| /* |
| * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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 1.58 2004/07/21 10:33:31 djm Exp $"); |
| |
| #include "xmalloc.h" |
| #include "rsa.h" |
| #include "ssh1.h" |
| #include "packet.h" |
| #include "buffer.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; |
| |
| 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, ""))) { |
| #ifdef USE_PAM |
| if (options.use_pam && (PRIVSEP(do_pam_account()))) |
| #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. */ |
| 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, |
| authctxt->pw)) { |
| packet_disconnect("Authentication rejected for uid %d.", |
| authctxt->pw == NULL ? -1 : authctxt->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++ > options.max_authtries) |
| 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->valid ? user : "unknown", |
| use_privsep ? " [net]" : ""); |
| |
| #ifdef USE_PAM |
| if (options.use_pam) |
| PRIVSEP(start_pam(authctxt)); |
| #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(); |
| } |