Support ACLs for controlling VNC access ("Daniel P. Berrange")

This patch introduces a generic internal API for access control lists
to be used by network servers in QEMU. It adds support for checking
these ACL in the VNC server, in two places. The first ACL is for the
SASL authentication mechanism, checking the SASL username. This ACL
is called 'vnc.username'. The second is for the TLS authentication
mechanism, when x509 client certificates are turned on, checking against
the Distinguished Name of the client. This ACL is called 'vnc.x509dname'

The internal API provides for an ACL with the following characteristics

 - A unique name, eg  vnc.username, and vnc.x509dname.
 - A default policy, allow or deny
 - An ordered series of match rules, with allow or deny policy

If none of the match rules apply, then the default policy is
used.

There is a monitor API to manipulate the ACLs, which I'll describe via
examples

  (qemu) acl show vnc.username
  policy: allow
  (qemu) acl policy vnc.username denya
  acl: policy set to 'deny'
  (qemu) acl allow vnc.username fred
  acl: added rule at position 1
  (qemu) acl allow vnc.username bob
  acl: added rule at position 2
  (qemu) acl allow vnc.username joe 1
  acl: added rule at position 1
  (qemu) acl show vnc.username
  policy: deny
  0: allow fred
  1: allow joe
  2: allow bob


  (qemu) acl show vnc.x509dname
  policy: allow
  (qemu) acl policy vnc.x509dname deny
  acl: policy set to 'deny'
  (qemu) acl allow vnc.x509dname C=GB,O=ACME,L=London,CN=*
  acl: added rule at position 1
  (qemu) acl allow vnc.x509dname C=GB,O=ACME,L=Boston,CN=bob
  acl: added rule at position 2
  (qemu) acl show vnc.x509dname
  policy: deny
  0: allow C=GB,O=ACME,L=London,CN=*
  1: allow C=GB,O=ACME,L=Boston,CN=bob

By default the VNC server will not use any ACLs, allowing access to
the server if the user successfully authenticates. To enable use of
ACLs to restrict user access, the ',acl' flag should be given when
starting QEMU. The initial ACL activated will be a 'deny all' policy
and should be customized using monitor commands.

eg enable SASL auth and ACLs

    qemu ....  -vnc localhost:1,sasl,acl

The next patch will provide a way to load a pre-defined ACL when
starting up


 Makefile        |    6 +
 b/acl.c         |  185 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 b/acl.h         |   74 ++++++++++++++++++++++
 configure       |   18 +++++
 monitor.c       |   95 ++++++++++++++++++++++++++++
 qemu-doc.texi   |   49 ++++++++++++++
 vnc-auth-sasl.c |   16 +++-
 vnc-auth-sasl.h |    7 ++
 vnc-tls.c       |   19 +++++
 vnc-tls.h       |    3 
 vnc.c           |   21 ++++++
 vnc.h           |    3 
 12 files changed, 491 insertions(+), 5 deletions(-)

   Signed-off-by: Daniel P. Berrange <[email protected]>
Signed-off-by: Anthony Liguori <[email protected]>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6726 c046a42c-6fe2-441c-8c8c-71466251a162

Makefile

@@ -144,7 +144,7 @@ endif
 ifdef CONFIG_CURSES
 OBJS+=curses.o
 endif
-OBJS+=vnc.o d3des.o
+OBJS+=vnc.o acl.o d3des.o
 ifdef CONFIG_VNC_TLS
 OBJS+=vnc-tls.o vnc-auth-vencrypt.o
 endif
@@ -174,9 +174,11 @@ sdl.o: sdl.c keymaps.h sdl_keysym.h
 
 sdl.o audio/sdlaudio.o: CFLAGS += $(SDL_CFLAGS)
 
+acl.o: acl.h acl.c
+
 vnc.h: vnc-tls.h vnc-auth-vencrypt.h vnc-auth-sasl.h keymaps.h
 
-vnc.o: vnc.c vnc.h vnc_keysym.h vnchextile.h d3des.c d3des.h
+vnc.o: vnc.c vnc.h vnc_keysym.h vnchextile.h d3des.c d3des.h acl.h
 
 vnc.o: CFLAGS += $(CONFIG_VNC_TLS_CFLAGS)
 

