auth-passwd.c

   1 /* $OpenBSD: auth-passwd.c,v 1.48 2020/10/18 11:32:01 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Password authentication.  This file contains the functions to check whether
   7  * the password is valid for the user.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  *
  15  * Copyright (c) 1999 Dug Song.  All rights reserved.
  16  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions
  20  * are met:
  21  * 1. Redistributions of source code must retain the above copyright
  22  *    notice, this list of conditions and the following disclaimer.
  23  * 2. Redistributions in binary form must reproduce the above copyright
  24  *    notice, this list of conditions and the following disclaimer in the
  25  *    documentation and/or other materials provided with the distribution.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  28  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  29  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  30  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  31  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  32  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  33  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  34  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  35  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  36  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37  */
  38
  39 #include "includes.h"
  40
  41 #include <sys/types.h>
  42
  43 #include <pwd.h>
  44 #include <stdio.h>
  45 #include <string.h>
  46 #include <stdarg.h>
  47
  48 #include "packet.h"
  49 #include "sshbuf.h"
  50 #include "ssherr.h"
  51 #include "log.h"
  52 #include "misc.h"
  53 #include "servconf.h"
  54 #include "sshkey.h"
  55 #include "hostfile.h"
  56 #include "auth.h"
  57 #include "auth-options.h"
  58
  59 extern struct sshbuf *loginmsg;
  60 extern ServerOptions options;
  61
  62 #ifdef HAVE_LOGIN_CAP
  63 extern login_cap_t *lc;
  64 #endif
  65
  66
  67 #define DAY             (24L * 60 * 60) /* 1 day in seconds */
  68 #define TWO_WEEKS       (2L * 7 * DAY)  /* 2 weeks in seconds */
  69
  70 #define MAX_PASSWORD_LEN        1024
  71
  72 /*
  73  * Tries to authenticate the user using password.  Returns true if
  74  * authentication succeeds.
  75  */
  76 int
  77 auth_password(struct ssh *ssh, const char *password)
  78 {
  79         Authctxt *authctxt = ssh->authctxt;
  80         struct passwd *pw = authctxt->pw;
  81         int result, ok = authctxt->valid;
  82 #if defined(USE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
  83         static int expire_checked = 0;
  84 #endif
  85
  86         if (strlen(password) > MAX_PASSWORD_LEN)
  87                 return 0;
  88
  89 #ifndef HAVE_CYGWIN
  90         if (pw->pw_uid == 0 && options.permit_root_login != PERMIT_YES)
  91                 ok = 0;
  92 #endif
  93         if (*password == '\0' && options.permit_empty_passwd == 0)
  94                 return 0;
  95
  96 #ifdef KRB5
  97         if (options.kerberos_authentication == 1) {
  98                 int ret = auth_krb5_password(authctxt, password);
  99                 if (ret == 1 || ret == 0)
 100                         return ret && ok;
 101                 /* Fall back to ordinary passwd authentication. */
 102         }
 103 #endif
 104 #ifdef HAVE_CYGWIN
 105         {
 106                 HANDLE hToken = cygwin_logon_user(pw, password);
 107
 108                 if (hToken == INVALID_HANDLE_VALUE)
 109                         return 0;
 110                 cygwin_set_impersonation_token(hToken);
 111                 return ok;
 112         }
 113 #endif
 114 #ifdef USE_PAM
 115         if (options.use_pam)
 116                 return (sshpam_auth_passwd(authctxt, password) && ok);
 117 #endif
 118 #if defined(USE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
 119         if (!expire_checked) {
 120                 expire_checked = 1;
