OpenConnect — sing-box

sing-box provides an OpenConnect client endpoint (type: "openconnect"). It connects to Cisco AnyConnect, Palo Alto GlobalProtect, Fortinet SSL VPN, F5 BIG-IP, Pulse Connect Secure and Juniper Network Connect servers and exposes the VPN as a routable endpoint carrying TCP, UDP and ICMP. A companion openconnect DNS server resolves names through the DNS settings the VPN server pushes.

Endpoint, client only

OpenConnect sits under the root endpoints[] array, like WireGuard and Tailscale, and is referenced from routing rules by its tag. Only the client side is implemented.

Endpoint options

type: "openconnect" under endpoints[]:

Field	Type	Default	Allowed values	Description
`system`	`bool`	`false`	`true \| false`	Use a real system interface instead of sing-box's internal network stack. Needs privileges and must not clash with an existing interface.
`name`	`string`	`(auto)`	`<interface name>`	Interface name when `system` is enabled. An `oc`-prefixed name is generated by default.
`udp_timeout`	`badoption.Duration`	`5m`	`<duration>`	UDP NAT session expiry.
`udp_mapping`	`UDPNATBehavior`	`endpoint_independent`	`endpoint_independent \| address_dependent \| address_and_port_dependent`	UDP NAT mapping: reuse one mapping per source for every destination, or split it per destination address / address and port.
`udp_filtering`	`UDPNATBehavior`	`endpoint_independent`	`endpoint_independent \| address_dependent \| address_and_port_dependent`	UDP NAT filtering: accept replies from any remote, or only from addresses / address-and-port pairs already contacted.
`udp_nat_max`	`uint32`	`0`	`<count>`	Maximum number of UDP NAT sessions; the least recently used one is closed at the limit. 0 means 4096 on iOS and 4096–16384 (by total memory) elsewhere.
`server`	`string`	`(required)`	`<hostname or https:// URL>`	VPN server HTTPS URL; `https://` is added if missing. User info, query strings and fragments are not supported.
`flavor`	`string`	`anyconnect`	`anyconnect \| gp \| fortinet \| f5 \| pulse \| nc`	Server family: Cisco AnyConnect, Palo Alto GlobalProtect, Fortinet, F5 BIG-IP, Pulse Connect Secure, Juniper Network Connect.
`username`	`string`	`(unset)`	`<string>`	Fills matching username fields of the authentication form.
`password`	`string`	`(unset)`	`<string>`	Fills matching password fields of the authentication form.
`auth_group`	`string`	`(unset)`	`<string>`	Preselects a matching group, realm, domain or gateway choice where the flavor supports it.
`cookie`	`string`	`(unset)`	`<session cookie>`	Existing authenticated session, tried before prompting for credentials. Format depends on the flavor (e.g. `webvpn` for AnyConnect, `SVPNCOOKIE` for Fortinet, `DSID` for Network Connect); normal login is attempted if the server rejects it.
`token`	`*OpenConnectTokenOptions`	`(unset)`	`OpenConnectTokenOptions`	Software token (TOTP, HOTP, RSA SecurID) or OIDC access token used to answer token prompts or Bearer authentication. See below.
`reported_os`	`string`	`(from platform)`	`linux \| linux-64 \| win \| mac-intel \| android \| apple-ios`	OS identity reported to AnyConnect, GlobalProtect and Pulse servers. Defaults to the running platform.
`user_agent`	`string`	`(flavor-specific)`	`<string>`	User agent reported to the server. Defaults: an AnyConnect-compatible OpenConnect agent (AnyConnect, Network Connect, Pulse, F5), `PAN GlobalProtect`, `Mozilla/5.0 SV1` (Fortinet).
`version`	`string`	`v9.21`	`<string>`	Client version reported separately from `user_agent`; currently used by AnyConnect XML authentication.
`local_hostname`	`string`	`(system hostname)`	`<string>`	Hostname reported to the server; `localhost` if the system hostname is unavailable.
`mobile`	`*OpenConnectMobileOptions`	`(unset)`	`OpenConnectMobileOptions`	Report an AnyConnect mobile-client identity. When set, all three sub-fields are required. See below.
`csd`	`*OpenConnectCSDOptions`	`(built-in)`	`{ wrapper_path }`	AnyConnect CSD / host-scan handling. Built in by default; `wrapper_path` runs an external wrapper executable instead.
`hip`	`*OpenConnectHIPOptions`	`(built-in)`	`{ wrapper_path }`	GlobalProtect HIP report handling. Built in by default; `wrapper_path` runs an external wrapper executable instead.
`tncc`	`*OpenConnectTNCCOptions`	`(built-in)`	`OpenConnectTNCCOptions`	Network Connect TNCC compliance handling. See below.
`fortinet_host_check`	`*OpenConnectFortinetHostCheckOptions`	`(disabled)`	`OpenConnectFortinetHostCheckOptions`	Fortinet hostcheck result override; only active when `hostcheck` is non-empty. See below.
`no_udp`	`bool`	`false`	`true \| false`	Disable the DTLS / ESP data channel and carry all traffic over the TLS channel.
`dtls_local_port`	`uint16`	`0`	`<port>`	Local UDP port for the direct DTLS / ESP data channel; 0 picks an ephemeral port.
`compression_disabled`	`bool`	`false`	`true \| false`	Disable AnyConnect compression negotiation. Conflicts with `compression_mode: all`.
`compression_mode`	`string`	`stateless`	`stateless \| all`	AnyConnect compression: `stateless` advertises `oc-lz4` / `lzs`; `all` also offers stateful `deflate` for CSTP (DTLS stays stateless). Compression can leak information about tunnelled plaintext.
`ipv6_disabled`	`bool`	`false`	`true \| false`	Do not request or use IPv6 tunnel configuration.
`http_keepalive_disabled`	`bool`	`false`	`true \| false`	Disable HTTP connection reuse during authentication and configuration requests.
`xml_post_disabled`	`bool`	`false`	`true \| false`	Skip AnyConnect XML POST authentication and start with the legacy GET flow.
`external_auth_disabled`	`bool`	`false`	`true \| false`	Disable external-browser authentication (SSO / SAML) for AnyConnect, GlobalProtect and Fortinet; unexpected external-auth requests are rejected.
`password_authentication_disabled`	`bool`	`false`	`true \| false`	Abort AnyConnect authentication when the server returns a non-success form (like OpenConnect's `--no-passwd`). Does not affect other flavors or `cookie`.
`tcp_keep_alive_enabled`	`bool`	`false`	`true \| false`	Enable TCP keep-alive on direct VPN server connections (off by default, as in OpenConnect). Setting `tcp_keep_alive` or `tcp_keep_alive_interval` also enables it.
`pfs`	`bool`	`false`	`true \| false`	Require forward-secret cipher suites for TLS 1.2 and earlier. Off by default for servers that need RSA key exchange.
`mtu`	`uint32`	`0`	`<576-65535>`	Preferred tunnel MTU; the negotiated MTU is capped to it (0 = negotiated). Non-zero values below 576 become 576.
`base_mtu`	`uint32`	`1406`	`<1280-65535>`	Path MTU used to derive the tunnel MTU after outer overhead (AnyConnect, GlobalProtect, F5, Fortinet). Values below 1280 become 1280.
`dpd_interval`	`badoption.Duration`	`(server-provided)`	`<duration>`	Override the Dead Peer Detection interval. Positive values below 2s become 2s.
`reconnect_timeout`	`badoption.Duration`	`300s`	`<duration>`	Maximum accumulated backoff across failed reconnect attempts; the first retry happens immediately.
`trojan_interval`	`badoption.Duration`	`(server-provided)`	`<duration>`	Interval between GlobalProtect HIP reports / Network Connect TNCC checks. GlobalProtect uses 1h if the server sends none.
`queue_length`	`uint32`	`32`	`<packets>`	Packet queue length between the VPN transport and the tunnel interface. A full queue applies backpressure instead of dropping packets.
`allow_insecure_crypto`	`bool`	`false`	`true \| false`	Allow weak TLS / DTLS cipher suites and TLS 1.0 for legacy servers. Does not disable certificate verification.
`tls`	`OpenConnectTLSOptions`	`(system trust)`	`OpenConnectTLSOptions`	OpenConnect's own TLS settings (not the shared sing-box TLS block). See below.
`form_entries`	`[]OpenConnectFormEntryOptions`	`[]`	`[OpenConnectFormEntryOptions]`	Authentication-form field overrides. See below.

