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-rw-r--r--src/core/dynamic-user.c51
-rw-r--r--src/core/execute.c15
-rw-r--r--src/nss-systemd/nss-systemd.c262
3 files changed, 235 insertions, 93 deletions
diff --git a/src/core/dynamic-user.c b/src/core/dynamic-user.c
index 8035bee231..185d0e5f00 100644
--- a/src/core/dynamic-user.c
+++ b/src/core/dynamic-user.c
@@ -150,6 +150,42 @@ int dynamic_user_acquire(Manager *m, const char *name, DynamicUser** ret) {
return 1;
}
+static int make_uid_symlinks(uid_t uid, const char *name, bool b) {
+
+ char path1[strlen("/run/systemd/dynamic-uid/direct:") + DECIMAL_STR_MAX(uid_t) + 1];
+ const char *path2;
+ int r = 0;
+
+ /* Add direct additional symlinks for direct lookups of dynamic UIDs and their names by userspace code. The
+ * only reason we have this is because dbus-daemon cannot use D-Bus for resolving users and groups (since it
+ * would be its own client then). We hence keep these world-readable symlinks in place, so that the
+ * unprivileged dbus user can read the mappings when it needs them via these symlinks instead of having to go
+ * via the bus. Ideally, we'd use the lock files we keep for this anyway, but we can't since we use BSD locks
+ * on them and as those may be taken by any user with read access we can't make them world-readable. */
+
+ xsprintf(path1, "/run/systemd/dynamic-uid/direct:" UID_FMT, uid);
+ if (unlink(path1) < 0) {
+ if (errno != ENOENT)
+ r = -errno;
+ }
+ if (b) {
+ if (symlink(name, path1) < 0)
+ r = -errno;
+ }
+
+ path2 = strjoina("/run/systemd/dynamic-uid/direct:", name);
+ if (unlink(path2) < 0) {
+ if (errno != ENOENT)
+ r = -errno;
+ }
+ if (b) {
+ if (symlink(path1 + strlen("/run/systemd/dynamic-uid/direct:"), path2) < 0)
+ r = -errno;
+ }
+
+ return r;
+}
+
static int pick_uid(const char *name, uid_t *ret_uid) {
static const uint8_t hash_key[] = {
@@ -223,6 +259,7 @@ static int pick_uid(const char *name, uid_t *ret_uid) {
}
(void) ftruncate(lock_fd, l);
+ (void) make_uid_symlinks(candidate, name, true); /* also add direct lookup symlinks */
*ret_uid = candidate;
r = lock_fd;
@@ -324,14 +361,16 @@ static int dynamic_user_push(DynamicUser *d, uid_t uid, int lock_fd) {
return 0;
}
-static void unlink_uid_lock(int lock_fd, uid_t uid) {
+static void unlink_uid_lock(int lock_fd, uid_t uid, const char *name) {
char lock_path[strlen("/run/systemd/dynamic-uid/") + DECIMAL_STR_MAX(uid_t) + 1];
if (lock_fd < 0)
return;
xsprintf(lock_path, "/run/systemd/dynamic-uid/" UID_FMT, uid);
- (void) unlink_noerrno(lock_path);
+ (void) unlink(lock_path);
+
+ (void) make_uid_symlinks(uid, name, false); /* remove direct lookup symlinks */
}
int dynamic_user_realize(DynamicUser *d, uid_t *ret) {
@@ -399,7 +438,7 @@ int dynamic_user_realize(DynamicUser *d, uid_t *ret) {
/* So, we found a working UID/lock combination. Let's see if we actually still need it. */
if (lockf(d->storage_socket[0], F_LOCK, 0) < 0) {
- unlink_uid_lock(uid_lock_fd, uid);
+ unlink_uid_lock(uid_lock_fd, uid, d->name);
return -errno;
}
@@ -407,7 +446,7 @@ int dynamic_user_realize(DynamicUser *d, uid_t *ret) {
if (r < 0) {
if (r != -EAGAIN) {
/* OK, something bad happened, let's get rid of the bits we acquired. */
- unlink_uid_lock(uid_lock_fd, uid);
+ unlink_uid_lock(uid_lock_fd, uid, d->name);
goto finish;
}
@@ -416,7 +455,7 @@ int dynamic_user_realize(DynamicUser *d, uid_t *ret) {
/* Hmm, so as it appears there's now something stored in the storage socket. Throw away what we
