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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/crypto/krb/enc_dk_cmac.c - Derived-key enctype functions using CMAC */
/*
* Copyright 2008, 2009, 2010 by the Massachusetts Institute of Technology.
* All Rights Reserved.
*
* Export of this software from the United States of America may
* require a specific license from the United States Government.
* It is the responsibility of any person or organization contemplating
* export to obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. Furthermore if you modify this software you must label
* your software as modified software and not distribute it in such a
* fashion that it might be confused with the original M.I.T. software.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
#include "crypto_int.h"
#define K5CLENGTH 5 /* 32 bit net byte order integer + one byte seed */
/* AEAD */
unsigned int
krb5int_camellia_crypto_length(const struct krb5_keytypes *ktp,
krb5_cryptotype type)
{
switch (type) {
case KRB5_CRYPTO_TYPE_HEADER:
return ktp->enc->block_size;
case KRB5_CRYPTO_TYPE_PADDING:
return 0;
case KRB5_CRYPTO_TYPE_TRAILER:
case KRB5_CRYPTO_TYPE_CHECKSUM:
return ktp->enc->block_size;
default:
assert(0 && "bad type passed to krb5int_camellia_crypto_length");
return 0;
}
}
/* Derive encryption and integrity keys for CMAC-using enctypes. */
static krb5_error_code
derive_keys(const struct krb5_enc_provider *enc, krb5_key key,
krb5_keyusage usage, krb5_key *ke_out, krb5_key *ki_out)
{
krb5_error_code ret;
unsigned char buf[K5CLENGTH];
krb5_data constant = make_data(buf, K5CLENGTH);
krb5_key ke, ki;
*ke_out = *ki_out = NULL;
/* Derive the encryption key. */
store_32_be(usage, buf);
buf[4] = 0xAA;
ret = krb5int_derive_key(enc, key, &ke, &constant, DERIVE_SP800_108_CMAC);
if (ret != 0)
return ret;
/* Derive the integrity key. */
buf[4] = 0x55;
ret = krb5int_derive_key(enc, key, &ki, &constant, DERIVE_SP800_108_CMAC);
if (ret != 0) {
krb5_k_free_key(NULL, ke);
return ret;
}
*ke_out = ke;
*ki_out = ki;
return 0;
}
krb5_error_code
krb5int_dk_cmac_encrypt(const struct krb5_keytypes *ktp, krb5_key key,
krb5_keyusage usage, const krb5_data *ivec,
krb5_crypto_iov *data, size_t num_data)
{
const struct krb5_enc_provider *enc = ktp->enc;
krb5_error_code ret;
krb5_crypto_iov *header, *trailer, *padding;
krb5_data cksum = empty_data();
krb5_key ke = NULL, ki = NULL;
/* E(Confounder | Plaintext | Pad) | Checksum */
/* Validate header and trailer lengths, and zero out padding length. */
header = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_HEADER);
if (header == NULL || header->data.length < enc->block_size)
return KRB5_BAD_MSIZE;
trailer = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_TRAILER);
if (trailer == NULL || trailer->data.length < enc->block_size)
return KRB5_BAD_MSIZE;
padding = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_PADDING);
if (padding != NULL)
padding->data.length = 0;
/* Derive the encryption and integrity keys. */
ret = derive_keys(enc, key, usage, &ke, &ki);
if (ret != 0)
goto cleanup;
/* Generate confounder. */
header->data.length = enc->block_size;
ret = krb5_c_random_make_octets(NULL, &header->data);
if (ret != 0)
goto cleanup;
/* Checksum the plaintext. */
ret = krb5int_cmac_checksum(enc, ki, data, num_data, &trailer->data);
if (ret != 0)
goto cleanup;
/* Encrypt the plaintext (header | data | padding) */
ret = enc->encrypt(ke, ivec, data, num_data);
if (ret != 0)
goto cleanup;
cleanup:
krb5_k_free_key(NULL, ke);
krb5_k_free_key(NULL, ki);
zapfree(cksum.data, cksum.length);
return ret;
}
krb5_error_code
krb5int_dk_cmac_decrypt(const struct krb5_keytypes *ktp, krb5_key key,
krb5_keyusage usage, const krb5_data *ivec,
krb5_crypto_iov *data, size_t num_data)
{
const struct krb5_enc_provider *enc = ktp->enc;
krb5_error_code ret;
krb5_crypto_iov *header, *trailer;
krb5_data cksum;
krb5_key ke = NULL, ki = NULL;
/* E(Confounder | Plaintext | Pad) | Checksum */
/* Validate header and trailer lengths. */
header = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_HEADER);
if (header == NULL || header->data.length != enc->block_size)
return KRB5_BAD_MSIZE;
trailer = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_TRAILER);
if (trailer == NULL || trailer->data.length != enc->block_size)
return KRB5_BAD_MSIZE;
/* Derive the encryption and integrity keys. */
ret = derive_keys(enc, key, usage, &ke, &ki);
if (ret != 0)
goto cleanup;
/* Decrypt the plaintext (header | data | padding). */
ret = enc->decrypt(ke, ivec, data, num_data);
if (ret != 0)
goto cleanup;
/* Verify the hash. */
ret = alloc_data(&cksum, enc->block_size);
if (ret != 0)
goto cleanup;
ret = krb5int_cmac_checksum(enc, ki, data, num_data, &cksum);
if (ret != 0)
goto cleanup;
if (!data_eq(cksum, trailer->data))
ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
cleanup:
krb5_k_free_key(NULL, ke);
krb5_k_free_key(NULL, ki);
zapfree(cksum.data, cksum.length);
return ret;
}
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