Platform: Add cross-platform removexattr bindings

Signed-off-by: alighazi288 <51366992+alighazi288@users.noreply.github.com>

Author: alighazi288

src/borg/platform/__init__.py

@@ -18,7 +18,7 @@
 platform_ug: ModuleType | None = None  # make mypy happy
 
 if is_linux:  # pragma: linux only
-    from .linux import listxattr, getxattr, setxattr
+    from .linux import listxattr, getxattr, setxattr, removexattr
     from .linux import acl_get, acl_set
     from .linux import set_flags, get_flags
     from .linux import SyncFile
@@ -27,7 +27,7 @@
     from .posix import getosusername
     from . import posix_ug as platform_ug
 elif is_freebsd:  # pragma: freebsd only
-    from .freebsd import listxattr, getxattr, setxattr
+    from .freebsd import listxattr, getxattr, setxattr, removexattr
     from .freebsd import acl_get, acl_set
     from .freebsd import set_flags
     from .base import get_flags
@@ -37,7 +37,7 @@
     from .posix import getosusername
     from . import posix_ug as platform_ug
 elif is_netbsd:  # pragma: netbsd only
-    from .netbsd import listxattr, getxattr, setxattr
+    from .netbsd import listxattr, getxattr, setxattr, removexattr
     from .base import acl_get, acl_set
     from .base import set_flags, get_flags
     from .base import SyncFile
@@ -46,7 +46,7 @@
     from .posix import getosusername
     from . import posix_ug as platform_ug
 elif is_darwin:  # pragma: darwin only
-    from .darwin import listxattr, getxattr, setxattr
+    from .darwin import listxattr, getxattr, setxattr, removexattr
     from .darwin import acl_get, acl_set
     from .darwin import is_darwin_feature_64_bit_inode, _get_birthtime_ns
     from .darwin import set_flags
@@ -59,7 +59,7 @@
     from . import posix_ug as platform_ug
 elif not is_win32:  # pragma: posix only
     # Generic code for all other POSIX OSes
-    from .base import listxattr, getxattr, setxattr
+    from .base import listxattr, getxattr, setxattr, removexattr
     from .base import acl_get, acl_set
     from .base import set_flags, get_flags
     from .base import SyncFile
@@ -69,7 +69,7 @@
     from . import posix_ug as platform_ug
 else:  # pragma: win32 only
     # Win32-specific stuff
-    from .base import listxattr, getxattr, setxattr
+    from .base import listxattr, getxattr, setxattr, removexattr
     from .base import acl_get, acl_set
     from .base import set_flags, get_flags
     from .windows import SyncFile

src/borg/platform/base.py

@@ -69,6 +69,17 @@ def setxattr(path, name, value, *, follow_symlinks=False):
     """
 
 
+def removexattr(path, name, *, follow_symlinks=False):
+    """
+    Remove an xattr from *path*.
+
+    *path* can either be a path (bytes) or an open file descriptor (int).
+    *name* is the name of the xattr to remove (bytes).
+    *follow_symlinks* indicates whether symlinks should be followed
+    and only applies when *path* is not an open file descriptor.
+    """
+
+
 def acl_get(path, item, st, numeric_ids=False, fd=None):
     """
     Save ACL entries.

src/borg/platform/darwin.pyx

@@ -6,7 +6,7 @@ from posix.time cimport timespec
 
 from . import posix_ug
 from ..helpers import safe_decode, safe_encode
-from .xattr import _listxattr_inner, _getxattr_inner, _setxattr_inner, split_string0
+from .xattr import _listxattr_inner, _getxattr_inner, _setxattr_inner, _removexattr_inner, split_string0
 
 
 
@@ -32,6 +32,9 @@ cdef extern from "sys/xattr.h":
     int c_setxattr "setxattr" (const char *path, const char *name, const void *value, size_t size, uint32_t pos, int flags)
     int c_fsetxattr "fsetxattr" (int filedes, const char *name, const void *value, size_t size, uint32_t pos, int flags)
 
+    int c_removexattr "removexattr" (const char *path, const char *name, int flags)
+    int c_fremovexattr "fremovexattr" (int filedes, const char *name, int flags)
+
     int XATTR_NOFOLLOW
 
 cdef int XATTR_NOFLAGS = 0x0000
@@ -100,6 +103,19 @@ def setxattr(path, name, value, *, follow_symlinks=False):
     _setxattr_inner(func, path, name, value)
 
