/*

 * Copyright 2025 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (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

 */

#include <stdlib.h>

#include <stdarg.h>

#include <string.h>

#include <openssl/evp.h>

#include <openssl/kdf.h>

#include <openssl/sha.h>

#include <openssl/core_names.h>

#include <openssl/proverr.h>

#include "internal/cryptlib.h"

#include "internal/fips.h"

#include "internal/numbers.h"

#include "crypto/evp.h"

#include "prov/provider_ctx.h"

#include "prov/providercommon.h"

#include "prov/implementations.h"

#include "prov/provider_util.h"

#include "providers/implementations/kdfs/snmpkdf.inc"

#define KDF_SNMP_PASSWORD_HASH_AMOUNT (1024 * 1024)

#define KDF_SNMP_MIN_PASSWORD_LEN 8

/* See RFC 3414, Appendix A.2.2 */

/* See NIST SP800-135 Section 6.8 */

static OSSL_FUNC_kdf_newctx_fn kdf_snmpkdf_new;

static OSSL_FUNC_kdf_dupctx_fn kdf_snmpkdf_dup;

static OSSL_FUNC_kdf_freectx_fn kdf_snmpkdf_free;

static OSSL_FUNC_kdf_reset_fn kdf_snmpkdf_reset;

static OSSL_FUNC_kdf_derive_fn kdf_snmpkdf_derive;

static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_snmpkdf_settable_ctx_params;

static OSSL_FUNC_kdf_set_ctx_params_fn kdf_snmpkdf_set_ctx_params;

static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_snmpkdf_gettable_ctx_params;

static OSSL_FUNC_kdf_get_ctx_params_fn kdf_snmpkdf_get_ctx_params;

static int SNMPKDF(const EVP_MD *evp_md,

    const unsigned char *eid, size_t eid_len,

    unsigned char *password, size_t password_len,

    unsigned char *key, size_t keylen);

typedef struct {

    /* Warning: Any changes to this structure may require you to update kdf_snmpkdf_dup */

    void *provctx;

    PROV_DIGEST digest;

    unsigned char *eid;

    size_t eid_len;

    unsigned char *password;

    size_t password_len;

} KDF_SNMPKDF;

static void *kdf_snmpkdf_new(void *provctx)

{

    KDF_SNMPKDF *ctx;

    if (!ossl_prov_is_running())

        return NULL;

#ifdef FIPS_MODULE

    if (!ossl_deferred_self_test(PROV_LIBCTX_OF(provctx),

            ST_ID_KDF_SNMPKDF))

        return NULL;

#endif

    if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) != NULL)

        ctx->provctx = provctx;

    return ctx;

}

static void *kdf_snmpkdf_dup(void *vctx)

{

    const KDF_SNMPKDF *src = (const KDF_SNMPKDF *)vctx;

    KDF_SNMPKDF *dest;

    dest = kdf_snmpkdf_new(src->provctx);

    if (dest != NULL) {

        if (!ossl_prov_memdup(src->eid, src->eid_len,

                &dest->eid, &dest->eid_len)

            || !ossl_prov_memdup(src->password, src->password_len,

                &dest->password, &dest->password_len)

            || !ossl_prov_digest_copy(&dest->digest, &src->digest))

            goto err;

    }

    return dest;

err:

    kdf_snmpkdf_free(dest);

    return NULL;

}

static void kdf_snmpkdf_free(void *vctx)

{

    KDF_SNMPKDF *ctx = (KDF_SNMPKDF *)vctx;

    if (ctx != NULL) {

        kdf_snmpkdf_reset(ctx);

        OPENSSL_free(ctx);

    }

}

static void kdf_snmpkdf_reset(void *vctx)

{

    KDF_SNMPKDF *ctx = (KDF_SNMPKDF *)vctx;

    void *provctx = ctx->provctx;

    ossl_prov_digest_reset(&ctx->digest);

    OPENSSL_clear_free(ctx->eid, ctx->eid_len);

