path: root/modules/pam_issue/pam_issue.c

/* pam_issue module - a simple /etc/issue parser to set PAM_USER_PROMPT
 *
 * Copyright 1999 by Ben Collins <bcollins@debian.org>
 *
 * Needs to be called before any other auth modules so we can setup the
 * user prompt before it's first used. Allows one argument option, which
 * is the full path to a file to be used for issue (uses /etc/issue as a
 * default) such as "issue=/etc/issue.telnet".
 *
 * We can also parse escapes within the the issue file (enabled by
 * default, but can be disabled with the "noesc" option). It's the exact
 * same parsing as util-linux's agetty program performs.
 *
 * Released under the GNU LGPL version 2 or later
 */

#include "config.h"

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <sys/utsname.h>
#include <utmp.h>
#include <time.h>
#include <syslog.h>

#define PAM_SM_AUTH

#include <security/_pam_macros.h>
#include <security/pam_modules.h>
#include <security/pam_ext.h>

static int _user_prompt_set = 0;

static int read_issue_raw(pam_handle_t *pamh, FILE *fp, char **prompt);
static int read_issue_quoted(pam_handle_t *pamh, FILE *fp, char **prompt);

/* --- authentication management functions (only) --- */

PAM_EXTERN int
pam_sm_authenticate (pam_handle_t *pamh, int flags UNUSED,
		     int argc, const char **argv)
{
    int retval = PAM_SERVICE_ERR;
    FILE *fp;
    const char *issue_file = NULL;
    int parse_esc = 1;
    const void *item = NULL;
    const char *cur_prompt;
    char *issue_prompt = NULL;

   /* If we've already set the prompt, don't set it again */
    if(_user_prompt_set)
	return PAM_IGNORE;

    /* We set this here so if we fail below, we wont get further
       than this next time around (only one real failure) */
    _user_prompt_set = 1;

    for ( ; argc-- > 0 ; ++argv ) {
	if (!strncmp(*argv,"issue=",6)) {
	    issue_file = 6 + *argv;
	    D(("set issue_file to: %s", issue_file));
	} else if (!strcmp(*argv,"noesc")) {
	    parse_esc = 0;
	    D(("turning off escape parsing by request"));
	} else
	    D(("unknown option passed: %s", *argv));
    }

    if (issue_file == NULL)
	issue_file = "/etc/issue";

    if ((fp = fopen(issue_file, "r")) == NULL) {
	pam_syslog(pamh, LOG_ERR, "error opening %s: %m", issue_file);
	return PAM_SERVICE_ERR;
    }

    if ((retval = pam_get_item(pamh, PAM_USER_PROMPT, &item)) != PAM_SUCCESS) {
	fclose(fp);
	return retval;
    }

    cur_prompt = item;
    if (cur_prompt == NULL)
	cur_prompt = "";

    if (parse_esc)
	retval = read_issue_quoted(pamh, fp, &issue_prompt);
    else
	retval = read_issue_raw(pamh, fp, &issue_prompt);

    fclose(fp);

    if (retval != PAM_SUCCESS)
	goto out;

    {
	size_t size = strlen(issue_prompt) + strlen(cur_prompt) + 1;
	char *new_prompt = realloc(issue_prompt, size);

	if (new_prompt == NULL) {
	    pam_syslog(pamh, LOG_ERR, "out of memory");
	    retval = PAM_BUF_ERR;
	    goto out;
	}
	issue_prompt = new_prompt;
    }

    strcat(issue_prompt, cur_prompt);
    retval = pam_set_item(pamh, PAM_USER_PROMPT,
			      (const void *) issue_prompt);
  out:
    _pam_drop(issue_prompt);
    return (retval == PAM_SUCCESS) ? PAM_IGNORE : retval;
}

PAM_EXTERN int
pam_sm_setcred (pam_handle_t *pamh UNUSED, int flags UNUSED,
		int argc UNUSED, const char **argv UNUSED)
{
     return PAM_IGNORE;
}

static int
read_issue_raw(pam_handle_t *pamh, FILE *fp, char **prompt)
{
    char *issue;
    struct stat st;

