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service: optionally call into PAM when dropping priviliges

This commit is contained in:
Lennart Poettering 2010-06-16 21:54:17 +02:00
parent 04aa0cb9c4
commit 5b6319dcee
17 changed files with 319 additions and 53 deletions
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3
Makefile.am
View File

@ -290,7 +290,8 @@ systemd_LDADD = \
$(DBUS_LIBS) \
$(UDEV_LIBS) \
$(CGROUP_LIBS) \
$(LIBWRAP_LIBS)
$(LIBWRAP_LIBS) \
$(PAM_LIBS)
test_engine_SOURCES = \
$(COMMON_SOURCES) \

55
configure.ac
View File

@ -111,27 +111,61 @@ AC_SUBST(CGROUP_LIBS)
AC_ARG_ENABLE([tcpwrap],
AS_HELP_STRING([--disable-tcpwrap],[Disable optional TCP wrappers support]),
[case "${enableval}" in
yes) tcpwrap=yes ;;
no) tcpwrap=no ;;
yes) have_tcpwrap=yes ;;
no) have_tcpwrap=no ;;
*) AC_MSG_ERROR(bad value ${enableval} for --disable-tcpwrap) ;;
esac],
[tcpwrap=auto])
[have_tcpwrap=auto])
if test "x${tcpwrap}" != xno ; then
if test "x${have_tcpwrap}" != xno ; then
ACX_LIBWRAP
if test "x${LIBWRAP_LIBS}" = x ; then
if test "x$tcpwrap" = xyes ; then
AC_MSG_ERROR([*** TCP wrappers support not found])
if test "x$have_tcpwrap" = xyes ; then
AC_MSG_ERROR([*** TCP wrappers support not found.])
fi
else
tcpwrap=yes
have_tcpwrap=yes
fi
else
LIBWRAP_LIBS=
LIBWRAP_LIBS=
fi
AC_SUBST(LIBWRAP_LIBS)
AC_ARG_ENABLE([pam],
AS_HELP_STRING([--disable-pam],[Disable optional PAM support]),
[case "${enableval}" in
yes) have_pam=yes ;;
no) have_pam=no ;;
*) AC_MSG_ERROR(bad value ${enableval} for --disable-pam) ;;
esac],
[have_pam=auto])
if test "x${have_pam}" != xno ; then
AC_CHECK_HEADERS(
[security/pam_modules.h security/pam_modutil.h security/pam_ext.h],
[have_pam=yes],
[if test "x$have_pam" = xyes ; then
AC_MSG_ERROR([*** PAM headers not found.])
fi])
AC_CHECK_LIB(
[pam],
[pam_syslog],
[have_pam=yes],
[if test "x$have_pam" = xyes ; then
AC_MSG_ERROR([*** libpam not found.])
fi])
if test "x$have_pam" = xyes ; then
PAM_LIBS="-lpam -lpam_misc"
AC_DEFINE(HAVE_PAM, 1, [PAM available])
fi
else
PAM_LIBS=
fi
AC_SUBST(PAM_LIBS)
AM_CONDITIONAL([HAVE_PAM], [test "x$have_pam" != xno])
have_gtk=no
AC_ARG_ENABLE(gtk, AS_HELP_STRING([--disable-gtk], [disable GTK tools]))
if test "x$enable_gtk" != "xno"; then
@ -336,7 +370,8 @@ echo "
Syslog service: ${SPECIAL_SYSLOG_SERVICE}
D-Bus service: ${SPECIAL_DBUS_SERVICE}
Gtk: ${have_gtk}
tcpwrap: ${tcpwrap}
tcpwrap: ${have_tcpwrap}
PAM: ${have_pam}
prefix: ${prefix}
root dir: ${with_rootdir}
udev rules dir: ${with_udevrulesdir}

10
fixme
View File

@ -51,14 +51,16 @@
* write utmp record a la upstart for processes
* run PAM session stuff
* use setproctitle() when forking, before exec() (waiting for (PR_SET_PROCTITLE_AREA to enter the kernel)
* follow property change dbus spec
* pam module
* selinux
Regularly:
* look for close() vs. close_nointr() vs. close_nointr_nofail()
* check for strerror(r) instead of strerror(-r)
* Use PR_SET_PROCTITLE_AREA if it becomes available in the kernel

