/*------------------------------------------------------------------
 * utils.c - Generic functions used by all the example apps
 *
 * August, 2013
 *
 * Copyright (c) 2013, 2016, 2017 by cisco Systems, Inc.
 * All rights reserved.
 *------------------------------------------------------------------
 */

#include <stdio.h>
#include <stdlib.h>
#include <openssl/x509v3.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <openssl/x509.h>
#include "est_ossl_util.h"

/*
 * Key wrap algorithm optionally used to protect private keys
 */
#define EST_PRIVATE_KEY_ENC EVP_aes_128_cbc()


/*
 * This function can be used to output the OpenSSL
 * error buffer.  This is useful when an OpenSSL
 * API call fails and you'd like to provide some
 * detail to the user regarding the cause of the
 * failure.
 */
void ossl_dump_ssl_errors ()
{
    BIO		*e = NULL;
    BUF_MEM	*bptr = NULL;

    e = BIO_new(BIO_s_mem());
    if (!e) {
	printf("\nBIO_new failed\n");
	return;
    }
    ERR_print_errors(e);
    (void)BIO_flush(e);
    BIO_get_mem_ptr(e, &bptr);
    printf("\nOSSL error: %s\n", bptr->data); 
    BIO_free_all(e);
}

/*
 * Reads a file into an unsigned char array.
 * The array should not be allocated prior to calling this
 * function.  The return value is the size of the file
 * read into the array.
 */
int read_binary_file (char *filename, unsigned char **contents)
{
    FILE *fp;
    int len;

    fp = fopen(filename, "rb");
    if (!fp) {
        printf("\nUnable to open %s for reading\n", filename);
        return -1;
    }

    /*
     * Determine the size of the file
     */
    fseek(fp, 0, SEEK_END);
    len = ftell(fp);
    if (len < 0 ){
        perror("ftell failed - errno");
        fclose(fp);
        return -2;
    }
    if (fseek(fp, 0, SEEK_SET)) {
        perror("fseek failed - errno");
        fclose(fp);
        return -2;
    }

    *contents = malloc(len + 1);
    if (!*contents) {
        printf("\nmalloc fail\n");
        fclose(fp);
        return -2;
    }

    if (1 != fread(*contents, len, 1, fp)) {
        printf("\nfread failed\n");
        fclose(fp);
        return -2;
    }
    
    /*
     * put the terminator at the end of the buffer
     */
    *(*contents+len) = 0x00;
    fclose(fp);
    return (len);
}

/*
 * Generic function to write a binary file from
 * raw data.
 */
void write_binary_file (char *filename, unsigned char *contents, int len) 
{
    FILE *fp;

    fp = fopen(filename, "wb");
    if (!fp) {
	printf("\nUnable to open %s for writing\n", filename);
	return;
    }
    fwrite(contents, sizeof(char), len, fp);
    fclose(fp);
}

/*
 * Simple function to display hex data to stdout
 * This is used for debugging
 */
void dumpbin (unsigned char *buf, int len)
{
    int i;

    fflush(stdout);
    printf("\ndumpbin (%lu bytes):\n", (long unsigned)len);
    for (i = 0; i < len; i++) {
        /*if (buf[i] >= 0xA)*/ printf("%c", buf[i]);
        //if (i%32 == 31) printf("\n");
    }
    printf("\n");
    fflush(stdout);
}

/*
 * Helper functions to load in/generate private keys
 */

unsigned char *BIO_copy_data(BIO *out, int *data_lenp) {
    unsigned char *data, *tdata;
    int data_len;

    data_len = BIO_get_mem_data(out, &tdata);
    data = malloc(data_len+1);
    if (data) {
        memcpy(data, tdata, data_len);
	data[data_len]='\0';  // Make sure it's \0 terminated, in case used as string
	if (data_lenp) {
	    *data_lenp = data_len;
	}
    } else {
        printf("\nmalloc failed\n");
    }
    return data;
}

char *generate_private_RSA_key (int key_size, pem_password_cb *cb)
{
    char *key_data = NULL;

    RSA *rsa = RSA_new();
    if (!rsa) {
        return NULL;
    }
    BIGNUM *bn = BN_new();
    if (!bn) {
        RSA_free(rsa);
        return NULL;
    }

