Fix various issues with qubes-dom0-update

- fix unescaped dot in package_regex
- if any package fails verification, remove the whole directory, not
only that single package
- abort (and remove the whole directory) on any exception
- don't include file name in the error message, if it failed
verification

This, among other things, fix handling symlinks and directories sent by
potentially malicious UpdateVM. os.remove() can't remove non-empty
directories, so it would fail.
Fortunately metadata is created only after successful verification, so
dnf/yum wouldn't touch packages that failed verification and also
weren't removed. But make the code better handle such situations.

Reported-by: Hans Jerry Illikainen <hji@dyntopia.com>

dom0-updates/qubes-receive-updates

@@ -31,13 +31,12 @@ updates_dir = "/var/lib/qubes/updates"
 updates_rpm_dir = updates_dir + "/rpm"
 updates_repodata_dir = updates_dir + "/repodata"
 updates_error_file = updates_dir + "/errors"
-updates_error_file_handle = None
 
 comps_file = None
 if os.path.exists('/usr/share/qubes/Qubes-comps.xml'):
     comps_file = '/usr/share/qubes/Qubes-comps.xml'
 
-package_regex = re.compile(r"^[A-Za-z0-9._+-]{1,128}.rpm$")
+package_regex = re.compile(r"^[A-Za-z0-9._+-]{1,128}\.rpm$")
 # example valid outputs:
 #  .....rpm: rsa sha1 (md5) pgp md5 OK
 #  .....rpm: (sha1) dsa sha1 md5 gpg OK
@@ -49,18 +48,15 @@ package_regex = re.compile(r"^[A-Za-z0-9._+-]{1,128}.rpm$")
 gpg_ok_regex = re.compile(r": [a-z0-9() ]* (pgp|gpg|signatures) [a-z0-9 ]*OK$")
 
 
-def dom0updates_fatal(pkg, msg):
-    global updates_error_file_handle
+def dom0updates_fatal(msg):
     print(msg, file=sys.stderr)
-    if updates_error_file_handle is None:
-        updates_error_file_handle = open(updates_error_file, "a")
-    updates_error_file_handle.write(msg + "\n")
-    os.remove(pkg)
+    with open(updates_error_file, "a") as updates_error_file_handle:
+        updates_error_file_handle.write(msg + "\n")
+    shutil.rmtree(updates_rpm_dir)
+    exit(1)
 
 
 def handle_dom0updates(updatevm):
-    global updates_error_file_handle
-
     source = os.getenv("QREXEC_REMOTE_DOMAIN")
     if source != updatevm.name:
         print('Domain ' + str(source) + ' not allowed to send dom0 updates',
@@ -79,14 +75,14 @@ def handle_dom0updates(updatevm):
     os.mkdir(updates_rpm_dir)
     os.chown(updates_rpm_dir, -1, qubes_gid)
     os.chmod(updates_rpm_dir, 0o0775)
-    subprocess.check_call(["/usr/libexec/qubes/qfile-dom0-unpacker",
-        str(os.getuid()), updates_rpm_dir])
-    # Verify received files
-    for untrusted_f in os.listdir(updates_rpm_dir):
-        if not package_regex.match(untrusted_f):
-            dom0updates_fatal(updates_rpm_dir + '/' + untrusted_f,
-                'Domain ' + source + ' sent unexpected file: ' + untrusted_f)
-        else:
+    try:
+        subprocess.check_call(["/usr/libexec/qubes/qfile-dom0-unpacker",
+            str(os.getuid()), updates_rpm_dir])
+        # Verify received files
+        for untrusted_f in os.listdir(updates_rpm_dir):
+            if not package_regex.match(untrusted_f):
+                raise Exception(
+                    'Domain ' + source + ' sent unexpected file')
             f = untrusted_f
             assert '/' not in f
             assert '\0' not in f
@@ -94,19 +90,19 @@ def handle_dom0updates(updatevm):
 
             full_path = updates_rpm_dir + "/" + f
             if os.path.islink(full_path) or not os.path.isfile(full_path):
-                dom0updates_fatal(
-                    full_path, 'Domain ' + source + ' sent not regular file')
+                raise Exception(
+                    'Domain ' + source + ' sent not regular file')
             p = subprocess.Popen(["/bin/rpm", "-K", full_path],
                     stdout=subprocess.PIPE)
             output = p.communicate()[0].decode('ascii')
             if p.returncode != 0:
-                dom0updates_fatal(full_path,
+                raise Exception(
                     'Error while verifing %s signature: %s' % (f, output))
             if not gpg_ok_regex.search(output.strip()):
-                dom0updates_fatal(full_path,
+                raise Exception(
                     'Domain ' + source + ' sent not signed rpm: ' + f)
-    if updates_error_file_handle is not None:
-        updates_error_file_handle.close()
+    except Exception as e:
+        dom0updates_fatal(str(e))
     # After updates received - create repo metadata
     createrepo_cmd = ["/usr/bin/createrepo_c"]
     if comps_file:
@@ -130,4 +126,6 @@ def main():
         exit(1)
     handle_dom0updates(updatevm)
 
-main()
+
+if __name__ == '__main__':
+    main()