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core: add pre-defined syscall groups to SystemCallFilter= (#3053) (#3157)

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Implement sets of system calls to help constructing system call
filters. A set starts with '@' to distinguish from a system call.

Closes: #3053, #3157
This commit is contained in:
Topi Miettinen 2016-06-01 09:56:01 +00:00 committed by Lennart Poettering
parent ce3eb7790c
commit 201c1cc22a
4 changed files with 350 additions and 41 deletions
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73
man/systemd.exec.xml
View File

@ -1193,7 +1193,78 @@
<function>read</function> and <function>write</function>, and
right after it add a blacklisting of
<function>write</function>, then <function>write</function>
will be removed from the set.) </para></listitem>
will be removed from the set.)</para>
<para>As the number of possible system
calls is large, predefined sets of system calls are provided.
A set starts with <literal>@</literal> character, followed by
name of the set.
<table>
<title>Currently predefined system call sets</title>
<tgroup cols='2'>
<colspec colname='set' />
<colspec colname='description' />
<thead>
<row>
<entry>Set</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>@clock</entry>
<entry>System calls for changing the system clock (<function>adjtimex()</function>,
<function>settimeofday()</function>)</entry>
</row>
<row>
<entry>@io-event</entry>
<entry>Event loop use (<function>poll()</function>, <function>select()</function>,
<citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<function>eventfd()</function>...)</entry>
</row>
<row>
<entry>@ipc</entry>
<entry>SysV IPC, POSIX Message Queues or other IPC (<citerefentry project='man-pages'><refentrytitle>mq_overview</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>svipc</refentrytitle><manvolnum>7</manvolnum></citerefentry>)</entry>
</row>
<row>
<entry>@module</entry>
<entry>Kernel module control (<function>create_module()</function>, <function>init_module()</function>...)</entry>
</row>
<row>
<entry>@mount</entry>
<entry>File system mounting and unmounting (<function>chroot()</function>, <function>mount()</function>...)</entry>
</row>
<row>
<entry>@network-io</entry>
<entry>Socket I/O (including local AF_UNIX):
<citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry></entry>
</row>
<row>
<entry>@obsolete</entry>
<entry>Unusual, obsolete or unimplemented (<function>fattach()</function>, <function>gtty()</function>, <function>vm86()</function>...)</entry>
</row>
<row>
<entry>@privileged</entry>
<entry>All system calls which need superuser capabilities (<citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>)</entry>
</row>
<row>
<entry>@process</entry>
<entry>Process control, execution, namespaces (<function>execve()</function>, <function>kill()</function>, <citerefentry project='man-pages'><refentrytitle>namespaces</refentrytitle><manvolnum>7</manvolnum></citerefentry>...)</entry>
</row>
<row>
<entry>@raw-io</entry>
<entry>Raw I/O ports (<function>ioperm()</function>, <function>iopl()</function>, <function>pciconfig_read()</function>...)</entry>
</row>
</tbody>
</tgroup>
</table>
Note, that as new system calls are added to the kernel, additional system calls might be added to the groups
above, so the contents of the sets may change between systemd versions.</para></listitem>
</varlistentry>
<varlistentry>

