aarch64: support BTI and pointer authentication in assembly

This change adds optional support for
- Armv8.3-A Pointer Authentication (PAuth) and
- Armv8.5-A Branch Target Identificat

aarch64: support BTI and pointer authentication in assembly

This change adds optional support for
- Armv8.3-A Pointer Authentication (PAuth) and
- Armv8.5-A Branch Target Identification (BTI)
features to the perl scripts.

Both features can be enabled with additional compiler flags.
Unless any of these are enabled explicitly there is no code change at
all.

The extensions are briefly described below. Please read the appropriate
chapters of the Arm Architecture Reference Manual for the complete
specification.

Scope
-----

This change only affects generated assembly code.

Armv8.3-A Pointer Authentication
--------------------------------

Pointer Authentication extension supports the authentication of the
contents of registers before they are used for indirect branching
or load.

PAuth provides a probabilistic method to detect corruption of register
values. PAuth signing instructions generate a Pointer Authentication
Code (PAC) based on the value of a register, a seed and a key.
The generated PAC is inserted into the original value in the register.
A PAuth authentication instruction recomputes the PAC, and if it matches
the PAC in the register, restores its original value. In case of a
mismatch, an architecturally unmapped address is generated instead.

With PAuth, mitigation against ROP (Return-oriented Programming) attacks
can be implemented. This is achieved by signing the contents of the
link-register (LR) before it is pushed to stack. Once LR is popped,
it is authenticated. This way a stack corruption which overwrites the
LR on the stack is detectable.

The PAuth extension adds several new instructions, some of which are not
recognized by older hardware. To support a single codebase for both pre
Armv8.3-A targets and newer ones, only NOP-space instructions are added
by this patch. These instructions are treated as NOPs on hardware
which does not support Armv8.3-A. Furthermore, this patch only considers
cases where LR is saved to the stack and then restored before branching
to its content. There are cases in the code where LR is pushed to stack
but it is not used later. We do not address these cases as they are not
affected by PAuth.

There are two keys available to sign an instruction address: A and B.
PACIASP and PACIBSP only differ in the used keys: A and B, respectively.
The keys are typically managed by the operating system.

To enable generating code for PAuth compile with
-mbranch-protection=<mode>:

- standard or pac-ret: add PACIASP and AUTIASP, also enables BTI
(read below)
- pac-ret+b-key: add PACIBSP and AUTIBSP

Armv8.5-A Branch Target Identification
--------------------------------------

Branch Target Identification features some new instructions which
protect the execution of instructions on guarded pages which are not
intended branch targets.

If Armv8.5-A is supported by the hardware, execution of an instruction
changes the value of PSTATE.BTYPE field. If an indirect branch
lands on a guarded page the target instruction must be one of the
BTI <jc> flavors, or in case of a direct call or jump it can be any
other instruction. If the target instruction is not compatible with the
value of PSTATE.BTYPE a Branch Target Exception is generated.

In short, indirect jumps are compatible with BTI <j> and <jc> while
indirect calls are compatible with BTI <c> and <jc>. Please refer to the
specification for the details.

Armv8.3-A PACIASP and PACIBSP are implicit branch target
identification instructions which are equivalent with BTI c or BTI jc
depending on system register configuration.

BTI is used to mitigate JOP (Jump-oriented Programming) attacks by
limiting the set of instructions which can be jumped to.

BTI requires active linker support to mark the pages with BTI-enabled
code as guarded. For ELF64 files BTI compatibility is recorded in the
.note.gnu.property section. For a shared object or static binary it is
required that all linked units support BTI. This means that even a
single assembly file without the required note section turns-off BTI
for the whole binary or shared object.

The new BTI instructions are treated as NOPs on hardware which does
not support Armv8.5-A or on pages which are not guarded.

To insert this new and optional instruction compile with
-mbranch-protection=standard (also enables PAuth) or +bti.

When targeting a guarded page from a non-guarded page, weaker
compatibility restrictions apply to maintain compatibility between
legacy and new code. For detailed rules please refer to the Arm ARM.

Compiler support
----------------

Compiler support requires understanding '-mbranch-protection=<mode>'
and emitting the appropriate feature macros (__ARM_FEATURE_BTI_DEFAULT
and __ARM_FEATURE_PAC_DEFAULT). The current state is the following:

-------------------------------------------------------
| Compiler | -mbranch-protection | Feature macros |
+----------+---------------------+--------------------+
| clang | 9.0.0 | 11.0.0 |
+----------+---------------------+--------------------+
| gcc | 9 | expected in 10.1+ |
-------------------------------------------------------

Available Platforms
------------------

Arm Fast Model and QEMU support both extensions.

https://developer.arm.com/tools-and-software/simulation-models/fast-models
https://www.qemu.org/

Implementation Notes
--------------------

This change adds BTI landing pads even to assembly functions which are
likely to be directly called only. In these cases, landing pads might
be superfluous depending on what code the linker generates.
Code size and performance impact for these cases would be negligible.

