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add cmd line option to restrict timetravel, minor code cleanup of keystate logic

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This commit is contained in:
Christian Grothoff 2020-03-17 17:33:30 +01:00
parent fb47c680b1
commit c17909d820
No known key found for this signature in database
GPG Key ID: 939E6BE1E29FC3CC
5 changed files with 213 additions and 106 deletions
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12
src/exchange/taler-exchange-httpd.c
View File

@ -82,6 +82,14 @@ char *TEH_exchange_directory;
*/
char *TEH_revocation_directory;
/**
* Are clients allowed to request /keys for times other than the
* current time? Allowing this could be abused in a DoS-attack
* as building new /keys responses is expensive. Should only be
* enabled for testcases, development and test systems.
*/
int TEH_allow_keys_timetravel;
/**
* The exchange's configuration (global)
*/
@ -1183,6 +1191,10 @@ main (int argc,
char *logfile = NULL;
int connection_close = GNUNET_NO;
const struct GNUNET_GETOPT_CommandLineOption options[] = {
GNUNET_GETOPT_option_flag ('a',
"allow-timetravel",
"allow clients to request /keys for arbitrary timestamps (for testing and development only)",
&TEH_allow_keys_timetravel),
GNUNET_GETOPT_option_flag ('C',
"connection-close",
"force HTTP connections to be closed after each request",

8
src/exchange/taler-exchange-httpd.h
View File

@ -43,6 +43,14 @@ extern struct GNUNET_CONFIGURATION_Handle *TEH_cfg;
*/
extern char *TEH_exchange_directory;
/**
* Are clients allowed to request /keys for times other than the
* current time? Allowing this could be abused in a DoS-attack
* as building new /keys responses is expensive. Should only be
* enabled for testcases, development and test systems.
*/
extern int TEH_allow_keys_timetravel;
/**
* Main directory with revocation data.
*/

