crypto/openssh/auth-rh-rsa.c

   1 /* $OpenBSD: auth-rh-rsa.c,v 1.42 2006/08/03 03:34:41 deraadt 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 "xmalloc.h"
  24 #include "packet.h"
  25 #include "uidswap.h"
  26 #include "log.h"
  27 #include "buffer.h"
  28 #include "servconf.h"
  29 #include "key.h"
  30 #include "hostfile.h"
  31 #include "authfile.h"
  32 #include "pathnames.h"
  33 #include "auth.h"
  34 #include "canohost.h"
  35 #ifdef GSSAPI
  36 #include "ssh-gss.h"
  37 #endif
  38 #include "monitor_wrap.h"
  39
  40 /* import */
  41 extern ServerOptions options;
  42
  43 int
  44 auth_rhosts_rsa_key_allowed(struct passwd *pw, char *cuser, char *chost,
  45     Key *client_host_key)
  46 {
  47         char *fp;
  48         HostStatus host_status;
  49
  50         if (blacklisted_key(client_host_key)) {
  51                 fp = key_fingerprint(client_host_key, SSH_FP_MD5, SSH_FP_HEX);
  52                 if (options.permit_blacklisted_keys)
  53                         logit("Public key %s blacklisted (see "
  54                             "ssh-vulnkey(1)); continuing anyway", fp);
  55                 else
  56                         logit("Public key %s blacklisted (see "
  57                             "ssh-vulnkey(1))", fp);
  58                 xfree(fp);
  59                 if (!options.permit_blacklisted_keys)
  60                         return 0;
  61         }
  62
  63         /* Check if we would accept it using rhosts authentication. */
  64         if (!auth_rhosts(pw, cuser))
  65                 return 0;
  66
  67         host_status = check_key_in_hostfiles(pw, client_host_key,
  68             chost, _PATH_SSH_SYSTEM_HOSTFILE,
  69             options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
  70
  71         return (host_status == HOST_OK);
  72 }
  73
  74 /*
  75  * Tries to authenticate the user using the .rhosts file and the host using
  76  * its host key.  Returns true if authentication succeeds.
  77  */
  78 int
  79 auth_rhosts_rsa(Authctxt *authctxt, char *cuser, Key *client_host_key)
  80 {
  81         char *chost;
  82         struct passwd *pw = authctxt->pw;
  83
  84         debug("Trying rhosts with RSA host authentication for client user %.100s",
  85             cuser);
  86
  87         if (!authctxt->valid || client_host_key == NULL ||
  88             client_host_key->rsa == NULL)
  89                 return 0;
  90
  91         chost = (char *)get_canonical_hostname(options.use_dns);
  92         debug("Rhosts RSA authentication: canonical host %.900s", chost);
  93
  94         if (!PRIVSEP(auth_rhosts_rsa_key_allowed(pw, cuser, chost, client_host_key))) {
  95                 debug("Rhosts with RSA host authentication denied: unknown or invalid host key");
  96                 packet_send_debug("Your host key cannot be verified: unknown or invalid host key.");
  97                 return 0;
  98         }
  99         /* A matching host key was found and is known. */
 100
 101         /* Perform the challenge-response dialog with the client for the host key. */
 102         if (!auth_rsa_challenge_dialog(client_host_key)) {
 103                 logit("Client on %.800s failed to respond correctly to host authentication.",
 104                     chost);
 105                 return 0;
 106         }
 107         /*
 108          * We have authenticated the user using .rhosts or /etc/hosts.equiv,
 109          * and the host using RSA. We accept the authentication.
 110          */
 111
 112         verbose("Rhosts with RSA host authentication accepted for %.100s, %.100s on %.700s.",
 113             pw->pw_name, cuser, chost);
 114         packet_send_debug("Rhosts with RSA host authentication accepted.");
 115         return 1;
 116 }