linux/arch/s390/crypto/prng.c
Heiko Carstens a53c8fab3f s390/comments: unify copyright messages and remove file names
Remove the file name from the comment at top of many files. In most
cases the file name was wrong anyway, so it's rather pointless.

Also unify the IBM copyright statement. We did have a lot of sightly
different statements and wanted to change them one after another
whenever a file gets touched. However that never happened. Instead
people start to take the old/"wrong" statements to use as a template
for new files.
So unify all of them in one go.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-07-20 11:15:04 +02:00

212 lines
4.8 KiB
C

/*
* 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);