[PATCH v2 2/4] crypto: skcipher - Enforce non-ASYNC for on-stack requests
From: Kees Cook <hidden>
Date: 2018-09-06 22:59:17
Also in:
linux-arm-kernel, lkml
Subsystem:
crypto api, the rest · Maintainers:
Herbert Xu, "David S. Miller", Linus Torvalds
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 <redacted> Signed-off-by: Kees Cook <redacted> --- 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