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/*
 * Secure Remote Password 6a implementation
 * https://github.com/est31/csrp-gmp
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2010, 2013 Tom Cocagne, 2015 est31 <MTest31@outlook.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is furnished to do
 * so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */

// clang-format off
#ifdef WIN32
	#include <windows.h>
	#include <wincrypt.h>
#else
	#include <time.h>
#endif
// clang-format on

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

#include <config.h>

#if USE_SYSTEM_GMP || defined (__ANDROID__) || defined (ANDROID)
	#include <gmp.h>
#else
	#include <mini-gmp.h>
#endif

#include <util/sha2.h>

#include "srp.h"
//#define CSRP_USE_SHA1
#define CSRP_USE_SHA256

#define srp_dbg_data(data, datalen, prevtext) ;
/*void srp_dbg_data(unsigned char * data, size_t datalen, char * prevtext)
{
	printf(prevtext);
	size_t i;
	for (i = 0; i < datalen; i++)
	{
		printf("%02X", data[i]);
	}
	printf("\n");
}*/

static int g_initialized = 0;

#define RAND_BUFF_MAX 128
static unsigned int g_rand_idx;
static unsigned char g_rand_buff[RAND_BUFF_MAX];

void *(*srp_alloc)(size_t) = &malloc;
void *(*srp_realloc)(void *, size_t) = &realloc;
void (*srp_free)(void *) = &free;

// clang-format off
void srp_set_memory_functions(
		void *(*new_srp_alloc)(size_t),
		void *(*new_srp_realloc)(void *, size_t),
		void (*new_srp_free)(void *))
{
	srp_alloc = new_srp_alloc;
	srp_realloc = new_srp_realloc;
	srp_free = new_srp_free;
}
// clang-format on

typedef struct {
	mpz_t N;
	mpz_t g;
} NGConstant;

struct NGHex {
	const char *n_hex;
	const char *g_hex;
};

