)
die("Cannot remove control group %s: %m", path);
}
}
/*** Disk quotas ***/
static int
path_begins_with(char *path, char *with)
{
while (*with)
if (*path++ != *with++)
return 0;
return (!*with || *with == '/');
}
static char *
find_device(char *path)
{
FILE *f = setmntent("/proc/mounts", "r");
if (!f)
die("Cannot open /proc/mounts: %m");
struct mntent *me;
int best_len = 0;
char *best_dev = NULL;
while (me = getmntent(f))
{
if (!path_begins_with(me->mnt_fsname, "/dev"))
continue;
if (path_begins_with(path, me->mnt_dir))
{
int len = strlen(me->mnt_dir);
if (len > best_len)
{
best_len = len;
free(best_dev);
best_dev = xstrdup(me->mnt_fsname);
}
}
}
endmntent(f);
return best_dev;
}
static void
set_quota(void)
{
if (!block_quota)
return;
char cwd[PATH_MAX];
if (!getcwd(cwd, sizeof(cwd)))
die("getcwd: %m");
char *dev = find_device(cwd);
if (!dev)
die("Cannot identify filesystem which contains %s", cwd);
msg("Quota: Mapped path %s to a filesystem on %s\n", cwd, dev);
// Sanity check
struct stat dev_st, cwd_st;
if (stat(dev, &dev_st) < 0)
die("Cannot identify block device %s: %m", dev);
if (!S_ISBLK(dev_st.st_mode))
die("Expected that %s is a block device", dev);
if (stat(".", &cwd_st) < 0)
die("Cannot stat cwd: %m");
if (cwd_st.st_dev != dev_st.st_rdev)
die("Identified %s as a filesystem on %s, but it is obviously false", cwd, dev);
struct dqblk dq = {
.dqb_bhardlimit = block_quota,
.dqb_bsoftlimit = block_quota,
.dqb_ihardlimit = inode_quota,
.dqb_isoftlimit = inode_quota,
.dqb_valid = QIF_LIMITS,
};
if (quotactl(QCMD(Q_SETQUOTA, USRQUOTA), dev, box_uid, (caddr_t) &dq) < 0)
die("Cannot set disk quota: %m");
msg("Quota: Set block quota %d and inode quota %d\n", block_quota, inode_quota);
free(dev);
}
/*** The keeper process ***/
static void
signal_alarm(int unused UNUSED)
{
/* Time limit checks are synchronous, so we only schedule them there. */
timer_tick = 1;
alarm(1);
}
static void
signal_int(int signum)