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diff --git a/Changes.rst b/Changes.rst new file mode 100644 index 0000000..7ffd89e --- /dev/null +++ b/Changes.rst @@ -0,0 +1,304 @@ +Version 2.4.0 +============= + + +New features +------------ +Seamless client IP/port floating + Added new packet format P_DATA_V2, which includes peer-id. If both the + server and client support it, the client sends all data packets in + the new format. When a data packet arrives, the server identifies peer + by peer-id. If peer's ip/port has changed, server assumes that + client has floated, verifies HMAC and updates ip/port in internal structs. + This allows the connection to be immediatly restored, instead of requiring + a TLS handshake before the server accepts packets from the new client + ip/port. + +Data channel cipher negotiation + Data channel ciphers (``--cipher``) are now by default negotiated. If a + client advertises support for Negotiable Crypto Parameters (NCP), the + server will choose a cipher (by default AES-256-GCM) for the data channel, + and tell the client to use that cipher. Data channel cipher negotiation + can be controlled using ``--ncp-ciphers`` and ``--ncp-disable``. + + A more limited version also works in client-to-server and server-to-client + scenarios where one of the end points uses a v2.4 client or server and the + other side uses an older version. In such scenarios the v2.4 side will + change to the ``--cipher`` set by the remote side, if permitted by by + ``--ncp-ciphers``. For example, a v2.4 client with ``--cipher BF-CBC`` + and ``ncp-ciphers AES-256-GCM:AES-256-CBC`` can connect to both a v2.3 + server with ``cipher BF-CBC`` as well as a server with + ``cipher AES-256-CBC`` in its config. The other way around, a v2.3 client + with either ``cipher BF-CBC`` or ``cipher AES-256-CBC`` can connect to a + v2.4 server with e.g. ``cipher BF-CBC`` and + ``ncp-ciphers AES-256-GCM:AES-256-CBC`` in its config. For this to work + it requires that OpenVPN was built without disabling OCC support. + +AEAD (GCM) data channel cipher support + The data channel now supports AEAD ciphers (currently only GCM). The AEAD + packet format has a smaller crypto overhead than the CBC packet format, + (e.g. 20 bytes per packet for AES-128-GCM instead of 36 bytes per packet + for AES-128-CBC + HMAC-SHA1). + +ECDH key exchange + The TLS control channel now supports for elliptic curve diffie-hellmann + key exchange (ECDH). + +Dualstack round-robin DNS client connect + Instead of only using the first address of each ``--remote`` OpenVPN + will now try all addresses (IPv6 and IPv4) of a ``--remote`` entry. + +Support for providing IPv6 DNS servers + A new DHCP sub-option ``DNS6`` is added alongside with the already existing + ``DNS`` sub-option. This is used to provide DNS resolvers available over + IPv6. This may be pushed to clients where `` --up`` scripts and ``--plugin`` + can act upon it through the ``foreign_option_<n>`` environment variables. + + Support for the Windows client picking up this new sub-option is added, + however IPv6 DNS resolvers need to be configured via ``netsh`` which requires + administrator privileges unless the new interactive services on Windows is + being used. If the interactive service is used, this service will execute + ``netsh`` in the background with the proper privileges. + +New improved Windows Background service + The new OpenVPNService is based on openvpnserv2, a complete rewrite of the OpenVPN + service wrapper. It is intended for launching OpenVPN instances that should be + up at all times, instead of being manually launched by a user. OpenVPNService is + able to restart individual OpenVPN processes if they crash, and it also works + properly on recent Windows versions. OpenVPNServiceLegacy tends to work poorly, + if at all, on newer Windows versions (8+) and its use is not recommended. + +New interactive Windows service + The installer starts OpenVPNServiceInteractive automatically and configures + it to start at system startup. + + The interactive Windows service allows unprivileged users to start + OpenVPN connections in the global config directory (usually + C:\\Program Files\\OpenVPN\\config) using OpenVPN GUI without any + extra configuration. + + Users who belong to the built-in Administrator group or to the + local "OpenVPN Administrator" group can also store configuration + files under %USERPROFILE%\\OpenVPN\\config for use with the + interactive service. + +redirect-gateway ipv6 + OpenVPN has now feature parity between IPv4 and IPv6 for redirect + gateway including the handling of overlapping IPv6 routes with + IPv6 remote VPN server address. + +LZ4 Compression and pushable compression + Additionally to LZO compression OpenVPN now also supports LZ4 compression. + Compression options are now pushable from the server. + +Filter pulled options client-side: pull-filter + New option to explicitly allow or reject options pushed by the server. + May be used multiple times and is applied in the order specified. + +Per-client remove push options: push-remove + New