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

 /*
  * Copyright 2018-2022 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/core_names.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"

 /* See RFC 4253, Section 7.2 */
 static OSSL_FUNC_kdf_newctx_fn kdf_sshkdf_new;
 static OSSL_FUNC_kdf_dupctx_fn kdf_sshkdf_dup;
 static OSSL_FUNC_kdf_freectx_fn kdf_sshkdf_free;
 static OSSL_FUNC_kdf_reset_fn kdf_sshkdf_reset;
 static OSSL_FUNC_kdf_derive_fn kdf_sshkdf_derive;
 static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_sshkdf_settable_ctx_params;
 static OSSL_FUNC_kdf_set_ctx_params_fn kdf_sshkdf_set_ctx_params;
 static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_sshkdf_gettable_ctx_params;
 static OSSL_FUNC_kdf_get_ctx_params_fn kdf_sshkdf_get_ctx_params;

 static int SSHKDF(const EVP_MD *evp_md,
                   const unsigned char *key, size_t key_len,
                   const unsigned char *xcghash, size_t xcghash_len,
                   const unsigned char *session_id, size_t session_id_len,
                   char type, unsigned char *okey, size_t okey_len);

 typedef struct {
     void *provctx;
     PROV_DIGEST digest;
     unsigned char *key; /* K */
     size_t key_len;
     unsigned char *xcghash; /* H */
     size_t xcghash_len;
     char type; /* X */
     unsigned char *session_id;
     size_t session_id_len;
 } KDF_SSHKDF;

 static void *kdf_sshkdf_new(void *provctx)
 {
     KDF_SSHKDF *ctx;

     if (!ossl_prov_is_running())
         return NULL;

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

 static void kdf_sshkdf_free(void *vctx)
 {
     KDF_SSHKDF *ctx = (KDF_SSHKDF *)vctx;

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

 static void kdf_sshkdf_reset(void *vctx)
 {
     KDF_SSHKDF *ctx = (KDF_SSHKDF *)vctx;
     void *provctx = ctx->provctx;

     ossl_prov_digest_reset(&ctx->digest);
     OPENSSL_clear_free(ctx->key, ctx->key_len);
     OPENSSL_clear_free(ctx->xcghash, ctx->xcghash_len);
     OPENSSL_clear_free(ctx->session_id, ctx->session_id_len);
     memset(ctx, 0, sizeof(*ctx));
     ctx->provctx = provctx;
 }

 static void *kdf_sshkdf_dup(void *vctx)
 {
     const KDF_SSHKDF *src = (const KDF_SSHKDF *)vctx;
     KDF_SSHKDF *dest;

     dest = kdf_sshkdf_new(src->provctx);
     if (dest != NULL) {
         if (!ossl_prov_memdup(src->key, src->key_len,
                               &dest->key, &dest->key_len)
                 || !ossl_prov_memdup(src->xcghash, src->xcghash_len,
                                      &dest->xcghash , &dest->xcghash_len)
                 || !ossl_prov_memdup(src->session_id, src->session_id_len,
                                      &dest->session_id , &dest->session_id_len)
                 || !ossl_prov_digest_copy(&dest->digest, &src->digest))
             goto err;
         dest->type = src->type;
     }
     return dest;

  err:
     kdf_sshkdf_free(dest);
     return NULL;
 }

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

     if (!ossl_prov_is_running() || !kdf_sshkdf_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->key == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
         return 0;
     }
     if (ctx->xcghash == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_XCGHASH);
         return 0;
     }
     if (ctx->session_id == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SESSION_ID);
         return 0;
     }
     if (ctx->type == 0) {
         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_TYPE);
         return 0;
     }
     return SSHKDF(md, ctx->key, ctx->key_len,
                   ctx->xcghash, ctx->xcghash_len,
                   ctx->session_id, ctx->session_id_len,
                   ctx->type, key, keylen);
 }

 static int kdf_sshkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 {
     const OSSL_PARAM *p;
     KDF_SSHKDF *ctx = vctx;
     OSSL_LIB_CTX *provctx = PROV_LIBCTX_OF(ctx->provctx);

     if (params == NULL)
         return 1;

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

     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL)
         if (!sshkdf_set_membuf(&ctx->key, &ctx->key_len, p))
             return 0;

