An IV should be generated for each encryption

We now have the ability to decide if the IV is communicated to the client in a non forgeable manner or we only keep it on the server side.

Closes openresty#2

Author: rcosnita

src/ngx_http_encrypted_session_module.c

@@ -10,6 +10,7 @@
 #include "ddebug.h"
 
 #include <ndk.h>
+#include <string.h>
 #include "ngx_http_encrypted_session_cipher.h"
 
 #define ngx_http_encrypted_session_default_iv (u_char *) "deadbeefdeadbeef"
@@ -19,9 +20,11 @@
 
 typedef struct {
     u_char              *key;
+    size_t              key_len;
     u_char              *iv;
+    size_t              iv_len;
     time_t               expires;
-
+    ngx_flag_t          iv_in_content;
 } ngx_http_encrypted_session_conf_t;
 
 
@@ -42,6 +45,8 @@ static char *ngx_http_encrypted_session_iv(ngx_conf_t *cf, ngx_command_t *cmd,
 static char *ngx_http_encrypted_session_expires(ngx_conf_t *cf,
     ngx_command_t *cmd, void *conf);
 
+static char *ngx_http_encrypted_iv_in_content(ngx_conf_t *cf,
+    ngx_command_t *cmd, void *conf);
 
 static ngx_int_t ngx_http_encrypted_session_init(ngx_conf_t *cf);
 static void *ngx_http_encrypted_session_create_main_conf(ngx_conf_t *cf);
@@ -53,7 +58,6 @@ static void *ngx_http_encrypted_session_create_conf(ngx_conf_t *cf);
 static char *ngx_http_encrypted_session_merge_conf(ngx_conf_t *cf, void *parent,
     void *child);
 
-
 static  ndk_set_var_t  ngx_http_set_encode_encrypted_session_filter = {
     NDK_SET_VAR_VALUE,
     (void *) ngx_http_set_encode_encrypted_session,
@@ -115,7 +119,14 @@ static ngx_command_t  ngx_http_encrypted_session_commands[] = {
         0,
         &ngx_http_set_decode_encrypted_session_filter
     },
-
+    { ngx_string("include_iv_in_encrypted_payload"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_SIF_CONF
+      |NGX_HTTP_LOC_CONF|NGX_HTTP_LIF_CONF|NGX_CONF_NOARGS,
+      ngx_http_encrypted_iv_in_content,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      0,
+      NULL
+    },
     ngx_null_command
 };
 
@@ -151,14 +162,14 @@ ngx_module_t  ngx_http_encrypted_session_module = {
 };
 
 static ngx_str_t ngx_http_get_variable_by_name(ngx_http_request_t *r,
-    unsigned char *name, ngx_http_encrypted_session_conf_t *conf)
+    unsigned char *name, size_t name_len, ngx_http_encrypted_session_conf_t *conf)
 {
     ngx_http_variable_value_t  *v;
     ngx_str_t name_str;
     name_str.data = name;
-    name_str.len = strlen((const char *)name);
+    name_str.len = name_len;
 
-    ngx_uint_t key = ngx_hash_strlow(name, name, name_str.len);
+    ngx_uint_t key = ngx_hash_strlow(name, name, name_len);
     v = ngx_http_get_variable(r, &name_str, key);
 
     if (v->not_found) {
@@ -171,6 +182,19 @@ static ngx_str_t ngx_http_get_variable_by_name(ngx_http_request_t *r,
     return var_value;
 }
 
+static char*
+ngx_http_encrypted_session_build_payload(ngx_http_request_t *r,
+   char *input, size_t input_len, ngx_str_t *iv)
+{
+    size_t new_len = input_len + iv->len + 2;
+    char *data = (char *)ngx_pcalloc(r->pool, new_len);
+    data = strncat(data, input, input_len);
+    data = strcat(data, ":");
+    data = strncat(data, (char *)iv->data, iv->len);
+
+    return data;
+}
+
 static ngx_int_t
 ngx_http_set_encode_encrypted_session(ngx_http_request_t *r,
     ngx_str_t *res, ngx_http_variable_value_t *v)
@@ -196,12 +220,19 @@ ngx_http_set_encode_encrypted_session(ngx_http_request_t *r,
     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                    "encrypted_session: expires=%T", conf->expires);
 
-    ngx_str_t iv = ngx_http_get_variable_by_name(r, conf->iv, conf);
-    ngx_str_t key = ngx_http_get_variable_by_name(r, conf->key, conf);
+    ngx_str_t iv = ngx_http_get_variable_by_name(r, conf->iv, conf->iv_len,
+                                                 conf);
+    ngx_str_t key = ngx_http_get_variable_by_name(r, conf->key, conf->key_len,
+                                                  conf);
+
+    char *data = (char *)v->data;
+    if (conf->iv_in_content) {
+        data = ngx_http_encrypted_session_build_payload(r, data, v->len, &iv);
+    }
 
     rc = ngx_http_encrypted_session_aes_mac_encrypt(emcf, r->pool,
             r->connection->log, iv.data, iv.len, key.data, key.len,
-            v->data, v->len, (ngx_uint_t) conf->expires, &dst, &len);
+            (u_char*)data, v->len, (ngx_uint_t) conf->expires, &dst, &len);
 
     if (rc != NGX_OK) {
         dst = NULL;
@@ -211,6 +242,16 @@ ngx_http_set_encode_encrypted_session(ngx_http_request_t *r,
                       "encrypted_session: failed to encrypt");
     }
 
