char: introduce support for TLS encrypted TCP chardev backend

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>
Message-Id: <1453202071-10289-5-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/qemu-options.hx b/qemu-options.hx
index b4763ba226..f31a240bed 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