TAN and Resume - Varinomics

TAN selection, TAN media, interactive TAN entry, decoupled approval polling, and Verification of Payee confirmation are FinTS-backed C API surfaces. Probe TAN and resume support for arbitrary backend handles through gln_check_backend_operation_support.

For Verification of Payee scheme background, see the European Payments Council Verification Of Payee page.

Operations

Operation	Request	Result kind
`gln_retrieve_tan_modes`	none	`GLN_BACKEND_RESULT_KIND_TAN_MODES`
`gln_set_tan_mode`	`gln_set_tan_mode_request_t`	`GLN_BACKEND_RESULT_KIND_TAN_MODE_SELECTION`
`gln_retrieve_tan_media`	none	`GLN_BACKEND_RESULT_KIND_TAN_MEDIA`
`gln_resume_continuation`	`gln_continuation_t*`, optional secret, `gln_continuation_input_t`	Operation-dependent

TAN Modes

gln_retrieve_tan_modes returns gln_tan_modes_t.

Accessor	Meaning
`gln_get_tan_modes_count`, `gln_get_tan_mode_at`	Enumerate available rows.
`gln_get_tan_modes_selected`	Current selected security function, when known.
`gln_get_tan_mode_security_function`	Security function code to pass to `gln_set_tan_mode`.
`gln_get_tan_mode_name`	Bank-supplied display name.
`gln_get_tan_mode_decoupled`	Non-zero when approval happens out of band.

gln_backend_result_t* result = NULL;
if (gln_retrieve_tan_modes(backend, &result) == GLN_OK &&
    gln_get_backend_result_outcome(result) == GLN_BACKEND_OUTCOME_SUCCESS) {
    const gln_tan_modes_t* modes = gln_get_backend_result_tan_modes(result);
    const gln_tan_mode_t* mode = gln_get_tan_mode_at(modes, 0);

    gln_set_tan_mode_request_t request = {0};

    gln_default_set_tan_mode_request(&request);
    request.security_function = gln_get_tan_mode_security_function(mode);

    gln_backend_result_t* selection_result = NULL;
    gln_set_tan_mode(backend, &request, &selection_result);
    gln_destroy_backend_result(selection_result);
}
gln_destroy_backend_result(result);

TAN Media

gln_retrieve_tan_media returns gln_tan_media_t.

Accessor	Meaning
`gln_get_tan_media_count`, `gln_get_tan_medium_at`	Enumerate TAN media.
`gln_get_tan_medium_media_name`	Bank label.
`gln_get_tan_medium_media_type`	Bank media type code.
`gln_get_tan_medium_phone_number`	Phone number, when supplied.
`gln_get_tan_medium_card_number`	Card number, when supplied.
`gln_get_tan_medium_active`	Non-zero when active.

Interrupts

Action-required envelopes carry a borrowed gln_interrupt_info_t:

Interrupt kind	Envelope status	Active fields
`GLN_INTERRUPT_TAN_REQUIRED`	`GLN_ERR_TAN_REQUIRED`	`tan.challenge`, `tan.challenge_html`, optional HHDuc, medium name, and task reference.
`GLN_INTERRUPT_DECOUPLED_PENDING`	`GLN_ERR_DECOUPLED_PENDING`	`decoupled_poll` fields plus `retry_after_seconds`.
`GLN_INTERRUPT_VOP_CONFIRMATION_REQUIRED`	`GLN_ERR_VOP_CONFIRMATION_REQUIRED`	`vop_confirm.vop_id_or_null`, `vop_confirm.result_code_or_null`, `vop_confirm.alternate_name_or_null`, and `vop_confirm.explanatory_text_or_null`.

Provider status rows attached to an interrupt are available with gln_get_interrupt_info_provider_status_count and gln_get_interrupt_info_provider_status_at.

The VoP interrupt fields are populated from the normalized Verification of Payee response. vop_id_or_null is the identifier stored in the continuation and submitted by supported VoP confirmation resume paths when the caller confirms the prompt. result_code_or_null is the bank/protocol VoP result code. alternate_name_or_null and explanatory_text_or_null carry the normalized alternate beneficiary name and explanation when present; a non-null empty string means the normalized VoP info has no value for that field.

Resume Inputs

Initialize gln_continuation_input_t by calling gln_default_continuation_input.

Resume case	Input setup
User enters a TAN	Create a `gln_secret_t*` from the TAN bytes and pass it as `in_interactive_secret_or_null`; use `GLN_CONTINUATION_INPUT_KIND_NONE` unless HHDuc response data is needed.
Decoupled poll	Set `kind = GLN_CONTINUATION_INPUT_KIND_DECOUPLED_POLL`.
Decoupled-pending HHDuc echo/status variant	Set `kind = GLN_CONTINUATION_INPUT_KIND_HHDUC_RESPONSE` and fill `hhduc_response_or_null`.
VoP confirmation	Set `kind = GLN_CONTINUATION_INPUT_KIND_VOP_CONFIRM`; supported VoP confirmation resume paths confirm the VoP id stored in the continuation.

gln_default_continuation_input before a NULL interactive secret is not a complete resume input; the returned envelope reports GLN_ERR_INVALID_ARG.

Unsupported VoP confirmation resume paths return an error envelope with status GLN_ERR_NOT_SUPPORTED and issue type unsupported_vop_confirmation_backend.

gln_continuation_t* continuation = gln_take_backend_result_continuation(result);

gln_continuation_input_t input = {0};

gln_default_continuation_input(&input);
gln_backend_result_t* resumed = NULL;
gln_status_t resume_status = gln_resume_continuation(
    backend,
    continuation,
    tan_secret_or_null,
    &input,
    &resumed);

if (resume_status == GLN_OK) {
    /* Inspect resumed just like any other backend result envelope. */
}

gln_destroy_backend_result(resumed);
gln_destroy_continuation(continuation);

Use gln_save_continuation and gln_load_continuation when an operation may be resumed after process restart.