600 lines
16 KiB
C
600 lines
16 KiB
C
/*
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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*
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* As far as I am concerned, the code I have written for this software
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* can be used freely for any purpose. Any derived versions of this
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* software must be clearly marked as such, and if the derived work is
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* incompatible with the protocol description in the RFC file, it must be
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* called by a name other than "ssh" or "Secure Shell".
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*/
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#include "includes.h"
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RCSID("$OpenBSD: auth1.c,v 1.4 2000/09/07 20:27:49 deraadt Exp $");
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RCSID("$FreeBSD$");
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#include "xmalloc.h"
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#include "rsa.h"
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#include "ssh.h"
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#include "packet.h"
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#include "buffer.h"
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#include "cipher.h"
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#include "mpaux.h"
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#include "servconf.h"
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#include "compat.h"
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#include "auth.h"
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#include "session.h"
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#include <login_cap.h>
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#ifdef KRB5
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extern krb5_context ssh_context;
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krb5_principal tkt_client = NULL; /* Principal from the received ticket.
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Also is used as an indication of succesful krb5 authentization. */
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#endif
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/* import */
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extern ServerOptions options;
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extern char *forced_command;
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/*
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* convert ssh auth msg type into description
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*/
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char *
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get_authname(int type)
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{
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static char buf[1024];
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switch (type) {
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case SSH_CMSG_AUTH_PASSWORD:
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return "password";
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case SSH_CMSG_AUTH_RSA:
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return "rsa";
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case SSH_CMSG_AUTH_RHOSTS_RSA:
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return "rhosts-rsa";
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case SSH_CMSG_AUTH_RHOSTS:
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return "rhosts";
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#ifdef KRB4
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case SSH_CMSG_AUTH_KRB4:
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return "kerberosV4";
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#endif
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#ifdef KRB5
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case SSH_CMSG_AUTH_KRB5:
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return "kerberosV5";
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#endif /* KRB5 */
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#ifdef SKEY
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case SSH_CMSG_AUTH_TIS_RESPONSE:
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return "s/key";
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#endif
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}
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snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
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return buf;
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}
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/*
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* The user does not exist or access is denied,
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* but fake indication that authentication is needed.
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*/
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void
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do_fake_authloop1(char *user)
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{
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int attempt = 0;
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log("Faking authloop for illegal user %.200s from %.200s port %d",
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user,
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get_remote_ipaddr(),
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get_remote_port());
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/* Indicate that authentication is needed. */
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packet_start(SSH_SMSG_FAILURE);
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packet_send();
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packet_write_wait();
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/*
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* Keep reading packets, and always respond with a failure. This is
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* to avoid disclosing whether such a user really exists.
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*/
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for (attempt = 1;; attempt++) {
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/* Read a packet. This will not return if the client disconnects. */
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int plen;
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int type = packet_read(&plen);
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#ifdef SKEY
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unsigned int dlen;
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char *password, *skeyinfo;
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password = NULL;
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/* Try to send a fake s/key challenge. */
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if (options.skey_authentication == 1 &&
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(skeyinfo = skey_fake_keyinfo(user)) != NULL) {
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if (type == SSH_CMSG_AUTH_TIS) {
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packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
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packet_put_string(skeyinfo, strlen(skeyinfo));
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packet_send();
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packet_write_wait();
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continue;
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} else if (type == SSH_CMSG_AUTH_PASSWORD &&
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options.password_authentication &&
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(password = packet_get_string(&dlen)) != NULL &&
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dlen == 5 &&
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strncasecmp(password, "s/key", 5) == 0 ) {
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packet_send_debug(skeyinfo);
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}
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}
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if (password != NULL)
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xfree(password);
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#endif
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if (attempt > AUTH_FAIL_MAX)
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packet_disconnect(AUTH_FAIL_MSG, user);
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/*
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* Send failure. This should be indistinguishable from a
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* failed authentication.
