path: root/modules/pam_unix/pam_unix.c

#define _XOPEN_SOURCE

#include <pwd.h> 
#include <netdb.h>
#include <shadow.h>  
#include <sys/types.h>
#include <unistd.h>
#include <time.h>
#include <string.h>


#ifndef MAXHOSTNAMELEN
# define MAXHOSTNAMELEN 256
#endif

#define PAM_SM_AUTH
#define PAM_SM_ACCOUNT
#define PAM_PASSWORD

#ifndef __linux__
#include <login_cap.h>
#endif


#define PASSWORD_HASH           "md5"
#define MAX_RETRIES 		3
#define DEFAULT_WARN            (2L * 7L * 86400L) /* two weeks */
#define SALTSIZE                32


#include <security/pam_modules.h>
#include <security/pam_appl.h>
#include <security/pam_mod_misc.h>

/*
 * User authentication
 */

PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags,
		int argc , const char **argv ) {

#ifndef __linux__
	login_cap_t *lc;
#endif
	struct passwd *pwd;
	const char *pass, *crypt_pass, *user;
	int pam_err;

	/* identify user */

	if (openpam_get_option(pamh, PAM_OPT_AUTH_AS_SELF)) {
		PAM_LOG("Authenticating as self.");
		pwd = getpwnam(getlogin());
	} else {
		if ((pam_err = pam_get_user(pamh, &user, NULL)) != PAM_SUCCESS) {
			PAM_ERROR("Authenticating with uname [%s] failed.", user);
	                return (pam_err);
		}

	        pwd = getpwnam(user);
	}
	
	PAM_LOG("Authenticating user: [%s]", user);

	/* get password */

	if (pwd != NULL) {
		PAM_LOG("Doing real authentication");
	        pass = pwd->pw_passwd;
		if (pass[0] == '\0') {
			if (!(flags & PAM_DISALLOW_NULL_AUTHTOK) &&
					openpam_get_option(pamh, PAM_OPT_NULLOK)){
				PAM_ERROR("Authentication failed. Empty passwd not allowed.");
				return (PAM_SUCCESS);
			}
			
			pass = "*";
		}
#ifndef __linux__
		lc = login_getpwclass(pwd);
#endif
	} else {
		PAM_LOG("Doing dummy authentication.");
		pass =  "*";
#ifndef __linux__     
		lc = login_getpwclass(NULL);
#endif
	}

#ifndef __linux__
        prompt = login_getcapstr(lc, "passwd_prompt", NULL, NULL);
        pam_err = pam_get_authtok(pamh, PAM_AUTHTOK, &pass, prompt);
        login_close(lc);
#else
	pam_err = pam_get_authtok(pamh, PAM_AUTHTOK, (const char **) &pass, NULL);
#endif
	PAM_LOG("Got password for user [%s]", user);

        if (pam_err == PAM_CONV_ERR)
                return (pam_err);
	if (pam_err != PAM_SUCCESS)
	        return (PAM_AUTH_ERR);
	
	/* check passwd entry */
	
	crypt_pass = crypt(pass, pwd->pw_passwd); 
	if ( strcmp(crypt_pass, pwd->pw_passwd) != 0 ) {
		PAM_ERROR("Wrong password. Authentication failed.");
		pam_err = PAM_AUTH_ERR;
	} else {
		PAM_LOG("Authentication completed succesfully.");
		pam_err = PAM_SUCCESS;
	}

	return (pam_err);
}

PAM_EXTERN int
pam_sm_setcred(pam_handle_t *pamh , int flags ,
		    int argc , const char *argv[] ) {
	
	/* 
	 * This functions takes care of renewing/initializing
	 * user credentials as well as gid/uids. Someday, it
	 * will be completed. For now, it's not very urgent. 
	 */

	return (PAM_SUCCESS);
}


/*
 * Account Management
 */

PAM_EXTERN int
pam_sm_acct_mgmt(pam_handle_t *pamh, int flags ,
		    int argc , const char *argv[] ) {



#ifndef __linux__
	login_cap_t *lc;
#endif

	struct spwd *pwd;
	int pam_err;
	const char *user;
	time_t curtime;
	
#ifndef __linux__
	const void *rhost, *tty;
	char rhostip[MAXHOSTNAMELEN] = "";
#endif

	/* Sanity checks for uname,pwd,tty,host etc */

	pam_err = pam_get_user(pamh, &user, NULL);

	if (pam_err != PAM_SUCCESS)
		return (pam_err);

	if (user == NULL || (pwd = getpwnam(user)) == NULL)
		return (PAM_SERVICE_ERR);


