[Qemu-devel] [PATCH v4 4/4] char: introduce support for TLS encrypted TCP chardev backend

["Daniel P. Berrange" <berrange@redhat.com>]

This integrates support for QIOChannelTLS object in the TCP
chardev backend. If the 'tls-creds=NAME' option is passed with
the '-chardev tcp' argument, then it will setup the chardev
such that the client is required to establish a TLS handshake
when connecting. There is no support for checking the client
certificate against ACLs in this initial patch. This is pending
work to QOM-ify the ACL object code.

A complete invocation to run QEMU as the server for a TLS
encrypted serial dev might be

  $ qemu-system-x86_64 \
      -nodefconfig -nodefaults -device sga -display none \
      -chardev socket,id=s0,host=127.0.0.1,port=9000,tls-creds=tls0,server \
      -device isa-serial,chardev=s0 \
      -object tls-creds-x509,id=tls0,endpoint=server,verify-peer=off,\
         dir=/home/berrange/security/qemutls

To test with the gnutls-cli tool as the client:

  $ gnutls-cli --priority=NORMAL -p 9000 \
       --x509cafile=/home/berrange/security/qemutls/ca-cert.pem \
       127.0.0.1

If QEMU was told to use 'anon' credential type, then use the
priority string 'NORMAL:+ANON-DH' with gnutls-cli

Alternatively, if setting up a chardev to operate as a client,
then the TLS credentials registered must be for the client
endpoint. First a TLS server must be setup, which can be done
with the gnutls-serv tool

  $ gnutls-serv --priority=NORMAL -p 9000 --echo \
       --x509cafile=/home/berrange/security/qemutls/ca-cert.pem \
       --x509certfile=/home/berrange/security/qemutls/server-cert.pem \
       --x509keyfile=/home/berrange/security/qemutls/server-key.pem

Then QEMU can connect with

  $ qemu-system-x86_64 \
      -nodefconfig -nodefaults -device sga -display none \
      -chardev socket,id=s0,host=127.0.0.1,port=9000,tls-creds=tls0 \
      -device isa-serial,chardev=s0 \
      -object tls-creds-x509,id=tls0,endpoint=client,\
        dir=/home/berrange/security/qemutls

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 qapi-schema.json |   2 +
 qemu-char.c      | 136 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
 qemu-options.hx  |   9 +++-
 3 files changed, 134 insertions(+), 13 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json
index b3038b2..8d04897 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3146,6 +3146,7 @@
 #
 # @addr: socket address to listen on (server=true)
 #        or connect to (server=false)
+# @tls-creds: #optional the ID of the TLS credentials object (since 2.6)
 # @server: #optional create server socket (default: true)
 # @wait: #optional wait for incoming connection on server
 #        sockets (default: false).
@@ -3160,6 +3161,7 @@
 # Since: 1.4
 ##
 { 'struct': 'ChardevSocket', 'data': { 'addr'       : 'SocketAddress',
+                                     '*tls-creds'  : 'str',
                                      '*server'    : 'bool',
                                      '*wait'      : 'bool',
                                      '*nodelay'   : 'bool',
diff --git a/qemu-char.c b/qemu-char.c
index f0cea8a..7ded3c2 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -35,6 +35,7 @@
 #include "qemu/base64.h"
 #include "io/channel-socket.h"
 #include "io/channel-file.h"
+#include "io/channel-tls.h"
 
 #include <unistd.h>
 #include <fcntl.h>
@@ -2532,9 +2533,11 @@ static CharDriverState *qemu_chr_open_udp(QIOChannelSocket *sioc,
 /* TCP Net console */
 
 typedef struct {
-    QIOChannel *ioc;
+    QIOChannel *ioc; /* Client I/O channel */
+    QIOChannelSocket *sioc; /* Client master channel */
     QIOChannelSocket *listen_ioc;
     guint listen_tag;
+    QCryptoTLSCreds *tls_creds;
     int connected;
     int max_size;
     int do_telnetopt;
@@ -2776,6 +2779,8 @@ static void tcp_chr_disconnect(CharDriverState *chr)
             QIO_CHANNEL(s->listen_ioc), G_IO_IN, tcp_chr_accept, chr, NULL);
     }
     remove_fd_in_watch(chr);
+    object_unref(OBJECT(s->sioc));
+    s->sioc = NULL;
     object_unref(OBJECT(s->ioc));
     s->ioc = NULL;
     g_free(chr->filename);
@@ -2849,12 +2854,12 @@ static void tcp_chr_connect(void *opaque)
 {
     CharDriverState *chr = opaque;
     TCPCharDriver *s = chr->opaque;
-    QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(s->ioc);
 
     g_free(chr->filename);
-    chr->filename = sockaddr_to_str(&sioc->localAddr, sioc->localAddrLen,
-                                    &sioc->remoteAddr, sioc->remoteAddrLen,
-                                    s->is_listen, s->is_telnet);
+    chr->filename = sockaddr_to_str(
+        &s->sioc->localAddr, s->sioc->localAddrLen,
+        &s->sioc->remoteAddr, s->sioc->remoteAddrLen,
+        s->is_listen, s->is_telnet);
 
     s->connected = 1;
     if (s->ioc) {
@@ -2943,6 +2948,57 @@ static void tcp_chr_telnet_init(CharDriverState *chr)
         init, NULL);
 }
 
