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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 "old.h"
krb5_error_code
krb5int_old_decrypt(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
krb5_key key,
krb5_keyusage usage,
const krb5_data *ivec,
const krb5_data *input,
krb5_data *arg_output)
{
krb5_error_code ret;
size_t blocksize, hashsize, plainsize;
unsigned char *cksumdata, *cn;
krb5_data output, cksum, crcivec;
int alloced;
blocksize = enc->block_size;
hashsize = hash->hashsize;
plainsize = input->length - blocksize - hashsize;
if (arg_output->length < plainsize)
return(KRB5_BAD_MSIZE);
/* if there's enough space to work in the app buffer, use it,
otherwise allocate our own */
if ((cksumdata = (unsigned char *) malloc(hashsize)) == NULL)
return(ENOMEM);
if (arg_output->length < input->length) {
output.length = input->length;
if ((output.data = (char *) malloc(output.length)) == NULL) {
free(cksumdata);
return(ENOMEM);
}
alloced = 1;
} else {
output.length = input->length;
output.data = arg_output->data;
alloced = 0;
}
/* decrypt it */
/* save last ciphertext block in case we decrypt in place */
if (ivec != NULL && ivec->length == blocksize) {
cn = malloc(blocksize);
if (cn == NULL) {
ret = ENOMEM;
goto cleanup;
}
memcpy(cn, input->data + input->length - blocksize, blocksize);
} else
cn = NULL;
/* XXX this is gross, but I don't have much choice */
if ((key->keyblock.enctype == ENCTYPE_DES_CBC_CRC) && (ivec == 0)) {
crcivec.length = key->keyblock.length;
crcivec.data = (char *) key->keyblock.contents;
ivec = &crcivec;
}
if ((ret = ((*(enc->decrypt))(key, ivec, input, &output))))
goto cleanup;
/* verify the checksum */
memcpy(cksumdata, output.data+blocksize, hashsize);
memset(output.data+blocksize, 0, hashsize);
cksum.length = hashsize;
cksum.data = output.data+blocksize;
if ((ret = ((*(hash->hash))(1, &output, &cksum))))
goto cleanup;
if (memcmp(cksum.data, cksumdata, cksum.length) != 0) {
ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
goto cleanup;
}
/* copy the plaintext around */
if (alloced) {
memcpy(arg_output->data, output.data+blocksize+hashsize,
plainsize);
} else {
memmove(arg_output->data, arg_output->data+blocksize+hashsize,
plainsize);
}
arg_output->length = plainsize;
/* update ivec */
if (cn != NULL)
memcpy(ivec->data, cn, blocksize);
ret = 0;
cleanup:
if (alloced) {
memset(output.data, 0, output.length);
free(output.data);
}
if (cn != NULL)
free(cn);
memset(cksumdata, 0, hashsize);
free(cksumdata);
return(ret);
}
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