[edk2-devel] [PATCH v8 1/5] MdePkg: TimerRngLib: Added RngLib that uses TimerLib
Matthew Carlson
matthewfcarlson at gmail.com
Thu Aug 20 16:18:09 UTC 2020
Thank you Mike and Ard,
I'll definitely run ECC and resolve the code nits as well as the other
suggestions.
So the previous RNG code in OpenSSL just had a 10-microsecond delay in
between every 2 bytes. We could go back to that and match the behavior of
before but as Mike pointed out, this approach suffers on systems with slow
timer libs. I know this particular Rng library isn't meant to be a good
source of randomness and it is meant to offer a solution to those who don't
want to make the switch over to a good RngLib specifically for OpenSSL.
That said, I don't see any reason why we can't make this a better source of
random. I don't think it would be quite N, 2N, 3N, ... because of the
variability in the delay mechanism but I do agree that it would be quite
close to that. I'll throw out some options:
1. Implement a seeding mechanism that we mix in values with what we've
previously generated. So that it's no longer N, 2N, 3N but rather some sort
of hashing of the two numbers or other PRNG type system.
2. Use only 8 bits from the performance counter rather than 16. The idea
here is that it would roll over more frequently and you'd be more subject
to randomness. The downside is that this would take twice as long, which
means to generate 64 bits of random data, it would take at least 12
performance timer ticks, which on systems where their performance counters
run in KHz rather than MHz or GHz, means you could be looking at a delay of
milliseconds rather than microseconds. I'd argue in that case that the
platform should use a real RngLib rather than use this one if their timer
is so slow, but that's beside the point.
3. Have some way of specifying the delay that is less deterministic? There
are a few ways I can think of doing this but none are very good.I'm open to
suggestions.
-Matthew Carlson
On Thu, Aug 20, 2020 at 8:21 AM Kinney, Michael D <
michael.d.kinney at intel.com> wrote:
> Hi Matt,
>
> Some comments inline below.
>
> I also see come comments from Ard on this series about code style.
> I did not provide feedback on the code style issues here (except for
> a function header comment block style).
>
> There is a tool called ECC (EFI Code Checker) that is now enabled in
> EDK II CI. Please run this checker locally and resolve all issues in
> your patch series.
>
> Thanks,
>
> Mike
>
>
> > -----Original Message-----
> > From: matthewfcarlson at gmail.com <matthewfcarlson at gmail.com>
> > Sent: Wednesday, August 19, 2020 12:37 PM
> > To: devel at edk2.groups.io
> > Cc: Ard Biesheuvel <ard.biesheuvel at arm.com>; Kinney, Michael D <
> michael.d.kinney at intel.com>; Gao, Liming <liming.gao at intel.com>;
> > Liu, Zhiguang <zhiguang.liu at intel.com>; Matthew Carlson <
> matthewfcarlson at gmail.com>
> > Subject: [PATCH v8 1/5] MdePkg: TimerRngLib: Added RngLib that uses
> TimerLib
> >
> > From: Matthew Carlson <macarl at microsoft.com>
> >
> > Added a new RngLib that provides random numbers from the TimerLib
> > using the performance counter. This is meant to be used for OpenSSL
> > to replicate past behavior. This should not be used in production as
> > a real source of entropy.
> >
> > Ref: https://github.com/tianocore/edk2/pull/845
> > Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1871
> >
> > Cc: Ard Biesheuvel <ard.biesheuvel at arm.com>
> > Cc: Michael D Kinney <michael.d.kinney at intel.com>
> > Cc: Liming Gao <liming.gao at intel.com>
> > Cc: Zhiguang Liu <zhiguang.liu at intel.com>
> > Signed-off-by: Matthew Carlson <matthewfcarlson at gmail.com>
> > ---
> > MdePkg/Library/BaseRngLibTimerLib/RngLibTimer.c | 191
> ++++++++++++++++++++
> > MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf | 36 ++++
> > MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.uni | 15 ++
> > MdePkg/MdePkg.dsc | 3 +-
> > 4 files changed, 244 insertions(+), 1 deletion(-)
> >
> > diff --git a/MdePkg/Library/BaseRngLibTimerLib/RngLibTimer.c
> b/MdePkg/Library/BaseRngLibTimerLib/RngLibTimer.c
> > new file mode 100644
> > index 000000000000..c72aa335823d
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseRngLibTimerLib/RngLibTimer.c
> > @@ -0,0 +1,191 @@
> > +/** @file
> >
> > + BaseRng Library that uses the TimerLib to provide reasonably random
> numbers.
