/*

 * Copyright 2004-2021 The OpenSSL Project Authors. All Rights Reserved.

 * Copyright (c) 2004, EdelKey Project. All Rights Reserved.

 *

 * Licensed under the OpenSSL license (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 *

 * Originally written by Christophe Renou and Peter Sylvester,

 * for the EdelKey project.

 */

#ifndef OPENSSL_NO_SRP

# include "internal/cryptlib.h"

# include <openssl/sha.h>

# include <openssl/srp.h>

# include <openssl/evp.h>

# include "crypto/bn_srp.h"

/* calculate = SHA1(PAD(x) || PAD(y)) */

static BIGNUM *srp_Calc_xy(const BIGNUM *x, const BIGNUM *y, const BIGNUM *N)

{

    unsigned char digest[SHA_DIGEST_LENGTH];

    unsigned char *tmp = NULL;

    int numN = BN_num_bytes(N);

    BIGNUM *res = NULL;

    if (x != N && BN_ucmp(x, N) >= 0)

        return NULL;

    if (y != N && BN_ucmp(y, N) >= 0)

        return NULL;

    if ((tmp = OPENSSL_malloc(numN * 2)) == NULL)

        goto err;

    if (BN_bn2binpad(x, tmp, numN) < 0

        || BN_bn2binpad(y, tmp + numN, numN) < 0

        || !EVP_Digest(tmp, numN * 2, digest, NULL, EVP_sha1(), NULL))

        goto err;

    res = BN_bin2bn(digest, sizeof(digest), NULL);

 err:

    OPENSSL_free(tmp);

    return res;

}

static BIGNUM *srp_Calc_k(const BIGNUM *N, const BIGNUM *g)

{

    /* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */

    return srp_Calc_xy(N, g, N);

}

BIGNUM *SRP_Calc_u(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N)

{

    /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */

    return srp_Calc_xy(A, B, N);

}

BIGNUM *SRP_Calc_server_key(const BIGNUM *A, const BIGNUM *v, const BIGNUM *u,

                            const BIGNUM *b, const BIGNUM *N)

{

    BIGNUM *tmp = NULL, *S = NULL;

    BN_CTX *bn_ctx;

    if (u == NULL || A == NULL || v == NULL || b == NULL || N == NULL)

        return NULL;

    if ((bn_ctx = BN_CTX_new()) == NULL || (tmp = BN_new()) == NULL)

        goto err;

    /* S = (A*v**u) ** b */

    if (!BN_mod_exp(tmp, v, u, N, bn_ctx))

        goto err;

    if (!BN_mod_mul(tmp, A, tmp, N, bn_ctx))

        goto err;

    S = BN_new();

    if (S != NULL && !BN_mod_exp(S, tmp, b, N, bn_ctx)) {

        BN_free(S);

        S = NULL;

    }

 err:

    BN_CTX_free(bn_ctx);

    BN_clear_free(tmp);

    return S;

}

BIGNUM *SRP_Calc_B(const BIGNUM *b, const BIGNUM *N, const BIGNUM *g,

                   const BIGNUM *v)

{

    BIGNUM *kv = NULL, *gb = NULL;

    BIGNUM *B = NULL, *k = NULL;

    BN_CTX *bn_ctx;

    if (b == NULL || N == NULL || g == NULL || v == NULL ||

        (bn_ctx = BN_CTX_new()) == NULL)

        return NULL;

    if ((kv = BN_new()) == NULL ||

        (gb = BN_new()) == NULL || (B = BN_new()) == NULL)

        goto err;

    /* B = g**b + k*v */

    if (!BN_mod_exp(gb, g, b, N, bn_ctx)

        || (k = srp_Calc_k(N, g)) == NULL

        || !BN_mod_mul(kv, v, k, N, bn_ctx)

        || !BN_mod_add(B, gb, kv, N, bn_ctx)) {

        BN_free(B);

        B = NULL;

    }

 err:

    BN_CTX_free(bn_ctx);

    BN_clear_free(kv);

    BN_clear_free(gb);

    BN_free(k);

    return B;

}

BIGNUM *SRP_Calc_x(const BIGNUM *s, const char *user, const char *pass)

{

    unsigned char dig[SHA_DIGEST_LENGTH];

    EVP_MD_CTX *ctxt;

    unsigned char *cs = NULL;

    BIGNUM *res = NULL;

    if ((s == NULL) || (user == NULL) || (pass == NULL))

        return NULL;

    ctxt = EVP_MD_CTX_new();

    if (ctxt == NULL)

        return NULL;

    if ((cs = OPENSSL_malloc(BN_num_bytes(s))) == NULL)

        goto err;

    if (!EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL)

        || !EVP_DigestUpdate(ctxt, user, strlen(user))

        || !EVP_DigestUpdate(ctxt, ":", 1)

        || !EVP_DigestUpdate(ctxt, pass, strlen(pass))

        || !EVP_DigestFinal_ex(ctxt, dig, NULL)

        || !EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL))

        goto err;

    if (BN_bn2bin(s, cs) < 0)

        goto err;

    if (!EVP_DigestUpdate(ctxt, cs, BN_num_bytes(s)))

        goto err;

    if (!EVP_DigestUpdate(ctxt, dig, sizeof(dig))

        || !EVP_DigestFinal_ex(ctxt, dig, NULL))

        goto err;

    res = BN_bin2bn(dig, sizeof(dig), NULL);

 err:

    OPENSSL_free(cs);

    EVP_MD_CTX_free(ctxt);

    return res;

}

BIGNUM *SRP_Calc_A(const BIGNUM *a, const BIGNUM *N, const BIGNUM *g)

{

    BN_CTX *bn_ctx;

    BIGNUM *A = NULL;

    if (a == NULL || N == NULL || g == NULL || (bn_ctx = BN_CTX_new()) == NULL)

        return NULL;

    if ((A = BN_new()) != NULL && !BN_mod_exp(A, g, a, N, bn_ctx)) {

        BN_free(A);

        A = NULL;

    }

    BN_CTX_free(bn_ctx);

    return A;

}

BIGNUM *SRP_Calc_client_key(const BIGNUM *N, const BIGNUM *B, const BIGNUM *g,

                            const BIGNUM *x, const BIGNUM *a, const BIGNUM *u)

{

    BIGNUM *tmp = NULL, *tmp2 = NULL, *tmp3 = NULL, *k = NULL, *K = NULL;

    BIGNUM *xtmp = NULL;

    BN_CTX *bn_ctx;

    if (u == NULL || B == NULL || N == NULL || g == NULL || x == NULL

        || a == NULL || (bn_ctx = BN_CTX_new()) == NULL)

        return NULL;

    if ((tmp = BN_new()) == NULL ||

        (tmp2 = BN_new()) == NULL ||

        (tmp3 = BN_new()) == NULL ||

        (xtmp = BN_new()) == NULL)

        goto err;

    BN_with_flags(xtmp, x, BN_FLG_CONSTTIME);

    BN_set_flags(tmp, BN_FLG_CONSTTIME);

    if (!BN_mod_exp(tmp, g, xtmp, N, bn_ctx))

        goto err;

    if ((k = srp_Calc_k(N, g)) == NULL)

        goto err;

    if (!BN_mod_mul(tmp2, tmp, k, N, bn_ctx))

        goto err;

    if (!BN_mod_sub(tmp, B, tmp2, N, bn_ctx))

        goto err;

    if (!BN_mul(tmp3, u, xtmp, bn_ctx))

        goto err;

    if (!BN_add(tmp2, a, tmp3))

        goto err;

    K = BN_new();

    if (K != NULL && !BN_mod_exp(K, tmp, tmp2, N, bn_ctx)) {

        BN_free(K);

        K = NULL;

    }

 err:

    BN_CTX_free(bn_ctx);

    BN_free(xtmp);

    BN_clear_free(tmp);

    BN_clear_free(tmp2);

    BN_clear_free(tmp3);

    BN_free(k);

    return K;

}

int SRP_Verify_B_mod_N(const BIGNUM *B, const BIGNUM *N)

{

    BIGNUM *r;

    BN_CTX *bn_ctx;

    int ret = 0;

    if (B == NULL || N == NULL || (bn_ctx = BN_CTX_new()) == NULL)

        return 0;

    if ((r = BN_new()) == NULL)

        goto err;

    /* Checks if B % N == 0 */

    if (!BN_nnmod(r, B, N, bn_ctx))

        goto err;

    ret = !BN_is_zero(r);

 err:

    BN_CTX_free(bn_ctx);

    BN_free(r);

    return ret;

}

int SRP_Verify_A_mod_N(const BIGNUM *A, const BIGNUM *N)

{

    /* Checks if A % N == 0 */

    return SRP_Verify_B_mod_N(A, N);

}

static SRP_gN knowngN[] = {

    {"8192", &bn_generator_19, &bn_group_8192},

    {"6144", &bn_generator_5, &bn_group_6144},

    {"4096", &bn_generator_5, &bn_group_4096},

    {"3072", &bn_generator_5, &bn_group_3072},

    {"2048", &bn_generator_2, &bn_group_2048},

    {"1536", &bn_generator_2, &bn_group_1536},

    {"1024", &bn_generator_2, &bn_group_1024},

};

# define KNOWN_GN_NUMBER sizeof(knowngN) / sizeof(SRP_gN)

/*

 * Check if G and N are known parameters. The values have been generated

 * from the ietf-tls-srp draft version 8

 */

char *SRP_check_known_gN_param(const BIGNUM *g, const BIGNUM *N)

{

    size_t i;

    if ((g == NULL) || (N == NULL))

        return 0;

    for (i = 0; i < KNOWN_GN_NUMBER; i++) {

        if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0)

            return knowngN[i].id;

    }

    return NULL;

}

SRP_gN *SRP_get_default_gN(const char *id)

{

    size_t i;

    if (id == NULL)

        return knowngN;

    for (i = 0; i < KNOWN_GN_NUMBER; i++) {

        if (strcmp(knowngN[i].id, id) == 0)

            return knowngN + i;

    }

    return NULL;

}

#endif