     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_XCGHASH))
         != NULL)
         if (!sshkdf_set_membuf(&ctx->xcghash, &ctx->xcghash_len, p))
             return 0;

     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_SESSION_ID))
         != NULL)
         if (!sshkdf_set_membuf(&ctx->session_id, &ctx->session_id_len, p))
             return 0;

     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_TYPE))
         != NULL) {
         const char *kdftype;

         if (!OSSL_PARAM_get_utf8_string_ptr(p, &kdftype))
             return 0;
         /* Expect one character (byte in this case) */
         if (kdftype == NULL || p->data_size != 1)
             return 0;
         if (kdftype[0] < 65 || kdftype[0] > 70) {
             ERR_raise(ERR_LIB_PROV, PROV_R_VALUE_ERROR);
             return 0;
         }
         ctx->type = kdftype[0];
     }
     return 1;
 }

 static const OSSL_PARAM *kdf_sshkdf_settable_ctx_params(ossl_unused void *ctx,
                                                         ossl_unused void *p_ctx)
 {
     static const OSSL_PARAM known_settable_ctx_params[] = {
         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SSHKDF_XCGHASH, NULL, 0),
         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SSHKDF_SESSION_ID, NULL, 0),
         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_SSHKDF_TYPE, NULL, 0),
         OSSL_PARAM_END
     };
     return known_settable_ctx_params;
 }

 static int kdf_sshkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
 {
     OSSL_PARAM *p;

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

 static const OSSL_PARAM *kdf_sshkdf_gettable_ctx_params(ossl_unused void *ctx,
                                                         ossl_unused void *p_ctx)
 {
     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_sshkdf_functions[] = {
     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_sshkdf_new },
     { OSSL_FUNC_KDF_DUPCTX, (void(*)(void))kdf_sshkdf_dup },
     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_sshkdf_free },
     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_sshkdf_reset },
     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_sshkdf_derive },
     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
       (void(*)(void))kdf_sshkdf_settable_ctx_params },
     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_sshkdf_set_ctx_params },
     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
       (void(*)(void))kdf_sshkdf_gettable_ctx_params },
     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_sshkdf_get_ctx_params },
     { 0, NULL }
 };

 static int SSHKDF(const EVP_MD *evp_md,
                   const unsigned char *key, size_t key_len,
                   const unsigned char *xcghash, size_t xcghash_len,
                   const unsigned char *session_id, size_t session_id_len,
                   char type, unsigned char *okey, size_t okey_len)
 {
     EVP_MD_CTX *md = NULL;
     unsigned char digest[EVP_MAX_MD_SIZE];
     unsigned int dsize = 0;
     size_t cursize = 0;
     int ret = 0;

     md = EVP_MD_CTX_new();
     if (md == NULL)
         return 0;

     if (!EVP_DigestInit_ex(md, evp_md, NULL))
         goto out;

     if (!EVP_DigestUpdate(md, key, key_len))
         goto out;

     if (!EVP_DigestUpdate(md, xcghash, xcghash_len))
         goto out;

     if (!EVP_DigestUpdate(md, &type, 1))
         goto out;

     if (!EVP_DigestUpdate(md, session_id, session_id_len))
         goto out;

     if (!EVP_DigestFinal_ex(md, digest, &dsize))
         goto out;

     if (okey_len < dsize) {
         memcpy(okey, digest, okey_len);
         ret = 1;
         goto out;
     }

     memcpy(okey, digest, dsize);

     for (cursize = dsize; cursize < okey_len; cursize += dsize) {

         if (!EVP_DigestInit_ex(md, evp_md, NULL))
             goto out;

         if (!EVP_DigestUpdate(md, key, key_len))
             goto out;

         if (!EVP_DigestUpdate(md, xcghash, xcghash_len))
             goto out;

         if (!EVP_DigestUpdate(md, okey, cursize))
             goto out;

         if (!EVP_DigestFinal_ex(md, digest, &dsize))
             goto out;

         if (okey_len < cursize + dsize) {
             memcpy(okey + cursize, digest, okey_len - cursize);
             ret = 1;
             goto out;
         }

         memcpy(okey + cursize, digest, dsize);
     }

     ret = 1;

 out:
     EVP_MD_CTX_free(md);
     OPENSSL_cleanse(digest, EVP_MAX_MD_SIZE);
     return ret;
 }
	/*
	* Copyright 2018-2022 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/core_names.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"