* acquired, and use what's stored now. */
- unlink_uid_lock(uid_lock_fd, uid);
+ unlink_uid_lock(uid_lock_fd, uid, d->name);
safe_close(uid_lock_fd);
uid = new_uid;
@@ -513,7 +552,7 @@ static int dynamic_user_close(DynamicUser *d) {
goto finish;
/* This dynamic user was realized and dynamically allocated. In this case, let's remove the lock file. */
- unlink_uid_lock(lock_fd, uid);
+ unlink_uid_lock(lock_fd, uid, d->name);
r = 1;
finish:
diff --git a/src/core/execute.c b/src/core/execute.c
index 4c786a2e33..0af8eb5a02 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -91,6 +91,7 @@
#include "selinux-util.h"
#include "signal-util.h"
#include "smack-util.h"
+#include "special.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
@@ -1384,6 +1385,7 @@ static void do_idle_pipe_dance(int idle_pipe[4]) {
}
static int build_environment(
+ Unit *u,
const ExecContext *c,
const ExecParameters *p,
unsigned n_fds,
@@ -1401,7 +1403,7 @@ static int build_environment(
assert(c);
assert(ret);
- our_env = new0(char*, 12);
+ our_env = new0(char*, 13);
if (!our_env)
return -ENOMEM;
@@ -1436,6 +1438,16 @@ static int build_environment(
our_env[n_env++] = x;
}
+ /* If this is D-Bus, tell the nss-systemd module, since it relies on being able to use D-Bus look up dynamic
+ * users via PID 1, possibly dead-locking the dbus daemon. This way it will not use D-Bus to resolve names, but
+ * check the database directly. */
+ if (unit_has_name(u, SPECIAL_DBUS_SERVICE)) {
+ x = strdup("SYSTEMD_NSS_BYPASS_BUS=1");
+ if (!x)
+ return -ENOMEM;
+ our_env[n_env++] = x;
+ }
+
if (home) {
x = strappend("HOME=", home);
if (!x)
@@ -2100,6 +2112,7 @@ static int exec_child(
}
r = build_environment(
+ unit,
context,
params,
n_fds,
diff --git a/src/nss-systemd/nss-systemd.c b/src/nss-systemd/nss-systemd.c
index 7078c0c50c..17d04e958d 100644
--- a/src/nss-systemd/nss-systemd.c
+++ b/src/nss-systemd/nss-systemd.c
@@ -21,11 +21,14 @@
#include "sd-bus.h"
+#include "alloc-util.h"
#include "bus-common-errors.h"
#include "env-util.h"
+#include "fs-util.h"
#include "macro.h"
#include "nss-util.h"
#include "signal-util.h"
+#include "stdio-util.h"
#include "string-util.h"
#include "user-util.h"
#include "util.h"
@@ -75,15 +78,50 @@ static const struct group nobody_group = {
NSS_GETPW_PROTOTYPES(systemd);
NSS_GETGR_PROTOTYPES(systemd);
+static int direct_lookup_name(const char *name, uid_t *ret) {
+ _cleanup_free_ char *s = NULL;
+ const char *path;
+ int r;
+
+ assert(name);
+
+ /* Normally, we go via the bus to resolve names. That has the benefit that it is available from any mount
+ * namespace and subject to proper authentication. However, there's one problem: if our module is called from
+ * dbus-daemon itself we really can't use D-Bus to communicate. In this case, resort to a client-side hack,
+ * and look for the dynamic names directly. This is pretty ugly, but breaks the cyclic dependency. */
+
+ path = strjoina("/run/systemd/dynamic-uid/direct:", name);
+ r = readlink_malloc(path, &s);
+ if (r < 0)
+ return r;
+
+ return parse_uid(s, ret);
+}
+
+static int direct_lookup_uid(uid_t uid, char **ret) {
+ char path[strlen("/run/systemd/dynamic-uid/direct:") + DECIMAL_STR_MAX(uid_t) + 1], *s;
+ int r;
+
+ xsprintf(path, "/run/systemd/dynamic-uid/direct:" UID_FMT, uid);
+
+ r = readlink_malloc(path, &s);
+ if (r < 0)
+ return r;
+ if (!valid_user_group_name(s)) { /* extra safety check */
