Implement EMSA_PKCS1-v1_5-ENCODE [RFC3447 sec 9.2] in rsa.c. It's the first step of signature generation operation (RSASSA-PKCS1-v1_5-SIGN). This patch is temporary set emLen to pks->k, and temporary set EM to pks->S for debugging. We will replace the above values to real signature after implement RSASP1. The naming of EMSA_PKCS1_v1_5_ENCODE and the variables used in this function accord PKCS#1 spec but not follow kernel naming convention, it useful when look at them with spec. Reference: ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1v2/pkcs1ietffinal.txt Reference: http://www.emc.com/collateral/white-papers/h11300-pkcs-1v2-2-rsa-cryptography-standard-wp.pdf V2: - Clean up naming of variable: replace _EM by EM, replace EM by EM_tmp. - Add comment to EMSA_PKCS1-v1_5-ENCODE function. Cc: Pavel Machek <pavel@xxxxxx> Reviewed-by: Jiri Kosina <jkosina@xxxxxxx> Signed-off-by: Lee, Chun-Yi <jlee@xxxxxxxx> --- crypto/asymmetric_keys/rsa.c | 163 +++++++++++++++++++++++++++++++++++++++++- include/crypto/public_key.h | 2 + 2 files changed, 164 insertions(+), 1 deletions(-) diff --git a/crypto/asymmetric_keys/rsa.c b/crypto/asymmetric_keys/rsa.c index 47f3be4..352ba45 100644 --- a/crypto/asymmetric_keys/rsa.c +++ b/crypto/asymmetric_keys/rsa.c @@ -13,6 +13,7 @@ #include <linux/module.h> #include <linux/kernel.h> #include <linux/slab.h> +#include <crypto/hash.h> #include "public_key.h" #include "private_key.h" @@ -152,6 +153,132 @@ static int RSA_I2OSP(MPI x, size_t xLen, u8 **_X) } /* + * EMSA_PKCS1-v1_5-ENCODE [RFC3447 sec 9.2] + * @M: message to be signed, an octet string + * @emLen: intended length in octets of the encoded message + * @hash_algo: hash function (option) + * @hash: true means hash M, otherwise M is already a digest + * @EM: encoded message, an octet string of length emLen + * + * This function is a implementation of the EMSA-PKCS1-v1_5 encoding operation + * in RSA PKCS#1 spec. It used by the signautre generation operation of + * RSASSA-PKCS1-v1_5 to encode message M to encoded message EM. + * + * The variables used in this function accord PKCS#1 spec but not follow kernel + * naming convention, it useful when look at them with spec. + */ +static int EMSA_PKCS1_v1_5_ENCODE(const u8 *M, size_t emLen, + enum pkey_hash_algo hash_algo, const bool hash, + u8 **EM, struct public_key_signature *pks) +{ + u8 *digest; + struct crypto_shash *tfm; + struct shash_desc *desc; + size_t digest_size, desc_size; + size_t tLen; + u8 *T, *PS, *EM_tmp; + int i, ret; + + pr_info("EMSA_PKCS1_v1_5_ENCODE start\n"); + + if (!RSA_ASN1_templates[hash_algo].data) + ret = -ENOTSUPP; + else + pks->pkey_hash_algo = hash_algo; + + /* 1) Apply the hash function to the message M to produce a hash value H */ + tfm = crypto_alloc_shash(pkey_hash_algo[hash_algo], 0, 0); + if (IS_ERR(tfm)) + return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm); + + desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); + digest_size = crypto_shash_digestsize(tfm); + + ret = -ENOMEM; + + digest = kzalloc(digest_size + desc_size, GFP_KERNEL); + if (!digest) + goto error_digest; + pks->digest = digest; + pks->digest_size = digest_size; + + if (hash) { + desc = (void *) digest + digest_size; + desc->tfm = tfm; + desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP; + + ret = crypto_shash_init(desc); + if (ret < 0) + goto error_shash; + ret = crypto_shash_finup(desc, M, sizeof(M), pks->digest); + if (ret < 