/*

 * 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 "crypto/evp.h"

# include <openssl/sha.h>

# include <openssl/srp.h>

# include <openssl/evp.h>

# include <openssl/buffer.h>

# include <openssl/rand.h>

# include <openssl/txt_db.h>

# include <openssl/err.h>

# define SRP_RANDOM_SALT_LEN 20

# define MAX_LEN 2500

/*

 * Note that SRP uses its own variant of base 64 encoding. A different base64

 * alphabet is used and no padding '=' characters are added. Instead we pad to

 * the front with 0 bytes and subsequently strip off leading encoded padding.

 * This variant is used for compatibility with other SRP implementations -

 * notably libsrp, but also others. It is also required for backwards

 * compatibility in order to load verifier files from other OpenSSL versions.

 */

/*

 * Convert a base64 string into raw byte array representation.

 * Returns the length of the decoded data, or -1 on error.

 */

static int t_fromb64(unsigned char *a, size_t alen, const char *src)

{

    EVP_ENCODE_CTX *ctx;

    int outl = 0, outl2 = 0;

    size_t size, padsize;

    const unsigned char *pad = (const unsigned char *)"00";

    while (*src == ' ' || *src == '\t' || *src == '\n')

        ++src;

    size = strlen(src);

    padsize = 4 - (size & 3);

    padsize &= 3;

    /* Four bytes in src become three bytes output. */

    if (size > INT_MAX || ((size + padsize) / 4) * 3 > alen)

        return -1;

    ctx = EVP_ENCODE_CTX_new();

    if (ctx == NULL)

        return -1;

    /*

     * This should never occur because 1 byte of data always requires 2 bytes of

     * encoding, i.e.

     *  0 bytes unencoded = 0 bytes encoded

     *  1 byte unencoded  = 2 bytes encoded

     *  2 bytes unencoded = 3 bytes encoded

     *  3 bytes unencoded = 4 bytes encoded

     *  4 bytes unencoded = 6 bytes encoded

     *  etc

     */

    if (padsize == 3) {

        outl = -1;

        goto err;

    }

    /* Valid padsize values are now 0, 1 or 2 */

    EVP_DecodeInit(ctx);

    evp_encode_ctx_set_flags(ctx, EVP_ENCODE_CTX_USE_SRP_ALPHABET);

    /* Add any encoded padding that is required */

    if (padsize != 0

            && EVP_DecodeUpdate(ctx, a, &outl, pad, padsize) < 0) {

        outl = -1;

        goto err;

    }

    if (EVP_DecodeUpdate(ctx, a, &outl2, (const unsigned char *)src, size) < 0) {

        outl = -1;

        goto err;

    }

    outl += outl2;

    EVP_DecodeFinal(ctx, a + outl, &outl2);

    outl += outl2;

    /* Strip off the leading padding */

    if (padsize != 0) {

        if ((int)padsize >= outl) {

            outl = -1;

            goto err;

        }

        /*

         * If we added 1 byte of padding prior to encoding then we have 2 bytes

         * of "real" data which gets spread across 4 encoded bytes like this:

         *   (6 bits pad)(2 bits pad | 4 bits data)(6 bits data)(6 bits data)

         * So 1 byte of pre-encoding padding results in 1 full byte of encoded

         * padding.

         * If we added 2 bytes of padding prior to encoding this gets encoded

         * as:

         *   (6 bits pad)(6 bits pad)(4 bits pad | 2 bits data)(6 bits data)

         * So 2 bytes of pre-encoding padding results in 2 full bytes of encoded

         * padding, i.e. we have to strip the same number of bytes of padding

         * from the encoded data as we added to the pre-encoded data.

         */

        memmove(a, a + padsize, outl - padsize);

        outl -= padsize;

    }

 err:

    EVP_ENCODE_CTX_free(ctx);

    return outl;

}

/*

 * Convert a raw byte string into a null-terminated base64 ASCII string.

 * Returns 1 on success or 0 on error.

