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exchange/src/lib/exchange_api_age_withdraw_reveal.c

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/*
This file is part of TALER
Copyright (C) 2023 Taler Systems SA
TALER is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 3, or (at your option) any later version.
TALER is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
TALER; see the file COPYING. If not, see
<http://www.gnu.org/licenses/>
*/
/**
* @file lib/exchange_api_age_withdraw_reveal.c
* @brief Implementation of /age-withdraw/$ACH/reveal requests
* @author Özgür Kesim
*/
#include "platform.h"
#include <gnunet/gnunet_common.h>
#include <jansson.h>
#include <microhttpd.h> /* just for HTTP status codes */
#include <gnunet/gnunet_util_lib.h>
#include <gnunet/gnunet_json_lib.h>
#include <gnunet/gnunet_curl_lib.h>
#include "taler_curl_lib.h"
#include "taler_json_lib.h"
#include "taler_exchange_service.h"
#include "exchange_api_common.h"
#include "exchange_api_handle.h"
#include "taler_signatures.h"
#include "exchange_api_curl_defaults.h"
/**
* Handler for a running age-withdraw-reveal request
*/
struct TALER_EXCHANGE_AgeWithdrawRevealHandle
{
/* The index not to be disclosed */
uint8_t noreveal_index;
/* The age-withdraw commitment */
struct TALER_AgeWithdrawCommitmentHashP h_commitment;
/* The maximum age */
uint8_t max_age;
/* Number of coins */
size_t num_coins;
/* The @e num_coins * kappa coin secrets from the age-withdraw commitment */
const struct TALER_EXCHANGE_AgeWithdrawCoinInput *coins_input;
/* The @e num_coins algorithm- and coin-specific parameters from the
* previous call to /age-withdraw. */
const struct TALER_ExchangeWithdrawValues *alg_values;
/* The url for the reveal request */
const char *request_url;
/**
* CURL handle for the request job.
*/
struct GNUNET_CURL_Job *job;
/**
* Post Context
*/
struct TALER_CURL_PostContext post_ctx;
/* Callback */
TALER_EXCHANGE_AgeWithdrawRevealCallback callback;
/* Reveal */
void *callback_cls;
};
static enum GNUNET_GenericReturnValue
reveal_coin (
const struct TALER_PlanchetMasterSecretP *secret,
const struct TALER_DenominationPublicKey *denom_pub,
const struct TALER_ExchangeWithdrawValues *alg_values,
const struct TALER_BlindedDenominationSignature *blind_sig,
uint8_t max_age,
struct TALER_EXCHANGE_RevealedCoinInfo *revealed_coin)
{
enum GNUNET_GenericReturnValue ret = GNUNET_SYSERR;
#define BREAK_ON_FAILURE(call) \
do { \
if (GNUNET_OK != (call)) { GNUNET_break (0); break; } \
} while(0)
do {
struct TALER_CoinPubHashP h_coin_pub;
struct TALER_PlanchetDetail planchet_detail;
const struct TALER_AgeCommitmentHash *hac = NULL;
struct TALER_FreshCoin fresh_coin;
TALER_planchet_setup_coin_priv (secret,
alg_values,
&revealed_coin->coin_priv);
TALER_planchet_blinding_secret_create (secret,
alg_values,
&revealed_coin->bks);
revealed_coin->age_commitment_proof = NULL;
if (0 < max_age)
{
BREAK_ON_FAILURE (
TALER_age_restriction_from_secret (
secret,
&denom_pub->age_mask,
max_age,
revealed_coin->age_commitment_proof));
TALER_age_commitment_hash (
&revealed_coin->age_commitment_proof->commitment,
&revealed_coin->h_age_commitment);
hac = &revealed_coin->h_age_commitment;
}
BREAK_ON_FAILURE (
TALER_planchet_prepare (denom_pub,
alg_values,
&revealed_coin->bks,
&revealed_coin->coin_priv,
hac,
&h_coin_pub,
&planchet_detail));
BREAK_ON_FAILURE (
TALER_planchet_to_coin (denom_pub,
blind_sig,
&revealed_coin->bks,
&revealed_coin->coin_priv,
&revealed_coin->h_age_commitment,
&h_coin_pub,
alg_values,
&fresh_coin));
/* success */
revealed_coin->sig = fresh_coin.sig;
ret = GNUNET_OK;
} while(0);
return ret;
#undef BREAK_ON_FAILURE
}
/**
* We got a 200 OK response for the /age-withdraw/$ACH/reveal operation.