	PAM_LOG("Got user [%s]" , user );
#ifndef __linux__

	/* 
	 * tty/host info are provided by login classes
	 * and cannot be used out of the box under Linux
	 * for sanity checking (BSD only). May need to 
	 * be ported/rewritten to work on Linux as well.
	 * Time will tell...
	 */
	pam_err = pam_get_item(pamh, PAM_RHOST, &rhost);

	if (pam_err != PAM_SUCCESS)
		return (pam_err);

	pam_err = pam_get_item(pamh, PAM_TTY, &tty);

	if (pam_err != PAM_SUCCESS)
		return (pam_err);
#endif
	if (*pwd->sp_pwdp == '\0' &&
         	(flags & PAM_DISALLOW_NULL_AUTHTOK) != 0)
		return (PAM_NEW_AUTHTOK_REQD);

#ifndef __linux__
	lc = login_getpwclass(pwd);
	
	if (lc == NULL) {
		PAM_ERROR("Unable to get login class for user [%s]");
		return (PAM_SERVICE_ERR);		
	}
#endif
	/* Check if pw_lstchg or sp_expire is set */

	if (pwd->sp_lstchg || pwd->sp_expire) 
		curtime = time(NULL) / (60 * 60 * 24);
	if (pwd->sp_expire) {
		if ( (curtime > pwd->sp_expire ) && ( pwd->sp_expire != -1 ) ) {  
#ifndef __linux__ 		
			login_close(lc);
#endif	
			PAM_ERROR("Account has expired!");
			return (PAM_ACCT_EXPIRED);
		} else if ( ( pwd->sp_expire - curtime < DEFAULT_WARN) ) {
			PAM_ERROR(pamh, "Warning: your account expires on %s",
					ctime(&pwd->sp_expire));
		}
	}

	if (pwd->sp_lstchg == 0 ) {
		return (PAM_NEW_AUTHTOK_REQD);
	}
	
	/* check all other possibilities (mostly stolen from pam_tcb) */
	
	if ((curtime > (pwd->sp_lstchg + pwd->sp_max + pwd->sp_inact)) &&
			(pwd->sp_max != -1) && (pwd->sp_inact != -1) &&
			(pwd->sp_lstchg != 0)) {
		PAM_ERROR("Account has expired!");
		return (PAM_ACCT_EXPIRED);
	}
	
	if (((pwd->sp_lstchg + pwd->sp_max) < curtime) &&
		        (pwd->sp_max != -1)) {
		PAM_ERROR("Account has expired!");
		return (PAM_ACCT_EXPIRED);
	}

	if ((curtime - pwd->sp_lstchg > pwd->sp_max)
			&& (curtime - pwd->sp_lstchg > pwd->sp_inact)
			&& (curtime - pwd->sp_lstchg > pwd->sp_max + pwd->sp_inact)
			&& (pwd->sp_max != -1) && (pwd->sp_inact != -1)) {
		PAM_ERROR("Account has expired!");
		return (PAM_ACCT_EXPIRED);
	}

	pam_err = (PAM_SUCCESS);

#ifndef __linux__

	/* validate tty/host/time */

	if (!auth_hostok(lc, rhost, rhostip) ||
			!auth_ttyok(lc, tty) ||
			!auth_timeok(lc, time(NULL)))
		pam_err = PAM_AUTH_ERR;


	login_close(lc);
#endif

	return (pam_err);

}

/*
 * Password Management
 */

PAM_EXTERN int 
pam_sm_chautok(pam_handle_t *pamh, int flags,
		int argc, const char *argv[]) 
{

	/* 
	 * NIS support will be left for future implementation.
	 * This is standard unix passwd changing function. 
	 */
	struct passwd *new_pwd, *old_pwd;
        const char *user, *old_pass, *new_pass;
        char  *hashedpwd ;
#ifndef __linux__
	login_cap_t * lc;
#endif
	int pam_err, retries;

	/* identify user */

	if (openpam_get_option(pamh, PAM_OPT_AUTH_AS_SELF)) {
		PAM_LOG("Authenticating as self.");
		old_pwd = getpwnam(getlogin());
	} else {
		if ((pam_err = pam_get_user(pamh, &user, NULL)) != PAM_SUCCESS) {
			PAM_ERROR("Authenticating with uname [%s] failed.", user);
	                return (pam_err);
		}

	        old_pwd = getpwnam(user);
	}
	
	PAM_LOG("Got user: [%s]", user);

	if (old_pwd == NULL) {
		PAM_ERROR("User [%s] either has a corrupted passwd entry or \
				is not in the selected database", user);
                return (PAM_AUTHTOK_RECOVERY_ERR);
	}

	/*
	 * When looking through the LinuxPAM code, I came across this : 
	 *
	 * ` Various libraries at various times have had bugs related to
	 * '+' or '-' as the first character of a user name. Don't
	 * allow them. `
	 *
	 * I don't know if the problem is still around but just in case... 
	 */

	if (user == NULL || user[0] == '-' || user[0] == '+' ) { 
		PAM_ERROR("Bad username [%s]", user);
		return (PAM_USER_UNKNOWN);
	}



	if (flags & PAM_PRELIM_CHECK) {
		PAM_LOG("Doing preliminary actions.");

		if (getuid() == 0 ) { 
			/* root doesn't need old passwd */
			return (pam_set_item(pamh, PAM_OLDAUTHTOK, ""));
		}

		if ( (old_pwd->pw_passwd[0] == '\0' ) &&
			( openpam_get_option(pamh, PAM_OPT_NULLOK) ) &&
			!(flags & PAM_DISALLOW_NULL_AUTHTOK) ) {		
			/*
			 * Something funny could happen here since we don't 
			 * ask for a password.
			 */
			old_pass = "";
		} else { 
			pam_err = pam_get_authtok(pamh,PAM_OLDAUTHTOK, 
					&old_pass, NULL);
			if (pam_err != PAM_SUCCESS ) 
				return (pam_err);

