659 lines
17 KiB
C
659 lines
17 KiB
C
/* $OpenBSD: auth-options.c,v 1.73 2017/05/31 10:54:00 markus Exp $ */
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/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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* As far as I am concerned, the code I have written for this software
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* can be used freely for any purpose. Any derived versions of this
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* software must be clearly marked as such, and if the derived work is
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* incompatible with the protocol description in the RFC file, it must be
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* called by a name other than "ssh" or "Secure Shell".
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*/
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#include "includes.h"
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#include <sys/types.h>
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#include <netdb.h>
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#include <pwd.h>
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#include <string.h>
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#include <stdio.h>
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#include <stdarg.h>
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#include "openbsd-compat/sys-queue.h"
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#include "key.h" /* XXX for typedef */
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#include "buffer.h" /* XXX for typedef */
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#include "xmalloc.h"
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#include "match.h"
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#include "ssherr.h"
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#include "log.h"
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#include "canohost.h"
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#include "packet.h"
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#include "sshbuf.h"
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#include "misc.h"
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#include "channels.h"
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#include "servconf.h"
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#include "sshkey.h"
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#include "auth-options.h"
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#include "hostfile.h"
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#include "auth.h"
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/* Flags set authorized_keys flags */
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int no_port_forwarding_flag = 0;
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int no_agent_forwarding_flag = 0;
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int no_x11_forwarding_flag = 0;
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int no_pty_flag = 0;
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int no_user_rc = 0;
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int key_is_cert_authority = 0;
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/* "command=" option. */
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char *forced_command = NULL;
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/* "environment=" options. */
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struct envstring *custom_environment = NULL;
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/* "tunnel=" option. */
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int forced_tun_device = -1;
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/* "principals=" option. */
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char *authorized_principals = NULL;
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extern ServerOptions options;
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void
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auth_clear_options(void)
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{
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no_agent_forwarding_flag = 0;
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no_port_forwarding_flag = 0;
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no_pty_flag = 0;
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no_x11_forwarding_flag = 0;
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no_user_rc = 0;
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key_is_cert_authority = 0;
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while (custom_environment) {
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struct envstring *ce = custom_environment;
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custom_environment = ce->next;
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free(ce->s);
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free(ce);
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}
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free(forced_command);
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forced_command = NULL;
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free(authorized_principals);
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authorized_principals = NULL;
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forced_tun_device = -1;
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channel_clear_permitted_opens();
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}
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/*
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* Match flag 'opt' in *optsp, and if allow_negate is set then also match
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* 'no-opt'. Returns -1 if option not matched, 1 if option matches or 0
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* if negated option matches.
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* If the option or negated option matches, then *optsp is updated to
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* point to the first character after the option and, if 'msg' is not NULL
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* then a message based on it added via auth_debug_add().
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*/
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static int
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match_flag(const char *opt, int allow_negate, char **optsp, const char *msg)
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{
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size_t opt_len = strlen(opt);
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char *opts = *optsp;
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int negate = 0;
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if (allow_negate && strncasecmp(opts, "no-", 3) == 0) {
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opts += 3;
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negate = 1;
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}
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if (strncasecmp(opts, opt, opt_len) == 0) {
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*optsp = opts + opt_len;
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if (msg != NULL) {
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auth_debug_add("%s %s.", msg,
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negate ? "disabled" : "enabled");
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}
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return negate ? 0 : 1;
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}
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return -1;
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}
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/*
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* return 1 if access is granted, 0 if not.