Source: option/openconnect.go:5-49 · pinned at v1.14.2 (af6e64c)

The endpoint also embeds the usual dial fields (detour, bind_interface, tcp_keep_alive, …); they apply to the connections made to the VPN server. csd and hip each take a single wrapper_path field.

`token`

Field	Type	Default	Allowed values	Description
`mode`	`string`	`(required)`	`totp \| hotp \| stoken \| oidc`	Token type: TOTP, HOTP, RSA SecurID software token (`stoken`), or an OIDC access token sent as HTTP Bearer authentication.
`secret`	`string`	`(unset)`	`<secret>`	Token secret: Base32, `base32:`-prefixed or an `otpauth://` URI for TOTP / HOTP; the CTF token content for `stoken`; the access token for `oidc` (sent only when the server asks for Bearer auth). One of `secret` / `secret_path` is required.
`secret_path`	`string`	`(unset)`	`<file path>`	Read the secret or OIDC access token from a file. Conflicts with `secret`.
`pin`	`string`	`(unset)`	`<PIN>`	RSA SecurID PIN (`stoken`).
`password`	`string`	`(unset)`	`<string>`	Password that decrypts a password-protected SecurID token (`stoken`).
`device_id`	`string`	`(unset)`	`<string>`	Device ID that decrypts a device-bound SecurID token (`stoken`).
`counter`	`uint64`	`0`	`<uint64>`	Initial HOTP counter; 0 uses the counter from an `otpauth://` URI when present.

