virtio-9p: Make infrastructure for the new security model.

This patch adds required infrastructure for the new security model.

- A new configure option for attr/xattr.
- if CONFIG_VIRTFS will be defined if both CONFIG_LINUX and CONFIG_ATTR defined.
- Defines routines related to both security models.

Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Makefile.objs

@@ -35,8 +35,8 @@ net-nested-$(CONFIG_SLIRP) += slirp.o
 net-nested-$(CONFIG_VDE) += vde.o
 net-obj-y += $(addprefix net/, $(net-nested-y))
 
-fsdev-nested-$(CONFIG_LINUX) = qemu-fsdev.o
-fsdev-obj-$(CONFIG_LINUX) += $(addprefix fsdev/, $(fsdev-nested-y))
+fsdev-nested-$(CONFIG_VIRTFS) = qemu-fsdev.o
+fsdev-obj-$(CONFIG_VIRTFS) += $(addprefix fsdev/, $(fsdev-nested-y))
 
 ######################################################################
 # libqemu_common.a: Target independent part of system emulation. The
@@ -233,7 +233,7 @@ sound-obj-$(CONFIG_CS4231A) += cs4231a.o
 adlib.o fmopl.o: QEMU_CFLAGS += -DBUILD_Y8950=0
 hw-obj-$(CONFIG_SOUND) += $(sound-obj-y)
 
-hw-obj-$(CONFIG_LINUX) += virtio-9p-debug.o virtio-9p-local.o
+hw-obj-$(CONFIG_VIRTFS) += virtio-9p-debug.o virtio-9p-local.o
 
 ######################################################################
 # libdis

Makefile.target

@@ -169,7 +169,7 @@ obj-y += virtio-blk.o virtio-balloon.o virtio-net.o virtio-serial-bus.o
 obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
 obj-y += vhost_net.o
 obj-$(CONFIG_VHOST_NET) += vhost.o
-obj-$(CONFIG_LINUX) += virtio-9p.o
+obj-$(CONFIG_VIRTFS) += virtio-9p.o
 obj-y += rwhandler.o
 obj-$(CONFIG_KVM) += kvm.o kvm-all.o
 obj-$(CONFIG_NO_KVM) += kvm-stub.o

configure

@@ -270,6 +270,7 @@ vnc_tls=""
 vnc_sasl=""
 xen=""
 linux_aio=""
+attr=""
 vhost_net=""
 
 gprof="no"
@@ -671,6 +672,10 @@ for opt do
   ;;
   --enable-linux-aio) linux_aio="yes"
   ;;
+  --disable-attr) attr="no"
+  ;;
+  --enable-attr) attr="yes"
+  ;;
   --enable-io-thread) io_thread="yes"
   ;;
   --disable-blobs) blobs="no"
@@ -858,6 +863,8 @@ echo "  --disable-vde            disable support for vde network"
 echo "  --enable-vde             enable support for vde network"
 echo "  --disable-linux-aio      disable Linux AIO support"
 echo "  --enable-linux-aio       enable Linux AIO support"
+echo "  --disable-attr           disables attr and xattr support"
+echo "  --enable-attr            enable attr and xattr support"
 echo "  --enable-io-thread       enable IO thread"
 echo "  --disable-blobs          disable installing provided firmware blobs"
 echo "  --kerneldir=PATH         look for kernel includes in PATH"
@@ -1645,6 +1652,27 @@ EOF
   fi
 fi
 
+##########################################
+# attr probe
+
+if test "$attr" != "no" ; then
+  cat > $TMPC <<EOF
+#include <stdio.h>
+#include <sys/types.h>
+#include <attr/xattr.h>
+int main(void) { getxattr(NULL, NULL, NULL, 0); setxattr(NULL, NULL, NULL, 0, 0); return 0; }
+EOF
+  if compile_prog "" "-lattr" ; then
+    attr=yes
+    LIBS="-lattr $LIBS"
+  else
+    if test "$attr" = "yes" ; then
+      feature_not_found "ATTR"
+    fi
+    attr=no
+  fi
+fi
+
 ##########################################
 # iovec probe
 cat > $TMPC <<EOF
@@ -2079,6 +2107,7 @@ echo "PIE user targets  $user_pie"
 echo "vde support       $vde"
 echo "IO thread         $io_thread"
 echo "Linux AIO support $linux_aio"
+echo "ATTR/XATTR support $attr"
 echo "Install blobs     $blobs"
 echo "KVM support       $kvm"
 echo "fdt support       $fdt"
@@ -2280,6 +2309,14 @@ fi
 if test "$linux_aio" = "yes" ; then
   echo "CONFIG_LINUX_AIO=y" >> $config_host_mak
 fi
+if test "$attr" = "yes" ; then
+  echo "CONFIG_ATTR=y" >> $config_host_mak
+fi
+if test "$linux" = "yes" ; then
+  if test "$attr" = "yes" ; then
+    echo "CONFIG_VIRTFS=y" >> $config_host_mak
+  fi
+fi
 if test "$blobs" = "yes" ; then
   echo "INSTALL_BLOBS=yes" >> $config_host_mak
 fi

