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-fix withdraw logic idempotency broken yesterday: did not handle expired DKs nicely

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This commit is contained in:
Christian Grothoff 2021-12-05 08:58:12 +01:00
parent e61a53806e
commit c0d2af8a49
No known key found for this signature in database
GPG Key ID: 939E6BE1E29FC3CC
1 changed files with 105 additions and 61 deletions
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166
src/exchange/taler-exchange-httpd_withdraw.c
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@ -33,14 +33,6 @@
#include "taler-exchange-httpd_keys.h"
/**
* Perform RSA signature before checking with the database?
* Reduces time spent in transaction, but may cause us to
* waste CPU time if DB check fails.
*/
#define OPTIMISTIC_SIGN 1
/**
* Send reserve history information to client with the
* message that we have insufficient funds for the
@ -175,15 +167,8 @@ accumulate_withdraws (void *cls,
* IF it returns the soft error code, the function MAY be called again
* to retry and MUST not queue a MHD response.
*
* Note that "wc->collectable.sig" may already be set before entering
* this function, either because OPTIMISTIC_SIGN was used and we signed
* before entering the transaction, or because this function is run
* twice (!) by #TEH_DB_run_transaction() and the first time created
* the signature and then failed to commit. Furthermore, we may get
* a 2nd correct signature briefly if "get_withdraw_info" succeeds and
* finds one in the DB. To avoid signing twice, the function may
* return a valid signature in "wc->collectable.sig" **even if it failed**.
* The caller must thus free the signature in either case.
* Note that "wc->collectable.sig" is set before entering this function as we
* signed before entering the transaction.
*
* @param cls a `struct WithdrawContext *`
* @param connection MHD request which triggered the transaction
@ -201,14 +186,12 @@ withdraw_transaction (void *cls,
enum GNUNET_DB_QueryStatus qs;
struct TALER_BlindedDenominationSignature denom_sig;
#if OPTIMISTIC_SIGN
/* store away optimistic signature to protect
it from being overwritten by get_withdraw_info */
denom_sig = wc->collectable.sig;
memset (&wc->collectable.sig,
0,
sizeof (wc->collectable.sig));
#endif
qs = TEH_plugin->get_withdraw_info (TEH_plugin->cls,
&wc->wsrd.h_coin_envelope,
&wc->collectable);
@ -234,15 +217,13 @@ withdraw_transaction (void *cls,
/* Toss out the optimistic signature, we got another one from the DB;
optimization trade-off loses in this case: we unnecessarily computed
a signature :-( */
#if OPTIMISTIC_SIGN
TALER_blinded_denom_sig_free (&denom_sig);
#endif
return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
}
/* We should never get more than one result, and we handled
the errors (negative case) above, so that leaves no results. */
GNUNET_assert (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs);
wc->collectable.sig = denom_sig; /* Note: might still be NULL if we didn't do OPTIMISTIC_SIGN */
wc->collectable.sig = denom_sig;
/* Check if balance is sufficient */
r.pub = wc->wsrd.reserve_pub; /* other fields of 'r' initialized in reserves_get (if successful) */
@ -370,27 +351,7 @@ withdraw_transaction (void *cls,
}
}
/* Balance is good, sign the coin! */
#if ! OPTIMISTIC_SIGN
if (NULL == wc->collectable.sig.rsa_signature)
{
enum TALER_ErrorCode ec = TALER_EC_NONE;
wc->collectable.sig
= TEH_keys_denomination_sign (&wc->denom_pub_hash,
wc->blinded_msg,
wc->blinded_msg_len,
&ec);
if (TALER_EC_NONE != ec)
{
GNUNET_break (0);
*mhd_ret = TALER_MHD_reply_with_ec (connection,
ec,
NULL);
return GNUNET_DB_STATUS_HARD_ERROR;
}
}
#endif
/* Balance is good, persist signature */
wc->collectable.denom_pub_hash = wc->denom_pub_hash;
wc->collectable.amount_with_fee = wc->amount_required;
wc->collectable.reserve_pub = wc->wsrd.reserve_pub;
@ -416,6 +377,50 @@ withdraw_transaction (void *cls,
}
/**
* Check if the @a rc is replayed and we already have an
* answer. If so, replay the existing answer and return the
* HTTP response.