 */

static int t_tob64(char *dst, const unsigned char *src, int size)

{

    EVP_ENCODE_CTX *ctx = EVP_ENCODE_CTX_new();

    int outl = 0, outl2 = 0;

    unsigned char pad[2] = {0, 0};

    size_t leadz = 0;

    if (ctx == NULL)

        return 0;

    EVP_EncodeInit(ctx);

    evp_encode_ctx_set_flags(ctx, EVP_ENCODE_CTX_NO_NEWLINES

                                  | EVP_ENCODE_CTX_USE_SRP_ALPHABET);

    /*

     * We pad at the front with zero bytes until the length is a multiple of 3

     * so that EVP_EncodeUpdate/EVP_EncodeFinal does not add any of its own "="

     * padding

     */

    leadz = 3 - (size % 3);

    if (leadz != 3

            && !EVP_EncodeUpdate(ctx, (unsigned char *)dst, &outl, pad,

                                 leadz)) {

        EVP_ENCODE_CTX_free(ctx);

        return 0;

    }

    if (!EVP_EncodeUpdate(ctx, (unsigned char *)dst + outl, &outl2, src,

                          size)) {

        EVP_ENCODE_CTX_free(ctx);

        return 0;

    }

    outl += outl2;

    EVP_EncodeFinal(ctx, (unsigned char *)dst + outl, &outl2);

    outl += outl2;

    /* Strip the encoded padding at the front */

    if (leadz != 3) {

        memmove(dst, dst + leadz, outl - leadz);

        dst[outl - leadz] = '\0';

    }

    EVP_ENCODE_CTX_free(ctx);

    return 1;

}

void SRP_user_pwd_free(SRP_user_pwd *user_pwd)

{

    if (user_pwd == NULL)

        return;

    BN_free(user_pwd->s);

    BN_clear_free(user_pwd->v);

    OPENSSL_free(user_pwd->id);

    OPENSSL_free(user_pwd->info);

    OPENSSL_free(user_pwd);

}

static SRP_user_pwd *SRP_user_pwd_new(void)

{

    SRP_user_pwd *ret;

    if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) {

        /* SRPerr(SRP_F_SRP_USER_PWD_NEW, ERR_R_MALLOC_FAILURE); */ /*ckerr_ignore*/

        return NULL;

    }

    ret->N = NULL;

    ret->g = NULL;

    ret->s = NULL;

    ret->v = NULL;

    ret->id = NULL;

    ret->info = NULL;

    return ret;

}

static void SRP_user_pwd_set_gN(SRP_user_pwd *vinfo, const BIGNUM *g,

                                const BIGNUM *N)

{

    vinfo->N = N;

    vinfo->g = g;

}

static int SRP_user_pwd_set_ids(SRP_user_pwd *vinfo, const char *id,

                                const char *info)

{

    if (id != NULL && NULL == (vinfo->id = OPENSSL_strdup(id)))

        return 0;

    return (info == NULL || NULL != (vinfo->info = OPENSSL_strdup(info)));

}

static int SRP_user_pwd_set_sv(SRP_user_pwd *vinfo, const char *s,

                               const char *v)

{

    unsigned char tmp[MAX_LEN];

    int len;

    vinfo->v = NULL;

    vinfo->s = NULL;

    len = t_fromb64(tmp, sizeof(tmp), v);

    if (len < 0)

        return 0;

    if (NULL == (vinfo->v = BN_bin2bn(tmp, len, NULL)))

        return 0;

    len = t_fromb64(tmp, sizeof(tmp), s);

    if (len < 0)

        goto err;

    vinfo->s = BN_bin2bn(tmp, len, NULL);

    if (vinfo->s == NULL)

        goto err;

    return 1;

 err:

    BN_free(vinfo->v);

    vinfo->v = NULL;

    return 0;

}

static int SRP_user_pwd_set_sv_BN(SRP_user_pwd *vinfo, BIGNUM *s, BIGNUM *v)

{

    vinfo->v = v;

    vinfo->s = s;

    return (vinfo->s != NULL && vinfo->v != NULL);

