telnetd/libtelnet/sra.c

/* $FreeBSD$ */

#ifdef	SRA
#include <sys/types.h>
#include <arpa/telnet.h>
#include <stdio.h>
#ifdef	__STDC__
#include <stdlib.h>
#endif
#ifdef	NO_STRING_H
#include <strings.h>
#else
#include <string.h>
#endif

#if !defined(NOPAM)
#include <security/pam_appl.h>
#endif

#include <ttyent.h>

#include "auth.h"
#include "misc.h"
#include "encrypt.h"
#include "pk.h"

char pka[HEXKEYBYTES+1], ska[HEXKEYBYTES+1], pkb[HEXKEYBYTES+1];
char *user,*pass,*xuser,*xpass;
DesData ck;
IdeaData ik;

extern int auth_debug_mode;
extern char *line;

static sra_valid = 0;
static passwd_sent = 0;

static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
			  		AUTHTYPE_SRA, };

#define SRA_KEY	0
#define SRA_USER 1
#define SRA_CONTINUE 2
#define SRA_PASS 3
#define SRA_ACCEPT 4
#define SRA_REJECT 5

/* support routine to send out authentication message */
static int Data(ap, type, d, c)
Authenticator *ap;
int type;
void *d;
int c;
{
        unsigned char *p = str_data + 4;
	unsigned char *cd = (unsigned char *)d;

	if (c == -1)
		c = strlen((char *)cd);

        if (auth_debug_mode) {
                printf("%s:%d: [%d] (%d)",
                        str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
                        str_data[3],
                        type, c);
                printd(d, c);
                printf("\r\n");
        }
	*p++ = ap->type;
	*p++ = ap->way;
	*p++ = type;
        while (c-- > 0) {
                if ((*p++ = *cd++) == IAC)
                        *p++ = IAC;
        }
        *p++ = IAC;
        *p++ = SE;
	if (str_data[3] == TELQUAL_IS)
		printsub('>', &str_data[2], p - (&str_data[2]));
        return(net_write(str_data, p - str_data));
}

int sra_init(ap, server)
Authenticator *ap;
int server;
{
	if (server)
		str_data[3] = TELQUAL_REPLY;
	else
		str_data[3] = TELQUAL_IS;

	user = (char *)malloc(256);
	xuser = (char *)malloc(513);
	pass = (char *)malloc(256);
	xpass = (char *)malloc(513);

	if (user == NULL || xuser == NULL || pass == NULL || xpass ==
	NULL)
		return 0; /* malloc failed */

	passwd_sent = 0;
	
	genkeys(pka,ska);
	return(1);
}

/* client received a go-ahead for sra */
int sra_send(ap)
Authenticator *ap;
{
	/* send PKA */

	if (auth_debug_mode)
		printf("Sent PKA to server.\r\n" );
	printf("Trying SRA secure login:\r\n");
	if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
		if (auth_debug_mode)
			printf("Not enough room for authentication data\r\n");
		return(0);
	}

	return(1);
}

/* server received an IS -- could be SRA KEY, USER, or PASS */
void sra_is(ap, data, cnt)
Authenticator *ap;
unsigned char *data;
int cnt;
{
	int valid;
	Session_Key skey;

	if (cnt-- < 1)
		goto bad;
	switch (*data++) {

	case SRA_KEY:
		if (cnt < HEXKEYBYTES) {
			Data(ap, SRA_REJECT, (void *)0, 0);
			auth_finished(ap, AUTH_USER);
			if (auth_debug_mode) {
				printf("SRA user rejected for bad PKB\r\n");
			}
			return;
		}
		if (auth_debug_mode)
			printf("Sent pka\r\n");
		if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
			if (auth_debug_mode)
				printf("Not enough room\r\n");
			return;
		}
		memcpy(pkb,data,HEXKEYBYTES);
		pkb[HEXKEYBYTES] = '\0';
		common_key(ska,pkb,&ik,&ck);
		return;

	case SRA_USER:
		/* decode KAB(u) */
		if (cnt > 512) /* Attempted buffer overflow */
			break;
		memcpy(xuser,data,cnt);
		xuser[cnt] = '\0';
		pk_decode(xuser,user,&ck);
		auth_encrypt_user(user);
		Data(ap, SRA_CONTINUE, (void *)0, 0);

		return;

	case SRA_PASS:
		if (cnt > 512) /* Attempted buffer overflow */
			break;
		/* decode KAB(P) */
		memcpy(xpass,data,cnt);
		xpass[cnt] = '\0';
		pk_decode(xpass,pass,&ck);

