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core: introduce ProtectProc= and ProcSubset= to expose hidepid= and subset= procfs mount options 

Kernel 5.8 gained a hidepid= implementation that is truly per procfs,
which allows us to mount a distinct once into every unit, with
individual hidepid= settings. Let's expose this via two new settings:
ProtectProc= (wrapping hidpid=) and ProcSubset= (wrapping subset=).

Replaces: #11670
This commit is contained in:
Lennart Poettering 2020-08-06 12:51:50 +02:00
parent df6b900a1b
commit 4e39995371
12 changed files with 131 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
docs/TRANSIENT-SETTINGS.md
View File

@ -151,6 +151,8 @@ All execution-related settings are available for transient units.
✓ TimerSlackNSec=
✓ NoNewPrivileges=
✓ KeyringMode=
✓ ProtectProc=
✓ ProcSubset=
✓ SystemCallFilter=
✓ SystemCallArchitectures=
✓ SystemCallErrorNumber=

12
src/core/dbus-execute.c
View File

@ -47,6 +47,8 @@ static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_exec_input, exec_input, ExecInp
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_exec_utmp_mode, exec_utmp_mode, ExecUtmpMode);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_exec_preserve_mode, exec_preserve_mode, ExecPreserveMode);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_exec_keyring_mode, exec_keyring_mode, ExecKeyringMode);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_protect_proc, protect_proc, ProtectProc);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_proc_subset, proc_subset, ProcSubset);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_protect_home, protect_home, ProtectHome);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_protect_system, protect_system, ProtectSystem);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_personality, personality, unsigned long);
@ -1016,6 +1018,8 @@ const sd_bus_vtable bus_exec_vtable[] = {
SD_BUS_PROPERTY("TemporaryFileSystem", "a(ss)", property_get_temporary_filesystems, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("MountAPIVFS", "b", bus_property_get_bool, offsetof(ExecContext, mount_apivfs), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("KeyringMode", "s", property_get_exec_keyring_mode, offsetof(ExecContext, keyring_mode), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("ProtectProc", "s", property_get_protect_proc, offsetof(ExecContext, protect_proc), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("ProcSubset", "s", property_get_proc_subset, offsetof(ExecContext, proc_subset), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("ProtectHostname", "b", bus_property_get_bool, offsetof(ExecContext, protect_hostname), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("NetworkNamespacePath", "s", NULL, offsetof(ExecContext, network_namespace_path), SD_BUS_VTABLE_PROPERTY_CONST),
@ -1354,6 +1358,8 @@ static BUS_DEFINE_SET_TRANSIENT_PARSE(utmp_mode, ExecUtmpMode, exec_utmp_mode_fr
static BUS_DEFINE_SET_TRANSIENT_PARSE(protect_system, ProtectSystem, protect_system_from_string);
static BUS_DEFINE_SET_TRANSIENT_PARSE(protect_home, ProtectHome, protect_home_from_string);
static BUS_DEFINE_SET_TRANSIENT_PARSE(keyring_mode, ExecKeyringMode, exec_keyring_mode_from_string);
static BUS_DEFINE_SET_TRANSIENT_PARSE(protect_proc, ProtectProc, protect_proc_from_string);
static BUS_DEFINE_SET_TRANSIENT_PARSE(proc_subset, ProcSubset, proc_subset_from_string);
static BUS_DEFINE_SET_TRANSIENT_PARSE(preserve_mode, ExecPreserveMode, exec_preserve_mode_from_string);
static BUS_DEFINE_SET_TRANSIENT_PARSE_PTR(personality, unsigned long, parse_personality);
static BUS_DEFINE_SET_TRANSIENT_TO_STRING_ALLOC(secure_bits, "i", int32_t, int, "%" PRIi32, secure_bits_to_string_alloc_with_check);
@ -1706,6 +1712,12 @@ int bus_exec_context_set_transient_property(
if (streq(name, "KeyringMode"))
return bus_set_transient_keyring_mode(u, name, &c->keyring_mode, message, flags, error);
if (streq(name, "ProtectProc"))
return bus_set_transient_protect_proc(u, name, &c->protect_proc, message, flags, error);
if (streq(name, "ProcSubset"))
return bus_set_transient_proc_subset(u, name, &c->proc_subset, message, flags, error);
if (streq(name, "RuntimeDirectoryPreserve"))
return bus_set_transient_preserve_mode(u, name, &c->runtime_directory_preserve_mode, message, flags, error);

