The kernel self-tests picked up an issue with CTR mode:
alg: skcipher: p8_aes_ctr encryption test failed (wrong result) on test vector 3, cfg="uneven misaligned splits, may sleep"
Test vector 3 has an IV of FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFD, so
after 3 increments it should wrap around to 0.
In the aesp8-ppc code from OpenSSL, there are two paths that
increment IVs: the bulk (8 at a time) path, and the individual
path which is used when there are fewer than 8 AES blocks to
process.
In the bulk path, the IV is incremented with vadduqm: "Vector
Add Unsigned Quadword Modulo", which does 128-bit addition.
In the individual path, however, the IV is incremented with
vadduwm: "Vector Add Unsigned Word Modulo", which instead
does 4 32-bit additions. Thus the IV would instead become
FFFFFFFFFFFFFFFFFFFFFFFF00000000, throwing off the result.
Use vadduqm.
This was probably a typo originally, what with q and w being
adjacent. It is a pretty narrow edge case: I am really
impressed by the quality of the kernel self-tests!
Fixes: 5c380d623ed3 ("crypto: vmx - Add support for VMS instructions by ASM")
Cc: [email protected]
Signed-off-by: Daniel Axtens <[email protected]>
---
I'll pass this along internally to get it into OpenSSL as well.
---
drivers/crypto/vmx/aesp8-ppc.pl | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/crypto/vmx/aesp8-ppc.pl b/drivers/crypto/vmx/aesp8-ppc.pl
index de78282b8f44..9c6b5c1d6a1a 100644
--- a/drivers/crypto/vmx/aesp8-ppc.pl
+++ b/drivers/crypto/vmx/aesp8-ppc.pl
@@ -1357,7 +1357,7 @@ Loop_ctr32_enc:
addi $idx,$idx,16
bdnz Loop_ctr32_enc
- vadduwm $ivec,$ivec,$one
+ vadduqm $ivec,$ivec,$one
vmr $dat,$inptail
lvx $inptail,0,$inp
addi $inp,$inp,16
--
2.19.1
On 05/15/2019 06:24 AM, Daniel Axtens wrote:
> The kernel self-tests picked up an issue with CTR mode:
> alg: skcipher: p8_aes_ctr encryption test failed (wrong result) on test vector 3, cfg="uneven misaligned splits, may sleep"
>
> Test vector 3 has an IV of FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFD, so
> after 3 increments it should wrap around to 0.
>
> In the aesp8-ppc code from OpenSSL, there are two paths that
> increment IVs: the bulk (8 at a time) path, and the individual
> path which is used when there are fewer than 8 AES blocks to
> process.
>
> In the bulk path, the IV is incremented with vadduqm: "Vector
> Add Unsigned Quadword Modulo", which does 128-bit addition.
>
> In the individual path, however, the IV is incremented with
> vadduwm: "Vector Add Unsigned Word Modulo", which instead
> does 4 32-bit additions. Thus the IV would instead become
> FFFFFFFFFFFFFFFFFFFFFFFF00000000, throwing off the result.
>
> Use vadduqm.
>
> This was probably a typo originally, what with q and w being
> adjacent. It is a pretty narrow edge case: I am really
> impressed by the quality of the kernel self-tests!
>
> Fixes: 5c380d623ed3 ("crypto: vmx - Add support for VMS instructions by ASM")
> Cc: [email protected]
> Signed-off-by: Daniel Axtens <[email protected]>
>
> ---
>
> I'll pass this along internally to get it into OpenSSL as well.
