// SPDX-License-Identifier: GPL-2.0
/*
* chaoskey - driver for ChaosKey device from Altus Metrum.
*
* This device provides true random numbers using a noise source based
* on a reverse-biased p-n junction in avalanche breakdown. More
* details can be found at http://chaoskey.org
*
* The driver connects to the kernel hardware RNG interface to provide
* entropy for /dev/random and other kernel activities. It also offers
* a separate /dev/ entry to allow for direct access to the random
* bit stream.
*
* Copyright © 2015 Keith Packard <[email protected]>
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/wait.h>
#include <linux/hw_random.h>
#include <linux/mutex.h>
#include <linux/uaccess.h>
static struct usb_driver chaoskey_driver;
static struct usb_class_driver chaoskey_class;
static int chaoskey_rng_read(struct hwrng *rng, void *data,
size_t max, bool wait);
#define usb_dbg(usb_if, format, arg...) \
dev_dbg(&(usb_if)->dev, format, ## arg)
#define usb_err(usb_if, format, arg...) \
dev_err(&(usb_if)->dev, format, ## arg)
/* Version Information */
#define DRIVER_AUTHOR "Keith Packard, [email protected]"
#define DRIVER_DESC "Altus Metrum ChaosKey driver"
#define DRIVER_SHORT "chaoskey"
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");
#define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */
#define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */
#define ALEA_VENDOR_ID 0x12d8 /* Araneus */
#define ALEA_PRODUCT_ID 0x0001 /* Alea I */
#define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */
#define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */
#define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */
#ifdef CONFIG_USB_DYNAMIC_MINORS
#define USB_CHAOSKEY_MINOR_BASE 0
#else
/* IOWARRIOR_MINOR_BASE + 16, not official yet */
#define USB_CHAOSKEY_MINOR_BASE 224
#endif
static const struct usb_device_id chaoskey_table[] = {
{ USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) },
{ USB_DEVICE(ALEA_VENDOR_ID, ALEA_PRODUCT_ID) },
{ },
};
MODULE_DEVICE_TABLE(usb, chaoskey_table);
static void chaos_read_callback(struct urb *urb);
/* Driver-local specific stuff */
struct chaoskey {
struct usb_interface *interface;
char in_ep;
struct mutex lock;
struct mutex rng_lock;
int open; /* open count */
bool present; /* device not disconnected */
bool reading; /* ongoing IO */
bool reads_started; /* track first read for Alea */
int size; /* size of buf */
int valid; /* bytes of buf read */
int used; /* bytes of buf consumed */
char *name; /* product + serial */
struct hwrng hwrng; /* Embedded struct for hwrng */
int hwrng_registered; /* registered with hwrng API */
wait_queue_head_t wait_q; /* for timeouts */
struct urb *urb; /* for performing IO */
char *buf;
};
static void chaoskey_free(struct chaoskey *dev)
{
if (dev) {
usb_dbg(dev->interface, "free");
usb_free_urb(dev->urb);
kfree(dev->name);
kfree(dev->buf);
usb_put_intf(dev->interface);
kfree(dev);
}
}
static int chaoskey_probe(struct usb_interface *interface,
const struct usb_device_id *id)
{
struct usb_device *udev = interface_to_usbdev(interface);
struct usb_host_interface *altsetting = interface->cur_altsetting;
struct usb_endpoint_descriptor *epd;
int in_ep;
struct chaoskey *dev;
int result = -ENOMEM;
int size;
int res;
usb_dbg(interface, "probe %s-%s", udev->product, udev->serial);
/* Find the first bulk IN endpoint and its packet size */
res = usb_find_bulk_in_endpoint(altsetting, &epd);
if (res) {
usb_dbg(interface, "no IN endpoint found");
return res;
}
in_ep = usb_endpoint_num(epd);
size = usb_endpoint_maxp(epd);
/* Validate endpoint and size */
if (size <= 0) {
usb_dbg(interface, "invalid size (%d)", size);
return -ENODEV;
}
if (size > CHAOSKEY_BUF_LEN) {
usb_dbg(interface, "size reduced from %d to %d\n",
size, CHAOSKEY_BUF_LEN);
size = CHAOSKEY_BUF_LEN;
}
/* Looks good, allocate and initialize */
dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL);
if (dev == NULL)
goto out;
dev->interface = usb_get_intf(interface);
dev->buf = kmalloc(size, GFP_KERNEL);
if (dev->buf == NULL)
goto out;
dev->urb = usb_alloc_urb(0, GFP_KERNEL);
if (!dev->urb)
goto out;
usb_fill_bulk_urb(dev->urb,
udev,
usb_rcvbulkpipe(udev, in_ep),
dev->buf,
size,
chaos_read_callback,
dev);
/* Construct a name using the product and serial values. Each
