[Qemu-devel] [PATCH -V3 3/7] virtio-9p: modify create/open2 and mkdir for new security model.

[Venkateswararao Jujjuri (JV)]

Add required infrastructure and modify create/open2 and mkdir per the new
security model.

Signed-off-by: Venkateswararao Jujjuri <address@hidden>
---
 hw/file-op-9p.h      |   23 ++++++++-
 hw/virtio-9p-local.c |  139 +++++++++++++++++++++++++++++++++++---------------
 hw/virtio-9p.c       |   42 ++++++++++-----
 3 files changed, 148 insertions(+), 56 deletions(-)

diff --git a/hw/file-op-9p.h b/hw/file-op-9p.h
index 2934ff1..2cf7d27 100644
--- a/hw/file-op-9p.h
+++ b/hw/file-op-9p.h
@@ -19,13 +19,32 @@
 #include <sys/stat.h>
 #include <sys/uio.h>
 #include <sys/vfs.h>
+#define SM_LOCAL_MODE_BITS    0600
+
+typedef enum
+{
+    sm_none = 0,
+    sm_passthrough, /* 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 *);
@@ -43,7 +62,7 @@ typedef struct FileOperations
     int (*closedir)(FsContext *, DIR *);
     DIR *(*opendir)(FsContext *, const char *);
     int (*open)(FsContext *, const char *, int);
-    int (*open2)(FsContext *, const char *, int, mode_t);
+    int (*open2)(FsContext *, const char *, int, FsCred *);
     void (*rewinddir)(FsContext *, DIR *);
     off_t (*telldir)(FsContext *, DIR *);
     struct dirent *(*readdir)(FsContext *, DIR *);
@@ -51,7 +70,7 @@ typedef struct FileOperations
     ssize_t (*readv)(FsContext *, int, const struct iovec *, int);
     ssize_t (*writev)(FsContext *, int, const struct iovec *, int);
     off_t (*lseek)(FsContext *, int, off_t, int);
-    int (*mkdir)(FsContext *, const char *, mode_t);
+    int (*mkdir)(FsContext *, const char *, FsCred *);
     int (*fstat)(FsContext *, int, struct stat *);
     int (*rename)(FsContext *, const char *, const char *);
     int (*truncate)(FsContext *, const char *, off_t);
diff --git a/hw/virtio-9p-local.c b/hw/virtio-9p-local.c
index 78960ac..14fd3d9 100644
--- a/hw/virtio-9p-local.c
+++ b/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)
 {
@@ -31,47 +32,39 @@ 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;
-    }
-
-    if (setreuid(0, 0)) {
-        return -1;
-    }
-
-    pw = getpwuid(uid);
-    if (pw == NULL) {
-        return -1;
+    int err;
+    if (credp->fc_uid != -1) {
+        err = setxattr(path, "user.virtfs.uid", &credp->fc_uid, sizeof(uid_t),
+                0);
+        if (err) {
+            return err;
+        }
     }
-
-    ngroups = 33;
-    if (getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups) == -1) {
-        return -1;
+    if (credp->fc_gid != -1) {
+        err = setxattr(path, "user.virtfs.gid", &credp->fc_gid, sizeof(gid_t),
+                0);
+        if (err) {
+            return err;
+        }
     }
-
-    if (setgroups(ngroups, groups)) {
-        return -1;
-    }
-
-    if (setregid(-1, pw->pw_gid)) {
-        return -1;
+    if (credp->fc_mode != -1) {
+        err = setxattr(path, "user.virtfs.mode", &credp->fc_mode,
+                sizeof(mode_t), 0);
+        if (err) {
+            return err;
+        }
     }
-
-    if (setreuid(-1, uid)) {
-        return -1;
+    if (credp->fc_rdev != -1) {
+        err = setxattr(path, "user.virtfs.rdev", &credp->fc_rdev,
+                sizeof(dev_t), 0);
+        if (err) {
+            return err;
+        }
     }
-
-    cur_uid = uid;
-
-    return 0;
-}
+     return 0;
+ }
 
 static ssize_t local_readlink(FsContext *ctx, const char *path,
                                 char *buf, size_t bufsz)
@@ -168,9 +161,39 @@ static int local_mksock(FsContext *ctx2, const char *path)
     return 0;
 }
 