+    if (conf->iv_in_content) {
+        size_t new_len = iv.len + len + 1;
+        char *new_content = (char*)ngx_pcalloc(r->pool, new_len);
+        new_content = strncat(new_content, (char*)iv.data, iv.len);
+        new_content = strcat(new_content, ":");
+        new_content = strncat(new_content, (char*)dst, len);
+        len = new_len;
+        dst = (u_char*)new_content;
+    }
+
     res->data = dst;
     res->len = len;
 
@@ -240,12 +281,29 @@ ngx_http_set_decode_encrypted_session(ngx_http_request_t *r,
         return NGX_ERROR;
     }
 
-    ngx_str_t iv = ngx_http_get_variable_by_name(r, conf->iv, conf);
-    ngx_str_t key = ngx_http_get_variable_by_name(r, conf->key, conf);
+    ngx_str_t iv;
+    char *data = (char*)v->data;
+    size_t data_len = v->len;
+
+    if (!conf->iv_in_content) {
+        iv = ngx_http_get_variable_by_name(r, conf->iv, conf->iv_len, conf);
+    } else {
+        iv.len = strcspn(data, ":");
+        iv.data = (u_char*)ngx_pcalloc(r->pool, iv.len + 1);
+
+        strncpy((char*)iv.data, (char*)v->data, iv.len);
+
+        data_len = v->len - iv.len - 1;
+        data = (char*)ngx_pcalloc(r->pool, data_len);
+        strncpy(data, (char*)(&v->data[iv.len + 1]), data_len);
+    }
+
+    ngx_str_t key = ngx_http_get_variable_by_name(r, conf->key, conf->key_len,
+                                                  conf);
 
     rc = ngx_http_encrypted_session_aes_mac_decrypt(emcf, r->pool,
             r->connection->log, iv.data, iv.len, key.data, key.len,
-            v->data, v->len, &dst, &len);
+            (u_char*)data, data_len, &dst, &len);
 
     if (rc != NGX_OK) {
         dst = NULL;
@@ -273,7 +331,9 @@ ngx_http_encrypted_session_key(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
     value = cf->args->elts;
 
     if (value[1].len > 1 && value[1].data[0] == '$') {
-      llcf->key = &(value[1].data[1]);
+      llcf->key_len = value[1].len - 1;
+      llcf->key = (u_char*)ngx_pcalloc(cf->pool, llcf->key_len);
+      strncpy((char*)llcf->key, (char*)&(value[1].data[1]), llcf->key_len);
       return NGX_CONF_OK;
     }
 
@@ -287,6 +347,7 @@ ngx_http_encrypted_session_key(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
     }
 
     llcf->key = value[1].data;
+    llcf->key_len = value[1].len;
 
     return NGX_CONF_OK;
 }
@@ -307,6 +368,7 @@ ngx_http_encrypted_session_iv(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
 
     if (value[1].len > 1 && value[1].data[0] == '$') {
       llcf->iv = &(value[1].data[1]);
+      llcf->iv_len = value[1].len - 1;
       return NGX_CONF_OK;
     }
 
@@ -320,6 +382,7 @@ ngx_http_encrypted_session_iv(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
     }
 
     llcf->iv = ngx_pcalloc(cf->pool, ngx_http_encrypted_session_iv_length);
+    llcf->iv_len = ngx_http_encrypted_session_iv_length;
 
     if (llcf->iv == NULL) {
         return NGX_CONF_ERROR;
@@ -360,6 +423,13 @@ ngx_http_encrypted_session_expires(ngx_conf_t *cf, ngx_command_t *cmd,
     return NGX_CONF_OK;
 }
 
+static char *ngx_http_encrypted_iv_in_content(ngx_conf_t *cf,
+   ngx_command_t *cmd, void *conf)
+{
+   ngx_http_encrypted_session_conf_t  *llcf = conf;
+   llcf->iv_in_content = 1;
+   return NGX_CONF_OK;
+}
 
 static void
 ngx_http_encrypted_session_free_cipher_ctx(void *data)
@@ -435,8 +505,11 @@ ngx_http_encrypted_session_create_conf(ngx_conf_t *cf)
     }
 
     conf->key     = NGX_CONF_UNSET_PTR;
+    conf->key_len = NGX_CONF_UNSET;
     conf->iv      = NGX_CONF_UNSET_PTR;
+    conf->iv_len  = NGX_CONF_UNSET;
     conf->expires = NGX_CONF_UNSET;
+    conf->iv_in_content = NGX_CONF_UNSET;
 
     return conf;
 }
@@ -449,12 +522,17 @@ ngx_http_encrypted_session_merge_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_http_encrypted_session_conf_t *conf = child;
 
     ngx_conf_merge_ptr_value(conf->key, prev->key, NULL);
+    ngx_conf_merge_size_value(conf->key_len, prev->key_len,
+                              (size_t)ngx_http_encrypted_session_key_length);
 
     ngx_conf_merge_ptr_value(conf->iv, prev->iv,
                              ngx_http_encrypted_session_default_iv);
+    ngx_conf_merge_size_value(conf->iv_len, prev->iv_len,
+                              (size_t)ngx_http_encrypted_session_iv_length);
 
     ngx_conf_merge_value(conf->expires, prev->expires,
                          ngx_http_encrypted_session_default_expires);
+    ngx_conf_merge_value(conf->iv_in_content, prev->iv_in_content, 0);
 
     return NGX_CONF_OK;
 }