/*
   SMArT

   Check username/password combination using PAM and require membership in
   the configured SMArT administrator Unix group.

   Usage:
     check_login <user> <password> <admin-group> [smart.conf]

   Passwords are never written to the log.
*/

#include <ctype.h>
#include <errno.h>
#include <grp.h>
#include <pwd.h>
#include <security/pam_appl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

#include "config.h"

int my_conv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata_ptr);
static int user_in_group(const char *username, const char *groupname);


#define SMART_LOG_ERROR   0
#define SMART_LOG_WARNING 1
#define SMART_LOG_INFO    2
#define SMART_LOG_DEBUG   3
#define SMART_LOG_TRACE   4

typedef struct {
	char log_path[512];
	char debug_level[64];
	char admin_group[256];
	int level;
} smart_helper_config_t;

static void trim(char *s)
{
	char *p = s;
	size_t len;

	while (*p && isspace((unsigned char)*p)) {
		p++;
	}

	if (p != s) {
		memmove(s, p, strlen(p) + 1);
	}

	len = strlen(s);
	while (len > 0 && isspace((unsigned char)s[len - 1])) {
		s[len - 1] = '\0';
		len--;
	}
}

static void strip_quotes(char *s)
{
	size_t len = strlen(s);

	if (len >= 2) {
		if ((s[0] == '\'' && s[len - 1] == '\'') ||
		    (s[0] == '"'  && s[len - 1] == '"')) {
			memmove(s, s + 1, len - 2);
			s[len - 2] = '\0';
		}
	}
}

static int parse_perl_assignment(const char *line, char *key, size_t ksz, char *val, size_t vsz)
{
	const char *p = line;
	size_t ki = 0;
	size_t vi = 0;

	while (*p && isspace((unsigned char)*p)) {
		p++;
	}
	if (*p != '$') {
		return 0;
	}
	p++;

	while (*p && (isalnum((unsigned char)*p) || *p == '_')) {
		if (ki + 1 < ksz) {
			key[ki++] = *p;
		}
		p++;
	}
	key[ki] = '\0';

	while (*p && isspace((unsigned char)*p)) {
		p++;
	}
	if (*p != '=') {
		return 0;
	}
	p++;

	while (*p && isspace((unsigned char)*p)) {
		p++;
	}

	while (*p && *p != ';' && *p != '\n' && *p != '\r') {
		if (vi + 1 < vsz) {
			val[vi++] = *p;
		}
		p++;
	}
	val[vi] = '\0';

	trim(key);
	trim(val);
	strip_quotes(val);

	return key[0] != '\0';
}

static int parse_log_level(const char *value)
{
	char buf[64];
	size_t i;

	if (value == NULL || value[0] == '\0') {
		return SMART_LOG_INFO;
	}

	snprintf(buf, sizeof(buf), "%s", value);
	trim(buf);

	for (i = 0; buf[i]; i++) {
		buf[i] = (char)tolower((unsigned char)buf[i]);
	}

	if (strcmp(buf, "error") == 0 || strcmp(buf, "err") == 0 || strcmp(buf, "0") == 0) {
		return SMART_LOG_ERROR;
	}
	if (strcmp(buf, "warning") == 0 || strcmp(buf, "warn") == 0 || strcmp(buf, "1") == 0) {
		return SMART_LOG_WARNING;
	}
	if (strcmp(buf, "info") == 0 || strcmp(buf, "2") == 0) {
		return SMART_LOG_INFO;
	}
	if (strcmp(buf, "debug") == 0 || strcmp(buf, "3") == 0) {
		return SMART_LOG_DEBUG;
	}
	if (strcmp(buf, "trace") == 0 || strcmp(buf, "4") == 0) {
		return SMART_LOG_TRACE;
	}

	return SMART_LOG_INFO;
}

static const char *level_name(int level)
{
	if (level <= SMART_LOG_ERROR) {
		return "ERROR";
	}
	if (level == SMART_LOG_WARNING) {
		return "WARNING";
	}
	if (level == SMART_LOG_DEBUG) {
		return "DEBUG";
	}
	if (level >= SMART_LOG_TRACE) {
		return "TRACE";
	}
	return "INFO";
}

static void smart_cfg_init(smart_helper_config_t *cfg)
{
	memset(cfg, 0, sizeof(*cfg));
	snprintf(cfg->log_path, sizeof(cfg->log_path), "%s", DEFAULT_SMART_LOG_PATH);
	snprintf(cfg->debug_level, sizeof(cfg->debug_level), "%s", DEFAULT_SMART_LOG_LEVEL);
	snprintf(cfg->admin_group, sizeof(cfg->admin_group), "%s", "root");
	cfg->level = parse_log_level(cfg->debug_level);
}

static void smart_cfg_load(smart_helper_config_t *cfg, const char *path)
{
	FILE *fh;
	char line[2048];

	if (path == NULL || path[0] == '\0') {
		return;
	}

	fh = fopen(path, "r");
	if (fh == NULL) {
		return;
	}

	while (fgets(line, sizeof(line), fh) != NULL) {
		char key[256];
		char val[1024];

		if (!parse_perl_assignment(line, key, sizeof(key), val, sizeof(val))) {
			continue;
		}

		if (strcmp(key, "smart_log_path") == 0) {
			snprintf(cfg->log_path, sizeof(cfg->log_path), "%s", val);
		} else if (strcmp(key, "smart_debug_level") == 0 ||
		           strcmp(key, "smart_log_level") == 0) {
			snprintf(cfg->debug_level, sizeof(cfg->debug_level), "%s", val);
			cfg->level = parse_log_level(val);
		} else if (strcmp(key, "smart_admin_group") == 0) {
			snprintf(cfg->admin_group, sizeof(cfg->admin_group), "%s", val);
		}
	}

