/**
 * Copyright (C) 2016 Daniel-Constantin Mierla (asipto.com)
 *
 * This file is part of Kamailio, a free SIP server.
 *
 * This file is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version
 *
 *
 * This file is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

#include "../../sr_module.h"
#include "../../dprint.h"
#include "../../mod_fix.h"
#include "../../pvapi.h"
#include "../../lvalue.h"
#include "../../basex.h"

#include "crypto_uuid.h"

#include <openssl/evp.h>

#define AES_BLOCK_SIZE 256

MODULE_VERSION

int crypto_aes_init(unsigned char *key_data, int key_data_len,
		unsigned char *salt, EVP_CIPHER_CTX *e_ctx, EVP_CIPHER_CTX *d_ctx);
unsigned char *crypto_aes_encrypt(EVP_CIPHER_CTX *e, unsigned char *plaintext,
		int *len);
unsigned char *crypto_aes_decrypt(EVP_CIPHER_CTX *e, unsigned char *ciphertext,
		int *len);

static int  mod_init(void);
static int  child_init(int);
static void mod_destroy(void);

static int w_crypto_aes_encrypt(sip_msg_t* msg, char* inb, char* keyb, char* outb);
static int fixup_crypto_aes_encrypt(void** param, int param_no);
static int w_crypto_aes_decrypt(sip_msg_t* msg, char* inb, char* keyb, char* outb);
static int fixup_crypto_aes_decrypt(void** param, int param_no);

#define CRYPTO_SALT_BSIZE	16
static char _crypto_salt[CRYPTO_SALT_BSIZE];
static char *_crypto_salt_param = "k8hTm4aZ";

static int _crypto_register_callid = 0;

static cmd_export_t cmds[]={
	{"crypto_aes_encrypt", (cmd_function)w_crypto_aes_encrypt, 3,
		fixup_crypto_aes_encrypt, 0, ANY_ROUTE},
	{"crypto_aes_decrypt", (cmd_function)w_crypto_aes_decrypt, 3,
		fixup_crypto_aes_decrypt, 0, ANY_ROUTE},
	{0, 0, 0, 0, 0, 0}
};

static param_export_t params[]={
	{ "salt",            PARAM_STRING, &_crypto_salt_param },
	{ "register_callid", PARAM_INT, &_crypto_register_callid },
	{ 0, 0, 0 }
};

struct module_exports exports = {
	"crypto",
	DEFAULT_DLFLAGS, /* dlopen flags */
	cmds,
	params,
	0,
	0,              /* exported MI functions */
	0,              /* exported pseudo-variables */
	0,              /* extra processes */
	mod_init,       /* module initialization function */
	0,              /* response function */
	mod_destroy,    /* destroy function */
	child_init      /* per child init function */
};


/**
 * @brief Initialize crypto module function
 */
static int mod_init(void)
{
	int i;
	char k;
	memset(_crypto_salt, 0, CRYPTO_SALT_BSIZE*sizeof(char));
	if(_crypto_salt_param==NULL || _crypto_salt_param[0]==0) {
		_crypto_salt_param = NULL;
	} else {
		if(strlen(_crypto_salt_param)<8) {
			LM_ERR("salt parameter must be at least 8 characters\n");
			return -1;
		}
		k = 97;
		for(i=0; i<strlen(_crypto_salt_param); i++) {
			if(i>=CRYPTO_SALT_BSIZE) break;
			_crypto_salt[i] = (_crypto_salt_param[i]*7 + k + k*(i+1))%0xff;
			k = _crypto_salt[i];
		}
	}
	if(_crypto_register_callid!=0) {
		if(crypto_init_callid()<0) {
			LM_ERR("failed to init callid callback\n");
			return -1;
		}
		if(crypto_register_callid_func()<0) {
			LM_ERR("unable to register callid callback\n");
			return -1;
		}
		LM_DBG("registered crypto callid callback\n");
	}
	return 0;
}

