Merge branch 'release'

common/lib/extract_tar.py

@@ -0,0 +1,63 @@
+"""
+Safe version of tarfile.extractall which does not extract any files that would
+be, or symlink to a file that is, outside of the directory extracted in.
+
+Adapted from:
+http://stackoverflow.com/questions/10060069/safely-extract-zip-or-tar-using-python
+"""
+from os.path import abspath, realpath, dirname, join as joinpath
+from django.core.exceptions import SuspiciousOperation
+import logging
+
+log = logging.getLogger(__name__) #pylint: disable=C0103
+
+def resolved(rpath):
+    """
+    Returns the canonical absolute path of `rpath`.
+    """
+    return realpath(abspath(rpath))
+
+def _is_bad_path(path, base):
+    """
+    Is (the canonical absolute path of) `path` outside `base`?
+    """
+    return not resolved(joinpath(base, path)).startswith(base)
+
+def _is_bad_link(info, base):
+    """
+    Does the file sym- ord hard-link to files outside `base`?
+    """
+    # Links are interpreted relative to the directory containing the link
+    tip = resolved(joinpath(base, dirname(info.name)))
+    return _is_bad_path(info.linkname, base=tip)
+
+def safemembers(members):
+    """
+    Check that all elements of a tar file are safe.
+    """
+
+    base = resolved(".")
+
+    for finfo in members:
+        if _is_bad_path(finfo.name, base):
+            log.debug("File %r is blocked (illegal path)", finfo.name)
+            raise SuspiciousOperation("Illegal path")
+        elif finfo.issym() and _is_bad_link(finfo, base):
+            log.debug( "File %r is blocked: Hard link to %r", finfo.name, finfo.linkname)
+            raise SuspiciousOperation("Hard link")
+        elif finfo.islnk() and _is_bad_link(finfo, base):
+            log.debug("File %r is blocked: Symlink to %r", finfo.name,
+                    finfo.linkname)
+            raise SuspiciousOperation("Symlink")
+        elif finfo.isdev():
+            log.debug("File %r is blocked: FIFO, device or character file",
+                    finfo.name)
+            raise SuspiciousOperation("Dev file")
+
+    return members
+
+def safetar_extractall(tarf, *args, **kwargs):
+    """
+    Safe version of `tarf.extractall()`.
+    """
+    return tarf.extractall(members=safemembers(tarf), *args, **kwargs)