+
+static void tcp_chr_tls_handshake(Object *source,
+                                  Error *err,
+                                  gpointer user_data)
+{
+    CharDriverState *chr = user_data;
+    TCPCharDriver *s = chr->opaque;
+
+    if (err) {
+        tcp_chr_disconnect(chr);
+    } else {
+        if (s->do_telnetopt) {
+            tcp_chr_telnet_init(chr);
+        } else {
+            tcp_chr_connect(chr);
+        }
+    }
+}
+
+
+static void tcp_chr_tls_init(CharDriverState *chr)
+{
+    TCPCharDriver *s = chr->opaque;
+    QIOChannelTLS *tioc;
+    Error *err = NULL;
+
+    if (s->is_listen) {
+        tioc = qio_channel_tls_new_server(
+            s->ioc, s->tls_creds,
+            NULL, /* XXX Use an ACL */
+            &err);
+    } else {
+        tioc = qio_channel_tls_new_client(
+            s->ioc, s->tls_creds,
+            s->addr->u.inet->host,
+            &err);
+    }
+    if (tioc == NULL) {
+        error_free(err);
+        tcp_chr_disconnect(chr);
+    }
+    object_unref(OBJECT(s->ioc));
+    s->ioc = QIO_CHANNEL(tioc);
+
+    qio_channel_tls_handshake(tioc,
+                              tcp_chr_tls_handshake,
+                              chr,
+                              NULL);
+}
+
+
 static int tcp_chr_new_client(CharDriverState *chr, QIOChannelSocket *sioc)
 {
     TCPCharDriver *s = chr->opaque;
@@ -2952,6 +3008,8 @@ static int tcp_chr_new_client(CharDriverState *chr, QIOChannelSocket *sioc)
 
     s->ioc = QIO_CHANNEL(sioc);
     object_ref(OBJECT(sioc));
+    s->sioc = sioc;
+    object_ref(OBJECT(sioc));
 
     if (s->do_nodelay) {
         qio_channel_set_delay(s->ioc, false);
@@ -2961,10 +3019,14 @@ static int tcp_chr_new_client(CharDriverState *chr, QIOChannelSocket *sioc)
         s->listen_tag = 0;
     }
 
-    if (s->do_telnetopt) {
-        tcp_chr_telnet_init(chr);
+    if (s->tls_creds) {
+        tcp_chr_tls_init(chr);
     } else {
-        tcp_chr_connect(chr);
+        if (s->do_telnetopt) {
+            tcp_chr_telnet_init(chr);
+        } else {
+            tcp_chr_connect(chr);
+        }
     }
 
     return 0;
@@ -3033,6 +3095,9 @@ static void tcp_chr_close(CharDriverState *chr)
         }
         g_free(s->read_msgfds);
     }
+    if (s->tls_creds) {
+        object_unref(OBJECT(s->tls_creds));
+    }
     if (s->write_msgfds_num) {
         g_free(s->write_msgfds);
     }
@@ -3563,6 +3628,7 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend,
     const char *path = qemu_opt_get(opts, "path");
     const char *host = qemu_opt_get(opts, "host");
     const char *port = qemu_opt_get(opts, "port");
+    const char *tls_creds = qemu_opt_get(opts, "tls-creds");
     SocketAddress *addr;
 
     if (!path) {
@@ -3574,6 +3640,11 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend,
             error_setg(errp, "chardev: socket: no port given");
             return;
         }
+    } else {
+        if (tls_creds) {
+            error_setg(errp, "TLS can only be used over TCP socket");
+            return;
+        }
     }
 
     backend->u.socket = g_new0(ChardevSocket, 1);
@@ -3589,6 +3660,7 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend,
     backend->u.socket->wait = is_waitconnect;
     backend->u.socket->has_reconnect = true;
     backend->u.socket->reconnect = reconnect;
+    backend->u.socket->tls_creds = g_strdup(tls_creds);
 