* device needs a unique name for the hwrng code
*/
if (udev->product && udev->serial) {
dev->name = kasprintf(GFP_KERNEL, "%s-%s", udev->product,
udev->serial);
if (dev->name == NULL)
goto out;
}
dev->in_ep = in_ep;
if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID)
dev->reads_started = true;
dev->size = size;
dev->present = true;
init_waitqueue_head(&dev->wait_q);
mutex_init(&dev->lock);
mutex_init(&dev->rng_lock);
usb_set_intfdata(interface, dev);
result = usb_register_dev(interface, &chaoskey_class);
if (result) {
usb_err(interface, "Unable to allocate minor number.");
goto out;
}
dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
dev->hwrng.read = chaoskey_rng_read;
dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
if (!dev->hwrng_registered)
usb_err(interface, "Unable to register with hwrng");
usb_enable_autosuspend(udev);
usb_dbg(interface, "chaoskey probe success, size %d", dev->size);
return 0;
out:
usb_set_intfdata(interface, NULL);
chaoskey_free(dev);
return result;
}
static void chaoskey_disconnect(struct usb_interface *interface)
{
struct chaoskey *dev;
usb_dbg(interface, "disconnect");
dev = usb_get_intfdata(interface);
if (!dev) {
usb_dbg(interface, "disconnect failed - no dev");
return;
}
if (dev->hwrng_registered)
hwrng_unregister(&dev->hwrng);
usb_deregister_dev(interface, &chaoskey_class);
usb_set_intfdata(interface, NULL);
mutex_lock(&dev->lock);
dev->present = false;
usb_poison_urb(dev->urb);
if (!dev->open) {
mutex_unlock(&dev->lock);
chaoskey_free(dev);
} else
mutex_unlock(&dev->lock);
usb_dbg(interface, "disconnect done");
}
static int chaoskey_open(struct inode *inode, struct file *file)
{
struct chaoskey *dev;
struct usb_interface *interface;
/* get the interface from minor number and driver information */
interface = usb_find_interface(&chaoskey_driver, iminor(inode));
if (!interface)
return -ENODEV;
usb_dbg(interface, "open");
dev = usb_get_intfdata(interface);
if (!dev) {
usb_dbg(interface, "open (dev)");
return -ENODEV;
}
file->private_data = dev;
mutex_lock(&dev->lock);
++dev->open;
mutex_unlock(&dev->lock);
usb_dbg(interface, "open success");
return 0;
}
static int chaoskey_release(struct inode *inode, struct file *file)
{
struct chaoskey *dev = file->private_data;
struct usb_interface *interface;
if (dev == NULL)
return -ENODEV;
interface = dev->interface;
usb_dbg(interface, "release");
mutex_lock(&dev->lock);
usb_dbg(interface, "open count at release is %d", dev->open);
if (dev->open <= 0) {
usb_dbg(interface, "invalid open count (%d)", dev->open);
mutex_unlock(&dev->lock);
return -ENODEV;
}
--dev->open;
if (!dev->present) {
if (dev->open == 0) {
mutex_unlock(&dev->lock);
chaoskey_free(dev);
} else
mutex_unlock(&dev->lock);
} else
mutex_unlock(&dev->lock);
usb_dbg(interface, "release success");
return 0;
}
static void chaos_read_callback(struct urb *urb)
{
struct chaoskey *dev = urb->context;
int status = urb->status;
usb_dbg(dev->interface, "callback status (%d)", status);
if (status == 0)
dev->valid = urb->actual_length;
else
dev->valid = 0;
dev->used = 0;
/* must be seen first before validity is announced */
smp_wmb();
dev->reading = false;
wake_up(&dev->wait_q);
}
/* Fill the buffer. Called with dev->lock held
*/
static int _chaoskey_fill(struct chaoskey *dev)
{
DEFINE_WAIT(wait);
int result;
bool started;
usb_dbg(dev->interface, "fill");
/* Return immediately if someone called before the buffer was
* empty */
if (dev->valid != dev->used) {
usb_dbg(dev->interface, "not empty yet (valid %d used %d)",
dev->valid, dev->used);
return 0;
}
/* Bail if the device has been removed */
if (!dev->present) {
usb_dbg(dev->interface, "device not present");
return -ENODEV;
}
/* Make sure the device is awake */
result = usb_autopm_get_interface(dev->interface);
if (result) {
usb_dbg(dev->interface, "wakeup failed (result %d)", result);
return result;
}
dev->reading = true;
result = usb_submit_urb(dev->urb, GFP_KERNEL);
if (result < 0) {
result = usb_translate_errors(result);
dev->reading = false;
goto out;
}
/* The first read on the Alea takes a little under 2 seconds.
* Reads after the first read take only a few microseconds
* though. Presumably the entropy-generating circuit needs
* time to ramp up. So, we wait longer on the first read.
