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+@node vnc_security
+@section VNC security
+
+The VNC server capability provides access to the graphical console
+of the guest VM across the network. This has a number of security
+considerations depending on the deployment scenarios.
+
+@menu
+* vnc_sec_none::
+* vnc_sec_password::
+* vnc_sec_certificate::
+* vnc_sec_certificate_verify::
+* vnc_sec_certificate_pw::
+* vnc_sec_sasl::
+* vnc_sec_certificate_sasl::
+* vnc_setup_sasl::
+@end menu
+@node vnc_sec_none
+@subsection Without passwords
+
+The simplest VNC server setup does not include any form of authentication.
+For this setup it is recommended to restrict it to listen on a UNIX domain
+socket only. For example
+
+@example
+@value{qemu_system} [...OPTIONS...] -vnc unix:/home/joebloggs/.qemu-myvm-vnc
+@end example
+
+This ensures that only users on local box with read/write access to that
+path can access the VNC server. To securely access the VNC server from a
+remote machine, a combination of netcat+ssh can be used to provide a secure
+tunnel.
+
+@node vnc_sec_password
+@subsection With passwords
+
+The VNC protocol has limited support for password based authentication. Since
+the protocol limits passwords to 8 characters it should not be considered
+to provide high security. The password can be fairly easily brute-forced by
+a client making repeat connections. For this reason, a VNC server using password
+authentication should be restricted to only listen on the loopback interface
+or UNIX domain sockets. Password authentication is not supported when operating
+in FIPS 140-2 compliance mode as it requires the use of the DES cipher. Password
+authentication is requested with the @code{password} option, and then once QEMU
+is running the password is set with the monitor. Until the monitor is used to
+set the password all clients will be rejected.
+
+@example
+@value{qemu_system} [...OPTIONS...] -vnc :1,password -monitor stdio
+(qemu) change vnc password
+Password: ********
+(qemu)
+@end example
+
+@node vnc_sec_certificate
+@subsection With x509 certificates
+
+The QEMU VNC server also implements the VeNCrypt extension allowing use of
+TLS for encryption of the session, and x509 certificates for authentication.
+The use of x509 certificates is strongly recommended, because TLS on its
+own is susceptible to man-in-the-middle attacks. Basic x509 certificate
+support provides a secure session, but no authentication. This allows any
+client to connect, and provides an encrypted session.
+
+@example
+@value{qemu_system} [...OPTIONS...] \
+  -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=no \
+  -vnc :1,tls-creds=tls0 -monitor stdio
+@end example
+
+In the above example @code{/etc/pki/qemu} should contain at least three files,
+@code{ca-cert.pem}, @code{server-cert.pem} and @code{server-key.pem}. Unprivileged
+users will want to use a private directory, for example @code{$HOME/.pki/qemu}.
+NB the @code{server-key.pem} file should be protected with file mode 0600 to
+only be readable by the user owning it.
+
+@node vnc_sec_certificate_verify
+@subsection With x509 certificates and client verification
+
+Certificates can also provide a means to authenticate the client connecting.
+The server will request that the client provide a certificate, which it will
+then validate against the CA certificate. This is a good choice if deploying
+in an environment with a private internal certificate authority. It uses the
+same syntax as previously, but with @code{verify-peer} set to @code{yes}
+instead.
+
+@example
+@value{qemu_system} [...OPTIONS...] \
+  -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
+  -vnc :1,tls-creds=tls0 -monitor stdio
+@end example
+
+
+@node vnc_sec_certificate_pw
+@subsection With x509 certificates, client verification and passwords
+
+Finally, the previous method can be combined with VNC password authentication
+to provide two layers of authentication for clients.
+
+@example
+@value{qemu_system} [...OPTIONS...] \
+  -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
+  -vnc :1,tls-creds=tls0,password -monitor stdio
+(qemu) change vnc password
+Password: ********
+(qemu)
+@end example
+
+
+@node vnc_sec_sasl
+@subsection With SASL authentication
+
+The SASL authentication method is a VNC extension, that provides an
+easily extendable, pluggable authentication method. This allows for
+integration with a wide range of authentication mechanisms, such as
+PAM, GSSAPI/Kerberos, LDAP, SQL databases, one-time keys and more.
+The strength of the authentication depends on the exact mechanism
+configured. If the chosen mechanism also provides a SSF layer, then
+it will encrypt the datastream as well.
+
+Refer to the later docs on how to choose the exact SASL mechanism
+used for authentication, but assuming use of one supporting SSF,
+then QEMU can be launched with:
+
+@example
+@value{qemu_system} [...OPTIONS...] -vnc :1,sasl -monitor stdio
+@end example
+
+@node vnc_sec_certificate_sasl
+@subsection With x509 certificates and SASL authentication
+
+If the desired SASL authentication mechanism does not supported
+SSF layers, then it is strongly advised to run it in combination
+with TLS and x509 certificates. This provides securely encrypted
+data stream, avoiding risk of compromising of the security
+credentials. This can be enabled, by combining the 'sasl' option
+with the aforementioned TLS + x509 options:
+
+@example
+@value{qemu_system} [...OPTIONS...] \
+  -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
+  -vnc :1,tls-creds=tls0,sasl -monitor stdio
+@end example
+
+@node vnc_setup_sasl
+
+@subsection Configuring SASL mechanisms
+
+The following documentation assumes use of the Cyrus SASL implementation on a
+Linux host, but the principles should apply to any other SASL implementation
+or host. When SASL is enabled, the mechanism configuration will be loaded from
+system default SASL service config /etc/sasl2/qemu.conf. If running QEMU as an
+unprivileged user, an environment variable SASL_CONF_PATH can be used to make
+it search alternate locations for the service config file.
+
+If the TLS option is enabled for VNC, then it will provide session encryption,
+otherwise the SASL mechanism will have to provide encryption. In the latter
+case the list of possible plugins that can be used is drastically reduced. In
+fact only the GSSAPI SASL mechanism provides an acceptable level of security
+by modern standards. Previous versions of QEMU referred to the DIGEST-MD5
+mechanism, however, it has multiple serious flaws described in detail in
+RFC 6331 and thus should never be used any more. The SCRAM-SHA-1 mechanism
+provides a simple username/password auth facility similar to DIGEST-MD5, but
+does not support session encryption, so can only be used in combination with
+TLS.
+
+When not using TLS the recommended configuration is
+
+@example
+mech_list: gssapi
+keytab: /etc/qemu/krb5.tab
+@end example
+
+This says to use the 'GSSAPI' mechanism with the Kerberos v5 protocol, with
+the server principal stored in /etc/qemu/krb5.tab. For this to work the
+administrator of your KDC must generate a Kerberos principal for the server,
+with a name of 'qemu/somehost.example.com@@EXAMPLE.COM' replacing
+'somehost.example.com' with the fully qualified host name of the machine
+running QEMU, and 'EXAMPLE.COM' with the Kerberos Realm.
+
+When using TLS, if username+password authentication is desired, then a
+reasonable configuration is
+
+@example
+mech_list: scram-sha-1
+sasldb_path: /etc/qemu/passwd.db
+@end example
+
+The @code{saslpasswd2} program can be used to populate the @code{passwd.db}
+file with accounts.
+
+Other SASL configurations will be left as an exercise for the reader. Note that
+all mechanisms, except GSSAPI, should be combined with use of TLS to ensure a
+secure data channel.
+
+