6
src/dbus-execute.h
View File

@ -44,7 +44,8 @@
" <property name=\"User\" type=\"s\" access=\"read\"/>\n" \
" <property name=\"Group\" type=\"s\" access=\"read\"/>\n" \
" <property name=\"SupplementaryGroups\" type=\"as\" access=\"read\"/>\n" \
" <property name=\"TCPWrapName\" type=\"s\" access=\"read\"/>\n"
" <property name=\"TCPWrapName\" type=\"s\" access=\"read\"/>\n" \
" <property name=\"PAMName\" type=\"s\" access=\"read\"/>\n"
#define BUS_EXEC_CONTEXT_PROPERTIES(interface, context) \
{ interface, "Environment", bus_property_append_strv, "as", (context).environment }, \
@ -73,7 +74,8 @@
{ interface, "User", bus_property_append_string, "s", (context).user }, \
{ interface, "Group", bus_property_append_string, "s", (context).group }, \
{ interface, "SupplementaryGroups", bus_property_append_strv, "as", (context).supplementary_groups }, \
{ interface, "TCPWrapName", bus_property_append_string, "s", (context).tcpwrap_name }
{ interface, "TCPWrapName", bus_property_append_string, "s", (context).tcpwrap_name }, \
{ interface, "PAMName", bus_property_append_string, "s", (context).pam_name }
int bus_execute_append_output(Manager *m, DBusMessageIter *i, const char *property, void *data);
int bus_execute_append_input(Manager *m, DBusMessageIter *i, const char *property, void *data);

4
src/dbus-manager.c
View File

@ -626,7 +626,7 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection
return bus_send_error_reply(m, message, NULL, r);
}
e = strv_env_merge(m->environment, l, NULL);
e = strv_env_merge(2, m->environment, l);
strv_free(l);
if (!e)
@ -650,7 +650,7 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection
return bus_send_error_reply(m, message, NULL, r);
}
e = strv_env_delete(m->environment, l, NULL);
e = strv_env_delete(m->environment, 1, l);
strv_free(l);
if (!e)