Source: option/openconnect.go:51-59 · pinned at v1.14.2 (af6e64c)

`tls`

OpenConnect uses its own TLS block rather than the shared TLS options — there is no uTLS, REALITY or ECH here.

Field	Type	Default	Allowed values	Description
`insecure`	`bool`	`false`	`true \| false`	Skip server certificate and hostname verification. Lets an active attacker impersonate the server; prefer `certificate_authority` or `peer_fingerprint`.
`server_name`	`string`	`(host from server)`	`<hostname>`	SNI and the name used for certificate verification.
`peer_fingerprint`	`badoption.Listable[string]`	`(unset)`	`<SHA-1 hex> \| sha1:<hex> \| sha256:<hex> \| pin-sha256:<base64>`	Allowed server certificate fingerprints: an unprefixed SHA-1 certificate hash (as OpenConnect's `--servercert`) or SPKI hashes. Prefixes of at least 4 characters are accepted; a match can authorize an otherwise untrusted certificate.
`system_trust_disabled`	`bool`	`false`	`true \| false`	Ignore the system CA pool; establish trust with `certificate_authority` or `peer_fingerprint` instead.
`certificate_authority`	`badoption.Listable[string]`	`(unset)`	`<PEM>`	Extra trusted CA certificates (PEM content), added to the system pool. Conflicts with `certificate_authority_path`.
`certificate_authority_path`	`string`	`(unset)`	`<file path>`	Extra trusted CA certificates read from a PEM file.
`client_certificate`	`badoption.Listable[string]`	`(unset)`	`<PEM>`	Client certificate chain (PEM content). Certificate and key must be set together.
`client_certificate_path`	`string`	`(unset)`	`<file path>`	Client certificate chain read from a PEM file.
`client_key`	`badoption.Listable[string]`	`(unset)`	`<PEM>`	Client private key (PEM content).
`client_key_path`	`string`	`(unset)`	`<file path>`	Client private key read from a PEM file.
`client_key_password`	`string`	`(unset)`	`<string>`	Password for an encrypted client key.
`mca_certificate`	`badoption.Listable[string]`	`(unset)`	`<PEM>`	AnyConnect multiple-certificate authentication (MCA) certificate chain (PEM content). Certificate and key must be set together.
`mca_certificate_path`	`string`	`(unset)`	`<file path>`	MCA certificate chain read from a PEM file.
`mca_key`	`badoption.Listable[string]`	`(unset)`	`<PEM>`	MCA private key (PEM content).
`mca_key_path`	`string`	`(unset)`	`<file path>`	MCA private key read from a PEM file.
`mca_key_password`	`string`	`(unset)`	`<string>`	Password for an encrypted MCA key.

Source: option/openconnect.go:93-110 · pinned at v1.14.2 (af6e64c)

`form_entries`

Entries match by submission_key, or by form_id plus name; later matching entries win.

Field	Type	Default	Allowed values	Description
`form_id`	`string`	`(unset)`	`<string>`	Form identifier; matched together with `name` when `submission_key` is empty.
`submission_key`	`string`	`(unset)`	`<string>`	Field submission key. Either this or both `form_id` and `name` are required; later matching entries take precedence.
`name`	`string`	`(unset)`	`<string>`	Field name, matched together with `form_id`.
`value`	`string`	`(unset)`	`<string>`	Value filled in automatically. Conflicts with `promote`.
`promote`	`bool`	`false`	`true \| false`	Ask for this field interactively instead of filling it. Conflicts with `value`.

Source: option/openconnect.go:112-118 · pinned at v1.14.2 (af6e64c)

`tncc`

Field	Type	Default	Allowed values	Description
`wrapper_path`	`string`	`(built-in)`	`<file path>`	External TNCC wrapper executable. Conflicts with every other `tncc` field.
`device_id`	`string`	`(unset)`	`<string>`	Device ID reported by the built-in handler.
`user_agent`	`string`	`Neoteris HC Http`	`<string>`	User agent of the built-in handler.
`machine_identification_enabled`	`bool`	`false`	`true \| false`	Let the built-in handler report platform, hostname and observed MAC addresses.
`certificates`	`[]OpenConnectTNCCCertificateOptions`	`[]`	`[{ certificate \| certificate_path }]`	Machine certificates (PEM content or path) used to answer certificate requests. Requires `machine_identification_enabled`.

