/* Derive an encryption key from a usage key and (typically) checksum. */
static krb5_error_code
enc_key(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *usage_keyblock, const krb5_data *checksum,
krb5_keyblock *out)
{
krb5_keyblock *trunc_keyblock = NULL;
krb5_data out_data = make_data(out->contents, out->length);
krb5_crypto_iov iov;
krb5_error_code ret;
/* Copy usage_keyblock to trunc_keyblock and truncate if exportable. */
ret = krb5int_c_copy_keyblock(NULL, usage_keyblock, &trunc_keyblock);
if (ret != 0)
return ret;
if (trunc_keyblock->enctype == ENCTYPE_ARCFOUR_HMAC_EXP)
memset(trunc_keyblock->contents + 7, 0xab, 9);
/* Compute HMAC(trunc_key, checksum) to produce the encryption key. */
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = *checksum;
ret = krb5int_hmac_keyblock(hash, trunc_keyblock, &iov, 1, &out_data);
krb5int_c_free_keyblock(NULL, trunc_keyblock);
return ret;
}
krb5_error_code
krb5int_arcfour_gsscrypt(const krb5_keyblock *keyblock, krb5_keyusage usage,
const krb5_data *kd_data, krb5_crypto_iov *data,
size_t num_data)
{
const struct krb5_enc_provider *enc = &krb5int_enc_arcfour;
const struct krb5_hash_provider *hash = &krb5int_hash_md5;
krb5_keyblock *usage_keyblock = NULL, *enc_keyblock = NULL;
krb5_error_code ret;
ret = krb5int_c_init_keyblock(NULL, keyblock->enctype, enc->keybytes,
&usage_keyblock);
if (ret != 0)
goto cleanup;
ret = krb5int_c_init_keyblock(NULL, 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, keyblock, usage, usage_keyblock);
if (ret != 0)
goto cleanup;
/* Derive the encryption key from the usage key and kd_data. */
ret = enc_key(enc, hash, usage_keyblock, kd_data, enc_keyblock);
if (ret != 0)
goto cleanup;
/* Encrypt or decrypt (encrypt_iov works for both) the input. */
ret = keyblock_crypt(enc, enc_keyblock, 0, data, num_data);
cleanup:
krb5int_c_free_keyblock(NULL, usage_keyblock);
krb5int_c_free_keyblock(NULL, enc_keyblock);
return ret;
}
void KRB5_CALLCONV
krb5_free_keyblock(krb5_context context, register krb5_keyblock *val)
{
krb5int_c_free_keyblock (context, val);
}
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;
}
