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 TLOG_TAG "hwrng_fake_srv"
18 
19 #include <stdint.h>
20 #include <stdio.h>
21 #include <stdlib.h>
22 #include <string.h>
23 #include <uapi/err.h>
24 
25 #include <hwcrypto/hwrng_dev.h>
26 #include <trusty/time.h>
27 #include <trusty_log.h>
28 
29 #pragma message "Compiling FAKE HWRNG provider"
30 
hwrng_dev_init(void)31 int hwrng_dev_init(void) {
32     TLOGE("Init FAKE!!!! HWRNG service provider\n");
33     TLOGE("FAKE HWRNG service provider MUST be replaced with the REAL one\n");
34     return NO_ERROR;
35 }
36 
37 static size_t counter = 1;
38 
39 __attribute__((no_sanitize("unsigned-integer-overflow"))) int
trusty_rng_hw_rand(uint8_t * buf,size_t buf_len)40 trusty_rng_hw_rand(uint8_t* buf, size_t buf_len) {
41     int64_t time;
42     trusty_gettime(0, &time);
43 
44     time = time ^ (time >> 32);
45     time = time ^ (time >> 16);
46     const uint8_t mask = (time ^ (time >> 8)) & 0xff;
47 
48     for (uint8_t* end = buf + buf_len; buf < end; ++buf) {
49         *buf = (counter++ ^ mask) & 0xff;
50     }
51     return NO_ERROR;
52 }
53