cache-control.c

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/*
 * Copyright 2019 John-Mark Bell <jmb@netsurf-browser.org>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * NetSurf 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; version 2 of the License.
 *
 * NetSurf 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <limits.h>
#include <stdlib.h>
 
#include "utils/corestrings.h"
#include "utils/http.h"
 
#include "utils/http/generics.h"
#include "utils/http/primitives.h"
 
/**
 * Representation of a Cache-Control
 */
struct http_cache_control {
        uint32_t max_age;               /**< Max age (delta seconds) */
        bool max_age_valid;             /**< Whether max-age is valid */
        bool no_cache;                  /**< Whether caching is forbidden */
        bool no_store;                  /**< Whether persistent caching is forbidden */
};
 
/**
 * Representation of a directive
 */
typedef struct http_directive {
        http__item base;
 
        lwc_string *name;               /**< Parameter name */
        lwc_string *value;              /**< Parameter value (optional) */
} http_directive;
 
 
static void http_destroy_directive(http_directive *self)
{
        lwc_string_unref(self->name);
        lwc_string_unref(self->value);
        free(self);
}
 
static nserror http__parse_directive(const char **input,
                http_directive **result)
{
        const char *pos = *input;
        lwc_string *name;
        lwc_string *value = NULL;
        http_directive *directive;
        nserror error;
 
        /* token [ "=" ( token | quoted-string ) ] */
 
        error = http__parse_token(&pos, &name);
        if (error != NSERROR_OK)
                return error;
 
        http__skip_LWS(&pos);
 
        if (*pos == '=') {
                pos++;
 
                http__skip_LWS(&pos);
 
                if (*pos == '"')
                        error = http__parse_quoted_string(&pos, &value);
                else
                        error = http__parse_token(&pos, &value);
 
                if (error != NSERROR_OK) {
                        lwc_string_unref(name);
                        return error;
                }
        }
 
        directive = malloc(sizeof(*directive));
        if (directive == NULL) {
                lwc_string_unref(value);
                lwc_string_unref(name);
                return NSERROR_NOMEM;
        }
 
        HTTP__ITEM_INIT(directive, NULL, http_destroy_directive);
        directive->name = name;
        directive->value = value;
 
        *result = directive;
        *input = pos;
 
        return NSERROR_OK;
}
 
static void http_directive_list_destroy(http_directive *list)
{
        http__item_list_destroy(list);
}
 
static nserror http_directive_list_find_item(const http_directive *list,
                lwc_string *name, lwc_string **value)
{
        bool match;
 
        while (list != NULL) {
                if (lwc_string_caseless_isequal(name, list->name,
                                &match) == lwc_error_ok && match)
                        break;
 
                list = (http_directive *) list->base.next;
        }
 
        if (list == NULL)
                return NSERROR_NOT_FOUND;
 
        if (list->value != NULL) {
                *value = lwc_string_ref(list->value);
        } else {
                *value = NULL;
        }
 
        return NSERROR_OK;
}
 
static const http_directive *http_directive_list_iterate(
                const http_directive *cur,
                lwc_string **name, lwc_string **value)
{
        if (cur == NULL)
                return NULL;
 
        *name = lwc_string_ref(cur->name);
        if (cur->value != NULL) {
                *value = lwc_string_ref(cur->value);
        } else {
                *value = NULL;
        }
 
        return (http_directive *) cur->base.next;
}
 
static uint32_t count(const http_directive *list, lwc_string *key)
{
        uint32_t count = 0;
        bool match;
 
        while (list != NULL) {
                if (lwc_string_caseless_isequal(key, list->name,
                                &match) == lwc_error_ok && match) {
                        count++;
                }
 
                list = (http_directive *) list->base.next;
        }
 
        return count;
}
 
static bool check_duplicates(const http_directive *directives)
{
        bool result = true;
        const http_directive *key = directives;
 
        if (key == NULL) {
                /* No directives, so there can't be any duplicates */
                return true;
        }
 
        do {
                lwc_string *name = NULL, *value = NULL;
 
                key = http_directive_list_iterate(key, &name, &value);
 
                result &= (count(directives, name) == 1);
 
                lwc_string_unref(name);
                lwc_string_unref(value);
        } while (key != NULL);
 
        return result;
}
 
static nserror parse_max_age(lwc_string *value, uint32_t *result)
{
        const char *pos = lwc_string_data(value);
        const char *end = pos + lwc_string_length(value);
        uint32_t val = 0;
 
