crypto: arm64/neonbs - fix out-of-bounds access on short input
Subsystems (2)
PATCH v2 1/1 crypto: arm64/neonbs - fix out-of-bounds access on short input
From: Ard Biesheuvel <[email protected]>
The bit-sliced implementation of AES-CTR operates on blocks of 128 bytes, and will fall back to the plain NEON version for tail blocks or inputs that are shorter than 128 bytes to begin with.
It will call straight into the plain NEON asm helper, which performs all memory accesses in granules of 16 bytes (the size of a NEON register). For this reason, the associated plain NEON glue code will copy inputs shorter than 16 bytes into a temporary buffer, given that this is a rare occurrence and it is not worth the effort to work around this in the asm code.
The fallback from the bit-sliced NEON version fails to take this into account, potentially resulting in out-of-bounds accesses. So clone the same workaround, and use a temp buffer for short in/outputs.
--- arch/arm64/crypto/aes-neonbs-glue.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
arch/arm64/crypto/aes-neonbs-glue.c +11 -0
@@ -227,8 +227,19 @@ static int ctr_encrypt(struct skcipher_request *req) src += blocks *AES_BLOCK_SIZE ; }if (nbytes && walk.nbytes == walk.total) { +u8 buf[AES_BLOCK_SIZE ]; +u8 *d = dst; + +if (unlikely (nbytes <AES_BLOCK_SIZE )) + src = dst =memcpy (buf +sizeof (buf) - nbytes, + src, nbytes); +neon_aes_ctr_encrypt (dst, src, ctx->enc, ctx->key.rounds, nbytes, walk.iv); + +if (unlikely (nbytes <AES_BLOCK_SIZE )) +memcpy (d, dst, nbytes); + nbytes =0 ; }kernel_neon_end ();
Signature · 1 line
2.44.0.rc0.258.g7320e95886-goog
Herbert Xu
maintainerQuoted 17 lines · Ard Biesheuvel
From: Ard Biesheuvel <[email protected]>
The bit-sliced implementation of AES-CTR operates on blocks of 128 bytes, and will fall back to the plain NEON version for tail blocks or inputs that are shorter than 128 bytes to begin with.
It will call straight into the plain NEON asm helper, which performs all memory accesses in granules of 16 bytes (the size of a NEON register). For this reason, the associated plain NEON glue code will copy inputs shorter than 16 bytes into a temporary buffer, given that this is a rare occurrence and it is not worth the effort to work around this in the asm code.
The fallback from the bit-sliced NEON version fails to take this into account, potentially resulting in out-of-bounds accesses. So clone the same workaround, and use a temp buffer for short in/outputs.
Quoted 7 lines
Fixes fc074e130051 ("crypto: arm64/aes-neonbs-ctr - fallback to plain NEON for final chunk")Reported-by [email protected]Reviewed-by Eric Biggers <[email protected]>Signed-off-by Ard Biesheuvel <[email protected]>--- arch/arm64/crypto/aes-neonbs-glue.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
Patch applied. Thanks.
Signature · 3 lines
Email: Herbert Xu <[email protected]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt