ui: introduce "password-secret" option for SPICE server

Currently when using SPICE the "password" option provides the password
in plain text on the command line. This is insecure as it is visible
to all processes on the host. As an alternative, the password can be
provided separately via the monitor.

This introduces a "password-secret" option which lets the password be
provided up front.

  $QEMU --object secret,id=vncsec0,file=passwd.txt \
        --spice port=5901,password-secret=vncsec0

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210311114343.439820-3-berrange@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

qemu-options.hx

@@ -1899,7 +1899,8 @@ DEF("spice", HAS_ARG, QEMU_OPTION_spice,
     "       [,tls-ciphers=<list>]\n"
     "       [,tls-channel=[main|display|cursor|inputs|record|playback]]\n"
     "       [,plaintext-channel=[main|display|cursor|inputs|record|playback]]\n"
-    "       [,sasl=on|off][,password=<secret>][,disable-ticketing=on|off]\n"
+    "       [,sasl=on|off][,disable-ticketing=on|off]\n"
+    "       [,password=<string>][,password-secret=<secret-id>]\n"
     "       [,image-compression=[auto_glz|auto_lz|quic|glz|lz|off]]\n"
     "       [,jpeg-wan-compression=[auto|never|always]]\n"
     "       [,zlib-glz-wan-compression=[auto|never|always]]\n"
@@ -1924,9 +1925,13 @@ SRST
     ``ipv4=on|off``; \ ``ipv6=on|off``; \ ``unix=on|off``
         Force using the specified IP version.
 
-    ``password=<secret>``
+    ``password=<string>``
         Set the password you need to authenticate.
 
+    ``password-secret=<secret-id>``
+        Set the ID of the ``secret`` object containing the password
+        you need to authenticate.
+
     ``sasl=on|off``
         Require that the client use SASL to authenticate with the spice.
         The exact choice of authentication method used is controlled

ui/spice-core.c

@@ -34,6 +34,7 @@
 #include "qapi/qapi-events-ui.h"
 #include "qemu/notify.h"
 #include "qemu/option.h"
+#include "crypto/secret_common.h"
 #include "migration/misc.h"
 #include "hw/pci/pci_bus.h"
 #include "ui/spice-display.h"
@@ -415,6 +416,9 @@ static QemuOptsList qemu_spice_opts = {
         },{
             .name = "password",
             .type = QEMU_OPT_STRING,
+        },{
+            .name = "password-secret",
+            .type = QEMU_OPT_STRING,
         },{
             .name = "disable-ticketing",
             .type = QEMU_OPT_BOOL,
@@ -636,7 +640,9 @@ void qemu_spice_display_init_done(void)
 static void qemu_spice_init(void)
 {
     QemuOpts *opts = QTAILQ_FIRST(&qemu_spice_opts.head);
-    const char *password, *str, *x509_dir, *addr,
+    char *password = NULL;
+    const char *passwordSecret;
+    const char *str, *x509_dir, *addr,
         *x509_key_password = NULL,
         *x509_dh_file = NULL,
         *tls_ciphers = NULL;
@@ -663,7 +669,26 @@ static void qemu_spice_init(void)
         error_report("spice tls-port is out of range");
         exit(1);
     }
-    password = qemu_opt_get(opts, "password");
+    passwordSecret = qemu_opt_get(opts, "password-secret");
+    if (passwordSecret) {
+        Error *local_err = NULL;
+        if (qemu_opt_get(opts, "password")) {
+            error_report("'password' option is mutually exclusive with "
+                         "'password-secret'");
+            exit(1);
+        }
+        password = qcrypto_secret_lookup_as_utf8(passwordSecret,
+                                                 &local_err);
+        if (!password) {
+            error_report_err(local_err);
+            exit(1);
+        }
+    } else {
+        str = qemu_opt_get(opts, "password");
+        if (str) {
+            password = g_strdup(str);
+        }
+    }
 
     if (tls_port) {
         x509_dir = qemu_opt_get(opts, "x509-dir");
@@ -809,6 +834,7 @@ static void qemu_spice_init(void)
     g_free(x509_key_file);
     g_free(x509_cert_file);
     g_free(x509_cacert_file);
+    g_free(password);
 
 #ifdef HAVE_SPICE_GL
     if (qemu_opt_get_bool(opts, "gl", 0)) {