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// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2012- OpenVPN Inc.
//
// SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
#ifndef OPENVPN_CLIENT_OPTFILT_H
#define OPENVPN_CLIENT_OPTFILT_H
#include <vector>
#include <openvpn/common/options.hpp>
#include <openvpn/common/numeric_util.hpp>
#include <openvpn/common/string.hpp>
#include <openvpn/client/dns.hpp>
// Options filters, consumes the route-nopull and pull-filter client options
namespace openvpn {
class PushedOptionsFilter : public OptionList::FilterBase
{
public:
PushedOptionsFilter(const OptionList &opt)
: route_nopull_(opt.exists("route-nopull"))
{
if (!opt.exists("pull-filter"))
return;
for (auto i : opt.get_index("pull-filter"))
{
FilterAction action = None;
auto &o = opt[i];
o.exact_args(3);
o.touch();
const auto &action_str = o.get(1, -1);
if (action_str == "accept")
action = Accept;
else if (action_str == "ignore")
action = Ignore;
else if (action_str == "reject")
action = Reject;
else
throw option_error(ERR_INVALID_OPTION_VAL, "invalid pull-filter action: " + action_str);
Option match = OptionList::parse_option_from_line(o.get(2, -1), nullptr);
pull_filter_list_.push_back({action, match});
}
}
bool filter(const Option &opt) override
{
return filter_(opt) == Accept ? true : false;
}
private:
enum FilterAction
{
None,
Accept,
Ignore,
Reject
};
struct PullFilter
{
FilterAction action;
Option match;
};
FilterAction filter_(const Option &opt)
{
static_filter_(opt);
FilterAction action = pull_filter_(opt);
if (action == None)
{
if (route_nopull_)
action = route_nopull_filter_(opt);
else
action = Accept;
}
return action;
}
void static_filter_(const Option &o)
{
// Reject pushed DNS servers with priority < 0
if (o.size() >= 3
&& o.ref(0) == "dns"
&& o.ref(1) == "server"
&& DnsOptionsParser::parse_priority(o.ref(2)) < 0)
{
throw option_error(ERR_INVALID_CONFIG, o.escape(false));
}
}
// Return an action if a pull-filter directive matches the pushed option
FilterAction pull_filter_(const Option &pushed)
{
for (const auto &pull_filter : pull_filter_list_)
{
if (!pull_filter_matches_(pushed, pull_filter.match))
continue;
if (pull_filter.action != Accept)
{
OPENVPN_LOG((pull_filter.action == Ignore ? "Ignored" : "Rejected")
<< " due to pull-filter: "
<< pushed.render(Option::RENDER_TRUNC_64 | Option::RENDER_BRACKET));
if (pull_filter.action == Reject)
throw Option::RejectedException(pushed.escape(false));
}
return pull_filter.action;
}
return None;
}
bool pull_filter_matches_(const Option &pushed, const Option &match)
{
if (pushed.size() < match.size())
return false;
if (!is_safe_conversion<int>(match.size() - 1))
return false;
int i = static_cast<int>(match.size() - 1);
if (!string::starts_with(pushed.get(i, -1), match.get(i, -1)))
return false;
while (--i >= 0)
{
if (pushed.get(i, -1) != match.get(i, -1))
return false;
}
return true;
}
// return action if pushed option should be ignored due to route-nopull directive.
FilterAction route_nopull_filter_(const Option &opt)
{
FilterAction action = Accept;
if (opt.size() >= 1)
{
const std::string &directive = opt.ref(0);
if (directive.length() >= 1)
{
switch (directive[0])
{
case 'b':
if (directive == "block-ipv6")
{
action = Ignore;
}
break;
case 'c':
if (directive == "client-nat")
{
action = Ignore;
}
break;
case 'd':
if (directive == "dhcp-option"
|| directive == "dhcp-renew"
|| directive == "dhcp-pre-release" || directive == "dhcp-release")
{
action = Ignore;
}
break;
case 'i':
if (directive == "ip-win32")
{
action = Ignore;
}
break;
case 'r':
if (directive == "route"
|| directive == "route-ipv6"
|| directive == "route-metric"
|| directive == "redirect-gateway"
|| directive == "redirect-private"
|| directive == "register-dns"
|| directive == "route-delay"
|| directive == "route-method")
{
action = Ignore;
}
break;
case 't':
if (directive == "tap-sleep")
{
action = Ignore;
}
break;
}
if (action == Ignore)
{
OPENVPN_LOG("Ignored due to route-nopull: "
<< opt.render(Option::RENDER_TRUNC_64 | Option::RENDER_BRACKET));
}
}
}
return action;
}
bool route_nopull_;
std::vector<PullFilter> pull_filter_list_;
};
} // namespace openvpn
#endif
|