option to remove options on a per-client basis from the "push" list + (more fine-grained than ``--push-reset``). + +Http proxy password inside config file + Http proxy passwords can be specified with the inline file option + ``<http-proxy-user-pass>`` .. ``</http-proxy-user-pass>`` + +Windows version detection + Windows version is detected, logged and possibly signalled to server + (IV_PLAT_VER=<nn> if ``--push-peer-info`` is set on client). + +Authentication tokens + In situations where it is not suitable to save user passwords on the client, + OpenVPN has support for pushing a --auth-token since v2.3. This option is + pushed from the server to the client with a token value to be used instead + of the users password. For this to work, the authentication plug-in would + need to implement this support as well. In OpenVPN 2.4 --auth-gen-token + is introduced, which will allow the OpenVPN server to generate a random + token and push it to the client without any changes to the authentication + modules. When the clients need to re-authenticate the OpenVPN server will + do the authentication internally, instead of sending the re-authentication + request to the authentication module . This feature is especially + useful in configurations which use One Time Password (OTP) authentication + schemes, as this allows the tunnel keys to be renegotiated regularly without + any need to supply new OTP codes. + +keying-material-exporter + Keying Material Exporter [RFC-5705] allow additional keying material to be + derived from existing TLS channel. + +Mac OS X Keychain management client + Added contrib/keychain-mcd which allows to use Mac OS X keychain + certificates with OpenVPN. + +Android platform support + Support for running on Android using Android's VPNService API has been added. + See doc/android.txt for more details. This support is primarily used in + the OpenVPN for Android app (https://github.com/schwabe/ics-openvpn) + +AIX platform support + AIX platform support has been added. The support only includes tap + devices since AIX does not provide tun interface. + +Control channel encryption (``--tls-crypt``) + Use a pre-shared static key (like the ``--tls-auth`` key) to encrypt control + channel packets. Provides more privacy, some obfuscation and poor-man's + post-quantum security. + +Asynchronous push reply + Plug-ins providing support for deferred authentication can benefit from a more + responsive authentication where the server sends PUSH_REPLY immediately once + the authentication result is ready, instead of waiting for the the client to + to send PUSH_REQUEST once more. This requires OpenVPN to be built with + ``./configure --enable-async-push``. This is a compile-time only switch. + + +Deprecated features +------------------- +- ``--key-method 1`` is deprecated in 2.4 and will be removed in 2.5. Migrate + away from ``--key-method 1`` as soon as possible. The recommended approach + is to remove the ``--key-method`` option from the configuration files, OpenVPN + will then use ``--key-method 2`` by default. Note that this requires changing + the option in both the client and server side configs. + +- CRLs are now handled by the crypto library (OpenSSL or mbed TLS), instead of + inside OpenVPN itself. The crypto library implementations are more strict + than the OpenVPN implementation was. This might reject peer certificates + that would previously be accepted. If this occurs, OpenVPN will log the + crypto library's error description. + +- ``--tls-remote`` is removed in 2.4, as indicated in the 2.3 man-pages. Similar + functionality is provided via ``--verify-x509-name``, which does the same job in + a better way. + +- ``--compat-names`` and ``--no-name-remapping`` were deprecated in 2.3 and will + be removed in 2.5. All scripts and plug-ins depending on the old non-standard + X.509 subject formatting must be updated to the standardized formatting. See + the man page for more information. + +- ``--no-iv`` is deprecated in 2.4 and will be removed in 2.5. + +User-visible Changes +-------------------- +- When using ciphers with cipher blocks less than 128-bits, + OpenVPN will complain loudly if the configuration uses ciphers considered + weak, such as the SWEET32 attack vector. In such scenarios, OpenVPN will by + default renegotiate for each 64MB of transported data (``--reneg-bytes``). + This renegotiation can be disabled, but is HIGHLY DISCOURAGED. + +- For certificate DNs with duplicate fields, e.g. "OU=one,OU=two", both fields + are now exported to the environment, where each second and later occurrence + of a field get _$N appended to it's field name, starting at N=1. For the + example above, that would result in e.g. X509_0_OU=one, X509_0_OU_1=two. + Note that this breaks setups that rely on the fact that OpenVPN would + previously (incorrectly) only export the last occurence of a field. + +- ``proto udp`` and ``proto tcp`` now use both IPv4 and IPv6. The new + options ``proto udp4`` and ``proto tcp4`` use IPv4 only. + +- ``--sndbuf`` and ``--recvbuf`` default now to OS defaults instead of 64k + +- OpenVPN