acl.c

@@ -0,0 +1,185 @@
+/*
+ * QEMU access control list management
+ *
+ * Copyright (C) 2009 Red Hat, Inc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+
+#include "qemu-common.h"
+#include "sysemu.h"
+#include "acl.h"
+
+#ifdef HAVE_FNMATCH_H
+#include <fnmatch.h>
+#endif
+
+
+static unsigned int nacls = 0;
+static qemu_acl **acls = NULL;
+
+
+
+qemu_acl *qemu_acl_find(const char *aclname)
+{
+    int i;
+    for (i = 0 ; i < nacls ; i++) {
+	if (strcmp(acls[i]->aclname, aclname) == 0)
+	    return acls[i];
+    }
+
+    return NULL;
+}
+
+qemu_acl *qemu_acl_init(const char *aclname)
+{
+    qemu_acl *acl;
+
+    acl = qemu_acl_find(aclname);
+    if (acl)
+	return acl;
+
+    acl = qemu_malloc(sizeof(*acl));
+    acl->aclname = qemu_strdup(aclname);
+    /* Deny by default, so there is no window of "open
+     * access" between QEMU starting, and the user setting
+     * up ACLs in the monitor */
+    acl->defaultDeny = 1;
+
+    acl->nentries = 0;
+    TAILQ_INIT(&acl->entries);
+
+    acls = qemu_realloc(acls, sizeof(*acls) * (nacls +1));
+    acls[nacls] = acl;
+    nacls++;
+
+    return acl;
+}
+
+int qemu_acl_party_is_allowed(qemu_acl *acl,
+			      const char *party)
+{
+    qemu_acl_entry *entry;
+
+    TAILQ_FOREACH(entry, &acl->entries, next) {
+#ifdef HAVE_FNMATCH_H
+	if (fnmatch(entry->match, party, 0) == 0)
+	    return entry->deny ? 0 : 1;
+#else
+	/* No fnmatch, so fallback to exact string matching
+	 * instead of allowing wildcards */
+	if (strcmp(entry->match, party) == 0)
+	    return entry->deny ? 0 : 1;
+#endif
+    }
+
+    return acl->defaultDeny ? 0 : 1;
+}
+
+
+void qemu_acl_reset(qemu_acl *acl)
+{
+    qemu_acl_entry *entry;
+
+    /* Put back to deny by default, so there is no window
+     * of "open access" while the user re-initializes the
+     * access control list */
+    acl->defaultDeny = 1;
+    TAILQ_FOREACH(entry, &acl->entries, next) {
+	TAILQ_REMOVE(&acl->entries, entry, next);
+	free(entry->match);
+	free(entry);
+    }
+    acl->nentries = 0;
+}
+
+
+int qemu_acl_append(qemu_acl *acl,
+		    int deny,
+		    const char *match)
+{
+    qemu_acl_entry *entry;
+
+    entry = qemu_malloc(sizeof(*entry));
+    entry->match = qemu_strdup(match);
+    entry->deny = deny;
+
+    TAILQ_INSERT_TAIL(&acl->entries, entry, next);
+    acl->nentries++;
+
+    return acl->nentries;
+}
+
+
+int qemu_acl_insert(qemu_acl *acl,
+		    int deny,
+		    const char *match,
+		    int index)
+{
+    qemu_acl_entry *entry;
+    qemu_acl_entry *tmp;
+    int i = 0;
+
+    if (index <= 0)
+	return -1;
+    if (index >= acl->nentries)
+	return qemu_acl_append(acl, deny, match);
+
+
+    entry = qemu_malloc(sizeof(*entry));
+    entry->match = qemu_strdup(match);
+    entry->deny = deny;
+
+    TAILQ_FOREACH(tmp, &acl->entries, next) {
+	i++;
+	if (i == index) {
+	    TAILQ_INSERT_BEFORE(tmp, entry, next);
+	    acl->nentries++;
+	    break;
+	}
+    }
+
+    return i;
+}
+
+int qemu_acl_remove(qemu_acl *acl,
+		    const char *match)
+{
+    qemu_acl_entry *entry;
+    int i = 0;
+
+    TAILQ_FOREACH(entry, &acl->entries, next) {
+	i++;
+	if (strcmp(entry->match, match) == 0) {
+	    TAILQ_REMOVE(&acl->entries, entry, next);
+	    return i;
+	}
+    }
+    return -1;
+}
+
+
+/*
+ * Local variables:
+ *  c-indent-level: 4
+ *  c-basic-offset: 4
+ *  tab-width: 8
+ * End:
+ */

acl.h

@@ -0,0 +1,74 @@
+/*
+ * QEMU access control list management
+ *
+ * Copyright (C) 2009 Red Hat, Inc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef __QEMU_ACL_H__
+#define __QEMU_ACL_H__
+
+#include "sys-queue.h"
+
+typedef struct qemu_acl_entry qemu_acl_entry;
+typedef struct qemu_acl qemu_acl;
+
+struct qemu_acl_entry {
+    char *match;
+    int deny;
+
+    TAILQ_ENTRY(qemu_acl_entry) next;
+};
+
+struct qemu_acl {
+    char *aclname;
+    unsigned int nentries;
+    TAILQ_HEAD(,qemu_acl_entry) entries;
+    int defaultDeny;
+};
+
+qemu_acl *qemu_acl_init(const char *aclname);
+
+qemu_acl *qemu_acl_find(const char *aclname);
+
+int qemu_acl_party_is_allowed(qemu_acl *acl,
+			      const char *party);
+
+void qemu_acl_reset(qemu_acl *acl);
+
+int qemu_acl_append(qemu_acl *acl,
+		    int deny,
+		    const char *match);
+int qemu_acl_insert(qemu_acl *acl,
+		    int deny,
+		    const char *match,
+		    int index);
+int qemu_acl_remove(qemu_acl *acl,
+		    const char *match);
+
+#endif /* __QEMU_ACL_H__ */
+
+/*
+ * Local variables:
+ *  c-indent-level: 4
+ *  c-basic-offset: 4
+ *  tab-width: 8
+ * End:
+ */

configure

@@ -861,6 +861,21 @@ EOF
     fi
 fi
 
+##########################################
+# fnmatch() probe, used for ACL routines
+fnmatch="no"
+cat > $TMPC << EOF
+#include <fnmatch.h>
+int main(void)
+{
+    fnmatch("foo", "foo", 0);
+    return 0;
+}
+EOF
+if $cc $ARCH_CFLAGS -o $TMPE $TMPC > /dev/null 2> /dev/null ; then
+   fnmatch="yes"
+fi
+
 ##########################################
 # vde libraries probe
 if test "$vde" = "yes" ; then
@@ -1421,6 +1436,9 @@ if test "$vnc_sasl" = "yes" ; then
   echo "CONFIG_VNC_SASL_LIBS=$vnc_sasl_libs" >> $config_mak
   echo "#define CONFIG_VNC_SASL 1" >> $config_h
 fi
+if test "$fnmatch" = "yes" ; then
+  echo "#define HAVE_FNMATCH_H 1" >> $config_h
+fi
 qemu_version=`head $source_path/VERSION`
 echo "VERSION=$qemu_version" >>$config_mak
 echo "#define QEMU_VERSION \"$qemu_version\"" >> $config_h