249
src/exchange/taler-exchange-httpd_keystate.c
View File

@ -121,7 +121,7 @@ struct KeysResponseData
{
/**
* Response to return if the client supports (gzip) compression.
* Response to return if the client supports (deflate) compression.
*/
struct MHD_Response *response_compressed;
@ -211,15 +211,15 @@ struct ResponseFactoryContext
*/
struct TEH_KS_StateHandle *key_state;
/**
* Length of the @e denomkey_array.
*/
unsigned int denomkey_array_length;
/**
* Time stamp used as "now".
*/
struct GNUNET_TIME_Absolute now;
/**
* Length of the @e denomkey_array.
*/
unsigned int denomkey_array_length;
};
@ -249,7 +249,7 @@ struct TEH_KS_StateHandle
struct GNUNET_CONTAINER_MultiHashMap *revoked_map;
/**
* Sorted array of responses to /keys (sorted by cherry-picking date) of
* Sorted array of responses to /keys (MUST be sorted by cherry-picking date) of
* length @e krd_array_length;
*/
struct KeysResponseData *krd_array;
@ -309,6 +309,12 @@ static struct TEH_KS_StateHandle *internal_key_state;
*/
static pthread_mutex_t internal_key_state_mutex = PTHREAD_MUTEX_INITIALIZER;
/**
* Configuration value LOOKAHEAD_PROVIDE that says for how far in the
* future we want to provide exchange key information to clients.
*/
static struct GNUNET_TIME_Relative conf_duration_provide;
/* ************************** Clean up logic *********************** */
@ -368,6 +374,11 @@ destroy_response_builder (struct ResponseBuilderContext *rbc)
json_decref (rbc->auditors_array);
rbc->auditors_array = NULL;
}
if (NULL != rbc->hash_context)
{
GNUNET_CRYPTO_hash_context_abort (rbc->hash_context);
rbc->hash_context = NULL;
}
}
@ -447,7 +458,7 @@ ks_free (struct TEH_KS_StateHandle *key_state)
/**
* Pipe used for signaling reloading of our key state.
*/
static int reload_pipe[2];
static int reload_pipe[2] = { -1, -1 };
/**
@ -458,23 +469,15 @@ static int reload_pipe[2];
static void
handle_signal (int signal_number)
{
ssize_t res;
char c = signal_number;
char c = (char) signal_number; /* never seen a signal_number > 127 on any platform */
res = write (reload_pipe[1],
(void) ! write (reload_pipe[1],
&c,
1);
if ( (res < 0) &&
(EINTR != errno) )
{
GNUNET_break (0);
return;
}
if (0 == res)
{
GNUNET_break (0);
return;
}
/* While one might like to "handle errors" here, even logging via fprintf()
isn't safe inside of a signal handler. So there is nothing we safely CAN
do. OTOH, also very little that can go wrong in pratice. Calling _exit()
on errors might be a possibility, but that might do more harm than good. *///
}
@ -482,11 +485,10 @@ handle_signal (int signal_number)
/**
* Convert the public part of a denomination key issue to a JSON
* object.
* Convert the public part of denomination key data to a JSON object.
*
* @param pk public key of the denomination key
* @param dki the denomination key issue
* @param pk public key of the denomination
* @param dki the denomination key issue information
* @return a JSON object describing the denomination key isue (public part)
*/
static json_t *
@ -511,7 +513,9 @@ denom_key_issue_to_json (
TALER_amount_ntoh (&fee_refund,
&dki->properties.fee_refund);
return
json_pack ("{s:o, s:o, s:o, s:o, s:o, s:o, s:o, s:o, s:o, s:o, s:o}",
json_pack ("{s:o, s:o, s:o, s:o, s:o,"
" s:o, s:o, s:o, s:o, s:o,"
" s:o}",
"master_sig",
GNUNET_JSON_from_data_auto (&dki->signature),
"stamp_start",
@ -526,6 +530,7 @@ denom_key_issue_to_json (
"stamp_expire_legal",
GNUNET_JSON_from_time_abs (GNUNET_TIME_absolute_ntoh (
dki->properties.expire_legal)),
/* 5 entries until here */
"denom_pub",
GNUNET_JSON_from_rsa_public_key (pk->rsa_public_key),
"value",
@ -536,6 +541,7 @@ denom_key_issue_to_json (
TALER_JSON_from_amount (&fee_deposit),
"fee_refresh",
TALER_JSON_from_amount (&fee_refresh),
/* 10 entries until here */
"fee_refund",
TALER_JSON_from_amount (&fee_refund));
}
