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support file-based capabilities instead of SUID root for giving PA rights to acquire RT/HP scheduling: setcap cap_sys_nice=ep /usr/bin/pulseaudio

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This commit is contained in:
Lennart Poettering 2008-06-22 01:48:46 +02:00
parent ab93f2a087
commit 8885ddf716
3 changed files with 48 additions and 17 deletions
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31
src/daemon/caps.c
View file

@ -91,13 +91,18 @@ void pa_limit_caps(void) {
pa_assert_se(cap_clear(caps) == 0);
pa_assert_se(cap_set_flag(caps, CAP_EFFECTIVE, 1, &nice_cap, CAP_SET) == 0);
pa_assert_se(cap_set_flag(caps, CAP_PERMITTED, 1, &nice_cap, CAP_SET) == 0);
pa_assert_se(cap_set_proc(caps) == 0);
pa_assert_se(prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) == 0);
pa_log_info("Dropped capabilities successfully.");
if (cap_set_proc(caps) < 0)
/* Hmm, so we couldn't limit our caps, which probably means we
* hadn't any in the first place, so let's just make sure of
* that */
pa_drop_caps();
else
pa_log_info("Limited capabilities successfully to CAP_SYS_NICE.");
pa_assert_se(cap_free(caps) == 0);
pa_assert_se(prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) == 0);
}
/* Drop all capabilities, effectively becoming a normal user */
@ -110,17 +115,33 @@ void pa_drop_caps(void) {
pa_assert_se(cap_clear(caps) == 0);
pa_assert_se(cap_set_proc(caps) == 0);
pa_assert_se(cap_free(caps) == 0);
pa_assert_se(!pa_have_caps());
}
pa_bool_t pa_have_caps(void) {
cap_t caps;
cap_flag_value_t flag = CAP_CLEAR;
pa_assert_se(caps = cap_get_proc());
pa_assert_se(cap_get_flag(caps, CAP_SYS_NICE, CAP_EFFECTIVE, &flag) >= 0);
pa_assert_se(cap_free(caps) == 0);
return flag == CAP_SET;
}
#else
/* NOOPs in case capabilities are not available. */
void pa_limit_caps(void) {
return 0;
}
void pa_drop_caps(void) {
pa_drop_root();
}
pa_bool_t pa_have_caps(void) {
return FALSE;
}
#endif

3
src/daemon/caps.h
View file

@ -22,8 +22,11 @@
USA.
***/
#include <pulsecore/macro.h>
void pa_drop_root(void);
void pa_drop_caps(void);
void pa_limit_caps(void);
pa_bool_t pa_have_caps(void);
#endif

31
src/daemon/main.c
View file

@ -374,7 +374,7 @@ int main(int argc, char *argv[]) {
suid_root = FALSE;
#endif
if (suid_root) {
if (!real_root) {
/* Drop all capabilities except CAP_SYS_NICE */
pa_limit_caps();
@ -426,20 +426,26 @@ int main(int argc, char *argv[]) {
pa_log_set_maximal_level(conf->log_level);
pa_log_set_target(conf->auto_log_target ? PA_LOG_STDERR : conf->log_target, NULL);
if (suid_root) {
pa_bool_t allow_realtime, allow_high_priority;
pa_log_debug("Started as real root: %s, suid root: %s", pa_yes_no(real_root), pa_yes_no(suid_root));
/* Ok, we're suid root, so let's better not enable high prio
* or RT by default */
if (!real_root && pa_have_caps()) {
pa_bool_t allow_high_priority = FALSE, allow_realtime = FALSE;
allow_high_priority = allow_realtime = FALSE;
/* Let's better not enable high prio or RT by default */
if (conf->high_priority || conf->realtime_scheduling)
if (conf->high_priority && !allow_high_priority) {
if (pa_own_uid_in_group(PA_REALTIME_GROUP, &gid) > 0) {
pa_log_info("We're in the group '"PA_REALTIME_GROUP"', allowing real-time and high-priority scheduling.");
allow_realtime = conf->realtime_scheduling;
allow_high_priority = conf->high_priority;
pa_log_info("We're in the group '"PA_REALTIME_GROUP"', allowing high-priority scheduling.");
allow_high_priority = TRUE;
}
}
if (conf->realtime_scheduling && !allow_realtime) {
if (pa_own_uid_in_group(PA_REALTIME_GROUP, &gid) > 0) {
pa_log_info("We're in the group '"PA_REALTIME_GROUP"', allowing real-time scheduling.");
allow_realtime = TRUE;
}
}
#ifdef HAVE_POLKIT
if (conf->high_priority && !allow_high_priority) {
@ -465,7 +471,6 @@ int main(int argc, char *argv[]) {
* let's give it up early */
pa_drop_caps();
suid_root = FALSE;
if (conf->high_priority || conf->realtime_scheduling)
pa_log_notice("Called SUID root and real-time/high-priority scheduling was requested in the configuration. However, we lack the necessary priviliges:\n"
@ -491,7 +496,7 @@ int main(int argc, char *argv[]) {
if (conf->high_priority && (conf->cmd == PA_CMD_DAEMON || conf->cmd == PA_CMD_START))
pa_raise_priority(conf->nice_level);
if (suid_root) {
if (pa_have_caps()) {
pa_bool_t drop;
drop = (conf->cmd != PA_CMD_DAEMON && conf->cmd != PA_CMD_START) || !conf->realtime_scheduling;
@ -530,6 +535,8 @@ int main(int argc, char *argv[]) {
if (conf->realtime_scheduling && !pa_can_realtime())
pa_log_warn("Real-time scheduling enabled in configuration but not allowed by policy.");
pa_log_debug("Can realtime: %s, can high-priority: %s", pa_yes_no(pa_can_realtime()), pa_yes_no(pa_can_high_priority()));
LTDL_SET_PRELOADED_SYMBOLS();
pa_ltdl_init();
ltdl_init = TRUE;