/**
 * @brief Initialize crypto module children
 */
static int child_init(int rank)
{
	if(_crypto_register_callid!=0 && crypto_child_init_callid(rank)<0) {
		LM_ERR("failed to register callid callback\n");
		return -1;
	}

	return 0;
}

/**
 * destroy module function
 */
static void mod_destroy(void)
{
	return;
}

/**
 *
 */
static int w_crypto_aes_encrypt(sip_msg_t* msg, char* inb, char* keyb, char* outb)
{
	str ins;
	str keys;
	pv_spec_t *dst;
	pv_value_t val;
	EVP_CIPHER_CTX *en = NULL;
	str etext;

	if (fixup_get_svalue(msg, (gparam_t*)inb, &ins) != 0) {
		LM_ERR("cannot get input value\n");
		return -1;
	}
	if (fixup_get_svalue(msg, (gparam_t*)keyb, &keys) != 0) {
		LM_ERR("cannot get key value\n");
		return -1;
	}
	en = EVP_CIPHER_CTX_new();
	if(en==NULL) {
		LM_ERR("cannot get new cipher context\n");
		return -1;
	}
	dst = (pv_spec_t*)outb;

	/* gen key and iv. init the cipher ctx object */
	if (crypto_aes_init((unsigned char *)keys.s, keys.len,
				(unsigned char*)((_crypto_salt_param)?_crypto_salt:0), en, NULL)) {
		EVP_CIPHER_CTX_free(en);
		LM_ERR("couldn't initialize AES cipher\n");
		return -1;
	}
	etext.len = ins.len;
	etext.s = (char *)crypto_aes_encrypt(en, (unsigned char *)ins.s, &etext.len);
	if(etext.s==NULL) {
		EVP_CIPHER_CTX_free(en);
		LM_ERR("AES encryption failed\n");
		return -1;
	}

	memset(&val, 0, sizeof(pv_value_t));
	val.rs.s = pv_get_buffer();
	val.rs.len = base64_enc((unsigned char *)etext.s, etext.len,
					(unsigned char *)val.rs.s, pv_get_buffer_size()-1);
	if (val.rs.len < 0) {
		EVP_CIPHER_CTX_free(en);
		LM_ERR("base64 output of encrypted value is too large (need %d)\n",
				-val.rs.len);
		goto error;
	}
	LM_DBG("base64 encrypted result: [%.*s]\n", val.rs.len, val.rs.s);
	val.flags = PV_VAL_STR;
	dst->setf(msg, &dst->pvp, (int)EQ_T, &val);

	free(etext.s);
	EVP_CIPHER_CTX_cleanup(en);
	EVP_CIPHER_CTX_free(en);
	return 1;

error:
	free(etext.s);
	EVP_CIPHER_CTX_cleanup(en);
	EVP_CIPHER_CTX_free(en);
	return -1;
}

/**
 *
 */
static int fixup_crypto_aes_encrypt(void** param, int param_no)
{
	if(param_no==1 || param_no==2) {
		if(fixup_spve_null(param, 1)<0)
			return -1;
		return 0;
	} else if(param_no==3) {
		if (fixup_pvar_null(param, 1) != 0) {
			LM_ERR("failed to fixup result pvar\n");
			return -1;
		}
		if (((pv_spec_t *)(*param))->setf == NULL) {
			LM_ERR("result pvar is not writeble\n");
			return -1;
		}
	}
	return 0;
}

/**
 *
 */
static int w_crypto_aes_decrypt(sip_msg_t* msg, char* inb, char* keyb, char* outb)
{
	str ins;
	str keys;
	pv_spec_t *dst;
	pv_value_t val;
	EVP_CIPHER_CTX *de=NULL;
	str etext;

	if (fixup_get_svalue(msg, (gparam_t*)inb, &ins) != 0) {
		LM_ERR("cannot get input value\n");
		return -1;
	}
	if (fixup_get_svalue(msg, (gparam_t*)keyb, &keys) != 0) {
		LM_ERR("cannot get key value\n");
		return -1;
	}
	de = EVP_CIPHER_CTX_new();
	if(de==NULL) {
		LM_ERR("cannot get new cipher context\n");
		return -1;
	}
	dst = (pv_spec_t*)outb;