Interaction with C code
-----------------------

Pointer Authentication is a per-frame protection while Branch Target
Identification can be turned on and off only for all code pages of a
whole shared object or static binary. Because of these properties if
C/C++ code is compiled without any of the above features but assembly
files support any of them unconditionally there is no incompatibility
between the two.

Useful Links
------------

To fully understand the details of both PAuth and BTI it is advised to
read the related chapters of the Arm Architecture Reference Manual
(Arm ARM):
https://developer.arm.com/documentation/ddi0487/latest/

Additional materials:

"Providing protection for complex software"
https://developer.arm.com/architectures/learn-the-architecture/providing-protection-for-complex-software

Arm Compiler Reference Guide Version 6.14: -mbranch-protection
https://developer.arm.com/documentation/101754/0614/armclang-Reference/armclang-Command-line-Options/-mbranch-protection?lang=en

Arm C Language Extensions (ACLE)
https://developer.arm.com/docs/101028/latest

Addional Notes
--------------

This patch is a copy of the work done by Tamas Petz in boringssl. It
contains the changes from the following commits:

aarch64: support BTI and pointer authentication in assembly
Change-Id: I4335f92e2ccc8e209c7d68a0a79f1acdf3aeb791
URL: https://boringssl-review.googlesource.com/c/boringssl/+/42084
aarch64: Improve conditional compilation
Change-Id: I14902a64e5f403c2b6a117bc9f5fb1a4f4611ebf
URL: https://boringssl-review.googlesource.com/c/boringssl/+/43524
aarch64: Fix name of gnu property note section
Change-Id: I6c432d1c852129e9c273f6469a8b60e3983671ec
URL: https://boringssl-review.googlesource.com/c/boringssl/+/44024

Change-Id: I2d95ebc5e4aeb5610d3b226f9754ee80cf74a9af

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16674)

show more ...

Update copyright year

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11616)

Also check for errors in x86_64-xlate.pl.

In https://github.com/openssl/openssl/pull/10883, I'd meant to exclude
the perlasm drivers since they aren't opening pipes and do not
partic

Also check for errors in x86_64-xlate.pl.

In https://github.com/openssl/openssl/pull/10883, I'd meant to exclude
the perlasm drivers since they aren't opening pipes and do not
particularly need it, but I only noticed x86_64-xlate.pl, so
arm-xlate.pl and ppc-xlate.pl got the change.

That seems to have been fine, so be consistent and also apply the change
to x86_64-xlate.pl. Checking for errors is generally a good idea.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: David Benjamin <davidben@google.com>
(Merged from https://github.com/openssl/openssl/pull/10930)

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Do not silently truncate files on perlasm errors

If one of the perlasm xlate drivers crashes, OpenSSL's build will
currently swallow the error and silently truncate the output to however

Do not silently truncate files on perlasm errors

If one of the perlasm xlate drivers crashes, OpenSSL's build will
currently swallow the error and silently truncate the output to however
far the driver got. This will hopefully fail to build, but better to
check such things.

Handle this by checking for errors when closing STDOUT (which is a pipe
to the xlate driver).

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10883)

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Fix side channel in ecp_nistz256-armv8.pl

This change addresses a potential side-channel vulnerability in
the internals of nistz256 low level operations for armv8.

Reviewed-by:

Fix side channel in ecp_nistz256-armv8.pl

This change addresses a potential side-channel vulnerability in
the internals of nistz256 low level operations for armv8.

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/9239)

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Unify all assembler file generators

They now generally conform to the following argument sequence:

script.pl "$(PERLASM_SCHEME)" [ C preprocessor arguments ... ] \

Unify all assembler file generators

They now generally conform to the following argument sequence:

script.pl "$(PERLASM_SCHEME)" [ C preprocessor arguments ... ] \
$(PROCESSOR) <output file>

However, in the spirit of being able to use these scripts manually,
they also allow for no argument, or for only the flavour, or for only
the output file. This is done by only using the last argument as
output file if it's a file (it has an extension), and only using the
first argument as flavour if it isn't a file (it doesn't have an
extension).

While we're at it, we make all $xlate calls the same, i.e. the $output
argument is always quoted, and we always die on error when trying to
start $xlate.

There's a perl lesson in this, regarding operator priority...

This will always succeed, even when it fails:

open FOO, "something" || die "ERR: $!";

The reason is that '||' has higher priority than list operators (a
function is essentially a list operator and gobbles up everything
following it that isn't lower priority), and since a non-empty string
is always true, so that ends up being exactly the same as:

open FOO, "something";

This, however, will fail if "something" can't be opened:

open FOO, "something" or die "ERR: $!";

The reason is that 'or' has lower priority that list operators,
i.e. it's performed after the 'open' call.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9884)

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Fix calling convention bug in ecp_nistz256_ord_sqr_mont

The rep parameter takes an int in C, but the assembly implementation
looks at the upper bits. While it's unlikely to happen here,

Fix calling convention bug in ecp_nistz256_ord_sqr_mont

The rep parameter takes an int in C, but the assembly implementation
looks at the upper bits. While it's unlikely to happen here, where all
calls pass a constant, in other scenarios x86_64 compilers will leave
arbitrary values in the upper half.

