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
18#ifndef SOFT_GATEKEEPER_H_
19#define SOFT_GATEKEEPER_H_
20
21extern "C" {
22#include <openssl/rand.h>
23#include <openssl/sha.h>
24
25#include <crypto_scrypt.h>
26}
27
28#include <android-base/memory.h>
29#include <gatekeeper/gatekeeper.h>
30
31#include <iostream>
32#include <unordered_map>
33#include <memory>
34
35namespace gatekeeper {
36
37struct fast_hash_t {
38    uint64_t salt;
39    uint8_t digest[SHA256_DIGEST_LENGTH];
40};
41
42class SoftGateKeeper : public GateKeeper {
43public:
44    static const uint32_t SIGNATURE_LENGTH_BYTES = 32;
45
46    // scrypt params
47    static const uint64_t N = 16384;
48    static const uint32_t r = 8;
49    static const uint32_t p = 1;
50
51    static const int MAX_UINT_32_CHARS = 11;
52
53    SoftGateKeeper() {
54        key_.reset(new uint8_t[SIGNATURE_LENGTH_BYTES]);
55        memset(key_.get(), 0, SIGNATURE_LENGTH_BYTES);
56    }
57
58    virtual ~SoftGateKeeper() {
59    }
60
61    virtual bool GetAuthTokenKey(const uint8_t **auth_token_key,
62            uint32_t *length) const {
63        if (auth_token_key == NULL || length == NULL) return false;
64        uint8_t *auth_token_key_copy = new uint8_t[SIGNATURE_LENGTH_BYTES];
65        memcpy(auth_token_key_copy, key_.get(), SIGNATURE_LENGTH_BYTES);
66
67        *auth_token_key = auth_token_key_copy;
68        *length = SIGNATURE_LENGTH_BYTES;
69        return true;
70    }
71
72    virtual void GetPasswordKey(const uint8_t **password_key, uint32_t *length) {
73        if (password_key == NULL || length == NULL) return;
74        uint8_t *password_key_copy = new uint8_t[SIGNATURE_LENGTH_BYTES];
75        memcpy(password_key_copy, key_.get(), SIGNATURE_LENGTH_BYTES);
76
77        *password_key = password_key_copy;
78        *length = SIGNATURE_LENGTH_BYTES;
79    }
80
81    virtual void ComputePasswordSignature(uint8_t *signature, uint32_t signature_length,
82            const uint8_t *, uint32_t, const uint8_t *password,
83            uint32_t password_length, salt_t salt) const {
84        if (signature == NULL) return;
85        crypto_scrypt(password, password_length, reinterpret_cast<uint8_t *>(&salt),
86                sizeof(salt), N, r, p, signature, signature_length);
87    }
88
89    virtual void GetRandom(void *random, uint32_t requested_length) const {
90        if (random == NULL) return;
91        RAND_pseudo_bytes((uint8_t *) random, requested_length);
92    }
93
94    virtual void ComputeSignature(uint8_t *signature, uint32_t signature_length,
95            const uint8_t *, uint32_t, const uint8_t *, const uint32_t) const {
96        if (signature == NULL) return;
97        memset(signature, 0, signature_length);
98    }
99
100    virtual uint64_t GetMillisecondsSinceBoot() const {
101        struct timespec time;
102        int res = clock_gettime(CLOCK_BOOTTIME, &time);
103        if (res < 0) return 0;
104        return (time.tv_sec * 1000) + (time.tv_nsec / 1000 / 1000);
105    }
106
107    virtual bool IsHardwareBacked() const {
108        return false;
109    }
110
111    virtual bool GetFailureRecord(uint32_t uid, secure_id_t user_id, failure_record_t *record,
112            bool /* secure */) {
113        failure_record_t *stored = &failure_map_[uid];
114        if (user_id != stored->secure_user_id) {
115            stored->secure_user_id = user_id;
116            stored->last_checked_timestamp = 0;
117            stored->failure_counter = 0;
118        }
119        memcpy(record, stored, sizeof(*record));
120        return true;
121    }
122
123    virtual bool ClearFailureRecord(uint32_t uid, secure_id_t user_id, bool /* secure */) {
124        failure_record_t *stored = &failure_map_[uid];
125        stored->secure_user_id = user_id;
126        stored->last_checked_timestamp = 0;
127        stored->failure_counter = 0;
128        return true;
129    }
130
131    virtual bool WriteFailureRecord(uint32_t uid, failure_record_t *record, bool /* secure */) {
132        failure_map_[uid] = *record;
133        return true;
134    }
135
136    fast_hash_t ComputeFastHash(const SizedBuffer &password, uint64_t salt) {
137        fast_hash_t fast_hash;
138        size_t digest_size = password.length + sizeof(salt);
139        std::unique_ptr<uint8_t[]> digest(new uint8_t[digest_size]);
140        memcpy(digest.get(), &salt, sizeof(salt));
141        memcpy(digest.get() + sizeof(salt), password.buffer.get(), password.length);
142
143        SHA256(digest.get(), digest_size, (uint8_t *) &fast_hash.digest);
144
145        fast_hash.salt = salt;
146        return fast_hash;
147    }
148
149    bool VerifyFast(const fast_hash_t &fast_hash, const SizedBuffer &password) {
150        fast_hash_t computed = ComputeFastHash(password, fast_hash.salt);
151        return memcmp(computed.digest, fast_hash.digest, SHA256_DIGEST_LENGTH) == 0;
152    }
153
154    bool DoVerify(const password_handle_t *expected_handle, const SizedBuffer &password) {
155        uint64_t user_id = android::base::get_unaligned<secure_id_t>(&expected_handle->user_id);
156        FastHashMap::const_iterator it = fast_hash_map_.find(user_id);
157        if (it != fast_hash_map_.end() && VerifyFast(it->second, password)) {
158            return true;
159        } else {
160            if (GateKeeper::DoVerify(expected_handle, password)) {
161                uint64_t salt;
162                GetRandom(&salt, sizeof(salt));
163                fast_hash_map_[user_id] = ComputeFastHash(password, salt);
164                return true;
165            }
166        }
167
168        return false;
169    }
170
171private:
172
173    typedef std::unordered_map<uint32_t, failure_record_t> FailureRecordMap;
174    typedef std::unordered_map<uint64_t, fast_hash_t> FastHashMap;
175
176    std::unique_ptr<uint8_t[]> key_;
177    FailureRecordMap failure_map_;
178    FastHashMap fast_hash_map_;
179};
180}
181
182#endif // SOFT_GATEKEEPER_H_
183