@ -553,20 +559,37 @@ static int
store_in_map (struct GNUNET_CONTAINER_MultiHashMap *map,
const struct TALER_EXCHANGEDB_DenominationKey *dki)
{
struct TALER_EXCHANGEDB_DenominationKey *d2;
int res;
/* First, we verify that the @a dki is actually well-formed. While it comes
from our own hard disk, there is the possibility of missconfiguration
(i.e. bogus file in the directory), or that the administrator used the
wrong master public key, and we should not accept entries that are not
well-formed. *///
{
const struct TALER_EXCHANGEDB_DenominationKeyInformationP *dkip;
struct TALER_DenominationKeyValidityPS denom_key_issue;
dkip = &dki->issue;
denom_key_issue = dkip->properties;
/* The above is straight from our disk. We should not trust
that it is well-formed, so we setup crucial fields ourselves. */
denom_key_issue.purpose.purpose
= htonl (TALER_SIGNATURE_MASTER_DENOMINATION_KEY_VALIDITY);
denom_key_issue.purpose.size
= htonl (sizeof (struct TALER_DenominationKeyValidityPS));
denom_key_issue.master = TEH_master_public_key;
/* Check that the data we read matches our expectations */
if (0 !=
GNUNET_memcmp (&denom_key_issue,
&dkip->properties))
{
GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
"Invalid fields in denomination key `%s'\n",
GNUNET_h2s (&dkip->properties.denom_hash));
return GNUNET_SYSERR;
}
/* Also check the signature by the master public key */
if (GNUNET_SYSERR ==
GNUNET_CRYPTO_eddsa_verify (
TALER_SIGNATURE_MASTER_DENOMINATION_KEY_VALIDITY,
@ -581,28 +604,37 @@ store_in_map (struct GNUNET_CONTAINER_MultiHashMap *map,
}
}
/* We need to make a deep copy of the @a dki, as the original was allocated
elsewhere and will be freed by the caller. */
{
struct TALER_EXCHANGEDB_DenominationKey *d2;
d2 = GNUNET_new (struct TALER_EXCHANGEDB_DenominationKey);
d2->issue = dki->issue;
if (NULL != dki->denom_priv.rsa_private_key)
d2->denom_priv.rsa_private_key
= GNUNET_CRYPTO_rsa_private_key_dup (dki->denom_priv.rsa_private_key);
d2->denom_pub.rsa_public_key
= GNUNET_CRYPTO_rsa_public_key_dup (dki->denom_pub.rsa_public_key);
res = GNUNET_CONTAINER_multihashmap_put (map,
if (GNUNET_OK !=
GNUNET_CONTAINER_multihashmap_put (map,
&d2->issue.properties.denom_hash,
d2,
GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY);
if (GNUNET_OK != res)
GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
{
GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
"Duplicate denomination key `%s'\n",
GNUNET_h2s (&d2->issue.properties.denom_hash));
if (NULL != d2->denom_priv.rsa_private_key)
GNUNET_CRYPTO_rsa_private_key_free (d2->denom_priv.rsa_private_key);
GNUNET_CRYPTO_rsa_public_key_free (d2->denom_pub.rsa_public_key);
GNUNET_free (d2);
return GNUNET_NO;
}
/* finish *deep* part of deep copy */
if (NULL != dki->denom_priv.rsa_private_key)
{
/* we might be past the withdraw period, so private key could have been deleted,
so only try to (deep) copy if non-NULL. */
d2->denom_priv.rsa_private_key
= GNUNET_CRYPTO_rsa_private_key_dup (dki->denom_priv.rsa_private_key);
}
d2->denom_pub.rsa_public_key
= GNUNET_CRYPTO_rsa_public_key_dup (dki->denom_pub.rsa_public_key);
}
return GNUNET_OK;
}
@ -624,33 +656,6 @@ struct AddRevocationContext
};
/**
* Get the relative time value that describes how
* far in the future do we want to provide coin keys.
*
* @return the provide duration
*/
static struct GNUNET_TIME_Relative
TALER_EXCHANGE_conf_duration_provide (void)
{
struct GNUNET_TIME_Relative rel;
if (GNUNET_OK !=
GNUNET_CONFIGURATION_get_value_time (TEH_cfg,
"exchange",
"LOOKAHEAD_PROVIDE",
&rel))
{
GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
"exchange",
"LOOKAHEAD_PROVIDE",
"time value required");
GNUNET_assert (0);
}
return rel;
}
/**
* Execute transaction to add revocations.
*
@ -771,7 +776,7 @@ reload_keys_denom_iter (void *cls,
}
horizon = GNUNET_TIME_absolute_add (rfc->now,