		/* check user's password */
		valid = check_user(user,pass);

		if(valid) {
			Data(ap, SRA_ACCEPT, (void *)0, 0);
#ifdef DES_ENCRYPTION
			skey.data = ck;
			skey.type = SK_DES;
			skey.length = 8;
			encrypt_session_key(&skey, 1);
#endif

			sra_valid = 1;
			auth_finished(ap, AUTH_VALID);
			if (auth_debug_mode) {
				printf("SRA user accepted\r\n");
			}
		}
		else {
			Data(ap, SRA_CONTINUE, (void *)0, 0);
/*
			Data(ap, SRA_REJECT, (void *)0, 0);
			sra_valid = 0;
			auth_finished(ap, AUTH_REJECT);
*/
			if (auth_debug_mode) {
				printf("SRA user failed\r\n");
			}
		}
		return;

	default:
		if (auth_debug_mode)
			printf("Unknown SRA option %d\r\n", data[-1]);
	}
bad:
	Data(ap, SRA_REJECT, 0, 0);
	sra_valid = 0;
	auth_finished(ap, AUTH_REJECT);
}

extern char *getpass();

/* client received REPLY -- could be SRA KEY, CONTINUE, ACCEPT, or REJECT */
void sra_reply(ap, data, cnt)
Authenticator *ap;
unsigned char *data;
int cnt;
{
	extern char *telnet_gets();
	char uprompt[256],tuser[256];
	Session_Key skey;
	int i;

	if (cnt-- < 1)
		return;
	switch (*data++) {

	case SRA_KEY:
		/* calculate common key */
		if (cnt < HEXKEYBYTES) {
			if (auth_debug_mode) {
				printf("SRA user rejected for bad PKB\r\n");
			}
			return;
		}
		memcpy(pkb,data,HEXKEYBYTES);
		pkb[HEXKEYBYTES] = '\0';		

		common_key(ska,pkb,&ik,&ck);

	enc_user:

		/* encode user */
		memset(tuser,0,sizeof(tuser));
		sprintf(uprompt,"User (%s): ",UserNameRequested);
		telnet_gets(uprompt,tuser,255,1);
		if (tuser[0] == '\n' || tuser[0] == '\r' )
			strcpy(user,UserNameRequested);
		else {
			/* telnet_gets leaves the newline on */
			for(i=0;i<sizeof(tuser);i++) {
				if (tuser[i] == '\n') {
					tuser[i] = '\0';
					break;
				}
			}
			strcpy(user,tuser);
		}
		pk_encode(user,xuser,&ck);

		/* send it off */
		if (auth_debug_mode)
			printf("Sent KAB(U)\r\n");
		if (!Data(ap, SRA_USER, (void *)xuser, strlen(xuser))) {
			if (auth_debug_mode)
				printf("Not enough room\r\n");
			return;
		}
		break;

	case SRA_CONTINUE:
		if (passwd_sent) {
			passwd_sent = 0;
			printf("[ SRA login failed ]\r\n");
			goto enc_user;
		}
		/* encode password */
		memset(pass,0,sizeof(pass));
		telnet_gets("Password: ",pass,255,0);
		pk_encode(pass,xpass,&ck);
		/* send it off */
		if (auth_debug_mode)
			printf("Sent KAB(P)\r\n");
		if (!Data(ap, SRA_PASS, (void *)xpass, strlen(xpass))) {
			if (auth_debug_mode)
				printf("Not enough room\r\n");
			return;
		}
		passwd_sent = 1;
		break;

	case SRA_REJECT:
		printf("[ SRA refuses authentication ]\r\n");
		printf("Trying plaintext login:\r\n");
		auth_finished(0,AUTH_REJECT);
		return;

	case SRA_ACCEPT:
		printf("[ SRA accepts you ]\r\n");
#ifdef DES_ENCRYPTION
		skey.data = ck;
		skey.type = SK_DES;
		skey.length = 8;
		encrypt_session_key(&skey, 0);
#endif

		auth_finished(ap, AUTH_VALID);
		return;
	default:
		if (auth_debug_mode)
			printf("Unknown SRA option %d\r\n", data[-1]);
		return;
	}
}

int sra_status(ap, name, level)
Authenticator *ap;
char *name;
int level;
{
	if (level < AUTH_USER)
		return(level);
	if (UserNameRequested && sra_valid) {
		strcpy(name, UserNameRequested);
		return(AUTH_VALID);
	} else
		return(AUTH_USER);
}