-static int local_mkdir(FsContext *ctx, const char *path, mode_t mode)
+static int local_mkdir(FsContext *fs_ctx, const char *path, FsCred *credp)
 {
-    return mkdir(rpath(ctx, path), mode);
+    int err = -1;
+    /* Determine the security model */
+    if (fs_ctx->fs_sm == sm_mapped) {
+        err = mkdir(rpath(fs_ctx, path), SM_LOCAL_MODE_BITS);
+        if (err == -1) {
+            return err;
+        }
+        credp->fc_mode = credp->fc_mode|S_IFDIR;
+        err = local_set_xattr(rpath(fs_ctx, path), credp);
+        if (err == -1) {
+            goto err_end;
+        }
+    } else if (fs_ctx->fs_sm == sm_passthrough) {
+        err = mkdir(rpath(fs_ctx, path), credp->fc_mode);
+        if (err == -1) {
+            return err;
+        }
+        err = chmod(rpath(fs_ctx, path), credp->fc_mode & 07777);
+        if (err == -1) {
+            goto err_end;
+        }
+        err = chown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gid);
+        if (err == -1) {
+            goto err_end;
+        }
+    }
+    return err;
+
+err_end:
+    remove(rpath(fs_ctx, path));
+    return err;
 }
 
 static int local_fstat(FsContext *ctx, int fd, struct stat *stbuf)
@@ -178,9 +201,44 @@ static int local_fstat(FsContext *ctx, int fd, struct stat 
*stbuf)
     return fstat(fd, stbuf);
 }
 
-static int local_open2(FsContext *ctx, const char *path, int flags, mode_t 
mode)
+static int local_open2(FsContext *fs_ctx, const char *path, int flags,
+        FsCred *credp)
 {
-    return open(rpath(ctx, path), flags, mode);
+    int fd = -1;
+    int err = -1;
+    /* Determine the security model */
+    if (fs_ctx->fs_sm == sm_mapped) {
+        int err;
+        fd = open(rpath(fs_ctx, path), flags, SM_LOCAL_MODE_BITS);
+        if (fd == -1) {
+            return fd;
+        }
+        credp->fc_mode = credp->fc_mode|S_IFREG;
+        /* Set cleint credentials in xattr */
+        err = local_set_xattr(rpath(fs_ctx, path), credp);
+        if (err == -1) {
+            goto err_end;
+        }
+    } else if (fs_ctx->fs_sm == sm_passthrough) {
+        fd = open(rpath(fs_ctx, path), flags, credp->fc_mode);
+        if (fd == -1) {
+            return fd;
+        }
+        err = chmod(rpath(fs_ctx, path), credp->fc_mode & 07777);
+        if (err == -1) {
+            goto err_end;
+        }
+        err = chown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gid);
+        if (err == -1) {
+            goto err_end;
+        }
+    }
+    return fd;
+
+err_end:
+    close(fd);
+    remove(rpath(fs_ctx, path));
+    return err;
 }
 
 static int local_symlink(FsContext *ctx, const char *oldpath,
@@ -269,7 +327,6 @@ static int local_statfs(FsContext *s, const char *path, 
struct statfs *stbuf)
 
 FileOperations local_ops = {
     .lstat = local_lstat,
-    .setuid = local_setuid,
     .readlink = local_readlink,
     .close = local_close,
     .closedir = local_closedir,
diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index fda3c4a..c8bd5da 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -67,14 +67,17 @@ static int omode_to_uflags(int8_t mode)
     return ret;
 }
 
