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first draft for #6365, test pending

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This commit is contained in:
Christian Grothoff 2020-07-16 01:51:45 +02:00
parent 90e756ddea
commit e1ad498bff
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GPG Key ID: 939E6BE1E29FC3CC
3 changed files with 417 additions and 12 deletions
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25
src/include/taler_json_lib.h
View File

@ -158,6 +158,31 @@ int
TALER_JSON_contract_hash (const json_t *json,
struct GNUNET_HashCode *hc);
/**
* Mark part of a contract object as 'forgettable'.
*
* @param[in,out] json some JSON object to modify
* @param field name of the field to mark as forgettable
* @return #GNUNET_OK on success, #GNUNET_SYSERR on error
*/
int
TALER_JSON_contract_mark_forgettable (json_t *json,
const char *field);
/**
* Forget part of a contract object.
*
* @param[in,out] json some JSON object to modify
* @param field name of the field to forget
* @return #GNUNET_OK on success, #GNUNET_SYSERR on error
*/
int
TALER_JSON_contract_part_forget (json_t *json,
const char *field);
/**
* Extract the Taler error code from the given @a json object.
* Note that #TALER_EC_NONE is returned if no "code" is present.

400
src/json/json.c
View File

@ -1,6 +1,6 @@
/*
This file is part of TALER
Copyright (C) 2014, 2015, 2016 Taler Systems SA
Copyright (C) 2014, 2015, 2016, 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
@ -25,7 +25,235 @@
/**
* Hash a JSON object for binary signing.
* Dump the @a json to a string and hash it.
*
* @param json value to hash
* @param salt salt value to include when using HKDF,
* NULL to not use any salt and to use SHA512
* @param[out] hc where to store the hash
* @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
*/
static int
dump_and_hash (const json_t *json,
const char *salt,
struct GNUNET_HashCode *hc)
{
char *wire_enc;
size_t len;
if (NULL == (wire_enc = json_dumps (json,
JSON_COMPACT | JSON_SORT_KEYS)))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
len = strlen (wire_enc) + 1;
if (NULL == salt)
{
GNUNET_CRYPTO_hash (wire_enc,
len,
hc);
}
else
{
if (GNUNET_YES !=
GNUNET_CRYPTO_kdf (hc,
sizeof (*hc),
salt,
strlen (salt) + 1,
wire_enc,
len,
NULL,
0))
{
free (wire_enc);
return GNUNET_SYSERR;
}
}
free (wire_enc);
return GNUNET_OK;
}
/**
* Replace "forgettable" parts of a JSON object with its salted hash.
*
* @param[in] in some JSON value
* @return NULL on error
*/
static json_t *
forget (const json_t *in)
{
if (json_is_array (in))
{
/* array is a JSON array */
size_t index;
json_t *value;
json_t *ret;
ret = json_array ();
if (NULL == ret)
{
GNUNET_break (0);
return NULL;
}
json_array_foreach (in, index, value) {
json_t *t;
t = forget (value);
if (NULL == t)
{
GNUNET_break (0);
json_decref (ret);
return NULL;
}
if (0 != json_array_append_new (ret, t))
{
GNUNET_break (0);
json_decref (ret);
return NULL;
}
}
return ret;
}
if (! json_is_object (in))
{
json_t *ret;
const char *key;
json_t *value;
json_t *fg;
json_t *rx;
fg = json_object_get (in,
"_forgettable");
rx = json_object_get (in,
"_forgotten");
if (NULL != rx)
rx = json_deep_copy (rx); /* should be shallow
by structure, but
deep copy is safer */
ret = json_object ();
if (NULL == ret)
{
GNUNET_break (0);
return NULL;
}
json_object_foreach ((json_t*) in, key, value) {
json_t *t;
json_t *salt;
if (0 == strcmp (key,
"_forgettable"))
continue; /* skip! */
if (rx == value)
continue; /* skip! */
t = forget (value);
if (NULL == t)
{
GNUNET_break (0);
json_decref (ret);
json_decref (rx);
return NULL;
}
if ( (NULL != fg) &&
(NULL != (salt = json_object_get (fg,
key))) )
{
/* 't' is to be forgotten! */
struct GNUNET_HashCode hc;
if (! json_is_string (salt))
{
GNUNET_break (0);
json_decref (ret);
json_decref (rx);
return NULL;
}
if (GNUNET_OK !=
dump_and_hash (t,
json_string_value (salt),
&hc))
{
GNUNET_break (0);
json_decref (ret);
json_decref (rx);
return NULL;
}
if (NULL == rx)
rx = json_object ();
if (NULL == rx)
{
GNUNET_break (0);
json_decref (ret);
json_decref (rx);
return NULL;
}
if (0 !=
json_object_set_new (rx,
key,
GNUNET_JSON_from_data_auto (&hc)))
{
GNUNET_break (0);
json_decref (ret);
json_decref (rx);
return NULL;
}
if (0 !=
json_object_set_new (ret,
key,
json_null ()))
{
GNUNET_break (0);
json_decref (ret);
json_decref (rx);
return NULL;
}
}
else
{
/* 't' to be used without 'forgetting' */