/* All constants here were pulled from Appendix A of RFC 5054 */
static struct NGHex global_Ng_constants[] = {
	{/* 1024 */
		"EEAF0AB9ADB38DD69C33F80AFA8FC5E86072618775FF3C0B9EA2314C"
		"9C256576D674DF7496EA81D3383B4813D692C6E0E0D5D8E250B98BE4"
		"8E495C1D6089DAD15DC7D7B46154D6B6CE8EF4AD69B15D4982559B29"
		"7BCF1885C529F566660E57EC68EDBC3C05726CC02FD4CBF4976EAA9A"
		"FD5138FE8376435B9FC61D2FC0EB06E3",
		"2"},
	{/* 2048 */
		"AC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC319294"
		"3DB56050A37329CBB4A099ED8193E0757767A13DD52312AB4B03310D"
		"CD7F48A9DA04FD50E8083969EDB767B0CF6095179A163AB3661A05FB"
		"D5FAAAE82918A9962F0B93B855F97993EC975EEAA80D740ADBF4FF74"
		"7359D041D5C33EA71D281E446B14773BCA97B43A23FB801676BD207A"
		"436C6481F1D2B9078717461A5B9D32E688F87748544523B524B0D57D"
		"5EA77A2775D2ECFA032CFBDBF52FB3786160279004E57AE6AF874E73"
		"03CE53299CCC041C7BC308D82A5698F3A8D0C38271AE35F8E9DBFBB6"
		"94B5C803D89F7AE435DE236D525F54759B65E372FCD68EF20FA7111F"
		"9E4AFF73",
		"2"},
	{/* 4096 */
		"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08"
		"8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B"
		"302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9"
		"A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6"
		"49286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8"
		"FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D"
		"670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C"
		"180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF695581718"
		"3995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D"
		"04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7D"
		"B3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D226"
		"1AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200C"
		"BBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFC"
		"E0FD108E4B82D120A92108011A723C12A787E6D788719A10BDBA5B26"
		"99C327186AF4E23C1A946834B6150BDA2583E9CA2AD44CE8DBBBC2DB"
		"04DE8EF92E8EFC141FBECAA6287C59474E6BC05D99B2964FA090C3A2"
		"233BA186515BE7ED1F612970CEE2D7AFB81BDD762170481CD0069127"
		"D5B05AA993B4EA988D8FDDC186FFB7DC90A6C08F4DF435C934063199"
		"FFFFFFFFFFFFFFFF",
		"5"},
	{/* 8192 */
		"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08"
		"8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B"
		"302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9"
		"A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6"
		"49286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8"
		"FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D"
		"670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C"
		"180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF695581718"
		"3995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D"
		"04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7D"
		"B3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D226"
		"1AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200C"
		"BBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFC"
		"E0FD108E4B82D120A92108011A723C12A787E6D788719A10BDBA5B26"
		"99C327186AF4E23C1A946834B6150BDA2583E9CA2AD44CE8DBBBC2DB"
		"04DE8EF92E8EFC141FBECAA6287C59474E6BC05D99B2964FA090C3A2"
		"233BA186515BE7ED1F612970CEE2D7AFB81BDD762170481CD0069127"
		"D5B05AA993B4EA988D8FDDC186FFB7DC90A6C08F4DF435C934028492"
		"36C3FAB4D27C7026C1D4DCB2602646DEC9751E763DBA37BDF8FF9406"
		"AD9E530EE5DB382F413001AEB06A53ED9027D831179727B0865A8918"
		"DA3EDBEBCF9B14ED44CE6CBACED4BB1BDB7F1447E6CC254B33205151"
		"2BD7AF426FB8F401378CD2BF5983CA01C64B92ECF032EA15D1721D03"
		"F482D7CE6E74FEF6D55E702F46980C82B5A84031900B1C9E59E7C97F"
		"BEC7E8F323A97A7E36CC88BE0F1D45B7FF585AC54BD407B22B4154AA"
		"CC8F6D7EBF48E1D814CC5ED20F8037E0A79715EEF29BE32806A1D58B"
		"B7C5DA76F550AA3D8A1FBFF0EB19CCB1A313D55CDA56C9EC2EF29632"
		"387FE8D76E3C0468043E8F663F4860EE12BF2D5B0B7474D6E694F91E"
		"6DBE115974A3926F12FEE5E438777CB6A932DF8CD8BEC4D073B931BA"
		"3BC832B68D9DD300741FA7BF8AFC47ED2576F6936BA424663AAB639C"
		"5AE4F5683423B4742BF1C978238F16CBE39D652DE3FDB8BEFC848AD9"
		"22222E04A4037C0713EB57A81A23F0C73473FC646CEA306B4BCBC886"
		"2F8385DDFA9D4B7FA2C087E879683303ED5BDD3A062B3CF5B3A278A6"
		"6D2A13F83F44F82DDF310EE074AB6A364597E899A0255DC164F31CC5"
		"0846851DF9AB48195DED7EA1B1D510BD7EE74D73FAF36BC31ECFA268"
		"359046F4EB879F924009438B481C6CD7889A002ED5EE382BC9190DA6"
		"FC026E479558E4475677E9AA9E3050E2765694DFC81F56E880B96E71"
		"60C980DD98EDD3DFFFFFFFFFFFFFFFFF",
		"13"},
	{0, 0} /* null sentinel */
};

static void delete_ng(NGConstant *ng)
{
	if (ng) {
		mpz_clear(ng->N);
		mpz_clear(ng->g);
		srp_free(ng);
	}
}

static NGConstant *new_ng(SRP_NGType ng_type, const char *n_hex, const char *g_hex)
{
	NGConstant *ng = (NGConstant *)srp_alloc(sizeof(NGConstant));

	if (!ng) return 0;

	mpz_init(ng->N);
	mpz_init(ng->g);

	if (ng_type != SRP_NG_CUSTOM) {
		n_hex = global_Ng_constants[ng_type].n_hex;
		g_hex = global_Ng_constants[ng_type].g_hex;
	}

	int rv = 0;
	rv = mpz_set_str(ng->N, n_hex, 16);
	rv = rv | mpz_set_str(ng->g, g_hex, 16);

	if (rv) {
		delete_ng(ng);
		return 0;
	}

	return ng;
}

typedef union {
	SHA_CTX sha;
	SHA256_CTX sha256;
	// SHA512_CTX sha512;
} HashCTX;

struct SRPVerifier {
	SRP_HashAlgorithm hash_alg;
	NGConstant *ng;

	char *username;
	unsigned char *bytes_B;
	int authenticated;

	unsigned char M[SHA512_DIGEST_LENGTH];
	unsigned char H_AMK[SHA512_DIGEST_LENGTH];
	unsigned char session_key[SHA512_DIGEST_LENGTH];
};

struct SRPUser {
	SRP_HashAlgorithm hash_alg;
	NGConstant *ng;

	mpz_t a;
	mpz_t A;
	mpz_t S;

	unsigned char *bytes_A;
	int authenticated;

	char *username;
	char *username_verifier;
	unsigned char *password;
	size_t password_len;

	unsigned char M[SHA512_DIGEST_LENGTH];
	unsigned char H_AMK[SHA512_DIGEST_LENGTH];
	unsigned char session_key[SHA512_DIGEST_LENGTH];
};