}

static SRP_user_pwd *srp_user_pwd_dup(SRP_user_pwd *src)

{

    SRP_user_pwd *ret;

    if (src == NULL)

        return NULL;

    if ((ret = SRP_user_pwd_new()) == NULL)

        return NULL;

    SRP_user_pwd_set_gN(ret, src->g, src->N);

    if (!SRP_user_pwd_set_ids(ret, src->id, src->info)

        || !SRP_user_pwd_set_sv_BN(ret, BN_dup(src->s), BN_dup(src->v))) {

            SRP_user_pwd_free(ret);

            return NULL;

    }

    return ret;

}

SRP_VBASE *SRP_VBASE_new(char *seed_key)

{

    SRP_VBASE *vb = OPENSSL_malloc(sizeof(*vb));

    if (vb == NULL)

        return NULL;

    if ((vb->users_pwd = sk_SRP_user_pwd_new_null()) == NULL

        || (vb->gN_cache = sk_SRP_gN_cache_new_null()) == NULL) {

        OPENSSL_free(vb);

        return NULL;

    }

    vb->default_g = NULL;

    vb->default_N = NULL;

    vb->seed_key = NULL;

    if ((seed_key != NULL) && (vb->seed_key = OPENSSL_strdup(seed_key)) == NULL) {

        sk_SRP_user_pwd_free(vb->users_pwd);

        sk_SRP_gN_cache_free(vb->gN_cache);

        OPENSSL_free(vb);

        return NULL;

    }

    return vb;

}

void SRP_VBASE_free(SRP_VBASE *vb)

{

    if (!vb)

        return;

    sk_SRP_user_pwd_pop_free(vb->users_pwd, SRP_user_pwd_free);

    sk_SRP_gN_cache_free(vb->gN_cache);

    OPENSSL_free(vb->seed_key);

    OPENSSL_free(vb);

}

static SRP_gN_cache *SRP_gN_new_init(const char *ch)

{

    unsigned char tmp[MAX_LEN];

    int len;

    SRP_gN_cache *newgN = OPENSSL_malloc(sizeof(*newgN));

    if (newgN == NULL)

        return NULL;

    len = t_fromb64(tmp, sizeof(tmp), ch);

    if (len < 0)

        goto err;

    if ((newgN->b64_bn = OPENSSL_strdup(ch)) == NULL)

        goto err;

    if ((newgN->bn = BN_bin2bn(tmp, len, NULL)))

        return newgN;

    OPENSSL_free(newgN->b64_bn);

 err:

    OPENSSL_free(newgN);

    return NULL;

}

static void SRP_gN_free(SRP_gN_cache *gN_cache)

{

    if (gN_cache == NULL)

        return;

    OPENSSL_free(gN_cache->b64_bn);

    BN_free(gN_cache->bn);

    OPENSSL_free(gN_cache);

}

static SRP_gN *SRP_get_gN_by_id(const char *id, STACK_OF(SRP_gN) *gN_tab)

{

    int i;

    SRP_gN *gN;

    if (gN_tab != NULL)

        for (i = 0; i < sk_SRP_gN_num(gN_tab); i++) {

            gN = sk_SRP_gN_value(gN_tab, i);

            if (gN && (id == NULL || strcmp(gN->id, id) == 0))

                return gN;

        }

    return SRP_get_default_gN(id);

}

static BIGNUM *SRP_gN_place_bn(STACK_OF(SRP_gN_cache) *gN_cache, char *ch)

{

    int i;

    if (gN_cache == NULL)

        return NULL;

    /* search if we have already one... */

    for (i = 0; i < sk_SRP_gN_cache_num(gN_cache); i++) {

        SRP_gN_cache *cache = sk_SRP_gN_cache_value(gN_cache, i);

        if (strcmp(cache->b64_bn, ch) == 0)

            return cache->bn;

    }

    {                           /* it is the first time that we find it */

        SRP_gN_cache *newgN = SRP_gN_new_init(ch);

        if (newgN) {

            if (sk_SRP_gN_cache_insert(gN_cache, newgN, 0) > 0)

                return newgN->bn;

