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

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 05/21/2010 04:26 PM, Venkateswararao Jujjuri (JV) wrote:
> Add required infrastructure and modify create/open2 and mkdir per the new
> security model.
>
> Signed-off-by: Venkateswararao Jujjuri<jvrao@linux.vnet.ibm.com>
> ---
>   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 */
>    

Should use caps.

> +} 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>
>    

This is probably not something that can be included unconditionally.

Regards,

Anthony Liguori

>   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"
>