14
src/core/execute.c
View File

@ -1948,7 +1948,9 @@ static bool exec_needs_mount_namespace(
context->protect_kernel_tunables ||
context->protect_kernel_modules ||
context->protect_kernel_logs ||
context->protect_control_groups)
context->protect_control_groups ||
context->protect_proc != PROTECT_PROC_DEFAULT ||
context->proc_subset != PROC_SUBSET_ALL)
return true;
if (context->root_directory) {
@ -2652,6 +2654,8 @@ static int apply_mount_namespace(
.private_mounts = context->private_mounts,
.protect_home = context->protect_home,
.protect_system = context->protect_system,
.protect_proc = context->protect_proc,
.proc_subset = context->proc_subset,
};
} else if (!context->dynamic_user && root_dir)
/*
@ -4601,7 +4605,9 @@ void exec_context_dump(const ExecContext *c, FILE* f, const char *prefix) {
"%sRestrictRealtime: %s\n"
"%sRestrictSUIDSGID: %s\n"
"%sKeyringMode: %s\n"
"%sProtectHostname: %s\n",
"%sProtectHostname: %s\n"
"%sProtectProc: %s\n"
"%sProcSubset: %s\n",
prefix, c->umask,
prefix, c->working_directory ? c->working_directory : "/",
prefix, c->root_directory ? c->root_directory : "/",
@ -4623,7 +4629,9 @@ void exec_context_dump(const ExecContext *c, FILE* f, const char *prefix) {
prefix, yes_no(c->restrict_realtime),
prefix, yes_no(c->restrict_suid_sgid),
prefix, exec_keyring_mode_to_string(c->keyring_mode),
prefix, yes_no(c->protect_hostname));
prefix, yes_no(c->protect_hostname),
prefix, protect_proc_to_string(c->protect_proc),
prefix, proc_subset_to_string(c->proc_subset));
if (c->root_image)
fprintf(f, "%sRootImage: %s\n", prefix, c->root_image);

3
src/core/execute.h
View File

@ -260,6 +260,9 @@ struct ExecContext {
char *log_namespace;
ProtectProc protect_proc; /* hidepid= */
ProcSubset proc_subset; /* subset= */
bool private_tmp;
bool private_network;
bool private_devices;

2
src/core/load-fragment-gperf.gperf.m4
View File

@ -73,6 +73,8 @@ $1.AmbientCapabilities, config_parse_capability_set, 0,
$1.TimerSlackNSec, config_parse_nsec, 0, offsetof($1, exec_context.timer_slack_nsec)
$1.NoNewPrivileges, config_parse_bool, 0, offsetof($1, exec_context.no_new_privileges)
$1.KeyringMode, config_parse_exec_keyring_mode, 0, offsetof($1, exec_context.keyring_mode)
$1.ProtectProc, config_parse_protect_proc, 0, offsetof($1, exec_context.protect_proc)
$1.ProcSubset, config_parse_proc_subset, 0, offsetof($1, exec_context.proc_subset)
m4_ifdef(`HAVE_SECCOMP',
`$1.SystemCallFilter, config_parse_syscall_filter, 0, offsetof($1, exec_context)
$1.SystemCallArchitectures, config_parse_syscall_archs, 0, offsetof($1, exec_context.syscall_archs)

2
src/core/load-fragment.c
View File

@ -118,6 +118,8 @@ DEFINE_CONFIG_PARSE(config_parse_exec_secure_bits, secure_bits_from_string, "Fai
DEFINE_CONFIG_PARSE_ENUM(config_parse_collect_mode, collect_mode, CollectMode, "Failed to parse garbage collection mode");
DEFINE_CONFIG_PARSE_ENUM(config_parse_device_policy, cgroup_device_policy, CGroupDevicePolicy, "Failed to parse device policy");
DEFINE_CONFIG_PARSE_ENUM(config_parse_exec_keyring_mode, exec_keyring_mode, ExecKeyringMode, "Failed to parse keyring mode");
DEFINE_CONFIG_PARSE_ENUM(config_parse_protect_proc, protect_proc, ProtectProc, "Failed to parse /proc/ protection mode");
DEFINE_CONFIG_PARSE_ENUM(config_parse_proc_subset, proc_subset, ProcSubset, "Failed to parse /proc/ subset mode");
DEFINE_CONFIG_PARSE_ENUM(config_parse_exec_utmp_mode, exec_utmp_mode, ExecUtmpMode, "Failed to parse utmp mode");
DEFINE_CONFIG_PARSE_ENUM(config_parse_job_mode, job_mode, JobMode, "Failed to parse job mode");
DEFINE_CONFIG_PARSE_ENUM(config_parse_notify_access, notify_access, NotifyAccess, "Failed to parse notify access specifier");