> ---
> drivers/crypto/vmx/aesp8-ppc.pl | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/crypto/vmx/aesp8-ppc.pl b/drivers/crypto/vmx/aesp8-ppc.pl
> index de78282b8f44..9c6b5c1d6a1a 100644
> --- a/drivers/crypto/vmx/aesp8-ppc.pl
> +++ b/drivers/crypto/vmx/aesp8-ppc.pl
> @@ -1357,7 +1357,7 @@ Loop_ctr32_enc:
> addi $idx,$idx,16
> bdnz Loop_ctr32_enc
>
> - vadduwm $ivec,$ivec,$one
> + vadduqm $ivec,$ivec,$one
> vmr $dat,$inptail
> lvx $inptail,0,$inp
> addi $inp,$inp,16
Acked-by: Nayna Jain <[email protected]>
Tested-by: Nayna Jain <[email protected]>
On Wed, May 15, 2019 at 08:24:50PM +1000, Daniel Axtens wrote:
> The kernel self-tests picked up an issue with CTR mode:
> alg: skcipher: p8_aes_ctr encryption test failed (wrong result) on test vector 3, cfg="uneven misaligned splits, may sleep"
>
> Test vector 3 has an IV of FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFD, so
> after 3 increments it should wrap around to 0.
>
> In the aesp8-ppc code from OpenSSL, there are two paths that
> increment IVs: the bulk (8 at a time) path, and the individual
> path which is used when there are fewer than 8 AES blocks to
> process.
>
> In the bulk path, the IV is incremented with vadduqm: "Vector
> Add Unsigned Quadword Modulo", which does 128-bit addition.
>
> In the individual path, however, the IV is incremented with
> vadduwm: "Vector Add Unsigned Word Modulo", which instead
> does 4 32-bit additions. Thus the IV would instead become
> FFFFFFFFFFFFFFFFFFFFFFFF00000000, throwing off the result.
>
> Use vadduqm.
>
> This was probably a typo originally, what with q and w being
> adjacent. It is a pretty narrow edge case: I am really
> impressed by the quality of the kernel self-tests!
>
> Fixes: 5c380d623ed3 ("crypto: vmx - Add support for VMS instructions by ASM")
> Cc: [email protected]
> Signed-off-by: Daniel Axtens <[email protected]>
>
> ---
>
> I'll pass this along internally to get it into OpenSSL as well.
> ---
> drivers/crypto/vmx/aesp8-ppc.pl | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Daniel Axtens <[email protected]> writes:
> The kernel self-tests picked up an issue with CTR mode:
> alg: skcipher: p8_aes_ctr encryption test failed (wrong result) on test vector 3, cfg="uneven misaligned splits, may sleep"
>
> Test vector 3 has an IV of FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFD, so
> after 3 increments it should wrap around to 0.
>
> In the aesp8-ppc code from OpenSSL, there are two paths that
> increment IVs: the bulk (8 at a time) path, and the individual
> path which is used when there are fewer than 8 AES blocks to
> process.
>
> In the bulk path, the IV is incremented with vadduqm: "Vector
> Add Unsigned Quadword Modulo", which does 128-bit addition.
>
> In the individual path, however, the IV is incremented with
> vadduwm: "Vector Add Unsigned Word Modulo", which instead
> does 4 32-bit additions. Thus the IV would instead become
> FFFFFFFFFFFFFFFFFFFFFFFF00000000, throwing off the result.
>
> Use vadduqm.
>
> This was probably a typo originally, what with q and w being
> adjacent. It is a pretty narrow edge case: I am really
> impressed by the quality of the kernel self-tests!
>
> Fixes: 5c380d623ed3 ("crypto: vmx - Add support for VMS instructions by ASM")
> Cc: [email protected]
> Signed-off-by: Daniel Axtens <[email protected]>
>
> ---
>
> I'll pass this along internally to get it into OpenSSL as well.
I passed this along to OpenSSL and got pretty comprehensively schooled:
https://github.com/openssl/openssl/pull/8942
It seems we tweak the openssl code to use a 128-bit counter, whereas
the original code was in fact designed for a 32-bit counter. We must
have changed the vaddu instruction in the bulk path but not in the
individual path, as they're both vadduwm (4x32-bit) upstream.
I think this change is still correct with regards to the kernel,
but I guess it's probably something where I should have done a more
thorough read of the documentation before diving in to the code, and
perhaps we should note it in the code somewhere too. Ah well.