#define	BUMP(buf, len)		while (*(buf)) {++(buf), --(len);}
#define	ADDC(buf, len, c)	if ((len) > 0) {*(buf)++ = (c); --(len);}

void sra_printsub(data, cnt, buf, buflen)
unsigned char *data, *buf;
int cnt, buflen;
{
	char lbuf[32];
	register int i;

	buf[buflen-1] = '\0';		/* make sure its NULL terminated */
	buflen -= 1;

	switch(data[3]) {

	case SRA_CONTINUE:
		strncpy((char *)buf, " CONTINUE ", buflen);
		goto common;

	case SRA_REJECT:		/* Rejected (reason might follow) */
		strncpy((char *)buf, " REJECT ", buflen);
		goto common;

	case SRA_ACCEPT:		/* Accepted (name might follow) */
		strncpy((char *)buf, " ACCEPT ", buflen);

	common:
		BUMP(buf, buflen);
		if (cnt <= 4)
			break;
		ADDC(buf, buflen, '"');
		for (i = 4; i < cnt; i++)
			ADDC(buf, buflen, data[i]);
		ADDC(buf, buflen, '"');
		ADDC(buf, buflen, '\0');
		break;

	case SRA_KEY:			/* Authentication data follows */
		strncpy((char *)buf, " KEY ", buflen);
		goto common2;

	case SRA_USER:
		strncpy((char *)buf, " USER ", buflen);
		goto common2;

	case SRA_PASS:
		strncpy((char *)buf, " PASS ", buflen);
		goto common2;

	default:
		sprintf(lbuf, " %d (unknown)", data[3]);
		strncpy((char *)buf, lbuf, buflen);
	common2:
		BUMP(buf, buflen);
		for (i = 4; i < cnt; i++) {
			sprintf(lbuf, " %d", data[i]);
			strncpy((char *)buf, lbuf, buflen);
			BUMP(buf, buflen);
		}
		break;
	}
}

struct	passwd *pw;

/*
 * Helper function for sgetpwnam().
 */
char *
sgetsave(s)
	char *s;
{
	char *new = malloc((unsigned) strlen(s) + 1);

	if (new == NULL) {
		return(NULL);
	}
	(void) strcpy(new, s);
	return (new);
}

#include <pwd.h>
#include <syslog.h>
#ifdef USE_SHADOW
#include <shadow.h>
#endif


struct passwd *
sgetpwnam(name)
	char *name;
{
	static struct passwd save;
	register struct passwd *p;
	char *sgetsave();

	if ((p = getpwnam(name)) == NULL)
		return (p);
	if (save.pw_name) {
		free(save.pw_name);
		free(save.pw_passwd);
		free(save.pw_gecos);
		free(save.pw_dir);
		free(save.pw_shell);
	}
	save = *p;
	save.pw_name = sgetsave(p->pw_name);
	save.pw_passwd = sgetsave(p->pw_passwd);
	save.pw_gecos = sgetsave(p->pw_gecos);
	save.pw_dir = sgetsave(p->pw_dir);
	save.pw_shell = sgetsave(p->pw_shell);
#if 0
syslog(LOG_WARNING,"%s\n",save.pw_name);
syslog(LOG_WARNING,"%s\n",save.pw_passwd);
syslog(LOG_WARNING,"%s\n",save.pw_gecos);
syslog(LOG_WARNING,"%s\n",save.pw_dir);
#endif
#ifdef USE_SHADOW
        {
                struct spwd *sp;
                sp = getspnam(name);
                free(save.pw_passwd);
                save.pw_passwd  = sgetsave(sp->sp_pwdp);
        }
#endif 
	return (&save);
}

static int
isroot(user)
char *user;
{
	struct passwd *pw;

	if ((pw=getpwnam(user))==NULL)
		return 0;
	return (!pw->pw_uid);
}

static int
rootterm(ttyn)
char *ttyn;
{
	struct ttyent *t;

	return ((t = getttynam(ttyn)) && t->ty_status & TTY_SECURE);
}

#ifdef NOPAM
char *crypt();

int check_user(name, pass)
char *name;
char *pass;
{
	register char *cp;
	char *xpasswd, *salt;

	if (isroot(name) && !rootterm(line))
	{
		crypt("AA","*"); /* Waste some time to simulate success */
		return(0);
	}

	if (pw = sgetpwnam(name)) {
		if (pw->pw_shell == NULL) {
			pw = (struct passwd *) NULL;
			return(0);
		}

		salt = pw->pw_passwd;
		xpasswd = crypt(pass, salt);
		/* The strcmp does not catch null passwords! */
		if (pw == NULL || *pw->pw_passwd == '\0' ||
			strcmp(xpasswd, pw->pw_passwd)) {
			pw = (struct passwd *) NULL;
			return(0);
		}
		return(1);
	}
	return(0);
}
#else

