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/* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ /** * @file ap_expr.h * @brief Expression parser * * @defgroup AP_EXPR Expression parser * @ingroup APACHE_CORE * @{ */ #ifndef AP_EXPR_H #define AP_EXPR_H #include "httpd.h" #include "http_config.h" #include "ap_regex.h" #ifdef __cplusplus extern "C" { #endif /** A node in the expression parse tree */ typedef struct ap_expr_node ap_expr_t; /** Struct describing a parsed expression */ typedef struct { /** The root of the actual expression parse tree */ ap_expr_t *root_node; /** The filename where the expression has been defined (for logging). * May be NULL */ const char *filename; /** The line number where the expression has been defined (for logging). */ unsigned int line_number; /** Flags relevant for the expression, see AP_EXPR_FLAG_* */ unsigned int flags; /** The module that is used for loglevel configuration */ int module_index; } ap_expr_info_t; /** Use ssl_expr compatibility mode (changes the meaning of the comparison * operators) */ #define AP_EXPR_FLAG_SSL_EXPR_COMPAT 1 /** Don't add significant request headers to the Vary response header */ #define AP_EXPR_FLAG_DONT_VARY 2 /** Don't allow functions/vars that bypass the current request's access * restrictions or would otherwise leak confidential information. * Used by e.g. mod_include. */ #define AP_EXPR_FLAG_RESTRICTED 4 /** Expression evaluates to a string, not to a bool */ #define AP_EXPR_FLAG_STRING_RESULT 8 /** * Evaluate a parse tree, simple interface * @param r The current request * @param expr The expression to be evaluated * @param err Where an error message should be stored * @return > 0 if expression evaluates to true, == 0 if false, < 0 on error * @note err will be set to NULL on success, or to an error message on error * @note request headers used during evaluation will be added to the Vary: * response header, unless ::AP_EXPR_FLAG_DONT_VARY is set. */ AP_DECLARE(int) ap_expr_exec(request_rec *r, const ap_expr_info_t *expr, const char **err); /** * Evaluate a parse tree, with access to regexp backreference * @param r The current request * @param expr The expression to be evaluated * @param nmatch size of the regex match vector pmatch * @param pmatch information about regex matches * @param source the string that pmatch applies to * @param err Where an error message should be stored * @return > 0 if expression evaluates to true, == 0 if false, < 0 on error * @note err will be set to NULL on success, or to an error message on error * @note nmatch/pmatch/source can be used both to make previous matches * available to ap_expr_exec_re and to use ap_expr_exec_re's matches * later on. * @note request headers used during evaluation will be added to the Vary: * response header, unless ::AP_EXPR_FLAG_DONT_VARY is set. */ AP_DECLARE(int) ap_expr_exec_re(request_rec *r, const ap_expr_info_t *expr, apr_size_t nmatch, ap_regmatch_t *pmatch, const char **source, const char **err); /** Context used during evaluation of a parse tree, created by ap_expr_exec */ typedef struct { /** the current request */ request_rec *r; /** the current connection */ conn_rec *c; /** the current virtual host */ server_rec *s; /** the pool to use */ apr_pool_t *p; /** where to store the error string */ const char **err; /** ap_expr_info_t for the expression */ const ap_expr_info_t *info; /** regex match information for back references */ ap_regmatch_t *re_pmatch; /** size of the vector pointed to by re_pmatch */ apr_size_t re_nmatch; /** the string corresponding to the re_pmatch */ const char **re_source; /** A string where the comma separated names of headers are stored * to be later added to the Vary: header. If NULL, the caller is not * interested in this information. */ const char **vary_this; /** where to store the result string */ const char **result_string; /** Arbitrary context data provided by the caller for custom functions */ void *data; /** The current recursion level */ int reclvl; } ap_expr_eval_ctx_t; /** * Evaluate a parse tree, full featured version * @param ctx The evaluation context with all data filled in * @return > 0 if expression evaluates to true, == 0 if false, < 0 on error * @note *ctx->err will be set to NULL on success, or to an error message on * error * @note request headers used during evaluation will be added to the Vary: * response header if ctx->vary_this is set. */ AP_DECLARE(int) ap_expr_exec_ctx(ap_expr_eval_ctx_t *ctx); /** * Evaluate a parse tree of a string valued expression * @param r The current request * @param expr The expression to be evaluated * @param err Where an error message should be stored * @return The result string, NULL on error * @note err will be set to NULL on success, or to an error message on error * @note request headers used during evaluation will be added to the Vary: * response header, unless ::AP_EXPR_FLAG_DONT_VARY is set. */ AP_DECLARE(const char *) ap_expr_str_exec(request_rec *r, const ap_expr_info_t *expr, const char **err); /** * Evaluate a parse tree of a string valued expression * @param r The current request * @param expr The expression to be evaluated * @param nmatch size of the regex match vector pmatch * @param pmatch information about regex matches * @param source the string that pmatch applies to * @param err Where an error message should be stored * @return The result string, NULL on error * @note err will be set to NULL on success, or to an error message on error * @note nmatch/pmatch/source can be used both to make previous matches * available to ap_expr_exec_re and to use ap_expr_exec_re's matches * later on. * @note request headers used during evaluation will be added to the Vary: * response header, unless ::AP_EXPR_FLAG_DONT_VARY is set. */ AP_DECLARE(const char *) ap_expr_str_exec_re(request_rec *r, const ap_expr_info_t *expr, apr_size_t