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/*
* Copyright (c) 2021 Alexandru Ardelean.
* Copyright (c) 2023 Eric Hawicz
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the MIT license. See COPYING for details.
*/
#include "config.h"
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "json_patch.h"
#include "json_object_private.h"
#include "json_pointer_private.h"
#include <limits.h>
#ifndef SIZE_T_MAX
#if SIZEOF_SIZE_T == SIZEOF_INT
#define SIZE_T_MAX UINT_MAX
#elif SIZEOF_SIZE_T == SIZEOF_LONG
#define SIZE_T_MAX ULONG_MAX
#elif SIZEOF_SIZE_T == SIZEOF_LONG_LONG
#define SIZE_T_MAX ULLONG_MAX
#else
#error Unable to determine size of size_t
#endif
#endif
#define _set_err(_errval, _errmsg) do { \
patch_error->errno_code = (_errval); \
patch_error->errmsg = (_errmsg); \
errno = 0; /* To avoid confusion */ \
} while (0)
#define _set_err_from_ptrget(_errval, _fieldname) do { \
patch_error->errno_code = (_errval); \
patch_error->errmsg = (_errval) == ENOENT ? \
"Did not find element referenced by " _fieldname " field" : \
"Invalid " _fieldname " field"; \
errno = 0; /* To avoid confusion */ \
} while(0)
/**
* JavaScript Object Notation (JSON) Patch
*/
static int json_patch_apply_test(struct json_object **res,
struct json_object *patch_elem,
const char *path, struct json_patch_error *patch_error)
{
struct json_object *value1, *value2;
if (!json_object_object_get_ex(patch_elem, "value", &value1)) {
_set_err(EINVAL, "Patch object does not contain a 'value' field");
return -1;
}
if (json_pointer_get(*res, path, &value2))
{
_set_err_from_ptrget(errno, "path");
return -1;
}
if (!json_object_equal(value1, value2)) {
_set_err(ENOENT, "Value of element referenced by 'path' field did not match 'value' field");
return -1;
}
return 0;
}
static int __json_patch_apply_remove(struct json_pointer_get_result *jpres)
{
if (json_object_is_type(jpres->parent, json_type_array)) {
return json_object_array_del_idx(jpres->parent, jpres->index_in_parent, 1);
} else if (jpres->parent && jpres->key_in_parent) {
json_object_object_del(jpres->parent, jpres->key_in_parent);
return 0;
} else {
// We're removing the root object
(void)json_object_put(jpres->obj);
jpres->obj = NULL;
return 0;
}
}
static int json_patch_apply_remove(struct json_object **res, const char *path, struct json_patch_error *patch_error)
{
struct json_pointer_get_result jpres;
int rc;
if (json_pointer_get_internal(*res, path, &jpres))
{
_set_err_from_ptrget(errno, "path");
return -1;
}
rc = __json_patch_apply_remove(&jpres);
if (rc < 0)
_set_err(EINVAL, "Unable to remove path referenced by 'path' field");
// This means we removed and freed the root object, i.e. *res
if (jpres.parent == NULL)
*res = NULL;
return rc;
}
// callback for json_pointer_set_with_array_cb()
static int json_object_array_insert_idx_cb(struct json_object *parent, size_t idx,
struct json_object *value, void *priv)
{
int rc;
int *add = priv;
if (idx > json_object_array_length(parent))
{
// Note: will propagate back out through json_pointer_set_with_array_cb()
errno = EINVAL;
return -1;
}
if (*add)
rc = json_object_array_insert_idx(parent, idx, value);
else
rc = json_object_array_put_idx(parent, idx, value);
if (rc < 0)
errno = EINVAL;
return rc;
}
static int json_patch_apply_add_replace(struct json_object **res,
struct json_object *patch_elem,
const char *path, int add, struct json_patch_error *patch_error)
{
struct json_object *value;
int rc;
if (!json_object_object_get_ex(patch_elem, "value", &value)) {
_set_err(EINVAL, "Patch object does not contain a 'value' field");
return -1;
}
/* if this is a replace op, then we need to make sure it exists before replacing */
if (!add && json_pointer_get(*res, path, NULL)) {
_set_err_from_ptrget(errno, "path");
return -1;
}
rc = json_pointer_set_with_array_cb(res, path, json_object_get(value),
json_object_array_insert_idx_cb, &add);
if (rc)
{
_set_err(errno, "Failed to set value at path referenced by 'path' field");
json_object_put(value);
}
return rc;
}
// callback for json_pointer_set_with_array_cb()
static int json_object_array_move_cb(struct json_object *parent, size_t idx,
struct json_object *value, void *priv)
{
int rc;
struct json_pointer_get_result *from = priv;
size_t len = json_object_array_length(parent);
/**
* If it's the same array parent, it means that we removed
* and element from it, so the length is temporarily reduced
* by 1, which means that if we try to move an element to
* the last position, we need to check the current length + 1
*/
if (parent == from->parent)
len++;
if (idx > len)
{
// Note: will propagate back out through json_pointer_set_with_array_cb()
errno = EINVAL;
return -1;
}
rc = json_object_array_insert_idx(parent, idx, value);
if (rc < 0)
errno = EINVAL;
return rc;
}
static int json_patch_apply_move_copy(struct json_object **res,
struct json_object *patch_elem,
const char *path, int move, struct json_patch_error *patch_error)
{
json_pointer_array_set_cb array_set_cb;
struct json_pointer_get_result from;
struct json_object *jfrom;
const char *from_s;
size_t from_s_len;
int rc;
if (!json_object_object_get_ex(patch_elem, "from", &jfrom)) {
_set_err(EINVAL, "Patch does not contain a 'from' field");
return -1;
}
from_s = json_object_get_string(jfrom);
from_s_len = strlen(from_s);
if (strncmp(from_s, path, from_s_len) == 0) {
/**
* If lengths match, it's a noop, if they don't,
* then we're trying to move a parent under a child
* which is not allowed as per RFC 6902 section 4.4
* The "from" location MUST NOT be a proper prefix of the "path"
* location; i.e., a location cannot be moved into one of its children.
