generate-certificates and SAN

[r***@gmail.com]

I'm using generate-certificates to save some hassle with a lot of api backends. For the most
part it works great, but I ran into trouble with a java client (OkHttp) which wouldn't
trust the haproxy-generated certificates.

Some clients such as Google Chrome and OkHttp do not trust the server certificate
unless it has a Subject Alternate Name. For the generate-certificates case it seems safe
and unambiguous to do this, because it is based on the SNI name which must be a DNS name?

Example configuration demonstrating the issue. You'll get a warning from Chrome if you
try to hit this config, but if the SAN is set the warning goes away. If you apply the really
hacky patch (apologies: I'm afraid of openssl), there won't be a verification issue because
the SAN extension with the DNS name is available.

---
frontend fe
mode http
bind :8993 ssl crt default.chain ca-sign-file ca.chain generate-certificates no-sslv3
use_backend be

backend be
mode http
stats uri /
---
src/ssl_sock.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index 50af63b2..d994dcae 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -1684,6 +1684,8 @@ ssl_sock_do_create_cert(const char *servername, struct bind_conf *bind_conf, SSL
SSL *tmp_ssl = NULL;
CONF *ctmp = NULL;
X509_NAME *name;
+ X509_EXTENSION *san_ext;
+ char *san_value;
const EVP_MD *digest;
X509V3_CTX ctx;
unsigned int i;
@@ -1754,6 +1756,24 @@ ssl_sock_do_create_cert(const char *servername, struct bind_conf *bind_conf, SSL
X509_EXTENSION_free(ext);
}

+ /* Add Subject Alternative Name for the server */
+ san_value = (char *)malloc(4 + strlen(servername) + 1);
+ if (!san_value)
+ goto mkcert_error;
+ *san_value = '\0';
+ strcat(san_value, "DNS:");
+ strcat(san_value, servername);
+ if (!(san_ext = X509V3_EXT_conf_nid(NULL, &ctx, NID_subject_alt_name, san_value))) {
+ free(san_value);
+ goto mkcert_error;
+ }
+ free(san_value);
+ if (!X509_add_ext(newcrt, san_ext, -1)) {
+ X509_EXTENSION_free(san_ext);
+ goto mkcert_error;
+ }
+ X509_EXTENSION_free(san_ext);
+
/* Sign the certificate with the CA private key */

key_type = EVP_PKEY_base_id(capkey);