# sasl_callbacks - How to work with SASL callbacks¶

## Synopsis¶

#include <sasl/sasl.h>


## Description¶

sasl_callbacks are used when the application needs some information from the application. Common reasons are getting for getting usernames and passwords. A client MUST specify what callbacks they support in the sasl_client_init(3)/sasl_server_init(3) or sasl_client_new(3)/sasl_server_new(3) calls. If an authentication mechanism needs a callback that the application does not state it supports it cannot be used.

If a callback has an id parameter that should be checked to make sure you are giving the appropriate value.

If an application is using the client side of the library functions to handle the callbacks are not necessary. Instead the application may deal with callbacks via SASL_INTERACT’s. See sasl_client_start(3)/sasl_client_step(3) for more information.

### Common Callbacks¶

sasl_getopt_t
Get an option value
sasl_log_t
Log message handler
sasl_getpath_t
Get path to search for plugins (e.g. SASL mechanisms)
sasl_verifyfile_t
Verify files for use by SASL
sasl_canon_user_t(3)

### Client-only Callbacks¶

sasl_getsimple_t
Get user/language list
sasl_getsecret_t
Get authentication secret
sasl_chalprompt_t(3)
Display challenge and prompt for response
sasl_getrealm_t
Get the realm for authentication

### Server-only Callbacks¶

sasl_authorize_t(3)
Authorize policy callback
sasl_server_userdb_checkpass_t
SASL callback functions should return SASL return codes. See sasl_errors(3) for a complete list. SASL_OK typically indicates success.