kerberos5.c

经典的unix下telnetd代码

	ret = krb5_auth_con_getremotesubkey (context,
					     auth_context,
					     &key_block);

	if (ret) {
	    Data(ap, KRB_REJECT, "krb5_auth_con_getremotesubkey failed", -1);
	    auth_finished(ap, AUTH_REJECT);
	    if (auth_debug_mode)
		printf("Kerberos V5: "
		       "krb5_auth_con_getremotesubkey failed (%s)\r\n",
		       krb5_get_err_text(context, ret));
	    return;
	}

	if (key_block == NULL) {
	    ret = krb5_auth_con_getkey(context,
				       auth_context,
				       &key_block);
	}
	if (ret) {
	    Data(ap, KRB_REJECT, "krb5_auth_con_getkey failed", -1);
	    auth_finished(ap, AUTH_REJECT);
	    if (auth_debug_mode)
		printf("Kerberos V5: "
		       "krb5_auth_con_getkey failed (%s)\r\n",
		       krb5_get_err_text(context, ret));
	    return;
	}
	if (key_block == NULL) {
	    Data(ap, KRB_REJECT, "no subkey received", -1);
	    auth_finished(ap, AUTH_REJECT);
	    if (auth_debug_mode)
		printf("Kerberos V5: "
		       "krb5_auth_con_getremotesubkey returned NULL key\r\n");
	    return;
	}

	if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
	    ret = krb5_mk_rep(context, auth_context, &outbuf);
	    if (ret) {
		Data(ap, KRB_REJECT,
		     "krb5_mk_rep failed", -1);
		auth_finished(ap, AUTH_REJECT);
		if (auth_debug_mode)
		    printf("Kerberos V5: "
			   "krb5_mk_rep failed (%s)\r\n",
			   krb5_get_err_text(context, ret));
		return;
	    }
	    Data(ap, KRB_RESPONSE, outbuf.data, outbuf.length);
	}
	if (krb5_unparse_name(context, ticket->client, &name))
	    name = 0;

	if(UserNameRequested && krb5_kuserok(context,
					     ticket->client,
					     UserNameRequested)) {
	    Data(ap, KRB_ACCEPT, name, name ? -1 : 0);
	    if (auth_debug_mode) {
		printf("Kerberos5 identifies him as ``%s''\r\n",
		       name ? name : "");
	    }

	    if(key_block->keytype == ETYPE_DES_CBC_MD5 ||
	       key_block->keytype == ETYPE_DES_CBC_MD4 ||
	       key_block->keytype == ETYPE_DES_CBC_CRC) {
		Session_Key skey;

		skey.type = SK_DES;
		skey.length = 8;
		skey.data = key_block->keyvalue.data;
		encrypt_session_key(&skey, 0);
	    }

	} else {
	    char *msg;

	    asprintf (&msg, "user `%s' is not authorized to "
		      "login as `%s'", 
		      name ? name : "<unknown>",
		      UserNameRequested ? UserNameRequested : "<nobody>");
	    if (msg == NULL)
		Data(ap, KRB_REJECT, NULL, 0);
	    else {
		Data(ap, KRB_REJECT, (void *)msg, -1);
		free(msg);
	    }
	    auth_finished (ap, AUTH_REJECT);
	    krb5_free_keyblock_contents(context, key_block);
	    break;
	}
	auth_finished(ap, AUTH_USER);
	krb5_free_keyblock_contents(context, key_block);
	
	break;
    case KRB_FORWARD: {
	struct passwd *pwd;
	char ccname[1024];	/* XXX */
	krb5_data inbuf;
	krb5_ccache ccache;
	inbuf.data = (char *)data;
	inbuf.length = cnt;

	pwd = getpwnam (UserNameRequested);
	if (pwd == NULL)
	    break;

	snprintf (ccname, sizeof(ccname),
		  "FILE:/tmp/krb5cc_%u", pwd->pw_uid);

	ret = krb5_cc_resolve (context, ccname, &ccache);
	if (ret) {
	    if (auth_debug_mode)
		printf ("Kerberos V5: could not get ccache: %s\r\n",
			krb5_get_err_text(context, ret));
	    break;
	}

	ret = krb5_cc_initialize (context,
				  ccache,
				  ticket->client);
	if (ret) {
	    if (auth_debug_mode)
		printf ("Kerberos V5: could not init ccache: %s\r\n",
			krb5_get_err_text(context, ret));
	    break;
	}

