| /* |
| * Copyright (C) 2016 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #define LOG_TAG "keystore" |
| |
| #include "permissions.h" |
| |
| #include <cutils/log.h> |
| #include <cutils/sockets.h> |
| #include <private/android_filesystem_config.h> |
| |
| #include <selinux/android.h> |
| |
| #include "keystore_utils.h" |
| |
| /* perm_labels associcated with keystore_key SELinux class verbs. */ |
| const char* perm_labels[] = { |
| "get_state", "get", "insert", "delete", "exist", "list", |
| "reset", "password", "lock", "unlock", "is_empty", "sign", |
| "verify", "grant", "duplicate", "clear_uid", "add_auth", "user_changed", |
| }; |
| |
| struct user_euid { |
| uid_t uid; |
| uid_t euid; |
| }; |
| |
| user_euid user_euids[] = { |
| {AID_VPN, AID_SYSTEM}, {AID_WIFI, AID_SYSTEM}, {AID_ROOT, AID_SYSTEM}, |
| }; |
| |
| struct user_perm { |
| uid_t uid; |
| perm_t perms; |
| }; |
| |
| static user_perm user_perms[] = { |
| {AID_SYSTEM, static_cast<perm_t>((uint32_t)(~0))}, |
| {AID_VPN, static_cast<perm_t>(P_GET | P_SIGN | P_VERIFY)}, |
| {AID_WIFI, static_cast<perm_t>(P_GET | P_SIGN | P_VERIFY)}, |
| {AID_ROOT, static_cast<perm_t>(P_GET)}, |
| }; |
| |
| static const perm_t DEFAULT_PERMS = static_cast<perm_t>(P_GET_STATE | P_GET | P_INSERT | P_DELETE | |
| P_EXIST | P_LIST | P_SIGN | P_VERIFY); |
| |
| struct audit_data { |
| pid_t pid; |
| uid_t uid; |
| }; |
| |
| const char* get_perm_label(perm_t perm) { |
| unsigned int index = ffs(perm); |
| if (index > 0 && index <= (sizeof(perm_labels) / sizeof(perm_labels[0]))) { |
| return perm_labels[index - 1]; |
| } else { |
| ALOGE("Keystore: Failed to retrieve permission label.\n"); |
| abort(); |
| } |
| } |
| |
| static int audit_callback(void* data, security_class_t /* cls */, char* buf, size_t len) { |
| struct audit_data* ad = reinterpret_cast<struct audit_data*>(data); |
| if (!ad) { |
| ALOGE("No keystore audit data"); |
| return 0; |
| } |
| |
| snprintf(buf, len, "pid=%d uid=%d", ad->pid, ad->uid); |
| return 0; |
| } |
| |
| static char* tctx; |
| static int ks_is_selinux_enabled; |
| |
| int configure_selinux() { |
| ks_is_selinux_enabled = is_selinux_enabled(); |
| if (ks_is_selinux_enabled) { |
| 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); |
| if (getcon(&tctx) != 0) { |
| ALOGE("SELinux: Could not acquire target context. Aborting keystore.\n"); |
| return -1; |
| } |
| } else { |
| ALOGI("SELinux: Keystore SELinux is disabled.\n"); |
| } |
| |
| return 0; |
| } |
| |
| static bool keystore_selinux_check_access(uid_t uid, perm_t perm, pid_t spid) { |
| if (!ks_is_selinux_enabled) { |
| return true; |
| } |
| |
| audit_data ad; |
| char* sctx = NULL; |
| const char* selinux_class = "keystore_key"; |
| const char* str_perm = get_perm_label(perm); |
| |
| if (!str_perm) { |
| return false; |
| } |
| |
| if (getpidcon(spid, &sctx) != 0) { |
| ALOGE("SELinux: Failed to get source pid context.\n"); |
| return false; |
| } |
| |
| ad.pid = spid; |
| ad.uid = uid; |
| |
| bool allowed = selinux_check_access(sctx, tctx, selinux_class, str_perm, |
| reinterpret_cast<void*>(&ad)) == 0; |
| freecon(sctx); |
| return allowed; |
| } |
| |
| /** |
| * Returns the UID that the callingUid should act as. This is here for |
| * legacy support of the WiFi and VPN systems and should be removed |
| * when WiFi can operate in its own namespace. |
| */ |
| uid_t get_keystore_euid(uid_t uid) { |
| for (size_t i = 0; i < sizeof(user_euids) / sizeof(user_euids[0]); i++) { |
| struct user_euid user = user_euids[i]; |
| if (user.uid == uid) { |
| return user.euid; |
| } |
| } |
| |
| return uid; |
| } |
| |
| bool has_permission(uid_t uid, perm_t perm, pid_t spid) { |
| // All system users are equivalent for multi-user support. |
| if (get_app_id(uid) == AID_SYSTEM) { |
| uid = AID_SYSTEM; |
| } |
| |
| for (size_t i = 0; i < sizeof(user_perms) / sizeof(user_perms[0]); i++) { |
| struct user_perm user = user_perms[i]; |
| if (user.uid == uid) { |
| return (user.perms & perm) && keystore_selinux_check_access(uid, perm, spid); |
| } |
| } |
| |
| return (DEFAULT_PERMS & perm) && keystore_selinux_check_access(uid, perm, spid); |
| } |
| |
| /** |
| * Returns true if the callingUid is allowed to interact in the targetUid's |
| * namespace. |
| */ |
| bool is_granted_to(uid_t callingUid, uid_t targetUid) { |
| if (callingUid == targetUid) { |
| return true; |
| } |
| for (size_t i = 0; i < sizeof(user_euids) / sizeof(user_euids[0]); i++) { |
| struct user_euid user = user_euids[i]; |
| if (user.euid == callingUid && user.uid == targetUid) { |
| return true; |
| } |
| } |
| |
| return false; |
| } |