91
src/core/load-fragment.c
View File

@ -2396,6 +2396,55 @@ int config_parse_documentation(const char *unit,
}
#ifdef HAVE_SECCOMP
static int syscall_filter_parse_one(
const char *unit,
const char *filename,
unsigned line,
ExecContext *c,
bool invert,
const char *t,
bool warn) {
int r;
if (*t == '@') {
const SystemCallFilterSet *set;
for (set = syscall_filter_sets; set->set_name; set++)
if (streq(set->set_name, t)) {
const char *sys;
NULSTR_FOREACH(sys, set->value) {
r = syscall_filter_parse_one(unit, filename, line, c, invert, sys, false);
if (r < 0)
return r;
}
break;
}
} else {
int id;
id = seccomp_syscall_resolve_name(t);
if (id < 0) {
if (warn)
log_syntax(unit, LOG_ERR, filename, line, 0, "Failed to parse system call, ignoring: %s", t);
return 0;
}
/* If we previously wanted to forbid a syscall and now
* we want to allow it, then remove it from the list
*/
if (!invert == c->syscall_whitelist) {
r = set_put(c->syscall_filter, INT_TO_PTR(id + 1));
if (r == 0)
return 0;
if (r < 0)
return log_oom();
} else
set_remove(c->syscall_filter, INT_TO_PTR(id + 1));
}
return 0;
}
int config_parse_syscall_filter(
const char *unit,
const char *filename,
@ -2408,13 +2457,6 @@ int config_parse_syscall_filter(
void *data,
void *userdata) {
static const char default_syscalls[] =
"execve\0"
"exit\0"
"exit_group\0"
"rt_sigreturn\0"
"sigreturn\0";
ExecContext *c = data;
Unit *u = userdata;
bool invert = false;
@ -2448,53 +2490,26 @@ int config_parse_syscall_filter(
/* Allow everything but the ones listed */
c->syscall_whitelist = false;
else {
const char *i;
/* Allow nothing but the ones listed */
c->syscall_whitelist = true;
/* Accept default syscalls if we are on a whitelist */
NULSTR_FOREACH(i, default_syscalls) {
int id;
id = seccomp_syscall_resolve_name(i);
if (id < 0)
continue;
r = set_put(c->syscall_filter, INT_TO_PTR(id + 1));
if (r == 0)
continue;
r = syscall_filter_parse_one(unit, filename, line, c, false, "@default", false);
if (r < 0)
return log_oom();
}
return r;
}
}
FOREACH_WORD_QUOTED(word, l, rvalue, state) {
_cleanup_free_ char *t = NULL;
int id;
t = strndup(word, l);
if (!t)
return log_oom();
id = seccomp_syscall_resolve_name(t);
if (id < 0) {
log_syntax(unit, LOG_ERR, filename, line, 0, "Failed to parse system call, ignoring: %s", t);
continue;
}
/* If we previously wanted to forbid a syscall and now
* we want to allow it, then remove it from the list
*/
if (!invert == c->syscall_whitelist) {
r = set_put(c->syscall_filter, INT_TO_PTR(id + 1));
if (r == 0)
continue;
r = syscall_filter_parse_one(unit, filename, line, c, invert, t, true);
if (r < 0)
return log_oom();
} else
set_remove(c->syscall_filter, INT_TO_PTR(id + 1));
return r;
}
if (!isempty(state))
log_syntax(unit, LOG_ERR, filename, line, 0, "Trailing garbage, ignoring.");

