[Qemu-devel] [PATCH v1 RFC 34/34] char: introduce support for TLS encrypted TCP chardev backend

[Daniel P. Berrange]

This integrates support for QIOChannelTLS object in the TCP
chardev backend. If the 'tls-cred=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. The 'acl' option will further enable the
creation of a 'char.$ID.tlspeername' ACL which will be used
to validate the client x509 certificate, if provided.

A complete invokation 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-cred=tls0,server \
      -device isa-serial,chardev=s0 \
      -object qcrypto-tls-cred,id=tls0,credtype=x509,\
        endpoint=server,dir=/home/berrange/security/qemutls,verify-peer=off

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 'NOMAL:+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 \
       --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-cred=tls0 \
      -device isa-serial,chardev=s0 \
      -object qcrypto-tls-cred,id=tls0,credtype=x509,\
        endpoint=client,dir=/home/berrange/security/qemutls

Signed-off-by: Daniel P. Berrange <address@hidden>
---
 qapi-schema.json |   2 +
 qemu-char.c      | 182 ++++++++++++++++++++++++++++++++++++++++++++++---------
 qemu-options.hx  |   9 ++-
 3 files changed, 161 insertions(+), 32 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json
index ac9594d..062a455 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2782,6 +2782,8 @@
 # Since: 1.4
 ##
 { 'type': 'ChardevSocket', 'data': { 'addr'       : 'SocketAddress',
+                                     '*tls-cred'  : 'str',
+                                     '*acl'       : 'str',
                                      '*server'    : 'bool',
                                      '*wait'      : 'bool',
                                      '*nodelay'   : 'bool',
diff --git a/qemu-char.c b/qemu-char.c
index 85fbbaf..da6f188 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -33,6 +33,8 @@
 #include "qapi-visit.h"
 #include "io/channel-socket.h"
 #include "io/channel-file.h"
+#include "io/channel-tls.h"
+#include "qemu/acl.h"
 
 #include <unistd.h>
 #include <fcntl.h>
@@ -2466,9 +2468,12 @@ static CharDriverState *qemu_chr_open_udp_fd(int fd)
 /* 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;
+    char *acl;
     int connected;
     int max_size;
     int do_telnetopt;
@@ -2699,6 +2704,8 @@ static void tcp_chr_disconnect(CharDriverState *chr)
             QIO_CHANNEL(s->listen_ioc), G_IO_IN, tcp_chr_accept, chr);
     }
     remove_fd_in_watch(chr);
+    object_unref(OBJECT(s->sioc));
+    s->sioc = NULL;
     object_unref(OBJECT(s->ioc));
     s->ioc = NULL;
     SocketAddress_to_str(chr->filename, CHR_MAX_FILENAME_SIZE,
@@ -2777,11 +2784,10 @@ static void tcp_chr_connect(void *opaque)
 {
     CharDriverState *chr = opaque;
     TCPCharDriver *s = chr->opaque;
-    QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(s->ioc);
 
     sockaddr_to_str(chr->filename, CHR_MAX_FILENAME_SIZE,
-                    &sioc->localAddr, sioc->localAddrLen,
-                    &sioc->remoteAddr, sioc->remoteAddrLen,
+                    &s->sioc->localAddr, s->sioc->localAddrLen,
+                    &s->sioc->remoteAddr, s->sioc->remoteAddrLen,
                     s->is_listen, s->is_telnet);
 
     s->connected = 1;
@@ -2869,29 +2875,85 @@ static void tcp_chr_telnet_init(CharDriverState *chr)
         init);
 }
 
-static int tcp_chr_new_client(CharDriverState *chr, QIOChannel *ioc)
+
+static void tcp_chr_tls_handshake(QIOTask *task,
+                                  gpointer user_data)
+{
+    CharDriverState *chr = user_data;
+    TCPCharDriver *s = chr->opaque;
+
+    if (task->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,
+            s->acl,
+            &err);
+    } else {
+        tioc = qio_channel_tls_new_client(
+            s->ioc, s->tls_creds,
+            s->addr->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;
     if (s->ioc != NULL) {
        return -1;
     }
 