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*/
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packet_start(SSH_SMSG_FAILURE);
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packet_send();
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packet_write_wait();
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}
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/* NOTREACHED */
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abort();
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}
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/*
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* read packets and try to authenticate local user *pw.
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* return if authentication is successfull
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*/
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void
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do_authloop(struct passwd * pw)
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{
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int attempt = 0;
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unsigned int bits;
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RSA *client_host_key;
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BIGNUM *n;
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char *client_user, *password;
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char user[1024];
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unsigned int dlen;
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int plen, nlen, elen;
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unsigned int ulen;
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int type = 0;
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void (*authlog) (const char *fmt,...) = verbose;
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#ifdef HAVE_LOGIN_CAP
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login_cap_t *lc;
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#endif /* HAVE_LOGIN_CAP */
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#if defined(HAVE_LOGIN_CAP) || defined(LOGIN_ACCESS)
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const char *from_host, *from_ip;
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from_host = get_canonical_hostname();
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from_ip = get_remote_ipaddr();
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#endif /* HAVE_LOGIN_CAP || LOGIN_ACCESS */
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#ifdef HAVE_LIBPAM
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int pam_retval;
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#endif /* HAVE_LIBPAM */
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#if 0
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#ifdef KRB5
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{
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krb5_error_code ret;
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ret = krb5_init_context(&ssh_context);
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if (ret)
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verbose("Error while initializing Kerberos V5.");
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krb5_init_ets(ssh_context);
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}
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#endif /* KRB5 */
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#endif
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/* Indicate that authentication is needed. */
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packet_start(SSH_SMSG_FAILURE);
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packet_send();
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packet_write_wait();
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for (attempt = 1;; attempt++) {
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int authenticated = 0;
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strlcpy(user, "", sizeof user);
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/* Get a packet from the client. */
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type = packet_read(&plen);
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/* Process the packet. */
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switch (type) {
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#ifdef AFS
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case SSH_CMSG_HAVE_KRB4_TGT:
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if (!options.krb4_tgt_passing) {
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/* packet_get_all(); */
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verbose("Kerberos v4 tgt passing disabled.");
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break;
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} else {
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/* Accept Kerberos v4 tgt. */
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char *tgt = packet_get_string(&dlen);
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packet_integrity_check(plen, 4 + dlen, type);
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if (!auth_krb4_tgt(pw, tgt))
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verbose("Kerberos v4 tgt REFUSED for %s", pw->pw_name);
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xfree(tgt);
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}
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continue;
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case SSH_CMSG_HAVE_AFS_TOKEN:
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if (!options.afs_token_passing || !k_hasafs()) {
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/* packet_get_all(); */
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verbose("AFS token passing disabled.");
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break;
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} else {
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/* Accept AFS token. */
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char *token_string = packet_get_string(&dlen);
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packet_integrity_check(plen, 4 + dlen, type);
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if (!auth_afs_token(pw, token_string))
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verbose("AFS token REFUSED for %s", pw->pw_name);
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xfree(token_string);
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}
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continue;
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#endif /* AFS */
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#ifdef KRB4
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case SSH_CMSG_AUTH_KRB4:
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if (!options.krb4_authentication) {
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/* packet_get_all(); */
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verbose("Kerberos v4 authentication disabled.");
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break;
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} else {
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/* Try Kerberos v4 authentication. */
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KTEXT_ST auth;
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char *tkt_user = NULL;
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char *kdata = packet_get_string((unsigned int *) &auth.length);
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packet_integrity_check(plen, 4 + auth.length, type);
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if (auth.length < MAX_KTXT_LEN)
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memcpy(auth.dat, kdata, auth.length);
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xfree(kdata);
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authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user);
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if (authenticated) {
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snprintf(user, sizeof user, " tktuser %s", tkt_user);
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xfree(tkt_user);
