Explain the 3 SSL_CTX we have

[exim.git] / src / src / tls-openssl.c

diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c
index bbf6855ffd0dc767f829f39e5f43430f2ff09353..08b92bae56f9e3023ed88f804a71d4a97704b6a0 100644 (file)
--- a/src/src/tls-openssl.c
+++ b/src/src/tls-openssl.c
@@ -46,12 +46,31 @@ static BOOL client_verify_callback_called = FALSE;
 static BOOL server_verify_callback_called = FALSE;
 static const uschar *sid_ctx = US"exim";
 
+/* We have three different contexts to care about.
+
+Simple case: client, `client_ctx`
+ As a client, we can be doing a callout or cut-through delivery while receiving
+ a message.  So we have a client context, which should have options initialised
+ from the SMTP Transport.
+
+Server:
+ There are two cases: with and without ServerNameIndication from the client.
+ Given TLS SNI, we can be using different keys, certs and various other
+ configuration settings, because they're re-expanded with $tls_sni set.  This
+ allows vhosting with TLS.  This SNI is sent in the handshake.
+ A client might not send SNI, so we need a fallback, and an initial setup too.
+ So as a server, we start out using `server_ctx`.
+ If SNI is sent by the client, then we as server, mid-negotiation, try to clone
+ `server_sni` from `server_ctx` and then initialise settings by re-expanding
+ configuration.
+*/
+
 static SSL_CTX *client_ctx = NULL;
 static SSL_CTX *server_ctx = NULL;
 static SSL     *client_ssl = NULL;
 static SSL     *server_ssl = NULL;
+
 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
-static SSL_CTX *client_sni = NULL;
 static SSL_CTX *server_sni = NULL;
 #endif
 
@@ -317,11 +336,7 @@ Returns:    TRUE if OK (nothing to set up, or setup worked)
 */
 
 static BOOL
-<<<<<<< HEAD
 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
-=======
-init_dh(SSL_CTX *ctx, uschar *dhparam, host_item *host)
->>>>>>> Dual-tls - split management of TLS into in- and out-bound connection-handling.
 {
 BIO *bio;
 DH *dh;
@@ -546,7 +561,10 @@ uschar *expanded;
 if (cbinfo->certificate == NULL)
   return OK;
 
-if (Ustrstr(cbinfo->certificate, US"tls_sni"))
+if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
+    Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
+    Ustrstr(cbinfo->certificate, US"tls_out_sni")
+   )
   reexpand_tls_files_for_sni = TRUE;
 
 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
@@ -671,7 +689,7 @@ if (cbinfo->server_cipher_list)
 if (cbinfo->ocsp_file)
   {
   SSL_CTX_set_tlsext_status_cb(server_sni, tls_stapling_cb);
-  SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
+  SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
   }
 #endif
 
@@ -683,7 +701,7 @@ OCSP information. */
 rc = tls_expand_session_files(server_sni, cbinfo);
 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
 
-rc = init_dh(ctx_sni, cbinfo->dhparam, NULL);
+rc = init_dh(server_sni, cbinfo->dhparam, NULL);
 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
 
 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
@@ -726,7 +744,7 @@ response_der_len = i2d_OCSP_RESPONSE(cbinfo->ocsp_response, &response_der);
 if (response_der_len <= 0)
   return SSL_TLSEXT_ERR_NOACK;
 
-SSL_set_tlsext_status_ocsp_resp(ssl, response_der, response_der_len);
+SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
 return SSL_TLSEXT_ERR_OK;
 }
 
@@ -852,11 +870,7 @@ else
 
 /* Initialize with DH parameters if supplied */
 
-<<<<<<< HEAD
-if (!init_dh(ctx, dhparam, host)) return DEFER;
-=======
 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
->>>>>>> Dual-tls - split management of TLS into in- and out-bound connection-handling.
 
 /* Set up certificate and key (and perhaps OCSP info) */
 
@@ -874,8 +888,8 @@ if (host == NULL)
   callback is invoked. */
   if (cbinfo->ocsp_file)
     {
-    SSL_CTX_set_tlsext_status_cb(ctx, tls_stapling_cb);
-    SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
+    SSL_CTX_set_tlsext_status_cb(server_ctx, tls_stapling_cb);
+    SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
     }
 #endif
   /* We always do this, so that $tls_sni is available even if not used in
@@ -1342,7 +1356,11 @@ if (sni)
   {
   if (!expand_check(sni, US"tls_sni", &tls_out.sni))
     return FAIL;
-  if (!Ustrlen(tls_out.sni))
+  if (tls_out.sni == NULL)
+    {
+    DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
+    }
+  else if (!Ustrlen(tls_out.sni))
     tls_out.sni = NULL;
   else
     {
@@ -1493,16 +1511,17 @@ Only used by the client-side TLS.
 */
 
 int
-tls_read(uschar *buff, size_t len)
+tls_read(BOOL is_server, uschar *buff, size_t len)
 {
+SSL *ssl = is_server ? server_ssl : client_ssl;
 int inbytes;
 int error;
 
-DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", client_ssl,
+DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
   buff, (unsigned int)len);
 
-inbytes = SSL_read(client_ssl, CS buff, len);
-error = SSL_get_error(client_ssl, inbytes);
+inbytes = SSL_read(ssl, CS buff, len);
+error = SSL_get_error(ssl, inbytes);
 
 if (error == SSL_ERROR_ZERO_RETURN)
   {
@@ -1601,6 +1620,7 @@ void
 tls_close(BOOL is_server, BOOL shutdown)
 {
 SSL **sslp = is_server ? &server_ssl : &client_ssl;
+int *fdp = is_server ? &tls_in.active : &tls_out.active;
 
 if (*fdp < 0) return;  /* TLS was not active */