/*

 * Copyright 2016-2018 The OpenSSL Project Authors. 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

 */

#include <stdlib.h>

#include <string.h>

#include <openssl/hmac.h>

#include <openssl/kdf.h>

#include <openssl/evp.h>

#include "internal/cryptlib.h"

#include "internal/evp_int.h"

#define HKDF_MAXBUF 1024

static unsigned char *HKDF(const EVP_MD *evp_md,

                           const unsigned char *salt, size_t salt_len,

                           const unsigned char *key, size_t key_len,

                           const unsigned char *info, size_t info_len,

                           unsigned char *okm, size_t okm_len);

static unsigned char *HKDF_Extract(const EVP_MD *evp_md,

                                   const unsigned char *salt, size_t salt_len,

                                   const unsigned char *key, size_t key_len,

                                   unsigned char *prk, size_t *prk_len);

static unsigned char *HKDF_Expand(const EVP_MD *evp_md,

                                  const unsigned char *prk, size_t prk_len,

                                  const unsigned char *info, size_t info_len,

                                  unsigned char *okm, size_t okm_len);

typedef struct {

    int mode;

    const EVP_MD *md;

    unsigned char *salt;

    size_t salt_len;

    unsigned char *key;

    size_t key_len;

    unsigned char info[HKDF_MAXBUF];

    size_t info_len;

} HKDF_PKEY_CTX;

static int pkey_hkdf_init(EVP_PKEY_CTX *ctx)

{

    HKDF_PKEY_CTX *kctx;

    if ((kctx = OPENSSL_zalloc(sizeof(*kctx))) == NULL) {

        KDFerr(KDF_F_PKEY_HKDF_INIT, ERR_R_MALLOC_FAILURE);

        return 0;

    }

    ctx->data = kctx;

    return 1;

}

static void pkey_hkdf_cleanup(EVP_PKEY_CTX *ctx)

{

    HKDF_PKEY_CTX *kctx = ctx->data;

    OPENSSL_clear_free(kctx->salt, kctx->salt_len);

    OPENSSL_clear_free(kctx->key, kctx->key_len);

    OPENSSL_cleanse(kctx->info, kctx->info_len);

    OPENSSL_free(kctx);

}

static int pkey_hkdf_ctrl(EVP_PKEY_CTX *ctx, int type, int p1, void *p2)

{

    HKDF_PKEY_CTX *kctx = ctx->data;

    switch (type) {

    case EVP_PKEY_CTRL_HKDF_MD:

        if (p2 == NULL)

            return 0;

        kctx->md = p2;

        return 1;

    case EVP_PKEY_CTRL_HKDF_MODE:

        kctx->mode = p1;

        return 1;

    case EVP_PKEY_CTRL_HKDF_SALT:

        if (p1 == 0 || p2 == NULL)

            return 1;

        if (p1 < 0)

            return 0;

        if (kctx->salt != NULL)

            OPENSSL_clear_free(kctx->salt, kctx->salt_len);

        kctx->salt = OPENSSL_memdup(p2, p1);

        if (kctx->salt == NULL)

            return 0;

        kctx->salt_len = p1;

        return 1;

    case EVP_PKEY_CTRL_HKDF_KEY:

        if (p1 < 0)

            return 0;

        if (kctx->key != NULL)

            OPENSSL_clear_free(kctx->key, kctx->key_len);

        kctx->key = OPENSSL_memdup(p2, p1);

        if (kctx->key == NULL)

            return 0;

        kctx->key_len  = p1;

        return 1;

    case EVP_PKEY_CTRL_HKDF_INFO:

        if (p1 == 0 || p2 == NULL)

            return 1;

        if (p1 < 0 || p1 > (int)(HKDF_MAXBUF - kctx->info_len))

            return 0;

        memcpy(kctx->info + kctx->info_len, p2, p1);

        kctx->info_len += p1;

        return 1;

    default:

        return -2;

    }

}

static int pkey_hkdf_ctrl_str(EVP_PKEY_CTX *ctx, const char *type,

                              const char *value)

{

    if (strcmp(type, "mode") == 0) {

        int mode;

        if (strcmp(value, "EXTRACT_AND_EXPAND") == 0)

            mode = EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND;

        else if (strcmp(value, "EXTRACT_ONLY") == 0)

            mode = EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY;

        else if (strcmp(value, "EXPAND_ONLY") == 0)

            mode = EVP_PKEY_HKDEF_MODE_EXPAND_ONLY;

        else

            return 0;

        return EVP_PKEY_CTX_hkdf_mode(ctx, mode);

