providers/implementations/kdfs/sskdf.c - third_party/openssl - Git at Google

 /*
  * Copyright 2019-2022 The OpenSSL Project Authors. All Rights Reserved.
  * Copyright (c) 2019, Oracle and/or its affiliates.  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
  */

 /*
  * Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
  * Section 4.1.
  *
  * The Single Step KDF algorithm is given by:
  *
  * Result(0) = empty bit string (i.e., the null string).
  * For i = 1 to reps, do the following:
  *   Increment counter by 1.
  *   Result(i) = Result(i - 1) || H(counter || Z || FixedInfo).
  * DKM = LeftmostBits(Result(reps), L))
  *
  * NOTES:
  *   Z is a shared secret required to produce the derived key material.
  *   counter is a 4 byte buffer.
  *   FixedInfo is a bit string containing context specific data.
  *   DKM is the output derived key material.
  *   L is the required size of the DKM.
  *   reps = [L / H_outputBits]
  *   H(x) is the auxiliary function that can be either a hash, HMAC or KMAC.
  *   H_outputBits is the length of the output of the auxiliary function H(x).
  *
  * Currently there is not a comprehensive list of test vectors for this
  * algorithm, especially for H(x) = HMAC and H(x) = KMAC.
  * Test vectors for H(x) = Hash are indirectly used by CAVS KAS tests.
  */
 #include <stdlib.h>
 #include <stdarg.h>
 #include <string.h>
 #include <openssl/hmac.h>
 #include <openssl/evp.h>
 #include <openssl/kdf.h>
 #include <openssl/core_names.h>
 #include <openssl/params.h>
 #include <openssl/proverr.h>
 #include "internal/cryptlib.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"

 typedef struct {
     void *provctx;
     EVP_MAC_CTX *macctx;         /* H(x) = HMAC_hash OR H(x) = KMAC */
     PROV_DIGEST digest;          /* H(x) = hash(x) */
     unsigned char *secret;
     size_t secret_len;
     unsigned char *info;
     size_t info_len;
     unsigned char *salt;
     size_t salt_len;
     size_t out_len; /* optional KMAC parameter */
 } KDF_SSKDF;

 #define SSKDF_MAX_INLEN (1<<30)
 #define SSKDF_KMAC128_DEFAULT_SALT_SIZE (168 - 4)
 #define SSKDF_KMAC256_DEFAULT_SALT_SIZE (136 - 4)

 /* KMAC uses a Customisation string of 'KDF' */
 static const unsigned char kmac_custom_str[] = { 0x4B, 0x44, 0x46 };

 static OSSL_FUNC_kdf_newctx_fn sskdf_new;
 static OSSL_FUNC_kdf_dupctx_fn sskdf_dup;
 static OSSL_FUNC_kdf_freectx_fn sskdf_free;
 static OSSL_FUNC_kdf_reset_fn sskdf_reset;
 static OSSL_FUNC_kdf_derive_fn sskdf_derive;
 static OSSL_FUNC_kdf_derive_fn x963kdf_derive;
 static OSSL_FUNC_kdf_settable_ctx_params_fn sskdf_settable_ctx_params;
 static OSSL_FUNC_kdf_set_ctx_params_fn sskdf_set_ctx_params;
 static OSSL_FUNC_kdf_gettable_ctx_params_fn sskdf_gettable_ctx_params;
 static OSSL_FUNC_kdf_get_ctx_params_fn sskdf_get_ctx_params;

 /*
  * Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
  * Section 4. One-Step Key Derivation using H(x) = hash(x)
  * Note: X9.63 also uses this code with the only difference being that the
  * counter is appended to the secret 'z'.
  * i.e.
  *   result[i] = Hash(counter || z || info) for One Step OR
  *   result[i] = Hash(z || counter || info) for X9.63.
  */
 static int SSKDF_hash_kdm(const EVP_MD *kdf_md,
                           const unsigned char *z, size_t z_len,
                           const unsigned char *info, size_t info_len,
                           unsigned int append_ctr,
                           unsigned char *derived_key, size_t derived_key_len)
 {
     int ret = 0, hlen;
     size_t counter, out_len, len = derived_key_len;
     unsigned char c[4];
     unsigned char mac[EVP_MAX_MD_SIZE];
     unsigned char *out = derived_key;
     EVP_MD_CTX *ctx = NULL, *ctx_init = NULL;

     if (z_len > SSKDF_MAX_INLEN || info_len > SSKDF_MAX_INLEN
             || derived_key_len > SSKDF_MAX_INLEN
             || derived_key_len == 0)
         return 0;

     hlen = EVP_MD_get_size(kdf_md);
     if (hlen <= 0)
         return 0;
     out_len = (size_t)hlen;

     ctx = EVP_MD_CTX_create();
     ctx_init = EVP_MD_CTX_create();
     if (ctx == NULL || ctx_init == NULL)
         goto end;

     if (!EVP_DigestInit(ctx_init, kdf_md))
         goto end;

     for (counter = 1;; counter++) {
         c[0] = (unsigned char)((counter >> 24) & 0xff);
         c[1] = (unsigned char)((counter >> 16) & 0xff);
         c[2] = (unsigned char)((counter >> 8) & 0xff);
         c[3] = (unsigned char)(counter & 0xff);