/*
 * The following is stolen from ftpd, which stole it from the imap-uw
 * PAM module and login.c. It is needed because we can't really
 * "converse" with the user, having already gone to the trouble of
 * getting their username and password through an encrypted channel.
 */

#define COPY_STRING(s) (s ? strdup(s):NULL)

struct cred_t {
	const char *uname;
	const char *pass;
};
typedef struct cred_t cred_t;

auth_conv(int num_msg, const struct pam_message **msg,
	struct pam_response **resp, void *appdata)
{
	int i;
	cred_t *cred = (cred_t *) appdata;
	struct pam_response *reply =
		malloc(sizeof(struct pam_response) * num_msg);

	if (reply == NULL)
		return PAM_BUF_ERR;

	for (i = 0; i < num_msg; i++) {
		switch (msg[i]->msg_style) {
		case PAM_PROMPT_ECHO_ON:        /* assume want user name */
			reply[i].resp_retcode = PAM_SUCCESS;
			reply[i].resp = COPY_STRING(cred->uname);
			/* PAM frees resp. */
			break;
		case PAM_PROMPT_ECHO_OFF:       /* assume want password */
			reply[i].resp_retcode = PAM_SUCCESS;
			reply[i].resp = COPY_STRING(cred->pass);
			/* PAM frees resp. */
			break;
		case PAM_TEXT_INFO:
		case PAM_ERROR_MSG:
			reply[i].resp_retcode = PAM_SUCCESS;
			reply[i].resp = NULL;
			break;
		default:                        /* unknown message style */
			free(reply);
			return PAM_CONV_ERR;
		}
	}

	*resp = reply;
	return PAM_SUCCESS;
}

/*
 * The PAM version as a side effect may put a new username in *name.
 */
int check_user(const char *name, const char *pass)
{
	pam_handle_t *pamh = NULL;
	const char *tmpl_user;
	const void *item;
	int rval;
	int e;
	cred_t auth_cred = { name, pass };
	struct pam_conv conv = { &auth_conv, &auth_cred };

	e = pam_start("telnetd", name, &conv, &pamh);
	if (e != PAM_SUCCESS) {
		syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, e));
		return 0;
	}

#if 0 /* Where can we find this value? */
	e = pam_set_item(pamh, PAM_RHOST, remotehost);
	if (e != PAM_SUCCESS) {
		syslog(LOG_ERR, "pam_set_item(PAM_RHOST): %s",
			pam_strerror(pamh, e));
		return 0;
	}
#endif

	e = pam_authenticate(pamh, 0);
	switch (e) {
	case PAM_SUCCESS:
		/*
		 * With PAM we support the concept of a "template"
		 * user.  The user enters a login name which is
		 * authenticated by PAM, usually via a remote service
		 * such as RADIUS or TACACS+.  If authentication
		 * succeeds, a different but related "template" name
		 * is used for setting the credentials, shell, and
		 * home directory.  The name the user enters need only
		 * exist on the remote authentication server, but the
		 * template name must be present in the local password
		 * database.
		 *
		 * This is supported by two various mechanisms in the
		 * individual modules.  However, from the application's
		 * point of view, the template user is always passed
		 * back as a changed value of the PAM_USER item.
		 */
		if ((e = pam_get_item(pamh, PAM_USER, &item)) ==
		    PAM_SUCCESS) {
			strcpy(name, (const char *) item);
		} else
			syslog(LOG_ERR, "Couldn't get PAM_USER: %s",
			pam_strerror(pamh, e));
		if (isroot(name) && !rootterm(line))
			rval = 0;
		else
			rval = 1;
		break;

	case PAM_AUTH_ERR:
	case PAM_USER_UNKNOWN:
	case PAM_MAXTRIES:
		rval = 0;
	break;

	default:
		syslog(LOG_ERR, "auth_pam: %s", pam_strerror(pamh, e));
		rval = 0;
		break;
	}

	if ((e = pam_end(pamh, e)) != PAM_SUCCESS) {
		syslog(LOG_ERR, "pam_end: %s", pam_strerror(pamh, e));
		rval = 0;
	}
	return rval;
}

#endif

#endif