205
src/execute.c
View File

@ -37,6 +37,10 @@
#include <sys/mount.h>
#include <linux/fs.h>
#ifdef HAVE_PAM
#include <security/pam_appl.h>
#endif
#include "execute.h"
#include "strv.h"
#include "macro.h"
@ -720,6 +724,164 @@ static int enforce_user(const ExecContext *context, uid_t uid) {
return 0;
}
#ifdef HAVE_PAM
static int null_conv(
int num_msg,
const struct pam_message **msg,
struct pam_response **resp,
void *appdata_ptr) {
/* We don't support conversations */
return PAM_CONV_ERR;
}
static int setup_pam(
const char *name,
const char *user,
const char *tty,
char ***pam_env,
int fds[], unsigned n_fds) {
static const struct pam_conv conv = {
.conv = null_conv,
.appdata_ptr = NULL
};
pam_handle_t *handle = NULL;
sigset_t ss, old_ss;
int pam_code = PAM_SUCCESS;
char **e = NULL;
bool close_session = false;
pid_t pam_pid = 0, parent_pid;
assert(name);
assert(user);
assert(pam_env);
/* We set up PAM in the parent process, then fork. The child
* will then stay around untill killed via PR_GET_PDEATHSIG or
* systemd via the cgroup logic. It will then remove the PAM
* session again. The parent process will exec() the actual
* daemon. We do things this way to ensure that the main PID
* of the daemon is the one we initially fork()ed. */
if ((pam_code = pam_start(name, user, &conv, &handle)) != PAM_SUCCESS) {
handle = NULL;
goto fail;
}
if (tty)
if ((pam_code = pam_set_item(handle, PAM_TTY, tty)) != PAM_SUCCESS)
goto fail;
if ((pam_code = pam_acct_mgmt(handle, PAM_SILENT)) != PAM_SUCCESS)
goto fail;
if ((pam_code = pam_open_session(handle, PAM_SILENT)) != PAM_SUCCESS)
goto fail;
close_session = true;
if ((pam_code = pam_setcred(handle, PAM_ESTABLISH_CRED | PAM_SILENT)) != PAM_SUCCESS)
goto fail;
if ((!(e = pam_getenvlist(handle)))) {
pam_code = PAM_BUF_ERR;
goto fail;
}
/* Block SIGTERM, so that we know that it won't get lost in
* the child */
if (sigemptyset(&ss) < 0 ||
sigaddset(&ss, SIGTERM) < 0 ||
sigprocmask(SIG_BLOCK, &ss, &old_ss) < 0)
goto fail;
parent_pid = getpid();
if ((pam_pid = fork()) < 0)
goto fail;
if (pam_pid == 0) {
int sig;
int r = EXIT_PAM;
/* The child's job is to reset the PAM session on
* termination */
/* This string must fit in 10 chars (i.e. the length
* of "/sbin/init") */
rename_process("sd:pam");
/* Make sure we don't keep open the passed fds in this
child. We assume that otherwise only those fds are
open here that have been opened by PAM. */
close_many(fds, n_fds);
/* Wait until our parent died. This will most likely
* not work since the kernel does not allow
* unpriviliged paretns kill their priviliged children
* this way. We rely on the control groups kill logic
* to do the rest for us. */
if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
goto child_finish;
/* Check if our parent process might already have
* died? */
if (getppid() == parent_pid) {
if (sigwait(&ss, &sig) < 0)
goto child_finish;
assert(sig == SIGTERM);
}
/* Only if our parent died we'll end the session */
if (getppid() != parent_pid)
if ((pam_code = pam_close_session(handle, PAM_DATA_SILENT)) != PAM_SUCCESS)
goto child_finish;
r = 0;
child_finish:
pam_end(handle, pam_code | PAM_DATA_SILENT);
_exit(r);
}
/* If the child was forked off successfully it will do all the
* cleanups, so forget about the handle here. */
handle = NULL;
/* Unblock SIGSUR1 again in the parent */
if (sigprocmask(SIG_SETMASK, &old_ss, NULL) < 0)
goto fail;
/* We close the log explicitly here, since the PAM modules
* might have opened it, but we don't want this fd around. */
closelog();
return 0;
fail:
if (handle) {
if (close_session)
pam_code = pam_close_session(handle, PAM_DATA_SILENT);
pam_end(handle, pam_code | PAM_DATA_SILENT);
}
strv_free(e);
closelog();
if (pam_pid > 1)
kill(pam_pid, SIGTERM);
return EXIT_PAM;
}
#endif
int exec_spawn(ExecCommand *command,
char **argv,
const ExecContext *context,
@ -777,13 +939,17 @@ int exec_spawn(ExecCommand *command,
const char *username = NULL, *home = NULL;
uid_t uid = (uid_t) -1;
gid_t gid = (gid_t) -1;
char **our_env = NULL, **final_env = NULL;
char **our_env = NULL, **pam_env = NULL, **final_env = NULL;
unsigned n_env = 0;
int saved_stdout = -1, saved_stdin = -1;
bool keep_stdout = false, keep_stdin = false;
/* child */
/* This string must fit in 10 chars (i.e. the length
* of "/sbin/init") */
rename_process("sd:exec");
/* We reset exactly these signals, since they are the
* only ones we set to SIG_IGN in the main daemon. All
* others we leave untouched because we set them to
@ -928,6 +1094,25 @@ int exec_spawn(ExecCommand *command,
}
}
#ifdef HAVE_PAM
if (context->pam_name && username) {
/* Make sure no fds leak into the PAM
* supervisor process. We will call this later
* on again to make sure that any fds leaked
* by the PAM modules get closed before our
* exec(). */
if (close_all_fds(fds, n_fds) < 0) {
r = EXIT_FDS;
goto fail;
}
if (setup_pam(context->pam_name, username, context->tty_path, &pam_env, fds, n_fds) < 0) {
r = EXIT_PAM;
goto fail;
}
}
#endif
if (apply_permissions)
if (enforce_groups(context, username, uid) < 0) {
r = EXIT_GROUP;
@ -1049,7 +1234,13 @@ int exec_spawn(ExecCommand *command,
assert(n_env <= 6);
if (!(final_env = strv_env_merge(environment, our_env, context->environment, NULL))) {
if (!(final_env = strv_env_merge(
4,
environment,
our_env,
context->environment,
pam_env,
NULL))) {
r = EXIT_MEMORY;
goto fail;
}
@ -1060,6 +1251,7 @@ int exec_spawn(ExecCommand *command,
fail:
strv_free(our_env);
strv_free(final_env);
strv_free(pam_env);
if (saved_stdin >= 0)
close_nointr_nofail(saved_stdin);
@ -1133,6 +1325,9 @@ void exec_context_done(ExecContext *c) {
strv_free(c->supplementary_groups);
c->supplementary_groups = NULL;
free(c->pam_name);
c->pam_name = NULL;
if (c->capabilities) {
cap_free(c->capabilities);
c->capabilities = NULL;
@ -1332,6 +1527,9 @@ void exec_context_dump(ExecContext *c, FILE* f, const char *prefix) {
fputs("\n", f);
}
if (c->pam_name)
fprintf(f, "%sPAMName: %s", prefix, c->pam_name);
if (strv_length(c->read_write_dirs) > 0) {
fprintf(f, "%sReadWriteDirs:", prefix);
strv_fprintf(f, c->read_write_dirs);
@ -1613,6 +1811,9 @@ const char* exit_status_to_string(ExitStatus status) {
case EXIT_TCPWRAP:
return "TCPWRAP";
case EXIT_PAM:
return "PAM";
default:
return NULL;
}