         if (!(EVP_MD_CTX_copy_ex(ctx, ctx_init)
                 && (append_ctr || EVP_DigestUpdate(ctx, c, sizeof(c)))
                 && EVP_DigestUpdate(ctx, z, z_len)
                 && (!append_ctr || EVP_DigestUpdate(ctx, c, sizeof(c)))
                 && EVP_DigestUpdate(ctx, info, info_len)))
             goto end;
         if (len >= out_len) {
             if (!EVP_DigestFinal_ex(ctx, out, NULL))
                 goto end;
             out += out_len;
             len -= out_len;
             if (len == 0)
                 break;
         } else {
             if (!EVP_DigestFinal_ex(ctx, mac, NULL))
                 goto end;
             memcpy(out, mac, len);
             break;
         }
     }
     ret = 1;
 end:
     EVP_MD_CTX_destroy(ctx);
     EVP_MD_CTX_destroy(ctx_init);
     OPENSSL_cleanse(mac, sizeof(mac));
     return ret;
 }

 static int kmac_init(EVP_MAC_CTX *ctx, const unsigned char *custom,
                      size_t custom_len, size_t kmac_out_len,
                      size_t derived_key_len, unsigned char **out)
 {
     OSSL_PARAM params[2];

     /* Only KMAC has custom data - so return if not KMAC */
     if (custom == NULL)
         return 1;

     params[0] = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM,
                                                   (void *)custom, custom_len);
     params[1] = OSSL_PARAM_construct_end();

     if (!EVP_MAC_CTX_set_params(ctx, params))
         return 0;

     /* By default only do one iteration if kmac_out_len is not specified */
     if (kmac_out_len == 0)
         kmac_out_len = derived_key_len;
     /* otherwise check the size is valid */
     else if (!(kmac_out_len == derived_key_len
             || kmac_out_len == 20
             || kmac_out_len == 28
             || kmac_out_len == 32
             || kmac_out_len == 48
             || kmac_out_len == 64))
         return 0;

     params[0] = OSSL_PARAM_construct_size_t(OSSL_MAC_PARAM_SIZE,
                                             &kmac_out_len);

     if (EVP_MAC_CTX_set_params(ctx, params) <= 0)
         return 0;

     /*
      * For kmac the output buffer can be larger than EVP_MAX_MD_SIZE: so
      * alloc a buffer for this case.
      */
     if (kmac_out_len > EVP_MAX_MD_SIZE) {
         *out = OPENSSL_zalloc(kmac_out_len);
         if (*out == NULL)
             return 0;
     }
     return 1;
 }

 /*
  * Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
  * Section 4. One-Step Key Derivation using MAC: i.e either
  *     H(x) = HMAC-hash(salt, x) OR
  *     H(x) = KMAC#(salt, x, outbits, CustomString='KDF')
  */
 static int SSKDF_mac_kdm(EVP_MAC_CTX *ctx_init,
                          const unsigned char *kmac_custom,
                          size_t kmac_custom_len, size_t kmac_out_len,
                          const unsigned char *salt, size_t salt_len,
                          const unsigned char *z, size_t z_len,
                          const unsigned char *info, size_t info_len,
                          unsigned char *derived_key, size_t derived_key_len)
 {
     int ret = 0;
     size_t counter, out_len, len;
     unsigned char c[4];
     unsigned char mac_buf[EVP_MAX_MD_SIZE];
     unsigned char *out = derived_key;
     EVP_MAC_CTX *ctx = NULL;
     unsigned char *mac = mac_buf, *kmac_buffer = NULL;

     if (z_len > SSKDF_MAX_INLEN || info_len > SSKDF_MAX_INLEN
             || derived_key_len > SSKDF_MAX_INLEN
             || derived_key_len == 0)
         return 0;

     if (!kmac_init(ctx_init, kmac_custom, kmac_custom_len, kmac_out_len,
                    derived_key_len, &kmac_buffer))
         goto end;
     if (kmac_buffer != NULL)
         mac = kmac_buffer;

     if (!EVP_MAC_init(ctx_init, salt, salt_len, NULL))
         goto end;

     out_len = EVP_MAC_CTX_get_mac_size(ctx_init); /* output size */
     if (out_len <= 0 || (mac == mac_buf && out_len > sizeof(mac_buf)))
         goto end;
     len = derived_key_len;

     for (counter = 1;; counter++) {
         c[0] = (unsigned char)((counter >> 24) & 0xff);
         c[1] = (unsigned char)((counter >> 16) & 0xff);
         c[2] = (unsigned char)((counter >> 8) & 0xff);
         c[3] = (unsigned char)(counter & 0xff);

         ctx = EVP_MAC_CTX_dup(ctx_init);
         if (!(ctx != NULL
                 && EVP_MAC_update(ctx, c, sizeof(c))
                 && EVP_MAC_update(ctx, z, z_len)
                 && EVP_MAC_update(ctx, info, info_len)))
             goto end;
         if (len >= out_len) {
             if (!EVP_MAC_final(ctx, out, NULL, len))
                 goto end;
             out += out_len;
             len -= out_len;
             if (len == 0)
                 break;
         } else {
             if (!EVP_MAC_final(ctx, mac, NULL, out_len))
                 goto end;
             memcpy(out, mac, len);
             break;
         }
         EVP_MAC_CTX_free(ctx);
         ctx = NULL;
     }
     ret = 1;
 end:
     if (kmac_buffer != NULL)
         OPENSSL_clear_free(kmac_buffer, kmac_out_len);
     else
         OPENSSL_cleanse(mac_buf, sizeof(mac_buf));