// clang-format off
static int hash_init(SRP_HashAlgorithm alg, HashCTX *c)
{
	switch (alg) {
#ifdef CSRP_USE_SHA1
		case SRP_SHA1: return SHA1_Init(&c->sha);
#endif
		/*
		case SRP_SHA224: return SHA224_Init(&c->sha256);
		*/
#ifdef CSRP_USE_SHA256
		case SRP_SHA256: return SHA256_Init(&c->sha256);
#endif
		/*
		case SRP_SHA384: return SHA384_Init(&c->sha512);
		case SRP_SHA512: return SHA512_Init(&c->sha512);
		*/
		default: return -1;
	};
}
static int hash_update( SRP_HashAlgorithm alg, HashCTX *c, const void *data, size_t len )
{
	switch (alg) {
#ifdef CSRP_USE_SHA1
		case SRP_SHA1: return SHA1_Update(&c->sha, data, len);
#endif
		/*
		case SRP_SHA224: return SHA224_Update(&c->sha256, data, len);
		*/
#ifdef CSRP_USE_SHA256
		case SRP_SHA256: return SHA256_Update(&c->sha256, data, len);
#endif
		/*
		case SRP_SHA384: return SHA384_Update(&c->sha512, data, len);
		case SRP_SHA512: return SHA512_Update(&c->sha512, data, len);
		*/
		default: return -1;
	};
}
static int hash_final( SRP_HashAlgorithm alg, HashCTX *c, unsigned char *md )
{
	switch (alg) {
#ifdef CSRP_USE_SHA1
		case SRP_SHA1: return SHA1_Final(md, &c->sha);
#endif
		/*
		case SRP_SHA224: return SHA224_Final(md, &c->sha256);
		*/
#ifdef CSRP_USE_SHA256
		case SRP_SHA256: return SHA256_Final(md, &c->sha256);
#endif
		/*
		case SRP_SHA384: return SHA384_Final(md, &c->sha512);
		case SRP_SHA512: return SHA512_Final(md, &c->sha512);
		*/
		default: return -1;
	};
}
static unsigned char *hash(SRP_HashAlgorithm alg, const unsigned char *d, size_t n, unsigned char *md)
{
	switch (alg) {
#ifdef CSRP_USE_SHA1
		case SRP_SHA1: return SHA1(d, n, md);
#endif
		/*
		case SRP_SHA224: return SHA224( d, n, md );
		*/
#ifdef CSRP_USE_SHA256
		case SRP_SHA256: return SHA256(d, n, md);
#endif
		/*
		case SRP_SHA384: return SHA384( d, n, md );
		case SRP_SHA512: return SHA512( d, n, md );
		*/
		default: return 0;
	};
}
static size_t hash_length(SRP_HashAlgorithm alg)
{
	switch (alg) {
#ifdef CSRP_USE_SHA1
		case SRP_SHA1: return SHA_DIGEST_LENGTH;
#endif
		/*
		case SRP_SHA224: return SHA224_DIGEST_LENGTH;
		*/
#ifdef CSRP_USE_SHA256
		case SRP_SHA256: return SHA256_DIGEST_LENGTH;
#endif
		/*
		case SRP_SHA384: return SHA384_DIGEST_LENGTH;
		case SRP_SHA512: return SHA512_DIGEST_LENGTH;
		*/
		default: return -1;
	};
}
// clang-format on

inline static int mpz_num_bytes(const mpz_t op)
{
	return (mpz_sizeinbase(op, 2) + 7) / 8;
}

inline static void mpz_to_bin(const mpz_t op, unsigned char *to)
{
	mpz_export(to, NULL, 1, 1, 1, 0, op);
}

inline static void mpz_from_bin(const unsigned char *s, size_t len, mpz_t ret)
{
	mpz_import(ret, len, 1, 1, 1, 0, s);
}

// set op to (op1 * op2) mod d, using tmp for the calculation
inline static void mpz_mulm(
	mpz_t op, const mpz_t op1, const mpz_t op2, const mpz_t d, mpz_t tmp)
{
	mpz_mul(tmp, op1, op2);
	mpz_mod(op, tmp, d);
}