	/* gen key and iv. init the cipher ctx object */
	if (crypto_aes_init((unsigned char *)keys.s, keys.len,
				(unsigned char*)((_crypto_salt_param)?_crypto_salt:0), NULL, de)) {
		EVP_CIPHER_CTX_free(de);
		LM_ERR("couldn't initialize AES cipher\n");
		return -1;
	}

	memset(&val, 0, sizeof(pv_value_t));
	etext.s = pv_get_buffer();
	etext.len = base64_dec((unsigned char *)ins.s, ins.len,
					(unsigned char *)etext.s, pv_get_buffer_size()-1);
	if (etext.len < 0) {
		EVP_CIPHER_CTX_free(de);
		LM_ERR("base64 inpuy with encrypted value is too large (need %d)\n",
				-etext.len);
		return -1;
	}
	val.rs.len = etext.len;
	val.rs.s = (char *)crypto_aes_decrypt(de, (unsigned char *)etext.s,
			&val.rs.len);
	if(val.rs.s==NULL) {
		EVP_CIPHER_CTX_free(de);
		LM_ERR("AES decryption failed\n");
		return -1;
	}
	LM_DBG("plain result: [%.*s]\n", val.rs.len, val.rs.s);
	val.flags = PV_VAL_STR;
	dst->setf(msg, &dst->pvp, (int)EQ_T, &val);

	free(val.rs.s);
	EVP_CIPHER_CTX_cleanup(de);
	EVP_CIPHER_CTX_free(de);
	return 1;
}

/**
 *
 */
static int fixup_crypto_aes_decrypt(void** param, int param_no)
{
	if(param_no==1 || param_no==2) {
		if(fixup_spve_null(param, 1)<0)
			return -1;
		return 0;
	} else if(param_no==3) {
		if (fixup_pvar_null(param, 1) != 0) {
			LM_ERR("failed to fixup result pvar\n");
			return -1;
		}
		if (((pv_spec_t *)(*param))->setf == NULL) {
			LM_ERR("result pvar is not writeble\n");
			return -1;
		}
	}
	return 0;
}


/**
 * Create an 256 bit key and IV using the supplied key_data and salt.
 * Fills in the encryption and decryption ctx objects and returns 0 on success
 */
int crypto_aes_init(unsigned char *key_data, int key_data_len,
		unsigned char *salt, EVP_CIPHER_CTX *e_ctx, EVP_CIPHER_CTX *d_ctx)
{
	int i, nrounds = 5;
	int x;
	unsigned char key[32], iv[32];

	/*
	 * Gen key & IV for AES 256 CBC mode. A SHA1 digest is used to hash
	 * the supplied key material.
	 * nrounds is the number of times the we hash the material. More rounds
	 * are more secure but slower.
	 */
	i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), salt,
			key_data, key_data_len, nrounds, key, iv);
	if (i != 32) {
		LM_ERR("key size is %d bits - should be 256 bits\n", i);
		return -1;
	}

	for(x = 0; x<32; ++x)
		LM_DBG("key: %x iv: %x \n", key[x], iv[x]);

	for(x = 0; x<8; ++x)
		LM_DBG("salt: %x\n", salt[x]);

	if(e_ctx) {
		EVP_CIPHER_CTX_init(e_ctx);
		EVP_EncryptInit_ex(e_ctx, EVP_aes_256_cbc(), NULL, key, iv);
	}
	if(d_ctx) {
		EVP_CIPHER_CTX_init(d_ctx);
		EVP_DecryptInit_ex(d_ctx, EVP_aes_256_cbc(), NULL, key, iv);
	}

	return 0;
}

/*
 * Encrypt *len bytes of data
 * All data going in & out is considered binary (unsigned char[])
 */
unsigned char *crypto_aes_encrypt(EVP_CIPHER_CTX *e, unsigned char *plaintext,
		int *len)
{
	/* max ciphertext len for a n bytes of plaintext is
	 * n + AES_BLOCK_SIZE -1 bytes */
	int c_len = *len + AES_BLOCK_SIZE - 1, f_len = 0;
	unsigned char *ciphertext = (unsigned char *)malloc(c_len);

	if(ciphertext == NULL) {
		LM_ERR("no more system memory\n");
		return NULL;
	}
	/* allows reusing of 'e' for multiple encryption cycles */
	if(!EVP_EncryptInit_ex(e, NULL, NULL, NULL, NULL)){
		LM_ERR("failure in EVP_EncryptInit_ex \n");
		free(ciphertext);
		return NULL;
	}

	/* update ciphertext, c_len is filled with the length of ciphertext
	 * generated, *len is the size of plaintext in bytes */
	if(!EVP_EncryptUpdate(e, ciphertext, &c_len, plaintext, *len)){
		LM_ERR("failure in EVP_EncryptUpdate \n");
		free(ciphertext);
		return NULL;
	}