-    s->ioc = ioc;
-    object_ref(OBJECT(ioc));
+    s->ioc = QIO_CHANNEL(sioc);
+    object_ref(OBJECT(s->ioc));
+    s->sioc = sioc;
+    object_ref(OBJECT(s->sioc));
 
     qio_channel_set_blocking(s->ioc, false);
     if (s->do_nodelay) {
-        qio_channel_socket_set_nodelay(QIO_CHANNEL_SOCKET(s->ioc), true);
+        qio_channel_socket_set_nodelay(s->sioc, true);
     }
     if (s->listen_tag) {
         g_source_remove(s->listen_tag);
         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;
@@ -2901,14 +2963,14 @@ static int tcp_chr_new_client(CharDriverState *chr, 
QIOChannel *ioc)
 static int tcp_chr_add_client(CharDriverState *chr, int fd)
 {
     int ret;
-    QIOChannel *ioc;
+    QIOChannelSocket *sioc;
 
-    ioc = QIO_CHANNEL(qio_channel_socket_new_fd(fd, NULL));
-    if (!ioc) {
+    sioc = qio_channel_socket_new_fd(fd, NULL);
+    if (!sioc) {
         return -1;
     }
-    ret = tcp_chr_new_client(chr, ioc);
-    object_unref(OBJECT(ioc));
+    ret = tcp_chr_new_client(chr, sioc);
+    object_unref(OBJECT(sioc));
     return ret;
 }
 
@@ -2917,17 +2979,16 @@ static gboolean tcp_chr_accept(QIOChannel *channel,
                                void *opaque)
 {
     CharDriverState *chr = opaque;
-    QIOChannel *ioc;
+    QIOChannelSocket *sioc;
 
-    ioc = QIO_CHANNEL(
-        qio_channel_socket_accept(QIO_CHANNEL_SOCKET(channel), NULL));
-    if (!ioc) {
+    sioc = qio_channel_socket_accept(QIO_CHANNEL_SOCKET(channel), NULL);
+    if (!sioc) {
         return TRUE;
     }
 
-    tcp_chr_new_client(chr, ioc);
+    tcp_chr_new_client(chr, sioc);
 
-    object_unref(OBJECT(ioc));
+    object_unref(OBJECT(sioc));
 
     return TRUE;
 }
@@ -2959,6 +3020,9 @@ 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);
     }
@@ -2979,13 +3043,13 @@ static void 
qemu_chr_finish_socket_connection(CharDriverState *chr, int fd)
         s->listen_tag = qio_channel_add_watch(
             QIO_CHANNEL(s->listen_ioc), G_IO_IN, tcp_chr_accept, chr);
     } else {
-        QIOChannel *ioc = QIO_CHANNEL(qio_channel_socket_new_fd(fd, NULL));
-        if (!ioc) {
+        QIOChannelSocket *sioc = qio_channel_socket_new_fd(fd, NULL);
+        if (!sioc) {
             close(fd);
             return;
         }
-        tcp_chr_new_client(chr, ioc);
-        object_unref(OBJECT(ioc));
+        tcp_chr_new_client(chr, sioc);
+        object_unref(OBJECT(sioc));
     }
 }
 
@@ -3450,6 +3514,8 @@ 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_cred = qemu_opt_get(opts, "tls-cred");
+    bool acl = qemu_opt_get_bool(opts, "acl", false);
     SocketAddress *addr;
 
     if (!path) {
@@ -3461,6 +3527,11 @@ static void qemu_chr_parse_socket(QemuOpts *opts, 
ChardevBackend *backend,
             error_setg(errp, "chardev: socket: no port given");
             return;
         }
+    } else {
+        if (tls_cred) {
+            error_setg(errp, "TLS can only be used over TCP socket");
+            return;
+        }
     }
 
     backend->socket = g_new0(ChardevSocket, 1);
@@ -3475,6 +3546,11 @@ static void qemu_chr_parse_socket(QemuOpts *opts, 
ChardevBackend *backend,
     backend->socket->wait = is_waitconnect;
     backend->socket->has_reconnect = true;
     backend->socket->reconnect = reconnect;
+    backend->socket->tls_cred = g_strdup(tls_cred);
+    if (acl) {
+        backend->socket->acl = g_strdup_printf("chr.%s.tlspeername",
+                                               qemu_opts_id(opts));
+    }
 