* Extract the signed blindedcoins and return it to the caller.
*
* @param awrh operation handle
* @param j_response reply from the exchange
* @param num_coins The (expected) number of revealed coins
* @param[in,out] revealed_coins The @e num_coins revealed coins to populate
* @return #GNUNET_OK on success, #GNUNET_SYSERR on errors
*/
static enum GNUNET_GenericReturnValue
age_withdraw_reveal_ok (
struct TALER_EXCHANGE_AgeWithdrawRevealHandle *awrh,
const json_t *j_response)
{
struct TALER_EXCHANGE_AgeWithdrawRevealResponse response = {
.hr.reply = j_response,
.hr.http_status = MHD_HTTP_OK,
};
const json_t *j_sigs;
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_array_const ("ev_sigs",
&j_sigs),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK != GNUNET_JSON_parse (j_response,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if (awrh->num_coins != json_array_size (j_sigs))
{
/* Number of coins generated does not match our expectation */
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
{
struct TALER_EXCHANGE_RevealedCoinInfo revealed_coins[awrh->num_coins];
/* Reconstruct the coins and unblind the signatures */
for (size_t n = 0; n < awrh->num_coins; n++)
{
enum GNUNET_GenericReturnValue ret;
struct TALER_BlindedDenominationSignature blinded_sig;
json_t *j_sig = json_array_get (j_sigs, n);
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_fixed_auto ("", &blinded_sig),
GNUNET_JSON_spec_end ()
};
GNUNET_assert (NULL != j_sig);
if (GNUNET_OK != GNUNET_JSON_parse (j_sig,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
ret = reveal_coin (&awrh->coins_input[n].secrets[awrh->noreveal_index],
&awrh->coins_input[n].denom_pub->key,
&awrh->alg_values[n],
&blinded_sig,
awrh->max_age,
&revealed_coins[n]);
if (GNUNET_OK != ret)
return ret;
}
response.details.ok.num_coins = awrh->num_coins;
response.details.ok.revealed_coins = revealed_coins;
awrh->callback (awrh->callback_cls,
&response);
/* Make sure the callback isn't called again */
awrh->callback = NULL;
}
return GNUNET_OK;
}
/**
* Function called when we're done processing the
* HTTP /age-withdraw/$ACH/reveal request.
*
* @param cls the `struct TALER_EXCHANGE_AgeWithdrawRevealHandle`
* @param response_code The HTTP response code
* @param response response data
*/
static void
handle_age_withdraw_reveal_finished (
void *cls,
long response_code,
const void *response)
{
struct TALER_EXCHANGE_AgeWithdrawRevealHandle *awrh = cls;
const json_t *j_response = response;
struct TALER_EXCHANGE_AgeWithdrawRevealResponse awr = {
.hr.reply = j_response,
.hr.http_status = (unsigned int) response_code
};
awrh->job = NULL;
/* FIXME[oec]: Only handle response-codes that are in the spec */
switch (response_code)
{
case 0:
awr.hr.ec = TALER_EC_GENERIC_INVALID_RESPONSE;
break;
case MHD_HTTP_OK:
{
enum GNUNET_GenericReturnValue ret;
ret = age_withdraw_reveal_ok (awrh,
j_response);
if (GNUNET_OK != ret)
{
GNUNET_break_op (0);
awr.hr.http_status = 0;
awr.hr.ec = TALER_EC_GENERIC_REPLY_MALFORMED;
break;
}
GNUNET_assert (NULL == awrh->callback);
TALER_EXCHANGE_age_withdraw_reveal_cancel (awrh);
return;
}
case MHD_HTTP_UNAVAILABLE_FOR_LEGAL_REASONS:
/* only validate reply is well-formed */
{
uint64_t ptu;
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_uint64 ("legitimization_uuid",
&ptu),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (j_response,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
awr.hr.http_status = 0;
awr.hr.ec = TALER_EC_GENERIC_REPLY_MALFORMED;
break;
}
}
case MHD_HTTP_BAD_REQUEST:
/* This should never happen, either us or the exchange is buggy
(or API version conflict); just pass JSON reply to the application */
awr.hr.ec = TALER_JSON_get_error_code (j_response);
awr.hr.hint = TALER_JSON_get_error_hint (j_response);
break;
case MHD_HTTP_FORBIDDEN:
GNUNET_break_op (0);
/**
* This should never happen, as we don't sent any signatures
* to the exchange to verify. We should simply pass the JSON reply
* to the application
**/
awr.hr.ec = TALER_JSON_get_error_code (j_response);
awr.hr.hint = TALER_JSON_get_error_hint (j_response);
break;
case MHD_HTTP_NOT_FOUND:
/* Nothing really to verify, the exchange basically just says
that it doesn't know this age-withraw commitment. */
awr.hr.ec = TALER_JSON_get_error_code (j_response);
awr.hr.hint = TALER_JSON_get_error_hint (j_response);
break;
case MHD_HTTP_CONFLICT:
/* An age commitment for one of the coins did not fulfill
* the required maximum age requirement of the corresponding
* reserve.
