/*  $Id: ckpasswd.c 7565 2006-08-28 02:42:54Z eagle $
**
**  The default username/password authenticator.
**
**  This program is intended to be run by nnrpd and handle usernames and
**  passwords.  It can authenticate against a regular flat file (the type
**  managed by htpasswd), a DBM file, the system password file or shadow file,
**  or PAM.
*/

/* Used for unused parameters to silence gcc warnings. */
#define UNUSED  __attribute__((__unused__))

/* Make available the bool type. */
#if INN_HAVE_STDBOOL_H
# include <stdbool.h>
#else
# undef true
# undef false
# define true   (1)
# define false  (0)
# ifndef __cplusplus
#  define bool int
# endif
#endif /* INN_HAVE_STDBOOL_H */

#include <stdlib.h>
#include <string.h>
#include <crypt.h>
#include <fcntl.h>
#include <pwd.h>
#include <grp.h>

#define DB_DBM_HSEARCH 1
#include <db.h>
#define OPT_DBM "d:"

#if HAVE_GETSPNAM
# include <shadow.h>
# define OPT_SHADOW "s"
#else
# define OPT_SHADOW ""
#endif

/* The functions are actually macros so that we can pick up the file and line
   number information for debugging error messages without the user having to
   pass those in every time. */
#define xcalloc(n, size)        x_calloc((n), (size), __FILE__, __LINE__)
#define xmalloc(size)           x_malloc((size), __FILE__, __LINE__)
#define xrealloc(p, size)       x_realloc((p), (size), __FILE__, __LINE__)
#define xstrdup(p)              x_strdup((p), __FILE__, __LINE__)
#define xstrndup(p, size)       x_strndup((p), (size), __FILE__, __LINE__)

#include <security/pam_appl.h>

/* Holds the authentication information from nnrpd. */
struct auth_info {
    char *username;
    char *password;
};

/*
**  The PAM conversation function.
**
**  Since we already have all the information and can't ask the user
**  questions, we can't quite follow the real PAM protocol.  Instead, we just
**  return the password in response to every question that PAM asks.  There
**  appears to be no generic way to determine whether the message in question
**  is indeed asking for the password....
**
**  This function allocates an array of struct pam_response to return to the
**  PAM libraries that's never freed.  For this program, this isn't much of an
**  issue, since it will likely only be called once and then the program will
**  exit.  This function uses malloc and strdup instead of xmalloc and xstrdup
**  intentionally so that the PAM conversation will be closed cleanly if we
**  run out of memory rather than simply terminated.
**
**  appdata_ptr contains the password we were given.
*/
static int pass_conv(int num_msg, const struct pam_message **msgm UNUSED, struct pam_response **response, void *appdata_ptr)
{
    int i;

    *response = malloc(num_msg * sizeof(struct pam_response));
    if (*response == NULL)
        return PAM_CONV_ERR;
    for (i = 0; i < num_msg; i++) {
        (*response)[i].resp = strdup((char *)appdata_ptr);
        (*response)[i].resp_retcode = 0;
    }
    return PAM_SUCCESS;
}


/*
**  Authenticate a user via PAM.
**
**  Attempts to authenticate a user with PAM, returning true if the user
**  successfully authenticates and false otherwise.  Note that this function
**  doesn't attempt to handle any remapping of the authenticated user by the
**  PAM stack, but just assumes that the authenticated user was the same as
**  the username given.
**
**  Right now, all failures are handled via die.  This may be worth revisiting
**  in case we want to try other authentication methods if this fails for a
**  reason other than the system not having PAM support.
*/

static bool auth_pam(const char *username, char *password)
{
    pam_handle_t *pamh;
    struct pam_conv conv;
    int status;

    conv.conv = pass_conv;
    conv.appdata_ptr = password;
    status = pam_start("nnrpd", username, &conv, &pamh);
    if (status != PAM_SUCCESS)
        die("pam_start failed: %s", pam_strerror(pamh, status));
    status = pam_authenticate(pamh, PAM_SILENT);
    if (status != PAM_SUCCESS)
        die("pam_authenticate failed: %s", pam_strerror(pamh, status));
    status = pam_acct_mgmt(pamh, PAM_SILENT);
    if (status != PAM_SUCCESS)
        die("pam_acct_mgmt failed: %s", pam_strerror(pamh, status));
    status = pam_end(pamh, status);
    if (status != PAM_SUCCESS)
        die("pam_end failed: %s", pam_strerror(pamh, status));

    /* If we get to here, the user successfully authenticated. */
    return true;
}


/*
**  Try to get a password out of a dbm file.  The dbm file should have the
**  username for the key and the crypted password as the value.  The crypted
**  password, if found, is returned as a newly allocated string; otherwise,
**  NULL is returned.
*/
#if !(defined(HAVE_DBM) || defined(HAVE_BDB_DBM))
static char *
password_dbm(char *user UNUSED, const char *file UNUSED)
{
    return NULL;
}
#else
static char *
password_dbm(char *name, const char *file)
{
    datum key, value;
    DBM *database;
    char *password;

    database = dbm_open(file, O_RDONLY, 0600);
    if (database == NULL)
        return NULL;
    key.dptr = name;
    key.dsize = strlen(name);
    value = dbm_fetch(database, key);
    if (value.dptr == NULL) {
        dbm_close(database);
        return NULL;
    }
    password = xmalloc(value.dsize + 1);
    strlcpy(password, value.dptr, value.dsize + 1);
    dbm_close(database);
    return password;
}
#endif /* HAVE_DBM || HAVE_BDB_DBM */


