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Updated with kernel thread to add randmoness

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This commit is contained in:
Mickey Malone
2021-02-13 09:05:10 -06:00
parent 5571c8809c
commit edc12a7988
2 changed files with 101 additions and 15 deletions
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113
driver/pico_rng.c
View File

@@ -10,6 +10,8 @@
#include <linux/kernel.h>
#include <linux/semaphore.h>
#include <asm/uaccess.h>
#include <linux/hw_random.h>
#include <linux/kthread.h>
MODULE_LICENSE("GPL");
@@ -18,13 +20,14 @@ MODULE_DESCRIPTION("Random number generator using a Raspberry Pi Pico");
MODULE_VERSION("1.0");
/**
* Static constants
* Macros
**/
#define VENDOR_ID 0x0
#define PRODUCT_ID 0x4
#define PICO_RNG_ENTROPY(x) (((x) * 8 * 10) >> 5) /* quality: 10/32 */
/**
* Helper macros
* Logger macros
**/
#define LOGGER_INFO(fmt, args ...) printk( KERN_INFO "[info] %s(%d): " fmt, __FUNCTION__, __LINE__, ## args)
#define LOGGER_ERR(fmt, args ...) printk( KERN_ERR "[err] %s(%d): " fmt, __FUNCTION__, __LINE__, ## args)
@@ -46,8 +49,9 @@ struct pico_rng_data {
struct usb_device *dev;
struct usb_interface *interface;
struct usb_endpoint_descriptor *endpoint;
char *buffer;
void *buffer;
int pipe;
struct task_struct *rng_task;
} module_data;
/**
@@ -58,9 +62,15 @@ static void pico_rng_usb_disconnect(struct usb_interface *interface);
static int __init pico_rng_driver_init(void);
static void __exit pico_rng_driver_exit(void);
static int pico_rng_read_data(void);
static ssize_t pico_rng_read(struct file *file, char __user *user_buffer, size_t size, loff_t *offset);
static int pico_rng_open(struct inode *inode, struct file *file);
static int pico_rng_kthread(void *data);
void pico_rng_kthread_start(void);
void pico_rng_kthread_stop(void);
/**
* Data structure of the USB vid:pid device that we will support
**/
@@ -93,7 +103,7 @@ static struct file_operations pico_rng_fops = {
* USB class data structure
**/
struct usb_class_driver pico_rng_usb_class = {
.name = "pico_rng",
.name = "pico_raw",
.fops = &pico_rng_fops,
};
@@ -107,14 +117,12 @@ static int pico_rng_open(struct inode *inode, struct file *file)
}
/**
* File ops:read
**/
static ssize_t pico_rng_read(struct file *file, char __user *user_buffer, size_t size, loff_t *offset)
* Read data from the pico rng
*/
static int pico_rng_read_data()
{
int retval = 0;
int actual_length = 0;
int retval = 0;
LOGGER_DEBUG("inside pico_rng_read with file %p, user_buffer %p, size %ld, offset %lld\n", file, user_buffer, size, *offset);
// int usb_bulk_msg(struct usb_device *usb_dev, unsigned int pipe, void *data, int len, int *actual_length, int timeout)
LOGGER_DEBUG("Calling usb_bulk_msg dev %p, pipe %d, buffer %p, size %d, and timeout %d", \
@@ -126,19 +134,38 @@ static ssize_t pico_rng_read(struct file *file, char __user *user_buffer, size_t
module_data.endpoint->wMaxPacketSize,
&actual_length,
timeout);
if(retval)
if(retval)
{
return -EFAULT;
}
LOGGER_DEBUG("Copying %d bytest of random data to userspace with offset %lld\n", actual_length, *offset);
if(copy_to_user(user_buffer, module_data.buffer, module_data.endpoint->wMaxPacketSize))
return actual_length;
}
/**
* File ops:read
**/
static ssize_t pico_rng_read(struct file *file, char __user *user_buffer, size_t size, loff_t *offset)
{
int bytes_read = 0;
LOGGER_DEBUG("inside pico_rng_read with file %p, user_buffer %p, size %ld, offset %lld\n", file, user_buffer, size, *offset);
bytes_read = pico_rng_read_data();
if(!bytes_read)
{
LOGGER_ERR("Failed to read data");
return -EFAULT;
}
LOGGER_DEBUG("Copying %d bytest of random data to userspace with offset %lld\n", bytes_read, *offset);
if(copy_to_user(user_buffer, module_data.buffer, bytes_read))
{
return -EFAULT;
}
return module_data.endpoint->wMaxPacketSize;
return bytes_read;
}
/**
@@ -192,6 +219,8 @@ static int pico_rng_usb_probe(struct usb_interface *interface, const struct usb_
// int usb_bulk_msg(struct usb_device *usb_dev, unsigned int pipe, void *data, int len, int *actual_length, int timeout)
//retval = usb_bulk_msg(dev, pipe, buffer, 64, &actual_length, 500);
pico_rng_kthread_start();
return retval;
}
@@ -202,6 +231,7 @@ static int pico_rng_usb_probe(struct usb_interface *interface, const struct usb_
static void pico_rng_usb_disconnect(struct usb_interface *interface)
{
LOGGER_INFO("pico rng usb device disconnected\n");
pico_rng_kthread_stop();
usb_deregister_dev(module_data.interface, &pico_rng_usb_class);
module_data.dev = NULL;
module_data.interface = NULL;
@@ -210,6 +240,59 @@ static void pico_rng_usb_disconnect(struct usb_interface *interface)
module_data.buffer = NULL;
}
/*
* Pico rng thread that periodically adds hardware randomness
*/
static int pico_rng_kthread(void *data)
{
int bytes_read;
while (!kthread_should_stop())
{
bytes_read = pico_rng_read_data();
if(!bytes_read)
{
LOGGER_ERR("Failed to read data\n");
// sleep for at least a second, max 2 seconds
usleep_range(1000000, 2000000);
continue;
}
LOGGER_DEBUG("Adding hardware randomness\n");
add_hwgenerator_randomness(module_data.buffer, bytes_read, PICO_RNG_ENTROPY(bytes_read));
LOGGER_DEBUG("Randomness added\n");
}
return 0;
}
/**
* Start the rng thread
**/
void pico_rng_kthread_start()
{
module_data.rng_task = kthread_run(pico_rng_kthread, &module_data, "pico_rng_thread");
if(IS_ERR(module_data.rng_task))
{
module_data.rng_task = NULL;
LOGGER_ERR("Failed to launch the pico rng task\n");
}
}
/**
* Stop the rng thread
**/
void pico_rng_kthread_stop()
{
if(module_data.rng_task)
{
kthread_stop(module_data.rng_task);
module_data.rng_task = NULL;
}
}
static int __init pico_rng_driver_init(void)
{
int retval = 0;

3
firmware/pico_rng.c
View File

@@ -564,6 +564,9 @@ void get_random_data(char *buf, uint16_t len) {
memcpy(&buf[i-1], (void*)&adc_result, 2);
}
// The pico has a clock, use it as the seed because time always changes
// https://raspberrypi.github.io/pico-sdk-doxygen/group__hardware__clocks.html
/**
* In an attempt to make the rng even more random this will slow down the amount of data the
* pico can generate. It appears to be more random, but not good enough for FIPS 140-2.