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authorEric Biggers <ebiggers@google.com>2017-11-29 01:18:57 -0800
committerHerbert Xu <herbert@gondor.apana.org.au>2017-12-11 22:29:53 +1100
commit2b4f27c36bcd46e820ddb9a8e6fe6a63fa4250b8 (patch)
treef185bfdebe3769da7a82ea02cd394b3ed9736e91 /crypto
parent50c4c4e268a2d7a3e58ebb698ac74da0de40ae36 (diff)
download96b-common-2b4f27c36bcd46e820ddb9a8e6fe6a63fa4250b8.tar.gz
crypto: skcipher - set walk.iv for zero-length inputs
All the ChaCha20 algorithms as well as the ARM bit-sliced AES-XTS algorithms call skcipher_walk_virt(), then access the IV (walk.iv) before checking whether any bytes need to be processed (walk.nbytes). But if the input is empty, then skcipher_walk_virt() doesn't set the IV, and the algorithms crash trying to use the uninitialized IV pointer. Fix it by setting the IV earlier in skcipher_walk_virt(). Also fix it for the AEAD walk functions. This isn't a perfect solution because we can't actually align the IV to ->cra_alignmask unless there are bytes to process, for one because the temporary buffer for the aligned IV is freed by skcipher_walk_done(), which is only called when there are bytes to process. Thus, algorithms that require aligned IVs will still need to avoid accessing the IV when walk.nbytes == 0. Still, many algorithms/architectures are fine with IVs having any alignment, and even for those that aren't, a misaligned pointer bug is much less severe than an uninitialized pointer bug. This change also matches the behavior of the older blkcipher_walk API. Fixes: 0cabf2af6f5a ("crypto: skcipher - Fix crash on zero-length input") Reported-by: syzbot <syzkaller@googlegroups.com> Cc: <stable@vger.kernel.org> # v4.14+ Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto')
-rw-r--r--crypto/skcipher.c10
1 files changed, 4 insertions, 6 deletions
diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 778e0ff42bfa..11af5fd6a443 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -449,6 +449,8 @@ static int skcipher_walk_skcipher(struct skcipher_walk *walk,
walk->total = req->cryptlen;
walk->nbytes = 0;
+ walk->iv = req->iv;
+ walk->oiv = req->iv;
if (unlikely(!walk->total))
return 0;
@@ -456,9 +458,6 @@ static int skcipher_walk_skcipher(struct skcipher_walk *walk,
scatterwalk_start(&walk->in, req->src);
scatterwalk_start(&walk->out, req->dst);
- walk->iv = req->iv;
- walk->oiv = req->iv;
-
walk->flags &= ~SKCIPHER_WALK_SLEEP;
walk->flags |= req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP ?
SKCIPHER_WALK_SLEEP : 0;
@@ -510,6 +509,8 @@ static int skcipher_walk_aead_common(struct skcipher_walk *walk,
int err;
walk->nbytes = 0;
+ walk->iv = req->iv;
+ walk->oiv = req->iv;
if (unlikely(!walk->total))
return 0;
@@ -525,9 +526,6 @@ static int skcipher_walk_aead_common(struct skcipher_walk *walk,
scatterwalk_done(&walk->in, 0, walk->total);
scatterwalk_done(&walk->out, 0, walk->total);
- walk->iv = req->iv;
- walk->oiv = req->iv;
-
if (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP)
walk->flags |= SKCIPHER_WALK_SLEEP;
else