/* * 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 1.55 2003/11/08 16:02:40 jakob Exp $"); RCSID("$FreeBSD$"); #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 "channels.h" #include "session.h" #include "uidswap.h" #include "monitor_wrap.h" /* import */ extern ServerOptions options; /* * convert ssh auth msg type into description */ static 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"; } 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 */ static void do_authloop(Authctxt *authctxt) { int authenticated = 0; u_int bits; Key *client_host_key; BIGNUM *n; char *client_user, *password; char info[1024]; u_int dlen; u_int ulen; int prev, type = 0; struct passwd *pw = authctxt->pw; 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 && #ifdef KRB5 (!options.kerberos_authentication || options.kerberos_or_local_passwd) && #endif PRIVSEP(auth_password(authctxt, ""))) { 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. */ prev = type; type = packet_read(); /* * If we started challenge-response authentication but the * next packet is not a response to our challenge, release * the resources allocated by get_challenge() (which would * normally have been released by verify_response() had we * received such a response) */ if (prev == SSH_CMSG_AUTH_TIS && type != SSH_CMSG_AUTH_TIS_RESPONSE) abandon_challenge_response(authctxt); /* Process the packet. */ switch (type) { 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 = key_new(KEY_RSA1); bits = packet_get_int(); packet_get_bignum(client_host_key->rsa->e); packet_get_bignum(client_host_key->rsa->n); if (bits != BN_num_bits(client_host_key->rsa->n)) verbose("Warning: keysize mismatch for client_host_key: " "actual %d, announced %d", BN_num_bits(client_host_key->rsa->n), bits); packet_check_eom(); authenticated = auth_rhosts_rsa(authctxt, client_user, client_host_key); key_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. */ if ((n = BN_new()) == NULL) fatal("do_authloop: BN_new failed"); packet_get_bignum(n); packet_check_eom(); authenticated = auth_rsa(authctxt, 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_check_eom(); /* Try authentication with the password. */ authenticated = PRIVSEP(auth_password(authctxt, password)); memset(password, 0, strlen(password)); xfree(password); break; case SSH_CMSG_AUTH_TIS: debug("rcvd SSH_CMSG_AUTH_TIS"); if (options.challenge_response_authentication == 1) { char *challenge = get_challenge(authctxt); if (challenge != NULL) { debug("sending challenge '%s'", challenge); packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE); packet_put_cstring(challenge); xfree(challenge); packet_send(); packet_write_wait(); continue; } } break; case SSH_CMSG_AUTH_TIS_RESPONSE: debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE"); if (options.challenge_response_authentication == 1) { char *response = packet_get_string(&dlen); packet_check_eom(); authenticated = verify_response(authctxt, response); memset(response, 'r', dlen); xfree(response); } break; default: /* * Any unknown messages will be ignored (and failure * returned) during authentication. */ logit("Unknown message during authentication: type %d", type); break; } #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); #ifdef _UNICOS if (authenticated && cray_access_denied(authctxt->user)) { authenticated = 0; fatal("Access denied for user %s.",authctxt->user); } #endif /* _UNICOS */ #ifdef HAVE_CYGWIN if (authenticated && !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) { packet_disconnect("Authentication rejected for uid %d.", pw == NULL ? -1 : pw->pw_uid); authenticated = 0; } #else /* Special handling for root */ if (authenticated && authctxt->pw->pw_uid == 0 && !auth_root_allowed(get_authname(type))) authenticated = 0; #endif #ifdef USE_PAM if (options.use_pam && authenticated && !PRIVSEP(do_pam_account())) authenticated = 0; #endif /* Log before sending the reply */ auth_log(authctxt, authenticated, get_authname(type), info); 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) { u_int ulen; char *user, *style = NULL; /* Get the name of the user that we wish to log in as. */ packet_read_expect(SSH_CMSG_USER); /* Get the user name. */ user = packet_get_string(&ulen); packet_check_eom(); if ((style = strchr(user, ':')) != NULL) *style++ = '\0'; authctxt->user = user; authctxt->style = style; /* Verify that the user is a valid user. */ if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL) authctxt->valid = 1; else { debug("do_authentication: illegal user %s", user); authctxt->pw = fakepw(); } setproctitle("%s%s", authctxt->pw ? user : "unknown", use_privsep ? " [net]" : ""); #ifdef USE_PAM if (options.use_pam) PRIVSEP(start_pam(user)); #endif /* * If we are not running as root, the user must have the same uid as * the server. (Unless you are running Windows) */ #ifndef HAVE_CYGWIN if (!use_privsep && getuid() != 0 && authctxt->pw && authctxt->pw->pw_uid != getuid()) packet_disconnect("Cannot change user when server not running as root."); #endif /* * 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(); }