1 /* 2 * Copyright 2015 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 #ifndef GATEKEEPER_H_ 18 #define GATEKEEPER_H_ 19 20 #include <stdint.h> 21 #include <gatekeeper/UniquePtr.h> 22 #include <hardware/hw_auth_token.h> 23 24 #include "gatekeeper_messages.h" 25 #include "password_handle.h" 26 27 namespace gatekeeper { 28 29 struct __attribute__((packed)) failure_record_t { 30 uint64_t secure_user_id; 31 uint64_t last_checked_timestamp; 32 uint32_t failure_counter; 33 }; 34 35 /** 36 * Base class for gatekeeper implementations. Provides all functionality except 37 * the ability to create/access keys and compute signatures. These are left up 38 * to the platform-specific implementation. 39 */ 40 class GateKeeper { 41 public: GateKeeper()42 GateKeeper() {} ~GateKeeper()43 virtual ~GateKeeper() {} 44 45 void Enroll(const EnrollRequest &request, EnrollResponse *response); 46 void Verify(const VerifyRequest &request, VerifyResponse *response); 47 void DeleteUser(const DeleteUserRequest &request, DeleteUserResponse *response); 48 void DeleteAllUsers(const DeleteAllUsersRequest &request, DeleteAllUsersResponse *response); 49 50 protected: 51 52 // The following methods are intended to be implemented by concrete subclasses 53 54 /** 55 * Retrieves the key used by GateKeeper::MintAuthToken to sign the payload 56 * of the AuthToken. This is not cached as is may have changed due to an event such 57 * as a password change. 58 * 59 * Writes the length in bytes of the returned key to length if it is not null. 60 * 61 * Ownership of the auth_token_key pointer is maintained by the implementor. 62 * 63 * Returns true if the key was successfully fetched. 64 * 65 */ 66 virtual bool GetAuthTokenKey(const uint8_t **auth_token_key, uint32_t *length) 67 const = 0; 68 69 /** 70 * The key used to sign and verify password data. 71 * 72 * MUST be different from the AuthTokenKey. 73 * 74 * GetPasswordKey is not const because unlike AuthTokenKey, 75 * this value can be cached. 76 * 77 * Ownership of the password_key pointer is maintained by the implementor. 78 * 79 */ 80 virtual void GetPasswordKey(const uint8_t **password_key, uint32_t *length) = 0; 81 82 /** 83 * Uses platform-specific routines to compute a signature on the provided password. 84 * 85 * This can be implemented as a simple pass-through to ComputeSignature, but is 86 * available in case handling for password signatures is different from general 87 * purpose signatures. 88 * 89 * Writes the signature_length size signature to the 'signature' pointer. 90 */ 91 virtual void ComputePasswordSignature(uint8_t *signature, uint32_t signature_length, 92 const uint8_t *key, uint32_t key_length, const uint8_t *password, 93 uint32_t password_length, salt_t salt) const = 0; 94 95 /** 96 * Retrieves a unique, cryptographically randomly generated buffer for use in password 97 * hashing, etc. 98 * 99 * Assings the random to the random UniquePtr, relinquishing ownership to the caller 100 */ 101 virtual void GetRandom(void *random, uint32_t requested_size) const = 0; 102 103 /** 104 * Uses platform-specific routines to compute a signature on the provided message. 105 * 106 * Writes the signature_length size signature to the 'signature' pointer. 107 */ 108 virtual void ComputeSignature(uint8_t *signature, uint32_t signature_length, 109 const uint8_t *key, uint32_t key_length, const uint8_t *message, 110 const uint32_t length) const = 0; 111 112 /** 113 * Get the time since boot in milliseconds. 114 * 115 * Should return 0 on error. 116 */ 117 virtual uint64_t GetMillisecondsSinceBoot() const = 0; 118 119 /** 120 * Removes all records for the given user. 121 * 122 * Returns true if the user's records were successfully deleted. 123 */ RemoveUser(uint32_t)124 virtual gatekeeper_error_t RemoveUser(uint32_t /* uid */) { return ERROR_NOT_IMPLEMENTED; } 125 126 /** 127 * Removes all records. 128 * 129 * Returns true if the records were successfully deleted. 