TALER_EXCHANGE_conf_duration_provide ());
conf_duration_provide);
start = GNUNET_TIME_absolute_ntoh (dki->issue.properties.start);
if (start.abs_value_us > horizon.abs_value_us)
{
@ -944,8 +949,7 @@ reload_keys_sign_iter (
struct GNUNET_TIME_Absolute now;
struct GNUNET_TIME_Absolute horizon;
horizon = GNUNET_TIME_relative_to_absolute (
TALER_EXCHANGE_conf_duration_provide ());
horizon = GNUNET_TIME_relative_to_absolute (conf_duration_provide);
if (GNUNET_TIME_absolute_ntoh (ski->issue.start).abs_value_us >
horizon.abs_value_us)
{
@ -1127,7 +1131,9 @@ initialize_denomkey_array (void *cls,
/**
* Comparator used to sort the `struct DenominationKeyEntry` array
* by the validity period's starting time of the keys.
* by the validity period's starting time of the keys. Must match
* the expected sorting by cherry_pick_date (which is based on the
* issue.properties.start) used in #krd_search_comparator.
*
* @param k1 a `struct DenominationKeyEntry *`
* @param k2 a `struct DenominationKeyEntry *`
@ -1460,7 +1466,6 @@ build_keys_response (const struct ResponseFactoryContext *rfc,
&free_auditor_entry,
NULL);
GNUNET_CONTAINER_multihashmap_destroy (auditors);
GNUNET_CRYPTO_hash_context_abort (rbc.hash_context);
return GNUNET_SYSERR;
}
}
@ -1822,6 +1827,8 @@ make_fresh_key_state (struct GNUNET_TIME_Absolute now)
if (last.abs_value_us == d.abs_value_us)
continue;
/* must be monotonically increasing as per qsort() call above: */
GNUNET_assert (last.abs_value_us < d.abs_value_us);
last = d;
off++;
}
@ -2277,11 +2284,31 @@ static struct GNUNET_SIGNAL_Context *sigchld;
/**
* Setup initial #internal_key_state.
* Setup initial #internal_key_state and our signal handlers.
*/
int
TEH_KS_init (void)
{
if (GNUNET_OK !=
GNUNET_CONFIGURATION_get_value_time (TEH_cfg,
"exchange",
"LOOKAHEAD_PROVIDE",
&conf_duration_provide))
{
GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
"exchange",
"LOOKAHEAD_PROVIDE",
"time value required");
return GNUNET_SYSERR;
}
if (0 == conf_duration_provide.rel_value_us)
{
GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
"exchange",
"LOOKAHEAD_PROVIDE",
"value cannot be zero");
return GNUNET_SYSERR;
}
if (0 != pipe (reload_pipe))
{
GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
@ -2312,7 +2339,7 @@ TEH_KS_init (void)
/**
* Finally release #internal_key_state.
* Finally release #internal_key_state and our signal handlers.
*/
void
TEH_KS_free (void)
@ -2322,18 +2349,43 @@ TEH_KS_free (void)
/* Note: locking is no longer be required, as we are again
single-threaded. */
ks = internal_key_state;
if (NULL == ks)
return;
if (NULL != ks)
{
GNUNET_assert (1 == ks->refcnt);
ks->refcnt--;
ks_free (ks);
}
if (NULL != sigusr1)
{
GNUNET_SIGNAL_handler_uninstall (sigusr1);
sigusr1 = NULL;
}
if (NULL != sigterm)
{
GNUNET_SIGNAL_handler_uninstall (sigterm);
sigterm = NULL;
}
if (NULL != sigint)
{
GNUNET_SIGNAL_handler_uninstall (sigint);
sigint = NULL;
}
if (NULL != sighup)
{
GNUNET_SIGNAL_handler_uninstall (sighup);
sighup = NULL;
}
if (NULL != sigchld)
{
GNUNET_SIGNAL_handler_uninstall (sigchld);
sigchld = NULL;
}
if (-1 != reload_pipe[0])
{
GNUNET_break (0 == close (reload_pipe[0]));
GNUNET_break (0 == close (reload_pipe[1]));
reload_pipe[0] = reload_pipe[1] = -1;
}
}
@ -2356,10 +2408,11 @@ TEH_KS_sign (const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
key_state = TEH_KS_acquire (GNUNET_TIME_absolute_get ());
if (NULL == key_state)
{
/* This *can* happen if the exchange's keys are
not properly maintained. */
/* This *can* happen if the exchange's keys are not properly maintained
(i.e. administrator forgets to provision us with non-expired signing
keys or to send signal to reload keys after provisioning). */
GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
"Cannot sign request, no valid keys available\n");