 121                 if (auth_shadow_pwexpired(authctxt))
 122                         authctxt->force_pwchange = 1;
 123         }
 124 #endif
 125         result = sys_auth_passwd(ssh, password);
 126         if (authctxt->force_pwchange)
 127                 auth_restrict_session(ssh);
 128         return (result && ok);
 129 }
 130
 131 #ifdef BSD_AUTH
 132 static void
 133 warn_expiry(Authctxt *authctxt, auth_session_t *as)
 134 {
 135         int r;
 136         quad_t pwtimeleft, actimeleft, daysleft, pwwarntime, acwarntime;
 137
 138         pwwarntime = acwarntime = TWO_WEEKS;
 139
 140         pwtimeleft = auth_check_change(as);
 141         actimeleft = auth_check_expire(as);
 142 #ifdef HAVE_LOGIN_CAP
 143         if (authctxt->valid) {
 144                 pwwarntime = login_getcaptime(lc, "password-warn", TWO_WEEKS,
 145                     TWO_WEEKS);
 146                 acwarntime = login_getcaptime(lc, "expire-warn", TWO_WEEKS,
 147                     TWO_WEEKS);
 148         }
 149 #endif
 150         if (pwtimeleft != 0 && pwtimeleft < pwwarntime) {
 151                 daysleft = pwtimeleft / DAY + 1;
 152                 if ((r = sshbuf_putf(loginmsg,
 153                     "Your password will expire in %lld day%s.\n",
 154                     daysleft, daysleft == 1 ? "" : "s")) != 0)
 155                         fatal_fr(r, "buffer error");
 156         }
 157         if (actimeleft != 0 && actimeleft < acwarntime) {
 158                 daysleft = actimeleft / DAY + 1;
 159                 if ((r = sshbuf_putf(loginmsg,
 160                     "Your account will expire in %lld day%s.\n",
 161                     daysleft, daysleft == 1 ? "" : "s")) != 0)
 162                         fatal_fr(r, "buffer error");
 163         }
 164 }
 165
 166 int
 167 sys_auth_passwd(struct ssh *ssh, const char *password)
 168 {
 169         Authctxt *authctxt = ssh->authctxt;
 170         auth_session_t *as;
 171         static int expire_checked = 0;
 172
 173         as = auth_usercheck(authctxt->pw->pw_name, authctxt->style, "auth-ssh",
 174             (char *)password);
 175         if (as == NULL)
 176                 return (0);
 177         if (auth_getstate(as) & AUTH_PWEXPIRED) {
 178                 auth_close(as);
 179                 auth_restrict_session(ssh);
 180                 authctxt->force_pwchange = 1;
 181                 return (1);
 182         } else {
 183                 if (!expire_checked) {
 184                         expire_checked = 1;
 185                         warn_expiry(authctxt, as);
 186                 }
 187                 return (auth_close(as));
 188         }
 189 }
 190 #elif !defined(CUSTOM_SYS_AUTH_PASSWD)
 191 int
 192 sys_auth_passwd(struct ssh *ssh, const char *password)
 193 {
 194         Authctxt *authctxt = ssh->authctxt;
 195         struct passwd *pw = authctxt->pw;
 196         char *encrypted_password, *salt = NULL;
 197
 198         /* Just use the supplied fake password if authctxt is invalid */
 199         char *pw_password = authctxt->valid ? shadow_pw(pw) : pw->pw_passwd;
 200
 201         if (pw_password == NULL)
 202                 return 0;
 203
 204         /* Check for users with no password. */
 205         if (strcmp(pw_password, "") == 0 && strcmp(password, "") == 0)
 206                 return (1);
 207
 208         /*
 209          * Encrypt the candidate password using the proper salt, or pass a
 210          * NULL and let xcrypt pick one.
 211          */
 212         if (authctxt->valid && pw_password[0] && pw_password[1])
 213                 salt = pw_password;
 214         encrypted_password = xcrypt(password, salt);
 215
 216         /*
 217          * Authentication is accepted if the encrypted passwords
 218          * are identical.
 219          */
 220         return encrypted_password != NULL &&
 221             strcmp(encrypted_password, pw_password) == 0;
 222 }
 223 #endif