Source: option/openconnect.go:75-81 · pinned at v1.14.2 (af6e64c)

Each certificates[] entry takes either certificate (PEM content) or certificate_path.

`fortinet_host_check`

Field	Type	Default	Allowed values	Description
`hostcheck`	`string`	`(unset)`	`<status>,<os-version>`	Hostcheck result string, e.g. `0100,10.0.19042` — four 0/1 flags for third-party firewall, third-party antivirus, FortiClient firewall and FortiClient antivirus, then the OS version. Empty disables hostcheck.
`check_virtual_desktop`	`string`	`(empty)`	`<MAC>\|<MAC>…`	Virtual-desktop check result, conventionally `\|`-joined MAC addresses. Sent as an empty field when unset.

Source: option/openconnect.go:83-86 · pinned at v1.14.2 (af6e64c)

`mobile`

Field	Type	Default	Allowed values	Description
`platform_version`	`string`	`(required)`	`<string>`	Mobile OS version reported to the AnyConnect server.
`device_type`	`string`	`(required)`	`<string>`	Device model or type.
`device_unique_id`	`string`	`(required)`	`<string>`	Device identifier.

Source: option/openconnect.go:61-65 · pinned at v1.14.2 (af6e64c)

DNS server

type: "openconnect" under dns.servers[]:

Field	Type	Default	Allowed values	Description
`endpoint`	`string`	`(required)`	`<endpoint tag>`	Tag of the OpenConnect endpoint. Queries go to the resolvers the VPN server pushed: split-DNS rules use their own resolvers, pushed split-DNS and search-domain suffixes use the general ones, and the most specific suffix wins.
`accept_default_resolvers`	`bool`	`false`	`true \| false`	Also answer unmatched queries with the pushed general resolvers — only when the server tunnels all DNS or pushes no split-DNS rules or suffixes. Otherwise unmatched queries get NXDOMAIN.
`accept_search_domain`	`bool`	`false`	`true \| false`	Retry single-label names (e.g. `intranet`) with each pushed search domain until one resolves.

Source: option/openconnect.go:120-124 · pinned at v1.14.2 (af6e64c)

Examples

Minimal AnyConnect client, routing a private range through the VPN:

json

{
  "endpoints": [
    {
      "type": "openconnect",
      "tag": "oc-client",
      "server": "vpn.example.com",
      "flavor": "anyconnect",
      "username": "alice",
      "password": "<password>"
    }
  ],
  "route": {
    "rules": [
      { "ip_cidr": ["10.0.0.0/8"], "outbound": "oc-client" }
    ]
  }
}

GlobalProtect with a TOTP token, answering the VPN's split-DNS names through the pushed resolvers:

json

{
  "dns": {
    "servers": [
      { "type": "local", "tag": "local" },
      { "type": "openconnect", "tag": "oc-dns", "endpoint": "gp-client" }
    ],
    "rules": [
      { "preferred_by": "oc-dns", "action": "route", "server": "oc-dns" }
    ],
    "final": "local"
  },
  "endpoints": [
    {
      "type": "openconnect",
      "tag": "gp-client",
      "server": "https://gp.example.com",
      "flavor": "gp",
      "username": "alice",
      "password": "<password>",
      "token": { "mode": "totp", "secret": "<base32 secret>" }
    }
  ]
}

Notes

The type is only compiled in with the with_openconnect build tag, and the default userspace mode (system: false) additionally needs with_gvisor. Without them, the endpoint and the DNS server fail at startup with a rebuild hint.
Only non-interactive login works from a config file: username / password, token, cookie and form_entries. SSO / SAML and any other prompt the config cannot answer are completed through the sing-box graphical clients or the Dashboard (Tools → Endpoints).
Pushed DNS settings are never installed into the operating system. Add an openconnect DNS server to use them; with preferred_by as in the example above, only the VPN's own names are sent there.
compression_mode: all enables stateful compression, which carries extra confidentiality risks — only use it when the server requires it.
tls.insecure and allow_insecure_crypto are independent: the first skips certificate checks, the second only re-enables legacy ciphers and TLS 1.0.

Cross-core notes

mihomo has no OpenConnect client; its closest VPN-style outbound is OpenVPN — mihomo.
Xray-core has no OpenConnect support.

Source: option/openconnect.go:5-49 · v1.14.2 (af6e64c)

OpenConnect — sing-box ​

Endpoint options ​

token ​

tls ​

form_entries ​

tncc ​

fortinet_host_check ​

mobile ​

DNS server ​

Examples ​

Notes ​

Cross-core notes ​