     EVP_MAC_CTX_free(ctx);
     return ret;
 }

 static void *sskdf_new(void *provctx)
 {
     KDF_SSKDF *ctx;

     if (!ossl_prov_is_running())
         return NULL;

     if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL)
         ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
     ctx->provctx = provctx;
     return ctx;
 }

 static void sskdf_reset(void *vctx)
 {
     KDF_SSKDF *ctx = (KDF_SSKDF *)vctx;
     void *provctx = ctx->provctx;

     EVP_MAC_CTX_free(ctx->macctx);
     ossl_prov_digest_reset(&ctx->digest);
     OPENSSL_clear_free(ctx->secret, ctx->secret_len);
     OPENSSL_clear_free(ctx->info, ctx->info_len);
     OPENSSL_clear_free(ctx->salt, ctx->salt_len);
     memset(ctx, 0, sizeof(*ctx));
     ctx->provctx = provctx;
 }

 static void sskdf_free(void *vctx)
 {
     KDF_SSKDF *ctx = (KDF_SSKDF *)vctx;

     if (ctx != NULL) {
         sskdf_reset(ctx);
         OPENSSL_free(ctx);
     }
 }

 static void *sskdf_dup(void *vctx)
 {
     const KDF_SSKDF *src = (const KDF_SSKDF *)vctx;
     KDF_SSKDF *dest;

     dest = sskdf_new(src->provctx);
     if (dest != NULL) {
         if (src->macctx != NULL) {
             dest->macctx = EVP_MAC_CTX_dup(src->macctx);
             if (dest->macctx == NULL)
                 goto err;
         }
         if (!ossl_prov_memdup(src->info, src->info_len,
                               &dest->info, &dest->info_len)
                 || !ossl_prov_memdup(src->salt, src->salt_len,
                                      &dest->salt , &dest->salt_len)
                 || !ossl_prov_memdup(src->secret, src->secret_len,
                                      &dest->secret, &dest->secret_len)
                 || !ossl_prov_digest_copy(&dest->digest, &src->digest))
             goto err;
         dest->out_len = src->out_len;
     }
     return dest;

  err:
     sskdf_free(dest);
     return NULL;
 }

 static int sskdf_set_buffer(unsigned char **out, size_t *out_len,
                             const OSSL_PARAM *p)
 {
     if (p->data == NULL || p->data_size == 0)
         return 1;
     OPENSSL_free(*out);
     *out = NULL;
     return OSSL_PARAM_get_octet_string(p, (void **)out, 0, out_len);
 }

 static size_t sskdf_size(KDF_SSKDF *ctx)
 {
     int len;
     const EVP_MD *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 sskdf_derive(void *vctx, unsigned char *key, size_t keylen,
                         const OSSL_PARAM params[])
 {
     KDF_SSKDF *ctx = (KDF_SSKDF *)vctx;
     const EVP_MD *md;

     if (!ossl_prov_is_running() || !sskdf_set_ctx_params(ctx, params))
         return 0;
     if (ctx->secret == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SECRET);
         return 0;
     }
     md = ossl_prov_digest_md(&ctx->digest);

     if (ctx->macctx != NULL) {
         /* H(x) = KMAC or H(x) = HMAC */
         int ret;
         const unsigned char *custom = NULL;
         size_t custom_len = 0;
         int default_salt_len;
         EVP_MAC *mac = EVP_MAC_CTX_get0_mac(ctx->macctx);

         if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_HMAC)) {
             /* H(x) = HMAC(x, salt, hash) */
             if (md == NULL) {
                 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
                 return 0;
             }
             default_salt_len = EVP_MD_get_size(md);
             if (default_salt_len <= 0)
                 return 0;
         } else if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC128)
                    || EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC256)) {
             /* H(x) = KMACzzz(x, salt, custom) */
             custom = kmac_custom_str;
             custom_len = sizeof(kmac_custom_str);
             if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC128))
                 default_salt_len = SSKDF_KMAC128_DEFAULT_SALT_SIZE;
             else
                 default_salt_len = SSKDF_KMAC256_DEFAULT_SALT_SIZE;
         } else {
             ERR_raise(ERR_LIB_PROV, PROV_R_UNSUPPORTED_MAC_TYPE);
             return 0;
         }
         /* If no salt is set then use a default_salt of zeros */
         if (ctx->salt == NULL || ctx->salt_len <= 0) {
             ctx->salt = OPENSSL_zalloc(default_salt_len);
             if (ctx->salt == NULL) {
                 ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
                 return 0;
             }
             ctx->salt_len = default_salt_len;
         }
         ret = SSKDF_mac_kdm(ctx->macctx,
                             custom, custom_len, ctx->out_len,
                             ctx->salt, ctx->salt_len,
                             ctx->secret, ctx->secret_len,
                             ctx->info, ctx->info_len, key, keylen);
         return ret;
     } else {
         /* H(x) = hash */
         if (md == NULL) {
             ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
             return 0;
         }
         return SSKDF_hash_kdm(md, ctx->secret, ctx->secret_len,
                               ctx->info, ctx->info_len, 0, key, keylen);
     }
 }