*/
if (from_s_len == strlen(path))
return 0;
_set_err(EINVAL, "Invalid attempt to move parent under a child");
return -1;
}
rc = json_pointer_get_internal(*res, from_s, &from);
if (rc)
{
_set_err_from_ptrget(errno, "from");
return rc;
}
// Note: it's impossible for json_pointer to find the root obj, due
// to the path check above, so from.parent is guaranteed non-NULL
json_object_get(from.obj);
if (!move) {
array_set_cb = json_object_array_insert_idx_cb;
} else {
rc = __json_patch_apply_remove(&from);
if (rc < 0) {
json_object_put(from.obj);
return rc;
}
array_set_cb = json_object_array_move_cb;
}
rc = json_pointer_set_with_array_cb(res, path, from.obj, array_set_cb, &from);
if (rc)
{
_set_err(errno, "Failed to set value at path referenced by 'path' field");
json_object_put(from.obj);
}
return rc;
}
int json_patch_apply(struct json_object *copy_from, struct json_object *patch,
struct json_object **base, struct json_patch_error *patch_error)
{
size_t ii;
int rc = 0;
struct json_patch_error placeholder;
if (!patch_error)
patch_error = &placeholder;
patch_error->patch_failure_idx = SIZE_T_MAX;
patch_error->errno_code = 0;
if (base == NULL||
(*base == NULL && copy_from == NULL) ||
(*base != NULL && copy_from != NULL))
{
_set_err(EFAULT, "Exactly one of *base or copy_from must be non-NULL");
return -1;
}
if (!json_object_is_type(patch, json_type_array)) {
_set_err(EFAULT, "Patch object is not of type json_type_array");
return -1;
}
if (copy_from != NULL)
{
if (json_object_deep_copy(copy_from, base, NULL) < 0)
{
_set_err(ENOMEM, "Unable to copy copy_from using json_object_deep_copy()");
return -1;
}
}
/* Go through all operations ; apply them on res */
for (ii = 0; ii < json_object_array_length(patch); ii++) {
struct json_object *jop, *jpath;
struct json_object *patch_elem = json_object_array_get_idx(patch, ii);
const char *op, *path;
patch_error->patch_failure_idx = ii;
if (!json_object_object_get_ex(patch_elem, "op", &jop)) {
_set_err(EINVAL, "Patch object does not contain 'op' field");
return -1;
}
op = json_object_get_string(jop);
if (!json_object_object_get_ex(patch_elem, "path", &jpath)) {
_set_err(EINVAL, "Patch object does not contain 'path' field");
return -1;
}
path = json_object_get_string(jpath); // Note: empty string is ok!
if (!strcmp(op, "test"))
rc = json_patch_apply_test(base, patch_elem, path, patch_error);
else if (!strcmp(op, "remove"))
rc = json_patch_apply_remove(base, path, patch_error);
else if (!strcmp(op, "add"))
rc = json_patch_apply_add_replace(base, patch_elem, path, 1, patch_error);
else if (!strcmp(op, "replace"))
rc = json_patch_apply_add_replace(base, patch_elem, path, 0, patch_error);
else if (!strcmp(op, "move"))
rc = json_patch_apply_move_copy(base, patch_elem, path, 1, patch_error);
else if (!strcmp(op, "copy"))
rc = json_patch_apply_move_copy(base, patch_elem, path, 0, patch_error);
else {
_set_err(EINVAL, "Patch object has invalid 'op' field");
return -1;
}
if (rc < 0)
break;
}
return rc;
}