    BN_set_word(bn, 0x10001);
    RSA_generate_key_ex(rsa, key_size, bn, NULL);

    do {
        BIO *out = BIO_new(BIO_s_mem());
        if (!out) {
            break;
        }
        PEM_write_bio_RSAPrivateKey(out, rsa, cb ? EST_PRIVATE_KEY_ENC : NULL, NULL, 0, cb, NULL);
        key_data = (char *)BIO_copy_data(out, NULL);
        BIO_free(out);
        if (key_data && !key_data[0]) {
            // happens if passphrase entered via STDIN does not verify or has less than 4 characters
            free(key_data);
            key_data = NULL;
        }
    } while (cb && !key_data);

    RSA_free(rsa);
    BN_free(bn);
    return (key_data);
}

char *generate_private_EC_key (int curve_nid, pem_password_cb *cb)
{
    EC_KEY *eckey;
    EC_GROUP *group = NULL;
    char *key_data = NULL;
    int asn1_flag = OPENSSL_EC_NAMED_CURVE;
    point_conversion_form_t form = POINT_CONVERSION_UNCOMPRESSED;

    /*
     * Generate an EC key
     */

    eckey = EC_KEY_new();
    if (!eckey) {
        return NULL;
    }

    group = EC_GROUP_new_by_curve_name(curve_nid);
    if (!group) {
        return NULL;
    }
    EC_GROUP_set_asn1_flag(group, asn1_flag);
    EC_GROUP_set_point_conversion_form(group, form);
    EC_KEY_set_group(eckey, group);
    if (!EC_KEY_set_group(eckey, group)) {
        return NULL;
    }
    if (!EC_KEY_generate_key(eckey)) {
        return (NULL);
    }

    do {
        BIO *out = BIO_new(BIO_s_mem());
        if (!out) {
            break;
        }
        PEM_write_bio_ECPKParameters(out, group);
        PEM_write_bio_ECPrivateKey(out, eckey, cb ? EST_PRIVATE_KEY_ENC : NULL, NULL, 0, cb, NULL);
        key_data = (char *)BIO_copy_data(out, NULL);
        BIO_free(out);
        if (key_data && !strstr(key_data, "-----BEGIN EC PRIVATE KEY-----")) {
            // happens if passphrase entered via STDIN does not verify or has less than 4 characters
            free(key_data);
            key_data = NULL;
        }
    } while (cb && !key_data);

    EC_KEY_free(eckey);
    return (key_data);
}

/*
 * Helper function that can be used to write out a private key
 */
char *private_key_to_PEM (const EVP_PKEY* pkey, pem_password_cb *cb) {
    char *pkey_pem = NULL;
    BIO *out = BIO_new(BIO_s_mem());
    if (out) {
        PEM_write_bio_PrivateKey(out, (EVP_PKEY *)pkey, cb ? EST_PRIVATE_KEY_ENC : NULL, NULL, 0, cb, NULL);
    pkey_pem = (char *)BIO_copy_data(out, NULL);
    BIO_free(out);
    }
    return (pkey_pem);
}

/*
 * Helper function to load a private key from a string
 */
EVP_PKEY *load_private_key (const unsigned char *key, int key_len, int format, pem_password_cb *cb)
{
    BIO *in = NULL;
    EVP_PKEY *pkey = NULL;

    if (key == NULL) {
        printf("\nNo key data provided\n");
        return NULL;
    }

    in = BIO_new_mem_buf((unsigned char *)key, key_len);
    if (in == NULL) {
        printf("\nUnable to open the provided key buffer\n");
        return (NULL);
    }

    switch (format) {
    case EST_FORMAT_PEM:
        pkey = PEM_read_bio_PrivateKey(in, NULL, cb, NULL);
        break;
    case EST_FORMAT_DER:
        pkey = d2i_PrivateKey_bio(in, NULL);
        break;
    default:
        printf("\nInvalid key format\n");
        break;
    }
    BIO_free(in);

    return (pkey);
}

/*
 * Helper function to load a private key from a file
 */
EVP_PKEY *read_private_key(const char *key_file, pem_password_cb *cb)
{
    BIO *keyin;
    EVP_PKEY *priv_key;

    /*
     * Read in the private key
     */
    keyin = BIO_new(BIO_s_file());
    if (BIO_read_filename(keyin, key_file) <= 0) {
        printf("\nUnable to read private key file %s\n", key_file);
    return(NULL);
    }
    /*
     * This reads in the private key file, which is expected to be a PEM
     * encoded private key.  If using DER encoding, you would invoke
     * d2i_PrivateKey_bio() instead.
     */
    priv_key = PEM_read_bio_PrivateKey(keyin, NULL, cb, NULL);
    if (priv_key == NULL) {
        printf("\nError while parsing PEM encoded private key from file %s\n", key_file);
    ossl_dump_ssl_errors();
    }
    BIO_free(keyin);

    return (priv_key);
}