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-rw-r--r--crypto/dh.c189
1 files changed, 189 insertions, 0 deletions
diff --git a/crypto/dh.c b/crypto/dh.c
new file mode 100644
index 000000000000..9d19360e7189
--- /dev/null
+++ b/crypto/dh.c
@@ -0,0 +1,189 @@
+/* Diffie-Hellman Key Agreement Method [RFC2631]
+ *
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvatore 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/dh.h>
+#include <linux/mpi.h>
+
+struct dh_ctx {
+ MPI p;
+ MPI g;
+ MPI xa;
+};
+
+static inline void dh_clear_params(struct dh_ctx *ctx)
+{
+ mpi_free(ctx->p);
+ mpi_free(ctx->g);
+ ctx->p = NULL;
+ ctx->g = NULL;
+}
+
+static void dh_free_ctx(struct dh_ctx *ctx)
+{
+ dh_clear_params(ctx);
+ mpi_free(ctx->xa);
+ ctx->xa = NULL;
+}
+
+/*
+ * If base is g we compute the public key
+ * ya = g^xa mod p; [RFC2631 sec 2.1.1]
+ * else if base if the counterpart public key we compute the shared secret
+ * ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
+ */
+static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
+{
+ /* val = base^xa mod p */
+ return mpi_powm(val, base, ctx->xa, ctx->p);
+}
+
+static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
+{
+ return kpp_tfm_ctx(tfm);
+}
+
+static int dh_check_params_length(unsigned int p_len)
+{
+ return (p_len < 1536) ? -EINVAL : 0;
+}
+
+static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
+{
+ if (unlikely(!params->p || !params->g))
+ return -EINVAL;
+
+ if (dh_check_params_length(params->p_size << 3))
+ return -EINVAL;
+
+ ctx->p = mpi_read_raw_data(params->p, params->p_size);
+ if (!ctx->p)
+ return -EINVAL;
+
+ ctx->g = mpi_read_raw_data(params->g, params->g_size);
+ if (!ctx->g) {
+ mpi_free(ctx->p);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
+{
+ struct dh_ctx *ctx = dh_get_ctx(tfm);
+ struct dh params;
+
+ if (crypto_dh_decode_key(buf, len, &params) < 0)
+ return -EINVAL;
+
+ if (dh_set_params(ctx, &params) < 0)
+ return -EINVAL;
+
+ ctx->xa = mpi_read_raw_data(params.key, params.key_size);
+ if (!ctx->xa) {
+ dh_clear_params(ctx);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int dh_compute_value(struct kpp_request *req)
+{
+ struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
+ struct dh_ctx *ctx = dh_get_ctx(tfm);
+ MPI base, val = mpi_alloc(0);
+ int ret = 0;
+ int sign;
+
+ if (!val)
+ return -ENOMEM;
+
+ if (unlikely(!ctx->xa)) {
+ ret = -EINVAL;
+ goto err_free_val;
+ }
+
+ if (req->src) {
+ base = mpi_read_raw_from_sgl(req->src, req->src_len);
+ if (!base) {
+ ret = EINVAL;
+ goto err_free_val;
+ }
+ } else {
+ base = ctx->g;
+ }
+
+ ret = _compute_val(ctx, base, val);
+ if (ret)
+ goto err_free_base;
+
+ ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
+ if (ret)
+ goto err_free_base;
+
+ if (sign < 0)
+ ret = -EBADMSG;
+err_free_base:
+ if (req->src)
+ mpi_free(base);
+err_free_val:
+ mpi_free(val);
+ return ret;
+}
+
+static int dh_max_size(struct crypto_kpp *tfm)
+{
+ struct dh_ctx *ctx = dh_get_ctx(tfm);
+
+ return mpi_get_size(ctx->p);
+}
+
+static void dh_exit_tfm(struct crypto_kpp *tfm)
+{
+ struct dh_ctx *ctx = dh_get_ctx(tfm);
+
+ dh_free_ctx(ctx);
+}
+
+static struct kpp_alg dh = {
+ .set_secret = dh_set_secret,
+ .generate_public_key = dh_compute_value,
+ .compute_shared_secret = dh_compute_value,
+ .max_size = dh_max_size,
+ .exit = dh_exit_tfm,
+ .base = {
+ .cra_name = "dh",
+ .cra_driver_name = "dh-generic",
+ .cra_priority = 100,
+ .cra_module = THIS_MODULE,
+ .cra_ctxsize = sizeof(struct dh_ctx),
+ },
+};
+
+static int dh_init(void)
+{
+ return crypto_register_kpp(&dh);
+}
+
+static void dh_exit(void)
+{
+ crypto_unregister_kpp(&dh);
+}
+
+module_init(dh_init);
+module_exit(dh_exit);
+MODULE_ALIAS_CRYPTO("dh");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("DH generic algorithm");