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}
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}
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break;
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#endif /* KRB4 */
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#ifdef KRB5
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case SSH_CMSG_AUTH_KRB5:
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if (!options.krb5_authentication) {
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verbose("Kerberos v5 authentication disabled.");
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break;
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} else {
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krb5_data k5data;
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#if 0
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if (krb5_init_context(&ssh_context)) {
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verbose("Error while initializing Kerberos V5.");
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break;
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}
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krb5_init_ets(ssh_context);
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#endif
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k5data.data = packet_get_string(&k5data.length);
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packet_integrity_check(plen, 4 + k5data.length, type);
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if (auth_krb5(pw->pw_name, &k5data, &tkt_client)) {
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/* pw->name is passed just for logging purposes
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* */
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/* authorize client against .k5login */
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if (krb5_kuserok(ssh_context,
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tkt_client,
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pw->pw_name))
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authenticated = 1;
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}
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xfree(k5data.data);
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}
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break;
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#endif /* KRB5 */
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case SSH_CMSG_AUTH_RHOSTS:
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if (!options.rhosts_authentication) {
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verbose("Rhosts authentication disabled.");
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break;
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}
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/*
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* Get client user name. Note that we just have to
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* trust the client; this is one reason why rhosts
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* authentication is insecure. (Another is
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* IP-spoofing on a local network.)
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*/
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client_user = packet_get_string(&ulen);
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packet_integrity_check(plen, 4 + ulen, type);
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/* Try to authenticate using /etc/hosts.equiv and
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.rhosts. */
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authenticated = auth_rhosts(pw, client_user);
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snprintf(user, sizeof user, " ruser %s", client_user);
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xfree(client_user);
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break;
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case SSH_CMSG_AUTH_RHOSTS_RSA:
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if (!options.rhosts_rsa_authentication) {
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verbose("Rhosts with RSA authentication disabled.");
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break;
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}
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/*
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* Get client user name. Note that we just have to
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* trust the client; root on the client machine can
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* claim to be any user.
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*/
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client_user = packet_get_string(&ulen);
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/* Get the client host key. */
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client_host_key = RSA_new();
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if (client_host_key == NULL)
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fatal("RSA_new failed");
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client_host_key->e = BN_new();
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client_host_key->n = BN_new();
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if (client_host_key->e == NULL || client_host_key->n == NULL)
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fatal("BN_new failed");
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bits = packet_get_int();
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packet_get_bignum(client_host_key->e, &elen);
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packet_get_bignum(client_host_key->n, &nlen);
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if (bits != BN_num_bits(client_host_key->n))
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log("Warning: keysize mismatch for client_host_key: "
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"actual %d, announced %d", BN_num_bits(client_host_key->n), bits);
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packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
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authenticated = auth_rhosts_rsa(pw, client_user, client_host_key);
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RSA_free(client_host_key);
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snprintf(user, sizeof user, " ruser %s", client_user);
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xfree(client_user);
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break;
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case SSH_CMSG_AUTH_RSA:
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if (!options.rsa_authentication) {
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verbose("RSA authentication disabled.");
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break;
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}
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/* RSA authentication requested. */
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n = BN_new();
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packet_get_bignum(n, &nlen);
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packet_integrity_check(plen, nlen, type);
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authenticated = auth_rsa(pw, n);
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BN_clear_free(n);
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break;
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case SSH_CMSG_AUTH_PASSWORD:
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if (!options.password_authentication) {
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verbose("Password authentication disabled.");
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break;
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}
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/*
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* Read user password. It is in plain text, but was
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* transmitted over the encrypted channel so it is
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* not visible to an outside observer.
