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Diffstat (limited to 'src/lib/exchange_api_withdraw.c')
| -rw-r--r-- | src/lib/exchange_api_withdraw.c | 611 |
1 files changed, 611 insertions, 0 deletions
diff --git a/src/lib/exchange_api_withdraw.c b/src/lib/exchange_api_withdraw.c new file mode 100644 index 000000000..c63235377 --- /dev/null +++ b/src/lib/exchange_api_withdraw.c @@ -0,0 +1,611 @@ +/* + This file is part of TALER + Copyright (C) 2014-2020 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_withdraw.c + * @brief Implementation of the /reserves/$RESERVE_PUB/withdraw requests + * @author Christian Grothoff + */ +#include "platform.h" +#include <jansson.h> +#include <microhttpd.h> /* just for HTTP status codes */ +#include <gnunet/gnunet_util_lib.h> +#include <gnunet/gnunet_json_lib.h> +#include <gnunet/gnunet_curl_lib.h> +#include "taler_exchange_service.h" +#include "taler_json_lib.h" +#include "exchange_api_handle.h" +#include "taler_signatures.h" +#include "exchange_api_curl_defaults.h" + + +/** + * @brief A Withdraw Handle + */ +struct TALER_EXCHANGE_WithdrawHandle +{ + + /** + * The connection to exchange this request handle will use + */ + struct TALER_EXCHANGE_Handle *exchange; + + /** + * The url for this request. + */ + char *url; + + /** + * Context for #TEH_curl_easy_post(). Keeps the data that must + * persist for Curl to make the upload. + */ + struct TALER_CURL_PostContext ctx; + + /** + * Handle for the request. + */ + struct GNUNET_CURL_Job *job; + + /** + * Function to call with the result. + */ + TALER_EXCHANGE_WithdrawCallback cb; + + /** + * Secrets of the planchet. + */ + struct TALER_PlanchetSecretsP ps; + + /** + * Denomination key we are withdrawing. + */ + struct TALER_EXCHANGE_DenomPublicKey pk; + + /** + * Closure for @a cb. + */ + void *cb_cls; + + /** + * Hash of the public key of the coin we are signing. + */ + struct GNUNET_HashCode c_hash; + + /** + * Public key of the reserve we are withdrawing from. + */ + struct TALER_ReservePublicKeyP reserve_pub; + +}; + + +/** + * We got a 200 OK response for the /reserves/$RESERVE_PUB/withdraw operation. + * Extract the coin's signature and return it to the caller. The signature we + * get from the exchange is for the blinded value. Thus, we first must + * unblind it and then should verify its validity against our coin's hash. + * + * If everything checks out, we return the unblinded signature + * to the application via the callback. + * + * @param wh operation handle + * @param json reply from the exchange + * @return #GNUNET_OK on success, #GNUNET_SYSERR on errors + */ +static int +reserve_withdraw_ok (struct TALER_EXCHANGE_WithdrawHandle *wh, + const json_t *json) +{ + struct GNUNET_CRYPTO_RsaSignature *blind_sig; + struct TALER_FreshCoin fc; + struct GNUNET_JSON_Specification spec[] = { + GNUNET_JSON_spec_rsa_signature ("ev_sig", + &blind_sig), + GNUNET_JSON_spec_end () + }; + + if (GNUNET_OK != + GNUNET_JSON_parse (json, + spec, + NULL, NULL)) + { + GNUNET_break_op (0); + return GNUNET_SYSERR; + } + if (GNUNET_OK != + TALER_planchet_to_coin (&wh->pk.key, + blind_sig, + &wh->ps, + &wh->c_hash, + &fc)) + { + GNUNET_break_op (0); + GNUNET_JSON_parse_free (spec); + return GNUNET_SYSERR; + } + GNUNET_JSON_parse_free (spec); + + /* signature is valid, return it to the application */ + wh->cb (wh->cb_cls, + MHD_HTTP_OK, + TALER_EC_NONE, + &fc.sig, + json); + /* make sure callback isn't called again after return */ + wh->cb = NULL; + GNUNET_CRYPTO_rsa_signature_free (fc.sig.rsa_signature); + return GNUNET_OK; +} + + +/** + * We got a 409 CONFLICT response for the /reserves/$RESERVE_PUB/withdraw operation. + * Check the signatures on the withdraw transactions in the provided + * history and that the balances add up. We don't do anything directly + * with the information, as the JSON will be returned to the application. + * However, our job is ensuring that the exchange followed the protocol, and + * this in particular means checking all of the signatures in the history. + * + * @param wh operation handle + * @param json reply from the exchange + * @return #GNUNET_OK on success, #GNUNET_SYSERR on errors + */ +static int +reserve_withdraw_payment_required (struct + TALER_EXCHANGE_WithdrawHandle *wh, + const json_t *json) +{ + struct TALER_Amount balance; + struct TALER_Amount balance_from_history; + struct TALER_Amount requested_amount; + json_t *history; + size_t len; + struct GNUNET_JSON_Specification spec[] = { + TALER_JSON_spec_amount ("balance", &balance), + GNUNET_JSON_spec_end () + }; + + if (GNUNET_OK != + GNUNET_JSON_parse (json, + spec, + NULL, NULL)) + { + GNUNET_break_op (0); + return GNUNET_SYSERR; + } + history = json_object_get (json, + "history"); + if (NULL == history) + { + GNUNET_break_op (0); + return GNUNET_SYSERR; + } + + /* go over transaction history and compute + total incoming and outgoing amounts */ + len = json_array_size (history); + { + struct TALER_EXCHANGE_ReserveHistory *rhistory; + + /* Use heap allocation as "len" may be very big and thus this may + not fit on the stack. Use "GNUNET_malloc_large" as a malicious + exchange may theoretically try to crash us by giving a history + that does not fit into our memory. */ + rhistory = GNUNET_malloc_large (sizeof (struct + TALER_EXCHANGE_ReserveHistory) + * len); + if (NULL == rhistory) + { + GNUNET_break (0); + return GNUNET_SYSERR; + } + + if (GNUNET_OK != + TALER_EXCHANGE_parse_reserve_history (wh->exchange, + history, + &wh->reserve_pub, + balance.currency, + &balance_from_history, + len, + rhistory)) + { + GNUNET_break_op (0); + TALER_EXCHANGE_free_reserve_history (rhistory, + len); + return GNUNET_SYSERR; + } + TALER_EXCHANGE_free_reserve_history (rhistory, + len); + } + + if (0 != + TALER_amount_cmp (&balance_from_history, + &balance)) + { + /* exchange cannot add up balances!? */ + GNUNET_break_op (0); + return GNUNET_SYSERR; + } + /* Compute how much we expected to charge to the reserve */ + if (GNUNET_OK != + TALER_amount_add (&requested_amount, + &wh->pk.value, + &wh->pk.fee_withdraw)) + { + /* Overflow here? Very strange, our CPU must be fried... */ + GNUNET_break (0); + return GNUNET_SYSERR; + } + /* Check that funds were really insufficient */ + if (0 >= TALER_amount_cmp (&requested_amount, + &balance)) + { + /* Requested amount is smaller or equal to reported balance, + so this should not have failed. */ + GNUNET_break_op (0); + return GNUNET_SYSERR; + } + return GNUNET_OK; +} + + +/** + * Function called when we're done processing the + * HTTP /reserves/$RESERVE_PUB/withdraw request. + * + * @param cls the `struct TALER_EXCHANGE_WithdrawHandle` + * @param response_code HTTP response code, 0 on error + * @param response