5
src/execute.h
View File

@ -116,6 +116,8 @@ struct ExecContext {
char *group;
char **supplementary_groups;
char *pam_name;
char **read_write_dirs, **read_only_dirs, **inaccessible_dirs;
unsigned long mount_flags;
@ -182,7 +184,8 @@ typedef enum ExitStatus {
EXIT_SETSID, /* 220 */
EXIT_CONFIRM,
EXIT_STDERR,
EXIT_TCPWRAP
EXIT_TCPWRAP,
EXIT_PAM
} ExitStatus;

2
src/install.c
View File

@ -69,7 +69,7 @@ static int help(void) {
" enable [NAME...] Enable one or more units\n"
" disable [NAME...] Disable one or more units\n"
" test [NAME...] Test whether any of the specified units are enabled\n",
__progname);
program_invocation_short_name);
return 0;
}

3
src/load-fragment.c
View File

@ -1392,7 +1392,8 @@ static int load_from_path(Unit *u, const char *path) {
{ "InaccessibleDirectories",config_parse_path_strv, &(context).inaccessible_dirs, section }, \
{ "PrivateTmp", config_parse_bool, &(context).private_tmp, section }, \
{ "MountFlags", config_parse_mount_flags, &(context), section }, \
{ "TCPWrapName", config_parse_string, &(context).tcpwrap_name, section }
{ "TCPWrapName", config_parse_string, &(context).tcpwrap_name, section }, \
{ "PAMName", config_parse_string, &(context).pam_name, section }
const ConfigItem items[] = {
{ "Names", config_parse_names, u, "Unit" },

4
src/log.c
View File

@ -267,7 +267,7 @@ static int write_to_syslog(
zero(iovec);
IOVEC_SET_STRING(iovec[0], header_priority);
IOVEC_SET_STRING(iovec[1], header_time);
IOVEC_SET_STRING(iovec[2], __progname);
IOVEC_SET_STRING(iovec[2], program_invocation_short_name);
IOVEC_SET_STRING(iovec[3], header_pid);
IOVEC_SET_STRING(iovec[4], buffer);
@ -302,7 +302,7 @@ static int write_to_kmsg(
zero(iovec);
IOVEC_SET_STRING(iovec[0], header_priority);
IOVEC_SET_STRING(iovec[1], __progname);
IOVEC_SET_STRING(iovec[1], program_invocation_short_name);
IOVEC_SET_STRING(iovec[2], header_pid);
IOVEC_SET_STRING(iovec[3], buffer);
IOVEC_SET_STRING(iovec[4], "\n");

2
src/main.c
View File

@ -504,7 +504,7 @@ static int help(void) {
" --dump-configuration-items Dump understood unit configuration items\n"
" --confirm-spawn Ask for confirmation when spawning processes\n"
" --introspect[=INTERFACE] Extract D-Bus interface data\n",
__progname);
program_invocation_short_name);
return 0;
}

2
src/manager.c
View File

@ -109,7 +109,7 @@ static int manager_setup_notify(Manager *m) {
return -ENOMEM;
ne[1] = NULL;
t = strv_env_merge(m->environment, ne, NULL);
t = strv_env_merge(2, m->environment, ne);
free(ne[0]);
if (!t)