     addr = g_new0(SocketAddress, 1);
     if (path) {
@@ -3494,6 +3570,7 @@ static void qemu_chr_parse_socket(QemuOpts *opts, 
ChardevBackend *backend,
         addr->inet->ipv6 = qemu_opt_get_bool(opts, "ipv6", 0);
     }
     backend->socket->addr = addr;
+    return;
 }
 
 static void qemu_chr_parse_udp(QemuOpts *opts, ChardevBackend *backend,
@@ -3877,6 +3954,9 @@ QemuOptsList qemu_chardev_opts = {
             .name = "telnet",
             .type = QEMU_OPT_BOOL,
         },{
+            .name = "tls-cred",
+            .type = QEMU_OPT_STRING,
+        },{
             .name = "width",
             .type = QEMU_OPT_NUMBER,
         },{
@@ -4061,6 +4141,41 @@ static CharDriverState 
*qmp_chardev_open_socket(ChardevSocket *sock,
     s->is_listen = is_listen;
     s->is_telnet = is_telnet;
     s->do_nodelay = do_nodelay;
+    if (sock->tls_cred) {
+        Object *container;
+        container = container_get(object_get_root(), "/objects");
+        /* XXX this type cast causes an abort if the type is wrong.
+         * This is bad. We should check and set an error */
+        s->tls_creds = QCRYPTO_TLS_CREDS(
+            object_resolve_path_component(container,
+                                          sock->tls_cred));
+        if (!s->tls_creds) {
+            error_setg(errp, "No TLS credentials with id '%s'",
+                       sock->tls_cred);
+            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;
+            }
+        }
+
+        if (sock->acl) {
+            s->acl = g_strdup(sock->acl);
+
+            qemu_acl_init(s->acl);
+        }
+    }
+
     qapi_copy_SocketAddress(&s->addr, sock->addr);
 
     chr->opaque = s;
@@ -4090,10 +4205,7 @@ static CharDriverState 
*qmp_chardev_open_socket(ChardevSocket *sock,
     if (s->reconnect_time) {
         socket_try_connect(chr);
     } else if (!qemu_chr_open_socket_fd(chr, errp)) {
-        g_free(s);
-        g_free(chr->filename);
-        g_free(chr);
-        return NULL;
+        goto error;
     }
 
     if (is_listen && is_waitconnect) {
@@ -4104,6 +4216,16 @@ static CharDriverState 
*qmp_chardev_open_socket(ChardevSocket *sock,
     }
 
     return chr;
+
+ error:
+    if (s->tls_creds) {
+        object_unref(OBJECT(s->tls_creds));
+    }
+    g_free(s->acl);
+    g_free(s);
+    g_free(chr->filename);
+    g_free(chr);
+    return NULL;
 }
 
 static CharDriverState *qmp_chardev_open_udp(ChardevUdp *udp,
diff --git a/qemu-options.hx b/qemu-options.hx
index 44d9be2..0c764fc 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2009,7 +2009,7 @@ ETEXI
 DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
     "-chardev null,id=id[,mux=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] 
(tcp)\n"
+    "         
[,server][,nowait][,telnet][,reconnect=seconds][,mux=on|off][,tls-cred=ID][,acl]
 (tcp)\n"
     "-chardev 
socket,id=id,path=path[,server][,nowait][,telnet][,reconnect=seconds][,mux=on|off]
 (unix)\n"
     "-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr]\n"
     "         [,localport=localport][,ipv4][,ipv6][,mux=on|off]\n"
@@ -2082,7 +2082,7 @@ 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.
 
address@hidden -chardev socket ,address@hidden address@hidden options} or 
@var{unix options}] [,server] [,nowait] [,telnet] [,address@hidden
address@hidden -chardev socket ,address@hidden address@hidden options} or 
@var{unix options}] [,server] [,nowait] [,telnet] 
[,address@hidden,address@hidden
 
 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
@@ -2100,6 +2100,11 @@ 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.
 
address@hidden 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 
qcrypto-tls-cred}
+argument.
+
 TCP and unix socket options are given below:
 
 @table @option
-- 
2.1.0