Add support for getting early entropy from UEFI

UEFI provides a protocol for accessing randomness. This is a good way
to gather early entropy, especially when there's no driver for the RNG
on the platform (as is the case on the Marvell Armada8k (MACCHIATObin)
for now).

If the entropy_efi_seed option is enabled in loader.conf (default: YES)
obtain 2048 bytes of entropy from UEFI and pass is to the kernel as a
"module" of name "efi_rng_seed" and type "boot_entropy_platform"; if
present, ingest it into the kernel RNG.

Submitted by:	Greg V
Reviewed by:	markm, kevans
Approved by:	csprng (markm)
MFC after:	3 weeks
Differential Revision:	https://reviews.freebsd.org/D20780

stand/defaults/loader.conf

@@ -42,12 +42,14 @@ hostuuid_type="hostuuid"
 # See rc.conf(5). The entropy_boot_file config variable must agree with the
 # settings below.
 entropy_cache_load="YES"		# Set this to NO to disable loading
-					# entropy at boot time
+					# cached entropy at boot time
 entropy_cache_name="/boot/entropy"	# Set this to the name of the file
 entropy_cache_type="boot_entropy_cache"	# Required for the kernel to find
 					# the boot-time entropy cache. This
 					# must not change value even if the
 					# _name above does change!
+entropy_efi_seed="YES"		# Set this to NO to disable loading
+					# entropy from the UEFI hardware random number generator API
 
 ###  RAM Blacklist configuration  ############################
 ram_blacklist_load="NO"			# Set this to YES to load a file

stand/efi/include/efirng.h

@@ -0,0 +1,50 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright 2006 - 2016 Unified EFI, Inc.<BR>
+ * Copyright (c) 2013 - 2016, Intel Corporation. All rights reserved.<BR>   
+ * This program and the accompanying materials
+ * are licensed and made available under the terms and conditions of the BSD License
+ * which accompanies this distribution.  The full text of the license may be found at 
+ * http://opensource.org/licenses/bsd-license.php
+ *
+ * THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+ *
+ */
+
+#ifndef _EFIRNG_H
+#define _EFIRNG_H
+
+#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;
+
+#endif /* _EFIRNG_H */

stand/efi/loader/main.c

@@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
 #include <efi.h>
 #include <efilib.h>
 #include <efichar.h>
+#include <efirng.h>
 
 #include <uuid.h>
 
@@ -1204,6 +1205,47 @@ main(int argc, CHAR16 *argv[])
 	return (EFI_SUCCESS);		/* keep compiler happy */
 }
 
+COMMAND_SET(efi_seed_entropy, "efi-seed-entropy", "try to get entropy from the EFI RNG", command_seed_entropy);
+
+static int
+command_seed_entropy(int argc, char *argv[])
+{
+	EFI_STATUS status;
+	EFI_RNG_PROTOCOL *rng;
+	unsigned int size = 2048;
+	void *buf;
+
+	if (argc > 1) {
+		size = strtol(argv[1], NULL, 0);
+	}
+
+	status = BS->LocateProtocol(&rng_guid, NULL, (VOID **)&rng);
+	if (status != EFI_SUCCESS) {
+		command_errmsg = "RNG protocol not found";
+		return (CMD_ERROR);
+	}
+
+	if ((buf = malloc(size)) == NULL) {
+		command_errmsg = "out of memory";
+		return (CMD_ERROR);
+	}
+
+	status = rng->GetRNG(rng, NULL, size, (UINT8 *)buf);
+	if (status != EFI_SUCCESS) {
+		free(buf);
+		command_errmsg = "GetRNG failed";
+		return (CMD_ERROR);
+	}
+
+	if (file_addbuf("efi_rng_seed", "boot_entropy_platform", size, buf) != 0) {
+		free(buf);
+		return (CMD_ERROR);
+	}
+
+	free(buf);
+	return (CMD_OK);
+}
+
 COMMAND_SET(poweroff, "poweroff", "power off the system", command_poweroff);
 
 static int

stand/lua/core.lua

@@ -351,6 +351,14 @@ function core.changeRewindCheckpoint()
 	end
 end
 
+function core.loadEntropy()
+	if core.isUEFIBoot() then
+		if (loader.getenv("entropy_efi_seed") or "no"):lower() == "yes" then
+			loader.perform("efi-seed-entropy")
+		end
+	end
+end
+
 function core.setDefaults()
 	core.setACPI(core.getACPIPresent(true))
 	core.setSafeMode(default_safe_mode)
@@ -363,6 +371,7 @@ function core.autoboot(argstr)
 	if loader.getenv("kernelname") == nil then
 		config.loadelf()
 	end
+	core.loadEntropy()
 	loader.perform(composeLoaderCmd("autoboot", argstr))
 end
 
@@ -371,6 +380,7 @@ function core.boot(argstr)
 	if loader.getenv("kernelname") == nil then
 		config.loadelf()
 	end
+	core.loadEntropy()
 	loader.perform(composeLoaderCmd("boot", argstr))
 end
 

sys/dev/random/random_harvestq.c

@@ -488,6 +488,14 @@ random_harvestq_prime(void *unused __unused)
 		else
 			printf("random: no preloaded entropy cache\n");
 	}
+	size = random_prime_loader_file(RANDOM_PLATFORM_BOOT_ENTROPY_MODULE);
+	if (bootverbose) {
+		if (size > 0)
+			printf("random: read %zu bytes from platform bootloader\n",
+			    size);
+		else
+			printf("random: no platform bootloader entropy\n");
+	}
 }
 SYSINIT(random_device_prime, SI_SUB_RANDOM, SI_ORDER_MIDDLE, random_harvestq_prime, NULL);
 

sys/sys/random.h

@@ -110,6 +110,7 @@ _Static_assert(ENTROPYSOURCE <= 32,
     "hardcoded assumption that values fit in a typical word-sized bitset");
 
 #define RANDOM_CACHED_BOOT_ENTROPY_MODULE	"boot_entropy_cache"
+#define RANDOM_PLATFORM_BOOT_ENTROPY_MODULE	"boot_entropy_platform"
 
 extern u_int hc_source_mask;
 void random_harvest_queue_(const void *, u_int, enum random_entropy_source);