diff options
Diffstat (limited to 'arch/s390/crypto/prng.c')
| -rw-r--r-- | arch/s390/crypto/prng.c | 213 |
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 00000000000..8eb3a1aedc2 --- /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); |