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liblog: gate write on log id available 

- Secure LOG_ID_KERNEL in writer
- Secure LOG_ID_SECURITY in reader and writer
- if writer transport says not available, do not write to that log id

Bug: 27566046
Bug: 27896341
Change-Id: If63a78a56fb94adfbf9979454c4cadb81af45c19
This commit is contained in:
Mark Salyzyn 2016-03-28 16:20:29 -07:00
parent d8c88fc5e3
commit c33103c440
4 changed files with 100 additions and 61 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
liblog/logd_writer.c
View File

@ -105,12 +105,6 @@ static int logdAvailable(log_id_t logId)
if (logId > LOG_ID_SECURITY) {
return -EINVAL;
}
if (logId == LOG_ID_SECURITY) {
uid_t uid = __android_log_uid();
if ((uid != AID_LOG) && (uid != AID_ROOT) && (uid != AID_SYSTEM)) {
return -EPERM;
}
}
if (logdLoggerWrite.context.sock < 0) {
if (access("/dev/socket/logdw", W_OK) == 0) {
return 0;

1
liblog/logger.h
View File

@ -40,6 +40,7 @@ union android_log_context {
struct android_log_transport_write {
struct listnode node;
const char *name;
unsigned logMask; /* cache of available success */
union android_log_context context; /* Initialized by static allocation */
int (*available)(log_id_t logId);

5
liblog/logger_read.c
View File

@ -26,6 +26,7 @@
#include <cutils/list.h>
#include <log/log.h>
#include <log/logger.h>
#include <private/android_filesystem_config.h>
#include "config_read.h"
#include "log_portability.h"
@ -91,6 +92,10 @@ static int init_transport_context(struct android_log_logger_list *logger_list)
logger_for_each(logger, logger_list) {
log_id_t logId = logger->logId;
if ((logId == LOG_ID_SECURITY) &&
(__android_log_uid() != AID_SYSTEM)) {
continue;
}
if (transport->read &&
(!transport->available ||
(transport->available(logId) >= 0))) {