41
src/strv.c
View File

@ -374,7 +374,9 @@ char **strv_remove(char **l, const char *s) {
static int env_append(char **r, char ***k, char **a) {
assert(r);
assert(k);
assert(a);
if (!a)
return 0;
/* Add the entries of a to *k unless they already exist in *r
* in which case they are overriden instead. This assumes
@ -400,38 +402,33 @@ static int env_append(char **r, char ***k, char **a) {
return 0;
}
char **strv_env_merge(char **x, ...) {
char **strv_env_merge(unsigned n_lists, ...) {
size_t n = 0;
char **l, **k, **r;
va_list ap;
unsigned i;
/* Merges an arbitrary number of environment sets */
if (x) {
n += strv_length(x);
va_start(ap, x);
while ((l = va_arg(ap, char**)))
n += strv_length(l);
va_end(ap);
va_start(ap, n_lists);
for (i = 0; i < n_lists; i++) {
l = va_arg(ap, char**);
n += strv_length(l);
}
va_end(ap);
if (!(r = new(char*, n+1)))
return NULL;
k = r;
if (x) {
if (env_append(r, &k, x) < 0)
va_start(ap, n_lists);
for (i = 0; i < n_lists; i++) {
l = va_arg(ap, char**);
if (env_append(r, &k, l) < 0)
goto fail;
va_start(ap, x);
while ((l = va_arg(ap, char**)))
if (env_append(r, &k, l) < 0)
goto fail;
va_end(ap);
}
va_end(ap);
*k = NULL;
@ -472,7 +469,7 @@ static bool env_match(const char *t, const char *pattern) {
return false;
}
char **strv_env_delete(char **x, ...) {
char **strv_env_delete(char **x, unsigned n_lists, ...) {
size_t n = 0, i = 0;
char **l, **k, **r, **j;
va_list ap;
@ -486,12 +483,14 @@ char **strv_env_delete(char **x, ...) {
return NULL;
STRV_FOREACH(k, x) {
va_start(ap, x);
va_start(ap, n_lists);
while ((l = va_arg(ap, char**)))
for (i = 0; i < n_lists; i++) {
l = va_arg(ap, char**);
STRV_FOREACH(j, l)
if (env_match(*k, *j))
goto delete;
}
va_end(ap);

4
src/strv.h
View File

@ -55,8 +55,8 @@ char **strv_split_quoted(const char *s) _malloc_;
char *strv_join(char **l, const char *separator) _malloc_;
char **strv_env_merge(char **x, ...) _sentinel_;
char **strv_env_delete(char **x, ...) _sentinel_;
char **strv_env_merge(unsigned n_lists, ...);
char **strv_env_delete(char **x, unsigned n_lists, ...);
#define STRV_FOREACH(s, l) \
for ((s) = (l); (s) && *(s); (s)++)

2
src/systemctl.c
View File

@ -1322,7 +1322,7 @@ static int help(void) {
" show-environment Dump environment\n"
" set-environment [NAME=VALUE...] Set one or more environment variables\n"
" unset-environment [NAME...] Unset one or more environment variables\n",
__progname);
program_invocation_short_name);
return 0;
}

21
src/util.c
View File

@ -43,6 +43,7 @@
#include <sys/poll.h>
#include <libgen.h>
#include <ctype.h>
#include <sys/prctl.h>
#include "macro.h"
#include "util.h"
@ -222,6 +223,13 @@ void close_nointr_nofail(int fd) {
errno = saved_errno;
}
void close_many(const int fds[], unsigned n_fd) {
unsigned i;
for (i = 0; i < n_fd; i++)
close_nointr_nofail(fds[i]);
}
int parse_boolean(const char *v) {
assert(v);
@ -2161,6 +2169,19 @@ fallback:
return random() * RAND_MAX + random();
}
void rename_process(const char name[8]) {
assert(name);
prctl(PR_SET_NAME, name);
/* This is a like a poor man's setproctitle(). The string
* passed should fit in 7 chars (i.e. the length of
* "systemd") */
if (program_invocation_name)
strncpy(program_invocation_name, name, strlen(program_invocation_name));
}
static const char *const ioprio_class_table[] = {
[IOPRIO_CLASS_NONE] = "none",
[IOPRIO_CLASS_RT] = "realtime",

3
src/util.h
View File

@ -104,6 +104,7 @@ bool first_word(const char *s, const char *word);
int close_nointr(int fd);
void close_nointr_nofail(int fd);
void close_many(const int fds[], unsigned n_fd);
int parse_boolean(const char *v);
int parse_usec(const char *t, usec_t *usec);
@ -252,7 +253,7 @@ bool is_device_path(const char *path);
int dir_is_empty(const char *path);
extern char * __progname;
void rename_process(const char name[8]);
const char *ioprio_class_to_string(int i);
int ioprio_class_from_string(const char *s);