From 69154df9efd3ffb7580b72a0138f58a2f5443db6 Mon Sep 17 00:00:00 2001 From: Riley Spahn Date: Thu, 5 Jun 2014 11:07:18 -0700 Subject: [PATCH] Add SELinux checks when adding a service. Add a MAC check to the svc_can_register function in service_manager. The types are defined in external/sepolicy/service.te and the mapping from service names is defined in external/sepolicy/service_contexts. Currently uses the property context backend to parse the contexts file. Bug: 12909011 Change-Id: I5d90a614263c60571c7c70c2882e6fa929911ca5 --- cmds/servicemanager/Android.mk | 2 +- cmds/servicemanager/service_manager.c | 90 +++++++++++++++++++++++++-- 2 files changed, 85 insertions(+), 7 deletions(-) diff --git a/cmds/servicemanager/Android.mk b/cmds/servicemanager/Android.mk index 4ab8df68f..155cfc503 100644 --- a/cmds/servicemanager/Android.mk +++ b/cmds/servicemanager/Android.mk @@ -18,7 +18,7 @@ LOCAL_MODULE_TAGS := optional include $(BUILD_EXECUTABLE) include $(CLEAR_VARS) -LOCAL_SHARED_LIBRARIES := liblog +LOCAL_SHARED_LIBRARIES := liblog libselinux LOCAL_SRC_FILES := service_manager.c binder.c LOCAL_CFLAGS += $(svc_c_flags) LOCAL_MODULE := servicemanager diff --git a/cmds/servicemanager/service_manager.c b/cmds/servicemanager/service_manager.c index 79ce6eda5..939920a31 100644 --- a/cmds/servicemanager/service_manager.c +++ b/cmds/servicemanager/service_manager.c @@ -8,6 +8,8 @@ #include +#include + #include "binder.h" #if 0 @@ -76,16 +78,67 @@ int str16eq(const uint16_t *a, const char *b) return 1; } -int svc_can_register(uid_t uid, const uint16_t *name) +static struct selabel_handle* sehandle; + +static bool check_mac_perms(const char *name, pid_t spid) +{ + if (is_selinux_enabled() <= 0) { + return true; + } + + bool allowed = false; + + const char *class = "service_manager"; + const char *perm = "add"; + + char *tctx = NULL; + char *sctx = NULL; + + if (!sehandle) { + ALOGE("SELinux: Failed to find sehandle %s.\n", name); + return false; + } + + if (getpidcon(spid, &sctx) < 0) { + ALOGE("SELinux: getpidcon failed to retrieve pid context.\n"); + return false; + } + + if (!sctx) { + ALOGE("SELinux: Failed to find sctx for %s.\n", name); + return false; + } + + if (selabel_lookup(sehandle, &tctx, name, 1) != 0) { + ALOGE("SELinux: selabel_lookup failed to set tctx for %s.\n", name); + freecon(sctx); + return false; + } + + if (!tctx) { + ALOGE("SELinux: Failed to find tctx for %s.\n", name); + freecon(sctx); + return false; + } + + int result = selinux_check_access(sctx, tctx, class, perm, (void *) name); + allowed = (result == 0); + + freecon(sctx); + freecon(tctx); + return allowed; +} + +static int svc_can_register(uid_t uid, const uint16_t *name, pid_t spid) { size_t n; if ((uid == 0) || (uid == AID_SYSTEM)) - return 1; + return check_mac_perms(str8(name), spid) ? 1 : 0; for (n = 0; n < sizeof(allowed) / sizeof(allowed[0]); n++) if ((uid == allowed[n].uid) && str16eq(name, allowed[n].name)) - return 1; + return check_mac_perms(str8(name), spid) ? 1 : 0; return 0; } @@ -155,7 +208,8 @@ uint32_t do_find_service(struct binder_state *bs, const uint16_t *s, size_t len, int do_add_service(struct binder_state *bs, const uint16_t *s, size_t len, - uint32_t handle, uid_t uid, int allow_isolated) + uint32_t handle, uid_t uid, int allow_isolated, + pid_t spid) { struct svcinfo *si; @@ -165,7 +219,7 @@ int do_add_service(struct binder_state *bs, if (!handle || (len == 0) || (len > 127)) return -1; - if (!svc_can_register(uid, s)) { + if (!svc_can_register(uid, s, spid)) { ALOGE("add_service('%s',%x) uid=%d - PERMISSION DENIED\n", str8(s), handle, uid); return -1; @@ -235,6 +289,14 @@ int svcmgr_handler(struct binder_state *bs, return -1; } + if (sehandle && selinux_status_updated() > 0) { + struct selabel_handle *tmp_sehandle = selinux_android_service_context_handle(); + if (tmp_sehandle) { + selabel_close(sehandle); + sehandle = tmp_sehandle; + } + } + switch(txn->code) { case SVC_MGR_GET_SERVICE: case SVC_MGR_CHECK_SERVICE: @@ -249,7 +311,8 @@ int svcmgr_handler(struct binder_state *bs, s = bio_get_string16(msg, &len); handle = bio_get_ref(msg); allow_isolated = bio_get_uint32(msg) ? 1 : 0; - if (do_add_service(bs, s, len, handle, txn->sender_euid, allow_isolated)) + if (do_add_service(bs, s, len, handle, txn->sender_euid, + allow_isolated, txn->sender_pid)) return -1; break; @@ -274,6 +337,13 @@ int svcmgr_handler(struct binder_state *bs, return 0; } + +static int audit_callback(void *data, security_class_t cls, char *buf, size_t len) +{ + snprintf(buf, len, "service=%s", !data ? "NULL" : (char *)data); + return 0; +} + int main(int argc, char **argv) { struct binder_state *bs; @@ -289,6 +359,14 @@ int main(int argc, char **argv) return -1; } + sehandle = selinux_android_service_context_handle(); + + union selinux_callback cb; + cb.func_audit = audit_callback; + selinux_set_callback(SELINUX_CB_AUDIT, cb); + cb.func_log = selinux_log_callback; + selinux_set_callback(SELINUX_CB_LOG, cb); + svcmgr_handle = BINDER_SERVICE_MANAGER; binder_loop(bs, svcmgr_handler);