Check at use-time whether an skcipher request is on the stack. If it is, enforce that it must be backed by a synchronous algorithm, as is required: https://www.redhat.com/archives/dm-devel/2018-January/msg00087.html Co-developed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- include/crypto/skcipher.h | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h index 6e954d398e0f..3aabd5d098ed 100644 --- a/include/crypto/skcipher.h +++ b/include/crypto/skcipher.h @@ -19,6 +19,7 @@ /** * struct skcipher_request - Symmetric key cipher request + * @__onstack: 1 if the request was allocated by SKCIPHER_REQUEST_ON_STACK * @cryptlen: Number of bytes to encrypt or decrypt * @iv: Initialisation Vector * @src: Source SG list @@ -27,6 +28,7 @@ * @__ctx: Start of private context data */ struct skcipher_request { + unsigned char __onstack; unsigned int cryptlen; u8 *iv; @@ -139,9 +141,12 @@ struct skcipher_alg { struct crypto_alg base; }; +/* + * This must only ever be used with synchronous algorithms. + */ #define SKCIPHER_REQUEST_ON_STACK(name, tfm) \ char __##name##_desc[sizeof(struct skcipher_request) + \ - crypto_skcipher_reqsize(tfm)] CRYPTO_MINALIGN_ATTR; \ + crypto_skcipher_reqsize(tfm)] CRYPTO_MINALIGN_ATTR = { 1 }; \ struct skcipher_request *name = (void *)__##name##_desc /** @@ -437,6 +442,12 @@ static inline struct crypto_skcipher *crypto_skcipher_reqtfm_check( { struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); + if (req->__onstack) { + if (WARN_ON(crypto_skcipher_alg(tfm)->base.cra_flags & + CRYPTO_ALG_ASYNC)) + return ERR_PTR(-EINVAL); + } + if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY) return ERR_PTR(-ENOKEY); -- 2.17.1