if (0 !=
json_object_set_new (ret,
key,
t))
{
GNUNET_break (0);
json_decref (ret);
json_decref (rx);
return NULL;
}
}
} /* json_object_foreach */
if (0 !=
json_object_set_new (ret,
"_forgotten",
rx))
{
GNUNET_break (0);
json_decref (ret);
return NULL;
}
return ret;
}
return json_incref ((json_t *) in);
}
/**
* Hash a JSON contract for binary signing.
*
* Contracts can contain "forgettable" parts. Those components of the JSON
* object are indicated in a "_forgettable" field containing key-value
* pairs. The keys are the names of other fields that are forgettable, and the
* values are salt values to be used in the HKDF when hashing the forgettable
* field. To compute the overall hash, the values of all "_forgettable" fields
* are replaced with 'null', and the "_forgettable" field itself is removed,
* and a special "_forgotten" field is added with a map of forgotten entries
* to the respective HKDF values (see also #6365).
*
* Forgetting parts is not only applied at the top-level entry of the
* contract, but recursively to all entries.
*
* See https://tools.ietf.org/html/draft-rundgren-json-canonicalization-scheme-15
* for fun JSON canonicalization problems. Callers must ensure that
@ -41,20 +269,172 @@ int
TALER_JSON_contract_hash (const json_t *json,
struct GNUNET_HashCode *hc)
{
char *wire_enc;
size_t len;
int ret;
json_t *cjson;
if (NULL == (wire_enc = json_dumps (json,
JSON_COMPACT | JSON_SORT_KEYS)))
cjson = forget (json);
if (NULL == cjson)
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
len = strlen (wire_enc) + 1;
GNUNET_CRYPTO_hash (wire_enc,
len,
ret = dump_and_hash (cjson,
NULL,
hc);
free (wire_enc);
json_decref (cjson);
return ret;
}
/**
* Mark part of a contract object as 'forgettable'.
*
* @param[in,out] json some JSON object to modify
* @param field name of the field to mark as forgettable
* @return #GNUNET_OK on success, #GNUNET_SYSERR on error
*/
int
TALER_JSON_contract_mark_forgettable (json_t *json,
const char *field)
{
json_t *fg;
struct GNUNET_ShortHashCode salt;
if (! json_is_object (json))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
if (NULL == json_object_get (json,
field))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
fg = json_object_get (json,
"_forgettable");
if (NULL == fg)
{
fg = json_object ();
if (0 !=
json_object_set_new (json,
"_forgettable",
fg))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
}
GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_NONCE,
&salt,
sizeof (salt));
if (0 !=
json_object_set_new (fg,
field,
GNUNET_JSON_from_data_auto (&salt)))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
return GNUNET_OK;
}
/**
* Forget part of a contract object.
*
* @param[in,out] json some JSON object to modify
* @param field name of the field to forget
* @return #GNUNET_OK on success, #GNUNET_SYSERR on error
*/
int
TALER_JSON_contract_part_forget (json_t *json,
const char *field)
{
const json_t *fg;
const json_t *part;
json_t *fp;
json_t *rx;
struct GNUNET_HashCode hc;
const char *salt;
if (! json_is_object (json))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
if (NULL == (part = json_object_get (json,
field)))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
fg = json_object_get (json,
"_forgettable");
if (NULL == fg)
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
salt = json_string_value (json_object_get (fg,
field));
if (NULL == salt)
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
/* need to recursively forget to compute 'hc' */
fp = forget (part);
if (NULL == fp)
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
if (GNUNET_OK !=
dump_and_hash (fp,
salt,
&hc))
{
json_decref (fp);
GNUNET_break (0);
return GNUNET_SYSERR;
}
json_decref (fp);
rx = json_object_get (json,
"_forgotten");
if (NULL == rx)
{
rx = json_object ();
if (0 !=
json_object_set_new (json,
"_forgotten",
rx))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
}
/* remember field as 'forgotten' */
if (0 !=
json_object_set_new (rx,
field,
GNUNET_JSON_from_data_auto (&hc)))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
/* finally, set 'forgotten' field to null */
if (0 !=
json_object_set_new (json,
field,
json_null ()))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
return GNUNET_OK;
}

2
src/json/test_json.c
View File

@ -1,6 +1,6 @@
/*
This file is part of TALER
(C) 2015, 2016 Taler Systems SA
(C) 2015, 2016, 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