diff options
Diffstat (limited to 'drivers/usb/misc/chaoskey.c')
| -rw-r--r-- | drivers/usb/misc/chaoskey.c | 584 |
1 files changed, 584 insertions, 0 deletions
diff --git a/drivers/usb/misc/chaoskey.c b/drivers/usb/misc/chaoskey.c new file mode 100644 index 000000000..87067c3d6 --- /dev/null +++ b/drivers/usb/misc/chaoskey.c @@ -0,0 +1,584 @@ +// 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 <keithp@keithp.com> + */ + +#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, keithp@keithp.com" +#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.quality = 1024; + + 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); + |