Import initial code for the SM2 cipher

This adds the SM2 algorithm defined in the Chinese standards
GB/T 32918.1-2016, GB/T 32918.2-2016, GB/T 32918.3-2016,
GB/T 32918.4-2016 and GB/T 32918.5-2017.

This is an ISC licensed implementation contributed by Ribose.inc, based
on the same code that was contributed to OpenSSL by Jack Lloyd. The port
to LibreSSL was done by Ronald Tse and Nickolay Olshevsky.

Github PR #105

I made quite a few cleanup passes on this, but more is needed, some
of which will happen in-tree before this is linked to the build.

ok deraadt inoguchi (a long time ago), jsing

src/lib/libcrypto/sm2/sm2.h

@@ -0,0 +1,147 @@
+/*	$OpenBSD: sm2.h,v 1.1.1.1 2021/08/18 16:04:32 tb Exp $ */
+/*
+ * Copyright (c) 2017, 2019 Ribose Inc
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef HEADER_SM2_H
+#define HEADER_SM2_H
+
+#include <openssl/opensslconf.h>
+
+#include <openssl/ec.h>
+#include <openssl/ecdsa.h>
+
+#ifdef OPENSSL_NO_SM2
+#error SM2 is disabled.
+#endif
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+
+/*
+ * SM2 signature generation.
+ */
+int SM2_sign(const unsigned char *dgst, int dgstlen, unsigned char *sig,
+    unsigned int *siglen, EC_KEY *eckey);
+
+/*
+ * SM2 signature verification. Assumes input is an SM3 digest
+ */
+int SM2_verify(const unsigned char *dgst, int dgstlen, const unsigned char *sig,
+    int siglen, EC_KEY *eckey);
+
+/*
+ * SM2 encryption
+ */
+int SM2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest, size_t msg_len,
+    size_t *c_size);
+
+int SM2_plaintext_size(const EC_KEY *key, const EVP_MD *digest, size_t msg_len,
+    size_t *pl_size);
+
+int SM2_encrypt(const EC_KEY *key, const EVP_MD *digest, const uint8_t *msg,
+    size_t msg_len, uint8_t *ciphertext_buf, size_t *ciphertext_len);
+
+int SM2_decrypt(const EC_KEY *key, const EVP_MD *digest,
+    const uint8_t *ciphertext, size_t ciphertext_len, uint8_t *ptext_buf,
+    size_t *ptext_len);
+
+/* BEGIN ERROR CODES */
+/* The following lines are auto generated by the script mkerr.pl. Any changes
+ * made after this point may be overwritten when the script is next run.
+ */
+void ERR_load_SM2_strings(void);
+
+/* Error codes for the SM2 functions. */
+
+/* Function codes. */
+# define SM2_F_PKEY_SM2_CTRL                              274
+# define SM2_F_PKEY_SM2_CTRL_STR                          275
+# define SM2_F_PKEY_SM2_KEYGEN                            276
+# define SM2_F_PKEY_SM2_PARAMGEN                          277
+# define SM2_F_PKEY_SM2_SIGN                              278
+# define SM2_F_PKEY_SM2_VERIFY                            279
+# define SM2_F_PKEY_SM2_ENCRYPT                           280
+# define SM2_F_PKEY_SM2_DECRYPT                           281
+
+/* Reason codes. */
+# define SM2_R_ASN1_ERROR                                 115
+# define SM2_R_ASN5_ERROR                                 1150
+# define SM2_R_BAD_SIGNATURE                              156
+# define SM2_R_BIGNUM_OUT_OF_RANGE                        144
+# define SM2_R_BUFFER_TOO_SMALL                           100
+# define SM2_R_COORDINATES_OUT_OF_RANGE                   146
+# define SM2_R_CURVE_DOES_NOT_SUPPORT_ECDH                160
+# define SM2_R_CURVE_DOES_NOT_SUPPORT_SIGNING             159
+# define SM2_R_D2I_ECPKPARAMETERS_FAILURE                 117
+# define SM2_R_DECODE_ERROR                               142
+# define SM2_R_DIGEST_FAILURE                             163
+# define SM2_R_DISCRIMINANT_IS_ZERO                       118
+# define SM2_R_EC_GROUP_NEW_BY_NAME_FAILURE               119
+# define SM2_R_FIELD_TOO_LARGE                            143
+# define SM2_R_GF2M_NOT_SUPPORTED                         147
+# define SM2_R_GROUP2PKPARAMETERS_FAILURE                 120
+# define SM2_R_I2D_ECPKPARAMETERS_FAILURE                 121
+# define SM2_R_INCOMPATIBLE_OBJECTS                       101
+# define SM2_R_INVALID_ARGUMENT                           112
+# define SM2_R_INVALID_COMPRESSED_POINT                   110
+# define SM2_R_INVALID_COMPRESSION_BIT                    109
+# define SM2_R_INVALID_CURVE                              141
+# define SM2_R_INVALID_DIGEST                             151
+# define SM2_R_INVALID_DIGEST_TYPE                        138
+# define SM2_R_INVALID_ENCODING                           102
+# define SM2_R_INVALID_FIELD                              103
+# define SM2_R_INVALID_FORM                               104
+# define SM2_R_INVALID_GROUP_ORDER                        122
+# define SM2_R_INVALID_KEY                                116
+# define SM2_R_INVALID_OUTPUT_LENGTH                      161
+# define SM2_R_INVALID_PEER_KEY                           133
+# define SM2_R_INVALID_PENTANOMIAL_BASIS                  132
+# define SM2_R_INVALID_PRIVATE_KEY                        123
+# define SM2_R_INVALID_TRINOMIAL_BASIS                    137
+# define SM2_R_KDF_FAILURE                                162
+# define SM2_R_KDF_PARAMETER_ERROR                        148
+# define SM2_R_KEYS_NOT_SET                               140
+# define SM2_R_MISSING_PARAMETERS                         124
+# define SM2_R_MISSING_PRIVATE_KEY                        125
+# define SM2_R_NEED_NEW_SETUP_VALUES                      157
+# define SM2_R_NOT_A_NIST_PRIME                           135
+# define SM2_R_NOT_IMPLEMENTED                            126
+# define SM2_R_NOT_INITIALIZED                            111
+# define SM2_R_NO_PARAMETERS_SET                          139
+# define SM2_R_NO_PRIVATE_VALUE                           154
+# define SM2_R_OPERATION_NOT_SUPPORTED                    152
+# define SM2_R_PASSED_NULL_PARAMETER                      134
+# define SM2_R_PEER_KEY_ERROR                             149
+# define SM2_R_PKPARAMETERS2GROUP_FAILURE                 127
+# define SM2_R_POINT_ARITHMETIC_FAILURE                   155
+# define SM2_R_POINT_AT_INFINITY                          106
+# define SM2_R_POINT_IS_NOT_ON_CURVE                      107
+# define SM2_R_RANDOM_NUMBER_GENERATION_FAILED            158
+# define SM2_R_SHARED_INFO_ERROR                          150
+# define SM2_R_SLOT_FULL                                  108
+# define SM2_R_UNDEFINED_GENERATOR                        113
+# define SM2_R_UNDEFINED_ORDER                            128
+# define SM2_R_UNKNOWN_GROUP                              129
+# define SM2_R_UNKNOWN_ORDER                              114
+# define SM2_R_UNSUPPORTED_FIELD                          131
+# define SM2_R_WRONG_CURVE_PARAMETERS                     145
+# define SM2_R_WRONG_ORDER                                130
+
+#ifdef  __cplusplus
+}
+#endif
+#endif