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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
ARCFOUR cipher (based on a cipher posted on the Usenet in Spring-95).
This cipher is widely believed and has been tested to be equivalent
with the RC4 cipher from RSA Data Security, Inc. (RC4 is a trademark
of RSA Data Security)
*/
#include "k5-int.h"
#include "arcfour-int.h"
#include "hash_provider/hash_provider.h"
const char l40[] = "fortybits";
krb5_keyusage
krb5int_arcfour_translate_usage(krb5_keyusage usage)
{
switch (usage) {
case 1: return 1; /* AS-REQ PA-ENC-TIMESTAMP padata timestamp, */
case 2: return 2; /* ticket from kdc */
case 3: return 8; /* as-rep encrypted part */
case 4: return 4; /* tgs-req authz data */
case 5: return 5; /* tgs-req authz data in subkey */
case 6: return 6; /* tgs-req authenticator cksum */
case 7: return 7; /* tgs-req authenticator */
case 8: return 8;
case 9: return 9; /* tgs-rep encrypted with subkey */
case 10: return 10; /* ap-rep authentication cksum (never used by MS) */
case 11: return 11; /* app-req authenticator */
case 12: return 12; /* app-rep encrypted part */
case 23: return 13; /* sign wrap token*/
default: return usage;
}
}
/* Derive a usage key from a session key and krb5 usage constant. */
krb5_error_code
krb5int_arcfour_usage_key(const struct krb5_enc_provider *enc,
const struct krb5_hash_provider *hash,
const krb5_keyblock *session_keyblock,
krb5_keyusage usage,
krb5_keyblock *out)
{
char salt_buf[14];
unsigned int salt_len;
krb5_data out_data = make_data(out->contents, out->length);
krb5_crypto_iov iov;
krb5_keyusage ms_usage;
/* Generate the salt. */
ms_usage = krb5int_arcfour_translate_usage(usage);
if (session_keyblock->enctype == ENCTYPE_ARCFOUR_HMAC_EXP) {
memcpy(salt_buf, l40, 10);
store_32_le(ms_usage, salt_buf + 10);
salt_len = 14;
} else {
store_32_le(ms_usage, salt_buf);
salt_len = 4;
}
/* Compute HMAC(key, salt) to produce the usage key. */
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = make_data(salt_buf, salt_len);
return krb5int_hmac_keyblock(hash, session_keyblock, &iov, 1, &out_data);
}
/* Derive an encryption key from a usage key and (typically) checksum. */
krb5_error_code
krb5int_arcfour_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;
}
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