MINOR: ssl: add curve suite for ECDHE negotiation

Add 'curves' parameter on 'bind' and for 'crt-list' to set curve suite.
(ex: curves X25519:P-256)
diff --git a/doc/configuration.txt b/doc/configuration.txt
index abb36df..d9ef878 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -10093,6 +10093,14 @@
   Sets the socket's backlog to this value. If unspecified, the frontend's
   backlog is used instead, which generally defaults to the maxconn value.
 
+curves <curves>
+  This setting is only available when support for OpenSSL was built in. It sets
+  the string describing the list of elliptic curves algorithms ("curve suite")
+  that are negotiated during the SSL/TLS handshake with ECDHE. The format of the
+  string is a colon-delimited list of curve name.
+  Example: "X25519:P-256" (without quote)
+  When "curves" is set, "ecdhe" parameter is ignored.
+
 ecdhe <named curve>
   This setting is only available when support for OpenSSL was built in. It sets
   the named curve (RFC 4492) used to generate ECDH ephemeral keys. By default,
@@ -10254,7 +10262,7 @@
         <crtfile> [\[<sslbindconf> ...\]] [[!]<snifilter> ...]
 
   sslbindconf support "npn", "alpn", "verify", "ca_file", "crl_file", "ecdhe",
-  "ciphers" configuration and ssl options (see "ssl-default-bind-options").
+  "curves", "ciphers" configuration and ssl options (see "ssl-default-bind-options").
   It override the configuration set in bind line for the certificate.
 
   Wildcards are supported in the SNI filter. Negative filter are also supported,
diff --git a/include/types/listener.h b/include/types/listener.h
index b534c47..d813deb 100644
--- a/include/types/listener.h
+++ b/include/types/listener.h
@@ -130,6 +130,7 @@
 	char *ca_file;             /* CAfile to use on verify */
 	char *crl_file;            /* CRLfile to use on verify */
 	char *ciphers;             /* cipher suite to use if non-null */
+	char *curves;	           /* curves suite to use for ECDHE */
 	char *ecdhe;               /* named curve to use for ECDHE */
 	int ssl_options;           /* ssl options */
 #endif
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index b94166c..95f979c 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -2627,6 +2627,8 @@
 		conf->crl_file = NULL;
 		free(conf->ciphers);
 		conf->ciphers = NULL;
+		free(conf->curves);
+		conf->curves = NULL;
 		free(conf->ecdhe);
 		conf->ecdhe = NULL;
 	}
@@ -2851,6 +2853,7 @@
 	struct ssl_bind_conf *ssl_conf_cur;
 	int conf_ssl_options = bind_conf->ssl_conf.ssl_options | (ssl_conf ? ssl_conf->ssl_options : 0);
 	const char *conf_ciphers;
+	const char *conf_curves = NULL;
 
 	/* Make sure openssl opens /dev/urandom before the chroot */
 	if (!ssl_initialize_random()) {
@@ -3040,8 +3043,22 @@
 	SSL_CTX_set_tlsext_servername_callback(ctx, ssl_sock_switchctx_cbk);
 	SSL_CTX_set_tlsext_servername_arg(ctx, bind_conf);
 #endif
+#if OPENSSL_VERSION_NUMBER >= 0x1000200fL
+	conf_curves = (ssl_conf && ssl_conf->curves) ? ssl_conf->curves : bind_conf->ssl_conf.curves;
+	if (conf_curves) {
+		if (!SSL_CTX_set1_curves_list(ctx, conf_curves)) {
+			Alert("Proxy '%s': unable to set SSL curves list to '%s' for bind '%s' at [%s:%d].\n",
+			      curproxy->id, conf_curves, bind_conf->arg, bind_conf->file, bind_conf->line);
+			cfgerr++;
+		}
+#ifndef OPENSSL_IS_BORINGSSL
+		else
+			SSL_CTX_set_ecdh_auto(ctx, 1);
+#endif
+	}
+#endif
 #if defined(SSL_CTX_set_tmp_ecdh) && !defined(OPENSSL_NO_ECDH)
-	{
+	if (!conf_curves) {
 		int i;
 		EC_KEY  *ecdh;
 		const char *ecdhe = (ssl_conf && ssl_conf->ecdhe) ? ssl_conf->ecdhe :
@@ -5511,6 +5528,28 @@
 	return ssl_bind_parse_crl_file(args, cur_arg, px, &conf->ssl_conf, err);
 }
 
+/* parse the "curves" bind keyword keyword */
+static int ssl_bind_parse_curves(char **args, int cur_arg, struct proxy *px, struct ssl_bind_conf *conf, char **err)
+{
+#if OPENSSL_VERSION_NUMBER >= 0x1000200fL
+	if (!*args[cur_arg + 1]) {
+		if (err)
+			memprintf(err, "'%s' : missing curve suite", args[cur_arg]);
+		return ERR_ALERT | ERR_FATAL;
+	}
+	conf->curves = strdup(args[cur_arg + 1]);
+	return 0;
+#else
+	if (err)
+		memprintf(err, "'%s' : library does not support curve suite", args[cur_arg]);
+	return ERR_ALERT | ERR_FATAL;
+#endif
+}
+static int bind_parse_curves(char **args, int cur_arg, struct proxy *px, struct bind_conf *conf, char **err)
+{
+	return ssl_bind_parse_curves(args, cur_arg, px, &conf->ssl_conf, err);
+}
+
 /* parse the "ecdhe" bind keyword keyword */
 static int ssl_bind_parse_ecdhe(char **args, int cur_arg, struct proxy *px, struct ssl_bind_conf *conf, char **err)
 {
@@ -6814,6 +6853,7 @@
 	{ "ca-file",               ssl_bind_parse_ca_file,          1 }, /* set CAfile to process verify on client cert */
 	{ "ciphers",               ssl_bind_parse_ciphers,          1 }, /* set SSL cipher suite */
 	{ "crl-file",              ssl_bind_parse_crl_file,         1 }, /* set certificat revocation list file use on client cert verify */
+	{ "curves",                ssl_bind_parse_curves,           1 }, /* set SSL curve suite */
 	{ "ecdhe",                 ssl_bind_parse_ecdhe,            1 }, /* defines named curve for elliptic curve Diffie-Hellman */
 	{ "force-sslv3",           ssl_bind_parse_force_sslv3,      0 }, /* force SSLv3 */
 	{ "force-tlsv10",          ssl_bind_parse_force_tlsv10,     0 }, /* force TLSv10 */
@@ -6840,6 +6880,7 @@
 	{ "crt",                   bind_parse_crt,             1 }, /* load SSL certificates from this location */
 	{ "crt-ignore-err",        bind_parse_ignore_err,      1 }, /* set error IDs to ingore on verify depth == 0 */
 	{ "crt-list",              bind_parse_crt_list,        1 }, /* load a list of crt from this location */
+	{ "curves",                bind_parse_curves,          1 }, /* set SSL curve suite */
 	{ "ecdhe",                 bind_parse_ecdhe,           1 }, /* defines named curve for elliptic curve Diffie-Hellman */
 	{ "force-sslv3",           bind_parse_force_sslv3,     0 }, /* force SSLv3 */
 	{ "force-tlsv10",          bind_parse_force_tlsv10,    0 }, /* force TLSv10 */