[efi] Add EFI entropy source
Originally-implemented-by: Jarrod Johnson <jbjohnso@us.ibm.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
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@ -50,6 +50,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#define ERRFILE_cpuid_cmd ( ERRFILE_ARCH | ERRFILE_OTHER | 0x00000000 )
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#define ERRFILE_cpuid_settings ( ERRFILE_ARCH | ERRFILE_OTHER | 0x00010000 )
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#define ERRFILE_efi_entropy ( ERRFILE_ARCH | ERRFILE_OTHER | 0x00020000 )
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/** @} */
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@ -0,0 +1,150 @@
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/*
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* Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <errno.h>
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#include <ipxe/entropy.h>
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#include <ipxe/efi/efi.h>
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/** @file
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*
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* EFI entropy source
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*
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*/
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/** Time (in 100ns units) to delay waiting for timer tick
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*
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* In theory, UEFI allows us to specify a trigger time of zero to
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* simply wait for the next timer tick. In practice, specifying zero
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* seems to often return immediately, which produces almost no
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* entropy. Specify a delay of 1000ns to try to force an existent
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* delay.
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*/
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#define EFI_ENTROPY_TRIGGER_TIME 10
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/** Event used to wait for timer tick */
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static EFI_EVENT tick;
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/**
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* Enable entropy gathering
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*
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* @ret rc Return status code
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*/
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static int efi_entropy_enable ( void ) {
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EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
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EFI_STATUS efirc;
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int rc;
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/* Create timer tick event */
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if ( ( efirc = bs->CreateEvent ( EVT_TIMER, TPL_NOTIFY, NULL, NULL,
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&tick ) ) != 0 ) {
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rc = -EEFI ( efirc );
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DBGC ( &tick, "ENTROPY could not create event: %s\n",
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strerror ( rc ) );
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return rc;
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}
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return 0;
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}
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/**
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* Disable entropy gathering
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*
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*/
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static void efi_entropy_disable ( void ) {
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EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
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/* Close timer tick event */
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bs->CloseEvent ( tick );
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}
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/**
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* Wait for an RTC tick
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*
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* @ret low TSC low-order bits, or negative error
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*/
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static int efi_entropy_tick ( void ) {
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EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
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UINTN index;
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uint16_t low;
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uint32_t discard_d;
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EFI_STATUS efirc;
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int rc;
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/* Wait for next timer tick */
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if ( ( efirc = bs->SetTimer ( tick, TimerRelative,
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EFI_ENTROPY_TRIGGER_TIME ) ) != 0 ) {
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rc = -EEFI ( efirc );
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DBGC ( &tick, "ENTROPY could not set timer: %s\n",
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strerror ( rc ) );
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return rc;
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}
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if ( ( efirc = bs->WaitForEvent ( 1, &tick, &index ) ) != 0 ) {
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rc = -EEFI ( efirc );
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DBGC ( &tick, "ENTROPY could not wait for timer tick: %s\n",
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strerror ( rc ) );
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return rc;
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}
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/* Get current TSC low-order bits */
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__asm__ __volatile__ ( "rdtsc" : "=a" ( low ), "=d" ( discard_d ) );
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return low;
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}
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/**
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* Get noise sample
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*
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* @ret noise Noise sample
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* @ret rc Return status code
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*/
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static int efi_get_noise ( noise_sample_t *noise ) {
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int before;
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int after;
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int rc;
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/* Wait for a timer tick */
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before = efi_entropy_tick();
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if ( before < 0 ) {
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rc = before;
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return rc;
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}
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/* Wait for another timer tick */
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after = efi_entropy_tick();
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if ( after < 0 ) {
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rc = after;
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return rc;
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}
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/* Use TSC delta as noise sample */
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*noise = ( after - before );
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return 0;
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}
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PROVIDE_ENTROPY_INLINE ( efi, min_entropy_per_sample );
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PROVIDE_ENTROPY ( efi, entropy_enable, efi_entropy_enable );
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PROVIDE_ENTROPY ( efi, entropy_disable, efi_entropy_disable );
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PROVIDE_ENTROPY ( efi, get_noise, efi_get_noise );
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@ -7,7 +7,7 @@
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*
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*/
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FILE_LICENCE ( GPL2_OR_LATER );
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#define UACCESS_EFI
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#define IOAPI_X86
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@ -19,7 +19,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
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#define SMBIOS_EFI
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#define SANBOOT_NULL
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#define BOFM_EFI
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#define ENTROPY_NULL
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#define ENTROPY_EFI
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#define TIME_NULL
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#define REBOOT_EFI
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@ -0,0 +1,35 @@
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#ifndef _IPXE_EFI_ENTROPY_H
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#define _IPXE_EFI_ENTROPY_H
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/** @file
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*
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* EFI entropy source
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*
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <stdint.h>
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#ifdef ENTROPY_EFI
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#define ENTROPY_PREFIX_efi
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#else
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#define ENTROPY_PREFIX_efi __efi_
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#endif
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/**
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* min-entropy per sample
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*
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* @ret min_entropy min-entropy of each sample
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*/
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static inline __always_inline double
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ENTROPY_INLINE ( efi, min_entropy_per_sample ) ( void ) {
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/* We use essentially the same mechanism as for the BIOS
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* RTC-based entropy source, and so assume the same
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* min-entropy per sample.
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*/
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return 1.3;
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}
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#endif /* _IPXE_EFI_ENTROPY_H */
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@ -54,6 +54,7 @@ typedef uint8_t entropy_sample_t;
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/* Include all architecture-independent entropy API headers */
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#include <ipxe/null_entropy.h>
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#include <ipxe/efi/efi_entropy.h>
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#include <ipxe/linux/linux_entropy.h>
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/* Include all architecture-dependent entropy API headers */
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