Shawn Willden | 6507c27 | 2016-01-05 22:51:48 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2016 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #define LOG_TAG "keystore" |
| 18 | |
| 19 | #include "permissions.h" |
| 20 | |
| 21 | #include <cutils/log.h> |
| 22 | #include <cutils/sockets.h> |
| 23 | #include <private/android_filesystem_config.h> |
| 24 | |
| 25 | #include <selinux/android.h> |
| 26 | |
| 27 | #include "keystore_utils.h" |
| 28 | |
| 29 | /* perm_labels associcated with keystore_key SELinux class verbs. */ |
| 30 | const char* perm_labels[] = { |
| 31 | "get_state", "get", "insert", "delete", "exist", "list", |
| 32 | "reset", "password", "lock", "unlock", "is_empty", "sign", |
| 33 | "verify", "grant", "duplicate", "clear_uid", "add_auth", "user_changed", |
| 34 | }; |
| 35 | |
| 36 | struct user_euid { |
| 37 | uid_t uid; |
| 38 | uid_t euid; |
| 39 | }; |
| 40 | |
| 41 | user_euid user_euids[] = { |
| 42 | {AID_VPN, AID_SYSTEM}, {AID_WIFI, AID_SYSTEM}, {AID_ROOT, AID_SYSTEM}, |
| 43 | }; |
| 44 | |
| 45 | struct user_perm { |
| 46 | uid_t uid; |
| 47 | perm_t perms; |
| 48 | }; |
| 49 | |
| 50 | static user_perm user_perms[] = { |
| 51 | {AID_SYSTEM, static_cast<perm_t>((uint32_t)(~0))}, |
| 52 | {AID_VPN, static_cast<perm_t>(P_GET | P_SIGN | P_VERIFY)}, |
| 53 | {AID_WIFI, static_cast<perm_t>(P_GET | P_SIGN | P_VERIFY)}, |
| 54 | {AID_ROOT, static_cast<perm_t>(P_GET)}, |
| 55 | }; |
| 56 | |
| 57 | static const perm_t DEFAULT_PERMS = static_cast<perm_t>(P_GET_STATE | P_GET | P_INSERT | P_DELETE | |
| 58 | P_EXIST | P_LIST | P_SIGN | P_VERIFY); |
| 59 | |
| 60 | struct audit_data { |
| 61 | pid_t pid; |
| 62 | uid_t uid; |
| 63 | }; |
| 64 | |
| 65 | const char* get_perm_label(perm_t perm) { |
| 66 | unsigned int index = ffs(perm); |
| 67 | if (index > 0 && index <= (sizeof(perm_labels) / sizeof(perm_labels[0]))) { |
| 68 | return perm_labels[index - 1]; |
| 69 | } else { |
| 70 | ALOGE("Keystore: Failed to retrieve permission label.\n"); |
| 71 | abort(); |
| 72 | } |
| 73 | } |
| 74 | |
| 75 | static int audit_callback(void* data, security_class_t /* cls */, char* buf, size_t len) { |
| 76 | struct audit_data* ad = reinterpret_cast<struct audit_data*>(data); |
| 77 | if (!ad) { |
| 78 | ALOGE("No keystore audit data"); |
| 79 | return 0; |
| 80 | } |
| 81 | |
| 82 | snprintf(buf, len, "pid=%d uid=%d", ad->pid, ad->uid); |
| 83 | return 0; |
| 84 | } |
| 85 | |
| 86 | static char* tctx; |
| 87 | static int ks_is_selinux_enabled; |
| 88 | |
| 89 | int configure_selinux() { |
| 90 | ks_is_selinux_enabled = is_selinux_enabled(); |
| 91 | if (ks_is_selinux_enabled) { |
| 92 | union selinux_callback cb; |
| 93 | cb.func_audit = audit_callback; |
| 94 | selinux_set_callback(SELINUX_CB_AUDIT, cb); |
| 95 | cb.func_log = selinux_log_callback; |
| 96 | selinux_set_callback(SELINUX_CB_LOG, cb); |
