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exchange/src/lib/exchange_api_link.c

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/*
This file is part of TALER
Copyright (C) 2015-2020 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_link.c
* @brief Implementation of the /coins/$COIN_PUB/link request
* @author Christian Grothoff
*/
#include "platform.h"
#include <microhttpd.h> /* just for HTTP status codes */
#include <gnunet/gnunet_util_lib.h>
#include <gnunet/gnunet_curl_lib.h>
#include "taler_exchange_service.h"
#include "taler_json_lib.h"
#include "exchange_api_handle.h"
#include "taler_signatures.h"
#include "exchange_api_curl_defaults.h"
/**
* @brief A /coins/$COIN_PUB/link Handle
*/
struct TALER_EXCHANGE_LinkHandle
{
/**
* The connection to exchange this request handle will use
*/
struct TALER_EXCHANGE_Handle *exchange;
/**
* The url for this request.
*/
char *url;
/**
* Handle for the request.
*/
struct GNUNET_CURL_Job *job;
/**
* Function to call with the result.
*/
TALER_EXCHANGE_LinkCallback link_cb;
/**
* Closure for @e cb.
*/
void *link_cb_cls;
/**
* Private key of the coin, required to decode link information.
*/
struct TALER_CoinSpendPrivateKeyP coin_priv;
};
/**
* Parse the provided linkage data from the "200 OK" response
* for one of the coins.
*
* @param lh link handle
* @param json json reply with the data for one coin
* @param coin_num number of the coin to decode
* @param trans_pub our transfer public key
* @param[out] coin_priv where to return private coin key
* @param[out] sig where to return private coin signature
* @param[out] pub where to return the public key for the coin
* @return #GNUNET_OK on success, #GNUNET_SYSERR on error
*/
static int
parse_link_coin (const struct TALER_EXCHANGE_LinkHandle *lh,
const json_t *json,
unsigned int coin_num,
const struct TALER_TransferPublicKeyP *trans_pub,
struct TALER_CoinSpendPrivateKeyP *coin_priv,
struct TALER_DenominationSignature *sig,
struct TALER_DenominationPublicKey *pub)
{
struct GNUNET_CRYPTO_RsaSignature *bsig;
struct GNUNET_CRYPTO_RsaPublicKey *rpub;
struct TALER_CoinSpendSignatureP link_sig;
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_rsa_public_key ("denom_pub", &rpub),
GNUNET_JSON_spec_rsa_signature ("ev_sig", &bsig),
GNUNET_JSON_spec_fixed_auto ("link_sig", &link_sig),
GNUNET_JSON_spec_end ()
};
struct TALER_TransferSecretP secret;
struct TALER_PlanchetSecretsP fc;
/* parse reply */
if (GNUNET_OK !=
GNUNET_JSON_parse (json,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
TALER_link_recover_transfer_secret (trans_pub,
&lh->coin_priv,
&secret);
TALER_planchet_setup_refresh (&secret,
coin_num,
&fc);
/* extract coin and signature */
*coin_priv = fc.coin_priv;
sig->rsa_signature
= TALER_rsa_unblind (bsig,
&fc.blinding_key.bks,
rpub);
/* verify link_sig */
{
struct TALER_PlanchetDetail pd;
struct GNUNET_HashCode c_hash;
struct TALER_LinkDataPS ldp = {
.purpose.size = htonl (sizeof (ldp)),
.purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_LINK),
.transfer_pub = *trans_pub
};
GNUNET_CRYPTO_eddsa_key_get_public (&lh->coin_priv.eddsa_priv,
&ldp.old_coin_pub.eddsa_pub);
pub->rsa_public_key = rpub;
if (GNUNET_OK !=
TALER_planchet_prepare (pub,
&fc,
&c_hash,
&pd))
{
GNUNET_break (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
ldp.h_denom_pub = pd.denom_pub_hash;
GNUNET_CRYPTO_hash (pd.coin_ev,
pd.coin_ev_size,
&ldp.coin_envelope_hash);
GNUNET_free (pd.coin_ev);
if (GNUNET_OK !=
GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_LINK,
&ldp,
&link_sig.eddsa_signature,
&ldp.old_coin_pub.eddsa_pub))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
}
/* clean up */
pub->rsa_public_key = GNUNET_CRYPTO_rsa_public_key_dup (rpub);
GNUNET_JSON_parse_free (spec);
return GNUNET_OK;
}
/**
* Parse the provided linkage data from the "200 OK" response
* for one of the coins.
