How to use get_random_bytes() in linux kernel module?

by viola_gleichner , in category: General Help , 7 months ago

How to use get_random_bytes() in linux kernel module?

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2 answers

by noemy.bosco , 6 months ago

@viola_gleichner 

To use the get_random_bytes() function in a Linux kernel module, you need to follow these steps:

  1. Include the necessary header file: Include the linux/random.h header file in your module source code to be able to use the get_random_bytes() function.
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#include <linux/random.h>


  1. Declare a buffer: Declare a buffer of the required size to hold the random bytes you want to generate.
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#define BUF_SIZE 16
unsigned char buf[BUF_SIZE];


  1. Generate random bytes: Use the get_random_bytes() function to generate random bytes into the declared buffer.
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get_random_bytes(buf, BUF_SIZE);


  1. Use the generated random bytes: After calling get_random_bytes(), the buf array will be populated with random bytes. You can then use these bytes as needed in your kernel module.


Here's a simple example showing the usage of get_random_bytes():

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#include <linux/module.h>
#include <linux/random.h>

#define BUF_SIZE 16

unsigned char buf[BUF_SIZE];

static int __init my_init(void) {
    printk(KERN_INFO "Generating random bytes
");
    get_random_bytes(buf, BUF_SIZE);

    // Use the generated random bytes as needed

    return 0;
}

static void __exit my_exit(void) {
    // Cleanup if required
}

module_init(my_init);
module_exit(my_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Random Bytes Example");


Make sure to compile and install the kernel module using the appropriate build system (e.g., make or kbuild) for your specific kernel version.

Member

by adolf , 2 months ago

@viola_gleichner 

In the above example code snippet:

  • The header files linux/module.h and linux/random.h are included.
  • A buffer buf of size BUF_SIZE (16 in this case) is declared to store the generated random bytes.
  • The my_init() function calls get_random_bytes() to fill the buf with random bytes.
  • The generated random bytes can be used as required within the module.
  • The module_init() and module_exit() macros are used to specify the initialization and cleanup functions.
  • The module information like license and description is provided using appropriate macros.


Remember to compile the kernel module and load it into the kernel to test the functionality. Additionally, keep in mind that generating random bytes in the kernel context should be done cautiously, especially if the randomness is used for cryptographic purposes.