ssh: set a valid locale in the ssh-serve process

In the SSH client configuration, the setting 'SendEnv' could contain variables
like 'LANG', 'LC_ALL', and others. This causes these environment variables
(with their values at the client-side) to be set in the server. However, not
every locale setting valid in the client, is also valid on the server.

This could lead to the error:
    'locale.Error: unsupported locale setting'
when 'from mercurial import archival, merge as hg_merge, patch, ui' is
called.

Fix this problem by providing an ini setting 'ssh_locale' that the user can
set correctly, and which will be used to set LC_ALL and LANGUAGE in the
'kallithea-cli ssh-serve' process.

If an environment variable LC_ALL is set, it takes precedence over all other
'LC_xxx' variables, as well as over LANG. So, setting LC_ALL ensures that no
user setting of 'LC_xxx' or 'LANG' could influence ssh-serve badly.

There is one environment variable that might overrule LC_ALL, specifically
for showing messages: 'LANGUAGE'. GNU gettext lets it take precedence over
LC_ALL [1]:
    "GNU gettext gives preference to LANGUAGE over LC_ALL and LANG for the
    purpose of message handling"

So, also set LANGUAGE to the same value as we set LC_ALL to.


The principle of setting a specific locale in the server process to fix this
error, was first proposed by Dominik Ruf.

[1] https://www.gnu.org/software/gettext/manual/html_node/The-LANGUAGE-variable.html#The-LANGUAGE-variable

development.ini

@@ -238,6 +238,12 b' ssh_enabled = false'
 ## Path to be used in ssh_authorized_keys file to invoke kallithea-cli with ssh-serve.
 #kallithea_cli_path = /srv/kallithea/venv/bin/kallithea-cli
 
+## Locale to be used in the ssh-serve command.
+## This is needed because an SSH client may try to use its own locale
+## settings, which may not be available on the server.
+## See `locale -a` for valid values on this system.
+#ssh_locale = C.UTF-8
+
 ####################################
 ###        CELERY CONFIG        ####
 ####################################

kallithea/bin/kallithea_cli_ssh.py

@@ -45,6 +45,11 b' def ssh_serve(user_id, key_id):'
         sys.stderr.write("SSH access is disabled.\n")
         return sys.exit(1)
 
+    ssh_locale = kallithea.CONFIG.get('ssh_locale')
+    if ssh_locale:
+        os.environ['LC_ALL'] = ssh_locale # trumps everything, including LANG, except LANGUAGE
+        os.environ['LANGUAGE'] = ssh_locale # trumps LC_ALL for GNU gettext message handling
+
     ssh_original_command = os.environ.get('SSH_ORIGINAL_COMMAND', '')
     connection = re.search('^([\d\.]+)', os.environ.get('SSH_CONNECTION', ''))
     client_ip = connection.group(1) if connection else '0.0.0.0'

kallithea/lib/paster_commands/template.ini.mako

@@ -341,6 +341,12 b' ssh_authorized_keys = ${user_home_path}/'
 kallithea_cli_path = ${kallithea_cli_path}
 %endif
 
+<%text>## Locale to be used in the ssh-serve command.</%text>
+<%text>## This is needed because an SSH client may try to use its own locale</%text>
+<%text>## settings, which may not be available on the server.</%text>
+<%text>## See `locale -a` for valid values on this system.</%text>
+#ssh_locale = C.UTF-8
+
 <%text>####################################</%text>
 <%text>###        CELERY CONFIG        ####</%text>
 <%text>####################################</%text>