hw/file-op-9p.h

@@ -18,13 +18,33 @@
 #include <utime.h>
 #include <sys/stat.h>
 #include <sys/uio.h>
+#include <sys/vfs.h>
+#define SM_LOCAL_MODE_BITS    0600
+#define SM_LOCAL_DIR_MODE_BITS    0700
+
+typedef enum
+{
+    SM_PASSTHROUGH = 1, /* uid/gid set on fileserver files */
+    SM_MAPPED,  /* uid/gid part of xattr */
+} SecModel;
+
+typedef struct FsCred
+{
+    uid_t   fc_uid;
+    gid_t   fc_gid;
+    mode_t  fc_mode;
+    dev_t   fc_rdev;
+} FsCred;
 
 typedef struct FsContext
 {
     char *fs_root;
+    SecModel fs_sm;
     uid_t uid;
 } FsContext;
 
+extern void cred_init(FsCred *);
+
 typedef struct FileOperations
 {
     int (*lstat)(FsContext *, const char *, struct stat *);

hw/virtio-9p-local.c

@@ -17,6 +17,7 @@
 #include <grp.h>
 #include <sys/socket.h>
 #include <sys/un.h>
+#include <attr/xattr.h>
 
 static const char *rpath(FsContext *ctx, const char *path)
 {
@@ -31,45 +32,37 @@ static int local_lstat(FsContext *ctx, const char *path, struct stat *stbuf)
     return lstat(rpath(ctx, path), stbuf);
 }
 
-static int local_setuid(FsContext *ctx, uid_t uid)
+static int local_set_xattr(const char *path, FsCred *credp)
 {
-    struct passwd *pw;
-    gid_t groups[33];
-    int ngroups;
-    static uid_t cur_uid = -1;
-
-    if (cur_uid == uid) {
-        return 0;
+    int err;
+    if (credp->fc_uid != -1) {
+        err = setxattr(path, "user.virtfs.uid", &credp->fc_uid, sizeof(uid_t),
+                0);
+        if (err) {
+            return err;
+        }
     }
-
-    if (setreuid(0, 0)) {
-        return -1;
+    if (credp->fc_gid != -1) {
+        err = setxattr(path, "user.virtfs.gid", &credp->fc_gid, sizeof(gid_t),
+                0);
+        if (err) {
+            return err;
+        }
     }
-
-    pw = getpwuid(uid);
-    if (pw == NULL) {
-        return -1;
+    if (credp->fc_mode != -1) {
+        err = setxattr(path, "user.virtfs.mode", &credp->fc_mode,
+                sizeof(mode_t), 0);
+        if (err) {
+            return err;
+        }
     }
-
-    ngroups = 33;
-    if (getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups) == -1) {
-        return -1;
+    if (credp->fc_rdev != -1) {
+        err = setxattr(path, "user.virtfs.rdev", &credp->fc_rdev,
+                sizeof(dev_t), 0);
+        if (err) {
+            return err;
+        }
     }
-
-    if (setgroups(ngroups, groups)) {
-        return -1;
-    }
-
-    if (setregid(-1, pw->pw_gid)) {
-        return -1;
-    }
-
-    if (setreuid(-1, uid)) {
-        return -1;
-    }
-
-    cur_uid = uid;
-
     return 0;
 }
 
@@ -183,6 +176,7 @@ static int local_open2(FsContext *ctx, const char *path, int flags, mode_t mode)
     return open(rpath(ctx, path), flags, mode);
 }
 
+
 static int local_symlink(FsContext *ctx, const char *oldpath,
                             const char *newpath)
 {
@@ -259,12 +253,13 @@ static int local_remove(FsContext *ctx, const char *path)
 
 static int local_fsync(FsContext *ctx, int fd)
 {
+    if (0) /* Just to supress the warning. Will be removed in next patch. */
+        (void)local_set_xattr(NULL, NULL);
     return fsync(fd);
 }
 
