lib: crypto: add rsa public key parser

Imported from linux kernel v5.3:
rsapubkey.asn1 without changes
rsa.h without changes
rsa_helper.c with changes marked as __UBOOT__

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>

include/crypto/internal/rsa.h

@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * RSA internal helpers
+ *
+ * Copyright (c) 2015, Intel Corporation
+ * Authors: Tadeusz Struk <tadeusz.struk@intel.com>
+ */
+#ifndef _RSA_HELPER_
+#define _RSA_HELPER_
+#include <linux/types.h>
+
+/**
+ * rsa_key - RSA key structure
+ * @n           : RSA modulus raw byte stream
+ * @e           : RSA public exponent raw byte stream
+ * @d           : RSA private exponent raw byte stream
+ * @p           : RSA prime factor p of n raw byte stream
+ * @q           : RSA prime factor q of n raw byte stream
+ * @dp          : RSA exponent d mod (p - 1) raw byte stream
+ * @dq          : RSA exponent d mod (q - 1) raw byte stream
+ * @qinv        : RSA CRT coefficient q^(-1) mod p raw byte stream
+ * @n_sz        : length in bytes of RSA modulus n
+ * @e_sz        : length in bytes of RSA public exponent
+ * @d_sz        : length in bytes of RSA private exponent
+ * @p_sz        : length in bytes of p field
+ * @q_sz        : length in bytes of q field
+ * @dp_sz       : length in bytes of dp field
+ * @dq_sz       : length in bytes of dq field
+ * @qinv_sz     : length in bytes of qinv field
+ */
+struct rsa_key {
+	const u8 *n;
+	const u8 *e;
+	const u8 *d;
+	const u8 *p;
+	const u8 *q;
+	const u8 *dp;
+	const u8 *dq;
+	const u8 *qinv;
+	size_t n_sz;
+	size_t e_sz;
+	size_t d_sz;
+	size_t p_sz;
+	size_t q_sz;
+	size_t dp_sz;
+	size_t dq_sz;
+	size_t qinv_sz;
+};
+
+int rsa_parse_pub_key(struct rsa_key *rsa_key, const void *key,
+		      unsigned int key_len);
+
+int rsa_parse_priv_key(struct rsa_key *rsa_key, const void *key,
+		       unsigned int key_len);
+
+extern struct crypto_template rsa_pkcs1pad_tmpl;
+#endif