	fclose(fh);
}

static void helper_log(smart_helper_config_t *cfg, const char *component, int level, const char *fmt, ...)
{
	FILE *fh = stderr;
	int close_fh = 0;
	time_t now;
	struct tm tm_now;
	char tbuf[64];
	va_list ap;

	if (cfg != NULL && level > cfg->level) {
		return;
	}

	if (cfg != NULL && cfg->log_path[0] != '\0') {
		fh = fopen(cfg->log_path, "a");
		if (fh != NULL) {
			close_fh = 1;
		} else {
			fh = stderr;
		}
	}

	now = time(NULL);
	localtime_r(&now, &tm_now);
	strftime(tbuf, sizeof(tbuf), "%Y-%m-%d %H:%M:%S", &tm_now);

	fprintf(fh, "[%s] [%s] [SMArT helper] [%s] ", tbuf, level_name(level), component);

	va_start(ap, fmt);
	vfprintf(fh, fmt, ap);
	va_end(ap);

	fputc('\n', fh);
	fflush(fh);

	if (close_fh) {
		fclose(fh);
	}
}


static struct pam_conv conv = {
	my_conv,
	NULL
};

char *user;
char *pass;

int main( int argc, char **argv )
{
	pam_handle_t *pamh = NULL;
	int retval, st = 1;
	const char *admin_group;
	const char *smart_conf = DEFAULT_SMART_CONF;
	smart_helper_config_t cfg;

	smart_cfg_init(&cfg);

	if( argc < 4 )
	{
		fprintf( stderr, "Usage: %s <user> <password> <admin-group> [smart.conf]\n", argv[0] );
		return( 3 );
	}

	user = argv[1];
	pass = argv[2];
	admin_group = argv[3];

	if (argc >= 5 && argv[4] != NULL && argv[4][0] != '\0') {
		smart_conf = argv[4];
	}

	smart_cfg_load(&cfg, smart_conf);

	if (admin_group == NULL || admin_group[0] == '\0' || strcmp(admin_group, "-") == 0) {
		admin_group = cfg.admin_group;
	}

	if( user == NULL || user[0] == '\0' ||
	    pass == NULL ||
	    admin_group == NULL || admin_group[0] == '\0' )
	{
		helper_log(&cfg, "check_login", SMART_LOG_ERROR, "invalid helper arguments");
		return( 3 );
	}

	helper_log(&cfg, "check_login", SMART_LOG_INFO, "authentication requested user='%s' admin_group='%s'", user, admin_group);

	retval = pam_start( "smart", user, &conv, &pamh );
	if( retval == PAM_SUCCESS )
		retval = pam_authenticate( pamh, PAM_SILENT );
	if( retval == PAM_SUCCESS )
		st = retval = pam_acct_mgmt( pamh, PAM_SILENT );

	if( pamh != NULL && pam_end( pamh, retval ) != PAM_SUCCESS ) {
		helper_log(&cfg, "check_login", SMART_LOG_ERROR, "pam_end failed user='%s'", user);
		return( 1 );
	}

	if( st != PAM_SUCCESS ) {
		helper_log(&cfg, "check_login", SMART_LOG_WARNING, "pam authentication failed user='%s' pam_status=%d", user, st);
		return( 1 );
	}

	helper_log(&cfg, "check_login", SMART_LOG_DEBUG, "pam authentication ok user='%s'", user);

	if( ! user_in_group( user, admin_group ) ) {
		helper_log(&cfg, "check_login", SMART_LOG_WARNING, "group authorization failed user='%s' required_group='%s'", user, admin_group);
		return( 2 );
	}

	helper_log(&cfg, "check_login", SMART_LOG_INFO, "login accepted user='%s' required_group='%s'", user, admin_group);

	return( 0 );
}

static int user_in_group(const char *username, const char *groupname)
{
	struct passwd *pw;
	struct group *gr;
	int ngroups = 0;
	gid_t *groups;
	int i;

	if( username == NULL || username[0] == '\0' ||
	    groupname == NULL || groupname[0] == '\0' )
	{
		return( 0 );
	}

	pw = getpwnam( username );
	gr = getgrnam( groupname );

	if( pw == NULL || gr == NULL )
	{
		return( 0 );
	}

	if( pw->pw_gid == gr->gr_gid )
	{
		return( 1 );
	}

#if defined(__linux__) || defined(__GLIBC__)
	getgrouplist( username, pw->pw_gid, NULL, &ngroups );

	if( ngroups > 0 )
	{
		groups = calloc( (size_t) ngroups, sizeof( gid_t ) );

		if( groups != NULL )
		{
			if( getgrouplist( username, pw->pw_gid, groups, &ngroups ) >= 0 )
			{
				for( i = 0; i < ngroups; i++ )
				{
					if( groups[i] == gr->gr_gid )
					{
						free( groups );
						return( 1 );
					}
				}
			}

			free( groups );
		}
	}
#endif

	if( gr->gr_mem != NULL )
	{
		for( i = 0; gr->gr_mem[i] != NULL; i++ )
		{
			if( strcmp( gr->gr_mem[i], username ) == 0 )
			{
				return( 1 );
			}
		}
	}

	return( 0 );
}

int my_conv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata_ptr)
{
	struct pam_response *reply;
	int i;

	(void) msg;
	(void) appdata_ptr;

	reply = (struct pam_response *) calloc( (size_t) num_msg, sizeof( struct pam_response ) );
	if( reply == NULL )
	{
		return( PAM_BUF_ERR );
	}

	for( i = 0; i < num_msg; i ++ )
	{
		reply[i].resp = (char *) strdup( pass );
		reply[i].resp_retcode = 0;
	}

	*resp = reply;

	return( PAM_SUCCESS );
}