Commit 95c4e20a authored Aug 31, 2022 by Ignat Korchagin Committed by Greg Kroah-Hartman Oct 26, 2022

crypto: akcipher - default implementation for setting a private key



[ Upstream commit bc155c6c188c2f0c5749993b1405673d25a80389 ]

Changes from v1:
  * removed the default implementation from set_pub_key: it is assumed that
    an implementation must always have this callback defined as there are
    no use case for an algorithm, which doesn't need a public key

Many akcipher implementations (like ECDSA) support only signature
verifications, so they don't have all callbacks defined.

Commit 78a0324f ("crypto: akcipher - default implementations for
request callbacks") introduced default callbacks for sign/verify
operations, which just return an error code.

However, these are not enough, because before calling sign the caller would
likely call set_priv_key first on the instantiated transform (as the
in-kernel testmgr does). This function does not have a default stub, so the
kernel crashes, when trying to set a private key on an akcipher, which
doesn't support signature generation.

I've noticed this, when trying to add a KAT vector for ECDSA signature to
the testmgr.

With this patch the testmgr returns an error in dmesg (as it should)
instead of crashing the kernel NULL ptr dereference.

Fixes: 78a0324f ("crypto: akcipher - default implementations for request callbacks")
Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 4010a1af

crypto/akcipher.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -119,6 +119,12 @@ static int akcipher_default_op(struct akcipher_request *req)
		return -ENOSYS;
		}

		static int akcipher_default_set_key(struct crypto_akcipher *tfm,
		const void *key, unsigned int keylen)
		{
		return -ENOSYS;
		}

		int crypto_register_akcipher(struct akcipher_alg *alg)
		{
		struct crypto_alg *base = &alg->base;
		@@ -131,6 +137,8 @@ int crypto_register_akcipher(struct akcipher_alg *alg)
		alg->encrypt = akcipher_default_op;
		if (!alg->decrypt)
		alg->decrypt = akcipher_default_op;
		if (!alg->set_priv_key)
		alg->set_priv_key = akcipher_default_set_key;

		akcipher_prepare_alg(alg);
		return crypto_register_alg(base);