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 = empty_data();
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 (k5_bcmp(cksum.data, trailer->data.data, enc->block_size) != 0)
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;
}
static krb5_error_code
krb5int_raw_decrypt_iov(const struct krb5_aead_provider *aead,
const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *key,
krb5_keyusage usage,
const krb5_data *ivec,
krb5_crypto_iov *data,
size_t num_data)
{
krb5_error_code ret;
size_t i;
unsigned int blocksize = 0; /* careful, this is enc block size not confounder len */
unsigned int cipherlen = 0;
if (krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_STREAM) != NULL) {
return krb5int_c_iov_decrypt_stream(aead, enc, hash, key,
usage, ivec, data, num_data);
}
/* E(Confounder | Plaintext | Pad) | Checksum */
ret = aead->crypto_length(aead, enc, hash, KRB5_CRYPTO_TYPE_PADDING, &blocksize);
if (ret != 0)
return ret;
for (i = 0; i < num_data; i++) {
const krb5_crypto_iov *iov = &data[i];
if (ENCRYPT_DATA_IOV(iov))
cipherlen += iov->data.length;
}
if (blocksize == 0) {
/* Check for correct input length in CTS mode */
if (enc->block_size != 0 && cipherlen < enc->block_size)
return KRB5_BAD_MSIZE;
} else {
/* Check that the input data is correctly padded */
if ((cipherlen % blocksize) != 0)
return KRB5_BAD_MSIZE;
}
/* Validate header and trailer lengths */
/* derive the keys */
/* decrypt the plaintext (header | data | padding) */
assert(enc->decrypt_iov != NULL);
ret = enc->decrypt_iov(key, ivec, data, num_data); /* will update ivec */
return ret;
}
krb5_error_code KRB5_CALLCONV
krb5_c_make_checksum_iov(krb5_context context,
krb5_cksumtype cksumtype,
const krb5_keyblock *key,
krb5_keyusage usage,
krb5_crypto_iov *data,
size_t num_data)
{
unsigned int i;
size_t cksumlen;
krb5_error_code ret;
krb5_data cksum_data;
krb5_crypto_iov *checksum;
for (i = 0; i < krb5_cksumtypes_length; i++) {
if (krb5_cksumtypes_list[i].ctype == cksumtype)
break;
}
if (i == krb5_cksumtypes_length)
return(KRB5_BAD_ENCTYPE);
if (krb5_cksumtypes_list[i].keyhash != NULL)
cksum_data.length = krb5_cksumtypes_list[i].keyhash->hashsize;
else
cksum_data.length = krb5_cksumtypes_list[i].hash->hashsize;
if (krb5_cksumtypes_list[i].trunc_size != 0)
cksumlen = krb5_cksumtypes_list[i].trunc_size;
else
cksumlen = cksum_data.length;
checksum = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_CHECKSUM);
if (checksum == NULL || checksum->data.length < cksumlen)
return(KRB5_BAD_MSIZE);
cksum_data.data = malloc(cksum_data.length);
if (cksum_data.data == NULL)
return(ENOMEM);
ret = krb5int_c_make_checksum_iov(&krb5_cksumtypes_list[i],
key, usage, data, num_data,
&cksum_data);
if (ret == 0) {
memcpy(checksum->data.data, cksum_data.data, cksumlen);
checksum->data.length = cksumlen;
}
free(cksum_data.data);
return(ret);
}
static krb5_error_code
krb5int_raw_encrypt_iov(const struct krb5_aead_provider *aead,
const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *key,
krb5_keyusage usage,
const krb5_data *ivec,
krb5_crypto_iov *data,
size_t num_data)
{
krb5_error_code ret;
krb5_crypto_iov *padding;
size_t i;
unsigned int blocksize = 0;
unsigned int plainlen = 0;
unsigned int padsize = 0;
ret = aead->crypto_length(aead, enc, hash, KRB5_CRYPTO_TYPE_PADDING, &blocksize);
if (ret != 0)
return ret;
for (i = 0; i < num_data; i++) {
krb5_crypto_iov *iov = &data[i];
if (iov->flags == KRB5_CRYPTO_TYPE_DATA)
plainlen += iov->data.length;
}
if (blocksize != 0) {
/* Check that the input data is correctly padded */
if (plainlen % blocksize)
padsize = blocksize - (plainlen % blocksize);
}
padding = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_PADDING);
if (padsize && (padding == NULL || padding->data.length < padsize))
return KRB5_BAD_MSIZE;
if (padding != NULL) {
memset(padding->data.data, 0, padsize);
padding->data.length = padsize;
}
assert(enc->encrypt_iov != NULL);
ret = enc->encrypt_iov(key, ivec, data, num_data); /* will update ivec */
return ret;
}
krb5_error_code KRB5_CALLCONV
krb5_k_decrypt_iov(krb5_context context, krb5_key key, krb5_keyusage usage,
const krb5_data *cipher_state, krb5_crypto_iov *data,
size_t num_data)
{
const struct krb5_keytypes *ktp;
ktp = find_enctype(key->keyblock.enctype);
if (ktp == NULL)
return KRB5_BAD_ENCTYPE;
if (krb5int_c_locate_iov(data, num_data,
KRB5_CRYPTO_TYPE_STREAM) != NULL) {
return krb5int_c_iov_decrypt_stream(ktp, key, usage, cipher_state,
data, num_data);
}
return ktp->decrypt(ktp, key, usage, cipher_state, data, num_data);
}
static krb5_error_code
krb5int_arcfour_encrypt_iov(const struct krb5_aead_provider *aead,
const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *key,
krb5_keyusage usage,
const krb5_data *ivec,
krb5_crypto_iov *data,
size_t num_data)
{
krb5_error_code ret;
krb5_crypto_iov *header, *trailer;
krb5_keyblock k1, k2, k3;
krb5_data d1, d2, d3;
krb5_data checksum, confounder, header_data;
krb5_keyusage ms_usage;
char salt_data[14];
krb5_data salt;
size_t i;
d1.length = d2.length = d3.length = 0;
d1.data = d2.data = d3.data = NULL;
/*
* Caller must have provided space for the header, padding
* and trailer; per RFC 4757 we will arrange it as:
*
* Checksum | E(Confounder | Plaintext)
*/
header = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_HEADER);
if (header == NULL ||
header->data.length < hash->hashsize + CONFOUNDERLENGTH)
return KRB5_BAD_MSIZE;
header_data = header->data;
/* Trailer may be absent */
trailer = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_TRAILER);
if (trailer != NULL)
trailer->data.length = 0;
/* Ensure that there is no padding */
for (i = 0; i < num_data; i++) {
if (data[i].flags == KRB5_CRYPTO_TYPE_PADDING)
data[i].data.length = 0;
}
ret = alloc_derived_key(enc, &k1, &d1, key);
if (ret != 0)
goto cleanup;
ret = alloc_derived_key(enc, &k2, &d2, key);
if (ret != 0)
goto cleanup;
ret = alloc_derived_key(enc, &k3, &d3, key);
if (ret != 0)
goto cleanup;
/* Begin the encryption, compute K1 */
salt.data = salt_data;
salt.length = sizeof(salt_data);
ms_usage = krb5int_arcfour_translate_usage(usage);
if (key->enctype == ENCTYPE_ARCFOUR_HMAC_EXP) {
strncpy(salt.data, krb5int_arcfour_l40, salt.length);
store_32_le(ms_usage, salt.data + 10);
} else {
salt.length = 4;
store_32_le(ms_usage, salt.data);
}
ret = krb5_hmac(hash, key, 1, &salt, &d1);
if (ret != 0)
goto cleanup;
memcpy(k2.contents, k1.contents, k2.length);
if (key->enctype == ENCTYPE_ARCFOUR_HMAC_EXP)
memset(k1.contents + 7, 0xAB, 9);
header->data.length = hash->hashsize + CONFOUNDERLENGTH;
confounder.data = header->data.data + hash->hashsize;
confounder.length = CONFOUNDERLENGTH;
ret = krb5_c_random_make_octets(0, &confounder);
if (ret != 0)
goto cleanup;
checksum.data = header->data.data;
checksum.length = hash->hashsize;
/* Adjust pointers so confounder is at start of header */
header->data.length -= hash->hashsize;
header->data.data += hash->hashsize;
ret = krb5int_hmac_iov(hash, &k2, data, num_data, &checksum);
if (ret != 0)
goto cleanup;
ret = krb5_hmac(hash, &k1, 1, &checksum, &d3);
if (ret != 0)
goto cleanup;
ret = enc->encrypt_iov(&k3, ivec, data, num_data);
if (ret != 0)
goto cleanup;
cleanup:
header->data = header_data; /* restore header pointers */
if (d1.data != NULL) {
memset(d1.data, 0, d1.length);
free(d1.data);
}
if (d2.data != NULL) {
memset(d2.data, 0, d2.length);
free(d2.data);
}
if (d3.data != NULL) {
memset(d3.data, 0, d3.length);
free(d3.data);
}
return ret;
}
static krb5_error_code
krb5int_arcfour_decrypt_iov(const struct krb5_aead_provider *aead,
const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *key,
krb5_keyusage usage,
const krb5_data *ivec,
krb5_crypto_iov *data,
size_t num_data)
{
krb5_error_code ret;
krb5_crypto_iov *header, *trailer;
krb5_keyblock k1, k2, k3;
krb5_data d1, d2, d3;
krb5_data checksum, header_data;
krb5_keyusage ms_usage;
char salt_data[14];
krb5_data salt;
d1.length = d2.length = d3.length = 0;
d1.data = d2.data = d3.data = NULL;
header = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_HEADER);
if (header == NULL ||
header->data.length != hash->hashsize + CONFOUNDERLENGTH)
return KRB5_BAD_MSIZE;
header_data = header->data;
trailer = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_TRAILER);
if (trailer != NULL && trailer->data.length != 0)
return KRB5_BAD_MSIZE;
ret = alloc_derived_key(enc, &k1, &d1, key);
if (ret != 0)
goto cleanup;
ret = alloc_derived_key(enc, &k2, &d2, key);
if (ret != 0)
goto cleanup;
ret = alloc_derived_key(enc, &k3, &d3, key);
if (ret != 0)
goto cleanup;
/* Begin the decryption, compute K1 */
salt.data = salt_data;
salt.length = sizeof(salt_data);
ms_usage = krb5int_arcfour_translate_usage(usage);
if (key->enctype == ENCTYPE_ARCFOUR_HMAC_EXP) {
strncpy(salt.data, krb5int_arcfour_l40, salt.length);
store_32_le(ms_usage, (unsigned char *)salt.data + 10);
} else {
salt.length = 4;
store_32_le(ms_usage, (unsigned char *)salt.data);
}
ret = krb5_hmac(hash, key, 1, &salt, &d1);
if (ret != 0)
goto cleanup;
memcpy(k2.contents, k1.contents, k2.length);
if (key->enctype == ENCTYPE_ARCFOUR_HMAC_EXP)
memset(k1.contents + 7, 0xAB, 9);
checksum.data = header->data.data;
checksum.length = hash->hashsize;
/* Adjust pointers so confounder is at start of header */
header->data.length -= hash->hashsize;
header->data.data += hash->hashsize;
ret = krb5_hmac(hash, &k1, 1, &checksum, &d3);
if (ret != 0)
goto cleanup;
ret = enc->decrypt_iov(&k3, ivec, data, num_data);
if (ret != 0)
goto cleanup;
ret = krb5int_hmac_iov(hash, &k2, data, num_data, &d1);
if (ret != 0)
goto cleanup;
if (memcmp(checksum.data, d1.data, hash->hashsize) != 0) {
ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
goto cleanup;
}
cleanup:
header->data = header_data; /* restore header pointers */
if (d1.data != NULL) {
memset(d1.data, 0, d1.length);
free(d1.data);
}
if (d2.data != NULL) {
memset(d2.data, 0, d2.length);
free(d2.data);
}
if (d3.data != NULL) {
memset(d3.data, 0, d3.length);
free(d3.data);
}
return ret;
}
krb5_error_code
