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Date:   Mon, 21 Feb 2022 02:46:26 +0100
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     keyrings@vger.kernel.org, David Howells <dhowells@redhat.com>,
        linux-crypto@vger.kernel.org, linux-integrity@vger.kernel.org,
        Stefan Berger <stefanb@linux.ibm.com>,
        Gilad Ben-Yossef <gilad@benyossef.com>,
        Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
        Vitaly Chikunov <vt@altlinux.org>,
        Mimi Zohar <zohar@linux.ibm.com>, stable@vger.kernel.org
Subject: Re: [PATCH 2/2] KEYS: asymmetric: properly validate hash_algo and
 encoding
Message-ID: <YhLu8gZtdpphy5mB@kernel.org>
References: <20220201003414.55380-1-ebiggers@kernel.org>
 <20220201003414.55380-3-ebiggers@kernel.org>
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On Mon, Jan 31, 2022 at 04:34:14PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> It is insecure to allow arbitrary hash algorithms and signature
> encodings to be used with arbitrary signature algorithms.  Notably,
> ECDSA, ECRDSA, and SM2 all sign/verify raw hash values and don't
> disambiguate between different hash algorithms like RSA PKCS#1 v1.5
> padding does.  Therefore, they need to be restricted to certain sets of
> hash algorithms (ideally just one, but in practice small sets are used).
> Additionally, the encoding is an integral part of modern signature
> algorithms, and is not supposed to vary.
> 
> Therefore, tighten the checks of hash_algo and encoding done by
> software_key_determine_akcipher().
> 
> Also rearrange the parameters to software_key_determine_akcipher() to
> put the public_key first, as this is the most important parameter and it
> often determines everything else.
> 
> Fixes: 299f561a6693 ("x509: Add support for parsing x509 certs with ECDSA keys")
> Fixes: 215525639631 ("X.509: support OSCCA SM2-with-SM3 certificate verification")
> Fixes: 0d7a78643f69 ("crypto: ecrdsa - add EC-RDSA (GOST 34.10) algorithm")
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  crypto/asymmetric_keys/public_key.c | 111 +++++++++++++++++++---------
>  1 file changed, 76 insertions(+), 35 deletions(-)
> 
> diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
> index aba7113d86c76..a603ee8afdb8d 100644
> --- a/crypto/asymmetric_keys/public_key.c
> +++ b/crypto/asymmetric_keys/public_key.c
> @@ -60,39 +60,83 @@ static void public_key_destroy(void *payload0, void *payload3)
>  }
>  
>  /*
> - * Determine the crypto algorithm name.
> + * Given a public_key, and an encoding and hash_algo to be used for signing
> + * and/or verification with that key, determine the name of the corresponding
> + * akcipher algorithm.  Also check that encoding and hash_algo are allowed.
>   */
> -static
> -int software_key_determine_akcipher(const char *encoding,
> -				    const char *hash_algo,
> -				    const struct public_key *pkey,
> -				    char alg_name[CRYPTO_MAX_ALG_NAME])
> +static int
> +software_key_determine_akcipher(const struct public_key *pkey,
> +				const char *encoding, const char *hash_algo,
> +				char alg_name[CRYPTO_MAX_ALG_NAME])

Why is changing parameter order necessary?

BR, Jarkko