"Cannot sign request, no valid signing keys available. Were they properly provisioned and did you signal the exchange to reload the keys?\n");
return GNUNET_SYSERR;
}
*pub = key_state->current_sign_key_issue.issue.signkey_pub;
@ -2374,8 +2427,8 @@ TEH_KS_sign (const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
/**
* Comparator used for a binary search for @a key in the
* `struct KeysResponseData` array.
* Comparator used for a binary search by cherry_pick_date for @a key in the
* `struct KeysResponseData` array. See libc's qsort() and bsearch() functions.
*
* @param key pointer to a `struct GNUNET_TIME_Absolute`
* @param value pointer to a `struct KeysResponseData` array entry
@ -2437,6 +2490,10 @@ TEH_handler_keys (const struct TEH_RequestHandler *rh,
TALER_EC_KEYS_HAVE_NOT_NUMERIC,
"last_issue_date");
}
/* The following multiplication may overflow; but this should not really
be a problem, as giving back 'older' data than what the client asks for
(given that the client asks for data in the distant future) is not
problematic */
last_issue_date.abs_value_us = (uint64_t) cherrypickn * 1000000LLU;
}
else
@ -2458,12 +2515,27 @@ TEH_handler_keys (const struct TEH_RequestHandler *rh,
{
GNUNET_break_op (0);
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_BAD_REQUEST,
MHD_HTTP_FORBIDDEN,
TALER_EC_KEYS_HAVE_NOT_NUMERIC,
"now");
}
if (TEH_allow_keys_timetravel)
{
/* The following multiplication may overflow; but this should not really
be a problem, as giving back 'older' data than what the client asks for
(given that the client asks for data in the distant future) is not
problematic */
now.abs_value_us = (uint64_t) fakenown * 1000000LLU;
}
else
{
/* Option not allowed by configuration */
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_BAD_REQUEST,
TALER_EC_KEYS_TIMETRAVEL_FORBIDDEN,
"timetravel not allowed by this exchange");
}
}
GNUNET_log (GNUNET_ERROR_TYPE_INFO,
"Handling request for /keys (%s/%s)\n",
have_cherrypick,
@ -2474,11 +2546,14 @@ TEH_handler_keys (const struct TEH_RequestHandler *rh,
key_state = TEH_KS_acquire (now);
if (NULL == key_state)
{
TALER_LOG_ERROR ("Lacking keys to operate\n");
/* Maybe client picked time stamp too far in the future? In that case,
#MHD_HTTP_INTERNAL_SERVER_ERROR might be missleading, could be more like a
NOT_FOUND situation. But, OTOH, for 'sane' clients it is more likely
to be our fault, so let's speculatively assume we are to blame ;-) */
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_EXCHANGE_BAD_CONFIGURATION,
"no keys");
"no keys for requested time");
}
krd = bsearch (&last_issue_date,
key_state->krd_array,
@ -2501,6 +2576,10 @@ TEH_handler_keys (const struct TEH_RequestHandler *rh,
}
if (NULL == krd)
{
/* Maybe client picked time stamp too far in the future? In that case,
"INTERNAL_SERVER_ERROR" might be missleading, could be more like a
NOT_FOUND situation. But, OTOH, for 'sane' clients it is more likely
to be our fault, so let's speculatively assume we are to blame ;-) *///
GNUNET_break (0);
TEH_KS_release (key_state);
return TALER_MHD_reply_with_error (connection,

7
src/include/taler_error_codes.h
View File

@ -1051,6 +1051,13 @@ enum TALER_ErrorCode
*/
TALER_EC_KEYS_MISSING = 1901,
/**
* This exchange does not allow clients to request /keys for times
* other than the current (exchange) time. This reponse is provied
* with an HTTP status code of MHD_HTTP_FORBIDDEN.
*/
TALER_EC_KEYS_TIMETRAVEL_FORBIDDEN = 1902,
/**
* The backend could not find the merchant instance specified in the
* request. This response is provided with HTTP status code

1
src/testing/testing_api_helpers_exchange.c
View File

@ -762,6 +762,7 @@ TALER_TESTING_setup_with_exchange_cfg (void *cls,
NULL, NULL, NULL,
"taler-exchange-httpd",
"taler-exchange-httpd",
"-a", /* some tests may need timetravel */
"-c", setup_ctx->config_filename,
NULL);