/* * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this * software must be clearly marked as such, and if the derived work is * incompatible with the protocol description in the RFC file, it must be * called by a name other than "ssh" or "Secure Shell". */ #include "includes.h" RCSID("$OpenBSD: auth1.c,v 1.22 2001/03/23 12:02:49 markus Exp $"); RCSID("$FreeBSD: src/crypto/openssh/auth1.c,v 1.17 2001/09/04 13:27:04 assar Exp $"); #include "xmalloc.h" #include "rsa.h" #include "ssh1.h" #include "packet.h" #include "buffer.h" #include "mpaux.h" #include "log.h" #include "servconf.h" #include "compat.h" #include "auth.h" #include "auth-pam.h" #include "session.h" #include "canohost.h" #include "misc.h" #include #include #ifdef KRB5 extern krb5_context ssh_context; krb5_principal tkt_client = NULL; /* Principal from the received ticket. Also is used as an indication of succesful krb5 authentization. */ #endif /* import */ extern ServerOptions options; /* * convert ssh auth msg type into description */ char * get_authname(int type) { static char buf[1024]; switch (type) { case SSH_CMSG_AUTH_PASSWORD: return "password"; case SSH_CMSG_AUTH_RSA: return "rsa"; case SSH_CMSG_AUTH_RHOSTS_RSA: return "rhosts-rsa"; case SSH_CMSG_AUTH_RHOSTS: return "rhosts"; case SSH_CMSG_AUTH_TIS: case SSH_CMSG_AUTH_TIS_RESPONSE: return "challenge-response"; #if defined(KRB4) || defined(KRB5) case SSH_CMSG_AUTH_KERBEROS: return "kerberos"; #endif } snprintf(buf, sizeof buf, "bad-auth-msg-%d", type); return buf; } /* * read packets, try to authenticate the user and * return only if authentication is successful */ void do_authloop(Authctxt *authctxt) { int authenticated = 0; u_int bits; RSA *client_host_key; BIGNUM *n; char *client_user, *password; char info[1024]; u_int dlen; int plen, nlen, elen; u_int ulen; int type = 0; struct passwd *pw = authctxt->pw; void (*authlog) (const char *fmt,...) = verbose; #ifdef HAVE_LOGIN_CAP login_cap_t *lc; #endif /* HAVE_LOGIN_CAP */ #ifdef USE_PAM struct inverted_pam_cookie *pam_cookie; #endif /* USE_PAM */ #if defined(HAVE_LOGIN_CAP) || defined(LOGIN_ACCESS) const char *from_host, *from_ip; from_host = get_canonical_hostname(options.reverse_mapping_check); from_ip = get_remote_ipaddr(); #endif /* HAVE_LOGIN_CAP || LOGIN_ACCESS */ #if 0 #ifdef KRB5 { krb5_error_code ret; ret = krb5_init_context(&ssh_context); if (ret) verbose("Error while initializing Kerberos V5."); krb5_init_ets(ssh_context); } #endif /* KRB5 */ #endif debug("Attempting authentication for %s%.100s.", authctxt->valid ? "" : "illegal user ", authctxt->user); /* If the user has no password, accept authentication immediately. */ if (options.password_authentication && #if defined(KRB4) || defined(KRB5) (!options.kerberos_authentication #if defined(KRB4) || options.krb4_or_local_passwd #endif ) && #endif #ifdef USE_PAM auth_pam_password(authctxt, "") #else auth_password(authctxt, "") #endif ) { auth_log(authctxt, 1, "without authentication", ""); return; } /* Indicate that authentication is needed. */ packet_start(SSH_SMSG_FAILURE); packet_send(); packet_write_wait(); client_user = NULL; for (;;) { /* default to fail */ authenticated = 0; info[0] = '\0'; /* Get a packet from the client. */ type = packet_read(&plen); /* Process the packet. */ switch (type) { #ifdef AFS #ifndef KRB5 case SSH_CMSG_HAVE_KERBEROS_TGT: if (!options.krb4_tgt_passing) { /* packet_get_all(); */ verbose("Kerberos v4 tgt passing disabled."); break; } else { /* Accept Kerberos v4 tgt. */ char *tgt = packet_get_string(&dlen); packet_integrity_check(plen, 4 + dlen, type); if (!auth_krb4_tgt(pw, tgt)) verbose("Kerberos v4 tgt REFUSED for %.100ss", authctxt->user); xfree(tgt); } continue; #endif /* !KRB5 */ case SSH_CMSG_HAVE_AFS_TOKEN: if (!options.afs_token_passing || !k_hasafs()) { verbose("AFS token passing disabled."); break; } else { /* Accept AFS token. */ char *token_string = packet_get_string(&dlen); packet_integrity_check(plen, 4 + dlen, type); if (!auth_afs_token(pw, token_string)) verbose("AFS token REFUSED for %.100s", authctxt->user); xfree(token_string); } continue; #endif /* AFS */ #if defined(KRB4) || defined(KRB5) case SSH_CMSG_AUTH_KERBEROS: if (!options.kerberos_authentication) { verbose("Kerberos authentication disabled."); break; } else { /* Try Kerberos authentication. */ u_int len; char *tkt_user = NULL; char *kdata = packet_get_string(&len); packet_integrity_check(plen, 4 + len, type); if (!authctxt->valid) { /* Do nothing. */ } else if (kdata[0] == 4) { /* 4 == KRB_PROT_VERSION */ #ifdef KRB4 KTEXT_ST auth; auth.length = len; if (auth.length < MAX_KTXT_LEN) memcpy(auth.dat, kdata, auth.length); authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user); if (authenticated) { snprintf(info, sizeof info, " tktuser %.100s", tkt_user); xfree(tkt_user); } #else verbose("Kerberos v4 authentication disabled."); #endif /* KRB4 */ } else { #ifndef KRB5 verbose("Kerberos v5 authentication disabled."); #else krb5_data k5data; k5data.length = len; k5data.data = kdata; #if 0 if (krb5_init_context(&ssh_context)) { verbose("Error while initializing Kerberos V5."); break; } krb5_init_ets(ssh_context); #endif /* pw->name is passed just for logging purposes */ if (auth_krb5(pw->pw_name, &k5data, &tkt_client)) { /* authorize client against .k5login */ if (krb5_kuserok(ssh_context, tkt_client, pw->pw_name)) authenticated = 1; } #endif /* KRB5 */ } xfree(kdata); } break; #endif /* KRB4 || KRB5 */ case SSH_CMSG_AUTH_RHOSTS: if (!options.rhosts_authentication) { verbose("Rhosts authentication disabled."); break; } /* * Get client user name. Note that we just have to * trust the client; this is one reason why rhosts * authentication is insecure. (Another is * IP-spoofing on a local network.) */ client_user = packet_get_string(&ulen); packet_integrity_check(plen, 4 + ulen, type); /* Try to authenticate using /etc/hosts.equiv and .rhosts. */ authenticated = auth_rhosts(pw, client_user); snprintf(info, sizeof info, " ruser %.100s", client_user); break; case SSH_CMSG_AUTH_RHOSTS_RSA: if (!options.rhosts_rsa_authentication) { verbose("Rhosts with RSA authentication disabled."); break; } /* * Get client user name. Note that we just have to * trust the client; root on the client machine can * claim to be any user. */ client_user = packet_get_string(&ulen); /* Get the client host key. */ client_host_key = RSA_new(); if (client_host_key == NULL) fatal("RSA_new failed"); client_host_key->e = BN_new(); client_host_key->n = BN_new(); if (client_host_key->e == NULL || client_host_key->n == NULL) fatal("BN_new failed"); bits = packet_get_int(); packet_get_bignum(client_host_key->e, &elen); packet_get_bignum(client_host_key->n, &nlen); if (bits != BN_num_bits(client_host_key->n)) verbose("Warning: keysize mismatch for client_host_key: " "actual %d, announced %d", BN_num_bits(client_host_key->n), bits); packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type); authenticated = auth_rhosts_rsa(pw, client_user, client_host_key); RSA_free(client_host_key); snprintf(info, sizeof info, " ruser %.100s", client_user); break; case SSH_CMSG_AUTH_RSA: if (!options.rsa_authentication) { verbose("RSA authentication disabled."); break; } /* RSA authentication requested. */ n = BN_new(); packet_get_bignum(n, &nlen); packet_integrity_check(plen, nlen, type); authenticated = auth_rsa(pw, n); BN_clear_free(n); break; case SSH_CMSG_AUTH_PASSWORD: if (!options.password_authentication) { verbose("Password authentication disabled."); break; } /* * Read user password. It is in plain text, but was * transmitted over the encrypted channel so it is * not visible to an outside observer. */ password = packet_get_string(&dlen); packet_integrity_check(plen, 4 + dlen, type); #ifdef USE_PAM /* Do PAM auth with password */ authenticated = auth_pam_password(authctxt, password); #else /* !USE_PAM */ /* Try authentication with the password. */ authenticated = auth_password(authctxt, password); #endif /* USE_PAM */ memset(password, 0, strlen(password)); xfree(password); break; #ifdef USE_PAM case SSH_CMSG_AUTH_TIS: debug("rcvd SSH_CMSG_AUTH_TIS: Trying PAM"); pam_cookie = ipam_start_auth("csshd", pw->pw_name); /* We now have data available to send as a challenge */ if (pam_cookie->num_msg != 1 || (pam_cookie->msg[0]->msg_style != PAM_PROMPT_ECHO_OFF && pam_cookie->msg[0]->msg_style != PAM_PROMPT_ECHO_ON)) { /* We got several challenges or an unknown challenge type */ ipam_free_cookie(pam_cookie); pam_cookie = NULL; break; } packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); packet_put_string(pam_cookie->msg[0]->msg, strlen(pam_cookie->msg[0]->msg)); packet_send(); packet_write_wait(); continue; case SSH_CMSG_AUTH_TIS_RESPONSE: debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); if (pam_cookie == NULL) break; { char *response = packet_get_string(&dlen); packet_integrity_check(plen, 4 + dlen, type); pam_cookie->resp[0]->resp = strdup(response); xfree(response); authenticated = ipam_complete_auth(pam_cookie); ipam_free_cookie(pam_cookie); pam_cookie = NULL; } break; #elif defined(SKEY) case SSH_CMSG_AUTH_TIS: debug("rcvd SSH_CMSG_AUTH_TIS"); if (options.challenge_reponse_authentication == 1) { char *challenge = get_challenge(authctxt, authctxt->style); if (challenge != NULL) { debug("sending challenge '%s'", challenge); packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); packet_put_cstring(challenge); packet_send(); packet_write_wait(); continue; } } break; case SSH_CMSG_AUTH_TIS_RESPONSE: debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); if (options.challenge_reponse_authentication == 1) { char *response = packet_get_string(&dlen); debug("got response '%s'", response); packet_integrity_check(plen, 4 + dlen, type); authenticated = verify_response(authctxt, response); memset(response, 'r', dlen); xfree(response); } break; #else case SSH_CMSG_AUTH_TIS: /* TIS Authentication is unsupported */ log("TIS authentication unsupported."); break; #endif #ifdef KRB5 case SSH_CMSG_HAVE_KERBEROS_TGT: /* Passing krb5 ticket */ if (!options.krb5_tgt_passing /*|| !options.krb5_authentication */) { verbose("Kerberos v5 tgt passing disabled."); break; } if (tkt_client == NULL) { /* passing tgt without krb5 authentication */ } { krb5_data tgt; u_int tgtlen; tgt.data = packet_get_string(&tgtlen); tgt.length = tgtlen; if (!auth_krb5_tgt(pw->pw_name, &tgt, tkt_client)) verbose ("Kerberos V5 TGT refused for %.100s", pw->pw_name); xfree(tgt.data); break; } #endif /* KRB5 */ default: /* * Any unknown messages will be ignored (and failure * returned) during authentication. */ log("Unknown message during authentication: type %d", type); break; } #ifdef HAVE_LOGIN_CAP if (pw != NULL) { lc = login_getpwclass(pw); if (lc == NULL) lc = login_getclassbyname(NULL, pw); if (!auth_hostok(lc, from_host, from_ip)) { log("Denied connection for %.200s from %.200s [%.200s].", pw->pw_name, from_host, from_ip); packet_disconnect("Sorry, you are not allowed to connect."); } if (!auth_timeok(lc, time(NULL))) { log("LOGIN %.200s REFUSED (TIME) FROM %.200s", pw->pw_name, from_host); packet_disconnect("Logins not available right now."); } login_close(lc); lc = NULL; } #endif /* HAVE_LOGIN_CAP */ #ifdef LOGIN_ACCESS if (pw != NULL && !login_access(pw->pw_name, from_host)) { log("Denied connection for %.200s from %.200s [%.200s].", pw->pw_name, from_host, from_ip); packet_disconnect("Sorry, you are not allowed to connect."); } #endif /* LOGIN_ACCESS */ #ifdef BSD_AUTH if (authctxt->as) { auth_close(authctxt->as); authctxt->as = NULL; } #endif if (!authctxt->valid && authenticated) fatal("INTERNAL ERROR: authenticated invalid user %s", authctxt->user); /* Special handling for root */ if (authenticated && authctxt->pw->pw_uid == 0 && !auth_root_allowed(get_authname(type))) authenticated = 0; if (pw != NULL && pw->pw_uid == 0) log("ROOT LOGIN as '%.100s' from %.100s", pw->pw_name, get_canonical_hostname(options.reverse_mapping_check)); /* Log before sending the reply */ auth_log(authctxt, authenticated, get_authname(type), info); #ifdef USE_PAM if (authenticated && !do_pam_account(pw->pw_name, client_user)) authenticated = 0; #endif if (client_user != NULL) { xfree(client_user); client_user = NULL; } if (authenticated) return; if (authctxt->failures++ > AUTH_FAIL_MAX) packet_disconnect(AUTH_FAIL_MSG, authctxt->user); packet_start(SSH_SMSG_FAILURE); packet_send(); packet_write_wait(); } } /* * Performs authentication of an incoming connection. Session key has already * been exchanged and encryption is enabled. */ void do_authentication() { Authctxt *authctxt; struct passwd *pw; int plen; u_int ulen; char *user, *style = NULL; /* 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); if ((style = strchr(user, ':')) != NULL) *style++ = 0; authctxt = authctxt_new(); authctxt->user = user; authctxt->style = style; /* Verify that the user is a valid user. */ pw = getpwnam(user); if (pw && allowed_user(pw)) { authctxt->valid = 1; pw = pwcopy(pw); } else { debug("do_authentication: illegal user %s", user); pw = NULL; } authctxt->pw = pw; #ifdef USE_PAM if (pw != NULL) start_pam(pw); #endif setproctitle("%s", pw ? user : "unknown"); /* * If we are not running as root, the user must have the same uid as * the server. */ if (getuid() != 0 && pw && pw->pw_uid != getuid()) packet_disconnect("Cannot change user when server not running as root."); /* * Loop until the user has been authenticated or the connection is * closed, do_authloop() returns only if authentication is successful */ do_authloop(authctxt); /* The user has been authenticated and accepted. */ packet_start(SSH_SMSG_SUCCESS); packet_send(); packet_write_wait(); /* Perform session preparation. */ do_authenticated(authctxt); }