The UEFI standard defines an (optional) protocol for getting random
numbers. A while back I wrote support for this for the arm64
bootloader. But we should use this on amd64 as well. I tested that
this actually works on a machine with a recent AMD Ryzen APU. Not
sure if the firmware implements this using RDRAND or if it uses the
random number generator of the integrated crypto unit. Either way,
this can't make matters worse since the "entropy" is XORed into the
random data buffer.
ok?
Index: arch/amd64/stand/efiboot/Makefile.common
===================================================================
RCS file: /cvs/src/sys/arch/amd64/stand/efiboot/Makefile.common,v
retrieving revision 1.14
diff -u -p -r1.14 Makefile.common
--- arch/amd64/stand/efiboot/Makefile.common 20 Apr 2019 22:59:03 -0000
1.14
+++ arch/amd64/stand/efiboot/Makefile.common 4 May 2019 20:59:48 -0000
@@ -11,7 +11,7 @@ EFI_HEAP_LIMIT= 0xc00000
LDFLAGS+= -nostdlib -T${.CURDIR}/../${LDSCRIPT} -Bsymbolic -shared
-COPTS+= -DEFIBOOT -DNEEDS_HEAP_H -I${.CURDIR}/..
+COPTS+= -DEFIBOOT -DFWRANDOM -DNEEDS_HEAP_H -I${.CURDIR}/..
COPTS+= -I${EFIDIR}/include -I${S}/stand/boot
COPTS+= -ffreestanding -std=gnu99
COPTS+= -fshort-wchar -fPIC -mno-red-zone
@@ -24,7 +24,7 @@ AFLAGS+= -pipe -fPIC
.PATH: ${.CURDIR}/..
SRCS+= self_reloc.c
-SRCS+= efiboot.c efidev.c efipxe.c
+SRCS+= efiboot.c efidev.c efipxe.c efirng.c
SRCS+= conf.c
.PATH: ${S}/stand/boot
Index: arch/amd64/stand/efiboot/efirng.c
===================================================================
RCS file: arch/amd64/stand/efiboot/efirng.c
diff -N arch/amd64/stand/efiboot/efirng.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ arch/amd64/stand/efiboot/efirng.c 4 May 2019 20:59:48 -0000
@@ -0,0 +1,87 @@
+/* $OpenBSD: efirng.c,v 1.1 2018/04/08 13:27:22 kettenis Exp $ */
+
+/*
+ * Copyright (c) 2018 Mark Kettenis <kette...@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/param.h>
+
+#include <efi.h>
+#include <efiapi.h>
+
+#include "eficall.h"
+#include "libsa.h"
+
+extern EFI_BOOT_SERVICES *BS;
+
+/* Random Number Generator Protocol */
+
+#define EFI_RNG_PROTOCOL_GUID \
+ { 0x3152bca5, 0xeade, 0x433d, {0x86, 0x2e, 0xc0, 0x1c, 0xdc, 0x29, 0x1f,
0x44} }
+
+INTERFACE_DECL(_EFI_RNG_PROTOCOL);
+
+typedef EFI_GUID EFI_RNG_ALGORITHM;
+
+typedef
+EFI_STATUS
+(EFIAPI *EFI_RNG_GET_INFO) (
+ IN struct _EFI_RNG_PROTOCOL *This,
+ IN OUT UINTN *RNGAlgorithmListSize,
+ OUT EFI_RNG_ALGORITHM *RNGAlgorithmList
+ );
+
+typedef
+EFI_STATUS
+(EFIAPI *EFI_RNG_GET_RNG) (
+ IN struct _EFI_RNG_PROTOCOL *This,
+ IN EFI_RNG_ALGORITHM *RNGAlgorithm, OPTIONAL
+ IN UINTN RNGValueLength,
+ OUT UINT8 *RNGValue
+ );
+
+typedef struct _EFI_RNG_PROTOCOL {
+ EFI_RNG_GET_INFO GetInfo;
+ EFI_RNG_GET_RNG GetRNG;
+} EFI_RNG_PROTOCOL;
+
+static EFI_GUID rng_guid = EFI_RNG_PROTOCOL_GUID;
+
+void
+fwrandom(char *buf, size_t buflen)
+{
+ EFI_STATUS status;
+ EFI_RNG_PROTOCOL *rng = NULL;
+ UINT8 *random;
+ size_t i;
+
+ status = EFI_CALL(BS->LocateProtocol, &rng_guid, NULL, (void **)&rng);
+ if (rng == NULL || EFI_ERROR(status))
+ return;
+
+ random = alloc(buflen);
+
+ status = EFI_CALL(rng->GetRNG, rng, NULL, buflen, random);
+ if (EFI_ERROR(status)) {
+ printf("RNG GetRNG() failed (%d)\n", status);
+ goto out;
+ }
+
+ for (i = 0; i < buflen; i++)
+ buf[i] ^= random[i];
+
+out:
+ free(random, buflen);
+}