parsed JSON result, NULL on error + */ +static void +handle_reserve_withdraw_finished (void *cls, + long response_code, + const void *response) +{ + struct TALER_EXCHANGE_WithdrawHandle *wh = cls; + const json_t *j = response; + + wh->job = NULL; + switch (response_code) + { + case 0: + break; + case MHD_HTTP_OK: + if (GNUNET_OK != + reserve_withdraw_ok (wh, + j)) + { + GNUNET_break_op (0); + response_code = 0; + } + 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 */ + break; + case MHD_HTTP_CONFLICT: + /* The exchange says that the reserve has insufficient funds; + check the signatures in the history... */ + if (GNUNET_OK != + reserve_withdraw_payment_required (wh, + j)) + { + GNUNET_break_op (0); + response_code = 0; + } + break; + case MHD_HTTP_FORBIDDEN: + GNUNET_break (0); + /* Nothing really to verify, exchange says one of the signatures is + invalid; as we checked them, this should never happen, we + should pass the JSON reply to the application */ + break; + case MHD_HTTP_NOT_FOUND: + /* Nothing really to verify, the exchange basically just says + that it doesn't know this reserve. Can happen if we + query before the wire transfer went through. + We should simply pass the JSON reply to the application. */ + break; + case MHD_HTTP_INTERNAL_SERVER_ERROR: + /* Server had an internal issue; we should retry, but this API + leaves this to the application */ + break; + default: + /* unexpected response code */ + GNUNET_log (GNUNET_ERROR_TYPE_ERROR, + "Unexpected response code %u\n", + (unsigned int) response_code); + GNUNET_break (0); + response_code = 0; + break; + } + if (NULL != wh->cb) + { + wh->cb (wh->cb_cls, + response_code, + TALER_JSON_get_error_code (j), + NULL, + j); + wh->cb = NULL; + } + TALER_EXCHANGE_withdraw_cancel (wh); +} + + +/** + * Helper function for #TALER_EXCHANGE_withdraw2() and + * #TALER_EXCHANGE_withdraw(). + * + * @param exchange the exchange handle; the exchange must be ready to operate + * @param pk kind of coin to create + * @param reserve_sig signature from the reserve authorizing the withdrawal + * @param reserve_pub public key of the reserve to withdraw from + * @param ps secrets of the planchet + * caller must have committed this value to disk before the call (with @a pk) + * @param pd planchet details matching @a ps + * @param res_cb the callback to call when the final result for this request is available + * @param res_cb_cls closure for @a res_cb + * @return NULL + * if the inputs are invalid (i.e. denomination key not with this exchange). + * In this case, the callback is not called. + */ +struct TALER_EXCHANGE_WithdrawHandle * +reserve_withdraw_internal (struct TALER_EXCHANGE_Handle *exchange, + const struct TALER_EXCHANGE_DenomPublicKey *pk, + const struct TALER_ReserveSignatureP *reserve_sig, + const struct TALER_ReservePublicKeyP *reserve_pub, + const struct TALER_PlanchetSecretsP *ps, + const struct TALER_PlanchetDetail *pd, + TALER_EXCHANGE_WithdrawCallback res_cb, + void *res_cb_cls) +{ + struct TALER_EXCHANGE_WithdrawHandle *wh; + struct GNUNET_CURL_Context *ctx; + json_t *withdraw_obj; + CURL *eh; + struct GNUNET_HashCode h_denom_pub; + char arg_str[sizeof (struct TALER_ReservePublicKeyP) * 2 + 32]; + + { + char pub_str[sizeof (struct TALER_ReservePublicKeyP) * 2]; + char *end; + + end = GNUNET_STRINGS_data_to_string (reserve_pub, + sizeof (struct + TALER_ReservePublicKeyP), + pub_str, + sizeof (pub_str)); + *end = '\0'; + GNUNET_snprintf (arg_str, + sizeof (arg_str), + "/reserves/%s/withdraw", + pub_str); + } + wh = GNUNET_new (struct TALER_EXCHANGE_WithdrawHandle); + wh->exchange = exchange; + wh->cb = res_cb; + wh->cb_cls = res_cb_cls; + wh->pk = *pk; + wh->pk.key.rsa_public_key + = GNUNET_CRYPTO_rsa_public_key_dup (pk->key.rsa_public_key); + wh->reserve_pub = *reserve_pub; + wh->c_hash = pd->c_hash; + GNUNET_CRYPTO_rsa_public_key_hash (pk->key.rsa_public_key, + &h_denom_pub); + withdraw_obj = json_pack ("{s:o, s:o," /* denom_pub_hash and coin_ev */ + " s:o}",/* reserve_pub and reserve_sig */ + "denom_pub_hash", GNUNET_JSON_from_data_auto ( + &h_denom_pub), + "coin_ev", GNUNET_JSON_from_data (pd->coin_ev, + pd->coin_ev_size), + "reserve_sig", GNUNET_JSON_from_data_auto ( + reserve_sig)); + if (NULL == withdraw_obj) + { + GNUNET_break (0); + GNUNET_CRYPTO_rsa_public_key_free (wh->pk.key.rsa_public_key); + GNUNET_free (wh); + return NULL; + } + GNUNET_log (GNUNET_ERROR_TYPE_INFO, + "Attempting to withdraw from reserve %s\n", + TALER_B2S (reserve_pub)); + wh->ps = *ps; + wh->url = TEAH_path_to_url (exchange, + arg_str); + eh = TEL_curl_easy_get (wh->url); + if (GNUNET_OK != + TALER_curl_easy_post (&wh->ctx, + eh, + withdraw_obj)) + { + GNUNET_break (0); + curl_easy_cleanup (eh); + json_decref (withdraw_obj); + GNUNET_free (wh->url); + GNUNET_CRYPTO_rsa_public_key_free (wh->pk.key.rsa_public_key); + GNUNET_free (wh); + return NULL; + } + json_decref (withdraw_obj); + ctx = TEAH_handle_to_context (exchange); + wh->job = GNUNET_CURL_job_add2 (ctx, + eh, + wh->ctx.headers, + &handle_reserve_withdraw_finished, + wh); + return wh; +} + + +/** + * Withdraw a coin from the exchange using a /reserve/withdraw request. Note + * that to ensure that no money is lost in case of hardware failures, + * the caller must have committed (most of) the arguments to disk + * before calling, and be ready to repeat the request with the same + * arguments in case of failures. + * + * @param exchange the exchange handle; the exchange must be ready to operate + * @param pk kind of coin to create + * @param reserve_priv private key of the reserve to withdraw from + * @param ps secrets of the planchet + * caller must have committed this value to disk before the call (with @a pk) + * @param res_cb the callback to call when the final result for this request is available + * @param res_cb_cls closure for the above callback + * @return handle for the operation on success, NULL on error, i.e. + * if the inputs are invalid (i.e. denomination key not with this exchange). + * In this case, the callback is not called. + */ +struct TALER_EXCHANGE_WithdrawHandle * +TALER_EXCHANGE_withdraw (struct TALER_EXCHANGE_Handle *exchange, + const struct TALER_EXCHANGE_DenomPublicKey *pk, + const struct + TALER_ReservePrivateKeyP *reserve_priv, + const struct TALER_PlanchetSecretsP *ps, + TALER_EXCHANGE_WithdrawCallback + res_cb, + void *res_cb_cls) +{ + struct TALER_Amount amount_with_fee; + struct TALER_ReserveSignatureP reserve_sig; + struct TALER_WithdrawRequestPS req; + struct TALER_PlanchetDetail pd; + struct TALER_EXCHANGE_WithdrawHandle *wh; + + GNUNET_CRYPTO_eddsa_key_get_public (&reserve_priv->eddsa_priv, + &req.reserve_pub.eddsa_pub); + req.purpose.size = htonl (sizeof (struct