*
* @param[in,out] lh link handle (callback may be zero'ed out)
* @param json json reply with the data for one coin
* @return #GNUNET_OK on success, #GNUNET_SYSERR on error
*/
static int
parse_link_ok (struct TALER_EXCHANGE_LinkHandle *lh,
const json_t *json)
{
unsigned int session;
unsigned int num_coins;
int ret;
struct TALER_EXCHANGE_HttpResponse hr = {
.reply = json,
.http_status = MHD_HTTP_OK
};
if (! json_is_array (json))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
num_coins = 0;
/* Theoretically, a coin may have been melted repeatedly
into different sessions; so the response is an array
which contains information by melting session. That
array contains another array. However, our API returns
a single 1d array, so we flatten the 2d array that is
returned into a single array. Note that usually a coin
is melted at most once, and so we'll only run this
loop once for 'session=0' in most cases.
num_coins tracks the size of the 1d array we return,
whilst 'i' and 'session' track the 2d array. *///
for (session = 0; session<json_array_size (json); session++)
{
json_t *jsona;
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_json ("new_coins", &jsona),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (json_array_get (json,
session),
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if (! json_is_array (jsona))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
/* count all coins over all sessions */
num_coins += json_array_size (jsona);
GNUNET_JSON_parse_free (spec);
}
/* Now that we know how big the 1d array is, allocate
and fill it. */
{
unsigned int off_coin; /* index into 1d array */
unsigned int i;
struct TALER_CoinSpendPrivateKeyP coin_privs[GNUNET_NZL (num_coins)];
struct TALER_DenominationSignature sigs[GNUNET_NZL (num_coins)];
struct TALER_DenominationPublicKey pubs[GNUNET_NZL (num_coins)];
memset (sigs, 0, sizeof (sigs));
memset (pubs, 0, sizeof (pubs));
off_coin = 0;
for (session = 0; session<json_array_size (json); session++)
{
json_t *jsona;
struct TALER_TransferPublicKeyP trans_pub;
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_json ("new_coins",
&jsona),
GNUNET_JSON_spec_fixed_auto ("transfer_pub",
&trans_pub),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (json_array_get (json,
session),
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if (! json_is_array (jsona))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
/* decode all coins */
for (i = 0; i<json_array_size (jsona); i++)
{
GNUNET_assert (i + off_coin < num_coins);
if (GNUNET_OK !=
parse_link_coin (lh,
json_array_get (jsona,
i),
i,
&trans_pub,
&coin_privs[i + off_coin],
&sigs[i + off_coin],
&pubs[i + off_coin]))
{
GNUNET_break_op (0);
break;
}
}
/* check if we really got all, then invoke callback */
off_coin += i;
if (i != json_array_size (jsona))
{
GNUNET_break_op (0);
ret = GNUNET_SYSERR;
GNUNET_JSON_parse_free (spec);
break;
}
GNUNET_JSON_parse_free (spec);
} /* end of for (session) */
if (off_coin == num_coins)
{
lh->link_cb (lh->link_cb_cls,
&hr,
num_coins,
coin_privs,
sigs,
pubs);
lh->link_cb = NULL;
ret = GNUNET_OK;
}
else
{
GNUNET_break_op (0);
ret = GNUNET_SYSERR;
}
/* clean up */
GNUNET_assert (off_coin <= num_coins);
for (i = 0; i<off_coin; i++)
{
if (NULL != sigs[i].rsa_signature)
GNUNET_CRYPTO_rsa_signature_free (sigs[i].rsa_signature);
if (NULL != pubs[i].rsa_public_key)
GNUNET_CRYPTO_rsa_public_key_free (pubs[i].rsa_public_key);
}
}
return ret;
}
/**
* Function called when we're done processing the
* HTTP /coins/$COIN_PUB/link request.