2
src/core/load-fragment.h
View File

@ -108,6 +108,8 @@ CONFIG_PARSER_PROTOTYPE(config_parse_user_group_strv_compat);
CONFIG_PARSER_PROTOTYPE(config_parse_restrict_namespaces);
CONFIG_PARSER_PROTOTYPE(config_parse_bind_paths);
CONFIG_PARSER_PROTOTYPE(config_parse_exec_keyring_mode);
CONFIG_PARSER_PROTOTYPE(config_parse_protect_proc);
CONFIG_PARSER_PROTOTYPE(config_parse_proc_subset);
CONFIG_PARSER_PROTOTYPE(config_parse_job_timeout_sec);
CONFIG_PARSER_PROTOTYPE(config_parse_job_running_timeout_sec);
CONFIG_PARSER_PROTOTYPE(config_parse_log_extra_fields);

83
src/core/namespace.c
View File

@ -97,7 +97,7 @@ static const MountEntry protect_kernel_tunables_table[] = {
{ "/proc/latency_stats", READONLY, true },
{ "/proc/mtrr", READONLY, true },
{ "/proc/scsi", READONLY, true },
{ "/proc/sys", READONLY, false },
{ "/proc/sys", READONLY, true },
{ "/proc/sysrq-trigger", READONLY, true },
{ "/proc/timer_stats", READONLY, true },
{ "/sys", READONLY, false },
@ -863,22 +863,53 @@ static int mount_sysfs(const MountEntry *m) {
return 1;
}
static int mount_procfs(const MountEntry *m) {
int r;
static int mount_procfs(const MountEntry *m, const NamespaceInfo *ns_info) {
const char *entry_path;
assert(m);
assert(ns_info);
(void) mkdir_p_label(mount_entry_path(m), 0755);
entry_path = mount_entry_path(m);
r = path_is_mount_point(mount_entry_path(m), NULL, 0);
if (r < 0)
return log_debug_errno(r, "Unable to determine whether /proc is already mounted: %m");
if (r > 0) /* make this a NOP if /proc is already a mount point */
return 0;
/* Mount a new instance, so that we get the one that matches our user namespace, if we are running in
* one. i.e we don't reuse existing mounts here under any condition, we want a new instance owned by
* our user namespace and with our hidepid= settings applied. Hence, let's get rid of everything
* mounted on /proc/ first. */
/* Mount a new instance, so that we get the one that matches our user namespace, if we are running in one */
if (mount("proc", mount_entry_path(m), "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) < 0)
return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m));
(void) mkdir_p_label(entry_path, 0755);
(void) umount_recursive(entry_path, 0);
if (ns_info->protect_proc != PROTECT_PROC_DEFAULT ||
ns_info->proc_subset != PROC_SUBSET_ALL) {
_cleanup_free_ char *opts = NULL;
/* Starting with kernel 5.8 procfs' hidepid= logic is truly per-instance (previously it
* pretended to be per-instance but actually was per-namespace), hence let's make use of it
* if requested. To make sure this logic succeeds only on kernels where hidepid= is
* per-instance, we'll exclusively use the textual value for hidepid=, since support was
* added in the same commit: if it's supported it is thus also per-instance. */
opts = strjoin("hidepid=",
ns_info->protect_proc == PROTECT_PROC_DEFAULT ? "off" :
protect_proc_to_string(ns_info->protect_proc),
ns_info->proc_subset == PROC_SUBSET_PID ? ",subset=pid" : "");
if (!opts)
return -ENOMEM;
if (mount("proc", entry_path, "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, opts) < 0) {
if (errno != EINVAL)
return log_debug_errno(errno, "Failed to mount %s (options=%s): %m", mount_entry_path(m), opts);
/* If this failed with EINVAL then this likely means the textual hidepid= stuff is
* not supported by the kernel, and thus the per-instance hidepid= neither, which
* means we really don't want to use it, since it would affect our host's /proc
* mount. Hence let's gracefully fallback to a classic, unrestricted version. */
} else
return 1;
}
if (mount("proc", entry_path, "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) < 0)
return log_debug_errno(errno, "Failed to mount %s (no options): %m", mount_entry_path(m));
return 1;
}
@ -997,7 +1028,8 @@ static int follow_symlink(
static int apply_mount(
const char *root_directory,
MountEntry *m) {
MountEntry *m,
const NamespaceInfo *ns_info) {
_cleanup_free_ char *inaccessible = NULL;
bool rbind = true, make = false;
@ -1005,6 +1037,7 @@ static int apply_mount(
int r;
assert(m);
assert(ns_info);
log_debug("Applying namespace mount on %s", mount_entry_path(m));
@ -1109,7 +1142,7 @@ static int apply_mount(
return mount_sysfs(m);
case PROCFS:
return mount_procfs(m);
return mount_procfs(m, ns_info);
case MOUNT_IMAGES:
return mount_images(m);
@ -1221,7 +1254,9 @@ static bool namespace_info_mount_apivfs(const NamespaceInfo *ns_info) {
return ns_info->mount_apivfs ||
ns_info->protect_control_groups ||
ns_info->protect_kernel_tunables;
ns_info->protect_kernel_tunables ||
ns_info->protect_proc != PROTECT_PROC_DEFAULT ||
ns_info->proc_subset != PROC_SUBSET_ALL;
}
static size_t namespace_calculate_mounts(
@ -1717,7 +1752,7 @@ int setup_namespace(
break;
}
r = apply_mount(root, m);
r = apply_mount(root, m, ns_info);
if (r < 0) {
if (error_path && mount_entry_path(m))
*error_path = strdup(mount_entry_path(m));
@ -2237,3 +2272,19 @@ static const char* const namespace_type_table[] = {
};
DEFINE_STRING_TABLE_LOOKUP(namespace_type, NamespaceType);
static const char* const protect_proc_table[_PROTECT_PROC_MAX] = {
[PROTECT_PROC_DEFAULT] = "default",
[PROTECT_PROC_NOACCESS] = "noaccess",
[PROTECT_PROC_INVISIBLE] = "invisible",
[PROTECT_PROC_PTRACEABLE] = "ptraceable",
};
DEFINE_STRING_TABLE_LOOKUP(protect_proc, ProtectProc);
static const char* const proc_subset_table[_PROC_SUBSET_MAX] = {
[PROC_SUBSET_ALL] = "all",
[PROC_SUBSET_PID] = "pid",
};
DEFINE_STRING_TABLE_LOOKUP(proc_subset, ProcSubset);

