/*-
 * Copyright (c) 1991, 1993
 *      Dave Safford.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 */

#include <sys/cdefs.h>
#ifdef notdef
__FBSDID("$FreeBSD: src/contrib/telnet/libtelnet/sra.c,v 1.16 2002/05/06 09:48:02 markm Exp $");
#else
__RCSID("$NetBSD: sra.c,v 1.12 2021/10/30 10:46:57 nia Exp $");
#endif

#ifdef  SRA
#ifdef  ENCRYPTION
#include <sys/types.h>
#include <arpa/telnet.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <ttyent.h>

#ifndef NOPAM
#include <security/pam_appl.h>
#else
#include <unistd.h>
#endif

#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;
char *passprompt, *xpassprompt;
DesData ck;
IdeaData ik;

extern int auth_debug_mode;
extern char *line;              /* see sys_term.c */

static int sra_valid = 0;
static int passwd_sent = 0;

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

#define SMALL_LEN       256
#define XSMALL_LEN      513
#define SRA_KEY 0
#define SRA_USER 1
#define SRA_CONTINUE 2
#define SRA_PASS 3
#define SRA_ACCEPT 4
#define SRA_REJECT 5

static int check_user(char *, const char *);

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

        if (c == -1)
                c = strlen(d);

        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 telnet_net_write(str_data, p - str_data);
}

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

        user = malloc(SMALL_LEN);
        xuser = malloc(XSMALL_LEN);
        pass = malloc(SMALL_LEN);
        xpass = malloc(XSMALL_LEN);
        passprompt = malloc(SMALL_LEN);
        xpassprompt = malloc(XSMALL_LEN);

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

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

/* client received a go-ahead for sra */
int
sra_send(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(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 > XSMALL_LEN - 1) /* Attempted buffer overflow */
                        break;
                memcpy(xuser, data, cnt);
                xuser[cnt] = '\0';
                pk_decode(xuser, user, &ck);
                auth_encrypt_user(user);
#ifndef NOPAM
                (void)check_user(user, "*");
#endif
                pk_encode(passprompt, xpassprompt, &ck);
                Data(ap, SRA_CONTINUE, xpassprompt, XSMALL_LEN - 1);

                return;

        case SRA_PASS:
                if (cnt > XSMALL_LEN - 1) /* 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) {
                        /* PAM (via check_user()) may have changed 'user' */
                        auth_encrypt_user(user);
                        Data(ap, SRA_ACCEPT, (void *)0, 0);
                        skey.data = ck;
                        skey.type = SK_DES;
                        skey.length = 8;
                        encrypt_session_key(&skey, 1);

                        sra_valid = 1;
                        auth_finished(ap, AUTH_VALID);
                        if (auth_debug_mode) {
                                printf("SRA user accepted\r\n");
                        }
                }
                else {
                        pk_encode(passprompt, xpassprompt, &ck);
                        Data(ap, SRA_CONTINUE, (void *)xpassprompt,
                            XSMALL_LEN - 1);
                        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);
}

/* client received REPLY -- could be SRA KEY, CONTINUE, ACCEPT, or REJECT */
void
sra_reply(Authenticator *ap, unsigned char *data, int cnt)
{
        char uprompt[SMALL_LEN], tuser[SMALL_LEN];
        Session_Key skey;
        size_t 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));
                snprintf(uprompt, sizeof(uprompt), "User (%s): ",
                    UserNameRequested);
                if (telnet_gets(uprompt, tuser, SMALL_LEN - 1, 1) == NULL) {
                        printf("\n");
                        exit(1);
                }
                if (tuser[0] == '\n' || tuser[0] == '\r' )
                        strlcpy(user, UserNameRequested, SMALL_LEN);
                else {
                        /* telnet_gets leaves the newline on */
                        for(i = 0; i < sizeof(tuser); i++) {
                                if (tuser[i] == '\n') {
                                        tuser[i] = '\0';
                                        break;
                                }
                        }
                        strlcpy(user, tuser, SMALL_LEN);
                }
                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;
                }
                if (cnt > XSMALL_LEN - 1) { 
                        break;
                } else if (cnt > 0) {
                        (void)memcpy(xpassprompt, data, cnt);
                        pk_decode(xpassprompt, passprompt, &ck);
                } else {
                        (void)strlcpy(passprompt, "Password: ", SMALL_LEN);
                }
                /* encode password */
                memset(pass, 0, SMALL_LEN);
                if (telnet_gets(passprompt, pass, SMALL_LEN - 1, 0) == NULL) {
                        printf("\n");
                        exit(1);
                }
                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");
                skey.data = ck;
                skey.type = SK_DES;
                skey.length = 8;
                encrypt_session_key(&skey, 0);

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

int
sra_status(Authenticator *ap __unused, char *name, size_t len, int level)
{
        if (level < AUTH_USER)
                return level;
        if (UserNameRequested && sra_valid) {
                strlcpy(name, UserNameRequested, len);
                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(unsigned char *data, int cnt, unsigned char *ubuf, int buflen)
{
        char lbuf[32], *buf = (char *)ubuf;
        int i;

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

        switch(data[3]) {

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

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

        case SRA_ACCEPT:                /* Accepted (name might follow) */
                strncpy(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(buf, " KEY ", buflen);
                goto common2;

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

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

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

#ifdef NOPAM
static int
isroot(const char *usr)
{
        struct passwd pws, *pwd;
        char pwbuf[1024];

        if (getpwnam_r(usr, &pws, pwbuf, sizeof(pwbuf), &pwd) != 0 ||
            pwd == NULL)
                return 0;
        return (!pwd->pw_uid);
}

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

        ttyn = ttyname;
        if (strncmp(ttyn, _PATH_DEV, sizeof(_PATH_DEV) - 1) == 0)
                ttyn += sizeof(_PATH_DEV) - 1;

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

static int
check_user(char *name, const char *cred)
{
        struct passwd pws, *pw;
        char pwbuf[1024];
        char *xpasswd, *salt;

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

        if (getpwnam_r(name, &pws, pwbuf, sizeof(pwbuf), &pw) == 0 &&
            pw != NULL) {
                if (pw->pw_shell == NULL) {
                        return 0;
                }

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

/*
 * 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;

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

        if (reallocarr(&reply, num_msg, sizeof(*reply)) != 0)
                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 */
                    (void)strlcpy(passprompt, msg[i]->msg, SMALL_LEN);
                    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.
 */
static int
check_user(char *name, const char *cred)
{
        pam_handle_t *pamh = NULL;
        const void *item;
        int rval;
        int e;
        cred_t auth_cred = { name, cred };
        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) {
                        strlcpy(name, item, SMALL_LEN);
                } else
                        syslog(LOG_ERR, "Couldn't get PAM_USER: %s",
                        pam_strerror(pamh, e));
#if 0   /* pam_securetty(8) should be used to enforce this */
                if (isroot(name) && !rootterm(line))
                        rval = 0;
                else
#endif
                        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 /* !NOPAM */

#endif /* ENCRYPTION */
#endif /* SRA */