krb5_error_code
krb5int_hmac(const struct krb5_hash_provider *hash, krb5_key key,
const krb5_crypto_iov *data, size_t num_data,
krb5_data *output)
{
return krb5int_hmac_keyblock(hash, &key->keyblock, data, num_data, output);
}
/* 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;
}
/* Derive a usage key from a session key and krb5 usage constant. */
static krb5_error_code
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);
}
krb5_error_code krb5int_hmacmd5_checksum(const struct krb5_cksumtypes *ctp,
krb5_key key, krb5_keyusage usage,
const krb5_crypto_iov *data,
size_t num_data,
krb5_data *output)
{
krb5_keyusage ms_usage;
krb5_error_code ret;
krb5_keyblock ks, *keyblock;
krb5_crypto_iov *hash_iov = NULL, iov;
krb5_data ds = empty_data(), hashval = empty_data();
char t[4];
if (key == NULL || key->keyblock.length > ctp->hash->blocksize)
return KRB5_BAD_ENCTYPE;
if (ctp->ctype == CKSUMTYPE_HMAC_MD5_ARCFOUR) {
/* Compute HMAC(key, "signaturekey\0") to get the signing key ks. */
ret = alloc_data(&ds, ctp->hash->hashsize);
if (ret != 0)
goto cleanup;
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = make_data("signaturekey", 13);
ret = krb5int_hmac(ctp->hash, key, &iov, 1, &ds);
if (ret)
goto cleanup;
ks.length = key->keyblock.length;
ks.contents = (krb5_octet *) ds.data;
keyblock = &ks;
} else /* For md5-hmac, just use the key. */
keyblock = &key->keyblock;
/* Compute the MD5 value of the input. */
ms_usage = krb5int_arcfour_translate_usage(usage);
store_32_le(ms_usage, t);
hash_iov = k5alloc((num_data + 1) * sizeof(krb5_crypto_iov), &ret);
if (hash_iov == NULL)
goto cleanup;
hash_iov[0].flags = KRB5_CRYPTO_TYPE_DATA;
hash_iov[0].data = make_data(t, 4);
memcpy(hash_iov + 1, data, num_data * sizeof(krb5_crypto_iov));
ret = alloc_data(&hashval, ctp->hash->hashsize);
if (ret != 0)
goto cleanup;
ret = ctp->hash->hash(hash_iov, num_data + 1, &hashval);
if (ret != 0)
goto cleanup;
/* Compute HMAC(ks, md5value). */
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = hashval;
ret = krb5int_hmac_keyblock(ctp->hash, keyblock, &iov, 1, output);
cleanup:
zapfree(ds.data, ds.length);
zapfree(hashval.data, hashval.length);
free(hash_iov);
return ret;
}
/*
* Implements the hmac-sha1 PRF. pass has been pre-hashed (if
* necessary) and converted to a key already; salt has had the block
* index appended to the original salt.
*/
static krb5_error_code
hmac(const struct krb5_hash_provider *hash, krb5_keyblock *pass,
krb5_data *salt, krb5_data *out)
{
krb5_error_code err;
krb5_crypto_iov iov;
if (debug_hmac)
printd(" hmac input", salt);
iov.flags = KRB5_CRYPTO_TYPE_DATA;
iov.data = *salt;
err = krb5int_hmac_keyblock(hash, pass, &iov, 1, out);
if (err == 0 && debug_hmac)
printd(" hmac output", out);
return err;
}
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;
}
