stunnel/stunnel-5.72-speed-up-loading-client-CA-list.patch

From 5f0b818f62720d5bd8b8c9c631604ddb4c992be7 Mon Sep 17 00:00:00 2001
From: Clemens Lang <cllang@redhat.com>
Date: Wed, 31 Jul 2024 15:35:24 +0200
Subject: [PATCH] src/verify.c: Speed up loading client CA list

Do not attempt to load and print all trusted CAs unless we need them to
invoke SSL_CTX_set_client_CA_list(3). Loading all trusted CAs can be
slow, especially if there are many. The CAdir format allows OpenSSL to
only load them on demand, avoiding this overhead.

Additionally, SSL_CTX_load_verify_locations(3) supports file formats
that SSL_load_client_CA_file(3) and SSL_add_*_cert_subjects_to_stack(3)
do not support, for example certificates in the BEGIN TRUSTED
CERTIFICATE format. Valid configurations with older stunnel versions
that point to such a file would otherwise needlessly start failing.

Additionally, use SSL_load_client_CA_file(3) to load certificates from
a file rather than SSL_add_file_cert_subjects_to_stack(3), since the
former uses a hashtable for deduplication, but the latter relies on
a sorted STACK_OF(X509_NAME). The sorting is exceptionally slow in
OpenSSL, because the comparison function for X509_NAMEs converts them to
DER involving a memory allocation, which is already expensive, but even
more expensive when used with stunnel's custom allocator functions.

An upstream PR openssl/openssl#25056 will eventually fix this, but it
will take quite a while for this to arrive on users' systems, and it
will likely not be backported into older affected versions of OpenSSL or
their forks.

Related: RHEL-50154
Related: RHEL-46411
Signed-off-by: Clemens Lang <cllang@redhat.com>
---
 src/verify.c | 42 ++++++++++++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 14 deletions(-)

diff --git a/src/verify.c b/src/verify.c
index 56ab130..d1d3849 100644
--- a/src/verify.c
+++ b/src/verify.c
@@ -95,10 +95,35 @@ NOEXPORT int init_ca(SERVICE_OPTIONS *section) {
         if(!SSL_CTX_load_verify_locations(section->ctx,
                 section->ca_file, section->ca_dir)) {
             sslerror("SSL_CTX_load_verify_locations");
+            return 1; /* FAILED */
         }
     }
 
-    ca_dn=sk_X509_NAME_new_null();
+    /* Do not attempt to load and print all trusted CAs unless we need them to
+       invoke SSL_CTX_set_client_CA_list(3). Loading all trusted CAs can be
+       slow, especially if there are many. The CAdir format allows OpenSSL to
+       only load them on demand.
+       Additionally, SSL_CTX_load_verify_locations(3) supports file formats
+       that SSL_load_client_CA_file(3) and SSL_add_*_cert_subjects_to_stack(3)
+       do not support, for example certificates in the BEGIN TRUSTED
+       CERTIFICATE format. Valid configurations with older stunnel versions
+       that point to such a file would otherwise needlessly start failing. */
+    if(section->option.client)
+        return 0; /* OK */
+
+    if(section->ca_file)
+        /* SSL_load_client_CA_file is a lot faster than
+           SSL_add_file_cert_subjects_to_stack(). Use it for ca_file if
+           specified, then add the rest of the certificates to this stack. */
+        ca_dn=SSL_load_client_CA_file(section->ca_file);
+
+    if (!ca_dn)
+        /* ca_file not set, or SSL_load_client_CA_file(3) failed. */
+        ca_dn=sk_X509_NAME_new_null();
+
+    /* client CA list initialization from directory */
+    if(section->ca_dir)
+        SSL_add_dir_cert_subjects_to_stack(ca_dn, section->ca_dir);
 
 #ifndef OPENSSL_NO_ENGINE
     /* CA and client CA list initialization with the engine */
@@ -115,24 +140,13 @@ NOEXPORT int init_ca(SERVICE_OPTIONS *section) {
     }
 #endif
 
-    /* client CA list initialization with the file and/or directory */
-    if(section->ca_file)
-        SSL_add_file_cert_subjects_to_stack(ca_dn, section->ca_file);
-    if(section->ca_dir)
-        SSL_add_dir_cert_subjects_to_stack(ca_dn, section->ca_dir);
-
     if(!sk_X509_NAME_num(ca_dn)) {
         sk_X509_NAME_pop_free(ca_dn, X509_NAME_free);
         return 1; /* FAILED */
     }
 
-    if(section->option.client) {
-        print_CA_list("Configured trusted server CA", ca_dn);
-        sk_X509_NAME_pop_free(ca_dn, X509_NAME_free);
-    } else { /* only set the client CA list on the server */
-        print_CA_list("Configured trusted client CA", ca_dn);
-        SSL_CTX_set_client_CA_list(section->ctx, ca_dn);
-    }
+    print_CA_list("Configured trusted client CA", ca_dn);
+    SSL_CTX_set_client_CA_list(section->ctx, ca_dn);
 
     return 0; /* OK */
 }
-- 
2.45.2