TALER_WithdrawRequestPS)); + req.purpose.purpose = htonl (TALER_SIGNATURE_WALLET_RESERVE_WITHDRAW); + if (GNUNET_OK != + TALER_amount_add (&amount_with_fee, + &pk->fee_withdraw, + &pk->value)) + { + /* exchange gave us denomination keys that overflow like this!? */ + GNUNET_break_op (0); + return NULL; + } + TALER_amount_hton (&req.amount_with_fee, + &amount_with_fee); + TALER_amount_hton (&req.withdraw_fee, + &pk->fee_withdraw); + if (GNUNET_OK != + TALER_planchet_prepare (&pk->key, + ps, + &pd)) + { + GNUNET_break_op (0); + return NULL; + } + req.h_denomination_pub = pd.denom_pub_hash; + GNUNET_CRYPTO_hash (pd.coin_ev, + pd.coin_ev_size, + &req.h_coin_envelope); + GNUNET_assert (GNUNET_OK == + GNUNET_CRYPTO_eddsa_sign (&reserve_priv->eddsa_priv, + &req.purpose, + &reserve_sig.eddsa_signature)); + wh = reserve_withdraw_internal (exchange, + pk, + &reserve_sig, + &req.reserve_pub, + ps, + &pd, + res_cb, + res_cb_cls); + GNUNET_free (pd.coin_ev); + return wh; +} + + +/** + * Withdraw a coin from the exchange using a /reserve/withdraw + * request. This API is typically used by a wallet to withdraw a tip + * where the reserve's signature was created by the merchant already. + * + * Note that to ensure that no money is lost in case of hardware + * failures, the caller must have committed (most of) the arguments to + * disk before calling, and be ready to repeat the request with the + * same arguments in case of failures. + * + * @param exchange the exchange handle; the exchange must be ready to operate + * @param pk kind of coin to create + * @param reserve_sig signature from the reserve authorizing the withdrawal + * @param reserve_pub public key of the reserve to withdraw from + * @param ps secrets of the planchet + * caller must have committed this value to disk before the call (with @a pk) + * @param res_cb the callback to call when the final result for this request is available + * @param res_cb_cls closure for @a res_cb + * @return NULL + * if the inputs are invalid (i.e. denomination key not with this exchange). + * In this case, the callback is not called. + */ +struct TALER_EXCHANGE_WithdrawHandle * +TALER_EXCHANGE_withdraw2 (struct TALER_EXCHANGE_Handle *exchange, + const struct + TALER_EXCHANGE_DenomPublicKey *pk, + const struct + TALER_ReserveSignatureP *reserve_sig, + const struct + TALER_ReservePublicKeyP *reserve_pub, + const struct TALER_PlanchetSecretsP *ps, + TALER_EXCHANGE_WithdrawCallback + res_cb, + void *res_cb_cls) +{ + struct TALER_EXCHANGE_WithdrawHandle *wh; + struct TALER_PlanchetDetail pd; + + if (GNUNET_OK != + TALER_planchet_prepare (&pk->key, + ps, + &pd)) + { + GNUNET_break_op (0); + return NULL; + } + wh = reserve_withdraw_internal (exchange, + pk, + reserve_sig, + reserve_pub, + ps, + &pd, + res_cb, + res_cb_cls); + GNUNET_free (pd.coin_ev); + return wh; +} + + +/** + * Cancel a withdraw status request. This function cannot be used + * on a request handle if a response is already served for it. + * + * @param sign the withdraw sign request handle + */ +void +TALER_EXCHANGE_withdraw_cancel (struct TALER_EXCHANGE_WithdrawHandle *wh) +{ + if (NULL != wh->job) + { + GNUNET_CURL_job_cancel (wh->job); + wh->job = NULL; + } + GNUNET_free (wh->url); + TALER_curl_easy_post_finished (&wh->ctx); + GNUNET_CRYPTO_rsa_public_key_free (wh->pk.key.rsa_public_key); + GNUNET_free (wh); +} |