diff mbox series

crypto: arm64/poly1305-neon - reorder PAC authentication with SP update

Message ID 20201026230027.25813-1-ardb@kernel.org
State Accepted
Delegated to: Herbert Xu
Headers show
Series crypto: arm64/poly1305-neon - reorder PAC authentication with SP update | expand

Commit Message

Ard Biesheuvel Oct. 26, 2020, 11 p.m. UTC
PAC pointer authentication signs the return address against the value
of the stack pointer, to prevent stack overrun exploits from corrupting
the control flow. However, this requires that the AUTIASP is issued with
SP holding the same value as it held when the PAC value was generated.
The Poly1305 NEON code got this wrong, resulting in crashes on PAC
capable hardware.

Fixes: f569ca164751 ("crypto: arm64/poly1305 - incorporate OpenSSL/CRYPTOGAMS ...")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/crypto/poly1305-armv8.pl       | 2 +-
 arch/arm64/crypto/poly1305-core.S_shipped | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

Comments

Eric Biggers Oct. 26, 2020, 11:03 p.m. UTC | #1
On Tue, Oct 27, 2020 at 12:00:27AM +0100, Ard Biesheuvel wrote:
> PAC pointer authentication signs the return address against the value
> of the stack pointer, to prevent stack overrun exploits from corrupting
> the control flow. However, this requires that the AUTIASP is issued with
> SP holding the same value as it held when the PAC value was generated.
> The Poly1305 NEON code got this wrong, resulting in crashes on PAC
> capable hardware.
> 
> Fixes: f569ca164751 ("crypto: arm64/poly1305 - incorporate OpenSSL/CRYPTOGAMS ...")
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  arch/arm64/crypto/poly1305-armv8.pl       | 2 +-
>  arch/arm64/crypto/poly1305-core.S_shipped | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)

This needs to be fixed at https://github.com/dot-asm/cryptogams too, I assume?

- Eric
Ard Biesheuvel Oct. 26, 2020, 11:04 p.m. UTC | #2
On Tue, 27 Oct 2020 at 00:03, Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Tue, Oct 27, 2020 at 12:00:27AM +0100, Ard Biesheuvel wrote:
> > PAC pointer authentication signs the return address against the value
> > of the stack pointer, to prevent stack overrun exploits from corrupting
> > the control flow. However, this requires that the AUTIASP is issued with
> > SP holding the same value as it held when the PAC value was generated.
> > The Poly1305 NEON code got this wrong, resulting in crashes on PAC
> > capable hardware.
> >
> > Fixes: f569ca164751 ("crypto: arm64/poly1305 - incorporate OpenSSL/CRYPTOGAMS ...")
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  arch/arm64/crypto/poly1305-armv8.pl       | 2 +-
> >  arch/arm64/crypto/poly1305-core.S_shipped | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
>
> This needs to be fixed at https://github.com/dot-asm/cryptogams too, I assume?
>

Yes, and in OpenSSL.
Ard Biesheuvel Oct. 26, 2020, 11:06 p.m. UTC | #3
(+ Andy)

On Tue, 27 Oct 2020 at 00:04, Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Tue, 27 Oct 2020 at 00:03, Eric Biggers <ebiggers@kernel.org> wrote:
> >
> > On Tue, Oct 27, 2020 at 12:00:27AM +0100, Ard Biesheuvel wrote:
> > > PAC pointer authentication signs the return address against the value
> > > of the stack pointer, to prevent stack overrun exploits from corrupting
> > > the control flow. However, this requires that the AUTIASP is issued with
> > > SP holding the same value as it held when the PAC value was generated.
> > > The Poly1305 NEON code got this wrong, resulting in crashes on PAC
> > > capable hardware.
> > >
> > > Fixes: f569ca164751 ("crypto: arm64/poly1305 - incorporate OpenSSL/CRYPTOGAMS ...")
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > ---
> > >  arch/arm64/crypto/poly1305-armv8.pl       | 2 +-
> > >  arch/arm64/crypto/poly1305-core.S_shipped | 2 +-
> > >  2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > This needs to be fixed at https://github.com/dot-asm/cryptogams too, I assume?
> >
>
> Yes, and in OpenSSL.
Andy Polyakov Oct. 29, 2020, 1:27 p.m. UTC | #4
> (+ Andy)

Thanks! Applied to cryptogams, pinged openssl. Cheers.
Herbert Xu Nov. 6, 2020, 7:01 a.m. UTC | #5
On Tue, Oct 27, 2020 at 12:00:27AM +0100, Ard Biesheuvel wrote:
> PAC pointer authentication signs the return address against the value
> of the stack pointer, to prevent stack overrun exploits from corrupting
> the control flow. However, this requires that the AUTIASP is issued with
> SP holding the same value as it held when the PAC value was generated.
> The Poly1305 NEON code got this wrong, resulting in crashes on PAC
> capable hardware.
> 
> Fixes: f569ca164751 ("crypto: arm64/poly1305 - incorporate OpenSSL/CRYPTOGAMS ...")
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  arch/arm64/crypto/poly1305-armv8.pl       | 2 +-
>  arch/arm64/crypto/poly1305-core.S_shipped | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)

Patch applied.  Thanks.
diff mbox series

Patch

diff --git a/arch/arm64/crypto/poly1305-armv8.pl b/arch/arm64/crypto/poly1305-armv8.pl
index 6e5576d19af8..cbc980fb02e3 100644
--- a/arch/arm64/crypto/poly1305-armv8.pl
+++ b/arch/arm64/crypto/poly1305-armv8.pl
@@ -840,7 +840,6 @@  poly1305_blocks_neon:
 	 ldp	d14,d15,[sp,#64]
 	addp	$ACC2,$ACC2,$ACC2
 	 ldr	x30,[sp,#8]
-	 .inst	0xd50323bf		// autiasp
 
 	////////////////////////////////////////////////////////////////
 	// lazy reduction, but without narrowing
@@ -882,6 +881,7 @@  poly1305_blocks_neon:
 	str	x4,[$ctx,#8]		// set is_base2_26
 
 	ldr	x29,[sp],#80
+	 .inst	0xd50323bf		// autiasp
 	ret
 .size	poly1305_blocks_neon,.-poly1305_blocks_neon
 
diff --git a/arch/arm64/crypto/poly1305-core.S_shipped b/arch/arm64/crypto/poly1305-core.S_shipped
index 8d1c4e420ccd..fb2822abf63a 100644
--- a/arch/arm64/crypto/poly1305-core.S_shipped
+++ b/arch/arm64/crypto/poly1305-core.S_shipped
@@ -779,7 +779,6 @@  poly1305_blocks_neon:
 	 ldp	d14,d15,[sp,#64]
 	addp	v21.2d,v21.2d,v21.2d
 	 ldr	x30,[sp,#8]
-	 .inst	0xd50323bf		// autiasp
 
 	////////////////////////////////////////////////////////////////
 	// lazy reduction, but without narrowing
@@ -821,6 +820,7 @@  poly1305_blocks_neon:
 	str	x4,[x0,#8]		// set is_base2_26
 
 	ldr	x29,[sp],#80
+	 .inst	0xd50323bf		// autiasp
 	ret
 .size	poly1305_blocks_neon,.-poly1305_blocks_neon