 
+def removexattr(path, name, *, follow_symlinks=False):
+    def func(path, name):
+        if isinstance(path, int):
+            return c_fremovexattr(path, name, XATTR_NOFLAGS)
+        else:
+            if follow_symlinks:
+                return c_removexattr(path, name, XATTR_NOFLAGS)
+            else:
+                return c_removexattr(path, name, XATTR_NOFOLLOW)
+
+    _removexattr_inner(func, path, name)
+
+
 def _remove_numeric_id_if_possible(acl):
     """Replace the user/group field with the local uid/gid, if possible."""
     assert isinstance(acl, bytes)

src/borg/platform/freebsd.pyx

@@ -5,7 +5,7 @@ from libc cimport errno
 
 from .posix import posix_acl_use_stored_uid_gid
 from ..helpers import safe_encode, safe_decode
-from .xattr import _listxattr_inner, _getxattr_inner, _setxattr_inner, split_lstring
+from .xattr import _listxattr_inner, _getxattr_inner, _setxattr_inner, _removexattr_inner, split_lstring
 
 
 
@@ -22,6 +22,10 @@ cdef extern from "sys/extattr.h":
     int c_extattr_set_link "extattr_set_link" (const char *path, int attrnamespace, const char *attrname, const void *data, size_t nbytes)
     int c_extattr_set_fd "extattr_set_fd" (int fd, int attrnamespace, const char *attrname, const void *data, size_t nbytes)
 
+    int c_extattr_delete_file "extattr_delete_file" (const char *path, int attrnamespace, const char *attrname)
+    int c_extattr_delete_link "extattr_delete_link" (const char *path, int attrnamespace, const char *attrname)
+    int c_extattr_delete_fd "extattr_delete_fd" (int fd, int attrnamespace, const char *attrname)
+
     int EXTATTR_NAMESPACE_USER
 
 cdef extern from "sys/types.h":
@@ -124,6 +128,25 @@ def setxattr(path, name, value, *, follow_symlinks=False):
         _setxattr_inner(func, path, name, value)
 
 
+def removexattr(path, name, *, follow_symlinks=False):
+    def func(path, name):
+        if isinstance(path, int):
+            return c_extattr_delete_fd(path, ns_id, name)
+        else:
+            if follow_symlinks:
+                return c_extattr_delete_file(path, ns_id, name)
+            else:
+                return c_extattr_delete_link(path, ns_id, name)
+
+    ns, name = split_ns(name, b"user")
+    try:
+        ns_id = NS_ID_MAP[ns]  # this will raise a KeyError it the namespace is unsupported
+    except KeyError:
+        pass
+    else:
+        _removexattr_inner(func, path, name)
+
+
 cdef _get_acl(p, type, item, attribute, flags, fd=None):
     cdef acl_t acl
     cdef char *text

src/borg/platform/linux.pyx

@@ -8,7 +8,7 @@ from ..helpers import workarounds
 from ..helpers import safe_decode, safe_encode
 from .base import SyncFile as BaseSyncFile
 from .base import safe_fadvise
-from .xattr import _listxattr_inner, _getxattr_inner, _setxattr_inner, split_string0
+from .xattr import _listxattr_inner, _getxattr_inner, _setxattr_inner, _removexattr_inner, split_string0
 try:
     from .syncfilerange import sync_file_range, SYNC_FILE_RANGE_WRITE, SYNC_FILE_RANGE_WAIT_BEFORE, SYNC_FILE_RANGE_WAIT_AFTER
     SYNC_FILE_RANGE_LOADED = True
@@ -32,6 +32,10 @@ cdef extern from "sys/xattr.h":
     int c_lsetxattr "lsetxattr" (const char *path, const char *name, const void *value, size_t size, int flags)
     int c_fsetxattr "fsetxattr" (int filedes, const char *name, const void *value, size_t size, int flags)
 
+    int c_removexattr "removexattr" (const char *path, const char *name)
+    int c_lremovexattr "lremovexattr" (const char *path, const char *name)
+    int c_fremovexattr "fremovexattr" (int filedes, const char *name)
+
 cdef extern from "sys/types.h":
     int ACL_TYPE_ACCESS
     int ACL_TYPE_DEFAULT
@@ -121,6 +125,19 @@ def setxattr(path, name, value, *, follow_symlinks=False):
     _setxattr_inner(func, path, name, value)
 
 
+def removexattr(path, name, *, follow_symlinks=False):
+    def func(path, name):
+        if isinstance(path, int):
+            return c_fremovexattr(path, name)
+        else:
+            if follow_symlinks:
+                return c_removexattr(path, name)
+            else:
+                return c_lremovexattr(path, name)
+
+    _removexattr_inner(func, path, name)
+
+
 BSD_TO_LINUX_FLAGS = {
     stat.UF_NODUMP: FS_NODUMP_FL,
     stat.UF_IMMUTABLE: FS_IMMUTABLE_FL,

src/borg/platform/netbsd.pyx

@@ -1,4 +1,4 @@
-from .xattr import _listxattr_inner, _getxattr_inner, _setxattr_inner, split_lstring
+from .xattr import _listxattr_inner, _getxattr_inner, _setxattr_inner, _removexattr_inner, split_lstring
 
