v4.19.13 snapshot.
diff --git a/crypto/dh.c b/crypto/dh.c
new file mode 100644
index 0000000..09a44de
--- /dev/null
+++ b/crypto/dh.c
@@ -0,0 +1,243 @@
+/* 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 License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, 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; /* Value is guaranteed to be set. */
+ MPI q; /* Value is optional. */
+ MPI g; /* Value is guaranteed to be set. */
+ MPI xa; /* Value is guaranteed to be set. */
+};
+
+static void dh_clear_ctx(struct dh_ctx *ctx)
+{
+ mpi_free(ctx->p);
+ mpi_free(ctx->q);
+ mpi_free(ctx->g);
+ mpi_free(ctx->xa);
+ memset(ctx, 0, sizeof(*ctx));
+}
+
+/*
+ * 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 (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;
+
+ if (params->q && params->q_size) {
+ ctx->q = mpi_read_raw_data(params->q, params->q_size);
+ if (!ctx->q)
+ return -EINVAL;
+ }
+
+ ctx->g = mpi_read_raw_data(params->g, params->g_size);
+ if (!ctx->g)
+ return -EINVAL;
+
+ return 0;
+}
+
+static int dh_set_secret(struct crypto_kpp *tfm, const void *buf,
+ unsigned int len)
+{
+ struct dh_ctx *ctx = dh_get_ctx(tfm);
+ struct dh params;
+
+ /* Free the old MPI key if any */
+ dh_clear_ctx(ctx);
+
+ if (crypto_dh_decode_key(buf, len, ¶ms) < 0)
+ goto err_clear_ctx;
+
+ if (dh_set_params(ctx, ¶ms) < 0)
+ goto err_clear_ctx;
+
+ ctx->xa = mpi_read_raw_data(params.key, params.key_size);
+ if (!ctx->xa)
+ goto err_clear_ctx;
+
+ return 0;
+
+err_clear_ctx:
+ dh_clear_ctx(ctx);
+ return -EINVAL;
+}
+
+/*
+ * SP800-56A public key verification:
+ *
+ * * If Q is provided as part of the domain paramenters, a full validation
+ * according to SP800-56A section 5.6.2.3.1 is performed.
+ *
+ * * If Q is not provided, a partial validation according to SP800-56A section
+ * 5.6.2.3.2 is performed.
+ */
+static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y)
+{
+ if (unlikely(!ctx->p))
+ return -EINVAL;
+
+ /*
+ * Step 1: Verify that 2 <= y <= p - 2.
+ *
+ * The upper limit check is actually y < p instead of y < p - 1
+ * as the mpi_sub_ui function is yet missing.
+ */
+ if (mpi_cmp_ui(y, 1) < 1 || mpi_cmp(y, ctx->p) >= 0)
+ return -EINVAL;
+
+ /* Step 2: Verify that 1 = y^q mod p */
+ if (ctx->q) {
+ MPI val = mpi_alloc(0);
+ int ret;
+
+ if (!val)
+ return -ENOMEM;
+
+ ret = mpi_powm(val, y, ctx->q, ctx->p);
+
+ if (ret) {
+ mpi_free(val);
+ return ret;
+ }
+
+ ret = mpi_cmp_ui(val, 1);
+
+ mpi_free(val);
+
+ if (ret != 0)
+ 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;
+ }
+ ret = dh_is_pubkey_valid(ctx, base);
+ if (ret)
+ goto err_free_base;
+ } 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 unsigned 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_clear_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");