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/*
* Copyright (C) 2017 "IoT.bzh"
* Author José Bollo <jose.bollo@iot.bzh>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include "afb-perm.h"
#include "verbose.h"
/*********************************************************************
*** SECTION node
*********************************************************************/
/**
* types of nodes
*/
enum type
{
Text, /**< text node */
And, /**< and node */
Or, /**< or node */
Not /**< not node */
};
/**
* structure for nodes
*/
struct node
{
enum type type; /**< type of the node */
union {
struct node *children[2]; /**< possible subnodes */
char text[1]; /**< text of the node */
};
};
/**
* make a text node and return it
* @param type type of the node (should be Text)
* @param text the text to set for the node
* @param length the length of the text
* @return the allocated node or NULL on memory depletion
*/
static struct node *node_make_text(enum type type, const char *text, size_t length)
{
struct node *node;
node = malloc(length + sizeof *node);
if (!node)
errno = ENOMEM;
else {
node->type = type;
memcpy(node->text, text, length);
node->text[length] = 0;
}
return node;
}
/**
* make a node with sub nodes and return it
* @param type type of the node (should be And, Or or Text)
* @param left the "left" sub node
* @param right the "right" sub node (if any or NULL)
* @return the allocated node or NULL on memory depletion
*/
static struct node *node_make_parent(enum type type, struct node *left, struct node *right)
{
struct node *node;
node = malloc(sizeof *node);
if (!node)
errno = ENOMEM;
else {
node->type = type;
node->children[0] = left;
node->children[1] = right;
}
return node;
}
/**
* Frees the node and its possible subnodes
* @param node the node to free
*/
static void node_free(struct node *node)
{
struct node *left, *right;
if (node) {
switch (node->type) {
case Text:
free(node);
break;
case And:
case Or:
left = node->children[0];
right = node->children[1];
free(node);
node_free(left);
node_free(right);
break;
case Not:
left = node->children[0];
free(node);
node_free(left);
break;
}
}
}
/**
* Checks the permissions for the 'node' using the 'check' function
* and its 'closure'.
* @param node the node to check
* @param check the function that checks if a pernmission of 'name' is granted for 'closure'
* @param closure the context closure for the function 'check'
* @return 1 if the permission is granted or 0 otherwise
*/
static int node_check(struct node *node, int (*check)(void *closure, const char *name), void *closure)
{
for(;;) {
switch (node->type) {
case Text:
return check(closure, node->text);
case And:
if (!node_check(node->children[0], check, closure))
return 0;
break;
case Or:
if (node_check(node->children[0], check, closure))
return 1;
break;
case Not:
return !node_check(node->children[0], check, closure);
}
node = node->children[1];
}
}
/*********************************************************************
*** SECTION parse
*********************************************************************/
/**
* the symbol types
*/
enum symbol
{
TEXT, /**< a common text, name of a permission */
AND, /**< and keyword */
OR, /**< or keyword */
NOT, /**< not keyword */
OBRA, /**< open bracket */
CBRA, /**< close bracket */
END /**< end of input */
};
/**
* structure for parsing permission description
*/
struct parse
{
const char *desc; /**< initial permission description */
const char *symbol; /**< current symbol parsed */
size_t symlen; /**< length of the current symbol */
enum symbol type; /**< type of the current symbol */
};
/**
* updates parse to point to the next symbol if any
* @param parse parser state to update
*/
static void parse_next(struct parse *parse)
{
const char *scan;
size_t len;
/* skip current symbol */
scan = &parse->symbol[parse->symlen];
/* skip white spaces */
while (*scan && isspace(*scan))
scan++;
/* scan the symbol */
switch (*scan) {
case 0:
len = 0;
parse->type = END;
break;
case '(':
len = 1;
parse->type = OBRA;
break;
case ')':
len = 1;
parse->type = CBRA;
break;
default:
/* compute the length */
len = 0;
while (scan[len] && !isspace(scan[len]) && scan[len] != ')' && scan[len] != '(')
len++;
parse->type = TEXT;
/* fall to keyword if any */
switch(len) {
case 2:
if (!strncasecmp(scan, "or", len))
parse->type = OR;
break;
case 3:
if (!strncasecmp(scan, "and", len))
parse->type = AND;
else if (!strncasecmp(scan, "not", len))
parse->type = NOT;
break;
}
break;
}
parse->symbol = scan;
parse->symlen = len;
}
/**
* Init the parser state 'parse' for the description 'desc'
* @param parse the parser state to initialise
* @param desc the description of the permissions to be parsed
*/
static void parse_init(struct parse *parse, const char *desc)
{
parse->desc = desc;
parse->symbol = desc;
parse->symlen = 0;
parse_next(parse);
}
/*********************************************************************
*** SECTION node_parse
*********************************************************************/
static struct node *node_parse_or(struct parse *parse);
/**
* Parse a permission name
* @param parser the parser state
* @return the parsed node or NULL in case of error
* in case of error errno is set to EINVAL or ENOMEM
*/
static struct node *node_parse_text(struct parse *parse)
{
struct node *node;
if (parse->type == TEXT) {
node = node_make_text(Text, parse->symbol, parse->symlen);
parse_next(parse);
} else {
errno = EINVAL;
node = NULL;
}
return node;
}
/**
* Parse a term that is either a name (text) or a sub expression
* enclosed in brackets.
