Re: [Qemu-devel] [PATCH -V4 3/7] virtio-9p: modify create/open2 and mkdir for new security model.

[Aneesh Kumar K.V]

On Wed, May 26, 2010 at 04:21:42PM -0700, Venkateswararao Jujjuri (JV) wrote:
> 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 |  149 
> ++++++++++++++++++++++++++++++++++++--------------
>  hw/virtio-9p.c       |   42 ++++++++++----
>  3 files changed, 158 insertions(+), 56 deletions(-)
> 
> diff --git a/hw/file-op-9p.h b/hw/file-op-9p.h
> index 2934ff1..73d59b2 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
> +#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 *);
> @@ -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..f6c2fe2 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 +161,44 @@ 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;
> +    int serrno = 0;
> +    /* Determine the security model */
> +    if (fs_ctx->fs_sm == SM_MAPPED) {
> +        err = mkdir(rpath(fs_ctx, path), SM_LOCAL_DIR_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) {
> +            serrno = errno;
> +            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) {
> +            serrno = errno;
> +            goto err_end;
> +        }
> +        err = chown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gid);
> +        if (err == -1) {
> +            serrno = errno;
> +            goto err_end;
> +        }
> +    }
> +    return err;
> +
> +err_end:
> +    remove(rpath(fs_ctx, path));
> +    errno = serrno;
> +    return err;
>  }
>  
>  static int local_fstat(FsContext *ctx, int fd, struct stat *stbuf)
> @@ -178,9 +206,49 @@ 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;
> +    int serrno = 0;
> +    /* 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) {
> +            serrno = errno;
> +            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) {
> +            serrno = errno;
> +            goto err_end;
> +        }
> +        err = chown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gid);
> +        if (err == -1) {
> +            serrno = errno;
> +            goto err_end;
> +        }
> +    }
> +    return fd;
> +
> +err_end:
> +    close(fd);
> +    remove(rpath(fs_ctx, path));
> +    errno = serrno;
> +    return err;
>  }
>  
>  static int local_symlink(FsContext *ctx, const char *oldpath,
> @@ -269,7 +337,6 @@ 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 6feaa53..ef870a3 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
> 
> 


Can you split this to two patch. 

1) Introduce just the security model and related xattr
2) Introduce the open2 section


Can we get something like the below

security_chmod(..)
{
    if (fs_ctx->fs_sm == SM_MAPPED) {

    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {

    } else
      return -1;
}

static int local_open2(FsContext *fs_ctx, const char *path, int flags,
        FsCred *credp)
{
        fd = open(rpath(fs_ctx, path), flags, credp->fc_mode);
        if (fd == -1) {
            return fd;
        }
        err = security_chmod(rpath(fs_ctx, path), credp);
        if (err == -1) {
            serrno = errno;
            goto err_end;
        }
        err = security_chown(rpath(fs_ctx, path), credp);
        if (err == -1) {
            serrno = errno;
            goto err_end;
        }
    return fd;

err_end:
    close(fd);
    remove(rpath(fs_ctx, path));
    errno = serrno;
    return err;


}



So you basically introduce security_chmod ( I guess we need a better name) in 
patch 1
That also tells us better how is chmod different between two security models.

-aneesh