Absolutely minimalistic pam authentication example

simple_pam_auth.c

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <unistd.h> /* getpass */
#include <security/pam_appl.h> /* pam_start, pam_conv, pam_end, ... */

#define TRY(x) ret = (x); printf("PAM: %s\n", pam_strerror(handle, ret)); if (ret != PAM_SUCCESS) goto finally

int test_conv(int num_msg, const struct pam_message **msg,
        struct pam_response **resp, void *appdata_ptr){
    const struct pam_message* msg_ptr = *msg;
    struct pam_response * resp_ptr = NULL;
    int x = 0;
    *resp = calloc(sizeof(struct pam_response), num_msg);
    for (x = 0; x < num_msg; x++, msg_ptr++){
        char* resp_str;
        switch (msg_ptr->msg_style){
            case PAM_PROMPT_ECHO_OFF:
            case PAM_PROMPT_ECHO_ON:
                resp_str = getpass(msg_ptr->msg);
                resp[x]->resp= strdup(resp_str);
                break;

            case PAM_ERROR_MSG:
            case PAM_TEXT_INFO:
                printf("PAM: %s\n", msg_ptr->msg);
                break;

            default:
                assert(0);

        }
    }
    return PAM_SUCCESS;
}

int main(int argc, char** argv){

    int len = 1000;
    const char service[] = "passwd";
    char user[len];
    const char *changed_username = NULL;
    struct pam_conv conv;
    char resp_str[len];
    conv.conv=test_conv;
    pam_handle_t* handle;
    int ret;
    printf("Username: ");
    fgets(user,len, stdin); 
    strtok(user, "\n");

    TRY( pam_start(service, user, &conv, &handle ));
    TRY( pam_authenticate(handle, 0));
    TRY( pam_acct_mgmt(handle, 0)); 
    TRY( pam_get_item(handle, PAM_USER,(const void**) &changed_username ));
    if (changed_username != NULL) {
        printf("PAM: %s\n", changed_username);
    }
finally:
    pam_end(handle, ret);
    return ret;
 }

should't it be

(*resp)[idx].resp=strdup(...)

?