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
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
|
/*
* Copyright IBM Corp. 2006,2007
* Author(s): Jan Glauber <jan.glauber@de.ibm.com>
* Driver for the s390 pseudo random number generator
*/
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <asm/debug.h>
#include <asm/uaccess.h>
#include "crypt_s390.h"
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jan Glauber <jan.glauber@de.ibm.com>");
MODULE_DESCRIPTION("s390 PRNG interface");
static int prng_chunk_size = 256;
module_param(prng_chunk_size, int, S_IRUSR | S_IRGRP | S_IROTH);
MODULE_PARM_DESC(prng_chunk_size, "PRNG read chunk size in bytes");
static int prng_entropy_limit = 4096;
module_param(prng_entropy_limit, int, S_IRUSR | S_IRGRP | S_IROTH | S_IWUSR);
MODULE_PARM_DESC(prng_entropy_limit,
"PRNG add entropy after that much bytes were produced");
/*
* Any one who considers arithmetical methods of producing random digits is,
* of course, in a state of sin. -- John von Neumann
*/
struct s390_prng_data {
unsigned long count; /* how many bytes were produced */
char *buf;
};
static struct s390_prng_data *p;
/* copied from libica, use a non-zero initial parameter block */
static unsigned char parm_block[32] = {
0x0F,0x2B,0x8E,0x63,0x8C,0x8E,0xD2,0x52,0x64,0xB7,0xA0,0x7B,0x75,0x28,0xB8,0xF4,
0x75,0x5F,0xD2,0xA6,0x8D,0x97,0x11,0xFF,0x49,0xD8,0x23,0xF3,0x7E,0x21,0xEC,0xA0,
};
static int prng_open(struct inode *inode, struct file *file)
{
return nonseekable_open(inode, file);
}
static void prng_add_entropy(void)
{
__u64 entropy[4];
unsigned int i;
int ret;
for (i = 0; i < 16; i++) {
ret = crypt_s390_kmc(KMC_PRNG, parm_block, (char *)entropy,
(char *)entropy, sizeof(entropy));
BUG_ON(ret < 0 || ret != sizeof(entropy));
memcpy(parm_block, entropy, sizeof(entropy));
}
}
static void prng_seed(int nbytes)
{
char buf[16];
int i = 0;
BUG_ON(nbytes > 16);
get_random_bytes(buf, nbytes);
/* Add the entropy */
while (nbytes >= 8) {
*((__u64 *)parm_block) ^= *((__u64 *)(buf+i));
prng_add_entropy();
i += 8;
nbytes -= 8;
}
prng_add_entropy();
}
static ssize_t prng_read(struct file *file, char __user *ubuf, size_t nbytes,
loff_t *ppos)
{
int chunk, n;
int ret = 0;
int tmp;
/* nbytes can be arbitrary length, we split it into chunks */
while (nbytes) {
/* same as in extract_entropy_user in random.c */
if (need_resched()) {
if (signal_pending(current)) {
if (ret == 0)
ret = -ERESTARTSYS;
break;
}
schedule();
}
/*
* we lose some random bytes if an attacker issues
* reads < 8 bytes, but we don't care
*/
chunk = min_t(int, nbytes, prng_chunk_size);
/* PRNG only likes multiples of 8 bytes */
n = (chunk + 7) & -8;
if (p->count > prng_entropy_limit)
prng_seed(8);
/* if the CPU supports PRNG stckf is present too */
asm volatile(".insn s,0xb27c0000,%0"
: "=m" (*((unsigned long long *)p->buf)) : : "cc");
/*
* Beside the STCKF the input for the TDES-EDE is the output
* of the last operation. We differ here from X9.17 since we
* only store one timestamp into the buffer. Padding the whole
* buffer with timestamps does not improve security, since
* successive stckf have nearly constant offsets.
* If an attacker knows the first timestamp it would be
* trivial to guess the additional values. One timestamp
* is therefore enough and still guarantees unique input values.
*
* Note: you can still get strict X9.17 conformity by setting
* prng_chunk_size to 8 bytes.
*/
tmp = crypt_s390_kmc(KMC_PRNG, parm_block, p->buf, p->buf, n);
BUG_ON((tmp < 0) || (tmp != n));
p->count += n;
if (copy_to_user(ubuf, p->buf, chunk))
return -EFAULT;
nbytes -= chunk;
ret += chunk;
ubuf += chunk;
}
return ret;
}
static const struct file_operations prng_fops = {
.owner = THIS_MODULE,
.open = &prng_open,
.release = NULL,
.read = &prng_read,
.llseek = noop_llseek,
};
static struct miscdevice prng_dev = {
.name = "prandom",
.minor = MISC_DYNAMIC_MINOR,
.fops = &prng_fops,
};
static int __init prng_init(void)
{
int ret;
/* check if the CPU has a PRNG */
if (!crypt_s390_func_available(KMC_PRNG, CRYPT_S390_MSA))
return -EOPNOTSUPP;
if (prng_chunk_size < 8)
return -EINVAL;
p = kmalloc(sizeof(struct s390_prng_data), GFP_KERNEL);
if (!p)
return -ENOMEM;
p->count = 0;
p->buf = kmalloc(prng_chunk_size, GFP_KERNEL);
if (!p->buf) {
ret = -ENOMEM;
goto out_free;
}
/* initialize the PRNG, add 128 bits of entropy */
prng_seed(16);
ret = misc_register(&prng_dev);
if (ret)
goto out_buf;
return 0;
out_buf:
kfree(p->buf);
out_free:
kfree(p);
return ret;
}
static void __exit prng_exit(void)
{
/* wipe me */
kzfree(p->buf);
kfree(p);
misc_deregister(&prng_dev);
}
module_init(prng_init);
module_exit(prng_exit);
|