216
src/shared/seccomp-util.c
View File

@ -88,3 +88,219 @@ int seccomp_add_secondary_archs(scmp_filter_ctx *c) {
return 0;
}
const SystemCallFilterSet syscall_filter_sets[] = {
{
/* Clock */
.set_name = "@clock",
.value =
"adjtimex\0"
"settimeofday\0"
}, {
/* Default list */
.set_name = "@default",
.value =
"execve\0"
"exit\0"
"exit_group\0"
"rt_sigreturn\0"
"sigreturn\0"
}, {
/* Event loop use */
.set_name = "@io-event",
.value =
"_newselect\0"
"epoll_create1\0"
"epoll_create\0"
"epoll_ctl\0"
"epoll_ctl_old\0"
"epoll_pwait\0"
"epoll_wait\0"
"epoll_wait_old\0"
"eventfd2\0"
"eventfd\0"
"poll\0"
"ppoll\0"
"pselect6\0"
"select\0"
}, {
/* Message queues, SYSV IPC or other IPC: unusual */
.set_name = "@ipc",
.value = "ipc\0"
"mq_getsetattr\0"
"mq_notify\0"
"mq_open\0"
"mq_timedreceive\0"
"mq_timedsend\0"
"mq_unlink\0"
"msgctl\0"
"msgget\0"
"msgrcv\0"
"msgsnd\0"
"process_vm_readv\0"
"process_vm_writev\0"
"semctl\0"
"semget\0"
"semop\0"
"semtimedop\0"
"shmat\0"
"shmctl\0"
"shmdt\0"
"shmget\0"
}, {
/* Kernel module control */
.set_name = "@module",
.value =
"create_module\0"
"delete_module\0"
"finit_module\0"
"init_module\0"
}, {
/* Mounting */
.set_name = "@mount",
.value =
"chroot\0"
"mount\0"
"oldumount\0"
"pivot_root\0"
"umount2\0"
"umount\0"
}, {
/* Network or Unix socket IO, should not be needed if not network facing */
.set_name = "@network-io",
.value =
"accept4\0"
"accept\0"
"bind\0"
"connect\0"
"getpeername\0"
"getsockname\0"
"getsockopt\0"
"listen\0"
"recv\0"
"recvfrom\0"
"recvmmsg\0"
"recvmsg\0"
"send\0"
"sendmmsg\0"
"sendmsg\0"
"sendto\0"
"setsockopt\0"
"shutdown\0"
"socket\0"
"socketcall\0"
"socketpair\0"
}, {
/* Unusual, obsolete or unimplemented, some unknown even to libseccomp */
.set_name = "@obsolete",
.value =
"_sysctl\0"
"afs_syscall\0"
"break\0"
"fattach\0"
"fdetach\0"
"ftime\0"
"get_kernel_syms\0"
"get_mempolicy\0"
"getmsg\0"
"getpmsg\0"
"gtty\0"
"isastream\0"
"lock\0"
"madvise1\0"
"modify_ldt\0"
"mpx\0"
"pciconfig_iobase\0"
"perf_event_open\0"
"prof\0"
"profil\0"
"putmsg\0"
"putpmsg\0"
"query_module\0"
"rtas\0"
"s390_runtime_instr\0"
"security\0"
"sgetmask\0"
"ssetmask\0"
"stty\0"
"subpage_prot\0"
"switch_endian\0"
"sys_debug_setcontext\0"
"tuxcall\0"
"ulimit\0"
"uselib\0"
"vm86\0"
"vm86old\0"
"vserver\0"
}, {
/* Nice grab-bag of all system calls which need superuser capabilities */
.set_name = "@privileged",
.value =
"@clock\0"
"@module\0"
"@raw-io\0"
"acct\0"
"bdflush\0"
"bpf\0"
"chown32\0"
"chown\0"
"chroot\0"
"fchown32\0"
"fchown\0"
"fchownat\0"
"kexec_file_load\0"
"kexec_load\0"
"lchown32\0"
"lchown\0"
"nfsservctl\0"
"pivot_root\0"
"quotactl\0"
"reboot\0"
"setdomainname\0"
"setfsuid32\0"
"setfsuid\0"
"setgroups32\0"
"setgroups\0"
"sethostname\0"
"setresuid32\0"
"setresuid\0"
"setreuid32\0"
"setreuid\0"
"setuid32\0"
"setuid\0"
"stime\0"
"swapoff\0"
"swapon\0"
"sysctl\0"
"vhangup\0"
}, {
/* Process control, execution, namespaces */
.set_name = "@process",
.value =
"arch_prctl\0"
"clone\0"
"execve\0"
"execveat\0"
"fork\0"
"kill\0"
"prctl\0"
"setns\0"
"tgkill\0"
"tkill\0"
"unshare\0"
"vfork\0"
}, {
/* Raw I/O ports */
.set_name = "@raw-io",
.value =
"ioperm\0"
"iopl\0"
"pciconfig_read\0"
"pciconfig_write\0"
"s390_pci_mmio_read\0"
"s390_pci_mmio_write\0"
}, {
.set_name = NULL,
.value = NULL
}
};

7
src/shared/seccomp-util.h
View File

@ -26,3 +26,10 @@ const char* seccomp_arch_to_string(uint32_t c);
int seccomp_arch_from_string(const char *n, uint32_t *ret);
int seccomp_add_secondary_archs(scmp_filter_ctx *c);
typedef struct SystemCallFilterSet {
const char *set_name;
const char *value;
} SystemCallFilterSet;
extern const SystemCallFilterSet syscall_filter_sets[];