149
liblog/logger_write.c
View File

@ -49,20 +49,85 @@ static enum {
kLogUninitialized, kLogNotAvailable, kLogAvailable
} g_log_status = kLogUninitialized;
static int check_log_uid_permissions()
{
#if defined(__BIONIC__)
uid_t uid = __android_log_uid();
/* Matches clientHasLogCredentials() in logd */
if ((uid != AID_SYSTEM) && (uid != AID_ROOT) && (uid != AID_LOG)) {
uid = geteuid();
if ((uid != AID_SYSTEM) && (uid != AID_ROOT) && (uid != AID_LOG)) {
gid_t gid = getgid();
if ((gid != AID_SYSTEM) &&
(gid != AID_ROOT) &&
(gid != AID_LOG)) {
gid = getegid();
if ((gid != AID_SYSTEM) &&
(gid != AID_ROOT) &&
(gid != AID_LOG)) {
int num_groups;
gid_t *groups;
num_groups = getgroups(0, NULL);
if (num_groups <= 0) {
return -EPERM;
}
groups = calloc(num_groups, sizeof(gid_t));
if (!groups) {
return -ENOMEM;
}
num_groups = getgroups(num_groups, groups);
while (num_groups > 0) {
if (groups[num_groups - 1] == AID_LOG) {
break;
}
--num_groups;
}
free(groups);
if (num_groups <= 0) {
return -EPERM;
}
}
}
}
}
#endif
return 0;
}
static void __android_log_cache_available(
struct android_log_transport_write *node)
{
size_t i;
if (node->logMask) {
return;
}
for (i = LOG_ID_MIN; i < LOG_ID_MAX; ++i) {
if (node->write &&
(i != LOG_ID_KERNEL) &&
((i != LOG_ID_SECURITY) ||
(check_log_uid_permissions() == 0)) &&
(!node->available || ((*node->available)(i) >= 0))) {
node->logMask |= 1 << i;
}
}
}
LIBLOG_ABI_PUBLIC int __android_log_dev_available()
{
struct android_log_transport_write *node;
size_t i;
if (list_empty(&__android_log_transport_write)) {
return kLogUninitialized;
}
for (i = LOG_ID_MIN; i < LOG_ID_MAX; ++i) {
write_transport_for_each(node, &__android_log_transport_write) {
if (node->write &&
(!node->available || ((*node->available)(i) >= 0))) {
return kLogAvailable;
}
write_transport_for_each(node, &__android_log_transport_write) {
__android_log_cache_available(node);
if (node->logMask) {
return kLogAvailable;
}
}
return kLogNotAvailable;
@ -77,6 +142,11 @@ static int __write_to_log_initialize()
__android_log_config_write();
write_transport_for_each_safe(transport, n, &__android_log_transport_write) {
__android_log_cache_available(transport);
if (!transport->logMask) {
list_remove(&transport->node);
continue;
}
if (!transport->open || ((*transport->open)() < 0)) {
if (transport->close) {
(*transport->close)();
@ -87,6 +157,11 @@ static int __write_to_log_initialize()
++ret;
}
write_transport_for_each_safe(transport, n, &__android_log_persist_write) {
__android_log_cache_available(transport);
if (!transport->logMask) {
list_remove(&transport->node);
continue;
}
if (!transport->open || ((*transport->open)() < 0)) {
if (transport->close) {
(*transport->close)();
@ -127,50 +202,13 @@ static int __write_to_log_daemon(log_id_t log_id, struct iovec *vec, size_t nr)
#if defined(__BIONIC__)
if (log_id == LOG_ID_SECURITY) {
uid_t uid;
if (vec[0].iov_len < 4) {
return -EINVAL;
}
uid = __android_log_uid();
/* Matches clientHasLogCredentials() in logd */
if ((uid != AID_SYSTEM) && (uid != AID_ROOT) && (uid != AID_LOG)) {
uid = geteuid();
if ((uid != AID_SYSTEM) && (uid != AID_ROOT) && (uid != AID_LOG)) {
gid_t gid = getgid();
if ((gid != AID_SYSTEM) &&
(gid != AID_ROOT) &&
(gid != AID_LOG)) {
gid = getegid();
if ((gid != AID_SYSTEM) &&
(gid != AID_ROOT) &&
(gid != AID_LOG)) {
int num_groups;
gid_t *groups;
num_groups = getgroups(0, NULL);
if (num_groups <= 0) {
return -EPERM;
}
groups = calloc(num_groups, sizeof(gid_t));
if (!groups) {
return -ENOMEM;
}
num_groups = getgroups(num_groups, groups);
while (num_groups > 0) {
if (groups[num_groups - 1] == AID_LOG) {
break;
}
--num_groups;
}
free(groups);
if (num_groups <= 0) {
return -EPERM;
}
}
}
}
ret = check_log_uid_permissions();
if (ret < 0) {
return ret;
}
if (!__android_log_security()) {
/* If only we could reset downstream logd counter */
@ -262,8 +300,9 @@ static int __write_to_log_daemon(log_id_t log_id, struct iovec *vec, size_t nr)
#endif
ret = 0;
i = 1 << log_id;
write_transport_for_each(node, &__android_log_transport_write) {
if (node->write) {
if (node->logMask & i) {
ssize_t retval;
retval = (*node->write)(log_id, &ts, vec, nr);
if (ret >= 0) {
@ -273,7 +312,7 @@ static int __write_to_log_daemon(log_id_t log_id, struct iovec *vec, size_t nr)
}
write_transport_for_each(node, &__android_log_persist_write) {
if (node->write) {
if (node->logMask & i) {
(void)(*node->write)(log_id, &ts, vec, nr);
}
}
@ -343,12 +382,12 @@ LIBLOG_ABI_PUBLIC int __android_log_buf_write(int bufID, int prio,
}
#endif
vec[0].iov_base = (unsigned char *) &prio;
vec[0].iov_len = 1;
vec[1].iov_base = (void *) tag;
vec[1].iov_len = strlen(tag) + 1;
vec[2].iov_base = (void *) msg;
vec[2].iov_len = strlen(msg) + 1;
vec[0].iov_base = (unsigned char *)&prio;
vec[0].iov_len = 1;
vec[1].iov_base = (void *)tag;
vec[1].iov_len = strlen(tag) + 1;
vec[2].iov_base = (void *)msg;
vec[2].iov_len = strlen(msg) + 1;
return write_to_log(bufID, vec, 3);
}