Fix this by making the C prototype match the assembly. (This aspect of
the calling convention implies smaller-than-word arguments in assembly
functions should be avoided. There are far fewer things to test if
everything consistently takes word-sized arguments.)

This was found as part of ABI testing work in BoringSSL.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/8108)

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ARM64 assembly pack: make it Windows-friendly.

"Windows friendliness" means a) unified PIC-ification, unified across
all platforms; b) unified commantary delimiter; c) explicit ldur/stur

ARM64 assembly pack: make it Windows-friendly.

"Windows friendliness" means a) unified PIC-ification, unified across
all platforms; b) unified commantary delimiter; c) explicit ldur/stur,
as Visual Studio assembler can't automatically encode ldr/str as
ldur/stur when needed.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8256)

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AArch64 assembly pack: authenticate return addresses.

ARMv8.3 adds pointer authentication extension, which in this case allows
to ensure that, when offloaded to stack, return address is

AArch64 assembly pack: authenticate return addresses.

ARMv8.3 adds pointer authentication extension, which in this case allows
to ensure that, when offloaded to stack, return address is same at return
as at entry to the subroutine. The new instructions are nops on processors
that don't implement the extension, so that the vetification is backward
compatible.

Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8205)

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Following the license change, modify the boilerplates in crypto/ec/

[skip ci]

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7

Following the license change, modify the boilerplates in crypto/ec/

[skip ci]

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7791)

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ec/asm/ecp_nistz256-{!x86_64}.pl: fix scatter_w7 function.

The ecp_nistz256_scatter_w7 function is called when application
attempts to use custom generator, i.e. rarely. Even though non-

ec/asm/ecp_nistz256-{!x86_64}.pl: fix scatter_w7 function.

The ecp_nistz256_scatter_w7 function is called when application
attempts to use custom generator, i.e. rarely. Even though non-x86_64
versions were wrong, it didn't affect point operations, they were just
not as fast as expected.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6738)

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Update copyright years on all files merged since Jan 1st 2018

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5038)

ec/asm/ecp_nistz256-armv8.pl: add optimized inversion.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5001)

Remove trailing whitespace from some files.

The prevailing style seems to not have trailing whitespace, but a few
lines do. This is mostly in the perlasm files, but a few C files got

Remove trailing whitespace from some files.

The prevailing style seems to not have trailing whitespace, but a few
lines do. This is mostly in the perlasm files, but a few C files got
them after the reformat. This is the result of:

find . -name '*.pl' | xargs sed -E -i '' -e 's/( |'$'\t'')*$//'
find . -name '*.c' | xargs sed -E -i '' -e 's/( |'$'\t'')*$//'
find . -name '*.h' | xargs sed -E -i '' -e 's/( |'$'\t'')*$//'

Then bn_prime.h was excluded since this is a generated file.

Note mkerr.pl has some changes in a heredoc for some help output, but
other lines there lack trailing whitespace too.

Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>

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ec/ecp_nistz256: harmonize is_infinity with ec_GFp_simple_is_at_infinity.

RT#4625

Reviewed-by: Rich Salz <rsalz@openssl.org>

ec/asm/ecp_nistz256-*.pl: addition to perform stricter reduction.

Addition was not preserving inputs' property of being fully reduced.

Thanks to Brian Smith for reporting this.

ec/asm/ecp_nistz256-*.pl: addition to perform stricter reduction.

Addition was not preserving inputs' property of being fully reduced.

Thanks to Brian Smith for reporting this.

Reviewed-by: Rich Salz <rsalz@openssl.org>

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Add OpenSSL copyright to .pl files

Reviewed-by: Richard Levitte <levitte@openssl.org>

Fix the spelling of "implement".

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>

Fix some assembler generating scripts for better unification

Some of these scripts would recognise an output parameter if it looks
like a file path. That works both in both the classic

Fix some assembler generating scripts for better unification

Some of these scripts would recognise an output parameter if it looks
like a file path. That works both in both the classic and new build
schemes. Some fo these scripts would only recognise it if it's a
basename (i.e. no directory component). Those need to be corrected,
as the output parameter in the new build scheme is more likely to
contain a directory component than not.

Reviewed-by: Andy Polyakov <appro@openssl.org>

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ec/asm/ecp_nistz256-*.pl: get corner case logic right.

RT#4284

Reviewed-by: Rich Salz <rsalz@openssl.org>

ec/asm/ecp_nistz256-armv8.pl: fix test_ssl spurious errors.

RT#4237

Reviewed-by: Matt Caswell <matt@openssl.org>

bn/asm/armv8-mont.pl: boost performance.

Reviewed-by: Richard Levitte <levitte@openssl.org>

Add ecp_nistz256-armv8 module.

Reviewed-by: Richard Levitte <levitte@openssl.org>