1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
|
/*
* /dev/random EntropySource
* (C) 1999-2009 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/internal/dev_random.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
namespace Botan {
/**
Close the device, if open
*/
void Device_EntropySource::Device_Reader::close()
{
if(fd > 0) { ::close(fd); fd = -1; }
}
/**
Read bytes from a device file
*/
size_t Device_EntropySource::Device_Reader::get(byte out[], size_t length,
size_t ms_wait_time)
{
if(fd < 0)
return 0;
if(fd >= FD_SETSIZE)
return 0;
fd_set read_set;
FD_ZERO(&read_set);
FD_SET(fd, &read_set);
struct ::timeval timeout;
timeout.tv_sec = (ms_wait_time / 1000);
timeout.tv_usec = (ms_wait_time % 1000) * 1000;
if(::select(fd + 1, &read_set, nullptr, nullptr, &timeout) < 0)
return 0;
if(!(FD_ISSET(fd, &read_set)))
return 0;
const ssize_t got = ::read(fd, out, length);
if(got <= 0)
return 0;
return static_cast<size_t>(got);
}
/**
Attempt to open a device
*/
Device_EntropySource::Device_Reader::fd_type
Device_EntropySource::Device_Reader::open(const std::string& pathname)
{
#ifndef O_NONBLOCK
#define O_NONBLOCK 0
#endif
#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif
const int flags = O_RDONLY | O_NONBLOCK | O_NOCTTY;
return ::open(pathname.c_str(), flags);
}
/**
Device_EntropySource constructor
Open a file descriptor to each (available) device in fsnames
*/
Device_EntropySource::Device_EntropySource(
const std::vector<std::string>& fsnames)
{
for(size_t i = 0; i != fsnames.size(); ++i)
{
Device_Reader::fd_type fd = Device_Reader::open(fsnames[i]);
if(fd > 0)
devices.push_back(Device_Reader(fd));
}
}
/**
Device_EntropySource destructor: close all open devices
*/
Device_EntropySource::~Device_EntropySource()
{
for(size_t i = 0; i != devices.size(); ++i)
devices[i].close();
}
/**
* Gather entropy from a RNG device
*/
void Device_EntropySource::poll(Entropy_Accumulator& accum)
{
const size_t ENTROPY_BITS_PER_BYTE = 7;
const size_t go_get = std::min<size_t>(
accum.desired_remaining_bits() / ENTROPY_BITS_PER_BYTE, 32);
const size_t read_wait_ms = std::max<size_t>(go_get, 100);
secure_vector<byte>& io_buffer = accum.get_io_buffer(go_get);
for(size_t i = 0; i != devices.size(); ++i)
{
size_t got = devices[i].get(&io_buffer[0], io_buffer.size(),
read_wait_ms);
if(got)
{
accum.add(&io_buffer[0], got, ENTROPY_BITS_PER_BYTE);
break;
}
}
}
}
|