#if defined(DCE)
	esetenv("KRB5CCNAME", ccname, 1);
#endif
	ret = krb5_rd_cred2 (context,
			     auth_context,
			     ccache,
			     &inbuf);
	if(ret) {
	    char *errbuf;

	    asprintf (&errbuf,
		      "Read forwarded creds failed: %s",
		      krb5_get_err_text (context, ret));
	    if(errbuf == NULL)
		Data(ap, KRB_FORWARD_REJECT, NULL, 0);
	    else
		Data(ap, KRB_FORWARD_REJECT, errbuf, -1);
	    if (auth_debug_mode)
		printf("Could not read forwarded credentials: %s\r\n",
		       errbuf);
	    free (errbuf);
	} else {
	    Data(ap, KRB_FORWARD_ACCEPT, 0, 0);
#if defined(DCE)
	    dfsfwd = 1;
#endif
	}
	chown (ccname + 5, pwd->pw_uid, -1);
	if (auth_debug_mode)
	    printf("Forwarded credentials obtained\r\n");
	break;
    }
    default:
	if (auth_debug_mode)
	    printf("Unknown Kerberos option %d\r\n", data[-1]);
	Data(ap, KRB_REJECT, 0, 0);
	break;
    }
}

void
kerberos5_reply(Authenticator *ap, unsigned char *data, int cnt)
{
    static int mutual_complete = 0;

    if (cnt-- < 1)
	return;
    switch (*data++) {
    case KRB_REJECT:
	if (cnt > 0) {
	    printf("[ Kerberos V5 refuses authentication because %.*s ]\r\n",
		   cnt, data);
	} else
	    printf("[ Kerberos V5 refuses authentication ]\r\n");
	auth_send_retry();
	return;
    case KRB_ACCEPT: {
	krb5_error_code ret;
	Session_Key skey;
	krb5_keyblock *keyblock;
	
	if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL &&
	    !mutual_complete) {
	    printf("[ Kerberos V5 accepted you, but didn't provide mutual authentication! ]\r\n");
	    auth_send_retry();
	    return;
	}
	if (cnt)
	    printf("[ Kerberos V5 accepts you as ``%.*s'' ]\r\n", cnt, data);
	else
	    printf("[ Kerberos V5 accepts you ]\r\n");
	      
	ret = krb5_auth_con_getlocalsubkey (context,
					    auth_context,
					    &keyblock);
	if (ret)
	    ret = krb5_auth_con_getkey (context,
					auth_context,
					&keyblock);
	if(ret) {
	    printf("[ krb5_auth_con_getkey: %s ]\r\n",
		   krb5_get_err_text(context, ret));
	    auth_send_retry();
	    return;
	}
	      
	skey.type = SK_DES;
	skey.length = 8;
	skey.data = keyblock->keyvalue.data;
	encrypt_session_key(&skey, 0);
	krb5_free_keyblock_contents (context, keyblock);
	auth_finished(ap, AUTH_USER);
	if (forward_flags & OPTS_FORWARD_CREDS)
	    kerberos5_forward(ap);
	break;
    }
    case KRB_RESPONSE:
	if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
	    /* the rest of the reply should contain a krb_ap_rep */
	  krb5_ap_rep_enc_part *reply;
	  krb5_data inbuf;
	  krb5_error_code ret;
	    
	  inbuf.length = cnt;
	  inbuf.data = (char *)data;

	  ret = krb5_rd_rep(context, auth_context, &inbuf, &reply);
	  if (ret) {
	      printf("[ Mutual authentication failed: %s ]\r\n",
		     krb5_get_err_text (context, ret));
	      auth_send_retry();
	      return;
	  }
	  krb5_free_ap_rep_enc_part(context, reply);
	  mutual_complete = 1;
	}
	return;
    case KRB_FORWARD_ACCEPT:
	printf("[ Kerberos V5 accepted forwarded credentials ]\r\n");
	return;
    case KRB_FORWARD_REJECT:
	printf("[ Kerberos V5 refuses forwarded credentials because %.*s ]\r\n",
	       cnt, data);
	return;
    default:
	if (auth_debug_mode)
	    printf("Unknown Kerberos option %d\r\n", data[-1]);
	return;
    }
}

int
kerberos5_status(Authenticator *ap, char *name, size_t name_sz, int level)
{
    if (level < AUTH_USER)
	return(level);

    if (UserNameRequested &&
	krb5_kuserok(context,
		     ticket->client,
		     UserNameRequested))
	{
	    strlcpy(name, UserNameRequested, name_sz);
#if defined(DCE)
	    dfsk5ok = 1;
#endif
	    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
kerberos5_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
{
    int i;