130 */ RemoveAllUsers()131 virtual gatekeeper_error_t RemoveAllUsers() { return ERROR_NOT_IMPLEMENTED; } 132 133 /** 134 * Returns the value of the current failure record for the user. 135 * 136 * The failure record should be written to hardware-backed secure storage, such as 137 * RPMB, if the target device supports it. 138 * 139 * If 'secure' is false, password is operating in a fallback mode. Implementations 140 * may store the failure record in memory or in non-secure storage if this value is false. 141 * 142 * Returns true on success, false if failure record cannot be retrieved. 143 */ 144 virtual bool GetFailureRecord(uint32_t uid, secure_id_t user_id, failure_record_t *record, 145 bool secure) = 0; 146 147 /** 148 * Initializes or reinitializes the failure record for the current user. 149 * 150 * Must be persisted in secure storage if the target device supports it. 151 * 152 * If 'secure' is false, password is operating in a fallback mode. Implementations 153 * may store the failure record in memory or in non-secure storage if this value is false. 154 * 155 * Returns true if the failure record was successfully persisted. 156 */ 157 virtual bool ClearFailureRecord(uint32_t uid, secure_id_t user_id, bool secure) = 0; 158 159 /* 160 * Writes the provided failure record to persistent storage. 161 * 162 * Must be persisted in secure storage if the target device supports it. 163 * 164 * If 'secure' is false, password is operating in a fallback mode. Implementations 165 * may store the failure record in memory or in non-secure storage if this value is false. 166 * 167 * Returns true if record was successfully written. 168 */ 169 virtual bool WriteFailureRecord(uint32_t uid, failure_record_t *record, bool secure) = 0; 170 171 /** 172 * Computes the amount of time to throttle the user due to the current failure_record 173 * counter. An implementation is provided by the generic GateKeeper, but may be 174 * overriden. 175 */ 176 virtual uint32_t ComputeRetryTimeout(const failure_record_t *record); 177 178 /** 179 * Returns whether the GateKeeper implementation is backed by hardware. 180 */ 181 virtual bool IsHardwareBacked() const = 0; 182 183 /** 184 * Verifies that handle matches password HMAC'ed with the password_key 185 */ 186 virtual bool DoVerify(const password_handle_t *expected_handle, const SizedBuffer &password); 187 188 private: 189 /** 190 * Generates a signed attestation of an authentication event and assings 191 * to auth_token UniquePtr. 192 * The format is consistent with that of hw_auth_token_t. 193 * Also returns the length in length if it is not null. 194 */ 195 gatekeeper_error_t MintAuthToken(SizedBuffer *auth_token, uint64_t timestamp, 196 secure_id_t user_id, secure_id_t authenticator_id, uint64_t challenge); 197 198 /** 199 * Populates password_handle with the data provided and computes HMAC. 200 */ 201 bool CreatePasswordHandle(SizedBuffer *password_handle, salt_t salt, 202 secure_id_t secure_id, secure_id_t authenticator_id, uint8_t handle_version, 203 const SizedBuffer & password); 204 205 /** 206 * Increments the counter on the current failure record for the provided user id. 207 * Sets the last_checked_timestamp to timestamp. Writes the updated record 208 * to *record if not null. 209 * 210 * Returns true if failure record was successfully incremented. 211 */ 212 bool IncrementFailureRecord(uint32_t uid, secure_id_t user_id, uint64_t timestamp, 213 failure_record_t *record, bool secure); 214 215 /** 216 * Determines whether the request is within the current throttle window. 217 * 218 * If the system timer has been reset due to a reboot or otherwise, resets 219 * the throttle window with a base at the current time. 220 * 221 * Returns true if the request is in the throttle window. 222 */ 223 bool ThrottleRequest(uint32_t uid, uint64_t timestamp, 224 failure_record_t *record, bool secure, GateKeeperMessage *response); 225 }; 226 227 } 228 229 #endif // GATEKEEPER_H_ 230