 static int x963kdf_derive(void *vctx, unsigned char *key, size_t keylen,
                           const OSSL_PARAM params[])
 {
     KDF_SSKDF *ctx = (KDF_SSKDF *)vctx;
     const EVP_MD *md;

     if (!ossl_prov_is_running() || !sskdf_set_ctx_params(ctx, params))
         return 0;

     if (ctx->secret == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SECRET);
         return 0;
     }

     if (ctx->macctx != NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_NOT_SUPPORTED);
         return 0;
     }

     /* H(x) = hash */
     md = ossl_prov_digest_md(&ctx->digest);
     if (md == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
         return 0;
     }

     return SSKDF_hash_kdm(md, ctx->secret, ctx->secret_len,
                           ctx->info, ctx->info_len, 1, key, keylen);
 }

 static int sskdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 {
     const OSSL_PARAM *p;
     KDF_SSKDF *ctx = vctx;
     OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
     size_t sz;

     if (params == NULL)
         return 1;

     if (!ossl_prov_digest_load_from_params(&ctx->digest, params, libctx))
         return 0;

     if (!ossl_prov_macctx_load_from_params(&ctx->macctx, params,
                                            NULL, NULL, NULL, libctx))
         return 0;

     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SECRET)) != NULL
         || (p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL)
         if (!sskdf_set_buffer(&ctx->secret, &ctx->secret_len, p))
             return 0;

     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_INFO)) != NULL)
         if (!sskdf_set_buffer(&ctx->info, &ctx->info_len, p))
             return 0;

     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SALT)) != NULL)
         if (!sskdf_set_buffer(&ctx->salt, &ctx->salt_len, p))
             return 0;

     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MAC_SIZE))
         != NULL) {
         if (!OSSL_PARAM_get_size_t(p, &sz) || sz == 0)
             return 0;
         ctx->out_len = sz;
     }
     return 1;
 }

 static const OSSL_PARAM *sskdf_settable_ctx_params(ossl_unused void *ctx,
                                                    ossl_unused void *provctx)
 {
     static const OSSL_PARAM known_settable_ctx_params[] = {
         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SECRET, NULL, 0),
         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_INFO, NULL, 0),
         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_MAC, NULL, 0),
         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SALT, NULL, 0),
         OSSL_PARAM_size_t(OSSL_KDF_PARAM_MAC_SIZE, NULL),
         OSSL_PARAM_END
     };
     return known_settable_ctx_params;
 }

 static int sskdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
 {
     KDF_SSKDF *ctx = (KDF_SSKDF *)vctx;
     OSSL_PARAM *p;

     if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL)
         return OSSL_PARAM_set_size_t(p, sskdf_size(ctx));
     return -2;
 }

 static const OSSL_PARAM *sskdf_gettable_ctx_params(ossl_unused void *ctx,
                                                    ossl_unused void *provctx)
 {
     static const OSSL_PARAM known_gettable_ctx_params[] = {
         OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
         OSSL_PARAM_END
     };
     return known_gettable_ctx_params;
 }

 const OSSL_DISPATCH ossl_kdf_sskdf_functions[] = {
     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))sskdf_new },
     { OSSL_FUNC_KDF_DUPCTX, (void(*)(void))sskdf_dup },
     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))sskdf_free },
     { OSSL_FUNC_KDF_RESET, (void(*)(void))sskdf_reset },
     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))sskdf_derive },
     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
       (void(*)(void))sskdf_settable_ctx_params },
     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))sskdf_set_ctx_params },
     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
       (void(*)(void))sskdf_gettable_ctx_params },
     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))sskdf_get_ctx_params },
     { 0, NULL }
 };

 const OSSL_DISPATCH ossl_kdf_x963_kdf_functions[] = {
     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))sskdf_new },
     { OSSL_FUNC_KDF_DUPCTX, (void(*)(void))sskdf_dup },
     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))sskdf_free },
     { OSSL_FUNC_KDF_RESET, (void(*)(void))sskdf_reset },
     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))x963kdf_derive },
     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
       (void(*)(void))sskdf_settable_ctx_params },
     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))sskdf_set_ctx_params },
     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
       (void(*)(void))sskdf_gettable_ctx_params },
     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))sskdf_get_ctx_params },
     { 0, NULL }
 };
	/*
	* Copyright 2019-2022 The OpenSSL Project Authors. All Rights Reserved.
	* Copyright (c) 2019, Oracle and/or its affiliates. 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
	*/

