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/*
* Copyright 2015 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.
*/
#include <UniquePtr.h>
#include <gatekeeper/gatekeeper.h>
namespace gatekeeper {
void GateKeeper::Enroll(const EnrollRequest &request, EnrollResponse *response) {
if (response == NULL) return;
if (!request.provided_password.buffer.get()) {
response->error = ERROR_INVALID;
return;
}
secure_id_t user_id = 0;
if (request.password_handle.buffer.get() == NULL) {
// Password handle does not match what is stored, generate new SecureID
GetRandom(&user_id, sizeof(secure_id_t));
} else {
if (!ValidatePasswordFile(request.user_id, request.password_handle)) {
response->error = ERROR_INVALID;
return;
} else {
// Password handle matches password file
password_handle_t *pw_handle =
reinterpret_cast<password_handle_t *>(request.password_handle.buffer.get());
if (!DoVerify(pw_handle, request.enrolled_password)) {
// incorrect old password
response->error = ERROR_INVALID;
return;
}
user_id = pw_handle->user_id;
}
}
salt_t salt;
GetRandom(&salt, sizeof(salt));
secure_id_t authenticator_id;
GetRandom(&authenticator_id, sizeof(authenticator_id));
SizedBuffer password_handle;
if(!CreatePasswordHandle(&password_handle,
salt, user_id, authenticator_id, request.provided_password.buffer.get(),
request.provided_password.length)) {
response->error = ERROR_INVALID;
return;
}
WritePasswordFile(request.user_id, password_handle);
response->SetEnrolledPasswordHandle(&password_handle);
}
void GateKeeper::Verify(const VerifyRequest &request, VerifyResponse *response) {
if (response == NULL) return;
if (!request.provided_password.buffer.get() || !request.password_handle.buffer.get()) {
response->error = ERROR_INVALID;
return;
}
secure_id_t user_id, authenticator_id;
password_handle_t *password_handle = reinterpret_cast<password_handle_t *>(
request.password_handle.buffer.get());
// Sanity check
if (password_handle->version != HANDLE_VERSION) {
response->error = ERROR_INVALID;
return;
}
if (!ValidatePasswordFile(request.user_id, request.password_handle)) {
// we don't allow access to keys if we can't validate the file.
// we must allow this case to support authentication before we decrypt
// /data, however.
user_id = 0;
authenticator_id = 0;
} else {
user_id = password_handle->user_id;
authenticator_id = password_handle->authenticator_id;
}
uint64_t timestamp = GetNanosecondsSinceBoot();
if (DoVerify(password_handle, request.provided_password)) {
// Signature matches
SizedBuffer auth_token;
MintAuthToken(&auth_token.buffer, &auth_token.length, timestamp,
user_id, authenticator_id);
response->SetVerificationToken(&auth_token);
} else {
response->error = ERROR_INVALID;
}
}
bool GateKeeper::CreatePasswordHandle(SizedBuffer *password_handle_buffer, salt_t salt,
secure_id_t user_id, secure_id_t authenticator_id, const uint8_t *password,
uint32_t password_length) {
password_handle_buffer->buffer.reset(new uint8_t[sizeof(password_handle_t)]);
password_handle_buffer->length = sizeof(password_handle_t);
password_handle_t *password_handle = reinterpret_cast<password_handle_t *>(
password_handle_buffer->buffer.get());
password_handle->version = HANDLE_VERSION;
password_handle->salt = salt;
password_handle->user_id = user_id;
password_handle->authenticator_id = authenticator_id;
uint32_t metadata_length = sizeof(user_id) /* user id */
+ sizeof(authenticator_id) /* auth id */ + sizeof(uint8_t) /* version */;
uint8_t to_sign[password_length + metadata_length];
memcpy(to_sign, &password_handle->version, metadata_length);
memcpy(to_sign + metadata_length, password, password_length);
const uint8_t *password_key = NULL;
uint32_t password_key_length = 0;
GetPasswordKey(&password_key, &password_key_length);
if (!password_key || password_key_length == 0) {
return false;
}
ComputePasswordSignature(password_handle->signature, sizeof(password_handle->signature),
password_key, password_key_length, to_sign, sizeof(to_sign), salt);
return true;
}
bool GateKeeper::DoVerify(const password_handle_t *expected_handle, const SizedBuffer &password) {
if (!password.buffer.get()) return false;
SizedBuffer provided_handle;
if (!CreatePasswordHandle(&provided_handle, expected_handle->salt, expected_handle->user_id,
expected_handle->authenticator_id, password.buffer.get(), password.length)) {
return false;
}
return memcmp_s(provided_handle.buffer.get(), expected_handle, sizeof(*expected_handle)) == 0;
}
bool GateKeeper::ValidatePasswordFile(uint32_t uid, const SizedBuffer &provided_handle) {
SizedBuffer stored_handle;
ReadPasswordFile(uid, &stored_handle);
if (!stored_handle.buffer.get() || stored_handle.length == 0) return false;
// do we also verify the signature here?
return stored_handle.length == provided_handle.length &&
memcmp_s(stored_handle.buffer.get(), provided_handle.buffer.get(), stored_handle.length)
== 0;
}
void GateKeeper::MintAuthToken(UniquePtr<uint8_t> *auth_token, uint32_t *length,
uint32_t timestamp, secure_id_t user_id, secure_id_t authenticator_id) {
if (auth_token == NULL) return;
AuthToken *token = new AuthToken;
SizedBuffer serialized_auth_token;
token->auth_token_version = AUTH_TOKEN_VERSION;
token->root_secure_user_id = user_id;
token->auxiliary_secure_user_id = authenticator_id;
token->authenticator_id = 0;
token->timestamp = timestamp;
const uint8_t *auth_token_key = NULL;
uint32_t key_len = 0;
GetAuthTokenKey(&auth_token_key, &key_len);
uint32_t hash_len = (uint32_t)((uint8_t *)&token->hmac - (uint8_t *)token);
ComputeSignature(token->hmac, sizeof(token->hmac), auth_token_key, key_len,
reinterpret_cast<uint8_t *>(token), hash_len);
if (length != NULL) *length = sizeof(AuthToken);
auth_token->reset(reinterpret_cast<uint8_t *>(token));
}
}
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