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.

2 files changed, 47 insertions, 16 deletions

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index c98e3c2b0..3c74b7b21 100644
--- 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_rbtree_node_t *temp,
 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 *cf, ngx_ssl_t *ssl, ngx_array_t *paths)
             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 *cf, ngx_ssl_t *ssl, ngx_array_t *paths)
             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 *cf, ngx_ssl_t *ssl, ngx_array_t *paths)
             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_ssl_conn_t *ssl_conn,
     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_ssl_conn_t *ssl_conn,
     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_ssl_conn_t *ssl_conn,
                        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_ssl_conn_t *ssl_conn,
         }
 
 #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_ssl_conn_t *ssl_conn,
                        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) {
diff --git a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
index c0223070c..e093e10c5 100644
--- 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