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Systemd/src/nspawn/nspawn-settings.c
Lennart Poettering 960e4569e1 nspawn: implement configurable syscall whitelisting/blacklisting 
Now that we have ported nspawn's seccomp code to the generic code in
seccomp-util, let's extend it to support whitelisting and blacklisting
of specific additional syscalls.

This uses similar syntax as PID1's support for system call filtering,
but in contrast to that always implements a blacklist (and not a
whitelist), as we prepopulate the filter with a blacklist, and the
unit's system call filter logic does not come with anything
prepopulated.

(Later on we might actually want to invert the logic here, and
whitelist rather than blacklist things, but at this point let's not do
that. In case we switch this over later, the syscall add/remove logic of
this commit should be compatible conceptually.)

Fixes: #5163

Replaces: #5944
2017-09-12 14:06:21 +02:00

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/***
This file is part of systemd.
Copyright 2015 Lennart Poettering
systemd 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.
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include "alloc-util.h"
#include "cap-list.h"
#include "conf-parser.h"
#include "nspawn-network.h"
#include "nspawn-settings.h"
#include "parse-util.h"
#include "process-util.h"
#include "socket-util.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
#include "util.h"
int settings_load(FILE *f, const char *path, Settings **ret) {
_cleanup_(settings_freep) Settings *s = NULL;
int r;
assert(path);
assert(ret);
s = new0(Settings, 1);
if (!s)
return -ENOMEM;
s->start_mode = _START_MODE_INVALID;
s->personality = PERSONALITY_INVALID;
s->userns_mode = _USER_NAMESPACE_MODE_INVALID;
s->uid_shift = UID_INVALID;
s->uid_range = UID_INVALID;
s->read_only = -1;
s->volatile_mode = _VOLATILE_MODE_INVALID;
s->userns_chown = -1;
s->private_network = -1;
s->network_veth = -1;
r = config_parse(NULL, path, f,
"Exec\0"
"Network\0"
"Files\0",
config_item_perf_lookup, nspawn_gperf_lookup,
false,
false,
true,
s);
if (r < 0)
return r;
/* Make sure that if userns_mode is set, userns_chown is set to something appropriate, and vice versa. Either
* both fields shall be initialized or neither. */
if (s->userns_mode == USER_NAMESPACE_PICK)
s->userns_chown = true;
else if (s->userns_mode != _USER_NAMESPACE_MODE_INVALID && s->userns_chown < 0)
s->userns_chown = false;
if (s->userns_chown >= 0 && s->userns_mode == _USER_NAMESPACE_MODE_INVALID)
s->userns_mode = USER_NAMESPACE_NO;
*ret = s;
s = NULL;
return 0;
}
Settings* settings_free(Settings *s) {
if (!s)
return NULL;
strv_free(s->parameters);
strv_free(s->environment);
free(s->user);
free(s->pivot_root_new);
free(s->pivot_root_old);
free(s->working_directory);
strv_free(s->syscall_whitelist);
strv_free(s->syscall_blacklist);
strv_free(s->network_interfaces);
strv_free(s->network_macvlan);
strv_free(s->network_ipvlan);
strv_free(s->network_veth_extra);
free(s->network_bridge);
free(s->network_zone);
expose_port_free_all(s->expose_ports);
custom_mount_free_all(s->custom_mounts, s->n_custom_mounts);
return mfree(s);
}
bool settings_private_network(Settings *s) {
assert(s);
return
s->private_network > 0 ||
s->network_veth > 0 ||
s->network_bridge ||
s->network_zone ||
s->network_interfaces ||
s->network_macvlan ||
s->network_ipvlan ||
s->network_veth_extra;
}
bool settings_network_veth(Settings *s) {
assert(s);
return
s->network_veth > 0 ||
s->network_bridge ||
s->network_zone;
}
DEFINE_CONFIG_PARSE_ENUM(config_parse_volatile_mode, volatile_mode, VolatileMode, "Failed to parse volatile mode");
int config_parse_expose_port(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *s = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = expose_port_parse(&s->expose_ports, rvalue);
if (r == -EEXIST) {
log_syntax(unit, LOG_ERR, filename, line, r, "Duplicate port specification, ignoring: %s", rvalue);
return 0;
}
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse host port %s: %m", rvalue);
return 0;
}
return 0;
}
int config_parse_capability(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
uint64_t u = 0, *result = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
for (;;) {
_cleanup_free_ char *word = NULL;
int cap;
r = extract_first_word(&rvalue, &word, NULL, 0);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Failed to extract capability string, ignoring: %s", rvalue);
return 0;
}
if (r == 0)
break;
cap = capability_from_name(word);
if (cap < 0) {
log_syntax(unit, LOG_ERR, filename, line, 0, "Failed to parse capability, ignoring: %s", word);
continue;
}
u |= 1 << ((uint64_t) cap);
}
if (u == 0)
return 0;
*result |= u;
return 0;
}
int config_parse_id128(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
sd_id128_t t, *result = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = sd_id128_from_string(rvalue, &t);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse 128bit ID/UUID, ignoring: %s", rvalue);
return 0;
}
*result = t;
return 0;
}
