crypto: ecdh - Add ECDH software support
* Implement ECDH under kpp API
* Provide ECC software support for curve P-192 and
P-256.
* Add kpp test for ECDH with data generated by OpenSSL
Signed-off-by: Salvatore Benedetto <salvatore.benedetto@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/ecdh.c b/crypto/ecdh.c
new file mode 100644
index 0000000..d3a9eec
--- /dev/null
+++ b/crypto/ecdh.c
@@ -0,0 +1,151 @@
+/* ECDH key-agreement protocol
+ *
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvator Benedetto <salvatore.benedetto@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <crypto/internal/kpp.h>
+#include <crypto/kpp.h>
+#include <crypto/ecdh.h>
+#include <linux/scatterlist.h>
+#include "ecc.h"
+
+struct ecdh_ctx {
+ unsigned int curve_id;
+ unsigned int ndigits;
+ u64 private_key[ECC_MAX_DIGITS];
+ u64 public_key[2 * ECC_MAX_DIGITS];
+ u64 shared_secret[ECC_MAX_DIGITS];
+};
+
+static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm)
+{
+ return kpp_tfm_ctx(tfm);
+}
+
+static unsigned int ecdh_supported_curve(unsigned int curve_id)
+{
+ switch (curve_id) {
+ case ECC_CURVE_NIST_P192: return 3;
+ case ECC_CURVE_NIST_P256: return 4;
+ default: return 0;
+ }
+}
+
+static int ecdh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
+{
+ struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
+ struct ecdh params;
+ unsigned int ndigits;
+
+ if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0)
+ return -EINVAL;
+
+ ndigits = ecdh_supported_curve(params.curve_id);
+ if (!ndigits)
+ return -EINVAL;
+
+ ctx->curve_id = params.curve_id;
+ ctx->ndigits = ndigits;
+
+ if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
+ (const u8 *)params.key, params.key_size) < 0)
+ return -EINVAL;
+
+ memcpy(ctx->private_key, params.key, params.key_size);
+
+ return 0;
+}
+
+static int ecdh_compute_value(struct kpp_request *req)
+{
+ int ret = 0;
+ struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
+ struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
+ size_t copied, nbytes;
+ void *buf;
+
+ nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
+
+ if (req->src) {
+ copied = sg_copy_to_buffer(req->src, 1, ctx->public_key,
+ 2 * nbytes);
+ if (copied != 2 * nbytes)
+ return -EINVAL;
+
+ ret = ecdh_shared_secret(ctx->curve_id, ctx->ndigits,
+ (const u8 *)ctx->private_key, nbytes,
+ (const u8 *)ctx->public_key, 2 * nbytes,
+ (u8 *)ctx->shared_secret, nbytes);
+
+ buf = ctx->shared_secret;
+ } else {
+ ret = ecdh_make_pub_key(ctx->curve_id, ctx->ndigits,
+ (const u8 *)ctx->private_key, nbytes,
+ (u8 *)ctx->public_key,
+ sizeof(ctx->public_key));
+ buf = ctx->public_key;
+ /* Public part is a point thus it has both coordinates */
+ nbytes *= 2;
+ }
+
+ if (ret < 0)
+ return ret;
+
+ copied = sg_copy_from_buffer(req->dst, 1, buf, nbytes);
+ if (copied != nbytes)
+ return -EINVAL;
+
+ return ret;
+}
+
+static int ecdh_max_size(struct crypto_kpp *tfm)
+{
+ struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
+ int nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
+
+ /* Public key is made of two coordinates */
+ return 2 * nbytes;
+}
+
+static void no_exit_tfm(struct crypto_kpp *tfm)
+{
+ return;
+}
+
+static struct kpp_alg ecdh = {
+ .set_secret = ecdh_set_secret,
+ .generate_public_key = ecdh_compute_value,
+ .compute_shared_secret = ecdh_compute_value,
+ .max_size = ecdh_max_size,
+ .exit = no_exit_tfm,
+ .base = {
+ .cra_name = "ecdh",
+ .cra_driver_name = "ecdh-generic",
+ .cra_priority = 100,
+ .cra_module = THIS_MODULE,
+ .cra_ctxsize = sizeof(struct ecdh_ctx),
+ },
+};
+
+static int ecdh_init(void)
+{
+ return crypto_register_kpp(&ecdh);
+}
+
+static void ecdh_exit(void)
+{
+ crypto_unregister_kpp(&ecdh);
+}
+
+module_init(ecdh_init);
+module_exit(ecdh_exit);
+MODULE_ALIAS_CRYPTO("ecdh");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("ECDH generic algorithm");