linux-kernel - Re: [PATCH 4/8] akcipher: Move the RSA DER encoding to the crypto layer

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Date:	Wed, 24 Feb 2016 00:04:04 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	David Howells <dhowells@...hat.com>
Cc:	keyrings@...r.kernel.org, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, tadeusz.struk@...el.com
Subject: Re: [PATCH 4/8] akcipher: Move the RSA DER encoding to the crypto
 layer

On Fri, 2016-02-19 at 17:18 +0000, David Howells wrote:

>  /*
>   * Verify a signature using a public key.
>   */
>  int public_key_verify_signature(const struct public_key *pkey,
>  				const struct public_key_signature *sig)
>  {
> +	struct public_key_completion compl;
> +	struct crypto_akcipher *tfm;
> +	struct akcipher_request *req;
> +	struct scatterlist sig_sg, digest_sg;
> +	int ret = -ENOMEM;
> +
> +	pr_devel("==>%s()\n", __func__);
> +
>  	BUG_ON(!pkey);
>  	BUG_ON(!sig);
>  	BUG_ON(!sig->digest);
>  	BUG_ON(!sig->s);
> 
> -	if (pkey->pkey_algo >= PKEY_ALGO__LAST)
> -		return -ENOPKG;
> +	tfm = crypto_alloc_akcipher(pkey_algo_name[sig->pkey_algo], 0, 0);
> +	if (IS_ERR(tfm))
> +		return PTR_ERR(tfm);

IMA fails here.   The security.ima xattr header includes the hash
algorithm as defined in 
include/uapi/linux/hash_info.h.

struct signature_v2_hdr {
        uint8_t type;           /* xattr type */
        uint8_t version;        /* signature format version */
        uint8_t hash_algo;      /* Digest algorithm [enum pkey_hash_algo] */
        uint32_t keyid;         /* IMA key identifier - not X509/PGP specific */
        uint16_t sig_size;      /* signature size */
        uint8_t sig[0];         /* signature payload */
} __packed;

Mimi