DUO(3)

NAME
duo - Duo authentication service

SYNOPSIS
#include <duo.h>
duo_t *
duo_open(const char *ikey, const char *skey, const char *progname, const char *cafile);
void
duo_set_conv_funcs(duo_t *d, char *(*conv_prompt)(void *conv_arg, const char *, char *, size_t), void (*conv_status)(void *conv_arg, const char *msg), void *conv_arg);
void
duo_set_host(duo_t *d, const char *hostname);
void
duo_set_ssl_verify(duo_t *d, int bool);
duo_code_t
duo_login(duo_t *d, const char *username, const char *client_ip, int flags, const char *command);
const char *
duo_geterr(duo_t *d);
void
duo_close(duo_t *d);

DESCRIPTION
The duo API provides access to the Duo two-factor authentication service.

duo_open() is used to obtain a handle to the Duo service. ikey and skey are the required integration and secret keys, respectively, for a Duo customer account. progname identifies the program to the Duo service. cafile should be NULL or the pathname of a PEM-format CA certificate to override the default.

duo_set_conv_funcs() may be used to override the internal user conversation functions. conv_prompt is called to present the user a login menu and prompt, and gather their response, returning buf or NULL on error. It may be set to NULL if automatic login is specified with DUO_FLAG_AUTO. conv_status is called to display status messages to the user, and may be NULL if no status display is needed. conv_arg is passed as the first argument to these conversation functions.

duo_set_host() may be used to override the default Duo API host.

duo_set_ssl_verify() may be used to override SSL certificate verification (enabled by default).

duo_login() performs secondary authentication via the Duo service for the specified username. client_ip is the source IP address of the connection to be authenticated, or NULL to specify the local host. The following bitmask values are defined for flags:

DUO_FLAG_AUTO
    Attempt authentication without prompting the user, using their default out-of-band authentication factor.
DUO_FLAG_SYNC
    Do not report incremental status during authentication (e.g. voice callback progress) - only issue one status message per authentication attempt.

If not NULL, the command to be authorized will be displayed during push authentication.

duo_geterr() returns a description of the last-seen error on the specified Duo API handle. The returned constant string should not be modified or freed by the caller.

duo_close() closes and frees the specified Duo API handle.

RETURN VALUES
duo_open() returns a pointer to the configured Duo API handle, or NULL on failure.

duo_login() returns status codes of type duo_code_t, which may have the following values:

DUO_OK
    User authenticated
DUO_FAIL
    User failed to authenticate
DUO_ABORT
    User denied by policy
DUO_LIB_ERROR
    Unexpected library error
DUO_CONN_ERROR
    Duo service unreachable
DUO_CLIENT_ERROR
    Invalid client parameters to API call
DUO_SERVER_ERROR
    Duo service error

In the event of a DUO_*_ERROR return, duo_geterr may be called to recover a human-readable error message.

duo_geterr() returns a constant string which should not be modified or freed by the caller.

SEE ALSO
pam_duo(8), login_duo(1)

AUTHORS
Duo Security <support@duosecurity.com>