 
 
@@ -15,6 +15,10 @@ cdef extern from "sys/extattr.h":
     int c_extattr_set_link "extattr_set_link" (const char *path, int attrnamespace, const char *attrname, const void *data, size_t nbytes)
     int c_extattr_set_fd "extattr_set_fd" (int fd, int attrnamespace, const char *attrname, const void *data, size_t nbytes)
 
+    int c_extattr_delete_file "extattr_delete_file" (const char *path, int attrnamespace, const char *attrname)
+    int c_extattr_delete_link "extattr_delete_link" (const char *path, int attrnamespace, const char *attrname)
+    int c_extattr_delete_fd "extattr_delete_fd" (int fd, int attrnamespace, const char *attrname)
+
     int EXTATTR_NAMESPACE_USER
 
 
@@ -87,3 +91,22 @@ def setxattr(path, name, value, *, follow_symlinks=False):
         pass
     else:
         _setxattr_inner(func, path, name, value)
+
+
+def removexattr(path, name, *, follow_symlinks=False):
+    def func(path, name):
+        if isinstance(path, int):
+            return c_extattr_delete_fd(path, ns_id, name)
+        else:
+            if follow_symlinks:
+                return c_extattr_delete_file(path, ns_id, name)
+            else:
+                return c_extattr_delete_link(path, ns_id, name)
+
+    ns, name = split_ns(name, b"user")
+    try:
+        ns_id = NS_ID_MAP[ns]  # this will raise a KeyError it the namespace is unsupported
+    except KeyError:
+        pass
+    else:
+        _removexattr_inner(func, path, name)

src/borg/platform/xattr.py

@@ -87,3 +87,9 @@ def _setxattr_inner(func, path, name, value):
     assert isinstance(name, bytes)
     assert isinstance(value, bytes)
     _check(func(path, name, value, len(value)), path, detect_buffer_too_small=False)
+
+
+def _removexattr_inner(func, path, name):
+    assert isinstance(path, (bytes, int))
+    assert isinstance(name, bytes)
+    _check(func(path, name), path, detect_buffer_too_small=False)

src/borg/xattr.py

@@ -15,7 +15,7 @@
 
 logger = create_logger()
 
-from .platform import listxattr, getxattr, setxattr, ENOATTR
+from .platform import listxattr, getxattr, setxattr, removexattr, ENOATTR
 
 # If we are running with fakeroot on Linux, then use the xattr functions of fakeroot. This is needed by
 # the 'test_extract_capabilities' test, but also allows xattrs to work with fakeroot on Linux in normal use.
@@ -130,3 +130,37 @@ def set_all(path, xattrs, follow_symlinks=False):
                 err_str = str(e)
             logger.warning("When setting extended attribute %s: %s", k.decode(errors="replace"), err_str)
     return warning
+
+
+def clear_all(path, follow_symlinks=False):
+    """
+    Remove all (removable) extended attributes from *path*.
+
+    *path* can either be a path (str or bytes) or an open file descriptor (int).
+    *follow_symlinks* indicates whether symlinks should be followed
+    and only applies when *path* is not an open file descriptor.
+
+    This is best-effort: xattrs that cannot be removed (e.g. attributes in a
+    protected namespace such as "security.selinux", or on filesystems without
+    xattr support) are silently skipped rather than raising. It is used to bring
+    an existing file to a "fresh" state before re-applying archived metadata.
+    """
+    if isinstance(path, str):
+        path = os.fsencode(path)
+    try:
+        names = listxattr(path, follow_symlinks=follow_symlinks)
+    except OSError as e:
+        if e.errno in (errno.ENOTSUP, errno.EOPNOTSUPP, errno.EPERM):
+            # xattrs not supported on this filesystem (or not permitted to list): nothing to clear.
+            return
+        raise
+    for name in names:
+        try:
+            removexattr(path, name, follow_symlinks=follow_symlinks)
+        except OSError as e:
+            # ENOATTR: race, the xattr was already removed between list and remove.
+            # ENOTSUP/EOPNOTSUPP: filesystem does not support xattrs.
+            # EPERM/EACCES: protected namespace (e.g. "security.*") we are not allowed to drop.
+            if e.errno in (ENOATTR, errno.ENOTSUP, errno.EOPNOTSUPP, errno.EPERM, errno.EACCES):
+                continue
+            raise