summaryrefslogtreecommitdiff
path: root/README.input_filter
blob: e2941d029ee4e89f8880c46d41a7e8fc60a7fbc3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
Input Filter Support in PHP 5
-----------------------------

XSS (Cross Site Scripting) hacks are becoming more and more prevalent,
and can be quite difficult to prevent.  Whenever you accept user data
and somehow display this data back to users, you are likely vulnerable
to XSS hacks.

The Input Filter support in PHP 5 is aimed at providing the framework
through which a company-wide or site-wide security policy can be
enforced.  It is implemented as a SAPI hook and is called from the
treat_data and post handler functions.  To implement your own security
policy you will need to write a standard PHP extension.  There is also
a powerful standard implementation in ext/filter that should suit most
peoples' needs.  However, if you want to implement your own security 
policy, read on.

A simple implementation might look like the following.  This stores the
original raw user data and adds a my_get_raw() function while the normal
$_POST, $_GET and $_COOKIE arrays are only populated with stripped
data.  In this simple example all I am doing is calling strip_tags() on
the data.

ZEND_BEGIN_MODULE_GLOBALS(my_input_filter)
        zval *post_array;
        zval *get_array;
        zval *cookie_array;
ZEND_END_MODULE_GLOBALS(my_input_filter)

#ifdef ZTS
#define IF_G(v) TSRMG(my_input_filter_globals_id, zend_my_input_filter_globals *, v)
#else
#define IF_G(v) (my_input_filter_globals.v)
#endif

ZEND_DECLARE_MODULE_GLOBALS(my_input_filter)

zend_function_entry my_input_filter_functions[] = {
    PHP_FE(my_get_raw,   NULL)
    {NULL, NULL, NULL}
};

zend_module_entry my_input_filter_module_entry = {
    STANDARD_MODULE_HEADER,
    "my_input_filter",
    my_input_filter_functions,
    PHP_MINIT(my_input_filter),
    PHP_MSHUTDOWN(my_input_filter),
    NULL,
    PHP_RSHUTDOWN(my_input_filter),
    PHP_MINFO(my_input_filter),
    "0.1",
    STANDARD_MODULE_PROPERTIES
};

PHP_MINIT_FUNCTION(my_input_filter)
{
    ZEND_INIT_MODULE_GLOBALS(my_input_filter, php_my_input_filter_init_globals, NULL);

    REGISTER_LONG_CONSTANT("POST", PARSE_POST, CONST_CS | CONST_PERSISTENT);
    REGISTER_LONG_CONSTANT("GET", PARSE_GET, CONST_CS | CONST_PERSISTENT);
    REGISTER_LONG_CONSTANT("COOKIE", PARSE_COOKIE, CONST_CS | CONST_PERSISTENT);

    sapi_register_input_filter(my_sapi_input_filter);
    return SUCCESS;
}

PHP_RSHUTDOWN_FUNCTION(my_input_filter)
{
    if(IF_G(get_array)) {
        zval_ptr_dtor(&IF_G(get_array));
        IF_G(get_array) = NULL;
    }
    if(IF_G(post_array)) {
        zval_ptr_dtor(&IF_G(post_array));
        IF_G(post_array) = NULL;
    }
    if(IF_G(cookie_array)) {
        zval_ptr_dtor(&IF_G(cookie_array));
        IF_G(cookie_array) = NULL;
    }
    return SUCCESS;
}

PHP_MINFO_FUNCTION(my_input_filter)
{
    php_info_print_table_start();
    php_info_print_table_row( 2, "My Input Filter Support", "enabled" );
    php_info_print_table_row( 2, "Revision", "$Id$");
    php_info_print_table_end();
}

/* The filter handler. If you return 1 from it, then PHP also registers the
 * (modified) variable. Returning 0 prevents PHP from registering the variable;
 * you can use this if your filter already registers the variable under a
 * different name, or if you just don't want the variable registered at all. */
SAPI_INPUT_FILTER_FUNC(my_sapi_input_filter)
{
    zval new_var;
    zval *array_ptr = NULL;
    char *raw_var;
    int var_len;

    assert(*val != NULL);

    switch(arg) {
        case PARSE_GET:
            if(!IF_G(get_array)) {
                ALLOC_ZVAL(array_ptr);
                array_init(array_ptr);
                INIT_PZVAL(array_ptr);
            }
            IF_G(get_array) = array_ptr;
            break;
        case PARSE_POST:
            if(!IF_G(post_array)) {
                ALLOC_ZVAL(array_ptr);
                array_init(array_ptr);
                INIT_PZVAL(array_ptr);
            }
            IF_G(post_array) = array_ptr;
            break;
        case PARSE_COOKIE:
            if(!IF_G(cookie_array)) {
                ALLOC_ZVAL(array_ptr);
                array_init(array_ptr);
                INIT_PZVAL(array_ptr);
            }
            IF_G(cookie_array) = array_ptr;
            break;
    }
    Z_STRLEN(new_var) = val_len;
    Z_STRVAL(new_var) = estrndup(*val, val_len);
    Z_TYPE(new_var) = IS_STRING;

    var_len = strlen(var);
    raw_var = emalloc(var_len+5);  /* RAW_ and a \0 */
    strcpy(raw_var, "RAW_");
    strlcat(raw_var,var,var_len+5);

    php_register_variable_ex(raw_var, &new_var, array_ptr TSRMLS_DC);

    php_strip_tags(*val, val_len, NULL, NULL, 0);

    *new_val_len = strlen(*val);
    return 1;
}

PHP_FUNCTION(my_get_raw)
{
    long arg;
    char *var;
    int var_len;
    zval **tmp;
    zval *array_ptr = NULL;

    if(zend_parse_parameters(2 TSRMLS_CC, "ls", &arg, &var, &var_len) == FAILURE) {
        return;
    }

    switch(arg) {
        case PARSE_GET:
            array_ptr = IF_G(get_array);
            break;
        case PARSE_POST:
            array_ptr = IF_G(post_array);
            break;
        case PARSE_COOKIE:
            array_ptr = IF_G(post_array);
            break;
    }

    if(!array_ptr) {
        RETURN_FALSE;
    }

    if(zend_hash_find(HASH_OF(array_ptr), var, var_len+5, (void **)&tmp) == SUCCESS) {
        *return_value = **tmp;
        zval_copy_ctor(return_value);
    } else {
        RETVAL_FALSE;
    }
}