tcptls.c: Made TLS handle a certificate chain file.

Thanks to Guillaume Martres for doing the necessary research to validate
the change.

(closes issue ASTERISK-17727)
Reported by: LN
Patches:
      use_certificate_chain.patch (license #5864) patch uploaded by st
      documente_certificate_chain.patch (license #6576) patch uploaded by Guillaume Martres
........

Merged revisions 407272 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@407273 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configs/sip.conf.sample

@@ -526,8 +526,10 @@ srvlookup=yes                   ; Enable DNS SRV lookups on outbound calls
 
 ;
 ;------------------------ TLS settings ------------------------------------------------------------
-;tlscertfile=</path/to/certificate.pem> ; Certificate file (*.pem format only) to use for TLS connections
-                                        ; default is to look for "asterisk.pem" in current directory
+;tlscertfile=</path/to/certificate.pem> ; Certificate chain (*.pem format only) to use for TLS connections
+                                        ; The certificates must be sorted starting with the subject's certificate
+                                        ; and followed by intermediate CA certificates if applicable.
+                                        ; Default is to look for "asterisk.pem" in current directory
 
 ;tlsprivatekey=</path/to/private.pem> ; Private key file (*.pem format only) for TLS connections.
                                       ; If no tlsprivatekey is specified, tlscertfile is searched for

main/tcptls.c

@@ -393,7 +393,7 @@ static int __ssl_setup(struct ast_tls_config *cfg, int client)
 
 	if (!ast_strlen_zero(cfg->certfile)) {
 		char *tmpprivate = ast_strlen_zero(cfg->pvtfile) ? cfg->certfile : cfg->pvtfile;
-		if (SSL_CTX_use_certificate_file(cfg->ssl_ctx, cfg->certfile, SSL_FILETYPE_PEM) == 0) {
+		if (SSL_CTX_use_certificate_chain_file(cfg->ssl_ctx, cfg->certfile) == 0) {
 			if (!client) {
 				/* Clients don't need a certificate, but if its setup we can use it */
 				ast_verb(0, "SSL error loading cert file. <%s>\n", cfg->certfile);