446 lines
11 KiB
C
446 lines
11 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 1.47 2003/02/06 21:22:42 markus 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 "ssh1.h"
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#include "packet.h"
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#include "buffer.h"
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#include "mpaux.h"
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#include "log.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 "channels.h"
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#include "session.h"
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#include "uidswap.h"
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#include "monitor_wrap.h"
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/* import */
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extern ServerOptions options;
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/*
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* convert ssh auth msg type into description
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*/
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static 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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case SSH_CMSG_AUTH_TIS:
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case SSH_CMSG_AUTH_TIS_RESPONSE:
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return "challenge-response";
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#if defined(KRB4) || defined(KRB5)
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case SSH_CMSG_AUTH_KERBEROS:
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return "kerberos";
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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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* read packets, try to authenticate the user and
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* return only if authentication is successful
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*/
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static void
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do_authloop(Authctxt *authctxt)
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{
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int authenticated = 0;
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u_int bits;
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Key *client_host_key;
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BIGNUM *n;
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char *client_user, *password;
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char info[1024];
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u_int dlen;
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u_int ulen;
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int prev, type = 0;
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struct passwd *pw = authctxt->pw;
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debug("Attempting authentication for %s%.100s.",
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authctxt->valid ? "" : "illegal user ", authctxt->user);
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/* If the user has no password, accept authentication immediately. */
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if (options.password_authentication &&
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#if defined(KRB4) || defined(KRB5)
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(!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
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#endif
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PRIVSEP(auth_password(authctxt, ""))) {
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auth_log(authctxt, 1, "without authentication", "");
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return;
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}
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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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client_user = NULL;
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for (;;) {
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/* default to fail */
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authenticated = 0;
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info[0] = '\0';
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/* Get a packet from the client. */
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prev = type;
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type = packet_read();
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/*
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* If we started challenge-response authentication but the
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* next packet is not a response to our challenge, release
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* the resources allocated by get_challenge() (which would
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* normally have been released by verify_response() had we
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* received such a response)
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*/
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if (prev == SSH_CMSG_AUTH_TIS &&
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type != SSH_CMSG_AUTH_TIS_RESPONSE)
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abandon_challenge_response(authctxt);
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/* Process the packet. */
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switch (type) {
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#if defined(KRB4) || defined(KRB5)
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case SSH_CMSG_AUTH_KERBEROS:
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if (!options.kerberos_authentication) {
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verbose("Kerberos authentication disabled.");
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} else {
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char *kdata = packet_get_string(&dlen);
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packet_check_eom();
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if (kdata[0] == 4) { /* KRB_PROT_VERSION */
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#ifdef KRB4
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KTEXT_ST tkt, reply;
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tkt.length = dlen;
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if (tkt.length < MAX_KTXT_LEN)
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memcpy(tkt.dat, kdata, tkt.length);
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if (PRIVSEP(auth_krb4(authctxt, &tkt,
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&client_user, &reply))) {
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authenticated = 1;
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snprintf(info, sizeof(info),
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" tktuser %.100s",
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client_user);
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packet_start(
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SSH_SMSG_AUTH_KERBEROS_RESPONSE);
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packet_put_string((char *)
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reply.dat, reply.length);
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packet_send();
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packet_write_wait();
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}
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#endif /* KRB4 */
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} else {
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#ifdef KRB5
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krb5_data tkt, reply;
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tkt.length = dlen;
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tkt.data = kdata;
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if (PRIVSEP(auth_krb5(authctxt, &tkt,
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&client_user, &reply))) {
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authenticated = 1;
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snprintf(info, sizeof(info),
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" tktuser %.100s",
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client_user);
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/* Send response to client */
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packet_start(
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SSH_SMSG_AUTH_KERBEROS_RESPONSE);
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packet_put_string((char *)
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reply.data, reply.length);
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packet_send();
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packet_write_wait();
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if (reply.length)
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xfree(reply.data);
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}
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#endif /* KRB5 */
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}
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xfree(kdata);
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}
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break;
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#endif /* KRB4 || KRB5 */
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#if defined(AFS) || defined(KRB5)
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/* XXX - punt on backward compatibility here. */
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case SSH_CMSG_HAVE_KERBEROS_TGT:
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packet_send_debug("Kerberos TGT passing disabled before authentication.");
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break;
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#ifdef AFS
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case SSH_CMSG_HAVE_AFS_TOKEN:
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packet_send_debug("AFS token passing disabled before authentication.");
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break;
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#endif /* AFS */
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#endif /* AFS || 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_check_eom();
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/* Try to authenticate using /etc/hosts.equiv and .rhosts. */
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authenticated = auth_rhosts(pw, client_user);
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snprintf(info, sizeof info, " ruser %.100s", 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 = key_new(KEY_RSA1);
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bits = packet_get_int();
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packet_get_bignum(client_host_key->rsa->e);
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packet_get_bignum(client_host_key->rsa->n);
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if (bits != BN_num_bits(client_host_key->rsa->n))
