On Sat, Aug 19, 2017 at 04:17:40PM +0100, Ard Biesheuvel wrote:
> Early entropy is hard to come by, especially on non-x86 systems that
> lack an architected instruction and are not as uniform as PCs.
> Fortunately, on UEFI systems, we can invoke the EFI_RNG_PROTOCOL,
> which exposes the platform specific entropy source in a generic way.
> We use this protocol to fill the RNG UEFI config table (which is used
> during early boot to seed the kernel's entropy pool), and on ARM and
> arm64, we invoke it to seed KASLR as well.
>
> Sadly, EFI_RNG_PROTOCOL is not widely implemented, and so it would be
> nice to have a fallback for UEFI systems that lack it. So implement
> this fallback based on the Chaoskey RNG USB stick, which should be
> exposed using the standard UEFI USB I/O protocol if the firmware has
> USB support.
>
> Signed-off-by: Ard Biesheuvel <[email protected]>
> ---
> drivers/firmware/efi/Kconfig | 7 ++
> drivers/firmware/efi/libstub/Makefile | 2 +-
> drivers/firmware/efi/libstub/efistub.h | 3 +
> drivers/firmware/efi/libstub/random-chaoskey.c | 126
> +++++++++++++++++++++++++
> 4 files changed, 137 insertions(+), 1 deletion(-)
> create mode 100644 drivers/firmware/efi/libstub/random-chaoskey.c
>
> diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
> index 2b4c39fdfa91..448a6186d9fb 100644
> --- a/drivers/firmware/efi/Kconfig
> +++ b/drivers/firmware/efi/Kconfig
> @@ -87,6 +87,13 @@ config EFI_RUNTIME_WRAPPERS
> config EFI_ARMSTUB
> bool
>
> +config EFI_RNG_CHAOSKEY
> + bool "Chaoskey USB RNG support in the UEFI stub"
> + help
> + Fall back to a Chaoskey RNG USB stick in case EFI_RNG_PROTOCOL
> + is not implemented by the firmware. This is used for early
> + seeding of the entropy pool, and for KASLR on ARM and arm64.
> +
> config EFI_BOOTLOADER_CONTROL
> tristate "EFI Bootloader Control"
> depends on EFI_VARS
> diff --git a/drivers/firmware/efi/libstub/Makefile
> b/drivers/firmware/efi/libstub/Makefile
> index dedf9bde44db..fad6bc1d0e2a 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -40,7 +40,7 @@ $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
>
> lib-$(CONFIG_EFI_ARMSTUB) += arm-stub.o fdt.o string.o random.o \
> $(patsubst %.c,lib-%.o,$(arm-deps))
> -
> +lib-$(CONFIG_EFI_RNG_CHAOSKEY) += random-chaoskey.o
> lib-$(CONFIG_ARM) += arm32-stub.o
> lib-$(CONFIG_ARM64) += arm64-stub.o
> CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
> diff --git a/drivers/firmware/efi/libstub/efistub.h
> b/drivers/firmware/efi/libstub/efistub.h
> index 3afff5facd3b..9579ddb5937d 100644
> --- a/drivers/firmware/efi/libstub/efistub.h
> +++ b/drivers/firmware/efi/libstub/efistub.h
> @@ -62,6 +62,9 @@ efi_status_t efi_random_alloc(efi_system_table_t
> *sys_table_arg,
> unsigned long size, unsigned long align,
> unsigned long *addr, unsigned long random_seed);
>
> +efi_status_t efi_get_random_chaoskey(efi_system_table_t *sys_table_arg,
> + unsigned long size, u8 *out);
> +
> efi_status_t check_platform_features(efi_system_table_t *sys_table_arg);
>
> efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg);
> diff --git a/drivers/firmware/efi/libstub/random-chaoskey.c
> b/drivers/firmware/efi/libstub/random-chaoskey.c
> new file mode 100644
> index 000000000000..3f94ec3df9ff
> --- /dev/null
> +++ b/drivers/firmware/efi/libstub/random-chaoskey.c
> @@ -0,0 +1,126 @@
> +/*
> + * Copyright (C) 2017 Linaro Ltd; <[email protected]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +
> +#include <linux/efi.h>
> +#include <asm/efi.h>
> +
> +#include "efistub.h"
> +
> +#define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */
> +#define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */
> +
> +static efi_usb_io_protocol_t *chaoskey_usb_io;
> +static unsigned long chaoskey_usb_ep_addr, chaoskey_usb_ep_size;
> +
> +static void locate_chaoskey(efi_system_table_t *sys_table_arg)
> +{
> + efi_guid_t usb_io_guid = EFI_USB_IO_PROTOCOL_GUID;
> + unsigned long bufsize = 0, i, j;
> + efi_handle_t *handles;
> + efi_status_t status;
> +
> + chaoskey_usb_io = (void *)-1;
> +
> + /* find all USB devices that UEFI knows about */
> + status = efi_call_early(locate_handle, EFI_LOCATE_BY_PROTOCOL,
> + &usb_io_guid, NULL, &bufsize, NULL);
> + if (status != EFI_BUFFER_TOO_SMALL)
> + return;
> +
> + status = efi_call_early(allocate_pool, EFI_LOADER_DATA, bufsize,
> + (void **)&handles);
> + if (status != EFI_SUCCESS)
> + return;
> +
> + status = efi_call_early(locate_handle, EFI_LOCATE_BY_PROTOCOL,
> + &usb_io_guid, NULL, &bufsize, handles);
> + if (status != EFI_SUCCESS)
> + goto out;
> +
> + for (i = 0; i < bufsize / sizeof(efi_handle_t); i++) {
> + struct usb_device_descriptor dev;
> + struct usb_interface_descriptor iface;
> + efi_usb_io_protocol_t *p;
> +
> + status = efi_call_early(handle_protocol, handles[i],
> + &usb_io_guid, (void **)&p);
> + if (status != EFI_SUCCESS)
> + continue; /* shouldn't happen */
> +
> + /* get the device descriptor so we can check the vid/pid */
> + status = p->get_device_descriptor(p, &dev);
> + if (status != EFI_SUCCESS)
> + continue; /* shouldn't happen either */
> +
> + if (dev.idVendor != CHAOSKEY_VENDOR_ID ||
> + dev.idProduct != CHAOSKEY_PRODUCT_ID)
idVendor and idProduct are little endian types.
You have run sparse on this code, right?
> + continue;
> +
> + /* get the number of endpoints from the interface descriptor */
> + status = p->get_iface_descriptor(p, &iface);
> + if (status != EFI_SUCCESS)
> + continue;
> +
> + /* locate the first BULK IN endpoint */
> + for (j = 0; j < iface.bNumEndpoints; j++) {
> + struct usb_endpoint_descriptor ep;
Don't we have built-in usb functions for this now? Why not use them
instead of hand-rolling your own logic?
thanks,
greg k-h
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