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      1 /*	$NetBSD: efirng.c,v 1.4 2022/08/14 11:26:41 jmcneill Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2020 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 /*
     30  * UEFI Forum, Inc.: UEFI Specification, Version 2.8 Errata A, February
     31  * 2020, Sec. 37.5 EFI Random Number Generator Protocol, pp. 2158--2162
     32  * https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_A_Feb14.pdf
     33  */
     34 
     35 #include "efirng.h"
     36 
     37 #include "efiboot.h"
     38 
     39 static EFI_GUID RngProtocolGuid = EFI_RNG_PROTOCOL_GUID;
     40 static EFI_GUID RngAlgorithmRawGuid = EFI_RNG_ALGORITHM_RAW;
     41 static EFI_RNG_PROTOCOL *rng;
     42 
     43 #ifndef EFIBOOT_DEBUG
     44 #define	DPRINT(...)	__nothing
     45 #else
     46 #define	DPRINT		Print
     47 #endif
     48 
     49 static const struct {
     50 	EFI_GUID guid;
     51 	const CHAR16 *name;
     52 } algname[] = {
     53 	{EFI_RNG_ALGORITHM_SP800_90_HASH_256_GUID,
     54 	 L"NIST SP800-90 Hash_DRBG SHA-256"},
     55 	{EFI_RNG_ALGORITHM_SP800_90_HMAC_256_GUID,
     56 	 L"NIST SP800-90 HMAC_DRBG SHA-256"},
     57 	{EFI_RNG_ALGORITHM_SP800_90_CTR_256_GUID,
     58 	 L"NIST SP800-90 CTR_DRBG AES-256"},
     59 	{EFI_RNG_ALGORITHM_X9_31_3DES_GUID, L"ANSI X9.31 3DES"},
     60 	{EFI_RNG_ALGORITHM_X9_31_AES_GUID, L"ANSI X9.31 AES"},
     61 	{EFI_RNG_ALGORITHM_RAW, L"raw"},
     62 };
     63 
     64 void
     65 efi_rng_probe(void)
     66 {
     67 	EFI_STATUS status;
     68 
     69 	/* Get the RNG protocol.  */
     70 	status = LibLocateProtocol(&RngProtocolGuid, (void **)&rng);
     71 	if (EFI_ERROR(status)) {
     72 		DPRINT(L"efirng: protocol: %r\n", status);
     73 		rng = NULL;
     74 		return;
     75 	}
     76 }
     77 
     78 void
     79 efi_rng_show(void)
     80 {
     81 	EFI_RNG_ALGORITHM alglist[10];
     82 	UINTN i, j, alglistsz = sizeof(alglist);
     83 	EFI_STATUS status;
     84 
     85 	if (!efi_rng_available())
     86 		return;
     87 
     88 	command_printtab("RNG", "");
     89 
     90 	/* Query the list of supported algorithms.  */
     91 	status = uefi_call_wrapper(rng->GetInfo, 3, rng, &alglistsz, alglist);
     92 	if (EFI_ERROR(status)) {
     93 		Print(L"GetInfo: %r\n", status);
     94 		return;
     95 	}
     96 
     97 	/* Print the list of supported algorithms.  */
     98 	for (i = 0; i < alglistsz/sizeof(alglist[0]); i++) {
     99 		const CHAR16 *name = L"[unknown]";
    100 		for (j = 0; j < __arraycount(algname); j++) {
    101 			if (memcmp(&alglist[i], &algname[j].guid,
    102 				sizeof(EFI_GUID)) == 0) {
    103 				name = algname[j].name;
    104 				break;
    105 			}
    106 		}
    107 		Print(L"%s (%g)\n", name, &alglist[i]);
    108 	}
    109 }
    110 
    111 int
    112 efi_rng_available(void)
    113 {
    114 
    115 	return rng != NULL;
    116 }
    117 
    118 int
    119 efi_rng(void *buf, UINTN len)
    120 {
    121 	EFI_STATUS status;
    122 
    123 	if (!efi_rng_available())
    124 		return EIO;
    125 
    126 	status = uefi_call_wrapper(rng->GetRNG, 4, rng, &RngAlgorithmRawGuid,
    127 	    len, buf);
    128 	if (status == EFI_UNSUPPORTED) {
    129 		/*
    130 		 * Fall back to any supported RNG `algorithm' even
    131 		 * though we would prefer raw samples.
    132 		 */
    133 		status = uefi_call_wrapper(rng->GetRNG, 4, rng, NULL, len, buf);
    134 	}
    135 	if (EFI_ERROR(status)) {
    136 		DPRINT(L"efirng: GetRNG: %r\n", status);
    137 		return EIO;
    138 	}
    139 
    140 	return 0;
    141 }
    142