> >
> > + Do not use this on a production system.
> >
> > +
> >
> > + Copyright (c) Microsoft Corporation.
> >
> > + SPDX-License-Identifier: BSD-2-Clause-Patent
> >
> > +**/
> >
> > +
> >
> > +#include <Base.h>
> >
> > +#include <Library/BaseLib.h>
> >
> > +#include <Library/DebugLib.h>
> >
> > +#include <Library/TimerLib.h>
> >
> > +
> >
> > +/**
> >
> > + * Using the TimerLib GetPerformanceCounterProperties() we delay
> >
> > + * for enough time for the PerformanceCounter to increment.
> >
> > + * Depending on your system
>
>
> Please update the comments to describe that this function returns
> delay in microseconds. It does not actually do the delay.
>
> >
> > + *
> >
> > + * If the return value from GetPerformanceCounterProperties (TimerLib)
> >
> > + * is zero, this function will not delay and attempt to assert.
> >
> > + */
>
> Comment block style does not match EDK II style. Remove extra '*'.
>
>
> >
> > +STATIC
> >
> > +UINT32
> >
> > +CalculateMinimumDecentDelayInMicroseconds (
> >
> > + VOID
> >
> > + )
> >
> > +{
> >
> > + UINT64 StartValue;
>
> Remove
>
> >
> > + UINT64 EndValue;
>
> Remove
>
> >
> > + UINT64 CounterHz;
> >
> > + UINT64 MinumumDelayInMicroSeconds;
> >
> > +
> >
> > + // Get the counter properties
> >
> > + CounterHz = GetPerformanceCounterProperties (&StartValue, &EndValue);
>
>
> Change to:
>
> CounterHz = GetPerformanceCounterProperties (NULL, NULL);
>
> >
> > + // Make sure we won't divide by zero
> >
> > + if (CounterHz == 0) {
> >
> > + ASSERT(CounterHz != 0); // Assert so the developer knows something
> is wrong
> >
> > + return;
> >
> > + }
> >
> > + // Calculate the minimum delay based on 1.5 microseconds divided by
> the hertz.
> >
> > + // We calculate the length of a cycle (1/CounterHz) and multiply it
> by 1.5 microseconds
> >
> > + // This ensures that the performance counter has increased by at
> least one
> >
> > + return (UINT32)(MAX(DivU64x64Remainder(1500000 / CounterHz, NULL),
> 1));
> >
> > +}
> >
> > +
> >
> > +
> >
> > +/**
> >
> > + Generates a 16-bit random number.
> >
> > +
> >
> > + if Rand is NULL, then ASSERT().
> >
> > +
> >
> > + @param[out] Rand Buffer pointer to store the 16-bit random value.
> >
> > +
> >
> > + @retval TRUE Random number generated successfully.
> >
> > + @retval FALSE Failed to generate the random number.
> >
> > +
> >
> > +**/
> >
> > +BOOLEAN
> >
> > +EFIAPI
> >
> > +GetRandomNumber16 (
> >
> > + OUT UINT16 *Rand
> >
> > + )
> >
> > +{
> >
> > + UINT32 Index;
> >
> > + UINT8 *RandPtr;
> >
> > + UINT32 DelayInMicroSeconds;
> >
> > +
> >
> > + ASSERT (Rand != NULL);
> >
> > +
> >
> > + if (Rand == NULL) {
> >
> > + return FALSE;
> >
> > + }
> >
> > + DelayInMicroSeconds = CalculateMinimumDecentDelayInMicroseconds ();
> >
> > + RandPtr = (UINT8*)Rand;
> >
> > + // Get 2 bytes of random ish data
> >
> > + for (Index = 0; Index < 2; Index ++) {
> >
> > + *RandPtr = (UINT8)(GetPerformanceCounter () & 0xFF);
> >
> > + // Delay to give the performance counter a chance to change
> >
> > + MicroSecondDelay (DelayInMicroSeconds);
> >
> > + RandPtr++;
> >
> > + }
> >
> > + return TRUE;
> >
> > +}
> >
> > +
> >
> > +/**
> >
> > + Generates a 32-bit random number.
> >
> > +
> >
> > + if Rand is NULL, then ASSERT().
