auth-rh-rsa.c

   1 /* $OpenBSD: auth-rh-rsa.c,v 1.43 2010/03/04 10:36:03 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  * Rhosts or /etc/hosts.equiv authentication combined with RSA host
   7  * authentication.
   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
  16 #include "includes.h"
  17
  18 #include <sys/types.h>
  19
  20 #include <pwd.h>
  21 #include <stdarg.h>
  22
  23 #include "packet.h"
  24 #include "uidswap.h"
  25 #include "log.h"
  26 #include "buffer.h"
  27 #include "servconf.h"
  28 #include "key.h"
  29 #include "hostfile.h"
  30 #include "pathnames.h"
  31 #include "auth.h"
  32 #include "canohost.h"
  33 #ifdef GSSAPI
  34 #include "ssh-gss.h"
  35 #endif
  36 #include "monitor_wrap.h"
  37
  38 /* import */
  39 extern ServerOptions options;
  40
  41 int
  42 auth_rhosts_rsa_key_allowed(struct passwd *pw, char *cuser, char *chost,
  43     Key *client_host_key)
  44 {
  45         HostStatus host_status;
  46
  47         if (auth_key_is_revoked(client_host_key))
  48                 return 0;
  49
  50         /* Check if we would accept it using rhosts authentication. */
  51         if (!auth_rhosts(pw, cuser))
  52                 return 0;
  53
  54         host_status = check_key_in_hostfiles(pw, client_host_key,
  55             chost, _PATH_SSH_SYSTEM_HOSTFILE,
  56             options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
  57
  58         return (host_status == HOST_OK);
  59 }
  60
  61 /*
  62  * Tries to authenticate the user using the .rhosts file and the host using
  63  * its host key.  Returns true if authentication succeeds.
  64  */
  65 int
  66 auth_rhosts_rsa(Authctxt *authctxt, char *cuser, Key *client_host_key)
  67 {
  68         char *chost;
  69         struct passwd *pw = authctxt->pw;
  70
  71         debug("Trying rhosts with RSA host authentication for client user %.100s",
  72             cuser);
  73
  74         if (!authctxt->valid || client_host_key == NULL ||
  75             client_host_key->rsa == NULL)
  76                 return 0;
  77
  78         chost = (char *)get_canonical_hostname(options.use_dns);
  79         debug("Rhosts RSA authentication: canonical host %.900s", chost);
  80
  81         if (!PRIVSEP(auth_rhosts_rsa_key_allowed(pw, cuser, chost, client_host_key))) {
  82                 debug("Rhosts with RSA host authentication denied: unknown or invalid host key");
  83                 packet_send_debug("Your host key cannot be verified: unknown or invalid host key.");
  84                 return 0;
  85         }
  86         /* A matching host key was found and is known. */
  87
  88         /* Perform the challenge-response dialog with the client for the host key. */
  89         if (!auth_rsa_challenge_dialog(client_host_key)) {
  90                 logit("Client on %.800s failed to respond correctly to host authentication.",
  91                     chost);
  92                 return 0;
  93         }
  94         /*
  95          * We have authenticated the user using .rhosts or /etc/hosts.equiv,
  96          * and the host using RSA. We accept the authentication.
  97          */
  98
  99         verbose("Rhosts with RSA host authentication accepted for %.100s, %.100s on %.700s.",
 100             pw->pw_name, cuser, chost);
 101         packet_send_debug("Rhosts with RSA host authentication accepted.");
 102         return 1;
 103 }