| 97 | if (getcon(&tctx) != 0) { |
| 98 | ALOGE("SELinux: Could not acquire target context. Aborting keystore.\n"); |
| 99 | return -1; |
| 100 | } |
| 101 | } else { |
| 102 | ALOGI("SELinux: Keystore SELinux is disabled.\n"); |
| 103 | } |
| 104 | |
| 105 | return 0; |
| 106 | } |
| 107 | |
| 108 | static bool keystore_selinux_check_access(uid_t uid, perm_t perm, pid_t spid) { |
| 109 | if (!ks_is_selinux_enabled) { |
| 110 | return true; |
| 111 | } |
| 112 | |
| 113 | audit_data ad; |
| 114 | char* sctx = NULL; |
| 115 | const char* selinux_class = "keystore_key"; |
| 116 | const char* str_perm = get_perm_label(perm); |
| 117 | |
| 118 | if (!str_perm) { |
| 119 | return false; |
| 120 | } |
| 121 | |
| 122 | if (getpidcon(spid, &sctx) != 0) { |
| 123 | ALOGE("SELinux: Failed to get source pid context.\n"); |
| 124 | return false; |
| 125 | } |
| 126 | |
| 127 | ad.pid = spid; |
| 128 | ad.uid = uid; |
| 129 | |
| 130 | bool allowed = selinux_check_access(sctx, tctx, selinux_class, str_perm, |
| 131 | reinterpret_cast<void*>(&ad)) == 0; |
| 132 | freecon(sctx); |
| 133 | return allowed; |
| 134 | } |
| 135 | |
| 136 | /** |
| 137 | * Returns the UID that the callingUid should act as. This is here for |
| 138 | * legacy support of the WiFi and VPN systems and should be removed |
| 139 | * when WiFi can operate in its own namespace. |
| 140 | */ |
| 141 | uid_t get_keystore_euid(uid_t uid) { |
| 142 | for (size_t i = 0; i < sizeof(user_euids) / sizeof(user_euids[0]); i++) { |
| 143 | struct user_euid user = user_euids[i]; |
| 144 | if (user.uid == uid) { |
| 145 | return user.euid; |
| 146 | } |
| 147 | } |
| 148 | |
| 149 | return uid; |
| 150 | } |
| 151 | |
| 152 | bool has_permission(uid_t uid, perm_t perm, pid_t spid) { |
| 153 | // All system users are equivalent for multi-user support. |
| 154 | if (get_app_id(uid) == AID_SYSTEM) { |
| 155 | uid = AID_SYSTEM; |
| 156 | } |
| 157 | |
| 158 | for (size_t i = 0; i < sizeof(user_perms) / sizeof(user_perms[0]); i++) { |
| 159 | struct user_perm user = user_perms[i]; |
| 160 | if (user.uid == uid) { |
| 161 | return (user.perms & perm) && keystore_selinux_check_access(uid, perm, spid); |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | return (DEFAULT_PERMS & perm) && keystore_selinux_check_access(uid, perm, spid); |
| 166 | } |
| 167 | |
| 168 | /** |
| 169 | * Returns true if the callingUid is allowed to interact in the targetUid's |
| 170 | * namespace. |
| 171 | */ |
| 172 | bool is_granted_to(uid_t callingUid, uid_t targetUid) { |
| 173 | if (callingUid == targetUid) { |
| 174 | return true; |
| 175 | } |
| 176 | for (size_t i = 0; i < sizeof(user_euids) / sizeof(user_euids[0]); i++) { |
| 177 | struct user_euid user = user_euids[i]; |
| 178 | if (user.euid == callingUid && user.uid == targetUid) { |
| 179 | return true; |
| 180 | } |
| 181 | } |
| 182 | |
| 183 | return false; |
| 184 | } |