[PATCH] Implement generic variables $urlencode_<name> and $urldecode_<name> for get urlencode/urldecode of value of <name> variable.

[Kirill A. Korinskiy]

Raw value of arguments from request string can help for XSS.
---
 src/http/ngx_http_variables.c |  134 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 134 insertions(+), 0 deletions(-)

diff --git a/src/http/ngx_http_variables.c b/src/http/ngx_http_variables.c
index 22f213cf6157ab5b99e481835acf9a394ef21919..035f6cc4687d20646d156d0ed58a303aef76b8d8 100644
--- a/src/http/ngx_http_variables.c
+++ b/src/http/ngx_http_variables.c
@@ -31,6 +31,10 @@ 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_urlencode(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data);
+static ngx_int_t ngx_http_variable_urldecode(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 +534,24 @@ ngx_http_get_variable(ngx_http_request_t *r, ngx_str_t *name, ngx_uint_t key,
     }
 #endif
 
+    if (ngx_strncmp(name->data, "urlencode_", 10) == 0) {
+
+        if (ngx_http_variable_urlencode(r, vv, (uintptr_t) name) == NGX_OK) {
+            return vv;
+        }
+
+        return NULL;
+    }
+
+    if (ngx_strncmp(name->data, "urldecode_", 10) == 0) {
+
+        if (ngx_http_variable_urldecode(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 +853,104 @@ ngx_http_variable_ssi(ngx_http_request_t *r, ngx_http_variable_value_t *v,
 
 
 static ngx_int_t
+ngx_http_variable_urlencode(ngx_http_request_t *r, ngx_http_variable_value_t *v,
+    uintptr_t data)
+{
+    ngx_str_t *name = (ngx_str_t *) data;
+
+    ngx_str_t  sub_name;
+
+    ngx_uint_t key;
+
+    ngx_http_variable_value_t *vv;
+
+    sub_name.len = name->len - (sizeof("urlencode_") - 1);
+    sub_name.data = name->data + sizeof("urlencode_") - 1;
+
+    key = ngx_hash_strlow(sub_name.data, sub_name.data, sub_name.len);
+
+    vv = ngx_http_get_variable(r, &sub_name, key, 0);
+
+    if (vv == NULL || !vv->valid) {
+        return NGX_ERROR;
+    }
+
+    if (vv->not_found) {
+        v->not_found = 1;
+        return NGX_OK;
+    }
+
+    v->len = vv->len +
+	2 * ngx_escape_uri(NULL, vv->data, vv->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, vv->data, vv->len, NGX_ESCAPE_ARGS);
+
+    v->valid = 1;
+    v->not_found = 0;
+    v->no_cacheable = vv->no_cacheable;
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_http_variable_urldecode(ngx_http_request_t *r, ngx_http_variable_value_t *v,
+    uintptr_t data)
+{
+    ngx_str_t *name = (ngx_str_t *) data;
+
+    u_char    *dst, *src;
+    ngx_str_t  sub_name;
+    ngx_uint_t key;
+
+    ngx_http_variable_value_t *vv;
+
+    sub_name.len = name->len - (sizeof("urldecode_") - 1);
+    sub_name.data = name->data + sizeof("urldecode_") - 1;
+
+    key = ngx_hash_strlow(sub_name.data, sub_name.data, sub_name.len);
+
+    vv = ngx_http_get_variable(r, &sub_name, key, 0);
+
+    if (vv == NULL || !vv->valid) {
+        return NGX_ERROR;
+    }
+
+    if (vv->not_found) {
+        v->not_found = 1;
+        return NGX_OK;
+    }
+
+    v->len = vv->len;
+
+    v->data = ngx_palloc(r->pool, v->len);
+    if (v->data == NULL) {
+        v->not_found = 1;
+        return NGX_OK;
+    }
+
+    dst = v->data;
+    src = vv->data;
+
+    ngx_unescape_uri(&dst, &src, vv->len, NGX_ESCAPE_ARGS);
+
+    v->len = dst - v->data;
+
+    v->valid = 1;
+    v->not_found = 0;
+    v->no_cacheable = vv->no_cacheable;
+
+    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 +1909,20 @@ ngx_http_variables_init_vars(ngx_conf_t *cf)
         }
 #endif
 
+        if (ngx_strncmp(v[i].name.data, "urlencode_", 10) == 0) {
+            v[i].get_handler = ngx_http_variable_urlencode;
+            v[i].data = (uintptr_t) &v[i].name;
+
+            continue;
+        }
+
+        if (ngx_strncmp(v[i].name.data, "urldecode_", 10) == 0) {
+            v[i].get_handler = ngx_http_variable_urldecode;
+            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