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/*
* Copyright (C) 1998 by the FundsXpress, INC.
*
* 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 FundsXpress. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. FundsXpress makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#include "k5-int.h"
#include "dk.h"
#define K5CLENGTH 5 /* 32 bit net byte order integer + one byte seed */
static krb5_error_code
krb5_dk_decrypt_maybe_trunc_hmac(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *key,
krb5_keyusage usage,
const krb5_data *ivec,
const krb5_data *input,
krb5_data *output,
size_t hmacsize,
int ivec_mode);
krb5_error_code
krb5_dk_decrypt(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *key, krb5_keyusage usage,
const krb5_data *ivec, const krb5_data *input,
krb5_data *output)
{
return krb5_dk_decrypt_maybe_trunc_hmac(enc, hash, key, usage,
ivec, input, output, 0, 0);
}
krb5_error_code
krb5int_aes_dk_decrypt(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *key, krb5_keyusage usage,
const krb5_data *ivec, const krb5_data *input,
krb5_data *output)
{
return krb5_dk_decrypt_maybe_trunc_hmac(enc, hash, key, usage,
ivec, input, output, 96 / 8, 1);
}
static krb5_error_code
krb5_dk_decrypt_maybe_trunc_hmac(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *key, krb5_keyusage usage,
const krb5_data *ivec, const krb5_data *input,
krb5_data *output, size_t hmacsize,
int ivec_mode)
{
krb5_error_code ret;
size_t hashsize, blocksize, keybytes, keylength, enclen, plainlen;
unsigned char *plaindata, *kedata, *kidata, *cksum, *cn;
krb5_keyblock ke, ki;
krb5_data d1, d2;
unsigned char constantdata[K5CLENGTH];
/* allocate and set up ciphertext and to-be-derived keys */
hashsize = hash->hashsize;
blocksize = enc->block_size;
keybytes = enc->keybytes;
keylength = enc->keylength;
if (hmacsize == 0)
hmacsize = hashsize;
else if (hmacsize > hashsize)
return KRB5KRB_AP_ERR_BAD_INTEGRITY;
enclen = input->length - hmacsize;
if ((kedata = (unsigned char *) malloc(keylength)) == NULL)
return(ENOMEM);
if ((kidata = (unsigned char *) malloc(keylength)) == NULL) {
free(kedata);
return(ENOMEM);
}
if ((plaindata = (unsigned char *) malloc(enclen)) == NULL) {
free(kidata);
free(kedata);
return(ENOMEM);
}
if ((cksum = (unsigned char *) malloc(hashsize)) == NULL) {
free(plaindata);
free(kidata);
free(kedata);
return(ENOMEM);
}
ke.contents = kedata;
ke.length = keylength;
ki.contents = kidata;
ki.length = keylength;
/* derive the keys */
d1.data = (char *) constantdata;
d1.length = K5CLENGTH;
store_32_be(usage, constantdata);
d1.data[4] = (char) 0xAA;
if ((ret = krb5_derive_key(enc, key, &ke, &d1)) != 0)
goto cleanup;
d1.data[4] = 0x55;
if ((ret = krb5_derive_key(enc, key, &ki, &d1)) != 0)
goto cleanup;
/* decrypt the ciphertext */
d1.length = enclen;
d1.data = input->data;
d2.length = enclen;
d2.data = (char *) plaindata;
if ((ret = ((*(enc->decrypt))(&ke, ivec, &d1, &d2))) != 0)
goto cleanup;
if (ivec != NULL && ivec->length == blocksize) {
if (ivec_mode == 0)
cn = (unsigned char *) d1.data + d1.length - blocksize;
else if (ivec_mode == 1) {
int nblocks = (d1.length + blocksize - 1) / blocksize;
cn = d1.data + blocksize * (nblocks - 2);
} else
abort();
} else
cn = NULL;
/* verify the hash */
d1.length = hashsize;
d1.data = (char *) cksum;
if ((ret = krb5_hmac(hash, &ki, 1, &d2, &d1)) != 0)
goto cleanup;
if (memcmp(cksum, input->data+enclen, hmacsize) != 0) {
ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
goto cleanup;
}
/* because this encoding isn't self-describing wrt length, the
best we can do here is to compute the length minus the
confounder. */
plainlen = enclen - blocksize;
if (output->length < plainlen)
return(KRB5_BAD_MSIZE);
output->length = plainlen;
memcpy(output->data, d2.data+blocksize, output->length);
if (cn != NULL)
memcpy(ivec->data, cn, blocksize);
ret = 0;
cleanup:
memset(kedata, 0, keylength);
memset(kidata, 0, keylength);
memset(plaindata, 0, enclen);
memset(cksum, 0, hashsize);
free(cksum);
free(plaindata);
free(kidata);
free(kedata);
return(ret);
}
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