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-rw-r--r--security/keys/dh.c160
1 files changed, 160 insertions, 0 deletions
diff --git a/security/keys/dh.c b/security/keys/dh.c
new file mode 100644
index 0000000..880505a
--- /dev/null
+++ b/security/keys/dh.c
@@ -0,0 +1,160 @@
+/* Crypto operations using stored keys
+ *
+ * Copyright (c) 2016, Intel Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/mpi.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <keys/user-type.h>
+#include "internal.h"
+
+/*
+ * Public key or shared secret generation function [RFC2631 sec 2.1.1]
+ *
+ * ya = g^xa mod p;
+ * or
+ * ZZ = yb^xa mod p;
+ *
+ * where xa is the local private key, ya is the local public key, g is
+ * the generator, p is the prime, yb is the remote public key, and ZZ
+ * is the shared secret.
+ *
+ * Both are the same calculation, so g or yb are the "base" and ya or
+ * ZZ are the "result".
+ */
+static int do_dh(MPI result, MPI base, MPI xa, MPI p)
+{
+ return mpi_powm(result, base, xa, p);
+}
+
+static ssize_t mpi_from_key(key_serial_t keyid, size_t maxlen, MPI *mpi)
+{
+ struct key *key;
+ key_ref_t key_ref;
+ long status;
+ ssize_t ret;
+
+ key_ref = lookup_user_key(keyid, 0, KEY_NEED_READ);
+ if (IS_ERR(key_ref)) {
+ ret = -ENOKEY;
+ goto error;
+ }
+
+ key = key_ref_to_ptr(key_ref);
+
+ ret = -EOPNOTSUPP;
+ if (key->type == &key_type_user) {
+ down_read(&key->sem);
+ status = key_validate(key);
+ if (status == 0) {
+ const struct user_key_payload *payload;
+
+ payload = user_key_payload(key);
+
+ if (maxlen == 0) {
+ *mpi = NULL;
+ ret = payload->datalen;
+ } else if (payload->datalen <= maxlen) {
+ *mpi = mpi_read_raw_data(payload->data,
+ payload->datalen);
+ if (*mpi)
+ ret = payload->datalen;
+ } else {
+ ret = -EINVAL;
+ }
+ }
+ up_read(&key->sem);
+ }
+
+ key_put(key);
+error:
+ return ret;
+}
+
+long keyctl_dh_compute(struct keyctl_dh_params __user *params,
+ char __user *buffer, size_t buflen)
+{
+ long ret;
+ MPI base, private, prime, result;
+ unsigned nbytes;
+ struct keyctl_dh_params pcopy;
+ uint8_t *kbuf;
+ ssize_t keylen;
+ size_t resultlen;
+
+ if (!params || (!buffer && buflen)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ keylen = mpi_from_key(pcopy.prime, buflen, &prime);
+ if (keylen < 0 || !prime) {
+ /* buflen == 0 may be used to query the required buffer size,
+ * which is the prime key length.
+ */
+ ret = keylen;
+ goto out;
+ }
+
+ /* The result is never longer than the prime */
+ resultlen = keylen;
+
+ keylen = mpi_from_key(pcopy.base, SIZE_MAX, &base);
+ if (keylen < 0 || !base) {
+ ret = keylen;
+ goto error1;
+ }
+
+ keylen = mpi_from_key(pcopy.private, SIZE_MAX, &private);
+ if (keylen < 0 || !private) {
+ ret = keylen;
+ goto error2;
+ }
+
+ result = mpi_alloc(0);
+ if (!result) {
+ ret = -ENOMEM;
+ goto error3;
+ }
+
+ kbuf = kmalloc(resultlen, GFP_KERNEL);
+ if (!kbuf) {
+ ret = -ENOMEM;
+ goto error4;
+ }
+
+ ret = do_dh(result, base, private, prime);
+ if (ret)
+ goto error5;
+
+ ret = mpi_read_buffer(result, kbuf, resultlen, &nbytes, NULL);
+ if (ret != 0)
+ goto error5;
+
+ ret = nbytes;
+ if (copy_to_user(buffer, kbuf, nbytes) != 0)
+ ret = -EFAULT;
+
+error5:
+ kfree(kbuf);
+error4:
+ mpi_free(result);
+error3:
+ mpi_free(private);
+error2:
+ mpi_free(base);
+error1:
+ mpi_free(prime);
+out:
+ return ret;
+}
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