    }

    if (strcmp(type, "md") == 0)

        return EVP_PKEY_CTX_md(ctx, EVP_PKEY_OP_DERIVE,

                               EVP_PKEY_CTRL_HKDF_MD, value);

    if (strcmp(type, "salt") == 0)

        return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_SALT, value);

    if (strcmp(type, "hexsalt") == 0)

        return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_SALT, value);

    if (strcmp(type, "key") == 0)

        return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_KEY, value);

    if (strcmp(type, "hexkey") == 0)

        return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_KEY, value);

    if (strcmp(type, "info") == 0)

        return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_INFO, value);

    if (strcmp(type, "hexinfo") == 0)

        return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_INFO, value);

    KDFerr(KDF_F_PKEY_HKDF_CTRL_STR, KDF_R_UNKNOWN_PARAMETER_TYPE);

    return -2;

}

static int pkey_hkdf_derive(EVP_PKEY_CTX *ctx, unsigned char *key,

                            size_t *keylen)

{

    HKDF_PKEY_CTX *kctx = ctx->data;

    if (kctx->md == NULL) {

        KDFerr(KDF_F_PKEY_HKDF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);

        return 0;

    }

    if (kctx->key == NULL) {

        KDFerr(KDF_F_PKEY_HKDF_DERIVE, KDF_R_MISSING_KEY);

        return 0;

    }

    switch (kctx->mode) {

    case EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND:

        return HKDF(kctx->md, kctx->salt, kctx->salt_len, kctx->key,

                    kctx->key_len, kctx->info, kctx->info_len, key,

                    *keylen) != NULL;

    case EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY:

        if (key == NULL) {

            *keylen = EVP_MD_size(kctx->md);

            return 1;

        }

        return HKDF_Extract(kctx->md, kctx->salt, kctx->salt_len, kctx->key,

                            kctx->key_len, key, keylen) != NULL;

    case EVP_PKEY_HKDEF_MODE_EXPAND_ONLY:

        return HKDF_Expand(kctx->md, kctx->key, kctx->key_len, kctx->info,

                           kctx->info_len, key, *keylen) != NULL;

    default:

        return 0;

    }

}

const EVP_PKEY_METHOD hkdf_pkey_meth = {

    EVP_PKEY_HKDF,

    0,

    pkey_hkdf_init,

    0,

    pkey_hkdf_cleanup,

    0, 0,

    0, 0,

    0,

    0,

    0,

    0,

    0, 0,

    0, 0, 0, 0,

    0, 0,

    0, 0,

    0,

    pkey_hkdf_derive,

    pkey_hkdf_ctrl,

    pkey_hkdf_ctrl_str

};

static unsigned char *HKDF(const EVP_MD *evp_md,

                           const unsigned char *salt, size_t salt_len,

                           const unsigned char *key, size_t key_len,

                           const unsigned char *info, size_t info_len,

                           unsigned char *okm, size_t okm_len)

{

    unsigned char prk[EVP_MAX_MD_SIZE];

    unsigned char *ret;

    size_t prk_len;

    if (!HKDF_Extract(evp_md, salt, salt_len, key, key_len, prk, &prk_len))

        return NULL;

    ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);

    OPENSSL_cleanse(prk, sizeof(prk));

    return ret;

}

static unsigned char *HKDF_Extract(const EVP_MD *evp_md,

                                   const unsigned char *salt, size_t salt_len,

                                   const unsigned char *key, size_t key_len,

                                   unsigned char *prk, size_t *prk_len)

{

    unsigned int tmp_len;

    if (!HMAC(evp_md, salt, salt_len, key, key_len, prk, &tmp_len))

        return NULL;

    *prk_len = tmp_len;

    return prk;

}

static unsigned char *HKDF_Expand(const EVP_MD *evp_md,

                                  const unsigned char *prk, size_t prk_len,

                                  const unsigned char *info, size_t info_len,

                                  unsigned char *okm, size_t okm_len)

{

    HMAC_CTX *hmac;

    unsigned int i;

    unsigned char prev[EVP_MAX_MD_SIZE];

    size_t done_len = 0, dig_len = EVP_MD_size(evp_md);

    size_t n = okm_len / dig_len;

    if (okm_len % dig_len)

        n++;

    if (n > 255 || okm == NULL)

        return NULL;

    if ((hmac = HMAC_CTX_new()) == NULL)

        return NULL;

    if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))

        goto err;

    for (i = 1; i <= n; i++) {

        size_t copy_len;

        const unsigned char ctr = i;

        if (i > 1) {

            if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))

                goto err;

            if (!HMAC_Update(hmac, prev, dig_len))

                goto err;

        }

        if (!HMAC_Update(hmac, info, info_len))

            goto err;

        if (!HMAC_Update(hmac, &ctr, 1))

            goto err;

        if (!HMAC_Final(hmac, prev, NULL))

            goto err;

        copy_len = (done_len + dig_len > okm_len) ?

                       okm_len - done_len :

                       dig_len;

        memcpy(okm + done_len, prev, copy_len);

        done_len += copy_len;

    }

    HMAC_CTX_free(hmac);

    return okm;

 err:

    HMAC_CTX_free(hmac);

    return NULL;

}