Commit 4230a5dc authored by Darren Tucker's avatar Darren Tucker

- 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.
parent 33c787f2
......@@ -33,6 +33,22 @@
Merge duplicate host key file checks, based in part on a patch from Rob
Holland via bz #1348 . Also checks for non-regular files during protocol
1 RSA auth. ok djm@
- 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.
20080630
- (djm) OpenBSD CVS Sync
......@@ -4516,4 +4532,4 @@
OpenServer 6 and add osr5bigcrypt support so when someone migrates
passwords between UnixWare and OpenServer they will still work. OK dtucker@
$Id: ChangeLog,v 1.5047 2008/07/02 12:37:30 dtucker Exp $
$Id: ChangeLog,v 1.5048 2008/07/02 12:56:09 dtucker Exp $
/* $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 <fcntl.h>
#include <stdarg.h>
#include <unistd.h>
#include <string.h>
#include <unistd.h>
#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);
......
/* $OpenBSD: auth2.c,v 1.116 2007/09/29 00:25:51 dtucker Exp $ */
/* $OpenBSD: auth2.c,v 1.117 2008/07/02 12:36:39 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
*
......@@ -26,10 +26,14 @@
#include "includes.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <fcntl.h>
#include <pwd.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include "xmalloc.h"
#include "ssh2.h"
......@@ -88,10 +92,74 @@ static void input_userauth_request(int, u_int32_t, void *);
static Authmethod *authmethod_lookup(const char *);
static char *authmethods_get(void);
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);
}
/*
* loop until authctxt->success == TRUE
*/
void
do_authentication2(Authctxt *authctxt)
{
......@@ -179,6 +247,7 @@ input_userauth_request(int type, u_int32_t seq, void *ctxt)
authctxt->style = style ? xstrdup(style) : NULL;
if (use_privsep)
mm_inform_authserv(service, style);
userauth_banner();
} else if (strcmp(user, authctxt->user) != 0 ||
strcmp(service, authctxt->service) != 0) {
packet_disconnect("Change of username or service not allowed: "
......@@ -197,7 +266,7 @@ input_userauth_request(int type, u_int32_t seq, void *ctxt)
/* try to authenticate user */
m = authmethod_lookup(method);
if (m != NULL) {
if (m != NULL && authctxt->failures < options.max_authtries) {
debug2("input_userauth_request: try method %s", method);
authenticated = m->userauth(authctxt);
}
......@@ -264,7 +333,7 @@ userauth_finish(Authctxt *authctxt, int authenticated, char *method)
/* now we can break out */
authctxt->success = 1;
} else {
if (authctxt->failures++ > options.max_authtries) {
if (++authctxt->failures > options.max_authtries) {
#ifdef SSH_AUDIT_EVENTS
PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
#endif
......@@ -320,3 +389,4 @@ authmethod_lookup(const char *name)
name ? name : "NULL");
return NULL;
}
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment