Re: [PATCH v8 05/10] X.509: parse public key parameters from x509 for akcipher

Denis Kenzior
2019-03-26T16:14:43Z

Hi Vitaly,

On 03/26/2019 07:58 AM, Vitaly Chikunov wrote:
> Some public key algorithms (like EC-DSA) keep in parameters field
> important data such as digest and curve OIDs (possibly more for
> different EC-DSA variants). Thus, just setting a public key (as
> for RSA) is not enough.
>
> Append parameters into the key stream for akcipher_set_{pub,priv}_key.
> Appended data is: (u32) algo OID, (u32) parameters length, parameters
> data.
>
> This does not affect current akcipher API nor RSA ciphers (they could
> ignore it). Idea of appending parameters to the key stream is by Herbert
> Xu.
>
> Cc: David Howells <dhowells@redhat.com>
> Cc: keyrings@vger.kernel.org
> Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
> ---
> crypto/asymmetric_keys/asym_tpm.c | 43 ++++++++++++++++--
> crypto/asymmetric_keys/public_key.c | 72 ++++++++++++++++++++++++-------
> crypto/asymmetric_keys/x509.asn1 | 2 +-
> crypto/asymmetric_keys/x509_cert_parser.c | 31 +++++++++++++
> crypto/testmgr.c | 24 +++++++++--
> crypto/testmgr.h | 5 +++
> include/crypto/akcipher.h | 18 ++++----
> include/crypto/public_key.h | 4 ++
> 8 files changed, 168 insertions(+), 31 deletions(-)
>
> diff --git a/crypto/asymmetric_keys/asym_tpm.c b/crypto/asymmetric_keys/asym_tpm.c
> index 402fc34ca044..d95d7ec50e5a 100644
> --- a/crypto/asymmetric_keys/asym_tpm.c
> +++ b/crypto/asymmetric_keys/asym_tpm.c
> @@ -395,6 +395,12 @@ static int determine_akcipher(const char *encoding, const char *hash_algo,
> return -ENOPKG;
> }
>
> +static u8 *tpm_pack_u32(u8 *dst, u32 val)
> +{
> + memcpy(dst, &val, sizeof(val));
> + return dst + sizeof(val);
> +}
> +
> /*
> * Query information about a key.
> */
> @@ -407,6 +413,7 @@ static int tpm_key_query(const struct kernel_pkey_params *params,
> struct crypto_akcipher *tfm;
> uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
> uint32_t der_pub_key_len;
> + u8 *pkey, *ptr;
> int len;
>
> /* TPM only works on private keys, public keys still done in software */
> @@ -421,7 +428,16 @@ static int tpm_key_query(const struct kernel_pkey_params *params,
> der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
> der_pub_key);
>
> - ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
> + pkey = kmalloc(der_pub_key_len + sizeof(u32) * 2, GFP_KERNEL);
> + if (!pkey)
> + goto error_free_tfm;
> + memcpy(pkey, der_pub_key, der_pub_key_len);
> + ptr = pkey + der_pub_key_len;
> + /* Set dummy parameters to satisfy set_pub_key ABI. */
> + ptr = tpm_pack_u32(ptr, 0); /* algo */
> + ptr = tpm_pack_u32(ptr, 0); /* parameter length */
> +

Why not do all of this inside derive_pub_key? The only reason for that
function is to take a TPM-blob formatted public key and convert it to
ASN.1 format understood by crypto_akcipher_set_pub_key. So if you're
changing the format, might as well update that function.

> + ret = crypto_akcipher_set_pub_key(tfm, pkey, der_pub_key_len);
> if (ret < 0)
> goto error_free_tfm;
>
> @@ -440,6 +456,7 @@ static int tpm_key_query(const struct kernel_pkey_params *params,
>
> ret = 0;
> error_free_tfm:
> + kfree(pkey);
> crypto_free_akcipher(tfm);
> pr_devel("<==%s() = %d\n", __func__, ret);
> return ret;
> @@ -460,6 +477,7 @@ static int tpm_key_encrypt(struct tpm_key *tk,
> struct scatterlist in_sg, out_sg;
> uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
> uint32_t der_pub_key_len;
> + u8 *pkey, *ptr;
> int ret;
>
> pr_devel("==>%s()\n", __func__);
> @@ -475,7 +493,15 @@ static int tpm_key_encrypt(struct tpm_key *tk,
> der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
> der_pub_key);
>
> - ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
> + pkey = kmalloc(der_pub_key_len + sizeof(u32) * 2, GFP_KERNEL);
> + if (!pkey)
> + goto error_free_tfm;
> + memcpy(pkey, der_pub_key, der_pub_key_len);
> + ptr = pkey + der_pub_key_len;
> + ptr = tpm_pack_u32(ptr, 0); /* algo */
> + ptr = tpm_pack_u32(ptr, 0); /* parameter length */
> +

Same comment as above

> + ret = crypto_akcipher_set_pub_key(tfm, pkey, der_pub_key_len);
> if (ret < 0)
> goto error_free_tfm;
>
> @@ -500,6 +526,7 @@ static int tpm_key_encrypt(struct tpm_key *tk,
>
> akcipher_request_free(req);
> error_free_tfm:
> + kfree(pkey);
> crypto_free_akcipher(tfm);
> pr_devel("<==%s() = %d\n", __func__, ret);
> return ret;
> @@ -748,6 +775,7 @@ static int tpm_key_verify_signature(const struct key *key,
> char alg_name[CRYPTO_MAX_ALG_NAME];
> uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
> uint32_t der_pub_key_len;
> + u8 *pkey, *ptr;
> int ret;
>
> pr_devel("==>%s()\n", __func__);
> @@ -770,7 +798,15 @@ static int tpm_key_verify_signature(const struct key *key,
> der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
> der_pub_key);
>
> - ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
> + pkey = kmalloc(der_pub_key_len + sizeof(u32) * 2, GFP_KERNEL);
> + if (!pkey)
> + goto error_free_tfm;
> + memcpy(pkey, der_pub_key, der_pub_key_len);
> + ptr = pkey + der_pub_key_len;
> + ptr = tpm_pack_u32(ptr, 0); /* algo */
> + ptr = tpm_pack_u32(ptr, 0); /* parameter length */
> +

And here

> + ret = crypto_akcipher_set_pub_key(tfm, pkey, der_pub_key_len);
> if (ret < 0)
> goto error_free_tfm;
>
> @@ -792,6 +828,7 @@ static int tpm_key_verify_signature(const struct key *key,
>
> akcipher_request_free(req);
> error_free_tfm:
> + kfree(pkey);
> crypto_free_akcipher(tfm);
> pr_devel("<==%s() = %d\n", __func__, ret);
> if (WARN_ON_ONCE(ret > 0))

Regards,
-Denis