*
* @param cls the `struct TALER_EXCHANGE_LinkHandle`
* @param response_code HTTP response code, 0 on error
* @param response parsed JSON result, NULL on error
*/
static void
handle_link_finished (void *cls,
long response_code,
const void *response)
{
struct TALER_EXCHANGE_LinkHandle *lh = cls;
const json_t *j = response;
struct TALER_EXCHANGE_HttpResponse hr = {
.reply = j,
.http_status = (unsigned int) response_code
};
lh->job = NULL;
switch (response_code)
{
case 0:
hr.ec = TALER_EC_GENERIC_INVALID_RESPONSE;
break;
case MHD_HTTP_OK:
if (GNUNET_OK !=
parse_link_ok (lh,
j))
{
GNUNET_break_op (0);
hr.http_status = 0;
hr.ec = TALER_EC_GENERIC_REPLY_MALFORMED;
break;
}
GNUNET_assert (NULL == lh->link_cb);
TALER_EXCHANGE_link_cancel (lh);
return;
case MHD_HTTP_BAD_REQUEST:
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
/* This should never happen, either us or the exchange is buggy
(or API version conflict); just pass JSON reply to the application */
break;
case MHD_HTTP_NOT_FOUND:
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
/* Nothing really to verify, exchange says this coin was not melted; we
should pass the JSON reply to the application */
break;
case MHD_HTTP_INTERNAL_SERVER_ERROR:
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
/* Server had an internal issue; we should retry, but this API
leaves this to the application */
break;
default:
/* unexpected response code */
GNUNET_break_op (0);
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
"Unexpected response code %u/%d\n",
(unsigned int) response_code,
(int) hr.ec);
break;
}
if (NULL != lh->link_cb)
lh->link_cb (lh->link_cb_cls,
&hr,
0,
NULL,
NULL,
NULL);
TALER_EXCHANGE_link_cancel (lh);
}
/**
* Submit a link request to the exchange and get the exchange's response.
*
* This API is typically not used by anyone, it is more a threat against those
* trying to receive a funds transfer by abusing the refresh protocol.
*
* @param exchange the exchange handle; the exchange must be ready to operate
* @param coin_priv private key to request link data for
* @param link_cb the callback to call with the useful result of the
* refresh operation the @a coin_priv was involved in (if any)
* @param link_cb_cls closure for @a link_cb
* @return a handle for this request
*/
struct TALER_EXCHANGE_LinkHandle *
TALER_EXCHANGE_link (struct TALER_EXCHANGE_Handle *exchange,
const struct TALER_CoinSpendPrivateKeyP *coin_priv,
TALER_EXCHANGE_LinkCallback link_cb,
void *link_cb_cls)
{
struct TALER_EXCHANGE_LinkHandle *lh;
CURL *eh;
struct GNUNET_CURL_Context *ctx;
struct TALER_CoinSpendPublicKeyP coin_pub;
char arg_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2 + 32];
if (GNUNET_YES !=
TEAH_handle_is_ready (exchange))
{
GNUNET_break (0);
return NULL;
}
GNUNET_CRYPTO_eddsa_key_get_public (&coin_priv->eddsa_priv,
&coin_pub.eddsa_pub);
{
char pub_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2];
char *end;
end = GNUNET_STRINGS_data_to_string (&coin_pub,
sizeof (struct
TALER_CoinSpendPublicKeyP),
pub_str,
sizeof (pub_str));
*end = '\0';
GNUNET_snprintf (arg_str,
sizeof (arg_str),
"/coins/%s/link",
pub_str);
}
lh = GNUNET_new (struct TALER_EXCHANGE_LinkHandle);
lh->exchange = exchange;
lh->link_cb = link_cb;
lh->link_cb_cls = link_cb_cls;
lh->coin_priv = *coin_priv;
lh->url = TEAH_path_to_url (exchange,
arg_str);
eh = TALER_EXCHANGE_curl_easy_get_ (lh->url);
if (NULL == eh)
{
GNUNET_break (0);
GNUNET_free (lh->url);
GNUNET_free (lh);
return NULL;
}
ctx = TEAH_handle_to_context (exchange);
lh->job = GNUNET_CURL_job_add_with_ct_json (ctx,
eh,
&handle_link_finished,
lh);
return lh;
}
/**
* Cancel a link request. This function cannot be used
* on a request handle if the callback was already invoked.
*
* @param lh the link handle
*/
void
TALER_EXCHANGE_link_cancel (struct TALER_EXCHANGE_LinkHandle *lh)
{
if (NULL != lh->job)
{
GNUNET_CURL_job_cancel (lh->job);
lh->job = NULL;
}
GNUNET_free (lh->url);
GNUNET_free (lh);
}
/* end of exchange_api_link.c */
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