    OPENSSL_clear_free(ctx->password, ctx->password_len);

    memset(ctx, 0, sizeof(*ctx));

    ctx->provctx = provctx;

}

static int snmpkdf_set_membuf(unsigned char **dst, size_t *dst_len,

    const OSSL_PARAM *p)

{

    OPENSSL_clear_free(*dst, *dst_len);

    *dst = NULL;

    *dst_len = 0;

    return OSSL_PARAM_get_octet_string(p, (void **)dst, 0, dst_len);

}

static int kdf_snmpkdf_derive(void *vctx, unsigned char *key, size_t keylen,

    const OSSL_PARAM params[])

{

    KDF_SNMPKDF *ctx = (KDF_SNMPKDF *)vctx;

    const EVP_MD *md;

    if (!ossl_prov_is_running() || !kdf_snmpkdf_set_ctx_params(ctx, params))

        return 0;

    md = ossl_prov_digest_md(&ctx->digest);

    if (md == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);

        return 0;

    }

    if (ctx->eid == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_EID);

        return 0;

    }

    if (ctx->password == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_PASS);

        return 0;

    }

    return SNMPKDF(md, ctx->eid, ctx->eid_len,

        ctx->password, ctx->password_len,

        key, keylen);

}

static int kdf_snmpkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])

{

    struct snmp_set_ctx_params_st p;

    KDF_SNMPKDF *ctx = vctx;

    OSSL_LIB_CTX *libctx;

#ifdef FIPS_MODULE

    const EVP_MD *md = NULL;

#endif

    if (params == NULL)

        return 1;

    if (ctx == NULL || !snmp_set_ctx_params_decoder(params, &p))

        return 0;

    libctx = PROV_LIBCTX_OF(ctx->provctx);

    if (p.digest != NULL) {

        if (!ossl_prov_digest_load(&ctx->digest, p.digest, p.propq, libctx))

            return 0;

#ifdef FIPS_MODULE

        md = ossl_prov_digest_md(&ctx->digest);

        if (!EVP_MD_is_a(md, SN_sha1))

            return 0;

#endif

    }

    if (p.pw != NULL) {

        if (!snmpkdf_set_membuf(&ctx->password, &ctx->password_len, p.pw))

            return 0;

        if ((ctx->password_len > KDF_SNMP_PASSWORD_HASH_AMOUNT) || (ctx->password_len < KDF_SNMP_MIN_PASSWORD_LEN))

            return 0;

    }

    if (p.eid != NULL && !snmpkdf_set_membuf(&ctx->eid, &ctx->eid_len, p.eid))

        return 0;

    return 1;

}

static const OSSL_PARAM *kdf_snmpkdf_settable_ctx_params(ossl_unused void *ctx,

    ossl_unused void *p_ctx)

{

    return snmp_set_ctx_params_list;

}

static size_t kdf_snmpkdf_size(KDF_SNMPKDF *ctx)

{

    int len;

    const EVP_MD *md = NULL;

    md = ossl_prov_digest_md(&ctx->digest);

    if (md == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);

        return 0;

    }

    len = EVP_MD_get_size(md);

    return (len <= 0) ? 0 : (size_t)len;

}

static int kdf_snmpkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])

{

    struct snmp_get_ctx_params_st p;

    KDF_SNMPKDF *ctx = vctx;

    if (ctx == NULL || !snmp_get_ctx_params_decoder(params, &p))

        return 0;

    if (p.size != NULL) {

        size_t sz = kdf_snmpkdf_size(ctx);

        if (sz == 0)

            return 0;

        if (!OSSL_PARAM_set_size_t(p.size, sz))

            return 0;

    }

    return 1;

}

static const OSSL_PARAM *kdf_snmpkdf_gettable_ctx_params(ossl_unused void *ctx,

    ossl_unused void *p_ctx)

{

    return snmp_get_ctx_params_list;

