KEYS: asym_tpm: Implement signature verification [ver #2]
This patch implements the verify_signature operation. The public key portion extracted from the TPM key blob is used. The operation is performed entirely in software using the crypto API. Signed-off-by: Denis Kenzior <denkenz@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Marcel Holtmann <marcel@holtmann.org> Reviewed-by: Marcel Holtmann <marcel@holtmann.org> Signed-off-by: James Morris <james.morris@microsoft.com>
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@ -15,6 +15,7 @@
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#include <keys/asymmetric-subtype.h>
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#include <keys/asymmetric-subtype.h>
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#include <keys/trusted.h>
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#include <keys/trusted.h>
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#include <crypto/asym_tpm_subtype.h>
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#include <crypto/asym_tpm_subtype.h>
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#include <crypto/public_key.h>
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#define TPM_ORD_FLUSHSPECIFIC 186
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#define TPM_ORD_FLUSHSPECIFIC 186
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#define TPM_ORD_LOADKEY2 65
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#define TPM_ORD_LOADKEY2 65
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@ -286,12 +287,16 @@ static uint32_t derive_pub_key(const void *pub_key, uint32_t len, uint8_t *buf)
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static int determine_akcipher(const char *encoding, const char *hash_algo,
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static int determine_akcipher(const char *encoding, const char *hash_algo,
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char alg_name[CRYPTO_MAX_ALG_NAME])
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char alg_name[CRYPTO_MAX_ALG_NAME])
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{
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{
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/* TODO: We don't support hashing yet */
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if (hash_algo)
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return -ENOPKG;
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if (strcmp(encoding, "pkcs1") == 0) {
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if (strcmp(encoding, "pkcs1") == 0) {
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strcpy(alg_name, "pkcs1pad(rsa)");
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if (!hash_algo) {
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strcpy(alg_name, "pkcs1pad(rsa)");
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return 0;
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}
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if (snprintf(alg_name, CRYPTO_MAX_ALG_NAME, "pkcs1pad(rsa,%s)",
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hash_algo) >= CRYPTO_MAX_ALG_NAME)
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return -EINVAL;
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return 0;
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return 0;
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}
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}
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@ -342,7 +347,8 @@ static int tpm_key_query(const struct kernel_pkey_params *params,
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info->max_dec_size = tk->key_len / 8;
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info->max_dec_size = tk->key_len / 8;
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info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT |
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info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT |
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KEYCTL_SUPPORTS_DECRYPT;
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KEYCTL_SUPPORTS_DECRYPT |
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KEYCTL_SUPPORTS_VERIFY;
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ret = 0;
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ret = 0;
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error_free_tfm:
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error_free_tfm:
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@ -487,6 +493,93 @@ static int tpm_key_eds_op(struct kernel_pkey_params *params,
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return ret;
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return ret;
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}
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}
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/*
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* Verify a signature using a public key.
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*/
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static int tpm_key_verify_signature(const struct key *key,
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const struct public_key_signature *sig)
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{
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const struct tpm_key *tk = key->payload.data[asym_crypto];
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struct crypto_wait cwait;
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struct crypto_akcipher *tfm;
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struct akcipher_request *req;
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struct scatterlist sig_sg, digest_sg;
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char alg_name[CRYPTO_MAX_ALG_NAME];
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uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
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uint32_t der_pub_key_len;
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void *output;
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unsigned int outlen;
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int ret;
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pr_devel("==>%s()\n", __func__);
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BUG_ON(!tk);
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BUG_ON(!sig);
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BUG_ON(!sig->s);
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if (!sig->digest)
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return -ENOPKG;
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ret = determine_akcipher(sig->encoding, sig->hash_algo, alg_name);
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if (ret < 0)
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return ret;
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tfm = crypto_alloc_akcipher(alg_name, 0, 0);
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if (IS_ERR(tfm))
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return PTR_ERR(tfm);
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der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
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der_pub_key);
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ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
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if (ret < 0)
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goto error_free_tfm;
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ret = -ENOMEM;
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req = akcipher_request_alloc(tfm, GFP_KERNEL);
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if (!req)
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goto error_free_tfm;
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ret = -ENOMEM;
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outlen = crypto_akcipher_maxsize(tfm);
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output = kmalloc(outlen, GFP_KERNEL);
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if (!output)
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goto error_free_req;
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sg_init_one(&sig_sg, sig->s, sig->s_size);
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sg_init_one(&digest_sg, output, outlen);
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akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
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outlen);
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crypto_init_wait(&cwait);
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akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
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CRYPTO_TFM_REQ_MAY_SLEEP,
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crypto_req_done, &cwait);
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/* Perform the verification calculation. This doesn't actually do the
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* verification, but rather calculates the hash expected by the
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* signature and returns that to us.
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*/
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ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
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if (ret)
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goto out_free_output;
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/* Do the actual verification step. */
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if (req->dst_len != sig->digest_size ||
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memcmp(sig->digest, output, sig->digest_size) != 0)
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ret = -EKEYREJECTED;
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out_free_output:
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kfree(output);
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error_free_req:
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akcipher_request_free(req);
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error_free_tfm:
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crypto_free_akcipher(tfm);
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pr_devel("<==%s() = %d\n", __func__, ret);
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if (WARN_ON_ONCE(ret > 0))
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ret = -EINVAL;
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return ret;
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}
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/*
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/*
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* Parse enough information out of TPM_KEY structure:
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* Parse enough information out of TPM_KEY structure:
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* TPM_STRUCT_VER -> 4 bytes
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* TPM_STRUCT_VER -> 4 bytes
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@ -645,6 +738,7 @@ struct asymmetric_key_subtype asym_tpm_subtype = {
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.destroy = asym_tpm_destroy,
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.destroy = asym_tpm_destroy,
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.query = tpm_key_query,
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.query = tpm_key_query,
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.eds_op = tpm_key_eds_op,
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.eds_op = tpm_key_eds_op,
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.verify_signature = tpm_key_verify_signature,
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};
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};
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EXPORT_SYMBOL_GPL(asym_tpm_subtype);
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EXPORT_SYMBOL_GPL(asym_tpm_subtype);
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