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verbose("Warning: keysize mismatch for client_host_key: "
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"actual %d, announced %d",
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BN_num_bits(client_host_key->rsa->n), bits);
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packet_check_eom();
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authenticated = auth_rhosts_rsa(pw, client_user,
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client_host_key);
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key_free(client_host_key);
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snprintf(info, sizeof info, " ruser %.100s", 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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if ((n = BN_new()) == NULL)
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fatal("do_authloop: BN_new failed");
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packet_get_bignum(n);
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packet_check_eom();
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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_check_eom();
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/* Try authentication with the password. */
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authenticated = PRIVSEP(auth_password(authctxt, 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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case SSH_CMSG_AUTH_TIS:
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debug("rcvd SSH_CMSG_AUTH_TIS");
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if (options.challenge_response_authentication == 1) {
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char *challenge = get_challenge(authctxt);
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if (challenge != NULL) {
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debug("sending challenge '%s'", challenge);
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packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
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packet_put_cstring(challenge);
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xfree(challenge);
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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.challenge_response_authentication == 1) {
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char *response = packet_get_string(&dlen);
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packet_check_eom();
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authenticated = verify_response(authctxt, response);
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memset(response, 'r', dlen);
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xfree(response);
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}
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break;
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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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#ifdef BSD_AUTH
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if (authctxt->as) {
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auth_close(authctxt->as);
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authctxt->as = NULL;
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}
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#endif
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if (!authctxt->valid && authenticated)
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fatal("INTERNAL ERROR: authenticated invalid user %s",
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authctxt->user);
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#ifdef _UNICOS
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if (type == SSH_CMSG_AUTH_PASSWORD && !authenticated)
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cray_login_failure(authctxt->user, IA_UDBERR);
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if (authenticated && cray_access_denied(authctxt->user)) {
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authenticated = 0;
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fatal("Access denied for user %s.",authctxt->user);
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}
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#endif /* _UNICOS */
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#ifdef HAVE_CYGWIN
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if (authenticated &&
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!check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
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packet_disconnect("Authentication rejected for uid %d.",
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pw == NULL ? -1 : pw->pw_uid);
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authenticated = 0;
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}
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#else
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/* Special handling for root */
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if (authenticated && authctxt->pw->pw_uid == 0 &&
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!auth_root_allowed(get_authname(type)))
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authenticated = 0;
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#endif
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#ifdef USE_PAM
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if (!use_privsep && authenticated &&
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!do_pam_account(pw->pw_name, client_user))
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authenticated = 0;
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#endif
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/* Log before sending the reply */
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auth_log(authctxt, authenticated, get_authname(type), info);
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if (client_user != NULL) {
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xfree(client_user);
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client_user = NULL;
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}
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if (authenticated)
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return;
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if (authctxt->failures++ > AUTH_FAIL_MAX) {
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packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
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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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}
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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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Authctxt *
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do_authentication(void)
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{
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Authctxt *authctxt;
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u_int ulen;
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char *user, *style = NULL;
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/* Get the name of the user that we wish to log in as. */
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packet_read_expect(SSH_CMSG_USER);
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/* Get the user name. */
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user = packet_get_string(&ulen);
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packet_check_eom();
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if ((style = strchr(user, ':')) != NULL)
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*style++ = '\0';
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#ifdef KRB5
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/* XXX - SSH.com Kerberos v5 braindeath. */
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if ((datafellows & SSH_BUG_K5USER) &&
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options.kerberos_authentication) {
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char *p;
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if ((p = strchr(user, '@')) != NULL)
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*p = '\0';
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}
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#endif
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authctxt = authctxt_new();
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authctxt->user = user;
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authctxt->style = style;
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/* Verify that the user is a valid user. */
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if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
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authctxt->valid = 1;
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else
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debug("do_authentication: illegal user %s", user);
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setproctitle("%s%s", authctxt->pw ? user : "unknown",
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use_privsep ? " [net]" : "");
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#ifdef USE_PAM
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PRIVSEP(start_pam(authctxt->pw == NULL ? "NOUSER" : user));
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#endif
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/*
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* If we are not running as root, the user must have the same uid as
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* the server. (Unless you are running Windows)
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*/
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#ifndef HAVE_CYGWIN
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if (!use_privsep && getuid() != 0 && authctxt->pw &&
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authctxt->pw->pw_uid != getuid())
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packet_disconnect("Cannot change user when server not running as root.");
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#endif
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/*
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* Loop until the user has been authenticated or the connection is
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* closed, do_authloop() returns only if authentication is successful
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*/
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do_authloop(authctxt);
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/* The user has been authenticated and accepted. */
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packet_start(SSH_SMSG_SUCCESS);
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packet_send();
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packet_write_wait();
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return (authctxt);
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}
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