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*/
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password = packet_get_string(&dlen);
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packet_integrity_check(plen, 4 + dlen, type);
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/* Try authentication with the password. */
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authenticated = auth_password(pw, password);
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memset(password, 0, strlen(password));
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xfree(password);
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break;
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#ifdef SKEY
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case SSH_CMSG_AUTH_TIS:
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debug("rcvd SSH_CMSG_AUTH_TIS");
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if (options.skey_authentication == 1) {
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char *skeyinfo = opie_keyinfo(pw->pw_name);
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if (skeyinfo == NULL) {
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debug("generating fake skeyinfo for %.100s.", pw->pw_name);
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skeyinfo = skey_fake_keyinfo(pw->pw_name);
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}
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if (skeyinfo != NULL) {
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/* we send our s/key- in tis-challenge messages */
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debug("sending challenge '%s'", skeyinfo);
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packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
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packet_put_string(skeyinfo, strlen(skeyinfo));
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packet_send();
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packet_write_wait();
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continue;
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}
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}
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break;
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case SSH_CMSG_AUTH_TIS_RESPONSE:
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debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
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if (options.skey_authentication == 1) {
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char *response = packet_get_string(&dlen);
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debug("skey response == '%s'", response);
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packet_integrity_check(plen, 4 + dlen, type);
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authenticated = (opie_haskey(pw->pw_name) == 0 &&
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opie_passverify(pw->pw_name, response) != -1);
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xfree(response);
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}
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break;
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#else
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case SSH_CMSG_AUTH_TIS:
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/* TIS Authentication is unsupported */
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log("TIS authentication unsupported.");
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break;
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#endif
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#ifdef KRB5
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case SSH_CMSG_HAVE_KRB5_TGT:
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/* Passing krb5 ticket */
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if (!options.krb5_tgt_passing
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/*|| !options.krb5_authentication */) {
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}
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if (tkt_client == NULL) {
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/* passing tgt without krb5 authentication */
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}
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{
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krb5_data tgt;
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tgt.data = packet_get_string(&tgt.length);
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if (!auth_krb5_tgt(pw->pw_name, &tgt, tkt_client))
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verbose ("Kerberos V5 TGT refused for %.100s", pw->pw_name);
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xfree(tgt.data);
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break;
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}
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#endif /* KRB5 */
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default:
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/*
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* Any unknown messages will be ignored (and failure
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* returned) during authentication.
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*/
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log("Unknown message during authentication: type %d", type);
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break;
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}
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/*
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* Check if the user is logging in as root and root logins
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* are disallowed.
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* Note that root login is allowed for forced commands.
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*/
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if (authenticated && pw->pw_uid == 0 && !options.permit_root_login) {
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if (forced_command) {
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log("Root login accepted for forced command.");
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} else {
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authenticated = 0;
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log("ROOT LOGIN REFUSED FROM %.200s",
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get_canonical_hostname());
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}
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}
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#ifdef HAVE_LOGIN_CAP
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lc = login_getpwclass(pw);
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if (lc == NULL)
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lc = login_getclassbyname(NULL, pw);
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if (!auth_hostok(lc, from_host, from_ip)) {
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log("Denied connection for %.200s from %.200s [%.200s].",
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pw->pw_name, from_host, from_ip);
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packet_disconnect("Sorry, you are not allowed to connect.");
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}
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if (!auth_timeok(lc, time(NULL))) {
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log("LOGIN %.200s REFUSED (TIME) FROM %.200s",
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pw->pw_name, from_host);
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packet_disconnect("Logins not available right now.");
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}
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login_close(lc);
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#endif /* HAVE_LOGIN_CAP */
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#ifdef LOGIN_ACCESS
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if (!login_access(pw->pw_name, from_host)) {
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log("Denied connection for %.200s from %.200s [%.200s].",
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pw->pw_name, from_host, from_ip);
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packet_disconnect("Sorry, you are not allowed to connect.");
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}
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#endif /* LOGIN_ACCESS */
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if (pw->pw_uid == 0)
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log("ROOT LOGIN as '%.100s' from %.100s",
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pw->pw_name, get_canonical_hostname());
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/* Raise logging level */
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if (authenticated ||
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attempt == AUTH_FAIL_LOG ||
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type == SSH_CMSG_AUTH_PASSWORD)
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authlog = log;
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authlog("%s %s for %.200s from %.200s port %d%s",
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authenticated ? "Accepted" : "Failed",
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get_authname(type),
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pw->pw_uid == 0 ? "ROOT" : pw->pw_name,
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get_remote_ipaddr(),
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get_remote_port(),
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user);
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if (authenticated)
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return;
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if (attempt > AUTH_FAIL_MAX)
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packet_disconnect(AUTH_FAIL_MSG, pw->pw_name);
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/* Send a message indicating that the authentication attempt failed. */
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packet_start(SSH_SMSG_FAILURE);
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packet_send();
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packet_write_wait();
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}
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}
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/*
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* Performs authentication of an incoming connection. Session key has already
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* been exchanged and encryption is enabled.