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

    switch(data[3]) {
    case KRB_REJECT:		/* Rejected (reason might follow) */
	strlcpy((char *)buf, " REJECT ", buflen);
	goto common;

    case KRB_ACCEPT:		/* Accepted (name might follow) */
	strlcpy((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 KRB_AUTH:			/* Authentication data follows */
	strlcpy((char *)buf, " AUTH", buflen);
	goto common2;

    case KRB_RESPONSE:
	strlcpy((char *)buf, " RESPONSE", buflen);
	goto common2;

    case KRB_FORWARD:		/* Forwarded credentials follow */
	strlcpy((char *)buf, " FORWARD", buflen);
	goto common2;

    case KRB_FORWARD_ACCEPT:	/* Forwarded credentials accepted */
	strlcpy((char *)buf, " FORWARD_ACCEPT", buflen);
	goto common2;

    case KRB_FORWARD_REJECT:	/* Forwarded credentials rejected */
	/* (reason might follow) */
	strlcpy((char *)buf, " FORWARD_REJECT", buflen);
	goto common2;

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

void
kerberos5_forward(Authenticator *ap)
{
    krb5_error_code ret;
    krb5_ccache     ccache;
    krb5_creds      creds;
    krb5_kdc_flags  flags;
    krb5_data       out_data;
    krb5_principal  principal;

    ret = krb5_cc_default (context, &ccache);
    if (ret) {
	if (auth_debug_mode)
	    printf ("KerberosV5: could not get default ccache: %s\r\n",
		    krb5_get_err_text (context, ret));
	return;
    }

    ret = krb5_cc_get_principal (context, ccache, &principal);
    if (ret) {
	if (auth_debug_mode)
	    printf ("KerberosV5: could not get principal: %s\r\n",
		    krb5_get_err_text (context, ret));
	return;
    }

    memset (&creds, 0, sizeof(creds));

    creds.client = principal;
    
    ret = krb5_build_principal (context,
				&creds.server,
				strlen(principal->realm),
				principal->realm,
				"krbtgt",
				principal->realm,
				NULL);

    if (ret) {
	if (auth_debug_mode)
	    printf ("KerberosV5: could not get principal: %s\r\n",
		    krb5_get_err_text (context, ret));
	return;
    }

    creds.times.endtime = 0;

    flags.i = 0;
    flags.b.forwarded = 1;
    if (forward_flags & OPTS_FORWARDABLE_CREDS)
	flags.b.forwardable = 1;

    ret = krb5_get_forwarded_creds (context,
				    auth_context,
				    ccache,
				    flags.i,
				    RemoteHostName,
				    &creds,
				    &out_data);
    if (ret) {
	if (auth_debug_mode)
	    printf ("Kerberos V5: error getting forwarded creds: %s\r\n",
		    krb5_get_err_text (context, ret));
	return;
    }

    if(!Data(ap, KRB_FORWARD, out_data.data, out_data.length)) {
	if (auth_debug_mode)
	    printf("Not enough room for authentication data\r\n");
    } else {
	if (auth_debug_mode)
	    printf("Forwarded local Kerberos V5 credentials to server\r\n");
    }
}

#if defined(DCE)
/* if this was a K5 authentication try and join a PAG for the user. */
void
kerberos5_dfspag(void)
{
    if (dfsk5ok) {
	dfspag = krb5_dfs_pag(context, dfsfwd, ticket->client,
			      UserNameRequested);
    }
}
#endif

int
kerberos5_set_forward(int on)
{
    if(on == 0)
	forward_flags &= ~OPTS_FORWARD_CREDS;
    if(on == 1)
	forward_flags |= OPTS_FORWARD_CREDS;
    if(on == -1)
	forward_flags ^= OPTS_FORWARD_CREDS;
    return 0;
}

int
kerberos5_set_forwardable(int on)
{
    if(on == 0)
	forward_flags &= ~OPTS_FORWARDABLE_CREDS;
    if(on == 1)
	forward_flags |= OPTS_FORWARDABLE_CREDS;
    if(on == -1)
	forward_flags ^= OPTS_FORWARDABLE_CREDS;
    return 0;
}

#endif /* KRB5 */