+ free(s);
+ return -EINVAL;
+ }
+
+ *ret = s;
+ return 0;
+}
+
enum nss_status _nss_systemd_getpwnam_r(
const char *name,
struct passwd *pwd,
char *buffer, size_t buflen,
int *errnop) {
- _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
- _cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
- _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
uint32_t translated;
size_t l;
int r;
@@ -114,30 +152,45 @@ enum nss_status _nss_systemd_getpwnam_r(
if (getenv_bool("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
goto not_found;
- r = sd_bus_open_system(&bus);
- if (r < 0)
- goto fail;
+ if (getenv_bool("SYSTEMD_NSS_BYPASS_BUS") > 0) {
- r = sd_bus_call_method(bus,
- "org.freedesktop.systemd1",
- "/org/freedesktop/systemd1",
- "org.freedesktop.systemd1.Manager",
- "LookupDynamicUserByName",
- &error,
- &reply,
- "s",
- name);
- if (r < 0) {
- if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
+ /* Access the dynamic UID allocation directly if we are called from dbus-daemon, see above. */
+ r = direct_lookup_name(name, (uid_t*) &translated);
+ if (r == -ENOENT)
goto not_found;
-
- goto fail;
+ if (r < 0)
+ goto fail;
+
+ } else {
+ _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+ _cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
+ _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+
+ r = sd_bus_open_system(&bus);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_call_method(bus,
+ "org.freedesktop.systemd1",
+ "/org/freedesktop/systemd1",
+ "org.freedesktop.systemd1.Manager",
+ "LookupDynamicUserByName",
+ &error,
+ &reply,
+ "s",
+ name);
+ if (r < 0) {
+ if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
+ goto not_found;
+
+ goto fail;
+ }
+
+ r = sd_bus_message_read(reply, "u", &translated);
+ if (r < 0)
+ goto fail;
}
- r = sd_bus_message_read(reply, "u", &translated);
- if (r < 0)
- goto fail;
-
l = strlen(name);
if (buflen < l+1) {
*errnop = ENOMEM;
@@ -175,6 +228,7 @@ enum nss_status _nss_systemd_getpwuid_r(
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+ _cleanup_free_ char *direct = NULL;
const char *translated;
size_t l;
int r;
@@ -204,30 +258,42 @@ enum nss_status _nss_systemd_getpwuid_r(
if (getenv_bool("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
goto not_found;
- r = sd_bus_open_system(&bus);
- if (r < 0)
- goto fail;
+ if (getenv_bool("SYSTEMD_NSS_BYPASS_BUS") > 0) {
- r = sd_bus_call_method(bus,
- "org.freedesktop.systemd1",
- "/org/freedesktop/systemd1",
- "org.freedesktop.systemd1.Manager",
- "LookupDynamicUserByUID",
- &error,
- &reply,
- "u",
- (uint32_t) uid);
- if (r < 0) {
- if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
+ r = direct_lookup_uid(uid, &direct);
+ if (r == -ENOENT)
goto not_found;
-
- goto fail;
+ if (r < 0)
+ goto fail;
+
+ translated = direct;
+
+ } else {
+ r = sd_bus_open_system(&bus);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_call_method(bus,
+ "org.freedesktop.systemd1",
+ "/org/freedesktop/systemd1",
+ "org.freedesktop.systemd1.Manager",
+ "LookupDynamicUserByUID",
+ &error,
+ &reply,
+ "u",
+ (uint32_t) uid);
+ if (r < 0) {
+ if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
+ goto not_found;
+
+ goto fail;
+ }
+
+ r = sd_bus_message_read(reply, "s", &translated);
+ if (r < 0)
+ goto fail;
}
- r = sd_bus_message_read(reply, "s", &translated);
- if (r < 0)
- goto fail;
-
l = strlen(translated) + 1;
if (buflen < l) {
*errnop = ENOMEM;