> >
> > +
> >
> > + @param[out] Rand Buffer pointer to store the 32-bit random value.
> >
> > +
> >
> > + @retval TRUE Random number generated successfully.
> >
> > + @retval FALSE Failed to generate the random number.
> >
> > +
> >
> > +**/
> >
> > +BOOLEAN
> >
> > +EFIAPI
> >
> > +GetRandomNumber32 (
> >
> > + OUT UINT32 *Rand
> >
> > + )
> >
> > +{
> >
> > + UINT32 Index;
> >
> > + UINT8 *RandPtr;
> >
> > + UINT32 DelayInMicroSeconds;
> >
> > +
> >
> > + ASSERT (Rand != NULL);
> >
> > +
> >
> > + if (NULL == Rand) {
> >
> > + return FALSE;
> >
> > + }
> >
> > +
> >
> > + RandPtr = (UINT8 *) Rand;
> >
> > + DelayInMicroSeconds = CalculateMinimumDecentDelayInMicroseconds ();
> >
> > + // Get 4 bytes of random ish data
> >
> > + for (Index = 0; Index < 4; Index ++) {
> >
> > + *RandPtr = (UINT8) (GetPerformanceCounter () & 0xFF);
> >
> > + // Delay to give the performance counter a chance to change
> >
> > + MicroSecondDelay (DelayInMicroSeconds);
> >
> > + RandPtr++;
> >
> > + }
> >
> > + return TRUE;
> >
> > +}
> >
> > +
> >
> > +/**
> >
> > + Generates a 64-bit random number.
> >
> > +
> >
> > + if Rand is NULL, then ASSERT().
> >
> > +
> >
> > + @param[out] Rand Buffer pointer to store the 64-bit random value.
> >
> > +
> >
> > + @retval TRUE Random number generated successfully.
> >
> > + @retval FALSE Failed to generate the random number.
> >
> > +
> >
> > +**/
> >
> > +BOOLEAN
> >
> > +EFIAPI
> >
> > +GetRandomNumber64 (
> >
> > + OUT UINT64 *Rand
> >
> > + )
> >
> > +{
> >
> > + UINT32 Index;
> >
> > + UINT8 *RandPtr;
> >
> > + UINT32 DelayInMicroSeconds;
> >
> > +
> >
> > + ASSERT (Rand != NULL);
> >
> > +
> >
> > + if (NULL == Rand) {
> >
> > + return FALSE;
> >
> > + }
> >
> > +
> >
> > + RandPtr = (UINT8 *) Rand;
> >
> > + DelayInMicroSeconds = CalculateMinimumDecentDelayInMicroseconds ();
> >
> > + // Get 8 bytes of random ish data
> >
> > + for (Index = 0; Index < 8; Index ++) {
> >
> > + *RandPtr = (UINT8)(GetPerformanceCounter () & 0xFF);
> >
> > + // Delay to give the performance counter a chance to change
> >
> > + MicroSecondDelay (DelayInMicroSeconds);
> >
> > + RandPtr++;
> >
> > + }
> >
> > +
> >
> > + return TRUE;
> >
> > +}
> >
> > +
> >
> > +/**
> >
> > + Generates a 128-bit random number.
> >
> > +
> >
> > + if Rand is NULL, then ASSERT().
> >
> > +
> >
> > + @param[out] Rand Buffer pointer to store the 128-bit random value.
> >
> > +
> >
> > + @retval TRUE Random number generated successfully.
> >
> > + @retval FALSE Failed to generate the random number.
> >
> > +
> >
> > +**/
> >
> > +BOOLEAN
> >
> > +EFIAPI
> >
> > +GetRandomNumber128 (
> >
> > + OUT UINT64 *Rand
> >
> > + )
> >
> > +{
> >
> > + ASSERT (Rand != NULL);
> >
> > + // This should take around 80ms
>
>
> Update comment to remove mention of specific delay and match
> similar comments in functions above.
>
> >
> > +
> >
> > + // Read first 64 bits
> >
> > + if (!GetRandomNumber64 (Rand)) {
> >
> > + return FALSE;
> >
> > + }
> >
> > +
> >
> > + // Read second 64 bits
> >
> > + return GetRandomNumber64 (++Rand);
> >
> > +}
> >
> > diff --git a/MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf
> b/MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf
> > new file mode 100644
> > index 000000000000..c499e5327351
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf
> > @@ -0,0 +1,36 @@
> > +## @file
> >
> > +# Instance of RNG (Random Number Generator) Library.
