sshkdf.c
/*
* Copyright 2018-2023 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)
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 },
OSSL_DISPATCH_END
};
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;
}