@@ -262,9 +328,6 @@ enum nss_status _nss_systemd_getgrnam_r(
char *buffer, size_t buflen,
int *errnop) {
- _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
- _cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
- _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
uint32_t translated;
size_t l;
int r;
@@ -294,30 +357,45 @@ enum nss_status _nss_systemd_getgrnam_r(
if (getenv_bool("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
goto not_found;
- r = sd_bus_open_system(&bus);
- if (r < 0)
- goto fail;
+ if (getenv_bool("SYSTEMD_NSS_BYPASS_BUS") > 0) {
- r = sd_bus_call_method(bus,
- "org.freedesktop.systemd1",
- "/org/freedesktop/systemd1",
- "org.freedesktop.systemd1.Manager",
- "LookupDynamicUserByName",
- &error,
- &reply,
- "s",
- name);
- if (r < 0) {
- if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
+ /* Access the dynamic GID allocation directly if we are called from dbus-daemon, see above. */
+ r = direct_lookup_name(name, (uid_t*) &translated);
+ if (r == -ENOENT)
goto not_found;
-
- goto fail;
+ if (r < 0)
+ goto fail;
+ } else {
+
+ _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+ _cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
+ _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+
+ r = sd_bus_open_system(&bus);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_call_method(bus,
+ "org.freedesktop.systemd1",
+ "/org/freedesktop/systemd1",
+ "org.freedesktop.systemd1.Manager",
+ "LookupDynamicUserByName",
+ &error,
+ &reply,
+ "s",
+ name);
+ if (r < 0) {
+ if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
+ goto not_found;
+
+ goto fail;
+ }
+
+ r = sd_bus_message_read(reply, "u", &translated);
+ if (r < 0)
+ goto fail;
}
- r = sd_bus_message_read(reply, "u", &translated);
- if (r < 0)
- goto fail;
-
l = sizeof(char*) + strlen(name) + 1;
if (buflen < l) {
*errnop = ENOMEM;
@@ -353,6 +431,7 @@ enum nss_status _nss_systemd_getgrgid_r(
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+ _cleanup_free_ char *direct = NULL;
const char *translated;
size_t l;
int r;
@@ -382,30 +461,41 @@ enum nss_status _nss_systemd_getgrgid_r(
if (getenv_bool("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
goto not_found;
- r = sd_bus_open_system(&bus);
- if (r < 0)
- goto fail;
+ if (getenv_bool("SYSTEMD_NSS_BYPASS_BUS") > 0) {
- r = sd_bus_call_method(bus,
- "org.freedesktop.systemd1",
- "/org/freedesktop/systemd1",
- "org.freedesktop.systemd1.Manager",
- "LookupDynamicUserByUID",
- &error,
- &reply,
- "u",
- (uint32_t) gid);
- if (r < 0) {
- if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
+ r = direct_lookup_uid(gid, &direct);
+ if (r == -ENOENT)
goto not_found;
-
- goto fail;
+ if (r < 0)
+ goto fail;
+
+ translated = direct;
+ } else {
+ r = sd_bus_open_system(&bus);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_call_method(bus,
+ "org.freedesktop.systemd1",
+ "/org/freedesktop/systemd1",
+ "org.freedesktop.systemd1.Manager",
+ "LookupDynamicUserByUID",
+ &error,
+ &reply,
+ "u",
+ (uint32_t) gid);
+ if (r < 0) {
+ if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
+ goto not_found;
+
+ goto fail;
+ }
+
+ r = sd_bus_message_read(reply, "s", &translated);
+ if (r < 0)
+ goto fail;
}
- r = sd_bus_message_read(reply, "s", &translated);
- if (r < 0)
- goto fail;
-
l = sizeof(char*) + strlen(translated) + 1;
if (buflen < l) {
*errnop = ENOMEM;
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-07-14 16:27:35 +0000