            SRP_gN_free(newgN);

        }

    }

    return NULL;

}

/*

 * this function parses verifier file. Format is:

 * string(index):base64(N):base64(g):0

 * string(username):base64(v):base64(salt):int(index)

 */

int SRP_VBASE_init(SRP_VBASE *vb, char *verifier_file)

{

    int error_code;

    STACK_OF(SRP_gN) *SRP_gN_tab = sk_SRP_gN_new_null();

    char *last_index = NULL;

    int i;

    char **pp;

    SRP_gN *gN = NULL;

    SRP_user_pwd *user_pwd = NULL;

    TXT_DB *tmpdb = NULL;

    BIO *in = BIO_new(BIO_s_file());

    error_code = SRP_ERR_OPEN_FILE;

    if (in == NULL || BIO_read_filename(in, verifier_file) <= 0)

        goto err;

    error_code = SRP_ERR_VBASE_INCOMPLETE_FILE;

    if ((tmpdb = TXT_DB_read(in, DB_NUMBER)) == NULL)

        goto err;

    error_code = SRP_ERR_MEMORY;

    if (vb->seed_key) {

        last_index = SRP_get_default_gN(NULL)->id;

    }

    for (i = 0; i < sk_OPENSSL_PSTRING_num(tmpdb->data); i++) {

        pp = sk_OPENSSL_PSTRING_value(tmpdb->data, i);

        if (pp[DB_srptype][0] == DB_SRP_INDEX) {

            /*

             * we add this couple in the internal Stack

             */

            if ((gN = OPENSSL_malloc(sizeof(*gN))) == NULL)

                goto err;

            if ((gN->id = OPENSSL_strdup(pp[DB_srpid])) == NULL

                || (gN->N = SRP_gN_place_bn(vb->gN_cache, pp[DB_srpverifier]))

                        == NULL

                || (gN->g = SRP_gN_place_bn(vb->gN_cache, pp[DB_srpsalt]))

                        == NULL

                || sk_SRP_gN_insert(SRP_gN_tab, gN, 0) == 0)

                goto err;

            gN = NULL;

            if (vb->seed_key != NULL) {

                last_index = pp[DB_srpid];

            }

        } else if (pp[DB_srptype][0] == DB_SRP_VALID) {

            /* it is a user .... */

            const SRP_gN *lgN;

            if ((lgN = SRP_get_gN_by_id(pp[DB_srpgN], SRP_gN_tab)) != NULL) {

                error_code = SRP_ERR_MEMORY;

                if ((user_pwd = SRP_user_pwd_new()) == NULL)

                    goto err;

                SRP_user_pwd_set_gN(user_pwd, lgN->g, lgN->N);

                if (!SRP_user_pwd_set_ids

                    (user_pwd, pp[DB_srpid], pp[DB_srpinfo]))

                    goto err;

                error_code = SRP_ERR_VBASE_BN_LIB;

                if (!SRP_user_pwd_set_sv

                    (user_pwd, pp[DB_srpsalt], pp[DB_srpverifier]))

                    goto err;

                if (sk_SRP_user_pwd_insert(vb->users_pwd, user_pwd, 0) == 0)

                    goto err;

                user_pwd = NULL; /* abandon responsibility */

            }

        }

    }

    if (last_index != NULL) {

        /* this means that we want to simulate a default user */

        if (((gN = SRP_get_gN_by_id(last_index, SRP_gN_tab)) == NULL)) {

            error_code = SRP_ERR_VBASE_BN_LIB;

            goto err;

        }

        vb->default_g = gN->g;

        vb->default_N = gN->N;

        gN = NULL;

    }

    error_code = SRP_NO_ERROR;

 err:

    /*

     * there may be still some leaks to fix, if this fails, the application

     * terminates most likely

     */

    if (gN != NULL) {

        OPENSSL_free(gN->id);

        OPENSSL_free(gN);

    }

    SRP_user_pwd_free(user_pwd);

    TXT_DB_free(tmpdb);