nmatch, ap_regmatch_t *pmatch, const char **source, const char **err); /** * The parser can be extended with variable lookup, functions, and * and operators. * * During parsing, the parser calls the lookup function to resolve a * name into a function pointer and an opaque context for the function. * If the argument to a function or operator is constant, the lookup function * may also parse that argument and store the parsed data in the context. * * The default lookup function is the hook ::ap_expr_lookup_default which just * calls ap_run_expr_lookup. Modules can use it to make functions and * variables generally available. * * An ap_expr consumer can also provide its own custom lookup function to * modify the set of variables and functions that are available. The custom * lookup function can in turn call 'ap_run_expr_lookup'. */ /** Unary operator, takes one string argument and returns a bool value. * The name must have the form '-z' (one letter only). * @param ctx The evaluation context * @param data An opaque context provided by the lookup hook function * @param arg The (right) operand * @return 0 or 1 */ typedef int ap_expr_op_unary_t(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg); /** Binary operator, takes two string arguments and returns a bool value. * The name must have the form '-cmp' (at least two letters). * @param ctx The evaluation context * @param data An opaque context provided by the lookup hook function * @param arg1 The left operand * @param arg2 The right operand * @return 0 or 1 */ typedef int ap_expr_op_binary_t(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg1, const char *arg2); /** String valued function, takes a string argument and returns a string * @param ctx The evaluation context * @param data An opaque context provided by the lookup hook function * @param arg The argument * @return The functions result string, may be NULL for 'empty string' */ typedef const char *(ap_expr_string_func_t)(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg); /** List valued function, takes a string argument and returns a list of strings * Can currently only be called following the builtin '-in' operator. * @param ctx The evaluation context * @param data An opaque context provided by the lookup hook function * @param arg The argument * @return The functions result list of strings, may be NULL for 'empty array' */ typedef apr_array_header_t *(ap_expr_list_func_t)(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg); /** Variable lookup function, takes no argument and returns a string * @param ctx The evaluation context * @param data An opaque context provided by the lookup hook function * @return The expanded variable */ typedef const char *(ap_expr_var_func_t)(ap_expr_eval_ctx_t *ctx, const void *data); /** parameter struct passed to the lookup hook functions */ typedef struct { /** type of the looked up object */ int type; #define AP_EXPR_FUNC_VAR 0 #define AP_EXPR_FUNC_STRING 1 #define AP_EXPR_FUNC_LIST 2 #define AP_EXPR_FUNC_OP_UNARY 3 #define AP_EXPR_FUNC_OP_BINARY 4 /** name of the looked up object */ const char *name; int flags; apr_pool_t *pool; apr_pool_t *ptemp; /** where to store the function pointer */ const void **func; /** where to store the function's context */ const void **data; /** where to store the error message (if any) */ const char **err; /** arg for pre-parsing (only if a simple string). * For binary ops, this is the right argument. */ const char *arg; } ap_expr_lookup_parms; /** Function for looking up the provider function for a variable, operator * or function in an expression. * @param parms The parameter struct, also determines where the result is * stored. * @return OK on success, * !OK on failure, * DECLINED if the requested name is not handled by this function */ typedef int (ap_expr_lookup_fn_t)(ap_expr_lookup_parms *parms); /** Default lookup function which just calls ap_run_expr_lookup(). * ap_run_expr_lookup cannot be used directly because it has the wrong * calling convention under Windows. */ AP_DECLARE_NONSTD(int) ap_expr_lookup_default(ap_expr_lookup_parms *parms); AP_DECLARE_HOOK(int, expr_lookup, (ap_expr_lookup_parms *parms)) /** * Parse an expression into a parse tree * @param pool Pool * @param ptemp temp pool * @param info The ap_expr_info_t struct (with values filled in) * @param expr The expression string to parse * @param lookup_fn The lookup function to use, NULL for default * @return NULL on success, error message on error. * A pointer to the resulting parse tree will be stored in * info->root_node. */ AP_DECLARE(const char *) ap_expr_parse(apr_pool_t *pool, apr_pool_t *ptemp, ap_expr_info_t *info, const char *expr, ap_expr_lookup_fn_t *lookup_fn); /** * High level interface to ap_expr_parse that also creates ap_expr_info_t and * uses info from cmd_parms to fill in most of it. * @param cmd The cmd_parms struct * @param expr The expression string to parse * @param flags The flags to use, see AP_EXPR_FLAG_* * @param err Set to NULL on success, error message on error * @param lookup_fn The lookup function used to lookup vars, functions, and * operators * @param module_index The module_index to set for the expression * @return The parsed expression * @note Usually ap_expr_parse_cmd() should be used */ AP_DECLARE(ap_expr_info_t *) ap_expr_parse_cmd_mi(const cmd_parms *cmd, const char *expr, unsigned int flags, const char **err, ap_expr_lookup_fn_t *lookup_fn, int module_index); /** * Convenience wrapper for ap_expr_parse_cmd_mi() that sets * module_index = APLOG_MODULE_INDEX */ #define ap_expr_parse_cmd(cmd, expr, flags, err, lookup_fn) \ ap_expr_parse_cmd_mi(cmd, expr, flags, err, lookup_fn, APLOG_MODULE_INDEX) /** * Internal initialisation of ap_expr (for httpd internal use) */ void ap_expr_init(apr_pool_t *pool); #ifdef __cplusplus } #endif #endif /* AP_EXPR_H */ /** @} */