	/* update ciphertext with the final remaining bytes */
	if(!EVP_EncryptFinal_ex(e, ciphertext+c_len, &f_len)){
		LM_ERR("failure in EVP_EncryptFinal_ex \n");
		free(ciphertext);
		return NULL;
	}

	*len = c_len + f_len;
	return ciphertext;
}

/*
 * Decrypt *len bytes of ciphertext
 */
unsigned char *crypto_aes_decrypt(EVP_CIPHER_CTX *e, unsigned char *ciphertext,
		int *len)
{
	/* plaintext will always be equal to or lesser than length of ciphertext*/
	int p_len = *len, f_len = 0;
	unsigned char *plaintext = (unsigned char *)malloc(p_len);

	if(plaintext==NULL) {
		LM_ERR("no more system memory\n");
		return NULL;
	}
	if(!EVP_DecryptInit_ex(e, NULL, NULL, NULL, NULL)){
		LM_ERR("failure in EVP_DecryptInit_ex \n");
		free(plaintext);
		return NULL;
	}

	if(!EVP_DecryptUpdate(e, plaintext, &p_len, ciphertext, *len)){
		LM_ERR("failure in EVP_DecryptUpdate\n");
		free(plaintext);
		return NULL;
	}

	if(!EVP_DecryptFinal_ex(e, plaintext+p_len, &f_len)){
		LM_ERR("failure in EVP_DecryptFinal_ex\n");
		free(plaintext);
		return NULL;
	}

	*len = p_len + f_len;
	return plaintext;
}

/**
 * testing function
 */
int crypto_aes_test(void)
{
	/* "opaque" encryption, decryption ctx structures
	 * that libcrypto uses to record status of enc/dec operations */
	EVP_CIPHER_CTX *en = NULL;
	EVP_CIPHER_CTX *de = NULL;


	/* The salt paramter is used as a salt in the derivation:
	 * it should point to an 8 byte buffer or NULL if no salt is used. */
	unsigned char salt[] = {1,2,3,4,5,6,7,8};

	unsigned char *key_data;
	int key_data_len, i;
	char *input[] = {"Kamailio - The Open Source SIP Server",
		"Thank you for flying Kamailio!",
		"100 Trying\nYour call is important to us",
		NULL
	};

	en = EVP_CIPHER_CTX_new();
	if(en==NULL) {
		LM_ERR("cannot get new cipher context\n");
		return -1;
	}
	de = EVP_CIPHER_CTX_new();
	if(de==NULL) {
		EVP_CIPHER_CTX_free(en);
		LM_ERR("cannot get new cipher context\n");
		return -1;
	}
	/* the key_data for testing */
	key_data = (unsigned char *)"kamailio-sip-server";
	key_data_len = strlen((const char *)key_data);

	/* gen key and iv. init the cipher ctx object */
	if (crypto_aes_init(key_data, key_data_len, salt, en, de)) {
		LM_ERR("couldn't initialize AES cipher\n");
		return -1;
	}

	/* encrypt and decrypt each input string and compare with the original */
	for (i = 0; input[i]; i++) {
		char *plaintext;
		unsigned char *ciphertext;
		int olen, len;

		/* The enc/dec functions deal with binary data and not C strings.
		 * strlen() will return length of the string without counting the '\0'
		 * string marker. We always pass in the marker byte to the
		 * encrypt/decrypt functions so that after decryption we end up with
		 * a legal C string */
		olen = len = strlen(input[i])+1;

		ciphertext = crypto_aes_encrypt(en, (unsigned char *)input[i], &len);
		plaintext = (char *)crypto_aes_decrypt(de, ciphertext, &len);

		if (strncmp(plaintext, input[i], olen))
			LM_ERR("FAIL: enc/dec failed for \"%s\"\n", input[i]);
		else
			LM_NOTICE("OK: enc/dec ok for \"%s\"\n", plaintext);

		free(ciphertext);
		free(plaintext);
	}

	EVP_CIPHER_CTX_cleanup(de);
	EVP_CIPHER_CTX_free(de);
	EVP_CIPHER_CTX_cleanup(en);
	EVP_CIPHER_CTX_free(en);

	return 0;
}