--- /dev/null
+/*
+ * 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 <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*8);
+ 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 long, we spilt 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 struct file_operations prng_fops = {
+ .owner = THIS_MODULE,
+ .open = &prng_open,
+ .release = NULL,
+ .read = &prng_read,
+};
+
+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))
+ 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) {
+ printk(KERN_WARNING
+ "Could not register misc device for PRNG.\n");
+ goto out_buf;
+ }
+ return 0;
+
+out_buf:
+ kfree(p->buf);
+out_free:
+ kfree(p);
+ return ret;
+}
+
+static void __exit prng_exit(void)
+{
+ /* wipe me */
+ memset(p->buf, 0, prng_chunk_size);
+ kfree(p->buf);
+ kfree(p);
+
+ misc_deregister(&prng_dev);
+}
+
+module_init(prng_init);
+module_exit(prng_exit);
projects / linux-2.6 / commitdiff