0) + goto error_shash; + } else { + memcpy(pks->digest, M, pks->digest_size); + pks->digest_size = digest_size; + } + crypto_free_shash(tfm); + + /* 2) Encode the algorithm ID for the hash function and the hash value into + * an ASN.1 value of type DigestInfo with the DER. Let T be the DER encoding of + * the DigestInfo value and let tLen be the length in octets of T. + */ + tLen = RSA_ASN1_templates[hash_algo].size + pks->digest_size; + T = kmalloc(tLen, GFP_KERNEL); + if (!T) + goto error_T; + + memcpy(T, RSA_ASN1_templates[hash_algo].data, RSA_ASN1_templates[hash_algo].size); + memcpy(T + RSA_ASN1_templates[hash_algo].size, pks->digest, pks->digest_size); + + /* 3) check If emLen < tLen + 11, output "intended encoded message length too short" */ + if (emLen < tLen + 11) { + ret = -EINVAL; + goto error_emLen; + } + + /* 4) Generate an octet string PS consisting of emLen - tLen - 3 octets with 0xff. */ + PS = kmalloc(emLen - tLen - 3, GFP_KERNEL); + if (!PS) + goto error_P; + + for (i = 0; i < (emLen - tLen - 3); i++) + PS[i] = 0xff; + + /* 5) Concatenate PS, the DER encoding T, and other padding to form the encoded + * message EM as EM = 0x00 || 0x01 || PS || 0x00 || T + */ + EM_tmp = kmalloc(3 + emLen - tLen - 3 + tLen, GFP_KERNEL); + if (!EM_tmp) + goto error_EM; + + EM_tmp[0] = 0x00; + EM_tmp[1] = 0x01; + memcpy(EM_tmp + 2, PS, emLen - tLen - 3); + EM_tmp[2 + emLen - tLen - 3] = 0x00; + memcpy(EM_tmp + 2 + emLen - tLen - 3 + 1, T, tLen); + + *EM = EM_tmp; + + kfree(PS); + kfree(T); + + return 0; + +error_EM: + kfree(PS); +error_P: +error_emLen: + kfree(T); +error_T: +error_shash: + kfree(digest); +error_digest: + crypto_free_shash(tfm); + return ret; +} + +/* * Perform the RSA signature verification. * @H: Value of hash of data and metadata * @EM: The computed signature value @@ -275,9 +402,43 @@ static struct public_key_signature *RSA_generate_signature( const struct private_key *key, u8 *M, enum pkey_hash_algo hash_algo, const bool hash) { + struct public_key_signature *pks; + u8 *EM = NULL; + size_t emLen; + int ret; + pr_info("RSA_generate_signature start\n"); - return 0; + ret = -ENOMEM; + pks = kzalloc(sizeof(*pks), GFP_KERNEL); + if (!pks) + goto error_no_pks; + + /* 1): EMSA-PKCS1-v1_5 encoding: */ + /* Use the private key modulus size to be EM length */ + emLen = mpi_get_nbits(key->rsa.n); + emLen = (emLen + 7) / 8; + + ret = EMSA_PKCS1_v1_5_ENCODE(M, emLen, hash_algo, hash, &EM, pks); + if (ret < 0) + goto error_v1_5_encode; + + /* TODO 2): m = OS2IP (EM) */ + + /* TODO 3): s = RSASP1 (K, m) */ + + /* TODO 4): S = I2OSP (s, k) */ + + /* TODO: signature S to a u8* S or set to sig->rsa.s? */ + pks->S = EM; /* TODO: temporary set S to EM */ + + return pks; + +error_v1_5_encode: + kfree(pks); +error_no_pks: + pr_info("<==%s() = %d\n", __func__, ret); + return ERR_PTR(ret); } const struct public_key_algorithm RSA_public_key_algorithm = { diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h index d44b29f..1cdf457 100644 --- a/include/crypto/public_key.h +++ b/include/crypto/public_key.h @@ -110,6 +110,8 @@ extern void public_key_destroy(void *payload); struct public_key_signature { u8 *digest; u8 digest_size; /* Number of bytes in digest */ + u8 *S; /* signature S of length k octets */ + size_t k; /* length k of signature S */ u8 nr_mpi; /* Occupancy of mpi[] */ enum pkey_hash_algo pkey_hash_algo : 8; union { -- 1.6.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
