From: Jan Glauber <jglauber@redhat.com>
Subject: [RHEL5.1 PATCH] s390: pseudo random number generator
Date: Fri, 02 Mar 2007 10:11:52 +0100
Bugzilla: 184809
Message-Id: <1172826712.5527.3.camel@localhost.localdomain>
Changelog: [s390] pseudo random number generator


BZ 184809

Add support for the z9 CPU pseudo random number generator.

The generator creates random numbers by an algorithm similar to 
the ANSI X9.17 standard. The pseudo-random numbers can be
accessed via a character device driver node called /dev/prandom.
Similar to /dev/urandom any amount of bytes can be read from the
device without blocking.

The PRNG is faster than /dev/urandom by ~ factor 4.

Patch is upstream in 2.6.21-rc1 and tested by IBM.

Needs CONFIG_S390_PRNG=m.

Jan

jglauber@redhat.com
jang@de.ibm.com


 arch/s390/crypto/Makefile     |    1 
 arch/s390/crypto/crypt_s390.h |    1 
 arch/s390/crypto/prng.c       |  213 ++++++++++++++++++++++++++++++++++++++++++
 crypto/Kconfig                |   11 ++
 4 files changed, 226 insertions(+)

diff -urNp linux-2.6.18.s390/arch/s390/crypto/crypt_s390.h linux-2.6.18.s390_prng/arch/s390/crypto/crypt_s390.h
--- linux-2.6.18.s390/arch/s390/crypto/crypt_s390.h	2006-09-20 05:42:06.000000000 +0200
+++ linux-2.6.18.s390_prng/arch/s390/crypto/crypt_s390.h	2007-02-22 15:24:01.000000000 +0100
@@ -65,6 +65,7 @@ enum crypt_s390_kmc_func {
 	KMC_AES_192_DECRYPT  = CRYPT_S390_KMC | 0x13 | 0x80,
 	KMC_AES_256_ENCRYPT  = CRYPT_S390_KMC | 0x14,
 	KMC_AES_256_DECRYPT  = CRYPT_S390_KMC | 0x14 | 0x80,
+	KMC_PRNG             = CRYPT_S390_KMC | 0x43,
 };
 
 /* function codes for KIMD (COMPUTE INTERMEDIATE MESSAGE DIGEST)
diff -urNp linux-2.6.18.s390/arch/s390/crypto/Makefile linux-2.6.18.s390_prng/arch/s390/crypto/Makefile
--- linux-2.6.18.s390/arch/s390/crypto/Makefile	2006-09-20 05:42:06.000000000 +0200
+++ linux-2.6.18.s390_prng/arch/s390/crypto/Makefile	2007-02-22 15:23:33.000000000 +0100
@@ -6,5 +6,6 @@ obj-$(CONFIG_CRYPTO_SHA1_S390) += sha1_s
 obj-$(CONFIG_CRYPTO_SHA256_S390) += sha256_s390.o
 obj-$(CONFIG_CRYPTO_DES_S390) += des_s390.o des_check_key.o
 obj-$(CONFIG_CRYPTO_AES_S390) += aes_s390.o
+obj-$(CONFIG_S390_PRNG) += prng.o
 
 obj-$(CONFIG_CRYPTO_TEST) += crypt_s390_query.o
diff -urNp linux-2.6.18.s390/arch/s390/crypto/prng.c linux-2.6.18.s390_prng/arch/s390/crypto/prng.c
--- linux-2.6.18.s390/arch/s390/crypto/prng.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.18.s390_prng/arch/s390/crypto/prng.c	2007-02-22 15:05:15.000000000 +0100
@@ -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);
diff -urNp linux-2.6.18.s390/crypto/Kconfig linux-2.6.18.s390_prng/crypto/Kconfig
--- linux-2.6.18.s390/crypto/Kconfig	2007-02-22 14:49:00.000000000 +0100
+++ linux-2.6.18.s390_prng/crypto/Kconfig	2007-02-22 15:29:17.000000000 +0100
@@ -360,6 +360,17 @@ config CRYPTO_MPILIB
 	help
 	  Multiprecision maths library from GnuPG
 
+config S390_PRNG
+        tristate "Pseudo random number generator device driver"
+        depends on S390
+        default "m"
+        help
+          Select this option if you want to use the s390 pseudo random number
+          generator. The PRNG is part of the cryptograhic processor functions
+          and uses triple-DES to generate secure random numbers like the
+          ANSI X9.17 standard. The PRNG is usable via the char device
+          /dev/prandom.
+
 source "drivers/crypto/Kconfig"
 endmenu