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