/*

 * Copyright 2018-2019 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 <stdarg.h>

#include <string.h>

#include <openssl/des.h>

#include <openssl/evp.h>

#include <openssl/kdf.h>

#include "internal/cryptlib.h"

#include "crypto/evp.h"

#include "kdf_local.h"

/* KRB5 KDF defined in RFC 3961, Section 5.1 */

static int KRB5KDF(const EVP_CIPHER *cipher,

                   const unsigned char *key, size_t key_len,

                   const unsigned char *constant, size_t constant_len,

                   unsigned char *okey, size_t okey_len);

struct evp_kdf_impl_st {

    const EVP_CIPHER *cipher;

    unsigned char *key;

    size_t key_len;

    unsigned char *constant;

    size_t constant_len;

};

static void krb5kdf_reset(EVP_KDF_IMPL *ctx);

static EVP_KDF_IMPL *krb5kdf_new(void)

{

    EVP_KDF_IMPL *ctx;

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

        KDFerr(KDF_F_KBKDF_NEW, ERR_R_MALLOC_FAILURE);

    return ctx;

}

static void krb5kdf_free(EVP_KDF_IMPL *ctx)

{

    krb5kdf_reset(ctx);

    OPENSSL_free(ctx);

}

static void krb5kdf_reset(EVP_KDF_IMPL *ctx)

{

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

    OPENSSL_clear_free(ctx->constant, ctx->constant_len);

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

}

static int krb5kdf_derive(EVP_KDF_IMPL *ctx, unsigned char *key,

                              size_t keylen)

{

    if (ctx->cipher == NULL) {

        KDFerr(KDF_F_KRB5KDF_DERIVE, KDF_R_MISSING_CIPHER);

        return 0;

    }

    if (ctx->key == NULL) {

        KDFerr(KDF_F_KRB5KDF_DERIVE, KDF_R_MISSING_KEY);

        return 0;

    }

    if (ctx->constant == NULL) {

        KDFerr(KDF_F_KRB5KDF_DERIVE, KDF_R_MISSING_CONSTANT);

        return 0;

    }

    return KRB5KDF(ctx->cipher, ctx->key, ctx->key_len,

                   ctx->constant, ctx->constant_len,

                   key, keylen);

}

static size_t krb5kdf_size(EVP_KDF_IMPL *ctx)

{

    if (ctx->cipher != NULL)

        return EVP_CIPHER_key_length(ctx->cipher);

    else

        return EVP_MAX_KEY_LENGTH;

}

static int krb5kdf_parse_buffer_arg(unsigned char **dst, size_t *dst_len,

                                       va_list args)

{

    const unsigned char *p;

    size_t len;

    p = va_arg(args, const unsigned char *);

    len = va_arg(args, size_t);

    OPENSSL_clear_free(*dst, *dst_len);

    if (len == 0) {

        *dst = NULL;

        *dst_len = 0;

        return 1;

    }

    *dst = OPENSSL_memdup(p, len);

    if (*dst == NULL)

        return 0;

    *dst_len = len;

    return 1;

}

static int krb5kdf_ctrl(EVP_KDF_IMPL *ctx, int cmd, va_list args)

{

    switch (cmd) {

    case EVP_KDF_CTRL_SET_CIPHER:

        ctx->cipher = va_arg(args, const EVP_CIPHER *);

        if (ctx->cipher == NULL)

            return 0;

        return 1;

    case EVP_KDF_CTRL_SET_KEY:

        return krb5kdf_parse_buffer_arg(&ctx->key,

                                      &ctx->key_len, args);

    case EVP_KDF_CTRL_SET_KRB5KDF_CONSTANT:

        return krb5kdf_parse_buffer_arg(&ctx->constant,

                                           &ctx->constant_len, args);

    default:

        return -2;

    }

}

static int krb5kdf_ctrl_str(EVP_KDF_IMPL *ctx, const char *type,

                               const char *value)

{

    if (value == NULL) {

        KDFerr(KDF_F_KDF_SSHKDF_CTRL_STR, KDF_R_VALUE_MISSING);

        return 0;

    }

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

        return kdf_cipher2ctrl(ctx, krb5kdf_ctrl, EVP_KDF_CTRL_SET_CIPHER, value);

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

        return kdf_str2ctrl(ctx, krb5kdf_ctrl,

                            EVP_KDF_CTRL_SET_KEY, value);

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

        return kdf_hex2ctrl(ctx, krb5kdf_ctrl,

                            EVP_KDF_CTRL_SET_KEY, value);

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

        return kdf_str2ctrl(ctx, krb5kdf_ctrl,

                            EVP_KDF_CTRL_SET_KRB5KDF_CONSTANT, value);

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

        return kdf_hex2ctrl(ctx, krb5kdf_ctrl,

                            EVP_KDF_CTRL_SET_KRB5KDF_CONSTANT, value);

    KDFerr(KDF_F_KBKDF_CTRL_STR, KDF_R_UNKNOWN_PARAMETER_TYPE);

    return -2;

}

#ifndef OPENSSL_NO_DES

/*

 * DES3 is a special case, it requires a random-to-key function and its

 * input truncated to 21 bytes of the 24 produced by the cipher.