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* side effect: sets key option flags
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*/
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int
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auth_parse_options(struct passwd *pw, char *opts, const char *file,
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u_long linenum)
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{
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struct ssh *ssh = active_state; /* XXX */
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const char *cp;
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int i, r;
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/* reset options */
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auth_clear_options();
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if (!opts)
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return 1;
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while (*opts && *opts != ' ' && *opts != '\t') {
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if ((r = match_flag("cert-authority", 0, &opts, NULL)) != -1) {
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key_is_cert_authority = r;
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goto next_option;
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}
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if ((r = match_flag("restrict", 0, &opts, NULL)) != -1) {
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auth_debug_add("Key is restricted.");
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no_port_forwarding_flag = 1;
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no_agent_forwarding_flag = 1;
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no_x11_forwarding_flag = 1;
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no_pty_flag = 1;
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no_user_rc = 1;
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goto next_option;
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}
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if ((r = match_flag("port-forwarding", 1, &opts,
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"Port forwarding")) != -1) {
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no_port_forwarding_flag = r != 1;
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goto next_option;
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}
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if ((r = match_flag("agent-forwarding", 1, &opts,
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"Agent forwarding")) != -1) {
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no_agent_forwarding_flag = r != 1;
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goto next_option;
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}
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if ((r = match_flag("x11-forwarding", 1, &opts,
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"X11 forwarding")) != -1) {
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no_x11_forwarding_flag = r != 1;
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goto next_option;
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}
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if ((r = match_flag("pty", 1, &opts,
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"PTY allocation")) != -1) {
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no_pty_flag = r != 1;
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goto next_option;
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}
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if ((r = match_flag("user-rc", 1, &opts,
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"User rc execution")) != -1) {
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no_user_rc = r != 1;
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goto next_option;
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}
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cp = "command=\"";
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if (strncasecmp(opts, cp, strlen(cp)) == 0) {
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opts += strlen(cp);
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free(forced_command);
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forced_command = xmalloc(strlen(opts) + 1);
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i = 0;
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while (*opts) {
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if (*opts == '"')
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break;
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if (*opts == '\\' && opts[1] == '"') {
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opts += 2;
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forced_command[i++] = '"';
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continue;
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}
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forced_command[i++] = *opts++;
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}
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if (!*opts) {
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debug("%.100s, line %lu: missing end quote",
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file, linenum);
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auth_debug_add("%.100s, line %lu: missing end quote",
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file, linenum);
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free(forced_command);
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forced_command = NULL;
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goto bad_option;
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}
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forced_command[i] = '\0';
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auth_debug_add("Forced command.");
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opts++;
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goto next_option;
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}
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cp = "principals=\"";
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if (strncasecmp(opts, cp, strlen(cp)) == 0) {
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opts += strlen(cp);
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free(authorized_principals);
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authorized_principals = xmalloc(strlen(opts) + 1);
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i = 0;
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while (*opts) {
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if (*opts == '"')
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break;
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if (*opts == '\\' && opts[1] == '"') {
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opts += 2;
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authorized_principals[i++] = '"';
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continue;
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}
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authorized_principals[i++] = *opts++;
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}
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if (!*opts) {
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debug("%.100s, line %lu: missing end quote",
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file, linenum);
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auth_debug_add("%.100s, line %lu: missing end quote",
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file, linenum);
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free(authorized_principals);
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authorized_principals = NULL;
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goto bad_option;
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}
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authorized_principals[i] = '\0';
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auth_debug_add("principals: %.900s",
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authorized_principals);
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opts++;
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goto next_option;
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}
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cp = "environment=\"";
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if (strncasecmp(opts, cp, strlen(cp)) == 0) {
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char *s;
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struct envstring *new_envstring;
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opts += strlen(cp);
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s = xmalloc(strlen(opts) + 1);
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i = 0;
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while (*opts) {
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if (*opts == '"')
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break;
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if (*opts == '\\' && opts[1] == '"') {
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opts += 2;
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s[i++] = '"';
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continue;
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}
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s[i++] = *opts++;
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}
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if (!*opts) {
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debug("%.100s, line %lu: missing end quote",
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file, linenum);
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auth_debug_add("%.100s, line %lu: missing end quote",
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file, linenum);
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free(s);
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goto bad_option;
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}
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s[i] = '\0';
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opts++;
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if (options.permit_user_env) {
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auth_debug_add("Adding to environment: "
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"%.900s", s);
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debug("Adding to environment: %.900s", s);
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new_envstring = xcalloc(1,
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sizeof(*new_envstring));
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new_envstring->s = s;
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new_envstring->next = custom_environment;
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custom_environment = new_envstring;
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s = NULL;
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}
