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/*
auth-passwd.c
Author: Tatu Ylonen <ylo@cs.hut.fi>
Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
All rights reserved
Created: Sat Mar 18 05:11:38 1995 ylo
Password authentication. This file contains the functions to check whether
the password is valid for the user.
*/
#include "includes.h"
RCSID("$Id: auth-passwd.c,v 1.8 1999/10/19 15:56:41 deraadt Exp $");
#include "packet.h"
#include "ssh.h"
#include "servconf.h"
#include "xmalloc.h"
#ifdef KRB4
extern char *ticket;
#endif /* KRB4 */
/* Tries to authenticate the user using password. Returns true if
authentication succeeds. */
int auth_password(struct passwd *pw, const char *password)
{
extern ServerOptions options;
char *encrypted_password;
if (pw->pw_uid == 0 && options.permit_root_login == 2)
{
/*packet_send_debug("Server does not permit root login with password.");*/
return 0;
}
if (*password == '\0' && options.permit_empty_passwd == 0)
{
/*packet_send_debug("Server does not permit empty password login.");*/
return 0;
}
/* deny if no user. */
if (pw == NULL)
return 0;
#ifdef SKEY
if (options.skey_authentication == 1) {
if (strncasecmp(password, "s/key", 5) == 0) {
char *skeyinfo = skey_keyinfo(pw->pw_name);
if(skeyinfo == NULL){
debug("generating fake skeyinfo for %.100s.", pw->pw_name);
skeyinfo = skey_fake_keyinfo(pw->pw_name);
}
if(skeyinfo != NULL)
packet_send_debug(skeyinfo);
/* Try again. */
return 0;
}
else if (skey_haskey(pw->pw_name) == 0 &&
skey_passcheck(pw->pw_name, (char *)password) != -1) {
/* Authentication succeeded. */
return 1;
}
/* Fall back to ordinary passwd authentication. */
}
#endif
#if defined(KRB4)
/* Support for Kerberos v4 authentication - Dug Song <dugsong@UMICH.EDU> */
if (options.kerberos_authentication)
{
AUTH_DAT adata;
KTEXT_ST tkt;
struct hostent *hp;
unsigned long faddr;
char localhost[MAXHOSTNAMELEN]; /* local host name */
char phost[INST_SZ]; /* host instance */
char realm[REALM_SZ]; /* local Kerberos realm */
int r;
/* Try Kerberos password authentication only for non-root
users and only if Kerberos is installed. */
if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
/* Set up our ticket file. */
if (!ssh_tf_init(pw->pw_uid)) {
log("Couldn't initialize Kerberos ticket file for %s!",
pw->pw_name);
goto kerberos_auth_failure;
}
/* Try to get TGT using our password. */
r = krb_get_pw_in_tkt((char *)pw->pw_name, "", realm, "krbtgt", realm,
DEFAULT_TKT_LIFE, (char *)password);
if (r != INTK_OK) {
packet_send_debug("Kerberos V4 password authentication for %s "
"failed: %s", pw->pw_name, krb_err_txt[r]);
goto kerberos_auth_failure;
}
/* Successful authentication. */
chown(ticket, pw->pw_uid, pw->pw_gid);
(void) gethostname(localhost, sizeof(localhost));
(void) strlcpy(phost, (char *)krb_get_phost(localhost), INST_SZ);
/* Now that we have a TGT, try to get a local "rcmd" ticket to
ensure that we are not talking to a bogus Kerberos server. */
r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
if (r == KSUCCESS) {
if (!(hp = gethostbyname(localhost))) {
log("Couldn't get local host address!");
goto kerberos_auth_failure;
}
memmove((void *)&faddr, (void *)hp->h_addr, sizeof(faddr));
/* Verify our "rcmd" ticket. */
r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost, faddr, &adata, "");
if (r == RD_AP_UNDEC) {
/* Probably didn't have a srvtab on localhost. Allow login. */
log("Kerberos V4 TGT for %s unverifiable, no srvtab installed? "
"krb_rd_req: %s", pw->pw_name, krb_err_txt[r]);
}
else if (r != KSUCCESS) {
log("Kerberos V4 %s ticket unverifiable: %s",
KRB4_SERVICE_NAME, krb_err_txt[r]);
goto kerberos_auth_failure;
}
}
else if (r == KDC_PR_UNKNOWN) {
/* Allow login if no rcmd service exists, but log the error. */
log("Kerberos V4 TGT for %s unverifiable: %s; %s.%s "
"not registered, or srvtab is wrong?", pw->pw_name,
krb_err_txt[r], KRB4_SERVICE_NAME, phost);
}
else {
/* TGT is bad, forget it. Possibly spoofed! */
packet_send_debug("WARNING: Kerberos V4 TGT possibly spoofed for"
"%s: %s", pw->pw_name, krb_err_txt[r]);
goto kerberos_auth_failure;
}
/* Authentication succeeded. */
return 1;
kerberos_auth_failure:
(void) dest_tkt();
xfree(ticket);
ticket = NULL;
if (!options.kerberos_or_local_passwd ) return 0;
}
else {
/* Logging in as root or no local Kerberos realm. */
packet_send_debug("Unable to authenticate to Kerberos.");
}
/* Fall back to ordinary passwd authentication. */
}
#endif /* KRB4 */
/* Check for users with no password. */
if (strcmp(password, "") == 0 && strcmp(pw->pw_passwd, "") == 0)
{
packet_send_debug("Login permitted without a password because the account has no password.");
return 1; /* The user has no password and an empty password was tried. */
}
/* Encrypt the candidate password using the proper salt. */
encrypted_password = crypt(password,
(pw->pw_passwd[0] && pw->pw_passwd[1]) ?
pw->pw_passwd : "xx");
/* Authentication is accepted if the encrypted passwords are identical. */
return (strcmp(encrypted_password, pw->pw_passwd) == 0);
}
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