161 lines
3.2 KiB
C
161 lines
3.2 KiB
C
/* Crypto operations using stored keys
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*
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* Copyright (c) 2016, Intel Corporation
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/mpi.h>
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#include <linux/slab.h>
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#include <linux/uaccess.h>
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#include <keys/user-type.h>
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#include "internal.h"
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/*
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* Public key or shared secret generation function [RFC2631 sec 2.1.1]
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*
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* ya = g^xa mod p;
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* or
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* ZZ = yb^xa mod p;
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*
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* where xa is the local private key, ya is the local public key, g is
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* the generator, p is the prime, yb is the remote public key, and ZZ
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* is the shared secret.
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*
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* Both are the same calculation, so g or yb are the "base" and ya or
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* ZZ are the "result".
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*/
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static int do_dh(MPI result, MPI base, MPI xa, MPI p)
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{
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return mpi_powm(result, base, xa, p);
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}
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static ssize_t mpi_from_key(key_serial_t keyid, size_t maxlen, MPI *mpi)
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{
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struct key *key;
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key_ref_t key_ref;
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long status;
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ssize_t ret;
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key_ref = lookup_user_key(keyid, 0, KEY_NEED_READ);
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if (IS_ERR(key_ref)) {
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ret = -ENOKEY;
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goto error;
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}
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key = key_ref_to_ptr(key_ref);
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ret = -EOPNOTSUPP;
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if (key->type == &key_type_user) {
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down_read(&key->sem);
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status = key_validate(key);
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if (status == 0) {
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const struct user_key_payload *payload;
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payload = user_key_payload(key);
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if (maxlen == 0) {
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*mpi = NULL;
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ret = payload->datalen;
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} else if (payload->datalen <= maxlen) {
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*mpi = mpi_read_raw_data(payload->data,
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payload->datalen);
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if (*mpi)
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ret = payload->datalen;
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} else {
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ret = -EINVAL;
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}
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}
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up_read(&key->sem);
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}
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key_put(key);
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error:
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return ret;
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}
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long keyctl_dh_compute(struct keyctl_dh_params __user *params,
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char __user *buffer, size_t buflen)
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{
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long ret;
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MPI base, private, prime, result;
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unsigned nbytes;
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struct keyctl_dh_params pcopy;
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uint8_t *kbuf;
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ssize_t keylen;
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size_t resultlen;
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if (!params || (!buffer && buflen)) {
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ret = -EINVAL;
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goto out;
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}
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if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
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ret = -EFAULT;
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goto out;
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}
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keylen = mpi_from_key(pcopy.prime, buflen, &prime);
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if (keylen < 0 || !prime) {
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/* buflen == 0 may be used to query the required buffer size,
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* which is the prime key length.
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*/
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ret = keylen;
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goto out;
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}
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/* The result is never longer than the prime */
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resultlen = keylen;
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keylen = mpi_from_key(pcopy.base, SIZE_MAX, &base);
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if (keylen < 0 || !base) {
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ret = keylen;
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goto error1;
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}
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keylen = mpi_from_key(pcopy.private, SIZE_MAX, &private);
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if (keylen < 0 || !private) {
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ret = keylen;
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goto error2;
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}
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result = mpi_alloc(0);
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if (!result) {
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ret = -ENOMEM;
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goto error3;
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}
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kbuf = kmalloc(resultlen, GFP_KERNEL);
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if (!kbuf) {
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ret = -ENOMEM;
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goto error4;
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}
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ret = do_dh(result, base, private, prime);
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if (ret)
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goto error5;
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ret = mpi_read_buffer(result, kbuf, resultlen, &nbytes, NULL);
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if (ret != 0)
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goto error5;
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ret = nbytes;
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if (copy_to_user(buffer, kbuf, nbytes) != 0)
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ret = -EFAULT;
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error5:
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kfree(kbuf);
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error4:
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mpi_free(result);
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error3:
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mpi_free(private);
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error2:
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mpi_free(base);
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error1:
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mpi_free(prime);
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out:
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return ret;
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}
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