* Error code: TALER_EC_EXCHANGE_GENERIC_COIN_AGE_REQUIREMENT_FAILURE.
*/
awr.hr.ec = TALER_JSON_get_error_code (j_response);
awr.hr.hint = TALER_JSON_get_error_hint (j_response);
break;
case MHD_HTTP_GONE:
/* could happen if denomination was revoked */
/* Note: one might want to check /keys for revocation
signature here, alas tricky in case our /keys
is outdated => left to clients */
awr.hr.ec = TALER_JSON_get_error_code (j_response);
awr.hr.hint = TALER_JSON_get_error_hint (j_response);
break;
case MHD_HTTP_INTERNAL_SERVER_ERROR:
/* Server had an internal issue; we should retry, but this API
leaves this to the application */
awr.hr.ec = TALER_JSON_get_error_code (j_response);
awr.hr.hint = TALER_JSON_get_error_hint (j_response);
break;
default:
/* unexpected response code */
GNUNET_break_op (0);
awr.hr.ec = TALER_JSON_get_error_code (j_response);
awr.hr.hint = TALER_JSON_get_error_hint (j_response);
GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
"Unexpected response code %u/%d for exchange age-withdraw\n",
(unsigned int) response_code,
(int) awr.hr.ec);
break;
}
awrh->callback (awrh->callback_cls,
&awr);
TALER_EXCHANGE_age_withdraw_reveal_cancel (awrh);
}
/**
* Prepares the request URL for the age-withdraw-reveal request
*
* @param exchange_url The base-URL to the exchange
* @param[in,out] awrh The handler
* @return GNUNET_OK on success, GNUNET_SYSERR otherwise
*/
static
enum GNUNET_GenericReturnValue
prepare_url (
const char *exchange_url,
struct TALER_EXCHANGE_AgeWithdrawRevealHandle *awrh)
{
char arg_str[sizeof (struct TALER_AgeWithdrawCommitmentHashP) * 2 + 32];
char pub_str[sizeof (struct TALER_AgeWithdrawCommitmentHashP) * 2];
char *end;
end = GNUNET_STRINGS_data_to_string (&awrh->h_commitment,
sizeof (awrh->h_commitment),
pub_str,
sizeof (pub_str));
*end = '\0';
GNUNET_snprintf (arg_str,
sizeof (arg_str),
"age-withraw/%s/reveal",
pub_str);
awrh->request_url = TALER_url_join (exchange_url,
arg_str,
NULL);
if (NULL == awrh->request_url)
{
GNUNET_break (0);
TALER_EXCHANGE_age_withdraw_reveal_cancel (awrh);
return GNUNET_SYSERR;
}
return GNUNET_OK;
}
/**
* Call /age-withdraw/$ACH/reveal
*
* @param curl_ctx The context for CURL
* @param awrh The handler
* @param reveal_inputs The secrets of the coin candidates
*/
static
void
perform_protocol (
struct GNUNET_CURL_Context *curl_ctx,
struct TALER_EXCHANGE_AgeWithdrawRevealHandle *awrh)
{
CURL *curlh = NULL;
json_t *j_request_body = NULL;
json_t *j_array_of_secrets = NULL;
json_t *j_secrets = NULL;
json_t *j_sec = NULL;
#define FAIL_IF(cond) \
do { \
if ((cond)) \
{ \
GNUNET_break (! (cond)); \
goto ERROR; \
} \
} while(0)
for (size_t n = 0; n < awrh->num_coins; n++)
{
const struct TALER_PlanchetMasterSecretP *secrets =