-static int v9fs_do_lstat(V9fsState *s, V9fsString *path, struct stat *stbuf)
+void cred_init(FsCred *credp)
 {
-    return s->ops->lstat(&s->ctx, path->data, stbuf);
+    credp->fc_uid = -1;
+    credp->fc_gid = -1;
+    credp->fc_mode = -1;
+    credp->fc_rdev = -1;
 }
 
-static int v9fs_do_setuid(V9fsState *s, uid_t uid)
+static int v9fs_do_lstat(V9fsState *s, V9fsString *path, struct stat *stbuf)
 {
-    return s->ops->setuid(&s->ctx, uid);
+    return s->ops->lstat(&s->ctx, path->data, stbuf);
 }
 
 static ssize_t v9fs_do_readlink(V9fsState *s, V9fsString *path, V9fsString 
*buf)
@@ -164,9 +167,15 @@ static int v9fs_do_mksock(V9fsState *s, V9fsString *path)
     return s->ops->mksock(&s->ctx, path->data);
 }
 
-static int v9fs_do_mkdir(V9fsState *s, V9fsString *path, mode_t mode)
+static int v9fs_do_mkdir(V9fsState *s, V9fsCreateState *vs)
 {
-    return s->ops->mkdir(&s->ctx, path->data, mode);
+    FsCred cred;
+
+    cred_init(&cred);
+    cred.fc_uid = vs->fidp->uid;
+    cred.fc_mode = vs->perm & 0777;
+
+    return s->ops->mkdir(&s->ctx, vs->fullname.data, &cred);
 }
 
 static int v9fs_do_fstat(V9fsState *s, int fd, struct stat *stbuf)
@@ -174,9 +183,17 @@ static int v9fs_do_fstat(V9fsState *s, int fd, struct stat 
*stbuf)
     return s->ops->fstat(&s->ctx, fd, stbuf);
 }
 
-static int v9fs_do_open2(V9fsState *s, V9fsString *path, int flags, mode_t 
mode)
+static int v9fs_do_open2(V9fsState *s, V9fsCreateState *vs)
 {
-    return s->ops->open2(&s->ctx, path->data, flags, mode);
+    FsCred cred;
+    int flags;
+
+    cred_init(&cred);
+    cred.fc_uid = vs->fidp->uid;
+    cred.fc_mode = vs->perm & 0777;
+    flags = omode_to_uflags(vs->mode) | O_CREAT;
+
+    return s->ops->open2(&s->ctx, vs->fullname.data, flags, &cred);
 }
 
 static int v9fs_do_symlink(V9fsState *s, V9fsString *oldpath,
@@ -348,7 +365,6 @@ 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;
         }
     }
@@ -1762,7 +1778,7 @@ static void v9fs_create_post_lstat(V9fsState *s, 
V9fsCreateState *vs, int err)
     }
 
     if (vs->perm & P9_STAT_MODE_DIR) {
-        err = v9fs_do_mkdir(s, &vs->fullname, vs->perm & 0777);
+        err = v9fs_do_mkdir(s, vs);
         v9fs_create_post_mkdir(s, vs, err);
     } else if (vs->perm & P9_STAT_MODE_SYMLINK) {
         err = v9fs_do_symlink(s, &vs->extension, &vs->fullname);
@@ -1809,9 +1825,7 @@ static void v9fs_create_post_lstat(V9fsState *s, 
V9fsCreateState *vs, int err)
         err = v9fs_do_mksock(s, &vs->fullname);
         v9fs_create_post_mksock(s, vs, err);
     } else {
-        vs->fidp->fd = v9fs_do_open2(s, &vs->fullname,
-                                omode_to_uflags(vs->mode) | O_CREAT,
-                                vs->perm & 0777);
+        vs->fidp->fd = v9fs_do_open2(s, vs);
         v9fs_create_post_open2(s, vs, err);
     }
 
@@ -2322,10 +2336,12 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf 
*conf)
 
     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"
-- 
1.6.5.2