0036-rpmb-mux-add-HKDF-for-RPMB-Mux-module.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Qi Yadong <yadong.qi@intel.com>
Date: Thu, 18 Oct 2018 15:41:11 +0800
Subject: [PATCH] rpmb: mux: add HKDF for RPMB Mux module

Implement a HKDF (hash based key derivation function)
for RPMB key derivation.

Change-Id: Ic1a0d270c32d9ba101369ef10065b93f5c7ec479
Signed-off-by: Huang, Yang <yang.huang@intel.com>
Signed-off-by: Wei, Xinghai <xinghaix.wei@intel.com>
Signed-off-by: Qi Yadong <yadong.qi@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
---
 drivers/char/rpmb/mux/Makefile   |   4 +-
 drivers/char/rpmb/mux/mux_hkdf.c | 166 +++++++++++++++++++++++++++++++
 drivers/char/rpmb/mux/mux_hkdf.h |  14 +++
 3 files changed, 183 insertions(+), 1 deletion(-)
 create mode 100644 drivers/char/rpmb/mux/mux_hkdf.c
 create mode 100644 drivers/char/rpmb/mux/mux_hkdf.h

diff --git a/drivers/char/rpmb/mux/Makefile b/drivers/char/rpmb/mux/Makefile
index 7afc458a0dd2..23234a88aa73 100644
--- a/drivers/char/rpmb/mux/Makefile
+++ b/drivers/char/rpmb/mux/Makefile
@@ -1,3 +1,5 @@
-obj-$(CONFIG_RPMB_MUX) += mux.o
+obj-$(CONFIG_RPMB_MUX) += rpmb_mux.o
+rpmb_mux-objs := mux.o
+rpmb_mux-objs += mux_hkdf.o
 
 ccflags-y += -D__CHECK_ENDIAN__
diff --git a/drivers/char/rpmb/mux/mux_hkdf.c b/drivers/char/rpmb/mux/mux_hkdf.c
new file mode 100644
index 000000000000..d4234924148e
--- /dev/null
+++ b/drivers/char/rpmb/mux/mux_hkdf.c
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/*
+ * RPMB Mux HKDF
+ *
+ * Copyright (c) 2018 Intel Corporation. All rights reserved.
+ */
+
+#include <linux/compat.h>
+#include <crypto/hash.h>
+#include "mux_hkdf.h"
+
+static int mux_sha256_extract(u8 *out_key, size_t out_len,
+			      struct shash_desc *desc,
+			      const u8 *secret, size_t secret_len,
+			      const u8 *salt, size_t salt_len)
+{
+	int ret;
+	u8 salt0[SHA256_HASH_SIZE];
+
+	if (!salt || !salt_len) {
+		memset(salt0, 0, sizeof(salt0));
+		salt = salt0;
+		salt_len = sizeof(salt0);
+	}
+
+	ret = crypto_shash_setkey(desc->tfm, salt, salt_len);
+	if (ret) {
+		pr_err("set key failed = %d\n", ret);
+		goto out;
+	}
+
+	ret = crypto_shash_init(desc);
+	if (ret)
+		goto out;
+
+	ret = crypto_shash_update(desc, secret, secret_len);
+	if (ret)
+		goto out;
+
+	ret = crypto_shash_final(desc, out_key);
+	if (ret)
+		goto out;
+
+out:
+	return ret;
+}
+
+static int mux_sha256_expand(u8 *out_key, size_t out_len,
+			     struct shash_desc *desc,
+			     const u8 *prk, size_t prk_len,
+			     const u8 *info, size_t info_len)
+{
+	const size_t digest_len = SHA256_HASH_SIZE;
+	u8 previous[SHA256_HASH_SIZE];
+	size_t n, done = 0;
+	unsigned int i;
+	int ret = 0;
+
+	n = (out_len + digest_len - 1) / digest_len;
+
+	/* check for possible integer overflow */
+	if (out_len + digest_len < out_len)
+		return 0;
+
+	if (n > 255)
+		return 0;
+
+	for (i = 0; i < n; i++) {
+		u8 ctr = i + 1;
+		size_t todo;
+
+		ret = crypto_shash_setkey(desc->tfm, prk, prk_len);
+		if (ret)
+			goto out;
+
+		ret = crypto_shash_init(desc);
+		if (ret)
+			goto out;
+
+		if (i != 0 && crypto_shash_update(desc, previous, digest_len))
+			goto out;
+
+		if (crypto_shash_update(desc, info, info_len) ||
+		    crypto_shash_update(desc, &ctr, 1) ||
+		    crypto_shash_final(desc, previous)) {
+			ret = -EPERM;
+			goto out;
+		}
+
+		todo = digest_len;
+		/* Check if the length of left buffer is smaller than
+		 * 32 to make sure no buffer overflow in below memcpy
+		 */
+		if (done + todo > out_len)
+			todo = out_len - done;
+
+		memcpy(out_key + done, previous, todo);
+		done += todo;
+	}
+
+out:
+	memset(previous, 0, sizeof(previous));
+
+	return ret;
+}
+
+static struct shash_desc *mux_hkdf_init_hmac_sha256_desc(void)
+{
+	struct shash_desc *desc;
+	struct crypto_shash *tfm;
+
+	tfm = crypto_alloc_shash("hmac(sha256)", 0, 0);
+	if (IS_ERR(tfm))
+		return ERR_PTR(-EFAULT);
+
+	desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
+	if (!desc) {
+		crypto_free_shash(tfm);
+		return ERR_PTR(-ENOMEM);
+	}
+	desc->tfm = tfm;
+
+	return desc;
+}
+
+int mux_hkdf_sha256(u8 *out_key, size_t out_len,
+		    const u8 *secret, size_t secret_len,
+		    const u8 *salt, size_t salt_len,
+		    const u8 *info, size_t info_len)
+{
+	u8 prk[SHA256_HASH_SIZE];
+	size_t prk_len = SHA256_HASH_SIZE;
+	int ret;
+	struct shash_desc *desc;
+
+	if (!out_key || !out_len)
+		return -EINVAL;
+
+	if (!secret || !secret_len)
+		return -EINVAL;
+
+	if (!info && info_len)
+		return -EINVAL;
+
+	desc = mux_hkdf_init_hmac_sha256_desc();
+	if (IS_ERR(desc))
+		return PTR_ERR(desc);
+
+	memset(prk, 0, sizeof(prk));
+
+	ret = mux_sha256_extract(prk, prk_len, desc,
+				 secret, secret_len,
+				 salt, salt_len);
+	if (ret)
+		goto err_free_shash;
+
+	ret = mux_sha256_expand(out_key, out_len, desc,
+				prk, prk_len,
+				info, info_len);
+
+err_free_shash:
+	crypto_free_shash(desc->tfm);
+	kfree(desc);
+
+	return ret;
+}
diff --git a/drivers/char/rpmb/mux/mux_hkdf.h b/drivers/char/rpmb/mux/mux_hkdf.h
new file mode 100644
index 000000000000..0055884054c2
--- /dev/null
+++ b/drivers/char/rpmb/mux/mux_hkdf.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 */
+/*
+ * Copyright (C) 2018 Intel Corp. All rights reserved
+ */
+#ifndef _MUX_HKDF_H
+#define _MUX_HKDF_H
+
+#define SHA256_HASH_SIZE 32
+
+int mux_hkdf_sha256(u8 *out_key, size_t out_len,
+		    const u8 *secret, size_t secret_len,
+		    const u8 *salt, size_t salt_len,
+		    const u8 *info, size_t info_len);
+#endif /* !_MUX_HKDF_H */
-- 
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