/*
 * Copyright 2021 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <libcr51sign/libcr51sign_support.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/rsa.h>
#include <stdio.h>
#include <string.h>

#ifdef __cplusplus
extern "C"
{
#endif

#ifndef USER_PRINT
#define CPRINTS(ctx, ...) fprintf(stderr, __VA_ARGS__)
#endif

// @func hash_init get ready to compute a hash
//
// @param[in] ctx - context struct
// @param[in] hash_type - type of hash function to use
//
// @return nonzero on error, zero on success

int hash_init(const void* ctx, enum hash_type type)
{
    struct libcr51sign_ctx* context = (struct libcr51sign_ctx*)ctx;
    struct hash_ctx* hash_context = (struct hash_ctx*)context->priv;
    hash_context->hash_type = type;
    if (type == HASH_SHA2_256) // SHA256_Init returns 1
        SHA256_Init(&hash_context->sha256_ctx);
    else if (type == HASH_SHA2_512)
        SHA512_Init(&hash_context->sha512_ctx);
    else
        return LIBCR51SIGN_ERROR_INVALID_HASH_TYPE;

    return LIBCR51SIGN_SUCCESS;
}

// @func hash_update add data to the hash
//
// @param[in] ctx - context struct
// @param[in] buf - data to add to hash
// @param[in] count - number of bytes of data to add
//
// @return nonzero on error, zero on success

int hash_update(void* ctx, const uint8_t* data, size_t size)
{
    if (size == 0)
        return LIBCR51SIGN_SUCCESS;
    struct libcr51sign_ctx* context = (struct libcr51sign_ctx*)ctx;
    struct hash_ctx* hash_context = (struct hash_ctx*)context->priv;

    if (hash_context->hash_type == HASH_SHA2_256) // SHA256_Update returns 1
        SHA256_Update(&hash_context->sha256_ctx, data, size);
    else if (hash_context->hash_type == HASH_SHA2_512)
        SHA512_Update(&hash_context->sha512_ctx, data, size);
    else
        return LIBCR51SIGN_ERROR_INVALID_HASH_TYPE;

    return LIBCR51SIGN_SUCCESS;
}

// @func hash_final finish hash calculation
//
// @param[in] ctx - context struct
// @param[out] hash - buffer to write hash to (guaranteed to be big enough)
//
// @return nonzero on error, zero on success

int hash_final(void* ctx, uint8_t* hash)
{
    int rv;
    struct libcr51sign_ctx* context = (struct libcr51sign_ctx*)ctx;
    struct hash_ctx* hash_context = (struct hash_ctx*)context->priv;

    if (hash_context->hash_type == HASH_SHA2_256)
        rv = SHA256_Final(hash, &hash_context->sha256_ctx);
    else if (hash_context->hash_type == HASH_SHA2_512)
        rv = SHA512_Final(hash, &hash_context->sha512_ctx);
    else
        return LIBCR51SIGN_ERROR_INVALID_HASH_TYPE;

    if (rv)
        return LIBCR51SIGN_SUCCESS;
    else
        return LIBCR51SIGN_ERROR_RUNTIME_FAILURE;
}

// @func verify check that the signature is valid for given hashed data
//
// @param[in] ctx - context struct
// @param[in] scheme - type of signature, hash, etc.
// @param[in] sig - signature blob
// @param[in] sig_len - length of signature in bytes
// @param[in] data - pre-hashed data to verify
// @param[in] data_len - length of hashed data in bytes
//
// verify_signature expects RSA public key file path in ctx->key_ring
// @return nonzero on error, zero on success

int verify_signature(const void* ctx, enum signature_scheme sig_scheme,
                     const uint8_t* sig, size_t sig_len, const uint8_t* data,
                     size_t data_len)
{
    // By default returns error.
    int rv = LIBCR51SIGN_ERROR_INVALID_ARGUMENT;

    CPRINTS(ctx, "sig_len %zu sig: ", sig_len);
    for (size_t i = 0; i < sig_len; i++)
    {
        CPRINTS(ctx, "%x", sig[i]);
    }
    CPRINTS(ctx, "\n");

    struct libcr51sign_ctx* lctx = (struct libcr51sign_ctx*)ctx;
    FILE* fp = fopen(lctx->keyring, "r");
    RSA *rsa = NULL, *pub_rsa = NULL;
    EVP_PKEY* pkey = NULL;
    BIO* bio = BIO_new(BIO_s_mem());
    if (!fp)
    {
        CPRINTS(ctx, "fopen failed\n");
        goto clean_up;
    }

    pkey = PEM_read_PUBKEY(fp, 0, 0, 0);
    if (!pkey)
    {
        CPRINTS(ctx, "Read public key failed\n");
        goto clean_up;
    }

    rsa = EVP_PKEY_get1_RSA(pkey);
    if (!rsa)
    {
        goto clean_up;
    }
    pub_rsa = RSAPublicKey_dup(rsa);
    if (!RSA_print(bio, pub_rsa, 2))
    {
        CPRINTS(ctx, "RSA print failed\n");
    }
    if (!pub_rsa)
    {
        CPRINTS(ctx, "no pub RSA\n");
        goto clean_up;
    }
    CPRINTS(ctx, "public RSA\n");
    char buffer[1024] = {};
    while (BIO_read(bio, buffer, sizeof(buffer) - 1) > 0)
    {
        CPRINTS(ctx, " %s", buffer);
    }
    enum hash_type hash_type;
    rv = get_hash_type_from_signature(sig_scheme, &hash_type);
    if (rv != LIBCR51SIGN_SUCCESS)
    {
        CPRINTS(ctx, "Invalid hash_type!\n");
        goto clean_up;
    }
    int hash_nid = -1;
    if (hash_type == HASH_SHA2_256)
    {
        hash_nid = NID_sha256;
    }
    else if (hash_type == HASH_SHA2_512)
    {
        hash_nid = NID_sha512;
    }
    else
    {
        rv = LIBCR51SIGN_ERROR_INVALID_HASH_TYPE;
        goto clean_up;
    }

    int ret = RSA_verify(hash_nid, data, data_len, sig, sig_len, pub_rsa);
    // OpenSSL RSA_verify returns 1 on success and 0 on failure
    if (!ret)
    {
        CPRINTS(ctx, "OPENSSL_ERROR: %s\n",
                ERR_error_string(ERR_get_error(), NULL));
        rv = LIBCR51SIGN_ERROR_RUNTIME_FAILURE;
        goto clean_up;
    }
    rv = LIBCR51SIGN_SUCCESS;
    CPRINTS(ctx, "sig: ");
    for (size_t i = 0; i < sig_len; i++)
    {
        CPRINTS(ctx, "%x", sig[i]);
    }
    CPRINTS(ctx, "\n");

    CPRINTS(ctx, "data: ");
    for (size_t i = 0; i < data_len; i++)
    {
        CPRINTS(ctx, "%x", data[i]);
    }
    CPRINTS(ctx, "\n");

    const unsigned rsa_size = RSA_size(pub_rsa);
    CPRINTS(ctx, "rsa size %d sig_len %d\n", rsa_size, (uint32_t)sig_len);

clean_up:
    if (fp)
    {
        fclose(fp);
    }
    EVP_PKEY_free(pkey);
    RSA_free(rsa);
    RSA_free(pub_rsa);
    BIO_free(bio);
    return rv;
}

#ifdef __cplusplus
} //  extern "C"
#endif