/*
**  Try to get a password out of the system /etc/shadow file.  The crypted
**  password, if found, is returned as a newly allocated string; otherwise,
**  NULL is returned.
*/
#if !HAVE_GETSPNAM
static char *
password_shadow(const char *user UNUSED)
{
    return NULL;
}
#else
static char *
password_shadow(const char *user)
{
    struct spwd *spwd;

    spwd = getspnam(user);
    if (spwd != NULL)
        return xstrdup(spwd->sp_pwdp);
    return NULL;
}
#endif /* HAVE_GETSPNAM */


/*
**  Try to get a password out of the system password file.  The crypted
**  password, if found, is returned as a newly allocated string; otherwise,
**  NULL is returned.
*/
static char *
password_system(const char *username)
{
    struct passwd *pwd;

    pwd = getpwnam(username);
    if (pwd != NULL)
        return xstrdup(pwd->pw_passwd);
    return NULL;
}


/*
**  Try to get the name of a user's primary group out of the system group 
**  file.  The group, if found, is returned as a newly allocated string;
**  otherwise, NULL is returned.  If the username is not found, NULL is
**  returned.
*/
static char *
group_system(const char *username)
{
    struct passwd *pwd;
    struct group *gr;

    pwd = getpwnam(username);
    if (pwd == NULL)
        return NULL;
    gr = getgrgid(pwd->pw_gid);
    if (gr == NULL)
        return NULL;
    return xstrdup(gr->gr_name);
}


/*
**  Output username (and group, if desired) in correct return format.
*/
static void
output_user(const char *username, bool wantgroup)
{
    if (wantgroup) {
        char *group = group_system(username);
        if (group == NULL)
            die("group info for user %s not available", username);
        printf("User:%s@%s\n", username, group);
    }
    else
        printf("User:%s\n", username);
}


/*
**  Main routines.
**
**  We handle the variences between systems with #if blocks above, so that
**  this code can look fairly clean.
*/

int
main(int argc, char *argv[])
{
    enum authtype { AUTH_NONE, AUTH_SHADOW, AUTH_FILE, AUTH_DBM };

    int opt;
    enum authtype type = AUTH_NONE;
    bool wantgroup = false;
    const char *filename = NULL;
    struct auth_info *authinfo = NULL;
    char *password = NULL;

    //message_program_name = "ckpasswd";

    while ((opt = getopt(argc, argv, "gf:u:p:" OPT_DBM OPT_SHADOW)) != -1) {
        switch (opt) {
        case 'g':
            if (type == AUTH_DBM || type == AUTH_FILE)
                die("-g option is incompatible with -d or -f");
            wantgroup = true;
            break;
        case 'd':
            if (type != AUTH_NONE)
                die("only one of -s, -f, or -d allowed");
            if (wantgroup)
                die("-g option is incompatible with -d or -f");
            type = AUTH_DBM;
            filename = optarg;
            break;
        case 'f':
            if (type != AUTH_NONE)
                die("only one of -s, -f, or -d allowed");
            if (wantgroup)
                die("-g option is incompatible with -d or -f");
            type = AUTH_FILE;
            filename = optarg;
            break;
        case 's':
            if (type != AUTH_NONE)
                die("only one of -s, -f, or -d allowed");
            type = AUTH_SHADOW;
            break;
        case 'u':
            if (authinfo == NULL) {
                authinfo = xmalloc(sizeof(struct auth_info));
                authinfo->password = NULL;
            }
            authinfo->username = optarg;
            break;
        case 'p':
            if (authinfo == NULL) {
                authinfo = xmalloc(sizeof(struct auth_info));
                authinfo->username = NULL;
            }
            authinfo->password = optarg;
            break;
        default:
            exit(1);
        }
    }
    if (argc != optind)
	die("extra arguments given");
    if (authinfo != NULL && authinfo->username == NULL)
        die("-u option is required if -p option is given");
    if (authinfo != NULL && authinfo->password == NULL)
        die("-p option is required if -u option is given");

//     /* Unless a username or password was given on the command line, assume
//        we're being run by nnrpd. */
//     if (authinfo == NULL)
//         authinfo = get_auth_info(stdin);
//     if (authinfo == NULL)
//         die("no authentication information from nnrpd");
//     if (authinfo->username[0] == '\0')
//         die("null username");

    /* Run the appropriate authentication routines. */
    switch (type) {
    case AUTH_SHADOW:
        password = password_shadow(authinfo->username);
        if (password == NULL)
            password = password_system(authinfo->username);
        break;
//     case AUTH_FILE:
//         password = password_file(authinfo->username, filename);
//         break;
    case AUTH_DBM:
        password = password_dbm(authinfo->username, filename);
        break;
    case AUTH_NONE:
        if (auth_pam(authinfo->username, authinfo->password)) {
            output_user(authinfo->username, wantgroup);
            exit(0);
        }
        password = password_system(authinfo->username);
        break;
    }

    if (password == NULL)
        die("user %s unknown", authinfo->username);
    if (strcmp(password, crypt(authinfo->password, password)) != 0)
        die("invalid password for user %s", authinfo->username);

    /* The password matched. */
    output_user(authinfo->username, wantgroup);
    exit(0);
}