view src/http/ngx_http_variables.h @ 8164:b71e69247483

Variables: avoid possible buffer overrun with some "$sent_http_*". The existing logic to evaluate multi header "$sent_http_*" variables, such as $sent_http_cache_control, as previously introduced in 1.23.0, doesn't take into account that one or more elements can be cleared, yet still present in a linked list, pointed to by the next field. Such elements don't contribute to the resulting variable length, an attempt to append a separator for them ends up in out of bounds write. This is not possible with standard modules, though at least one third party module is known to override multi header values this way, so it makes sense to harden the logic. The fix restores a generic boundary check.
author Sergey Kandaurov <pluknet@nginx.com>
date Mon, 01 May 2023 19:16:05 +0400
parents 08b3ea81ff5f
children
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_HTTP_VARIABLES_H_INCLUDED_
#define _NGX_HTTP_VARIABLES_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


typedef ngx_variable_value_t  ngx_http_variable_value_t;

#define ngx_http_variable(v)     { sizeof(v) - 1, 1, 0, 0, 0, (u_char *) v }

typedef struct ngx_http_variable_s  ngx_http_variable_t;

typedef void (*ngx_http_set_variable_pt) (ngx_http_request_t *r,
    ngx_http_variable_value_t *v, uintptr_t data);
typedef ngx_int_t (*ngx_http_get_variable_pt) (ngx_http_request_t *r,
    ngx_http_variable_value_t *v, uintptr_t data);


#define NGX_HTTP_VAR_CHANGEABLE   1
#define NGX_HTTP_VAR_NOCACHEABLE  2
#define NGX_HTTP_VAR_INDEXED      4
#define NGX_HTTP_VAR_NOHASH       8
#define NGX_HTTP_VAR_WEAK         16
#define NGX_HTTP_VAR_PREFIX       32


struct ngx_http_variable_s {
    ngx_str_t                     name;   /* must be first to build the hash */
    ngx_http_set_variable_pt      set_handler;
    ngx_http_get_variable_pt      get_handler;
    uintptr_t                     data;
    ngx_uint_t                    flags;
    ngx_uint_t                    index;
};

#define ngx_http_null_variable  { ngx_null_string, NULL, NULL, 0, 0, 0 }


ngx_http_variable_t *ngx_http_add_variable(ngx_conf_t *cf, ngx_str_t *name,
    ngx_uint_t flags);
ngx_int_t ngx_http_get_variable_index(ngx_conf_t *cf, ngx_str_t *name);
ngx_http_variable_value_t *ngx_http_get_indexed_variable(ngx_http_request_t *r,
    ngx_uint_t index);
ngx_http_variable_value_t *ngx_http_get_flushed_variable(ngx_http_request_t *r,
    ngx_uint_t index);

ngx_http_variable_value_t *ngx_http_get_variable(ngx_http_request_t *r,
    ngx_str_t *name, ngx_uint_t key);

ngx_int_t ngx_http_variable_unknown_header(ngx_http_request_t *r,
    ngx_http_variable_value_t *v, ngx_str_t *var, ngx_list_part_t *part,
    size_t prefix);


#if (NGX_PCRE)

typedef struct {
    ngx_uint_t                    capture;
    ngx_int_t                     index;
} ngx_http_regex_variable_t;


typedef struct {
    ngx_regex_t                  *regex;
    ngx_uint_t                    ncaptures;
    ngx_http_regex_variable_t    *variables;
    ngx_uint_t                    nvariables;
    ngx_str_t                     name;
} ngx_http_regex_t;


typedef struct {
    ngx_http_regex_t             *regex;
    void                         *value;
} ngx_http_map_regex_t;


ngx_http_regex_t *ngx_http_regex_compile(ngx_conf_t *cf,
    ngx_regex_compile_t *rc);
ngx_int_t ngx_http_regex_exec(ngx_http_request_t *r, ngx_http_regex_t *re,
    ngx_str_t *s);

#endif


typedef struct {
    ngx_hash_combined_t           hash;
#if (NGX_PCRE)
    ngx_http_map_regex_t         *regex;
    ngx_uint_t                    nregex;
#endif
} ngx_http_map_t;


void *ngx_http_map_find(ngx_http_request_t *r, ngx_http_map_t *map,
    ngx_str_t *match);


ngx_int_t ngx_http_variables_add_core_vars(ngx_conf_t *cf);
ngx_int_t ngx_http_variables_init_vars(ngx_conf_t *cf);


extern ngx_http_variable_value_t  ngx_http_variable_null_value;
extern ngx_http_variable_value_t  ngx_http_variable_true_value;


#endif /* _NGX_HTTP_VARIABLES_H_INCLUDED_ */