crypto: dh - Add DH software implementation

* Implement MPI based Diffie-Hellman under kpp API
 * Test provided uses data generad by OpenSSL

Signed-off-by: Salvatore Benedetto <salvatore.benedetto@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 95 insertions, 0 deletions

diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c
new file mode 100644
index 000000000000..02db76b20d00
--- /dev/null
+++ b/crypto/dh_helper.c
@@ -0,0 +1,95 @@
+/*
+ * 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/kernel.h>
+#include <linux/export.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <crypto/dh.h>
+#include <crypto/kpp.h>
+
+#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
+
+static inline u8 *dh_pack_data(void *dst, const void *src, size_t size)
+{
+        memcpy(dst, src, size);
+        return dst + size;
+}
+
+static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
+{
+        memcpy(dst, src, size);
+        return src + size;
+}
+
+static inline int dh_data_size(const struct dh *p)
+{
+        return p->key_size + p->p_size + p->g_size;
+}
+
+int crypto_dh_key_len(const struct dh *p)
+{
+        return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
+}
+EXPORT_SYMBOL_GPL(crypto_dh_key_len);
+
+int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
+{
+        u8 *ptr = buf;
+        struct kpp_secret secret = {
+                .type = CRYPTO_KPP_SECRET_TYPE_DH,
+                .len = len
+        };
+
+        if (unlikely(!buf))
+                return -EINVAL;
+
+        if (len != crypto_dh_key_len(params))
+                return -EINVAL;
+
+        ptr = dh_pack_data(ptr, &secret, sizeof(secret));
+        ptr = dh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
+        ptr = dh_pack_data(ptr, &params->p_size, sizeof(params->p_size));
+        ptr = dh_pack_data(ptr, &params->g_size, sizeof(params->g_size));
+        ptr = dh_pack_data(ptr, params->key, params->key_size);
+        ptr = dh_pack_data(ptr, params->p, params->p_size);
+        dh_pack_data(ptr, params->g, params->g_size);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
+
+int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
+{
+        const u8 *ptr = buf;
+        struct kpp_secret secret;
+
+        if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
+                return -EINVAL;
+
+        ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
+        if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
+                return -EINVAL;
+
+        ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
+        ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
+        ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
+        if (secret.len != crypto_dh_key_len(params))
+                return -EINVAL;
+
+        /* Don't allocate memory. Set pointers to data within
+         * the given buffer
+         */
+        params->key = (void *)ptr;
+        params->p = (void *)(ptr + params->key_size);
+        params->g = (void *)(ptr + params->key_size + params->p_size);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_dh_decode_key);