1 files changed, 213 insertions, 0 deletions
diff --git a/arch/s390/crypto/prng.c b/arch/s390/crypto/prng.c
new file mode 100644
index 0000000..8eb3a1a
--- /dev/null
+++ b/arch/s390/crypto/prng.c
@@ -0,0 +1,213 @@
+/*
+ * 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);