24
src/core/namespace.h
View File

@ -47,6 +47,22 @@ typedef enum ProtectSystem {
_PROTECT_SYSTEM_INVALID = -1
} ProtectSystem;
typedef enum ProtectProc {
PROTECT_PROC_DEFAULT,
PROTECT_PROC_NOACCESS, /* hidepid=noaccess */
PROTECT_PROC_INVISIBLE, /* hidepid=invisible */
PROTECT_PROC_PTRACEABLE, /* hidepid=ptraceable */
_PROTECT_PROC_MAX,
_PROTECT_PROC_INVALID = -1,
} ProtectProc;
typedef enum ProcSubset {
PROC_SUBSET_ALL,
PROC_SUBSET_PID, /* subset=pid */
_PROC_SUBSET_MAX,
_PROC_SUBSET_INVALID = -1,
} ProcSubset;
struct NamespaceInfo {
bool ignore_protect_paths:1;
bool private_dev:1;
@ -59,6 +75,8 @@ struct NamespaceInfo {
bool protect_hostname:1;
ProtectHome protect_home;
ProtectSystem protect_system;
ProtectProc protect_proc;
ProcSubset proc_subset;
};
struct BindMount {
@ -135,6 +153,12 @@ ProtectHome protect_home_from_string(const char *s) _pure_;
const char* protect_system_to_string(ProtectSystem p) _const_;
ProtectSystem protect_system_from_string(const char *s) _pure_;
const char* protect_proc_to_string(ProtectProc i) _const_;
ProtectProc protect_proc_from_string(const char *s) _pure_;
const char* proc_subset_to_string(ProcSubset i) _const_;
ProcSubset proc_subset_from_string(const char *s) _pure_;
void bind_mount_free_many(BindMount *b, size_t n);
int bind_mount_add(BindMount **b, size_t *n, const BindMount *item);

2
src/shared/bus-unit-util.c
View File

@ -855,6 +855,8 @@ static int bus_append_execute_property(sd_bus_message *m, const char *field, con
"RuntimeDirectoryPreserve",
"Personality",
"KeyringMode",
"ProtectProc",
"ProcSubset",
"NetworkNamespacePath",
"LogNamespace"))
return bus_append_string(m, field, eq);

2
src/test/test-ns.c
View File

@ -36,6 +36,8 @@ int main(int argc, char *argv[]) {
.protect_control_groups = true,
.protect_kernel_tunables = true,
.protect_kernel_modules = true,
.protect_proc = PROTECT_PROC_NOACCESS,
.proc_subset = PROC_SUBSET_PID,
};
char *root_directory;

2
test/fuzz/fuzz-unit-file/directives.service
View File

@ -782,6 +782,8 @@ KEYMAP=
KEYMAP_TOGGLE=
KeepFree=
KeyringMode=
ProtectProc=
ProcSubset=
KillExcludeUsers=
KillOnlyUsers=
KillSignal=