	/*
	* Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
	* Section 4.1.
	*
	* The Single Step KDF algorithm is given by:
	*
	* Result(0) = empty bit string (i.e., the null string).
	* For i = 1 to reps, do the following:
	* Increment counter by 1.
	* Result(i) = Result(i - 1) \|\| H(counter \|\| Z \|\| FixedInfo).
	* DKM = LeftmostBits(Result(reps), L))
	*
	* NOTES:
	* Z is a shared secret required to produce the derived key material.
	* counter is a 4 byte buffer.
	* FixedInfo is a bit string containing context specific data.
	* DKM is the output derived key material.
	* L is the required size of the DKM.
	* reps = [L / H_outputBits]
	* H(x) is the auxiliary function that can be either a hash, HMAC or KMAC.
	* H_outputBits is the length of the output of the auxiliary function H(x).
	*
	* Currently there is not a comprehensive list of test vectors for this
	* algorithm, especially for H(x) = HMAC and H(x) = KMAC.
	* Test vectors for H(x) = Hash are indirectly used by CAVS KAS tests.
	*/
	#include <stdlib.h>
	#include <stdarg.h>
	#include <string.h>
	#include <openssl/hmac.h>
	#include <openssl/evp.h>
	#include <openssl/kdf.h>
	#include <openssl/core_names.h>
	#include <openssl/params.h>
	#include <openssl/proverr.h>
	#include "internal/cryptlib.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"

	typedef struct {
	void *provctx;
	EVP_MAC_CTX macctx; / H(x) = HMAC_hash OR H(x) = KMAC */
	PROV_DIGEST digest; /* H(x) = hash(x) */
	unsigned char *secret;
	size_t secret_len;
	unsigned char *info;
	size_t info_len;
	unsigned char *salt;
	size_t salt_len;
	size_t out_len; /* optional KMAC parameter */
	} KDF_SSKDF;

	#define SSKDF_MAX_INLEN (1<<30)
	#define SSKDF_KMAC128_DEFAULT_SALT_SIZE (168 - 4)
	#define SSKDF_KMAC256_DEFAULT_SALT_SIZE (136 - 4)

	/* KMAC uses a Customisation string of 'KDF' */
	static const unsigned char kmac_custom_str[] = { 0x4B, 0x44, 0x46 };

	static OSSL_FUNC_kdf_newctx_fn sskdf_new;
	static OSSL_FUNC_kdf_dupctx_fn sskdf_dup;
	static OSSL_FUNC_kdf_freectx_fn sskdf_free;
	static OSSL_FUNC_kdf_reset_fn sskdf_reset;
	static OSSL_FUNC_kdf_derive_fn sskdf_derive;
	static OSSL_FUNC_kdf_derive_fn x963kdf_derive;
	static OSSL_FUNC_kdf_settable_ctx_params_fn sskdf_settable_ctx_params;
	static OSSL_FUNC_kdf_set_ctx_params_fn sskdf_set_ctx_params;
	static OSSL_FUNC_kdf_gettable_ctx_params_fn sskdf_gettable_ctx_params;
	static OSSL_FUNC_kdf_get_ctx_params_fn sskdf_get_ctx_params;

	/*
	* Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
	* Section 4. One-Step Key Derivation using H(x) = hash(x)
	* Note: X9.63 also uses this code with the only difference being that the
	* counter is appended to the secret 'z'.
	* i.e.
	* result[i] = Hash(counter \|\| z \|\| info) for One Step OR
	* result[i] = Hash(z \|\| counter \|\| info) for X9.63.
	*/
	static int SSKDF_hash_kdm(const EVP_MD *kdf_md,
	const unsigned char *z, size_t z_len,
	const unsigned char *info, size_t info_len,
	unsigned int append_ctr,
	unsigned char *derived_key, size_t derived_key_len)
	{
	int ret = 0, hlen;
	size_t counter, out_len, len = derived_key_len;
	unsigned char c[4];
	unsigned char mac[EVP_MAX_MD_SIZE];
	unsigned char *out = derived_key;
	EVP_MD_CTX ctx = NULL, ctx_init = NULL;

	if (z_len > SSKDF_MAX_INLEN \|\| info_len > SSKDF_MAX_INLEN
	\|\| derived_key_len > SSKDF_MAX_INLEN
	\|\| derived_key_len == 0)
	return 0;

	hlen = EVP_MD_get_size(kdf_md);
	if (hlen <= 0)
	return 0;
	out_len = (size_t)hlen;

	ctx = EVP_MD_CTX_create();
	ctx_init = EVP_MD_CTX_create();
	if (ctx == NULL \|\| ctx_init == NULL)
	goto end;

	if (!EVP_DigestInit(ctx_init, kdf_md))
	goto end;

	for (counter = 1;; counter++) {
	c[0] = (unsigned char)((counter >> 24) & 0xff);
	c[1] = (unsigned char)((counter >> 16) & 0xff);
	c[2] = (unsigned char)((counter >> 8) & 0xff);
	c[3] = (unsigned char)(counter & 0xff);