Regards,
Daniel
> ---
> drivers/crypto/vmx/aesp8-ppc.pl | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/crypto/vmx/aesp8-ppc.pl b/drivers/crypto/vmx/aesp8-ppc.pl
> index de78282b8f44..9c6b5c1d6a1a 100644
> --- a/drivers/crypto/vmx/aesp8-ppc.pl
> +++ b/drivers/crypto/vmx/aesp8-ppc.pl
> @@ -1357,7 +1357,7 @@ Loop_ctr32_enc:
> addi $idx,$idx,16
> bdnz Loop_ctr32_enc
>
> - vadduwm $ivec,$ivec,$one
> + vadduqm $ivec,$ivec,$one
> vmr $dat,$inptail
> lvx $inptail,0,$inp
> addi $inp,$inp,16
> --
> 2.19.1
On Mon, May 20, 2019 at 11:59:05AM +1000, Daniel Axtens wrote:
> Daniel Axtens <[email protected]> writes:
>
> > The kernel self-tests picked up an issue with CTR mode:
> > alg: skcipher: p8_aes_ctr encryption test failed (wrong result) on test vector 3, cfg="uneven misaligned splits, may sleep"
> >
> > Test vector 3 has an IV of FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFD, so
> > after 3 increments it should wrap around to 0.
> >
> > In the aesp8-ppc code from OpenSSL, there are two paths that
> > increment IVs: the bulk (8 at a time) path, and the individual
> > path which is used when there are fewer than 8 AES blocks to
> > process.
> >
> > In the bulk path, the IV is incremented with vadduqm: "Vector
> > Add Unsigned Quadword Modulo", which does 128-bit addition.
> >
> > In the individual path, however, the IV is incremented with
> > vadduwm: "Vector Add Unsigned Word Modulo", which instead
> > does 4 32-bit additions. Thus the IV would instead become
> > FFFFFFFFFFFFFFFFFFFFFFFF00000000, throwing off the result.
> >
> > Use vadduqm.
> >
> > This was probably a typo originally, what with q and w being
> > adjacent. It is a pretty narrow edge case: I am really
> > impressed by the quality of the kernel self-tests!
> >
> > Fixes: 5c380d623ed3 ("crypto: vmx - Add support for VMS instructions by ASM")
> > Cc: [email protected]
> > Signed-off-by: Daniel Axtens <[email protected]>
> >
> > ---
> >
> > I'll pass this along internally to get it into OpenSSL as well.
>
> I passed this along to OpenSSL and got pretty comprehensively schooled:
> https://github.com/openssl/openssl/pull/8942
>
> It seems we tweak the openssl code to use a 128-bit counter, whereas
> the original code was in fact designed for a 32-bit counter. We must
> have changed the vaddu instruction in the bulk path but not in the
> individual path, as they're both vadduwm (4x32-bit) upstream.
>
> I think this change is still correct with regards to the kernel,
> but I guess it's probably something where I should have done a more
> thorough read of the documentation before diving in to the code, and
> perhaps we should note it in the code somewhere too. Ah well.
>
> Regards,
> Daniel
>
Ah, I didn't realize there are multiple conventions for CTR. Yes, all CTR
implementations in the kernel follow the 128-bit convention, and evidently the
test vectors test for that. Apparently the VMX OpenSSL code got incompletely
changed from the 32-bit convention by this commit, so that's what you're fixing:
commit 1d4aa0b4c1816e8ca92a6aadb0d8f6b43c56c0d0
Author: Leonidas Da Silva Barbosa <[email protected]>
Date: Fri Aug 14 10:12:22 2015 -0300
crypto: vmx - Fixing AES-CTR counter bug
AES-CTR is using a counter 8bytes-8bytes what miss match with
kernel specs.
In the previous code a vadduwm was done to increment counter.
Replacing this for a vadduqm now considering both cases counter
8-8 bytes and full 16bytes.
A comment in the code would indeed be helpful.
Note that the kernel doesn't currently need a 32-bit CTR implementation for GCM
like OpenSSL does, because the kernel currently only supports 12-byte IVs with
GCM. So the low 32 bits of the counter start at 1 and don't overflow,
regardless of whether the counter is incremented mod 2^32 or mod 2^128.
- Eric