* @param parser the parser state
* @return the parsed node or NULL in case of error
* in case of error errno is set to EINVAL or ENOMEM
*/
static struct node *node_parse_term(struct parse *parse)
{
struct node *node;
if (parse->type != OBRA)
node = node_parse_text(parse);
else {
parse_next(parse);
node = node_parse_or(parse);
if (parse->type == CBRA)
parse_next(parse);
else {
errno = EINVAL;
node_free(node);
node = NULL;
}
}
return node;
}
/**
* Parse a term potentially prefixed by not.
* @param parser the parser state
* @return the parsed node or NULL in case of error
* in case of error errno is set to EINVAL or ENOMEM
*/
static struct node *node_parse_not(struct parse *parse)
{
struct node *node, *not;
if (parse->type != NOT)
node = node_parse_term(parse);
else {
parse_next(parse);
node = node_parse_term(parse);
if (node) {
not = node_make_parent(Not, node, NULL);
if (not)
node = not;
else {
node_free(node);
node = NULL;
}
}
}
return node;
}
/**
* Parse a potential sequence of terms connected with the
* given operator (AND or OR). The function takes care to
* create an evaluation tree that respects the order given
* by the description and that will limit the recursivity
* depth.
* @param parser the parser state
* @param operator the symbol type of the operator scanned
* @param subparse the function for parsing terms of the sequence
* @param type the node type corresponding to the operator
* @return the parsed node or NULL in case of error
* in case of error errno is set to EINVAL or ENOMEM
*/
static struct node *node_parse_infix(
struct parse *parse,
enum symbol operator,
struct node *(*subparse)(struct parse*),
enum type type
)
{
struct node *root, **up, *right, *node;
root = subparse(parse);
if (root) {
up = &root;
while (parse->type == operator) {
parse_next(parse);
right = subparse(parse);
if (!right) {
node_free(root);
root = NULL;
break;
}
node = node_make_parent(type, *up, right);
if (!node) {
node_free(right);
node_free(root);
root = NULL;
break;
}
*up = node;
up = &node->children[1];
}
}
return root;
}
/**
* Parse a potential sequence of anded terms.
* @param parser the parser state
* @return the parsed node or NULL in case of error
* in case of error errno is set to EINVAL or ENOMEM
*/
static struct node *node_parse_and(struct parse *parse)
{
return node_parse_infix(parse, AND, node_parse_not, And);
}
/**
* Parse a potential sequence of ored terms.
* @param parser the parser state
* @return the parsed node or NULL in case of error
* in case of error errno is set to EINVAL or ENOMEM
*/
static struct node *node_parse_or(struct parse *parse)
{
return node_parse_infix(parse, OR, node_parse_and, Or);
}
/**
* Parse description of permissions.
* @param desc the description to parse
* @return the parsed node or NULL in case of error
* in case of error errno is set to EINVAL or ENOMEM
*/
static struct node *node_parse(const char *desc)
{
struct node *node;
struct parse parse;
parse_init(&parse, desc);
node = node_parse_or(&parse);
if (node && parse.type != END) {
node_free(node);
node = NULL;
}
return node;
}
/*********************************************************************
*** SECTION perm
*********************************************************************/
/**
* structure for storing permissions
*/
struct afb_perm
{
struct node *root; /**< root node descripbing the permission */
int refcount; /**< the count of use of the structure */
};
/**
* allocates the structure for the given root
* @param root the root node to keep
* @return the created permission object or NULL
*/
static struct afb_perm *make_perm(struct node *root)
{
struct afb_perm *perm;
perm = malloc(sizeof *perm);
if (!perm)
errno = ENOMEM;
else {
perm->root = root;
perm->refcount = 1;
}
return perm;
}
/**
* Creates the permission for the given description
* @param desc the description of the permission to create
* @return the created permission object or NULL
*/
struct afb_perm *afb_perm_parse(const char *desc)
{
struct node *root;
struct afb_perm *perm;
root = node_parse(desc);
if (root) {
perm = make_perm(root);
if (perm)
return perm;
node_free(root);
}
return NULL;
}
/**
* Adds a reference to the permissions
* @param perm the permission to reference
*/
void afb_perm_addref(struct afb_perm *perm)
{
assert(perm);
perm->refcount++;
}
/**
* Removes a reference to the permissions
* @param perm the permission to dereference
*/
void afb_perm_unref(struct afb_perm *perm)
{
if (perm && !--perm->refcount) {
node_free(perm->root);
free(perm);
}
}
/**
* Checks permission 'perm' using the 'check' function
* and its 'closure'.
* @param perm the permission to check
* @param check the function that checks if a pernmission of 'name' is granted for 'closure'
* @param closure the context closure for the function 'check'
* @return 1 if the permission is granted or 0 otherwise
*/
int afb_perm_check(struct afb_perm *perm, int (*check)(void *closure, const char *name), void *closure)
{
return node_check(perm->root, check, closure);
}
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