	if (!(EVP_MD_CTX_copy_ex(ctx, ctx_init)
	&& (append_ctr \|\| EVP_DigestUpdate(ctx, c, sizeof(c)))
	&& EVP_DigestUpdate(ctx, z, z_len)
	&& (!append_ctr \|\| EVP_DigestUpdate(ctx, c, sizeof(c)))
	&& EVP_DigestUpdate(ctx, info, info_len)))
	goto end;
	if (len >= out_len) {
	if (!EVP_DigestFinal_ex(ctx, out, NULL))
	goto end;
	out += out_len;
	len -= out_len;
	if (len == 0)
	break;
	} else {
	if (!EVP_DigestFinal_ex(ctx, mac, NULL))
	goto end;
	memcpy(out, mac, len);
	break;
	}
	}
	ret = 1;
	end:
	EVP_MD_CTX_destroy(ctx);
	EVP_MD_CTX_destroy(ctx_init);
	OPENSSL_cleanse(mac, sizeof(mac));
	return ret;
	}

	static int kmac_init(EVP_MAC_CTX ctx, const unsigned char custom,
	size_t custom_len, size_t kmac_out_len,
	size_t derived_key_len, unsigned char **out)
	{
	OSSL_PARAM params[2];

	/* Only KMAC has custom data - so return if not KMAC */
	if (custom == NULL)
	return 1;

	params[0] = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM,
	(void *)custom, custom_len);
	params[1] = OSSL_PARAM_construct_end();

	if (!EVP_MAC_CTX_set_params(ctx, params))
	return 0;

	/* By default only do one iteration if kmac_out_len is not specified */
	if (kmac_out_len == 0)
	kmac_out_len = derived_key_len;
	/* otherwise check the size is valid */
	else if (!(kmac_out_len == derived_key_len
	\|\| kmac_out_len == 20
	\|\| kmac_out_len == 28
	\|\| kmac_out_len == 32
	\|\| kmac_out_len == 48
	\|\| kmac_out_len == 64))
	return 0;

	params[0] = OSSL_PARAM_construct_size_t(OSSL_MAC_PARAM_SIZE,
	&kmac_out_len);

	if (EVP_MAC_CTX_set_params(ctx, params) <= 0)
	return 0;

	/*
	* For kmac the output buffer can be larger than EVP_MAX_MD_SIZE: so
	* alloc a buffer for this case.
	*/
	if (kmac_out_len > EVP_MAX_MD_SIZE) {
	*out = OPENSSL_zalloc(kmac_out_len);
	if (*out == NULL)
	return 0;
	}
	return 1;
	}

	/*
	* Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
	* Section 4. One-Step Key Derivation using MAC: i.e either
	* H(x) = HMAC-hash(salt, x) OR
	* H(x) = KMAC#(salt, x, outbits, CustomString='KDF')
	*/
	static int SSKDF_mac_kdm(EVP_MAC_CTX *ctx_init,
	const unsigned char *kmac_custom,
	size_t kmac_custom_len, size_t kmac_out_len,
	const unsigned char *salt, size_t salt_len,
	const unsigned char *z, size_t z_len,
	const unsigned char *info, size_t info_len,
	unsigned char *derived_key, size_t derived_key_len)
	{
	int ret = 0;
	size_t counter, out_len, len;
	unsigned char c[4];
	unsigned char mac_buf[EVP_MAX_MD_SIZE];
	unsigned char *out = derived_key;
	EVP_MAC_CTX *ctx = NULL;
	unsigned char mac = mac_buf, kmac_buffer = NULL;

	if (z_len > SSKDF_MAX_INLEN \|\| info_len > SSKDF_MAX_INLEN
	\|\| derived_key_len > SSKDF_MAX_INLEN
	\|\| derived_key_len == 0)
	return 0;

	if (!kmac_init(ctx_init, kmac_custom, kmac_custom_len, kmac_out_len,
	derived_key_len, &kmac_buffer))
	goto end;
	if (kmac_buffer != NULL)
	mac = kmac_buffer;

	if (!EVP_MAC_init(ctx_init, salt, salt_len, NULL))
	goto end;

	out_len = EVP_MAC_CTX_get_mac_size(ctx_init); /* output size */
	if (out_len <= 0 \|\| (mac == mac_buf && out_len > sizeof(mac_buf)))
	goto end;
	len = derived_key_len;

	for (counter = 1;; counter++) {
	c[0] = (unsigned char)((counter >> 24) & 0xff);
	c[1] = (unsigned char)((counter >> 16) & 0xff);
	c[2] = (unsigned char)((counter >> 8) & 0xff);
	c[3] = (unsigned char)(counter & 0xff);

	ctx = EVP_MAC_CTX_dup(ctx_init);
	if (!(ctx != NULL
	&& EVP_MAC_update(ctx, c, sizeof(c))
	&& EVP_MAC_update(ctx, z, z_len)
	&& EVP_MAC_update(ctx, info, info_len)))
	goto end;
	if (len >= out_len) {
	if (!EVP_MAC_final(ctx, out, NULL, len))
	goto end;
	out += out_len;
	len -= out_len;
	if (len == 0)
	break;
	} else {
	if (!EVP_MAC_final(ctx, mac, NULL, out_len))
	goto end;
	memcpy(out, mac, len);
	break;
	}
	EVP_MAC_CTX_free(ctx);
	ctx = NULL;
	}
	ret = 1;
	end:
	if (kmac_buffer != NULL)
	OPENSSL_clear_free(kmac_buffer, kmac_out_len);
	else
	OPENSSL_cleanse(mac_buf, sizeof(mac_buf));