    BIO_free_all(in);

    sk_SRP_gN_free(SRP_gN_tab);

    return error_code;

}

static SRP_user_pwd *find_user(SRP_VBASE *vb, char *username)

{

    int i;

    SRP_user_pwd *user;

    if (vb == NULL)

        return NULL;

    for (i = 0; i < sk_SRP_user_pwd_num(vb->users_pwd); i++) {

        user = sk_SRP_user_pwd_value(vb->users_pwd, i);

        if (strcmp(user->id, username) == 0)

            return user;

    }

    return NULL;

}

# if OPENSSL_API_COMPAT < 0x10100000L

/*

 * DEPRECATED: use SRP_VBASE_get1_by_user instead.

 * This method ignores the configured seed and fails for an unknown user.

 * Ownership of the returned pointer is not released to the caller.

 * In other words, caller must not free the result.

 */

SRP_user_pwd *SRP_VBASE_get_by_user(SRP_VBASE *vb, char *username)

{

    return find_user(vb, username);

}

# endif

/*

 * Ownership of the returned pointer is released to the caller.

 * In other words, caller must free the result once done.

 */

SRP_user_pwd *SRP_VBASE_get1_by_user(SRP_VBASE *vb, char *username)

{

    SRP_user_pwd *user;

    unsigned char digv[SHA_DIGEST_LENGTH];

    unsigned char digs[SHA_DIGEST_LENGTH];

    EVP_MD_CTX *ctxt = NULL;

    if (vb == NULL)

        return NULL;

    if ((user = find_user(vb, username)) != NULL)

        return srp_user_pwd_dup(user);

    if ((vb->seed_key == NULL) ||

        (vb->default_g == NULL) || (vb->default_N == NULL))

        return NULL;

/* if the user is unknown we set parameters as well if we have a seed_key */

    if ((user = SRP_user_pwd_new()) == NULL)

        return NULL;

    SRP_user_pwd_set_gN(user, vb->default_g, vb->default_N);

    if (!SRP_user_pwd_set_ids(user, username, NULL))

        goto err;

    if (RAND_priv_bytes(digv, SHA_DIGEST_LENGTH) <= 0)

        goto err;

    ctxt = EVP_MD_CTX_new();

    if (ctxt == NULL

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

        || !EVP_DigestUpdate(ctxt, vb->seed_key, strlen(vb->seed_key))

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

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

        goto err;

    EVP_MD_CTX_free(ctxt);

    ctxt = NULL;

    if (SRP_user_pwd_set_sv_BN(user,

                               BN_bin2bn(digs, SHA_DIGEST_LENGTH, NULL),

                               BN_bin2bn(digv, SHA_DIGEST_LENGTH, NULL)))

        return user;

 err:

    EVP_MD_CTX_free(ctxt);

    SRP_user_pwd_free(user);

    return NULL;

}

/*

 * create a verifier (*salt,*verifier,g and N are in base64)

 */

char *SRP_create_verifier(const char *user, const char *pass, char **salt,

                          char **verifier, const char *N, const char *g)

{

    int len;

    char *result = NULL, *vf = NULL;

    const BIGNUM *N_bn = NULL, *g_bn = NULL;

    BIGNUM *N_bn_alloc = NULL, *g_bn_alloc = NULL, *s = NULL, *v = NULL;

    unsigned char tmp[MAX_LEN];

    unsigned char tmp2[MAX_LEN];

    char *defgNid = NULL;

    int vfsize = 0;

    if ((user == NULL) ||

        (pass == NULL) || (salt == NULL) || (verifier == NULL))

        goto err;

    if (N) {

        if ((len = t_fromb64(tmp, sizeof(tmp), N)) <= 0)

            goto err;

        N_bn_alloc = BN_bin2bn(tmp, len, NULL);

        if (N_bn_alloc == NULL)

            goto err;

        N_bn = N_bn_alloc;

        if ((len = t_fromb64(tmp, sizeof(tmp) ,g)) <= 0)

            goto err;

        g_bn_alloc = BN_bin2bn(tmp, len, NULL);

        if (g_bn_alloc == NULL)

            goto err;

        g_bn = g_bn_alloc;

        defgNid = "*";

