From 165dc73d4d71c5d68beb5e904d91b280f08fccb6 Mon Sep 17 00:00:00 2001 From: Nick Kew Date: Thu, 27 Aug 2009 01:02:42 +0000 Subject: [PATCH] mod_headers: generalise the envclause to support conditional header rules via ap_expr. git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@808240 13f79535-47bb-0310-9956-ffa450edef68 --- CHANGES | 3 ++ docs/manual/mod/mod_headers.xml | 54 +++++++++++++++++++++------------ modules/metadata/mod_headers.c | 29 +++++++++++++++--- 3 files changed, 63 insertions(+), 23 deletions(-) diff --git a/CHANGES b/CHANGES index 2f07200672..eb887ad3f0 100644 --- a/CHANGES +++ b/CHANGES @@ -2,6 +2,9 @@ Changes with Apache 2.3.3 + *) mod_headers: generalise the envclause to support expression + evaluation with ap_expr parser [Nick Kew] + *) mod_cache: Introduce the thundering herd lock, a mechanism to keep the flood of requests at bay that strike a backend webserver as a cached entity goes stale. [Graham Leggett] diff --git a/docs/manual/mod/mod_headers.xml b/docs/manual/mod/mod_headers.xml index 91674c9d36..8fd54a4bda 100644 --- a/docs/manual/mod/mod_headers.xml +++ b/docs/manual/mod/mod_headers.xml @@ -181,6 +181,12 @@ headers Cache-Control: no-cache, no-cache, no-store +
  • + Set a test cookie if and only if the client didn't send us a cookie + + Header set Set-Cookie testcookie !$req{Cookie} + +
    • @@ -258,15 +264,20 @@ headers replacement string respectively.

    The RequestHeader directive may be followed by - an additional argument, which may be used to specify conditions under - which the action will be taken, or may be the keyword early - to specify early processing. If the - environment - variable specified in the env=... argument - exists (or if the environment variable does not exist and - env=!... is specified) then the action specified - by the RequestHeader directive will take effect. - Otherwise, the directive will have no effect on the request.

    + an additional argument, which may be any of:

    +
    +
    early
    +
    Specifies early processing.
    +
    env=[!]varname
    +
    The directive is applied if and only if the environment variable varname exists. + A ! in front of varname reverses the test, + so the directive applies only if varname is unset.
    +
    expr
    +
    An string that matches neither of the above is parsed as an + expression. Details of expression syntax and evaluation are + currently best documented on the mod_filter page.
    +

    Except in early mode, the RequestHeader directive is processed @@ -404,16 +415,21 @@ headers which is a regular expression, and an additional replacement string.

    -

    The Header directive may be followed by an - an additional argument, which may be used to specify conditions under - which the action will be taken, or may be the keyword early - to specify early processing. If the - environment variable specified in the - env=... argument exists (or if the environment - variable does not exist and env=!... is specified) - then the action specified by the Header directive - will take effect. Otherwise, the directive will have no effect - on the request.

    +

    The Header directive may be followed by + an additional argument, which may be any of:

    +
    +
    early
    +
    Specifies early processing.
    +
    env=[!]varname
    +
    The directive is applied if and only if the environment variable varname exists. + A ! in front of varname reverses the test, + so the directive applies only if varname is unset.
    +
    expr
    +
    An string that matches neither of the above is parsed as an + expression. Details of expression syntax and evaluation are + currently best documented on the mod_filter page.
    +

    Except in early mode, the Header directives are processed just diff --git a/modules/metadata/mod_headers.c b/modules/metadata/mod_headers.c index b65fbfd077..c9c73c7db9 100644 --- a/modules/metadata/mod_headers.c +++ b/modules/metadata/mod_headers.c @@ -81,6 +81,7 @@ #include "http_log.h" #include "util_filter.h" #include "http_protocol.h" +#include "ap_expr.h" #include "mod_ssl.h" /* for the ssl_var_lookup optional function defn */ @@ -125,6 +126,7 @@ typedef struct { ap_regex_t *regex; const char *condition_var; const char *subs; + ap_parse_node_t *expr; } header_entry; /* echo_do is used for Header echo to iterate through the request headers*/ @@ -391,6 +393,7 @@ static APR_INLINE const char *header_inout_cmd(cmd_parms *cmd, const char *condition_var = NULL; const char *colon; header_entry *new; + ap_parse_node_t *expr = NULL; apr_array_header_t *fixup = (cmd->info == &hdr_in) ? dirconf->fixup_in : (cmd->info == &hdr_err) @@ -472,10 +475,7 @@ static APR_INLINE const char *header_inout_cmd(cmd_parms *cmd, if (strcasecmp(envclause, "early") == 0) { condition_var = condition_early; } - else { - if (strncasecmp(envclause, "env=", 4) != 0) { - return "error: envclause should be in the form env=envar"; - } + else if (strncasecmp(envclause, "env=", 4) == 0) { if ((envclause[4] == '\0') || ((envclause[4] == '!') && (envclause[5] == '\0'))) { return "error: missing environment variable name. " @@ -483,6 +483,13 @@ static APR_INLINE const char *header_inout_cmd(cmd_parms *cmd, } condition_var = envclause + 4; } + else { + int err = 0; + expr = ap_expr_parse(cmd->pool, envclause, &err); + if (err) { + return "Can't parse envclause/expression"; + } + } } if ((colon = ap_strchr_c(hdr, ':'))) { @@ -491,6 +498,7 @@ static APR_INLINE const char *header_inout_cmd(cmd_parms *cmd, new->header = hdr; new->condition_var = condition_var; + new->expr = expr; return parse_format_string(cmd->pool, new, value); } @@ -620,6 +628,19 @@ static void do_headers_fixup(request_rec *r, apr_table_t *headers, else if (early && (envar != condition_early)) { continue; } + /* Do we have an expression to evaluate? */ + else if (hdr->expr != NULL) { + int err = 0; + int eval = ap_expr_eval(r, hdr->expr, &err, NULL, + ap_expr_string, NULL); + if (err) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, + "Failed to evaluate expression - ignoring"); + } + else if (!eval) { + continue; + } + } /* Have any conditional envar-controlled Header processing to do? */ else if (envar && !early) { if (*envar != '!') { -- 2.40.0