	/* See RFC 4253, Section 7.2 */
	static OSSL_FUNC_kdf_newctx_fn kdf_sshkdf_new;
	static OSSL_FUNC_kdf_dupctx_fn kdf_sshkdf_dup;
	static OSSL_FUNC_kdf_freectx_fn kdf_sshkdf_free;
	static OSSL_FUNC_kdf_reset_fn kdf_sshkdf_reset;
	static OSSL_FUNC_kdf_derive_fn kdf_sshkdf_derive;
	static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_sshkdf_settable_ctx_params;
	static OSSL_FUNC_kdf_set_ctx_params_fn kdf_sshkdf_set_ctx_params;
	static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_sshkdf_gettable_ctx_params;
	static OSSL_FUNC_kdf_get_ctx_params_fn kdf_sshkdf_get_ctx_params;

	static int SSHKDF(const EVP_MD *evp_md,
	const unsigned char *key, size_t key_len,
	const unsigned char *xcghash, size_t xcghash_len,
	const unsigned char *session_id, size_t session_id_len,
	char type, unsigned char *okey, size_t okey_len);

	typedef struct {
	void *provctx;
	PROV_DIGEST digest;
	unsigned char key; / K */
	size_t key_len;
	unsigned char xcghash; / H */
	size_t xcghash_len;
	char type; /* X */
	unsigned char *session_id;
	size_t session_id_len;
	} KDF_SSHKDF;

	static void kdf_sshkdf_new(void provctx)
	{
	KDF_SSHKDF *ctx;

	if (!ossl_prov_is_running())
	return NULL;

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

	static void kdf_sshkdf_free(void *vctx)
	{
	KDF_SSHKDF ctx = (KDF_SSHKDF )vctx;

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

	static void kdf_sshkdf_reset(void *vctx)
	{
	KDF_SSHKDF ctx = (KDF_SSHKDF )vctx;
	void *provctx = ctx->provctx;

	ossl_prov_digest_reset(&ctx->digest);
	OPENSSL_clear_free(ctx->key, ctx->key_len);
	OPENSSL_clear_free(ctx->xcghash, ctx->xcghash_len);
	OPENSSL_clear_free(ctx->session_id, ctx->session_id_len);
	memset(ctx, 0, sizeof(*ctx));
	ctx->provctx = provctx;
	}

	static void kdf_sshkdf_dup(void vctx)
	{
	const KDF_SSHKDF src = (const KDF_SSHKDF )vctx;
	KDF_SSHKDF *dest;

	dest = kdf_sshkdf_new(src->provctx);
	if (dest != NULL) {
	if (!ossl_prov_memdup(src->key, src->key_len,
	&dest->key, &dest->key_len)
	\|\| !ossl_prov_memdup(src->xcghash, src->xcghash_len,
	&dest->xcghash , &dest->xcghash_len)
	\|\| !ossl_prov_memdup(src->session_id, src->session_id_len,
	&dest->session_id , &dest->session_id_len)
	\|\| !ossl_prov_digest_copy(&dest->digest, &src->digest))
	goto err;
	dest->type = src->type;
	}
	return dest;

	err:
	kdf_sshkdf_free(dest);
	return NULL;
	}

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

	if (!ossl_prov_is_running() \|\| !kdf_sshkdf_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->key == NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
	return 0;
	}
	if (ctx->xcghash == NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_XCGHASH);
	return 0;
	}
	if (ctx->session_id == NULL) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SESSION_ID);
	return 0;
	}
	if (ctx->type == 0) {
	ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_TYPE);
	return 0;
	}
	return SSHKDF(md, ctx->key, ctx->key_len,
	ctx->xcghash, ctx->xcghash_len,
	ctx->session_id, ctx->session_id_len,
	ctx->type, key, keylen);
	}

	static int kdf_sshkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
	{
	const OSSL_PARAM *p;
	KDF_SSHKDF *ctx = vctx;
	OSSL_LIB_CTX *provctx = PROV_LIBCTX_OF(ctx->provctx);

	if (params == NULL)
	return 1;