awrh->coins_input[n].secrets;
j_secrets = json_array ();
FAIL_IF (NULL == j_secrets);
for (uint8_t k = 0; k < TALER_CNC_KAPPA; k++)
{
const struct TALER_PlanchetMasterSecretP *secret = &secrets[k];
if (awrh->noreveal_index == k)
continue;
j_sec = GNUNET_JSON_PACK (
GNUNET_JSON_pack_data_auto (NULL, secret));
FAIL_IF (NULL == j_sec);
FAIL_IF (0 < json_array_append_new (j_secrets,
j_sec));
}
FAIL_IF (0 < json_array_append_new (j_array_of_secrets,
j_secrets));
}
j_request_body = GNUNET_JSON_PACK (
GNUNET_JSON_pack_array_steal ("disclosed_coin_secrets",
j_array_of_secrets));
FAIL_IF (NULL == j_request_body);
curlh = TALER_EXCHANGE_curl_easy_get_ (awrh->request_url);
FAIL_IF (NULL == curlh);
FAIL_IF (GNUNET_OK !=
TALER_curl_easy_post (&awrh->post_ctx,
curlh,
j_request_body));
json_decref (j_request_body);
j_request_body = NULL;
awrh->job = GNUNET_CURL_job_add2 (curl_ctx,
curlh,
awrh->post_ctx.headers,
&handle_age_withdraw_reveal_finished,
awrh);
FAIL_IF (NULL == awrh->job);
/* No error, return */
return;
ERROR:
if (NULL != j_sec)
json_decref (j_sec);
if (NULL != j_secrets)
json_decref (j_secrets);
if (NULL != j_array_of_secrets)
json_decref (j_array_of_secrets);
if (NULL != j_request_body)
json_decref (j_request_body);
if (NULL != curlh)
curl_easy_cleanup (curlh);
TALER_EXCHANGE_age_withdraw_reveal_cancel (awrh);
return;
#undef FAIL_IF
}
struct TALER_EXCHANGE_AgeWithdrawRevealHandle *
TALER_EXCHANGE_age_withdraw_reveal (
struct GNUNET_CURL_Context *curl_ctx,
const char *exchange_url,
size_t num_coins,
const struct TALER_EXCHANGE_AgeWithdrawCoinInput coins_input[static
num_coins],
const struct TALER_ExchangeWithdrawValues alg_values[static num_coins],
uint8_t noreveal_index,
const struct TALER_AgeWithdrawCommitmentHashP *h_commitment,
uint8_t max_age,
TALER_EXCHANGE_AgeWithdrawRevealCallback reveal_cb,
void *reveal_cb_cls)
{
struct TALER_EXCHANGE_AgeWithdrawRevealHandle *awrh =
GNUNET_new (struct TALER_EXCHANGE_AgeWithdrawRevealHandle);
awrh->noreveal_index = noreveal_index;
awrh->callback = reveal_cb;
awrh->callback_cls = reveal_cb_cls;
awrh->h_commitment = *h_commitment;
awrh->num_coins = num_coins;
awrh->coins_input = coins_input;
awrh->alg_values = alg_values;
awrh->max_age = max_age;
if (GNUNET_OK !=
prepare_url (exchange_url,
awrh))
return NULL;
perform_protocol (curl_ctx, awrh);
return awrh;
}
void
TALER_EXCHANGE_age_withdraw_reveal_cancel (
struct TALER_EXCHANGE_AgeWithdrawRevealHandle *awrh)
{
if (NULL != awrh->job)
{
GNUNET_CURL_job_cancel (awrh->job);
awrh->job = NULL;
}
TALER_curl_easy_post_finished (&awrh->post_ctx);
/* FIXME[oec]: anything else left to cleanup!? */
GNUNET_free (awrh);
}
/* exchange_api_age_withdraw_reveal.c */
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