> >
> > +#
> >
> > +# BaseRng Library that uses the TimerLib to provide reasonably random
> numbers.
> >
> > +# Do NOT use this on a production system as this uses the system
> performance
> >
> > +# counter rather than a true source of random in addition to having a
> weak
> >
> > +# random algorithm. This is provided primarily as a source of entropy
> for
> >
> > +# OpenSSL for platforms that do not have a good built in RngLib as this
> >
> > +# emulates what was done before (though it isn't perfect).
> >
> > +#
> >
> > +# Copyright (c) Microsoft Corporation. All rights reserved.<BR>
> >
> > +#
> >
> > +# SPDX-License-Identifier: BSD-2-Clause-Patent
> >
> > +#
> >
> > +#
> >
> > +##
> >
> > +
> >
> > +[Defines]
> >
> > + INF_VERSION = 1.27
> >
> > + BASE_NAME = BaseRngLibTimerLib
> >
> > + MODULE_UNI_FILE = BaseRngLibTimerLib.uni
> >
> > + FILE_GUID = 74950C45-10FC-4AB5-B114-49C87C17409B
> >
> > + MODULE_TYPE = BASE
> >
> > + VERSION_STRING = 1.0
> >
> > + LIBRARY_CLASS = RngLib
> >
> > + CONSTRUCTOR = BaseRngLibConstructor
> >
> > +
> >
> > +[Sources]
> >
> > + RngLibTimer.c
> >
> > +
> >
> > +[Packages]
> >
> > + MdePkg/MdePkg.dec
> >
> > +
> >
> > +[LibraryClasses]
> >
> > + BaseLib
> >
> > + TimerLib
> >
> > diff --git a/MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.uni
> b/MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.uni
> > new file mode 100644
> > index 000000000000..fde24b9f0107
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.uni
> > @@ -0,0 +1,15 @@
> > +// @file
> >
> > +// Instance of RNG (Random Number Generator) Library.
> >
> > +//
> >
> > +// RngLib that uses TimerLib's performance counter to provide random
> numbers.
> >
> > +//
> >
> > +// Copyright (c) Microsoft Corporation.
> >
> > +//
> >
> > +// SPDX-License-Identifier: BSD-2-Clause-Patent
> >
> > +//
> >
> > +
> >
> > +
> >
> > +#string STR_MODULE_ABSTRACT #language en-US "Instance of RNG
> Library"
> >
> > +
> >
> > +#string STR_MODULE_DESCRIPTION #language en-US "BaseRng Library that
> uses the TimerLib to provide low-entropy random numbers"
> >
> > +
> >
> > diff --git a/MdePkg/MdePkg.dsc b/MdePkg/MdePkg.dsc
> > index 472fa3777412..d7ba3a730909 100644
> > --- a/MdePkg/MdePkg.dsc
> > +++ b/MdePkg/MdePkg.dsc
> > @@ -62,6 +62,8 @@
> > MdePkg/Library/BasePostCodeLibPort80/BasePostCodeLibPort80.inf
> >
> > MdePkg/Library/BasePrintLib/BasePrintLib.inf
> >
> >
> MdePkg/Library/BaseReportStatusCodeLibNull/BaseReportStatusCodeLibNull.inf
> >
> > + MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf
> >
> > + MdePkg/Library/BaseRngLibNull/BaseRngLibNull.inf
> >
> > MdePkg/Library/BaseSerialPortLibNull/BaseSerialPortLibNull.inf
> >
> > MdePkg/Library/BaseSynchronizationLib/BaseSynchronizationLib.inf
> >
> > MdePkg/Library/BaseTimerLibNullTemplate/BaseTimerLibNullTemplate.inf
> >
> > @@ -69,7 +71,6 @@
> >
> MdePkg/Library/BaseUefiDecompressLib/BaseUefiTianoCustomDecompressLib.inf
> >
> > MdePkg/Library/BaseSmbusLibNull/BaseSmbusLibNull.inf
> >
> > MdePkg/Library/BaseSafeIntLib/BaseSafeIntLib.inf
> >
> > - MdePkg/Library/BaseRngLibNull/BaseRngLibNull.inf
> >
> >
> >
> > MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf
> >
> > MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf
> >
> > --
> > 2.28.0.windows.1
>
>
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