From 4230a5dc305d1b39bc118befcc1ccfe933281b75 Mon Sep 17 00:00:00 2001 From: Darren Tucker Date: Wed, 2 Jul 2008 22:56:09 +1000 Subject: - djm@cvs.openbsd.org 2008/07/02 12:36:39 [auth2-none.c auth2.c] Make protocol 2 MaxAuthTries behaviour a little more sensible: Check whether client has exceeded MaxAuthTries before running an authentication method and skip it if they have, previously it would always allow one try (for "none" auth). Preincrement failure count before post-auth test - previously this checked and postincremented, also to allow one "none" try. Together, these two changes always count the "none" auth method which could be skipped by a malicious client (e.g. an SSH worm) to get an extra attempt at a real auth method. They also make MaxAuthTries=0 a useful way to block users entirely (esp. in a sshd_config Match block). Also, move sending of any preauth banner from "none" auth method to the first call to input_userauth_request(), so worms that skip the "none" method get to see it too. --- auth2-none.c | 72 +++--------------------------------------------------------- 1 file changed, 3 insertions(+), 69 deletions(-) (limited to 'auth2-none.c') diff --git a/auth2-none.c b/auth2-none.c index 28e593e6..10accfe5 100644 --- a/auth2-none.c +++ b/auth2-none.c @@ -1,4 +1,4 @@ -/* $OpenBSD: auth2-none.c,v 1.14 2007/08/23 03:22:16 djm Exp $ */ +/* $OpenBSD: auth2-none.c,v 1.15 2008/07/02 12:36:39 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * @@ -31,9 +31,10 @@ #include #include -#include #include +#include +#include "atomicio.h" #include "xmalloc.h" #include "key.h" #include "hostfile.h" @@ -42,7 +43,6 @@ #include "log.h" #include "buffer.h" #include "servconf.h" -#include "atomicio.h" #include "compat.h" #include "ssh2.h" #ifdef GSSAPI @@ -56,77 +56,11 @@ extern ServerOptions options; /* "none" is allowed only one time */ static int none_enabled = 1; -char * -auth2_read_banner(void) -{ - struct stat st; - char *banner = NULL; - size_t len, n; - int fd; - - if ((fd = open(options.banner, O_RDONLY)) == -1) - return (NULL); - if (fstat(fd, &st) == -1) { - close(fd); - return (NULL); - } - if (st.st_size > 1*1024*1024) { - close(fd); - return (NULL); - } - - len = (size_t)st.st_size; /* truncate */ - banner = xmalloc(len + 1); - n = atomicio(read, fd, banner, len); - close(fd); - - if (n != len) { - xfree(banner); - return (NULL); - } - banner[n] = '\0'; - - return (banner); -} - -void -userauth_send_banner(const char *msg) -{ - if (datafellows & SSH_BUG_BANNER) - return; - - packet_start(SSH2_MSG_USERAUTH_BANNER); - packet_put_cstring(msg); - packet_put_cstring(""); /* language, unused */ - packet_send(); - debug("%s: sent", __func__); -} - -static void -userauth_banner(void) -{ - char *banner = NULL; - - if (options.banner == NULL || - strcasecmp(options.banner, "none") == 0 || - (datafellows & SSH_BUG_BANNER) != 0) - return; - - if ((banner = PRIVSEP(auth2_read_banner())) == NULL) - goto done; - userauth_send_banner(banner); - -done: - if (banner) - xfree(banner); -} - static int userauth_none(Authctxt *authctxt) { none_enabled = 0; packet_check_eom(); - userauth_banner(); #ifdef HAVE_CYGWIN if (check_nt_auth(1, authctxt->pw) == 0) return (0); -- cgit v1.2.1