int config_parse_pivot_root(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = pivot_root_parse(&settings->pivot_root_new, &settings->pivot_root_old, rvalue);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Invalid pivot root mount specification %s: %m", rvalue);
return 0;
}
return 0;
}
int config_parse_bind(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = bind_mount_parse(&settings->custom_mounts, &settings->n_custom_mounts, rvalue, ltype);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Invalid bind mount specification %s: %m", rvalue);
return 0;
}
return 0;
}
int config_parse_tmpfs(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = tmpfs_mount_parse(&settings->custom_mounts, &settings->n_custom_mounts, rvalue);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Invalid temporary file system specification %s: %m", rvalue);
return 0;
}
return 0;
}
int config_parse_overlay(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = overlay_mount_parse(&settings->custom_mounts, &settings->n_custom_mounts, rvalue, ltype);
if (r < 0)
log_syntax(unit, LOG_ERR, filename, line, r, "Invalid overlay file system specification %s, ignoring: %m", rvalue);
return 0;
}
int config_parse_veth_extra(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = veth_extra_parse(&settings->network_veth_extra, rvalue);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Invalid extra virtual Ethernet link specification %s: %m", rvalue);
return 0;
}
return 0;
}
int config_parse_network_zone(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
_cleanup_free_ char *j = NULL;
assert(filename);
assert(lvalue);
assert(rvalue);
j = strappend("vz-", rvalue);
if (!ifname_valid(j)) {
log_syntax(unit, LOG_ERR, filename, line, 0, "Invalid network zone name %s, ignoring: %m", rvalue);
return 0;
}
free(settings->network_zone);
settings->network_zone = j;
j = NULL;
return 0;
}
int config_parse_boot(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = parse_boolean(rvalue);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse Boot= parameter %s, ignoring: %m", rvalue);
return 0;
}
if (r > 0) {
if (settings->start_mode == START_PID2)
goto conflict;
settings->start_mode = START_BOOT;
} else {
if (settings->start_mode == START_BOOT)
goto conflict;
if (settings->start_mode < 0)
settings->start_mode = START_PID1;
}
return 0;
conflict:
log_syntax(unit, LOG_ERR, filename, line, r, "Conflicting Boot= or ProcessTwo= setting found. Ignoring.");
return 0;
}
int config_parse_pid2(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = parse_boolean(rvalue);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse ProcessTwo= parameter %s, ignoring: %m", rvalue);
return 0;
}
if (r > 0) {
if (settings->start_mode == START_BOOT)
goto conflict;
settings->start_mode = START_PID2;
} else {
if (settings->start_mode == START_PID2)
goto conflict;
if (settings->start_mode < 0)
settings->start_mode = START_PID1;
}
return 0;
conflict:
log_syntax(unit, LOG_ERR, filename, line, r, "Conflicting Boot= or ProcessTwo= setting found. Ignoring.");
return 0;
}
int config_parse_private_users(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = parse_boolean(rvalue);
if (r == 0) {
/* no: User namespacing off */
settings->userns_mode = USER_NAMESPACE_NO;
settings->uid_shift = UID_INVALID;
settings->uid_range = UINT32_C(0x10000);
} else if (r > 0) {
/* yes: User namespacing on, UID range is read from root dir */
settings->userns_mode = USER_NAMESPACE_FIXED;
settings->uid_shift = UID_INVALID;
settings->uid_range = UINT32_C(0x10000);
} else if (streq(rvalue, "pick")) {
/* pick: User namespacing on, UID range is picked randomly */
settings->userns_mode = USER_NAMESPACE_PICK;
settings->uid_shift = UID_INVALID;
settings->uid_range = UINT32_C(0x10000);
} else {
const char *range, *shift;
uid_t sh, rn;
/* anything else: User namespacing on, UID range is explicitly configured */
range = strchr(rvalue, ':');
if (range) {
shift = strndupa(rvalue, range - rvalue);
range++;
r = safe_atou32(range, &rn);
if (r < 0 || rn <= 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "UID/GID range invalid, ignoring: %s", range);
return 0;
}
} else {
shift = rvalue;
rn = UINT32_C(0x10000);
}
r = parse_uid(shift, &sh);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "UID/GID shift invalid, ignoring: %s", range);
return 0;
}
settings->userns_mode = USER_NAMESPACE_FIXED;
settings->uid_shift = sh;
settings->uid_range = rn;
}
return 0;
}
int config_parse_syscall_filter(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
bool negative;
const char *items;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
negative = rvalue[0] == '~';
items = negative ? rvalue + 1 : rvalue;
for (;;) {
_cleanup_free_ char *word = NULL;
r = extract_first_word(&items, &word, NULL, 0);
if (r == 0)
break;
if (r == -ENOMEM)
return log_oom();
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse SystemCallFilter= parameter %s, ignoring: %m", rvalue);
return 0;
}
if (negative)
r = strv_extend(&settings->syscall_blacklist, word);
else
r = strv_extend(&settings->syscall_whitelist, word);
if (r < 0)
return log_oom();
}
return 0;
}
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