        /* 1*DIGIT */
 
        if (pos == end) {
                /* Blank value */
                return NSERROR_NOT_FOUND;
        }
 
        while (pos < end) {
                if ('0' <= *pos && *pos <= '9') {
                        uint32_t nv = val * 10 + (*pos - '0');
                        if (nv < val) {
                                val = UINT_MAX;
                        } else {
                                val = nv;
                        }
                } else {
                        /* Non-digit */
                        return NSERROR_NOT_FOUND;
                }
 
                pos++;
        }
 
        *result = val;
 
        return NSERROR_OK;
}
 
/* See cache-control.h for documentation */
nserror http_parse_cache_control(const char *header_value,
                http_cache_control **result)
{
        const char *pos = header_value;
        http_cache_control *cc;
        http_directive *first = NULL;
        http_directive *directives = NULL;
        lwc_string *value_str = NULL;
        uint32_t max_age = 0;
        bool max_age_valid = false;
        bool no_cache = false;
        bool no_store = false;
        nserror error;
 
        /* 1#cache-directive */
 
        http__skip_LWS(&pos);
 
        error = http__parse_directive(&pos, &first);
        if (error != NSERROR_OK) {
                return error;
        }
 
        http__skip_LWS(&pos);
 
        if (*pos == ',') {
                error = http__item_list_parse(&pos,
                                http__parse_directive, first, &directives);
                if (error != NSERROR_OK) {
                        if (directives != NULL) {
                                http_directive_list_destroy(directives);
                        }
                        return error;
                }
        } else {
                directives = first;
        }
 
        /* Each directive must only appear once */
        if (check_duplicates(directives) == false) {
                http_directive_list_destroy(directives);
                return NSERROR_NOT_FOUND;
        }
 
        /* Find max-age */
        error = http_directive_list_find_item(directives,
                        corestring_lwc_max_age, &value_str);
        if (error == NSERROR_OK && value_str != NULL) {
                error = parse_max_age(value_str, &max_age);
                max_age_valid = (error == NSERROR_OK);
                lwc_string_unref(value_str);
        }
 
        /* Find no-cache */
        error = http_directive_list_find_item(directives,
                        corestring_lwc_no_cache, &value_str);
        if (error == NSERROR_OK) {
                no_cache = true;
                lwc_string_unref(value_str);
        }
 
        /* Find no-store */
        error = http_directive_list_find_item(directives,
                        corestring_lwc_no_store, &value_str);
        if (error == NSERROR_OK) {
                no_store = true;
                lwc_string_unref(value_str);
        }
 
        http_directive_list_destroy(directives);
 
        cc = malloc(sizeof(*cc));
        if (cc == NULL) {
                return NSERROR_NOMEM;
        }
 
        cc->max_age = max_age;
        cc->max_age_valid = max_age_valid;
        cc->no_cache = no_cache;
        cc->no_store = no_store;
 
        *result = cc;
 
        return NSERROR_OK;
}
 
/* See cache-control.h for documentation */
void http_cache_control_destroy(http_cache_control *victim)
{
        free(victim);
}
 
/* See cache-control.h for documentation */
bool http_cache_control_has_max_age(http_cache_control *cc)
{
        return cc->max_age_valid;
}
 
/* See cache-control.h for documentation */
uint32_t http_cache_control_max_age(http_cache_control *cc)
{
        return cc->max_age;
}
 
/* See cache-control.h for documentation */
bool http_cache_control_no_cache(http_cache_control *cc)
{
        return cc->no_cache;
}
 
/* See cache-control.h for documentation */
bool http_cache_control_no_store(http_cache_control *cc)
{
        return cc->no_store;
}