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free(s);
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goto next_option;
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}
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cp = "from=\"";
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if (strncasecmp(opts, cp, strlen(cp)) == 0) {
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const char *remote_ip = ssh_remote_ipaddr(ssh);
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const char *remote_host = auth_get_canonical_hostname(
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ssh, options.use_dns);
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char *patterns = xmalloc(strlen(opts) + 1);
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opts += strlen(cp);
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i = 0;
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while (*opts) {
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if (*opts == '"')
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break;
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if (*opts == '\\' && opts[1] == '"') {
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opts += 2;
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patterns[i++] = '"';
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continue;
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}
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patterns[i++] = *opts++;
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}
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if (!*opts) {
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debug("%.100s, line %lu: missing end quote",
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file, linenum);
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auth_debug_add("%.100s, line %lu: missing end quote",
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file, linenum);
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free(patterns);
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goto bad_option;
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}
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patterns[i] = '\0';
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opts++;
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switch (match_host_and_ip(remote_host, remote_ip,
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patterns)) {
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case 1:
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free(patterns);
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/* Host name matches. */
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goto next_option;
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case -1:
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debug("%.100s, line %lu: invalid criteria",
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file, linenum);
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auth_debug_add("%.100s, line %lu: "
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"invalid criteria", file, linenum);
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/* FALLTHROUGH */
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case 0:
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free(patterns);
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logit("Authentication tried for %.100s with "
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"correct key but not from a permitted "
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"host (host=%.200s, ip=%.200s).",
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pw->pw_name, remote_host, remote_ip);
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auth_debug_add("Your host '%.200s' is not "
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"permitted to use this key for login.",
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remote_host);
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break;
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}
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/* deny access */
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return 0;
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}
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cp = "permitopen=\"";
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if (strncasecmp(opts, cp, strlen(cp)) == 0) {
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char *host, *p;
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int port;
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char *patterns = xmalloc(strlen(opts) + 1);
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opts += strlen(cp);
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i = 0;
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while (*opts) {
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if (*opts == '"')
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break;
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if (*opts == '\\' && opts[1] == '"') {
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opts += 2;
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patterns[i++] = '"';
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continue;
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}
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patterns[i++] = *opts++;
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}
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if (!*opts) {
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debug("%.100s, line %lu: missing end quote",
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file, linenum);
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auth_debug_add("%.100s, line %lu: missing "
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"end quote", file, linenum);
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free(patterns);
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goto bad_option;
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}
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patterns[i] = '\0';
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opts++;
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p = patterns;
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/* XXX - add streamlocal support */
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host = hpdelim(&p);
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if (host == NULL || strlen(host) >= NI_MAXHOST) {
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debug("%.100s, line %lu: Bad permitopen "
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"specification <%.100s>", file, linenum,
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patterns);
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auth_debug_add("%.100s, line %lu: "
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"Bad permitopen specification", file,
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linenum);
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free(patterns);
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goto bad_option;
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}
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host = cleanhostname(host);
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if (p == NULL || (port = permitopen_port(p)) < 0) {
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debug("%.100s, line %lu: Bad permitopen port "
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"<%.100s>", file, linenum, p ? p : "");
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auth_debug_add("%.100s, line %lu: "
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"Bad permitopen port", file, linenum);
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free(patterns);
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goto bad_option;
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}
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if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0)
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channel_add_permitted_opens(host, port);
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free(patterns);
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goto next_option;
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}
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cp = "tunnel=\"";
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if (strncasecmp(opts, cp, strlen(cp)) == 0) {
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char *tun = NULL;
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opts += strlen(cp);
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tun = xmalloc(strlen(opts) + 1);
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i = 0;
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while (*opts) {
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if (*opts == '"')
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break;
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tun[i++] = *opts++;
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}
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if (!*opts) {
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debug("%.100s, line %lu: missing end quote",
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file, linenum);
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auth_debug_add("%.100s, line %lu: missing end quote",
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file, linenum);
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free(tun);
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forced_tun_device = -1;
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goto bad_option;
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}
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tun[i] = '\0';
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forced_tun_device = a2tun(tun, NULL);
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free(tun);
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if (forced_tun_device == SSH_TUNID_ERR) {
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debug("%.100s, line %lu: invalid tun device",
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file, linenum);
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auth_debug_add("%.100s, line %lu: invalid tun device",
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file, linenum);
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forced_tun_device = -1;
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goto bad_option;
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}
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auth_debug_add("Forced tun device: %d", forced_tun_device);
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opts++;
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goto next_option;
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}
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next_option:
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/*
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* Skip the comma, and move to the next option
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* (or break out if there are no more).