	EVP_MAC_CTX_free(ctx);
	return ret;
	}

	static void sskdf_new(void provctx)
	{
	KDF_SSKDF *ctx;

	if (!ossl_prov_is_running())
	return NULL;

	if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL)
	ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
	ctx->provctx = provctx;
	return ctx;
	}

	static void sskdf_reset(void *vctx)
	{
	KDF_SSKDF ctx = (KDF_SSKDF )vctx;
	void *provctx = ctx->provctx;

	EVP_MAC_CTX_free(ctx->macctx);
	ossl_prov_digest_reset(&ctx->digest);
	OPENSSL_clear_free(ctx->secret, ctx->secret_len);
	OPENSSL_clear_free(ctx->info, ctx->info_len);
	OPENSSL_clear_free(ctx->salt, ctx->salt_len);
	memset(ctx, 0, sizeof(*ctx));
	ctx->provctx = provctx;
	}

	static void sskdf_free(void *vctx)
	{
	KDF_SSKDF ctx = (KDF_SSKDF )vctx;

	if (ctx != NULL) {
	sskdf_reset(ctx);
	OPENSSL_free(ctx);
	}
	}

	static void sskdf_dup(void vctx)
	{
	const KDF_SSKDF src = (const KDF_SSKDF )vctx;
	KDF_SSKDF *dest;

	dest = sskdf_new(src->provctx);
	if (dest != NULL) {
	if (src->macctx != NULL) {
	dest->macctx = EVP_MAC_CTX_dup(src->macctx);
	if (dest->macctx == NULL)
	goto err;
	}
	if (!ossl_prov_memdup(src->info, src->info_len,
	&dest->info, &dest->info_len)
	\|\| !ossl_prov_memdup(src->salt, src->salt_len,
	&dest->salt , &dest->salt_len)
	\|\| !ossl_prov_memdup(src->secret, src->secret_len,
	&dest->secret, &dest->secret_len)
	\|\| !ossl_prov_digest_copy(&dest->digest, &src->digest))
	goto err;
	dest->out_len = src->out_len;
	}
	return dest;

	err:
	sskdf_free(dest);
	return NULL;
	}

	static int sskdf_set_buffer(unsigned char *out, size_t out_len,
	const OSSL_PARAM *p)
	{
	if (p->data == NULL \|\| p->data_size == 0)
	return 1;
	OPENSSL_free(*out);
	*out = NULL;
	return OSSL_PARAM_get_octet_string(p, (void **)out, 0, out_len);
	}

	static size_t sskdf_size(KDF_SSKDF *ctx)
	{
	int len;
	const EVP_MD *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 sskdf_derive(void vctx, unsigned char key, size_t keylen,
	const OSSL_PARAM params[])
	{
	KDF_SSKDF ctx = (KDF_SSKDF )vctx;
	const EVP_MD *md;

	if (!ossl_prov_is_running() \|\| !sskdf_set_ctx_params(ctx, params))
	return 0;
	if (ctx->secret == NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SECRET);
	return 0;
	}
	md = ossl_prov_digest_md(&ctx->digest);

	if (ctx->macctx != NULL) {
	/* H(x) = KMAC or H(x) = HMAC */
	int ret;
	const unsigned char *custom = NULL;
	size_t custom_len = 0;
	int default_salt_len;
	EVP_MAC *mac = EVP_MAC_CTX_get0_mac(ctx->macctx);

	if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_HMAC)) {
	/* H(x) = HMAC(x, salt, hash) */
	if (md == NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
	return 0;
	}
	default_salt_len = EVP_MD_get_size(md);
	if (default_salt_len <= 0)
	return 0;
	} else if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC128)
	\|\| EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC256)) {
	/* H(x) = KMACzzz(x, salt, custom) */
	custom = kmac_custom_str;
	custom_len = sizeof(kmac_custom_str);
	if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC128))
	default_salt_len = SSKDF_KMAC128_DEFAULT_SALT_SIZE;
	else
	default_salt_len = SSKDF_KMAC256_DEFAULT_SALT_SIZE;
	} else {
	ERR_raise(ERR_LIB_PROV, PROV_R_UNSUPPORTED_MAC_TYPE);
	return 0;
	}
	/* If no salt is set then use a default_salt of zeros */
	if (ctx->salt == NULL \|\| ctx->salt_len <= 0) {
	ctx->salt = OPENSSL_zalloc(default_salt_len);
	if (ctx->salt == NULL) {
	ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
	return 0;
	}
	ctx->salt_len = default_salt_len;
	}
	ret = SSKDF_mac_kdm(ctx->macctx,
	custom, custom_len, ctx->out_len,
	ctx->salt, ctx->salt_len,
	ctx->secret, ctx->secret_len,
	ctx->info, ctx->info_len, key, keylen);
	return ret;
	} else {
	/* H(x) = hash */
	if (md == NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
	return 0;
	}
	return SSKDF_hash_kdm(md, ctx->secret, ctx->secret_len,
	ctx->info, ctx->info_len, 0, key, keylen);
	}
	}