// set op to (op1 + op2) mod d, using tmp for the calculation
inline static void mpz_addm(
	mpz_t op, const mpz_t op1, const mpz_t op2, const mpz_t d, mpz_t tmp)
{
	mpz_add(tmp, op1, op2);
	mpz_mod(op, tmp, d);
}

// set op to (op1 - op2) mod d, using tmp for the calculation
inline static void mpz_subm(
	mpz_t op, const mpz_t op1, const mpz_t op2, const mpz_t d, mpz_t tmp)
{
	mpz_sub(tmp, op1, op2);
	mpz_mod(op, tmp, d);
}

static SRP_Result H_nn(
	mpz_t result, SRP_HashAlgorithm alg, const mpz_t N, const mpz_t n1, const mpz_t n2)
{
	unsigned char buff[SHA512_DIGEST_LENGTH];
	size_t len_N = mpz_num_bytes(N);
	size_t len_n1 = mpz_num_bytes(n1);
	size_t len_n2 = mpz_num_bytes(n2);
	size_t nbytes = len_N + len_N;
	unsigned char *bin = (unsigned char *)srp_alloc(nbytes);
	if (!bin) return SRP_ERR;
	if (len_n1 > len_N || len_n2 > len_N) {
		srp_free(bin);
		return SRP_ERR;
	}
	memset(bin, 0, nbytes);
	mpz_to_bin(n1, bin + (len_N - len_n1));
	mpz_to_bin(n2, bin + (len_N + len_N - len_n2));
	hash(alg, bin, nbytes, buff);
	srp_free(bin);
	mpz_from_bin(buff, hash_length(alg), result);
	return SRP_OK;
}

static SRP_Result H_ns(mpz_t result, SRP_HashAlgorithm alg, const unsigned char *n,
	size_t len_n, const unsigned char *bytes, size_t len_bytes)
{
	unsigned char buff[SHA512_DIGEST_LENGTH];
	size_t nbytes = len_n + len_bytes;
	unsigned char *bin = (unsigned char *)srp_alloc(nbytes);
	if (!bin) return SRP_ERR;
	memcpy(bin, n, len_n);
	memcpy(bin + len_n, bytes, len_bytes);
	hash(alg, bin, nbytes, buff);
	srp_free(bin);
	mpz_from_bin(buff, hash_length(alg), result);
	return SRP_OK;
}

static int calculate_x(mpz_t result, SRP_HashAlgorithm alg, const unsigned char *salt,
	size_t salt_len, const char *username, const unsigned char *password,
	size_t password_len)
{
	unsigned char ucp_hash[SHA512_DIGEST_LENGTH];
	HashCTX ctx;
	hash_init(alg, &ctx);

	srp_dbg_data((char *)username, strlen(username), "Username for x: ");
	srp_dbg_data((char *)password, password_len, "Password for x: ");
	hash_update(alg, &ctx, username, strlen(username));
	hash_update(alg, &ctx, ":", 1);
	hash_update(alg, &ctx, password, password_len);

	hash_final(alg, &ctx, ucp_hash);

	return H_ns(result, alg, salt, salt_len, ucp_hash, hash_length(alg));
}

static SRP_Result update_hash_n(SRP_HashAlgorithm alg, HashCTX *ctx, const mpz_t n)
{
	size_t len = mpz_num_bytes(n);
	unsigned char *n_bytes = (unsigned char *)srp_alloc(len);
	if (!n_bytes) return SRP_ERR;
	mpz_to_bin(n, n_bytes);
	hash_update(alg, ctx, n_bytes, len);
	srp_free(n_bytes);
	return SRP_OK;
}

static SRP_Result hash_num(SRP_HashAlgorithm alg, const mpz_t n, unsigned char *dest)
{
	int nbytes = mpz_num_bytes(n);
	unsigned char *bin = (unsigned char *)srp_alloc(nbytes);
	if (!bin) return SRP_ERR;
	mpz_to_bin(n, bin);
	hash(alg, bin, nbytes, dest);
	srp_free(bin);
	return SRP_OK;
}

static SRP_Result calculate_M(SRP_HashAlgorithm alg, NGConstant *ng, unsigned char *dest,
	const char *I, const unsigned char *s_bytes, size_t s_len, const mpz_t A,
	const mpz_t B, const unsigned char *K)
{
	unsigned char H_N[SHA512_DIGEST_LENGTH];
	unsigned char H_g[SHA512_DIGEST_LENGTH];
	unsigned char H_I[SHA512_DIGEST_LENGTH];
	unsigned char H_xor[SHA512_DIGEST_LENGTH];
	HashCTX ctx;