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 000000000000..8eb3a1aedc22
--- /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);