Re: [PATCH 1/2] arm64 aes: fix encryption of unaligned data

On 26 July 2014 15:13, Ard Biesheuvel [off-list ref] wrote:

On 26 July 2014 01:40, Mikulas Patocka [off-list ref] wrote:

quoted

cryptsetup fails on arm64 when using kernel encryption via AF_ALG socket.
See https://bugzilla.redhat.com/show_bug.cgi?id=1122937

The bug is caused by incorrect handling of unaligned data in
arch/arm64/crypto/aes-glue.c. Cryptsetup creates a buffer that is aligned
on 8 bytes, but not on 16 bytes. It opens AF_ALG socket and uses the
socket to encrypt data in the buffer. The arm64 crypto accelerator causes
data corruption or crashes in the scatterwalk_pagedone.

This patch fixes the bug by passing the residue bytes that were not
processed as the last parameter to blkcipher_walk_done.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Acked-by: Ard Biesheuvel <redacted>

Thanks for the patch. This correctly fixes a thinko on my part
regarding the guarantees offered by the blkcipher API. Unfortunately,
this wasn't caught by the tcrypt test suite, so I will propose some
patches later to address cases like this.

BTW using kernel crypto with AF_ALG is fairly pointless when using
crypto instructions instead of crypto accelerator peripherals, should
we change anything on the kernel side so we don't expose these
drivers?

@Catalin: this is a bug fix for the code that was merged this cycle. I
would recommend to merge this for 3.16, but if not, could you please
add a cc stable? Or ack it and perhaps Herbert can take both? (There
is a similar patch for ARM as well)

... only this patch fails to repair the ECB case.
@Mikulas: could you do a v2 and include ECB encryption/decryption?

Cheers,
Ard.

quoted

Index: linux-3.16.0-0.rc6.git1.1.fc21.aarch64/arch/arm64/crypto/aes-glue.c
===================================================================

--- linux-3.16.0-0.rc6.git1.1.fc21.aarch64.orig/arch/arm64/crypto/aes-glue.c
+++ linux-3.16.0-0.rc6.git1.1.fc21.aarch64/arch/arm64/crypto/aes-glue.c

@@ -106,7 +106,7 @@ static int ecb_encrypt(struct blkcipher_
        for (first = 1; (blocks = (walk.nbytes / AES_BLOCK_SIZE)); first = 0) {
                aes_ecb_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
                                (u8 *)ctx->key_enc, rounds, blocks, first);
-               err = blkcipher_walk_done(desc, &walk, 0);
+               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
        }
        kernel_neon_end();
        return err;

@@ -128,7 +128,7 @@ static int ecb_decrypt(struct blkcipher_
        for (first = 1; (blocks = (walk.nbytes / AES_BLOCK_SIZE)); first = 0) {
                aes_ecb_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
                                (u8 *)ctx->key_dec, rounds, blocks, first);
-               err = blkcipher_walk_done(desc, &walk, 0);
+               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
        }
        kernel_neon_end();
        return err;

@@ -151,7 +151,7 @@ static int cbc_encrypt(struct blkcipher_
                aes_cbc_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
                                (u8 *)ctx->key_enc, rounds, blocks, walk.iv,
                                first);
-               err = blkcipher_walk_done(desc, &walk, 0);
+               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
        }
        kernel_neon_end();
        return err;

@@ -174,7 +174,7 @@ static int cbc_decrypt(struct blkcipher_
                aes_cbc_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
                                (u8 *)ctx->key_dec, rounds, blocks, walk.iv,
                                first);
-               err = blkcipher_walk_done(desc, &walk, 0);
+               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
        }
        kernel_neon_end();
        return err;

@@ -243,7 +243,7 @@ static int xts_encrypt(struct blkcipher_
                aes_xts_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
                                (u8 *)ctx->key1.key_enc, rounds, blocks,
                                (u8 *)ctx->key2.key_enc, walk.iv, first);
-               err = blkcipher_walk_done(desc, &walk, 0);
+               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
        }
        kernel_neon_end();

@@ -267,7 +267,7 @@ static int xts_decrypt(struct blkcipher_
                aes_xts_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
                                (u8 *)ctx->key1.key_dec, rounds, blocks,
                                (u8 *)ctx->key2.key_enc, walk.iv, first);
-               err = blkcipher_walk_done(desc, &walk, 0);
+               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
        }
        kernel_neon_end();