}

const OSSL_DISPATCH ossl_kdf_snmpkdf_functions[] = {

    { OSSL_FUNC_KDF_NEWCTX, (void (*)(void))kdf_snmpkdf_new },

    { OSSL_FUNC_KDF_DUPCTX, (void (*)(void))kdf_snmpkdf_dup },

    { OSSL_FUNC_KDF_FREECTX, (void (*)(void))kdf_snmpkdf_free },

    { OSSL_FUNC_KDF_RESET, (void (*)(void))kdf_snmpkdf_reset },

    { OSSL_FUNC_KDF_DERIVE, (void (*)(void))kdf_snmpkdf_derive },

    { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,

        (void (*)(void))kdf_snmpkdf_settable_ctx_params },

    { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void (*)(void))kdf_snmpkdf_set_ctx_params },

    { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,

        (void (*)(void))kdf_snmpkdf_gettable_ctx_params },

    { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void (*)(void))kdf_snmpkdf_get_ctx_params },

    { 0, NULL }

};

/*

 * SNMPKDF - In compliance with SP800-135 and RFC7860, calculate

 *           a master key using the engine ID and password.

 *

 * Denote engineLength and passwordlen to be the lengths (in bytes) of an

 * snmpEngineID and a password, respectively.

 *

 * Let N = (1024*1024)/passwordlen

 *

 * Expanded_password = the leftmost 1048576 bytes of the string of N

 * repetitions of the password.

 *

 * Derived_password = SHA-1 (Expanded_password). The Derived_password

 * is the output of hashing the Expanded_password by SHA-1.

 *

 * Let Shared_key to be the key that the user shares with the authoritative

 * SNMP engine with ID snmpEngineID. The Shared_key is generated as follows:

 *

 * Shared_key = SHA-1(Derived_password || snmpEngineID || Derived_password).

 *

 * Input:

 *     e_id -         engine ID(eid)

 *     e_len -        engineID length

 *     password -     password

 *     password_len - password length

 *     okey -         pointer to key output, FIPS testing limited to SHA-1.

 *     keylen -       key length

 * Output:

 *     okey   - filled with derived key

 *     return - 1 on pass, 0 fail

 */

static int SNMPKDF(const EVP_MD *evp_md,

    const unsigned char *e_id, size_t e_len,

    unsigned char *password, size_t password_len,

    unsigned char *okey, size_t keylen)

{

    EVP_MD_CTX *md = NULL;

    unsigned char digest[EVP_MAX_MD_SIZE];

    size_t mdsize = 0, len = 0;

    unsigned int md_len = 0;

    int ret = 0;

    /* Limited to SHA-1 and SHA-2 hashes presently */

    if (okey == NULL || keylen == 0)

        return 0;

    md = EVP_MD_CTX_new();

    if (md == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);

        goto err;

    }

    mdsize = EVP_MD_get_size(evp_md);

    if (mdsize <= 0 || mdsize > keylen)

        goto err;

    if (!EVP_DigestInit_ex(md, evp_md, NULL))

        goto err;

    for (len = 0; len < KDF_SNMP_PASSWORD_HASH_AMOUNT - password_len; len += password_len) {

        if (!EVP_DigestUpdate(md, password, password_len))

            goto err;

    }

    if (!EVP_DigestUpdate(md, password, KDF_SNMP_PASSWORD_HASH_AMOUNT - len)

        || !EVP_DigestFinal_ex(md, digest, &md_len)

        || !EVP_DigestInit_ex(md, evp_md, NULL)

        || !EVP_DigestUpdate(md, digest, mdsize)

        || !EVP_DigestUpdate(md, e_id, e_len)

        || !EVP_DigestUpdate(md, digest, mdsize)

        || !EVP_DigestFinal_ex(md, digest, &md_len))

        goto err;

    memcpy(okey, digest, md_len);

    ret = 1;

err:

    EVP_MD_CTX_free(md);

    OPENSSL_cleanse(digest, EVP_MAX_MD_SIZE);

    return ret;

}