fc0824d97d
not respond to challenge, and later successfully authenticated itself using another method, the kbdint context would never be released, leaving the PAM child process behind even after the connection ended. Fix this by automatically releasing the kbdint context if a packet of type SSH_CMSG_AUTH_TIS is follwed by anything but a packet of type SSH_CMSG_AUTH_TIS_RESPONSE. MFC after: 1 week
448 lines
11 KiB
C
448 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 1.44 2002/09/26 11:38:43 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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debug("got response '%s'", response);
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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 (!use_privsep &&
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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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