[PATCH] Implements the $arg_encode_<name> variables for get url encode value of <name> argument from request string.

[Kirill A. Korinskiy]

Raw value of arguments from request string can help for XSS.
---
 src/http/ngx_http_variables.c |   54 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 54 insertions(+), 0 deletions(-)

diff --git a/src/http/ngx_http_variables.c b/src/http/ngx_http_variables.c
index 22f213cf6157ab5b99e481835acf9a394ef21919..d5a7923343797c268cd70cdd2e87a70887a41419 100644
--- a/src/http/ngx_http_variables.c
+++ b/src/http/ngx_http_variables.c
@@ -31,6 +31,8 @@ static ngx_int_t ngx_http_variable_cookie(ngx_http_request_t *r,
 static ngx_int_t ngx_http_variable_ssi(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);
 #endif
+static ngx_int_t ngx_http_variable_encode_argument(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data);
 static ngx_int_t ngx_http_variable_argument(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);
 
@@ -530,6 +532,15 @@ ngx_http_get_variable(ngx_http_request_t *r, ngx_str_t *name, ngx_uint_t key,
     }
 #endif
 
+    if (ngx_strncmp(name->data, "arg_encode_", 11) == 0) {
+
+        if (ngx_http_variable_encode_argument(r, vv, (uintptr_t) name) == NGX_OK) {
+            return vv;
+        }
+
+        return NULL;
+    }
+
     if (ngx_strncmp(name->data, "arg_", 4) == 0) {
 
         if (ngx_http_variable_argument(r, vv, (uintptr_t) name) == NGX_OK) {
@@ -831,6 +842,42 @@ ngx_http_variable_ssi(ngx_http_request_t *r, ngx_http_variable_value_t *v,
 
 
 static ngx_int_t
+ngx_http_variable_encode_argument(ngx_http_request_t *r, ngx_http_variable_value_t *v,
+    uintptr_t data)
+{
+    ngx_str_t *name = (ngx_str_t *) data;
+
+    u_char     *arg;
+    size_t      len;
+    ngx_str_t   value;
+
+    len = name->len - (sizeof("arg_encode_") - 1);
+    arg = name->data + sizeof("arg_encode_") - 1;
+
+    if (ngx_http_arg(r, arg, len, &value) != NGX_OK) {
+        v->not_found = 1;
+        return NGX_OK;
+    }
+
+    v->len = value.len +
+	2 * ngx_escape_uri(NULL, value.data, value.len, NGX_ESCAPE_ARGS);
+
+    v->data = ngx_palloc(r->pool, v->len);
+    if (v->data == NULL) {
+        v->not_found = 1;
+        return NGX_OK;
+    }
+
+    (void) ngx_escape_uri(v->data, value.data, value.len, NGX_ESCAPE_ARGS);
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
 ngx_http_variable_argument(ngx_http_request_t *r, ngx_http_variable_value_t *v,
     uintptr_t data)
 {
@@ -1789,6 +1836,13 @@ ngx_http_variables_init_vars(ngx_conf_t *cf)
         }
 #endif
 
+        if (ngx_strncmp(v[i].name.data, "arg_encode_", 11) == 0) {
+            v[i].get_handler = ngx_http_variable_encode_argument;
+            v[i].data = (uintptr_t) &v[i].name;
+
+            continue;
+        }
+
         if (ngx_strncmp(v[i].name.data, "arg_", 4) == 0) {
             v[i].get_handler = ngx_http_variable_argument;
             v[i].data = (uintptr_t) &v[i].name;
-- 
1.6.2