From: Remi Tricot-Le Breton <rlebreton@haproxy.com>
Date: Mon, 17 Aug 2026 13:26:24 +0000 (+0200)
Subject: BUG/MEDIUM: ssl: Fix unprotected 'ssl_sock_choose_sni_ctx' calls
X-Git-Tag: v3.5-dev5~24
X-Git-Url: https://git.kaiwu.me/?a=commitdiff_plain;h=e80bcb3eacbec961c90cd471fda9ce610d769a07;p=haproxy.git

BUG/MEDIUM: ssl: Fix unprotected 'ssl_sock_choose_sni_ctx' calls

The 'ssl_sock_choose_sni_ctx' function accesses the sni tree and it
mostly covered by a read/write lock which was not taken around two of
its uses. One of them could be reached by using the SSL-related CLI
commands and the other one when the generate-cert mechanism is used. So
even if it's in a not that common use case, a race could still happen
and end up crashing.

Note that this requires that the read lock is properly released
before calling ssl_sock_generate_certificate() so as to avoid a
possible read-lock recursion (it was verified that this is safe).

This patch should be backported up to 3.0.

Reported-by: Claude (ANT-2026-VFR5JH3R)
---

diff --git a/src/ssl_clienthello.c b/src/ssl_clienthello.c
index 3148de24d..5cb94e685 100644
--- a/src/ssl_clienthello.c
+++ b/src/ssl_clienthello.c
@@ -629,15 +629,18 @@ sni_lookup:
 		}
 	}
 	if (!node) {
+		/* Nothing more to look up in the tree, and
+		 * ssl_sock_generate_certificate() takes this same lock in read
+		 * mode, which must not be done recursively.
+		 */
+		HA_RWLOCK_RDUNLOCK(SNI_LOCK, &s->sni_lock);
 #if (!defined SSL_NO_GENERATE_CERTIFICATES)
 		if (s->options & BC_O_GENERATE_CERTS && ssl_sock_generate_certificate(servername, s, ssl)) {
 			/* switch ctx done in ssl_sock_generate_certificate */
-			HA_RWLOCK_RDUNLOCK(SNI_LOCK, &s->sni_lock);
 			TRACE_STATE("No context found, generate certificate", SSL_EV_CONN_SWITCHCTX_CB, NULL, ssl, servername);
 			return SSL_TLSEXT_ERR_OK;
 		}
 #endif
-		HA_RWLOCK_RDUNLOCK(SNI_LOCK, &s->sni_lock);
 
 		if (!(s->ssl_options & BC_SSL_O_STRICT_SNI) && !default_lookup) {
 			/* we didn't find a SNI, and we didn't look for a default
diff --git a/src/ssl_gencert.c b/src/ssl_gencert.c
index b608f552c..4bff2d2d8 100644
--- a/src/ssl_gencert.c
+++ b/src/ssl_gencert.c
@@ -132,9 +132,12 @@ static SSL_CTX *ssl_sock_do_create_cert(const char *servername, struct bind_conf
 	if (!ssl_sock_sni_is_valid(servername))
 		goto mkcert_error;
 
+	HA_RWLOCK_RDLOCK(SNI_LOCK, &bind_conf->sni_lock);
 	sni_ctx = ssl_sock_choose_sni_ctx(bind_conf, NULL, "", 1, 1);
-	if (!sni_ctx)
+	if (!sni_ctx) {
+		HA_RWLOCK_RDUNLOCK(SNI_LOCK, &bind_conf->sni_lock);
 		goto mkcert_error;
+	}
 
 	/* Get the private key of the default certificate and use it */
 #ifdef HAVE_SSL_CTX_get0_privatekey
@@ -144,8 +147,12 @@ static SSL_CTX *ssl_sock_do_create_cert(const char *servername, struct bind_conf
 	if (tmp_ssl)
 		pkey = SSL_get_privatekey(tmp_ssl);
 #endif
-	if (!pkey)
+	if (!pkey) {
+		HA_RWLOCK_RDUNLOCK(SNI_LOCK, &bind_conf->sni_lock);
 		goto mkcert_error;
+	}
+	EVP_PKEY_up_ref(pkey);
+	HA_RWLOCK_RDUNLOCK(SNI_LOCK, &bind_conf->sni_lock);
 
 	/* Create the certificate */
 	if (!(newcrt = X509_new()))
@@ -302,6 +309,7 @@ static SSL_CTX *ssl_sock_do_create_cert(const char *servername, struct bind_conf
  end:
 	if (ctmp) NCONF_free(ctmp);
 	if (tmp_ssl) SSL_free(tmp_ssl);
+	EVP_PKEY_free(pkey);
 	return ssl_ctx;
 
  mkcert_error:
@@ -309,6 +317,7 @@ static SSL_CTX *ssl_sock_do_create_cert(const char *servername, struct bind_conf
 	if (tmp_ssl) SSL_free(tmp_ssl);
 	if (ssl_ctx) SSL_CTX_free(ssl_ctx);
 	if (newcrt)  X509_free(newcrt);
+	EVP_PKEY_free(pkey);
 	return NULL;
 }
 
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index 4fcf0ab67..628f936ad 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -5657,12 +5657,15 @@ int ssl_sock_prepare_bind_conf(struct bind_conf *bind_conf)
 		struct sni_ctx *sni_ctx;
 
 		/* if we use the generate-certificates option, look for the first default cert available */
+		HA_RWLOCK_RDLOCK(SNI_LOCK, &bind_conf->sni_lock);
 		sni_ctx = ssl_sock_choose_sni_ctx(bind_conf, NULL, "", 1, 1);
 		if (!sni_ctx) {
+			HA_RWLOCK_RDUNLOCK(SNI_LOCK, &bind_conf->sni_lock);
 			ha_alert("Proxy '%s': no SSL certificate specified for bind '%s' and 'generate-certificates' option at [%s:%d] (use 'crt').\n",
 				 px->id, bind_conf->arg, bind_conf->file, bind_conf->line);
 			return -1;
 		}
+		HA_RWLOCK_RDUNLOCK(SNI_LOCK, &bind_conf->sni_lock);
 	}
 
 	if (!ssl_shctx && global.tune.sslcachesize) {