 FileOperations local_ops = {
     .lstat = local_lstat,
-    .setuid = local_setuid,
     .readlink = local_readlink,
     .close = local_close,
     .closedir = local_closedir,

hw/virtio-9p.c

@@ -67,16 +67,19 @@ static int omode_to_uflags(int8_t mode)
     return ret;
 }
 
+void cred_init(FsCred *credp)
+{
+    credp->fc_uid = -1;
+    credp->fc_gid = -1;
+    credp->fc_mode = -1;
+    credp->fc_rdev = -1;
+}
+
 static int v9fs_do_lstat(V9fsState *s, V9fsString *path, struct stat *stbuf)
 {
     return s->ops->lstat(&s->ctx, path->data, stbuf);
 }
 
-static int v9fs_do_setuid(V9fsState *s, uid_t uid)
-{
-    return s->ops->setuid(&s->ctx, uid);
-}
-
 static ssize_t v9fs_do_readlink(V9fsState *s, V9fsString *path, V9fsString *buf)
 {
     ssize_t len;
@@ -348,7 +351,6 @@ static V9fsFidState *lookup_fid(V9fsState *s, int32_t fid)
 
     for (f = s->fid_list; f; f = f->next) {
         if (f->fid == fid) {
-            v9fs_do_setuid(s, f->uid);
             return f;
         }
     }
@@ -2253,8 +2255,15 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
         exit(1);
     }
 
-    if (!strcmp(fse->security_model, "passthrough") &&
-                !strcmp(fse->security_model, "mapped")) {
+    if (!strcmp(fse->security_model, "passthrough")) {
+        /* Files on the Fileserver set to client user credentials */
+        s->ctx.fs_sm = SM_PASSTHROUGH;
+    } else if (!strcmp(fse->security_model, "mapped")) {
+        /* Files on the fileserver are set to QEMU credentials.
+         * Client user credentials are saved in extended attributes.
+         */
+        s->ctx.fs_sm = SM_MAPPED;
+    } else {
         /* user haven't specified a correct security option */
         fprintf(stderr, "one of the following must be specified as the"
                 "security option:\n\t security_model=passthrough \n\t "

hw/virtio-pci.c

@@ -641,7 +641,7 @@ static int virtio_balloon_init_pci(PCIDevice *pci_dev)
     return 0;
 }
 
-#ifdef CONFIG_LINUX
+#ifdef CONFIG_VIRTFS
 static int virtio_9p_init_pci(PCIDevice *pci_dev)
 {
     VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
@@ -712,7 +712,7 @@ static PCIDeviceInfo virtio_info[] = {
         },
         .qdev.reset = virtio_pci_reset,
     },{
-#ifdef CONFIG_LINUX
+#ifdef CONFIG_VIRTFS
         .qdev.name = "virtio-9p-pci",
         .qdev.size = sizeof(VirtIOPCIProxy),
         .init      = virtio_9p_init_pci,

vl.c

@@ -147,7 +147,7 @@ int main(int argc, char **argv)
 #include "qemu-config.h"
 #include "qemu-objects.h"
 #include "qemu-options.h"
-#ifdef CONFIG_LINUX
+#ifdef CONFIG_VIRTFS
 #include "fsdev/qemu-fsdev.h"
 #endif
 
@@ -1532,7 +1532,7 @@ static int chardev_init_func(QemuOpts *opts, void *opaque)
     return 0;
 }
 
-#ifdef CONFIG_LINUX
+#ifdef CONFIG_VIRTFS
 static int fsdev_init_func(QemuOpts *opts, void *opaque)
 {
     int ret;
@@ -2281,7 +2281,7 @@ int main(int argc, char **argv, char **envp)
                     exit(1);
                 }
                 break;
-#ifdef CONFIG_LINUX
+#ifdef CONFIG_VIRTFS
             case QEMU_OPTION_fsdev:
                 opts = qemu_opts_parse(&qemu_fsdev_opts, optarg, 1);
                 if (!opts) {
@@ -2705,7 +2705,7 @@ int main(int argc, char **argv, char **envp)
 
     if (qemu_opts_foreach(&qemu_chardev_opts, chardev_init_func, NULL, 1) != 0)
         exit(1);
-#ifdef CONFIG_LINUX
+#ifdef CONFIG_VIRTFS
     if (qemu_opts_foreach(&qemu_fsdev_opts, fsdev_init_func, NULL, 1) != 0) {
         exit(1);
     }