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*/
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void
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do_authentication()
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{
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struct passwd *pw, pwcopy;
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int plen;
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unsigned int ulen;
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char *user;
|
|
|
|
/* Get the name of the user that we wish to log in as. */
|
|
packet_read_expect(&plen, SSH_CMSG_USER);
|
|
|
|
/* Get the user name. */
|
|
user = packet_get_string(&ulen);
|
|
packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
|
|
|
|
setproctitle("%s", user);
|
|
|
|
#ifdef AFS
|
|
/* If machine has AFS, set process authentication group. */
|
|
if (k_hasafs()) {
|
|
k_setpag();
|
|
k_unlog();
|
|
}
|
|
#endif /* AFS */
|
|
|
|
/* Verify that the user is a valid user. */
|
|
pw = getpwnam(user);
|
|
if (!pw || !allowed_user(pw))
|
|
do_fake_authloop1(user);
|
|
xfree(user);
|
|
|
|
/* Take a copy of the returned structure. */
|
|
memset(&pwcopy, 0, sizeof(pwcopy));
|
|
pwcopy.pw_name = xstrdup(pw->pw_name);
|
|
pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
|
|
pwcopy.pw_uid = pw->pw_uid;
|
|
pwcopy.pw_gid = pw->pw_gid;
|
|
pwcopy.pw_class = xstrdup(pw->pw_class);
|
|
pwcopy.pw_dir = xstrdup(pw->pw_dir);
|
|
pwcopy.pw_shell = xstrdup(pw->pw_shell);
|
|
pwcopy.pw_class = xstrdup(pw->pw_class);
|
|
pwcopy.pw_expire = pw->pw_expire;
|
|
pwcopy.pw_change = pw->pw_change;
|
|
pw = &pwcopy;
|
|
|
|
/*
|
|
* If we are not running as root, the user must have the same uid as
|
|
* the server.
|
|
*/
|
|
if (getuid() != 0 && pw->pw_uid != getuid())
|
|
packet_disconnect("Cannot change user when server not running as root.");
|
|
|
|
debug("Attempting authentication for %.100s.", pw->pw_name);
|
|
|
|
/* If the user has no password, accept authentication immediately. */
|
|
if (options.password_authentication &&
|
|
#ifdef KRB5
|
|
!options.krb5_authentication &&
|
|
#endif /* KRB5 */
|
|
#ifdef KRB4
|
|
(!options.krb4_authentication || options.krb4_or_local_passwd) &&
|
|
#endif /* KRB4 */
|
|
auth_password(pw, "")) {
|
|
/* Authentication with empty password succeeded. */
|
|
log("Login for user %s from %.100s, accepted without authentication.",
|
|
pw->pw_name, get_remote_ipaddr());
|
|
} else {
|
|
/* Loop until the user has been authenticated or the
|
|
connection is closed, do_authloop() returns only if
|
|
authentication is successfull */
|
|
do_authloop(pw);
|
|
}
|
|
|
|
/* The user has been authenticated and accepted. */
|
|
packet_start(SSH_SMSG_SUCCESS);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
/* Perform session preparation. */
|
|
do_authenticated(pw);
|
|
}
|