	static int x963kdf_derive(void vctx, unsigned char key, size_t keylen,
	const OSSL_PARAM params[])
	{
	KDF_SSKDF ctx = (KDF_SSKDF )vctx;
	const EVP_MD *md;

	if (!ossl_prov_is_running() \|\| !sskdf_set_ctx_params(ctx, params))
	return 0;

	if (ctx->secret == NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SECRET);
	return 0;
	}

	if (ctx->macctx != NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_NOT_SUPPORTED);
	return 0;
	}

	/* H(x) = hash */
	md = ossl_prov_digest_md(&ctx->digest);
	if (md == NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
	return 0;
	}

	return SSKDF_hash_kdm(md, ctx->secret, ctx->secret_len,
	ctx->info, ctx->info_len, 1, key, keylen);
	}

	static int sskdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
	{
	const OSSL_PARAM *p;
	KDF_SSKDF *ctx = vctx;
	OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
	size_t sz;

	if (params == NULL)
	return 1;

	if (!ossl_prov_digest_load_from_params(&ctx->digest, params, libctx))
	return 0;

	if (!ossl_prov_macctx_load_from_params(&ctx->macctx, params,
	NULL, NULL, NULL, libctx))
	return 0;

	if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SECRET)) != NULL
	\|\| (p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL)
	if (!sskdf_set_buffer(&ctx->secret, &ctx->secret_len, p))
	return 0;

	if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_INFO)) != NULL)
	if (!sskdf_set_buffer(&ctx->info, &ctx->info_len, p))
	return 0;

	if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SALT)) != NULL)
	if (!sskdf_set_buffer(&ctx->salt, &ctx->salt_len, p))
	return 0;

	if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MAC_SIZE))
	!= NULL) {
	if (!OSSL_PARAM_get_size_t(p, &sz) \|\| sz == 0)
	return 0;
	ctx->out_len = sz;
	}
	return 1;
	}

	static const OSSL_PARAM sskdf_settable_ctx_params(ossl_unused void ctx,
	ossl_unused void *provctx)
	{
	static const OSSL_PARAM known_settable_ctx_params[] = {
	OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SECRET, NULL, 0),
	OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
	OSSL_PARAM_octet_string(OSSL_KDF_PARAM_INFO, NULL, 0),
	OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
	OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
	OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_MAC, NULL, 0),
	OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SALT, NULL, 0),
	OSSL_PARAM_size_t(OSSL_KDF_PARAM_MAC_SIZE, NULL),
	OSSL_PARAM_END
	};
	return known_settable_ctx_params;
	}

	static int sskdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
	{
	KDF_SSKDF ctx = (KDF_SSKDF )vctx;
	OSSL_PARAM *p;

	if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL)
	return OSSL_PARAM_set_size_t(p, sskdf_size(ctx));
	return -2;
	}

	static const OSSL_PARAM sskdf_gettable_ctx_params(ossl_unused void ctx,
	ossl_unused void *provctx)
	{
	static const OSSL_PARAM known_gettable_ctx_params[] = {
	OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
	OSSL_PARAM_END
	};
	return known_gettable_ctx_params;
	}

	const OSSL_DISPATCH ossl_kdf_sskdf_functions[] = {
	{ OSSL_FUNC_KDF_NEWCTX, (void(*)(void))sskdf_new },
	{ OSSL_FUNC_KDF_DUPCTX, (void(*)(void))sskdf_dup },
	{ OSSL_FUNC_KDF_FREECTX, (void(*)(void))sskdf_free },
	{ OSSL_FUNC_KDF_RESET, (void(*)(void))sskdf_reset },
	{ OSSL_FUNC_KDF_DERIVE, (void(*)(void))sskdf_derive },
	{ OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
	(void(*)(void))sskdf_settable_ctx_params },
	{ OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))sskdf_set_ctx_params },
	{ OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
	(void(*)(void))sskdf_gettable_ctx_params },
	{ OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))sskdf_get_ctx_params },
	{ 0, NULL }
	};

	const OSSL_DISPATCH ossl_kdf_x963_kdf_functions[] = {
	{ OSSL_FUNC_KDF_NEWCTX, (void(*)(void))sskdf_new },
	{ OSSL_FUNC_KDF_DUPCTX, (void(*)(void))sskdf_dup },
	{ OSSL_FUNC_KDF_FREECTX, (void(*)(void))sskdf_free },
	{ OSSL_FUNC_KDF_RESET, (void(*)(void))sskdf_reset },
	{ OSSL_FUNC_KDF_DERIVE, (void(*)(void))x963kdf_derive },
	{ OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
	(void(*)(void))sskdf_settable_ctx_params },
	{ OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))sskdf_set_ctx_params },
	{ OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
	(void(*)(void))sskdf_gettable_ctx_params },
	{ OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))sskdf_get_ctx_params },
	{ 0, NULL }
	};