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*/
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if (!*opts)
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fatal("Bugs in auth-options.c option processing.");
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if (*opts == ' ' || *opts == '\t')
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break; /* End of options. */
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if (*opts != ',')
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goto bad_option;
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opts++;
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/* Process the next option. */
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}
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/* grant access */
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return 1;
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bad_option:
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logit("Bad options in %.100s file, line %lu: %.50s",
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file, linenum, opts);
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auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
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file, linenum, opts);
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/* deny access */
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return 0;
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}
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#define OPTIONS_CRITICAL 1
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#define OPTIONS_EXTENSIONS 2
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static int
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parse_option_list(struct sshbuf *oblob, struct passwd *pw,
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u_int which, int crit,
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int *cert_no_port_forwarding_flag,
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int *cert_no_agent_forwarding_flag,
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int *cert_no_x11_forwarding_flag,
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int *cert_no_pty_flag,
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int *cert_no_user_rc,
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char **cert_forced_command,
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int *cert_source_address_done)
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{
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struct ssh *ssh = active_state; /* XXX */
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char *command, *allowed;
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const char *remote_ip;
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char *name = NULL;
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struct sshbuf *c = NULL, *data = NULL;
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int r, ret = -1, result, found;
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if ((c = sshbuf_fromb(oblob)) == NULL) {
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error("%s: sshbuf_fromb failed", __func__);
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goto out;
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}
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while (sshbuf_len(c) > 0) {
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sshbuf_free(data);
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data = NULL;
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if ((r = sshbuf_get_cstring(c, &name, NULL)) != 0 ||
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(r = sshbuf_froms(c, &data)) != 0) {
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error("Unable to parse certificate options: %s",
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ssh_err(r));
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goto out;
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}
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debug3("found certificate option \"%.100s\" len %zu",
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name, sshbuf_len(data));
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found = 0;
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if ((which & OPTIONS_EXTENSIONS) != 0) {
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if (strcmp(name, "permit-X11-forwarding") == 0) {
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*cert_no_x11_forwarding_flag = 0;
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found = 1;
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} else if (strcmp(name,
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"permit-agent-forwarding") == 0) {
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*cert_no_agent_forwarding_flag = 0;
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found = 1;
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} else if (strcmp(name,
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"permit-port-forwarding") == 0) {
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*cert_no_port_forwarding_flag = 0;
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found = 1;
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} else if (strcmp(name, "permit-pty") == 0) {
