new file mode 100644
--- /dev/null
+++ b/src/http/modules/ngx_http_secure_link_module.c
@@ -0,0 +1,193 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+#include <ngx_md5.h>
+
+
+typedef struct {
+    ngx_str_t  secret;
+} ngx_http_secure_link_conf_t;
+
+
+static void *ngx_http_secure_link_create_conf(ngx_conf_t *cf);
+static char *ngx_http_secure_link_merge_conf(ngx_conf_t *cf, void *parent,
+    void *child);
+static ngx_int_t ngx_http_secure_link_add_variables(ngx_conf_t *cf);
+
+
+static ngx_command_t  ngx_http_secure_link_commands[] = {
+
+    { ngx_string("secure_link_secret"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_str_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_secure_link_conf_t, secret),
+      NULL },
+
+      ngx_null_command
+};
+
+
+static ngx_http_module_t  ngx_http_secure_link_module_ctx = {
+    ngx_http_secure_link_add_variables,    /* preconfiguration */
+    NULL,                                  /* postconfiguration */
+
+    NULL,                                  /* create main configuration */
+    NULL,                                  /* init main configuration */
+
+    NULL,                                  /* create server configuration */
+    NULL,                                  /* merge server configuration */
+
+    ngx_http_secure_link_create_conf,      /* create location configuration */
+    ngx_http_secure_link_merge_conf        /* merge location configuration */
+};
+
+
+ngx_module_t  ngx_http_secure_link_module = {
+    NGX_MODULE_V1,
+    &ngx_http_secure_link_module_ctx,      /* module context */
+    ngx_http_secure_link_commands,         /* module directives */
+    NGX_HTTP_MODULE,                       /* module type */
+    NULL,                                  /* init master */
+    NULL,                                  /* init module */
+    NULL,                                  /* init process */
+    NULL,                                  /* init thread */
+    NULL,                                  /* exit thread */
+    NULL,                                  /* exit process */
+    NULL,                                  /* exit master */
+    NGX_MODULE_V1_PADDING
+};
+
+
+static ngx_str_t  ngx_http_secure_link = ngx_string("secure_link");
+
+
+static ngx_int_t
+ngx_http_secure_link_variable(ngx_http_request_t *r,
+     ngx_http_variable_value_t *v, uintptr_t data)
+{
+    u_char                        *p, *start, *end, *last;
+    size_t                         len;
+    ngx_int_t                      n;
+    ngx_uint_t                     i;
+    ngx_md5_t                      md5;
+    ngx_http_secure_link_conf_t  *conf;
+    u_char                         hash[16];
+
+    conf = ngx_http_get_module_loc_conf(r, ngx_http_secure_link_module);
+
+    if (conf->secret.len == 0) {
+        goto not_found;
+    }
+
+    p = &r->unparsed_uri.data[1];
+    last = r->unparsed_uri.data + r->unparsed_uri.len;
+
+    while (p < last) {
+        if (*p++ == '/') {
+            start = p;
+            goto md5_start;
+        }
+    }
+
+    goto not_found;
+
+md5_start:
+
+    while (p < last) {
+        if (*p++ == '/') {
+            end = p - 1;
+            goto url_start;
+        }
+    }
+
+    goto not_found;
+
+url_start:
+
+    len = last - p;
+
+    if (end - start != 32 || len < 3) {
+        goto not_found;
+    }
+
+    ngx_md5_init(&md5);
+    ngx_md5_update(&md5, p, len);
+    ngx_md5_update(&md5, conf->secret.data, conf->secret.len);
+    ngx_md5_final(hash, &md5);
+
+    for (i = 0; i < 16; i++) {
+        n = ngx_hextoi(&start[2 * i], 2);
+        if (n == NGX_ERROR || n != hash[i]) {
+            goto not_found;
+        }
+    }
+
+    v->len = len;
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+    v->data = p;
+
+    return NGX_OK;
+
+not_found:
+
+    v->not_found = 1;
+
+    return NGX_OK;
+}
+
+
+static void *
+ngx_http_secure_link_create_conf(ngx_conf_t *cf)
+{
+    ngx_http_secure_link_conf_t  *conf;
+
+    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_secure_link_conf_t));
+    if (conf == NULL) {
+        return NGX_CONF_ERROR;
+    }
+
+    /*
+     * set by ngx_pcalloc():
+     *
+     *     conf->secret = { 0, NULL }
+     */
+
+    return conf;
+}
+
+
+static char *
+ngx_http_secure_link_merge_conf(ngx_conf_t *cf, void *parent, void *child)
+{
+    ngx_http_secure_link_conf_t *prev = parent;
+    ngx_http_secure_link_conf_t *conf = child;
+
+    ngx_conf_merge_str_value(conf->secret, prev->secret, "");
+
+    return NGX_CONF_OK;
+}
+
+
+static ngx_int_t
+ngx_http_secure_link_add_variables(ngx_conf_t *cf)
+{
+    ngx_http_variable_t  *var;
+
+    var = ngx_http_add_variable(cf, &ngx_http_secure_link, NGX_HTTP_VAR_NOHASH);
+    if (var == NULL) {
+        return NGX_ERROR;
+    }
+
+    var->get_handler = ngx_http_secure_link_variable;
+
+    return NGX_OK;
+}