exits with an error if an option has extra parameters; + previously they were silently ignored + +- ``--tls-auth`` always requires OpenVPN static key files and will no + longer work with free form files + +- ``--proto udp6/tcp6`` in server mode will now try to always listen to + both IPv4 and IPv6 on platforms that allow it. Use ``--bind ipv6only`` + to explicitly listen only on IPv6. + +- Removed ``--enable-password-save`` from configure. This option is now + always enabled. + +- Stricter default TLS cipher list (override with ``--tls-cipher``), that now + also disables: + + * Non-ephemeral key exchange using static (EC)DH keys + * DSS private keys + +- mbed TLS builds: changed the tls_digest_N values exported to the script + environment to be equal to the ones exported by OpenSSL builds, namely + the certificate fingerprint (was the hash of the 'to be signed' data). + +- mbed TLS builds: minimum RSA key size is now 2048 bits. Shorter keys will + not be accepted, both local and from the peer. + +- ``--connect-timeout`` now specifies the timeout until the first TLS packet + is received (identical to ``--server-poll-timeout``) and this timeout now + includes the removed socks proxy timeout and http proxy timeout. + + In ``--static`` mode ``connect-timeout`` specifies the timeout for TCP and + proxy connection establishment + +- ``--connect-retry-max`` now specifies the maximum number of unsuccessful + attempts of each remote/connection entry before exiting. + +- ``--http-proxy-timeout`` and the static non-changeable socks timeout (5s) + have been folded into a "unified" ``--connect-timeout`` which covers all + steps needed to connect to the server, up to the start of the TLS exchange. + The default value has been raised to 120s, to handle slow http/socks + proxies graciously. The old "fail TCP fast" behaviour can be achieved by + adding "``--connect-timeout 10``" to the client config. + +- ``--http-proxy-retry`` and ``--sock-proxy-retry`` have been removed. Proxy connections + will now behave like regular connection entries and generate a USR1 on failure. + +- ``--connect-retry`` gets an optional second argument that specifies the maximum + time in seconds to wait between reconnection attempts when an exponential + backoff is triggered due to repeated retries. Default = 300 seconds. + +- Data channel cipher negotiation (see New features section) can override + ciphers configured in the config file. Use ``--ncp-disable`` if you do not want + this behavior. + +- All tun devices on all platforms are always considered to be IPv6 + capable. The ``--tun-ipv6`` option is ignored (behaves like it is always + on). + +- On the client side recursively routed packets, which have the same destination + as the VPN server, are dropped. This can be disabled with + --allow-recursive-routing option. + +- On Windows, when the ``--register-dns`` option is set, OpenVPN no longer + restarts the ``dnscache`` service - this had unwanted side effects, and + seems to be no longer necessary with currently supported Windows versions. + +- If no flags are given, and the interactive Windows service is used, "def1" + is implicitly set (because "delete and later reinstall the existing + default route" does not work well here). If not using the service, + the old behaviour is kept. + +- OpenVPN now reloads a CRL only if the modication time or file size has + changed, instead of for each new connection. This reduces the connection + setup time, in particular when using large CRLs. + +- OpenVPN now ships with more up-to-date systemd unit files which take advantage + of the improved service management as well as some hardening steps. The + configuration files are picked up from the /etc/openvpn/server/ and + /etc/openvpn/client/ directories (depending on unit file). This also avoids + these new unit files and how they work to collide with older pre-existing + unit files. + +- Using ``--no-iv`` (which is generally not a recommended setup) will + require explicitly disabling NCP with ``--disable-ncp``. This is + intentional because NCP will by default use AES-GCM, which requires + an IV - so we want users of that option to consciously reconsider. + + +Maintainer-visible changes +-------------------------- +- OpenVPN no longer supports building with crypto support, but without TLS + support. As a consequence, OPENSSL_CRYPTO_{CFLAGS,LIBS} and + OPENSSL_SSL_{CFLAGS,LIBS} have been merged into OPENSSL_{CFLAGS,LIBS}. This + is particularly relevant for maintainers who build their own OpenSSL library, + e.g. when cross-compiling. + +- Linux distributions using systemd is highly encouraged to ship these new unit + files instead of older ones, to provide a unified behaviour across systemd + based Linux distributions. + +- With OpenVPN v2.4, the project has moved over to depend on and actively use + the official C99 standard (-std=c99). This may fail on some older compiler/libc + header combinations. In most of these situations it is recommended to + use -std=gnu99 in CFLAGS. This is known to be needed when doing + i386/i686 builds on RHEL5. |