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changeset 6854:75e7d55214bd

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SSL: support AES256 encryption of tickets. This implies ticket key size of 80 bytes instead of previously used 48, as both HMAC and AES keys are 32 bytes now. When an old 48-byte ticket key is provided, we fall back to using backward-compatible AES128 encryption. OpenSSL switched to using AES256 in 1.1.0, and we are providing equivalent security. While here, order of HMAC and AES keys was reverted to make the implementation compatible with keys used by OpenSSL with SSL_CTX_set_tlsext_ticket_keys(). Prodded by Christian Klinger.
author Maxim Dounin <mdounin@mdounin.ru>
date Fri, 23 Dec 2016 17:28:20 +0300
parents c85dfd99a2dd
children c2c13f1f47fd
files src/event/ngx_event_openssl.c src/event/ngx_event_openssl.h
diffstat 2 files changed, 47 insertions(+), 16 deletions(-) [+]
line wrap: on
line diff
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -2856,7 +2856,8 @@ ngx_ssl_session_rbtree_insert_value(ngx_
 ngx_int_t
 ngx_ssl_session_ticket_keys(ngx_conf_t *cf, ngx_ssl_t *ssl, ngx_array_t *paths)
 {
-    u_char                         buf[48];
+    u_char                         buf[80];
+    size_t                         size;
     ssize_t                        n;
     ngx_str_t                     *path;
     ngx_file_t                     file;
@@ -2899,13 +2900,15 @@ ngx_ssl_session_ticket_keys(ngx_conf_t *
             goto failed;
         }
 
-        if (ngx_file_size(&fi) != 48) {
+        size = ngx_file_size(&fi);
+
+        if (size != 48 && size != 80) {
             ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
-                               "\"%V\" must be 48 bytes", &file.name);
+                               "\"%V\" must be 48 or 80 bytes", &file.name);
             goto failed;
         }
 
-        n = ngx_read_file(&file, buf, 48, 0);
+        n = ngx_read_file(&file, buf, size, 0);
 
         if (n == NGX_ERROR) {
             ngx_conf_log_error(NGX_LOG_CRIT, cf, ngx_errno,
@@ -2913,10 +2916,10 @@ ngx_ssl_session_ticket_keys(ngx_conf_t *
             goto failed;
         }
 
-        if (n != 48) {
+        if ((size_t) n != size) {
             ngx_conf_log_error(NGX_LOG_CRIT, cf, 0,
                                ngx_read_file_n " \"%V\" returned only "
-                               "%z bytes instead of 48", &file.name, n);
+                               "%z bytes instead of %uz", &file.name, n, size);
             goto failed;
         }
 
@@ -2925,9 +2928,18 @@ ngx_ssl_session_ticket_keys(ngx_conf_t *
             goto failed;
         }
 
-        ngx_memcpy(key->name, buf, 16);
-        ngx_memcpy(key->aes_key, buf + 16, 16);
-        ngx_memcpy(key->hmac_key, buf + 32, 16);
+        if (size == 48) {
+            key->size = 48;
+            ngx_memcpy(key->name, buf, 16);
+            ngx_memcpy(key->aes_key, buf + 16, 16);
+            ngx_memcpy(key->hmac_key, buf + 32, 16);
+
+        } else {
+            key->size = 80;
+            ngx_memcpy(key->name, buf, 16);
+            ngx_memcpy(key->hmac_key, buf + 16, 32);
+            ngx_memcpy(key->aes_key, buf + 48, 32);
+        }
 
         if (ngx_close_file(file.fd) == NGX_FILE_ERROR) {
             ngx_log_error(NGX_LOG_ALERT, cf->log, ngx_errno,
@@ -2972,6 +2984,7 @@ ngx_ssl_session_ticket_key_callback(ngx_
     unsigned char *name, unsigned char *iv, EVP_CIPHER_CTX *ectx,
     HMAC_CTX *hctx, int enc)
 {
+    size_t                         size;
     SSL_CTX                       *ssl_ctx;
     ngx_uint_t                     i;
     ngx_array_t                   *keys;
@@ -2986,7 +2999,6 @@ ngx_ssl_session_ticket_key_callback(ngx_
     c = ngx_ssl_get_connection(ssl_conn);
     ssl_ctx = c->ssl->session_ctx;
 
-    cipher = EVP_aes_128_cbc();
 #ifdef OPENSSL_NO_SHA256
     digest = EVP_sha1();
 #else
@@ -3008,6 +3020,15 @@ ngx_ssl_session_ticket_key_callback(ngx_
                        ngx_hex_dump(buf, key[0].name, 16) - buf, buf,
                        SSL_session_reused(ssl_conn) ? "reused" : "new");
 
+        if (key[0].size == 48) {
+            cipher = EVP_aes_128_cbc();
+            size = 16;
+
+        } else {
+            cipher = EVP_aes_256_cbc();
+            size = 32;
+        }
+
         if (RAND_bytes(iv, EVP_CIPHER_iv_length(cipher)) != 1) {
             ngx_ssl_error(NGX_LOG_ALERT, c->log, 0, "RAND_bytes() failed");
             return -1;
@@ -3020,12 +3041,12 @@ ngx_ssl_session_ticket_key_callback(ngx_
         }
 
 #if OPENSSL_VERSION_NUMBER >= 0x10000000L
-        if (HMAC_Init_ex(hctx, key[0].hmac_key, 16, digest, NULL) != 1) {
+        if (HMAC_Init_ex(hctx, key[0].hmac_key, size, digest, NULL) != 1) {
             ngx_ssl_error(NGX_LOG_ALERT, c->log, 0, "HMAC_Init_ex() failed");
             return -1;
         }
 #else
-        HMAC_Init_ex(hctx, key[0].hmac_key, 16, digest, NULL);
+        HMAC_Init_ex(hctx, key[0].hmac_key, size, digest, NULL);
 #endif
 
         ngx_memcpy(name, key[0].name, 16);
@@ -3054,13 +3075,22 @@ ngx_ssl_session_ticket_key_callback(ngx_
                        ngx_hex_dump(buf, key[i].name, 16) - buf, buf,
                        (i == 0) ? " (default)" : "");
 
+        if (key[i].size == 48) {
+            cipher = EVP_aes_128_cbc();
+            size = 16;
+
+        } else {
+            cipher = EVP_aes_256_cbc();
+            size = 32;
+        }
+
 #if OPENSSL_VERSION_NUMBER >= 0x10000000L
-        if (HMAC_Init_ex(hctx, key[i].hmac_key, 16, digest, NULL) != 1) {
+        if (HMAC_Init_ex(hctx, key[i].hmac_key, size, digest, NULL) != 1) {
             ngx_ssl_error(NGX_LOG_ALERT, c->log, 0, "HMAC_Init_ex() failed");
             return -1;
         }
 #else
-        HMAC_Init_ex(hctx, key[i].hmac_key, 16, digest, NULL);
+        HMAC_Init_ex(hctx, key[i].hmac_key, size, digest, NULL);
 #endif
 
         if (EVP_DecryptInit_ex(ectx, cipher, NULL, key[i].aes_key, iv) != 1) {
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -117,9 +117,10 @@ typedef struct {
 #ifdef SSL_CTRL_SET_TLSEXT_TICKET_KEY_CB
 
 typedef struct {
+    size_t                      size;
     u_char                      name[16];
-    u_char                      aes_key[16];
-    u_char                      hmac_key[16];
+    u_char                      hmac_key[32];
+    u_char                      aes_key[32];
 } ngx_ssl_session_ticket_key_t;
 
 #endif