*/
started = dev->reads_started;
dev->reads_started = true;
result = wait_event_interruptible_timeout(
dev->wait_q,
!dev->reading,
(started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) );
if (result < 0) {
usb_kill_urb(dev->urb);
goto out;
}
if (result == 0) {
result = -ETIMEDOUT;
usb_kill_urb(dev->urb);
} else {
result = dev->valid;
}
out:
/* Let the device go back to sleep eventually */
usb_autopm_put_interface(dev->interface);
usb_dbg(dev->interface, "read %d bytes", dev->valid);
return result;
}
static ssize_t chaoskey_read(struct file *file,
char __user *buffer,
size_t count,
loff_t *ppos)
{
struct chaoskey *dev;
ssize_t read_count = 0;
int this_time;
int result = 0;
unsigned long remain;
dev = file->private_data;
if (dev == NULL || !dev->present)
return -ENODEV;
usb_dbg(dev->interface, "read %zu", count);
while (count > 0) {
/* Grab the rng_lock briefly to ensure that the hwrng interface
* gets priority over other user access
*/
result = mutex_lock_interruptible(&dev->rng_lock);
if (result)
goto bail;
mutex_unlock(&dev->rng_lock);
result = mutex_lock_interruptible(&dev->lock);
if (result)
goto bail;
if (dev->valid == dev->used) {
result = _chaoskey_fill(dev);
if (result < 0) {
mutex_unlock(&dev->lock);
goto bail;
}
}
this_time = dev->valid - dev->used;
if (this_time > count)
this_time = count;
remain = copy_to_user(buffer, dev->buf + dev->used, this_time);
if (remain) {
result = -EFAULT;
/* Consume the bytes that were copied so we don't leak
* data to user space
*/
dev->used += this_time - remain;
mutex_unlock(&dev->lock);
goto bail;
}
count -= this_time;
read_count += this_time;
buffer += this_time;
dev->used += this_time;
mutex_unlock(&dev->lock);
}
bail:
if (read_count) {
usb_dbg(dev->interface, "read %zu bytes", read_count);
return read_count;
}
usb_dbg(dev->interface, "empty read, result %d", result);
if (result == -ETIMEDOUT)
result = -EAGAIN;
return result;
}
static int chaoskey_rng_read(struct hwrng *rng, void *data,
size_t max, bool wait)
{
struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
int this_time;
usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait);
if (!dev->present) {
usb_dbg(dev->interface, "device not present");
return 0;
}
/* Hold the rng_lock until we acquire the device lock so that
* this operation gets priority over other user access to the
* device
*/
mutex_lock(&dev->rng_lock);
mutex_lock(&dev->lock);
mutex_unlock(&dev->rng_lock);
/* Try to fill the buffer if empty. It doesn't actually matter
* if _chaoskey_fill works; we'll just return zero bytes as
* the buffer will still be empty
*/
if (dev->valid == dev->used)
(void) _chaoskey_fill(dev);
this_time = dev->valid - dev->used;
if (this_time > max)
this_time = max;
memcpy(data, dev->buf + dev->used, this_time);
dev->used += this_time;
mutex_unlock(&dev->lock);
usb_dbg(dev->interface, "rng_read this_time %d\n", this_time);
return this_time;
}
#ifdef CONFIG_PM
static int chaoskey_suspend(struct usb_interface *interface,
pm_message_t message)
{
usb_dbg(interface, "suspend");
return 0;
}
static int chaoskey_resume(struct usb_interface *interface)
{
struct chaoskey *dev;
struct usb_device *udev = interface_to_usbdev(interface);
usb_dbg(interface, "resume");
dev = usb_get_intfdata(interface);
/*
* We may have lost power.
* In that case the device that needs a long time
* for the first requests needs an extended timeout
* again
*/
if (le16_to_cpu(udev->descriptor.idVendor) == ALEA_VENDOR_ID)
dev->reads_started = false;
return 0;
}
#else
#define chaoskey_suspend NULL
#define chaoskey_resume NULL
#endif
/* file operation pointers */
static const struct file_operations chaoskey_fops = {
.owner = THIS_MODULE,
.read = chaoskey_read,
.open = chaoskey_open,
.release = chaoskey_release,
.llseek = default_llseek,
};
/* class driver information */
static struct usb_class_driver chaoskey_class = {
.name = "chaoskey%d",
.fops = &chaoskey_fops,
.minor_base = USB_CHAOSKEY_MINOR_BASE,
};
/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver chaoskey_driver = {
.name = DRIVER_SHORT,
.probe = chaoskey_probe,
.disconnect = chaoskey_disconnect,
.suspend = chaoskey_suspend,
.resume = chaoskey_resume,
.reset_resume = chaoskey_resume,
.id_table = chaoskey_table,
.supports_autosuspend = 1,
};
module_usb_driver(chaoskey_driver);
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