#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <security/pam_appl.h>

static int converse(int n, const struct pam_message **msg,
                    struct pam_response **resp, void *data)
{
    struct pam_response *aresp;
    char buf[PAM_MAX_RESP_SIZE];
    int i;

    if (n <= 0 || n > PAM_MAX_NUM_MSG)
        return (PAM_CONV_ERR);
    if ((aresp = calloc(n, sizeof *aresp)) == NULL)
        return (PAM_BUF_ERR);
    for (i = 0; i < n; ++i)
    {   
        aresp[i].resp_retcode = 0;
        aresp[i].resp = NULL;
        switch (msg[i]->msg_style)
        {   
        case PAM_PROMPT_ECHO_OFF:
            aresp[i].resp = strdup("root"); //    getpass(msg[i]->msg));
            if (aresp[i].resp == NULL)
                goto fail;
            break;
        case PAM_PROMPT_ECHO_ON:
            fputs(msg[i]->msg, stderr);
            if (fgets(buf, sizeof buf, stdin) == NULL)
                goto fail;
            aresp[i].resp = strdup(buf);
            if (aresp[i].resp == NULL)
                goto fail;
            break;
        case PAM_ERROR_MSG:
            fputs(msg[i]->msg, stderr);
            if (strlen(msg[i]->msg) > 0 &&
                msg[i]->msg[strlen(msg[i]->msg) - 1] != '\n')
                fputc('\n', stdout);
            break;
        case PAM_TEXT_INFO:
            fputs(msg[i]->msg, stdout);
            if (strlen(msg[i]->msg) > 0 &&
                msg[i]->msg[strlen(msg[i]->msg) - 1] != '\n')
                fputc('\n', stdout);
            break;
        default:
            goto fail;
        }   
    }   
    *resp = aresp;
    return (PAM_SUCCESS);
fail:
    for (i = 0; i < n; ++i)
    {   
        if (aresp[i].resp != NULL)
        {   
            memset(aresp[i].resp, 0, strlen(aresp[i].resp));
            free(aresp[i].resp);
        }   
    }   
    memset(aresp, 0, n * sizeof *aresp);
    *resp = NULL;
    return (PAM_CONV_ERR);
}

int main()
{
    pam_handle_t *pamh;
    struct pam_conv pamc;
    pamc.conv = converse;
    int rc = pam_start("pamapp", "admin", &pamc, &pamh);
    if (rc != PAM_SUCCESS)
    {
        printf("Failed to init PAM (%s)\n", pam_strerror(pamh, rc));
        return EXIT_FAILURE;
    }

    char buff[256];
    gethostname(buff, sizeof(buff));
    rc = pam_set_item(pamh, PAM_RUSER, "admin");
    rc = pam_set_item(pamh, PAM_RHOST, strdup(buff));
    if (rc != PAM_SUCCESS)
        printf("Failed to set items: %s (%d)\n", pam_strerror(pamh, rc), rc);

    rc = pam_authenticate(pamh, 0);
    if (rc != PAM_SUCCESS)
    {
        printf("Failed to authenticate: %s (%d)\n", pam_strerror(pamh, rc), rc);
        if (rc == PAM_MODULE_UNKNOWN)
            printf("Are 32 bit modules installed? (apt-get install libpam-modules:i386)");
    }

    pam_end(pamh, rc);

    return rc != PAM_SUCCESS;
}