    *prompt = NULL;

    if (fstat(fileno(fp), &st) < 0) {
	pam_syslog(pamh, LOG_ERR, "stat error: %m");
	return PAM_SERVICE_ERR;
    }

    if ((issue = malloc(st.st_size + 1)) == NULL) {
	pam_syslog(pamh, LOG_ERR, "out of memory");
	return PAM_BUF_ERR;
    }

    if (fread(issue, 1, st.st_size, fp) != st.st_size) {
	pam_syslog(pamh, LOG_ERR, "read error: %m");
	_pam_drop(issue);
	return PAM_SERVICE_ERR;
    }

    issue[st.st_size] = '\0';
    *prompt = issue;
    return PAM_SUCCESS;
}

static int
read_issue_quoted(pam_handle_t *pamh, FILE *fp, char **prompt)
{
    int c;
    size_t size = 1024;
    char *issue;
    struct utsname uts;

    *prompt = NULL;

    if ((issue = malloc(size)) == NULL) {
	pam_syslog(pamh, LOG_ERR, "out of memory");
	return PAM_BUF_ERR;
    }

    issue[0] = '\0';
    (void) uname(&uts);

    while ((c = getc(fp)) != EOF) {
	char buf[1024];

	buf[0] = '\0';
	if (c == '\\') {
	    if ((c = getc(fp)) == EOF)
		break;
	    switch (c) {
	      case 's':
		strncat(buf, uts.sysname, sizeof(buf) - 1);
		break;
	      case 'n':
		strncat(buf, uts.nodename, sizeof(buf) - 1);
		break;
	      case 'r':
		strncat(buf, uts.release, sizeof(buf) - 1);
		break;
	      case 'v':
		strncat(buf, uts.version, sizeof(buf) - 1);
		break;
	      case 'm':
		strncat(buf, uts.machine, sizeof(buf) - 1);
		break;
	      case 'o':
		{
		    char domainname[256];

		    if (getdomainname(domainname, sizeof(domainname)) >= 0) {
			domainname[sizeof(domainname)-1] = '\0';
			strncat(buf, domainname, sizeof(buf) - 1);
		    }
		}
		break;
	      case 'd':
	      case 't':
		{
		    const char *weekday[] = {
			"Sun", "Mon", "Tue", "Wed", "Thu",
			"Fri", "Sat" };
		    const char *month[] = {
			"Jan", "Feb", "Mar", "Apr", "May",
			"Jun", "Jul", "Aug", "Sep", "Oct",
			"Nov", "Dec" };
		    time_t now;
		    struct tm *tm;

		    (void) time (&now);
		    tm = localtime(&now);

		    if (c == 'd')
			snprintf (buf, sizeof buf, "%s %s %d  %d",
				weekday[tm->tm_wday], month[tm->tm_mon],
				tm->tm_mday, tm->tm_year + 1900);
		    else
			snprintf (buf, sizeof buf, "%02d:%02d:%02d",
				tm->tm_hour, tm->tm_min, tm->tm_sec);
		}
		break;
	      case 'l':
		{
		    char *ttyn = ttyname(1);
		    if (ttyn) {
			if (!strncmp(ttyn, "/dev/", 5))
			    ttyn += 5;
			strncat(buf, ttyn, sizeof(buf) - 1);
		    }
		}
		break;
	      case 'u':
	      case 'U':
		{
		    unsigned int users = 0;
		    struct utmp *ut;
		    setutent();
		    while ((ut = getutent())) {
			if (ut->ut_type == USER_PROCESS)
			    ++users;
		    }
		    endutent();
		    if (c == 'U')
			snprintf (buf, sizeof buf, "%u %s", users,
			          (users == 1) ? "user" : "users");
		    else
			snprintf (buf, sizeof buf, "%u", users);
		    break;
		}
	      default:
		buf[0] = c; buf[1] = '\0';
	    }
	} else {
	    buf[0] = c; buf[1] = '\0';
	}

	if ((strlen(issue) + strlen(buf)) + 1 > size) {
	    char *new_issue;

	    size += strlen(buf) + 1;
	    new_issue = (char *) realloc (issue, size);
	    if (new_issue == NULL) {
		_pam_drop(issue);
		return PAM_BUF_ERR;
	    }
	    issue = new_issue;
	    strcat(issue, buf);
	}
    }

    if (ferror(fp)) {
	pam_syslog(pamh, LOG_ERR, "read error: %m");
	_pam_drop(issue);
	return PAM_SERVICE_ERR;
    }

    *prompt = issue;
    return PAM_SUCCESS;
}

#ifdef PAM_STATIC

/* static module data */

struct pam_module _pam_issue_modstruct = {
     "pam_issue",
     pam_sm_authenticate,
     pam_sm_setcred,
     NULL,
     NULL,
     NULL,
     NULL,
};

#endif

/* end of module definition */