krb5int_arcfour_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;
const struct krb5_hash_provider *hash = ktp->hash;
krb5_error_code ret;
krb5_crypto_iov *header, *trailer;
krb5_keyblock *usage_keyblock = NULL, *enc_keyblock = NULL;
krb5_data checksum, header_data, comp_checksum = empty_data();
header = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_HEADER);
if (header == NULL ||
header->data.length != hash->hashsize + CONFOUNDERLENGTH)
return KRB5_BAD_MSIZE;
header_data = header->data;
trailer = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_TRAILER);
if (trailer != NULL && trailer->data.length != 0)
return KRB5_BAD_MSIZE;
/* Allocate buffers. */
ret = alloc_data(&comp_checksum, hash->hashsize);
if (ret != 0)
goto cleanup;
ret = krb5int_c_init_keyblock(NULL, key->keyblock.enctype, enc->keybytes,
&usage_keyblock);
if (ret != 0)
goto cleanup;
ret = krb5int_c_init_keyblock(NULL, key->keyblock.enctype, enc->keybytes,
&enc_keyblock);
if (ret != 0)
goto cleanup;
checksum = make_data(header->data.data, hash->hashsize);
/* Adjust pointers so confounder is at start of header. */
header->data.length -= hash->hashsize;
header->data.data += hash->hashsize;
/* We may have to try two usage values; see below. */
do {
/* Derive a usage key from the session key and usage. */
ret = usage_key(enc, hash, &key->keyblock, usage, usage_keyblock);
if (ret != 0)
goto cleanup;
/* Derive the encryption key from the usage key and checksum. */
ret = enc_key(enc, hash, usage_keyblock, &checksum, enc_keyblock);
if (ret)
goto cleanup;
/* Decrypt the ciphertext. */
ret = keyblock_crypt(enc, enc_keyblock, ivec, data, num_data);
if (ret != 0)
goto cleanup;
/* Compute HMAC(usage key, plaintext) to get the checksum. */
ret = krb5int_hmac_keyblock(hash, usage_keyblock, data, num_data,
&comp_checksum);
if (ret != 0)
goto cleanup;
if (k5_bcmp(checksum.data, comp_checksum.data, hash->hashsize) != 0) {
if (usage == 9) {
/*
* RFC 4757 specifies usage 8 for TGS-REP encrypted parts
* encrypted in a subkey, but the value used by MS is actually
* 9. We now use 9 to start with, but fall back to 8 on
* failure in case we are communicating with a KDC using the
* value from the RFC. ivec is always NULL in this case.
* We need to re-encrypt the data in the wrong key first.
*/
ret = keyblock_crypt(enc, enc_keyblock, NULL, data, num_data);
if (ret != 0)
goto cleanup;
usage = 8;
continue;
}
ret = KRB5KRB_AP_ERR_BAD_INTEGRITY;
goto cleanup;
}
break;
} while (1);
cleanup:
header->data = header_data; /* Restore header pointers. */
krb5int_c_free_keyblock(NULL, usage_keyblock);
krb5int_c_free_keyblock(NULL, enc_keyblock);
zapfree(comp_checksum.data, comp_checksum.length);
return ret;
}
krb5_error_code
krb5int_arcfour_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;
const struct krb5_hash_provider *hash = ktp->hash;
krb5_error_code ret;
krb5_crypto_iov *header, *trailer;
krb5_keyblock *usage_keyblock = NULL, *enc_keyblock = NULL;
krb5_data checksum, confounder, header_data;
size_t i;
/*
* Caller must have provided space for the header, padding
* and trailer; per RFC 4757 we will arrange it as:
*
* Checksum | E(Confounder | Plaintext)
*/
header = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_HEADER);
if (header == NULL ||
header->data.length < hash->hashsize + CONFOUNDERLENGTH)
return KRB5_BAD_MSIZE;