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

	if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL)
	if (!sshkdf_set_membuf(&ctx->key, &ctx->key_len, p))
	return 0;

	if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_XCGHASH))
	!= NULL)
	if (!sshkdf_set_membuf(&ctx->xcghash, &ctx->xcghash_len, p))
	return 0;

	if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_SESSION_ID))
	!= NULL)
	if (!sshkdf_set_membuf(&ctx->session_id, &ctx->session_id_len, p))
	return 0;

	if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_TYPE))
	!= NULL) {
	const char *kdftype;

	if (!OSSL_PARAM_get_utf8_string_ptr(p, &kdftype))
	return 0;
	/* Expect one character (byte in this case) */
	if (kdftype == NULL \|\| p->data_size != 1)
	return 0;
	if (kdftype[0] < 65 \|\| kdftype[0] > 70) {
	ERR_raise(ERR_LIB_PROV, PROV_R_VALUE_ERROR);
	return 0;
	}
	ctx->type = kdftype[0];
	}
	return 1;
	}

	static const OSSL_PARAM kdf_sshkdf_settable_ctx_params(ossl_unused void ctx,
	ossl_unused void *p_ctx)
	{
	static const OSSL_PARAM known_settable_ctx_params[] = {
	OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
	OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
	OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
	OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SSHKDF_XCGHASH, NULL, 0),
	OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SSHKDF_SESSION_ID, NULL, 0),
	OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_SSHKDF_TYPE, NULL, 0),
	OSSL_PARAM_END
	};
	return known_settable_ctx_params;
	}

	static int kdf_sshkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
	{
	OSSL_PARAM *p;

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

	static const OSSL_PARAM kdf_sshkdf_gettable_ctx_params(ossl_unused void ctx,
	ossl_unused void *p_ctx)
	{
	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_sshkdf_functions[] = {
	{ OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_sshkdf_new },
	{ OSSL_FUNC_KDF_DUPCTX, (void(*)(void))kdf_sshkdf_dup },
	{ OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_sshkdf_free },
	{ OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_sshkdf_reset },
	{ OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_sshkdf_derive },
	{ OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
	(void(*)(void))kdf_sshkdf_settable_ctx_params },
	{ OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_sshkdf_set_ctx_params },
	{ OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
	(void(*)(void))kdf_sshkdf_gettable_ctx_params },
	{ OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_sshkdf_get_ctx_params },
	{ 0, NULL }
	};

	static int SSHKDF(const EVP_MD *evp_md,
	const unsigned char *key, size_t key_len,
	const unsigned char *xcghash, size_t xcghash_len,
	const unsigned char *session_id, size_t session_id_len,
	char type, unsigned char *okey, size_t okey_len)
	{
	EVP_MD_CTX *md = NULL;
	unsigned char digest[EVP_MAX_MD_SIZE];
	unsigned int dsize = 0;
	size_t cursize = 0;
	int ret = 0;

	md = EVP_MD_CTX_new();
	if (md == NULL)
	return 0;

	if (!EVP_DigestInit_ex(md, evp_md, NULL))
	goto out;

	if (!EVP_DigestUpdate(md, key, key_len))
	goto out;

	if (!EVP_DigestUpdate(md, xcghash, xcghash_len))
	goto out;

	if (!EVP_DigestUpdate(md, &type, 1))
	goto out;

	if (!EVP_DigestUpdate(md, session_id, session_id_len))
	goto out;

	if (!EVP_DigestFinal_ex(md, digest, &dsize))
	goto out;

	if (okey_len < dsize) {
	memcpy(okey, digest, okey_len);
	ret = 1;
	goto out;
	}

	memcpy(okey, digest, dsize);

	for (cursize = dsize; cursize < okey_len; cursize += dsize) {

	if (!EVP_DigestInit_ex(md, evp_md, NULL))
	goto out;

	if (!EVP_DigestUpdate(md, key, key_len))
	goto out;

	if (!EVP_DigestUpdate(md, xcghash, xcghash_len))
	goto out;

	if (!EVP_DigestUpdate(md, okey, cursize))
	goto out;

	if (!EVP_DigestFinal_ex(md, digest, &dsize))
	goto out;

	if (okey_len < cursize + dsize) {
	memcpy(okey + cursize, digest, okey_len - cursize);
	ret = 1;
	goto out;
	}

	memcpy(okey + cursize, digest, dsize);
	}

	ret = 1;

	out:
	EVP_MD_CTX_free(md);
	OPENSSL_cleanse(digest, EVP_MAX_MD_SIZE);
	return ret;
	}