 * See RFC3961 6.3.1

 */

static int fixup_des3_key(unsigned char *key)

{

    unsigned char *cblock;

    int i, j;

    for (i = 2; i >= 0; i--) {

        cblock = &key[i * 8];

        memmove(cblock, &key[i * 7], 7);

        cblock[7] = 0;

        for (j = 0; j < 7; j++)

            cblock[7] |= (cblock[j] & 1) << (j + 1);

        DES_set_odd_parity((DES_cblock *)cblock);

    }

    /* fail if keys are such that triple des degrades to single des */

    if (CRYPTO_memcmp(&key[0], &key[8], 8) == 0 ||

        CRYPTO_memcmp(&key[8], &key[16], 8) == 0) {

        return 0;

    }

    return 1;

}

#endif

/*

 * N-fold(K) where blocksize is N, and constant_len is K

 * Note: Here |= denotes concatenation

 *

 * L = lcm(N,K)

 * R = L/K

 *

 * for r: 1 -> R

 *   s |= constant rot 13*(r-1))

 *

 * block = 0

 * for k: 1 -> K

 *   block += s[N(k-1)..(N-1)k] (one's complement addition)

 *

 * Optimizing for space we compute:

 * for each l in L-1 -> 0:

 *   s[l] = (constant rot 13*(l/K))[l%k]

 *   block[l % N] += s[l] (with carry)

 * finally add carry if any

 */

static void n_fold(unsigned char *block, unsigned int blocksize,

                   const unsigned char *constant, size_t constant_len)

{

    unsigned int tmp, gcd, remainder, lcm, carry;

    int b, l;

    if (constant_len == blocksize) {

        memcpy(block, constant, constant_len);

        return;

    }

    /* Least Common Multiple of lengths: LCM(a,b)*/

    gcd = blocksize;

    remainder = constant_len;

    /* Calculate Great Common Divisor first GCD(a,b) */

    while (remainder != 0) {

        tmp = gcd % remainder;

        gcd = remainder;

        remainder = tmp;

    }

    /* resulting a is the GCD, LCM(a,b) = |a*b|/GCD(a,b) */

    lcm = blocksize * constant_len / gcd;

    /* now spread out the bits */

    memset(block, 0, blocksize);

    /* last to first to be able to bring carry forward */

    carry = 0;

    for (l = lcm - 1; l >= 0; l--) {

        unsigned int rotbits, rshift, rbyte;

        /* destination byte in block is l % N */

        b = l % blocksize;

        /* Our virtual s buffer is R = L/K long (K = constant_len) */

        /* So we rotate backwards from R-1 to 0 (none) rotations */

        rotbits = 13 * (l / constant_len);

        /* find the byte on s where rotbits falls onto */

        rbyte = l - (rotbits / 8);

        /* calculate how much shift on that byte */

        rshift = rotbits & 0x07;

        /* rbyte % constant_len gives us the unrotated byte in the

         * constant buffer, get also the previous byte then

         * appropriately shift them to get the rotated byte we need */

        tmp = (constant[(rbyte-1) % constant_len] << (8 - rshift)

               | constant[rbyte % constant_len] >> rshift)

              & 0xff;

        /* add with carry to any value placed by previous passes */

        tmp += carry + block[b];

        block[b] = tmp & 0xff;

        /* save any carry that may be left */

        carry = tmp >> 8;

    }

    /* if any carry is left at the end, add it through the number */

    for (b = blocksize - 1; b >= 0 && carry != 0; b--) {

        carry += block[b];

        block[b] = carry & 0xff;

        carry >>= 8;

    }

}

static int cipher_init(EVP_CIPHER_CTX *ctx,

                       const EVP_CIPHER *cipher,

                       const unsigned char *key, size_t key_len)

{

    int klen, ret;

    ret = EVP_EncryptInit_ex(ctx, cipher, NULL, key, NULL);

    if (!ret)

        goto out;