*
* @param rc request context
* @param[in,out] wc parsed request data
* @param[out] mret HTTP status, set if we return true
* @return true if the request is idempotent with an existing request
* false if we did not find the request in the DB and did not set @a mret
*/
static bool
check_request_idempotent (struct TEH_RequestContext *rc,
struct WithdrawContext *wc,
MHD_RESULT *mret)
{
enum GNUNET_DB_QueryStatus qs;
qs = TEH_plugin->get_withdraw_info (TEH_plugin->cls,
&wc->wsrd.h_coin_envelope,
&wc->collectable);
if (0 > qs)
{
GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR == qs);
if (GNUNET_DB_STATUS_HARD_ERROR == qs)
*mret = TALER_MHD_reply_with_error (rc->connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_GENERIC_DB_FETCH_FAILED,
"get_withdraw_info");
return true; /* well, kind-of */
}
if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
return false;
/* generate idempotent reply */
*mret = TALER_MHD_REPLY_JSON_PACK (
rc->connection,
MHD_HTTP_OK,
TALER_JSON_pack_blinded_denom_sig ("ev_sig",
&wc->collectable.sig));
TALER_blinded_denom_sig_free (&wc->collectable.sig);
return true;
}
MHD_RESULT
TEH_handler_withdraw (struct TEH_RequestContext *rc,
const json_t *root,
@ -463,12 +468,38 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
{
MHD_RESULT mret;
struct GNUNET_TIME_Absolute now;
struct TEH_KeyStateHandle *ksh;
dk = TEH_keys_denomination_by_hash (&wc.denom_pub_hash,
rc->connection,
&mret);
ksh = TEH_keys_get_state ();
if (NULL == ksh)
{
if (! check_request_idempotent (rc,
&wc,
&mret))
{
GNUNET_JSON_parse_free (spec);
return TALER_MHD_reply_with_error (rc->connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
NULL);
}
GNUNET_JSON_parse_free (spec);
return mret;
}
dk = TEH_keys_denomination_by_hash2 (ksh,
&wc.denom_pub_hash,
NULL,
NULL);
if (NULL == dk)
{
if (! check_request_idempotent (rc,
&wc,
&mret))
{
GNUNET_JSON_parse_free (spec);
return TEH_RESPONSE_reply_unknown_denom_pub_hash (rc->connection,
&wc.denom_pub_hash);
}
GNUNET_JSON_parse_free (spec);
return mret;
}
@ -481,13 +512,20 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
now = GNUNET_TIME_absolute_get ();
(void) GNUNET_TIME_round_abs (&now);
/* This denomination is past the expiration time for withdraws */
if (! check_request_idempotent (rc,
&wc,
&mret))
{
GNUNET_JSON_parse_free (spec);
return TEH_RESPONSE_reply_expired_denom_pub_hash (
rc->connection,
&wc.denom_pub_hash,
now,
TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
"WITHDRAW");
}
GNUNET_JSON_parse_free (spec);
return TEH_RESPONSE_reply_expired_denom_pub_hash (
rc->connection,
&wc.denom_pub_hash,
now,
TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
"WITHDRAW");
return mret;
}
if (GNUNET_TIME_absolute_is_future (dk->meta.start))
{
@ -495,7 +533,8 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
now = GNUNET_TIME_absolute_get ();
(void) GNUNET_TIME_round_abs (&now);
/* This denomination is not yet valid */
/* This denomination is not yet valid, no need to check
for idempotency! */
GNUNET_JSON_parse_free (spec);
return TEH_RESPONSE_reply_expired_denom_pub_hash (
rc->connection,
@ -511,13 +550,20 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
now = GNUNET_TIME_absolute_get ();
(void) GNUNET_TIME_round_abs (&now);
/* This denomination has been revoked */
if (! check_request_idempotent (rc,
&wc,
&mret))
{
GNUNET_JSON_parse_free (spec);
return TEH_RESPONSE_reply_expired_denom_pub_hash (
rc->connection,
&wc.denom_pub_hash,
now,
TALER_EC_EXCHANGE_GENERIC_DENOMINATION_REVOKED,
"WITHDRAW");
}
GNUNET_JSON_parse_free (spec);
return TEH_RESPONSE_reply_expired_denom_pub_hash (
rc->connection,
&wc.denom_pub_hash,
now,
TALER_EC_EXCHANGE_GENERIC_DENOMINATION_REVOKED,
"WITHDRAW");
return mret;
}
}
@ -562,7 +608,6 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
NULL);
}
#if OPTIMISTIC_SIGN
/* Sign before transaction! */
ec = TALER_EC_NONE;
wc.collectable.sig
@ -578,7 +623,6 @@ TEH_handler_withdraw (struct TEH_RequestContext *rc,
ec,
NULL);
}
#endif
/* run transaction and sign (if not optimistically signed before) */
wc.kyc_denied = false;