		} 
		
		PAM_LOG("Got old token for user [%s].",user);
		
		hashedpwd = crypt(old_pass, old_pwd->pw_passwd);
		
		if (old_pass[0] == '\0' && !openpam_get_option(pamh, PAM_OPT_NULLOK))
			return (PAM_PERM_DENIED);
		
		if (strcmp(hashedpwd, old_pwd->pw_passwd) != 0)
			return (PAM_PERM_DENIED);

	} else if ( flags & PAM_UPDATE_AUTHTOK ) {

		PAM_LOG("Doing actual update.");

		pam_err= pam_get_authtok(pamh, PAM_OLDAUTHTOK ,&old_pass, NULL);
                
		if (pam_err != PAM_SUCCESS)
			return (pam_err);
		
		PAM_LOG("Got old password");

		retries = 0;
		pam_err = PAM_AUTHTOK_ERR;

		while ((pam_err != PAM_SUCCESS) && ( retries++ < MAX_RETRIES)) {
			
			pam_err = pam_get_authtok(pamh, PAM_AUTHTOK,
					&new_pass, NULL);

			pam_error(pamh, "Unable to get new passwd. Please \
					 try again");

		}
		
		if (pam_err != PAM_SUCCESS) {
			PAM_ERROR("Unable to get new password!");
			return (pam_err);
		}

		PAM_LOG("Got new password");
		
		/* 
		 * checking has to be done (?) for the new passwd to 
		 * verify it's not weak. 
		 */
		
		if (getuid() != 0 && new_pass[0] == '\0' &&
				!openpam_get_option(pamh, PAM_OPT_NULLOK))
			return (PAM_PERM_DENIED);



		
#ifndef __linux__

		/*
		 * The BSD way to update the passwd entry. Taken as is 
		 * from the freebsd-lib module pam_unix. Unfortunately, 
		 * the following won't work under Linux. 
		 */

		if ((new_pwd = pw_dup(old_pwd)) == NULL) 
			return (PAM_BUF_ERR);

		new_pwd->pw_change = 0;
		lc = login_getclass(new_pwd->pw_class);
		if (login_setcryptfmt(lc, password_hash, NULL) == NULL)
			openpam_log(PAM_LOG_ERROR,
				"can't set password cipher, relying on default");
		
		login_close(lc);
		makesalt(salt);
		new_pwd->pw_passwd = crypt(new_pass, salt);


		pam_err = PAM_SERVICE_ERR;
		if (pw_init(NULL, NULL))
			openpam_log(PAM_LOG_ERROR, "pw_init() failed");
		else if ((pfd = pw_lock()) == -1)
			openpam_log(PAM_LOG_ERROR, "pw_lock() failed");
		else if ((tfd = pw_tmp(-1)) == -1)
			openpam_log(PAM_LOG_ERROR, "pw_tmp() failed");
		else if (pw_copy(pfd, tfd, new_pwd, old_pwd) == -1)
			openpam_log(PAM_LOG_ERROR, "pw_copy() failed");
		else if (pw_mkdb(new_pwd->pw_name) == -1)
			openpam_log(PAM_LOG_ERROR, "pw_mkdb() failed");
		else
			pam_err = PAM_SUCCESS;
		pw_fini();
		
		free(old_pwd);
#endif

		/* Update shadow/passwd entries for Linux */


	} else {
		pam_err = PAM_ABORT;
		PAM_ERROR("Unrecognized flags.");
		return (pam_err);
	}
			


	return (PAM_SUCCESS);


}


/* 
 * Mostly stolen from freebsd-lib's pam_unix module which was mostly 
 * stolen from passwd(1)'s local_passwd.c
 *
 * Good ideas are meant to be reused ;)
 */

static unsigned char itoa64[] =         /* 0 ... 63 => ascii - 64 */
        "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

static void to64(char *s, long v, int n) {
	        while (--n >= 0) {
			*s++ = itoa64[v&0x3f];
			v >>= 6;
		}
}

/* Salt suitable for traditional DES and MD5 */
void
makesalt(char salt[SALTSIZE]) {
	        int i;
		/* These are not really random numbers, they are just
		 * numbers that change to thwart construction of a
		 * dictionary. This is exposed to the public.
		 */
		
		for (i = 0; i < SALTSIZE; i += 4)
//			to64(&salt[i], arc4random(), 4);
		salt[SALTSIZE] = '\0';
}

PAM_MODULE_ENTRY("pam_unix")