header_data = header->data;
/* Trailer may be absent. */
trailer = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_TRAILER);
if (trailer != NULL)
trailer->data.length = 0;
/* Ensure that there is no padding. */
for (i = 0; i < num_data; i++) {
if (data[i].flags == KRB5_CRYPTO_TYPE_PADDING)
data[i].data.length = 0;
}
ret = krb5int_c_init_keyblock(NULL, key->keyblock.enctype, enc->keybytes,
&usage_keyblock);
if (ret != 0)
goto cleanup;
ret = krb5int_c_init_keyblock(NULL, key->keyblock.enctype, enc->keybytes,
&enc_keyblock);
if (ret != 0)
goto cleanup;
/* Derive a usage key from the session key and usage. */
ret = usage_key(enc, hash, &key->keyblock, usage, usage_keyblock);
if (ret != 0)
goto cleanup;
/* Generate a confounder in the header block, after the checksum. */
header->data.length = hash->hashsize + CONFOUNDERLENGTH;
confounder = make_data(header->data.data + hash->hashsize,
CONFOUNDERLENGTH);
ret = krb5_c_random_make_octets(0, &confounder);
if (ret != 0)
goto cleanup;
checksum = make_data(header->data.data, hash->hashsize);
/* Adjust pointers so confounder is at start of header. */
header->data.length -= hash->hashsize;
header->data.data += hash->hashsize;
/* Compute the checksum using the usage key. */
ret = krb5int_hmac_keyblock(hash, usage_keyblock, data, num_data,
&checksum);
if (ret != 0)
goto cleanup;
/* Derive the encryption key from the usage key and checksum. */
ret = enc_key(enc, hash, usage_keyblock, &checksum, enc_keyblock);
if (ret)
goto cleanup;
ret = keyblock_crypt(enc, enc_keyblock, ivec, data, num_data);
cleanup:
header->data = header_data; /* Restore header pointers. */
krb5int_c_free_keyblock(NULL, usage_keyblock);
krb5int_c_free_keyblock(NULL, enc_keyblock);
return ret;
}
krb5_error_code
krb5int_c_iov_decrypt_stream(const struct krb5_keytypes *ktp, krb5_key key,
krb5_keyusage keyusage, const krb5_data *ivec,
krb5_crypto_iov *data, size_t num_data)
{
krb5_error_code ret;
unsigned int header_len, trailer_len;
krb5_crypto_iov *iov;
krb5_crypto_iov *stream;
size_t i, j;
int got_data = 0;
stream = krb5int_c_locate_iov(data, num_data, KRB5_CRYPTO_TYPE_STREAM);
assert(stream != NULL);
header_len = ktp->crypto_length(ktp, KRB5_CRYPTO_TYPE_HEADER);
trailer_len = ktp->crypto_length(ktp, KRB5_CRYPTO_TYPE_TRAILER);
if (stream->data.length < header_len + trailer_len)
return KRB5_BAD_MSIZE;
iov = calloc(num_data + 2, sizeof(krb5_crypto_iov));
if (iov == NULL)
return ENOMEM;
i = 0;
iov[i].flags = KRB5_CRYPTO_TYPE_HEADER; /* takes place of STREAM */
iov[i].data = make_data(stream->data.data, header_len);
i++;
for (j = 0; j < num_data; j++) {
if (data[j].flags == KRB5_CRYPTO_TYPE_DATA) {
if (got_data) {
free(iov);
return KRB5_BAD_MSIZE;
}
got_data++;
data[j].data.data = stream->data.data + header_len;
data[j].data.length = stream->data.length - header_len
- trailer_len;
}
if (data[j].flags == KRB5_CRYPTO_TYPE_SIGN_ONLY ||
data[j].flags == KRB5_CRYPTO_TYPE_DATA)
iov[i++] = data[j];
}
/* Use empty padding since tokens don't indicate the padding length. */
iov[i].flags = KRB5_CRYPTO_TYPE_PADDING;
iov[i].data = empty_data();
i++;
iov[i].flags = KRB5_CRYPTO_TYPE_TRAILER;
iov[i].data = make_data(stream->data.data + stream->data.length -
trailer_len, trailer_len);
i++;
assert(i <= num_data + 2);
ret = ktp->decrypt(ktp, key, keyusage, ivec, iov, i);
free(iov);
return ret;
}