     addr = g_new0(SocketAddress, 1);
     if (path) {
@@ -4016,6 +4088,9 @@ QemuOptsList qemu_chardev_opts = {
             .name = "telnet",
             .type = QEMU_OPT_BOOL,
         },{
+            .name = "tls-creds",
+            .type = QEMU_OPT_STRING,
+        },{
             .name = "width",
             .type = QEMU_OPT_NUMBER,
         },{
@@ -4231,6 +4306,39 @@ static CharDriverState *qmp_chardev_open_socket(const char *id,
     s->is_listen = is_listen;
     s->is_telnet = is_telnet;
     s->do_nodelay = do_nodelay;
+    if (sock->tls_creds) {
+        Object *creds;
+        creds = object_resolve_path_component(
+            object_get_objects_root(), sock->tls_creds);
+        if (!creds) {
+            error_setg(errp, "No TLS credentials with id '%s'",
+                       sock->tls_creds);
+            goto error;
+        }
+        s->tls_creds = (QCryptoTLSCreds *)
+            object_dynamic_cast(creds,
+                                TYPE_QCRYPTO_TLS_CREDS);
+        if (!s->tls_creds) {
+            error_setg(errp, "Object with id '%s' is not TLS credentials",
+                       sock->tls_creds);
+            goto error;
+        }
+        object_ref(OBJECT(s->tls_creds));
+        if (is_listen) {
+            if (s->tls_creds->endpoint != QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {
+                error_setg(errp, "%s",
+                           "Expected TLS credentials for server endpoint");
+                goto error;
+            }
+        } else {
+            if (s->tls_creds->endpoint != QCRYPTO_TLS_CREDS_ENDPOINT_CLIENT) {
+                error_setg(errp, "%s",
+                           "Expected TLS credentials for client endpoint");
+                goto error;
+            }
+        }
+    }
+
     qapi_copy_SocketAddress(&s->addr, sock->addr);
 
     chr->opaque = s;
@@ -4259,9 +4367,7 @@ static CharDriverState *qmp_chardev_open_socket(const char *id,
     if (s->reconnect_time) {
         socket_try_connect(chr);
     } else if (!qemu_chr_open_socket_fd(chr, errp)) {
-        g_free(s);
-        qemu_chr_free_common(chr);
-        return NULL;
+        goto error;
     }
 
     if (is_listen && is_waitconnect) {
@@ -4272,6 +4378,14 @@ static CharDriverState *qmp_chardev_open_socket(const char *id,
     }
 
     return chr;
+
+ error:
+    if (s->tls_creds) {
+        object_unref(OBJECT(s->tls_creds));
+    }
+    g_free(s);
+    qemu_chr_free_common(chr);
+    return NULL;
 }
 
 static CharDriverState *qmp_chardev_open_udp(const char *id,
diff --git a/qemu-options.hx b/qemu-options.hx
index b4763ba..f31a240 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2092,7 +2092,7 @@ DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
     "-chardev null,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
     "-chardev socket,id=id[,host=host],port=port[,to=to][,ipv4][,ipv6][,nodelay][,reconnect=seconds]\n"
     "         [,server][,nowait][,telnet][,reconnect=seconds][,mux=on|off]\n"
-    "         [,logfile=PATH][,logappend=on|off] (tcp)\n"
+    "         [,logfile=PATH][,logappend=on|off][,tls-creds=ID] (tcp)\n"
     "-chardev socket,id=id,path=path[,server][,nowait][,telnet][,reconnect=seconds]\n"
     "         [,mux=on|off][,logfile=PATH][,logappend=on|off] (unix)\n"
     "-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr]\n"
@@ -2172,7 +2172,7 @@ Further options to each backend are described below.
 A void device. This device will not emit any data, and will drop any data it
 receives. The null backend does not take any options.
 
-@item -chardev socket ,id=@var{id} [@var{TCP options} or @var{unix options}] [,server] [,nowait] [,telnet] [,reconnect=@var{seconds}]
+@item -chardev socket ,id=@var{id} [@var{TCP options} or @var{unix options}] [,server] [,nowait] [,telnet] [,reconnect=@var{seconds}] [,tls-creds=@var{id}]
 
 Create a two-way stream socket, which can be either a TCP or a unix socket. A
 unix socket will be created if @option{path} is specified. Behaviour is
@@ -2190,6 +2190,11 @@ escape sequences.
 the remote end goes away.  qemu will delay this many seconds and then attempt
 to reconnect.  Zero disables reconnecting, and is the default.
 
+@option{tls-creds} requests enablement of the TLS protocol for encryption,
+and specifies the id of the TLS credentials to use for the handshake. The
+credentials must be previously created with the @option{-object tls-creds}
+argument.
+
 TCP and unix socket options are given below:
 
 @table @option
-- 
2.5.0