    } else {

        SRP_gN *gN = SRP_get_gN_by_id(g, NULL);

        if (gN == NULL)

            goto err;

        N_bn = gN->N;

        g_bn = gN->g;

        defgNid = gN->id;

    }

    if (*salt == NULL) {

        if (RAND_bytes(tmp2, SRP_RANDOM_SALT_LEN) <= 0)

            goto err;

        s = BN_bin2bn(tmp2, SRP_RANDOM_SALT_LEN, NULL);

    } else {

        if ((len = t_fromb64(tmp2, sizeof(tmp2), *salt)) <= 0)

            goto err;

        s = BN_bin2bn(tmp2, len, NULL);

    }

    if (s == NULL)

        goto err;

    if (!SRP_create_verifier_BN(user, pass, &s, &v, N_bn, g_bn))

        goto err;

    if (BN_bn2bin(v, tmp) < 0)

        goto err;

    vfsize = BN_num_bytes(v) * 2;

    if (((vf = OPENSSL_malloc(vfsize)) == NULL))

        goto err;

    if (!t_tob64(vf, tmp, BN_num_bytes(v)))

        goto err;

    if (*salt == NULL) {

        char *tmp_salt;

        if ((tmp_salt = OPENSSL_malloc(SRP_RANDOM_SALT_LEN * 2)) == NULL) {

            goto err;

        }

        if (!t_tob64(tmp_salt, tmp2, SRP_RANDOM_SALT_LEN)) {

            OPENSSL_free(tmp_salt);

            goto err;

        }

        *salt = tmp_salt;

    }

    *verifier = vf;

    vf = NULL;

    result = defgNid;

 err:

    BN_free(N_bn_alloc);

    BN_free(g_bn_alloc);

    OPENSSL_clear_free(vf, vfsize);

    BN_clear_free(s);

    BN_clear_free(v);

    return result;

}

/*

 * create a verifier (*salt,*verifier,g and N are BIGNUMs). If *salt != NULL

 * then the provided salt will be used. On successful exit *verifier will point

 * to a newly allocated BIGNUM containing the verifier and (if a salt was not

 * provided) *salt will be populated with a newly allocated BIGNUM containing a

 * random salt.

 * The caller is responsible for freeing the allocated *salt and *verifier

 * BIGNUMS.

 */

int SRP_create_verifier_BN(const char *user, const char *pass, BIGNUM **salt,

                           BIGNUM **verifier, const BIGNUM *N,

                           const BIGNUM *g)

{

    int result = 0;

    BIGNUM *x = NULL;

    BN_CTX *bn_ctx = BN_CTX_new();

    unsigned char tmp2[MAX_LEN];

    BIGNUM *salttmp = NULL, *verif;

    if ((user == NULL) ||

        (pass == NULL) ||

        (salt == NULL) ||

        (verifier == NULL) || (N == NULL) || (g == NULL) || (bn_ctx == NULL))

        goto err;

    if (*salt == NULL) {

        if (RAND_bytes(tmp2, SRP_RANDOM_SALT_LEN) <= 0)

            goto err;

        salttmp = BN_bin2bn(tmp2, SRP_RANDOM_SALT_LEN, NULL);

        if (salttmp == NULL)

            goto err;

    } else {

        salttmp = *salt;

    }

    x = SRP_Calc_x(salttmp, user, pass);

    if (x == NULL)

        goto err;

    verif = BN_new();

    if (verif == NULL)

        goto err;

    if (!BN_mod_exp(verif, g, x, N, bn_ctx)) {

        BN_clear_free(verif);

        goto err;

    }

    result = 1;

    *salt = salttmp;

    *verifier = verif;

 err:

    if (salt != NULL && *salt != salttmp)

        BN_clear_free(salttmp);

    BN_clear_free(x);

    BN_CTX_free(bn_ctx);

    return result;

}

#endif