Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 ========================================================== 2 Linux support for random number generator in i8xx chipsets 3 ========================================================== 4 5 Introduction 6 ============ 7 8 The hw_random framework is software that makes use of a 9 special hardware feature on your CPU or motherboard, 10 a Random Number Generator (RNG). The software has two parts: 11 a core providing the /dev/hwrng character device and its 12 sysfs support, plus a hardware-specific driver that plugs 13 into that core. 14 15 To make the most effective use of these mechanisms, you 16 should download the support software as well. Download the 17 latest version of the "rng-tools" package from the 18 hw_random driver's official Web site: 19 20 http://sourceforge.net/projects/gkernel/ 21 22 Those tools use /dev/hwrng to fill the kernel entropy pool, 23 which is used internally and exported by the /dev/urandom and 24 /dev/random special files. 25 26 Theory of operation 27 =================== 28 29 CHARACTER DEVICE. Using the standard open() 30 and read() system calls, you can read random data from 31 the hardware RNG device. This data is NOT CHECKED by any 32 fitness tests, and could potentially be bogus (if the 33 hardware is faulty or has been tampered with). Data is only 34 output if the hardware "has-data" flag is set, but nevertheless 35 a security-conscious person would run fitness tests on the 36 data before assuming it is truly random. 37 38 The rng-tools package uses such tests in "rngd", and lets you 39 run them by hand with a "rngtest" utility. 40 41 /dev/hwrng is char device major 10, minor 183. 42 43 CLASS DEVICE. There is a /sys/class/misc/hw_random node with 44 two unique attributes, "rng_available" and "rng_current". The 45 "rng_available" attribute lists the hardware-specific drivers 46 available, while "rng_current" lists the one which is currently 47 connected to /dev/hwrng. If your system has more than one 48 RNG available, you may change the one used by writing a name from 49 the list in "rng_available" into "rng_current". 50 51 ========================================================================== 52 53 54 Hardware driver for Intel/AMD/VIA Random Number Generators (RNG) 55 - Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com> 56 - Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com> 57 58 59 About the Intel RNG hardware, from the firmware hub datasheet 60 ============================================================= 61 62 The Firmware Hub integrates a Random Number Generator (RNG) 63 using thermal noise generated from inherently random quantum 64 mechanical properties of silicon. When not generating new random 65 bits the RNG circuitry will enter a low power state. Intel will 66 provide a binary software driver to give third party software 67 access to our RNG for use as a security feature. At this time, 68 the RNG is only to be used with a system in an OS-present state. 69 70 Intel RNG Driver notes 71 ====================== 72 73 FIXME: support poll(2) 74 75 .. note:: 76 77 request_mem_region was removed, for three reasons: 78 79 1) Only one RNG is supported by this driver; 80 2) The location used by the RNG is a fixed location in 81 MMIO-addressable memory; 82 3) users with properly working BIOS e820 handling will always 83 have the region in which the RNG is located reserved, so 84 request_mem_region calls always fail for proper setups. 85 However, for people who use mem=XX, BIOS e820 information is 86 **not** in /proc/iomem, and request_mem_region(RNG_ADDR) can 87 succeed. 88 89 Driver details 90 ============== 91 92 Based on: 93 Intel 82802AB/82802AC Firmware Hub (FWH) Datasheet 94 May 1999 Order Number: 290658-002 R 95 96 Intel 82802 Firmware Hub: 97 Random Number Generator 98 Programmer's Reference Manual 99 December 1999 Order Number: 298029-001 R 100 101 Intel 82802 Firmware HUB Random Number Generator Driver 102 Copyright (c) 2000 Matt Sottek <msottek@quiknet.com> 103 104 Special thanks to Matt Sottek. I did the "guts", he 105 did the "brains" and all the testing.