    /* set the key len for the odd variable key len cipher */

    klen = EVP_CIPHER_CTX_key_length(ctx);

    if (key_len != (size_t)klen) {

        ret = EVP_CIPHER_CTX_set_key_length(ctx, key_len);

        if (!ret)

            goto out;

    }

    /* we never want padding, either the length requested is a multiple of

     * the cipher block size or we are passed a cipher that can cope with

     * partial blocks via techniques like cipher text stealing */

    ret = EVP_CIPHER_CTX_set_padding(ctx, 0);

    if (!ret)

        goto out;

out:

    return ret;

}

static int KRB5KDF(const EVP_CIPHER *cipher,

                   const unsigned char *key, size_t key_len,

                   const unsigned char *constant, size_t constant_len,

                   unsigned char *okey, size_t okey_len)

{

    EVP_CIPHER_CTX *ctx = NULL;

    unsigned char block[EVP_MAX_BLOCK_LENGTH * 2];

    unsigned char *plainblock, *cipherblock;

    size_t blocksize;

    size_t cipherlen;

    size_t osize;

    int des3_no_fixup = 0;

    int ret;

    if (key_len != okey_len) {

        /* special case for 3des, where the caller may be requesting

         * the random raw key, instead of the fixed up key  */

        if (EVP_CIPHER_nid(cipher) == NID_des_ede3_cbc &&

            key_len == 24 && okey_len == 21) {

                des3_no_fixup = 1;

        } else {

            KDFerr(KDF_F_KRB5KDF, KDF_R_WRONG_OUTPUT_BUFFER_SIZE);

            return 0;

        }

    }

    ctx = EVP_CIPHER_CTX_new();

    if (ctx == NULL)

        return 0;

    ret = cipher_init(ctx, cipher, key, key_len);

    if (!ret)

        goto out;

    /* Initialize input block */

    blocksize = EVP_CIPHER_CTX_block_size(ctx);

    if (constant_len == 0 || constant_len > blocksize) {

        KDFerr(KDF_F_KRB5KDF, KDF_R_INVALID_CONSTANT_LENGTH);

        ret = 0;

        goto out;

    }

    n_fold(block, blocksize, constant, constant_len);

    plainblock = block;

    cipherblock = block + EVP_MAX_BLOCK_LENGTH;

    for (osize = 0; osize < okey_len; osize += cipherlen) {

        int olen;

        ret = EVP_EncryptUpdate(ctx, cipherblock, &olen,

                                plainblock, blocksize);

        if (!ret)

            goto out;

        cipherlen = olen;

        ret = EVP_EncryptFinal_ex(ctx, cipherblock, &olen);

        if (!ret)

            goto out;

        if (olen != 0) {

            KDFerr(KDF_F_KRB5KDF, KDF_R_WRONG_FINAL_BLOCK_LENGTH);

            ret = 0;

            goto out;

        }

        /* write cipherblock out */

        if (cipherlen > okey_len - osize)

            cipherlen = okey_len - osize;

        memcpy(okey + osize, cipherblock, cipherlen);

        if (okey_len > osize + cipherlen) {

            /* we need to reinitialize cipher context per spec */

            ret = EVP_CIPHER_CTX_reset(ctx);

            if (!ret)

                goto out;

            ret = cipher_init(ctx, cipher, key, key_len);

            if (!ret)

                goto out;

            /* also swap block offsets so last ciphertext becomes new

             * plaintext */

            plainblock = cipherblock;

            if (cipherblock == block) {

                cipherblock += EVP_MAX_BLOCK_LENGTH;

            } else {

                cipherblock = block;

            }

        }

    }

#ifndef OPENSSL_NO_DES

    if (EVP_CIPHER_nid(cipher) == NID_des_ede3_cbc && !des3_no_fixup) {

        ret = fixup_des3_key(okey);

        if (!ret) {

            KDFerr(KDF_F_KRB5KDF, KDF_R_FAILED_TO_GENERATE_KEY);

            goto out;

        }

    }

#endif

    ret = 1;

out:

    EVP_CIPHER_CTX_free(ctx);

    OPENSSL_cleanse(block, EVP_MAX_BLOCK_LENGTH * 2);

    return ret;

}

const EVP_KDF_METHOD krb5kdf_kdf_meth = {

    EVP_KDF_KRB5KDF,

    krb5kdf_new,

    krb5kdf_free,

    krb5kdf_reset,

    krb5kdf_ctrl,

    krb5kdf_ctrl_str,

    krb5kdf_size,

    krb5kdf_derive,

};