On Mon, Sep 05, 2016 at 03:25:22AM +0200, Alexander Bluhm wrote:
> Hi,
>
> Add an option to give syslogd a server CA that is used to validate
> client certificates. This prevent that malicious clients can send
> fake messages.
>
> ok?
Anyone?
>
> bluhm
>
> Index: usr.sbin/syslogd/syslogd.8
> ===================================================================
> RCS file: /data/mirror/openbsd/cvs/src/usr.sbin/syslogd/syslogd.8,v
> retrieving revision 1.42
> diff -u -p -r1.42 syslogd.8
> --- usr.sbin/syslogd/syslogd.8 12 Jul 2016 23:04:30 -0000 1.42
> +++ usr.sbin/syslogd/syslogd.8 5 Sep 2016 01:18:00 -0000
> @@ -44,6 +44,7 @@
> .Op Fl C Ar CAfile
> .Op Fl c Ar cert_file
> .Op Fl f Ar config_file
> +.Op Fl K Ar server_CAfile
> .Op Fl k Ar key_file
> .Op Fl m Ar mark_interval
> .Op Fl p Ar log_socket
> @@ -83,6 +84,11 @@ PEM encoded file containing CA certifica
> validation;
> the default is
> .Pa /etc/ssl/cert.pem .
> +Validate remote server certificates and their hostnames with this
> +CA to prevent that malicious servers read messages.
> +This validation can be explicitly turned off using the
> +.Fl V
> +switch.
> .It Fl c Ar cert_file
> PEM encoded file containing the client certificate for TLS connections
> to a remote host.
> @@ -102,6 +108,12 @@ the default is
> .Pa /etc/syslog.conf .
> .It Fl h
> Include the hostname when forwarding messages to a remote host.
> +.It Fl K Ar server_CAfile
> +PEM encoded file containing CA certificates used for certificate
> +valitation on the local server socket.
> +By default incomming connections from any TLS server are allowed.
> +Enforce client certificates and validate them with this CA to prevent
> +that malicious clients send fake messages.
> .It Fl k Ar key_file
> PEM encoded file containing the client private key for TLS connections
> to a remote host.
> @@ -170,7 +182,8 @@ accept input from the UDP port.
> Some software wants this, but you can be subjected to a variety of
> attacks over the network, including attackers remotely filling logs.
> .It Fl V
> -Do not perform server certificate and hostname validation.
> +Do not perform remote server certificate and hostname validation
> +when sending messages.
> .El
> .Pp
> .Nm
> Index: usr.sbin/syslogd/syslogd.c
> ===================================================================
> RCS file: /data/mirror/openbsd/cvs/src/usr.sbin/syslogd/syslogd.c,v
> retrieving revision 1.212
> diff -u -p -r1.212 syslogd.c
> --- usr.sbin/syslogd/syslogd.c 29 Aug 2016 20:31:56 -0000 1.212
> +++ usr.sbin/syslogd/syslogd.c 5 Sep 2016 01:20:06 -0000
> @@ -225,8 +225,9 @@ struct tls *server_ctx;
> struct tls_config *client_config, *server_config;
> const char *CAfile = "/etc/ssl/cert.pem"; /* file containing CA certificates
> */
> int NoVerify = 0; /* do not verify TLS server x509 certificate */
> -char *ClientCertfile = NULL;
> -char *ClientKeyfile = NULL;
> +const char *ClientCertfile = NULL;
> +const char *ClientKeyfile = NULL;
> +const char *ServerCAfile = NULL;
> int tcpbuf_dropped = 0; /* count messages dropped from TCP or TLS */
>
> #define CTL_READING_CMD 1
> @@ -356,7 +357,7 @@ main(int argc, char *argv[])
> int ch, i;
> int lockpipe[2] = { -1, -1}, pair[2], nullfd, fd;
>
> - while ((ch = getopt(argc, argv, "46a:C:c:dFf:hk:m:np:S:s:T:U:uV"))
> + while ((ch = getopt(argc, argv, "46a:C:c:dFf:hK:k:m:np:S:s:T:U:uV"))
> != -1)
> switch (ch) {
> case '4': /* disable IPv6 */
> @@ -388,6 +389,9 @@ main(int argc, char *argv[])
> case 'h': /* RFC 3164 hostnames */
> IncludeHostname = 1;
> break;
> + case 'K': /* verify client with CA file */
> + ServerCAfile = optarg;
> + break;
> case 'k': /* file containing client key */
> ClientKeyfile = optarg;
> break;
> @@ -625,6 +629,17 @@ main(int argc, char *argv[])
> break;
> }
>
> + if (ServerCAfile) {
> + if (tls_config_set_ca_file(server_config,
> + ServerCAfile) == -1) {
> + logerrortlsconf("Load server TLS CA failed",
> + server_config);
> + /* avoid reading default certs in chroot */
> + tls_config_set_ca_mem(server_config, "", 0);
> + } else
> + logdebug("Server CAfile %s\n", ServerCAfile);
> + tls_config_verify_client(server_config);
> + }
> tls_config_set_protocols(server_config, TLS_PROTOCOLS_ALL);
> if (tls_config_set_ciphers(server_config, "compat") != 0)
> logerrortlsconf("Set server TLS ciphers failed",
> @@ -1453,9 +1468,9 @@ usage(void)
>
> (void)fprintf(stderr,
> "usage: syslogd [-46dFhnuV] [-a path] [-C CAfile] [-c cert_file]\n"
> - "\t[-f config_file] [-k key_file] [-m mark_interval]\n"
> - "\t[-p log_socket] [-S listen_address] [-s reporting_socket]\n"
> - "\t[-T listen_address] [-U bind_address]\n");
> + "\t[-f config_file] [-K server_CAfile] [-k key_file]\n"
> + "\t[-m mark_interval] [-p log_socket] [-S listen_address]\n"
> + "\t[-s reporting_socket] [-T listen_address] [-U bind_address]\n");
> exit(1);
> }
>