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*cert_no_pty_flag = 0;
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found = 1;
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} else if (strcmp(name, "permit-user-rc") == 0) {
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*cert_no_user_rc = 0;
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found = 1;
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}
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}
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if (!found && (which & OPTIONS_CRITICAL) != 0) {
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if (strcmp(name, "force-command") == 0) {
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if ((r = sshbuf_get_cstring(data, &command,
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NULL)) != 0) {
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error("Unable to parse \"%s\" "
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"section: %s", name, ssh_err(r));
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goto out;
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}
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if (*cert_forced_command != NULL) {
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error("Certificate has multiple "
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"force-command options");
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free(command);
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goto out;
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}
|
|
*cert_forced_command = command;
|
|
found = 1;
|
|
}
|
|
if (strcmp(name, "source-address") == 0) {
|
|
if ((r = sshbuf_get_cstring(data, &allowed,
|
|
NULL)) != 0) {
|
|
error("Unable to parse \"%s\" "
|
|
"section: %s", name, ssh_err(r));
|
|
goto out;
|
|
}
|
|
if ((*cert_source_address_done)++) {
|
|
error("Certificate has multiple "
|
|
"source-address options");
|
|
free(allowed);
|
|
goto out;
|
|
}
|
|
remote_ip = ssh_remote_ipaddr(ssh);
|
|
result = addr_match_cidr_list(remote_ip,
|
|
allowed);
|
|
free(allowed);
|
|
switch (result) {
|
|
case 1:
|
|
/* accepted */
|
|
break;
|
|
case 0:
|
|
/* no match */
|
|
logit("Authentication tried for %.100s "
|
|
"with valid certificate but not "
|
|
"from a permitted host "
|
|
"(ip=%.200s).", pw->pw_name,
|
|
remote_ip);
|
|
auth_debug_add("Your address '%.200s' "
|
|
"is not permitted to use this "
|
|
"certificate for login.",
|
|
remote_ip);
|
|
goto out;
|
|
case -1:
|
|
default:
|
|
error("Certificate source-address "
|
|
"contents invalid");
|
|
goto out;
|
|
}
|
|
found = 1;
|
|
}
|
|
}
|
|
|
|
if (!found) {
|
|
if (crit) {
|
|
error("Certificate critical option \"%s\" "
|
|
"is not supported", name);
|
|
goto out;
|
|
} else {
|
|
logit("Certificate extension \"%s\" "
|
|
"is not supported", name);
|
|
}
|
|
} else if (sshbuf_len(data) != 0) {
|
|
error("Certificate option \"%s\" corrupt "
|
|
"(extra data)", name);
|
|
goto out;
|
|
}
|
|
free(name);
|
|
name = NULL;
|
|
}
|
|
/* successfully parsed all options */
|
|
ret = 0;
|
|
|
|
out:
|
|
if (ret != 0 &&
|
|
cert_forced_command != NULL &&
|
|
*cert_forced_command != NULL) {
|
|
free(*cert_forced_command);
|
|
*cert_forced_command = NULL;
|
|
}
|
|
free(name);
|
|
sshbuf_free(data);
|
|
sshbuf_free(c);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Set options from critical certificate options. These supersede user key
|
|
* options so this must be called after auth_parse_options().
|
|
*/
|
|
int
|
|
auth_cert_options(struct sshkey *k, struct passwd *pw, const char **reason)
|
|
{
|
|
int cert_no_port_forwarding_flag = 1;
|
|
int cert_no_agent_forwarding_flag = 1;
|
|
int cert_no_x11_forwarding_flag = 1;
|
|
int cert_no_pty_flag = 1;
|
|
int cert_no_user_rc = 1;
|
|
char *cert_forced_command = NULL;
|
|
int cert_source_address_done = 0;
|
|
|
|
*reason = "invalid certificate options";
|
|
|
|
/* Separate options and extensions for v01 certs */
|
|
if (parse_option_list(k->cert->critical, pw,
|
|
OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
|
|
&cert_forced_command,
|
|
&cert_source_address_done) == -1)
|
|
return -1;
|
|
if (parse_option_list(k->cert->extensions, pw,
|
|
OPTIONS_EXTENSIONS, 0,
|
|
&cert_no_port_forwarding_flag,
|
|
&cert_no_agent_forwarding_flag,
|
|
&cert_no_x11_forwarding_flag,
|
|
&cert_no_pty_flag,
|
|
&cert_no_user_rc,
|
|
NULL, NULL) == -1)
|
|
return -1;
|
|
|
|
no_port_forwarding_flag |= cert_no_port_forwarding_flag;
|
|
no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
|
|
no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
|
|
no_pty_flag |= cert_no_pty_flag;
|
|
no_user_rc |= cert_no_user_rc;
|
|
/*
|
|
* Only permit both CA and key option forced-command if they match.
|
|
* Otherwise refuse the certificate.
|
|
*/
|
|
if (cert_forced_command != NULL && forced_command != NULL) {
|
|
if (strcmp(forced_command, cert_forced_command) == 0) {
|
|
free(forced_command);
|
|
forced_command = cert_forced_command;
|
|
} else {
|
|
*reason = "certificate and key options forced command "
|
|
"do not match";
|
|
free(cert_forced_command);
|
|
return -1;
|
|
}
|
|
} else if (cert_forced_command != NULL)
|
|
forced_command = cert_forced_command;
|
|
/* success */
|
|
*reason = NULL;
|
|
return 0;
|
|
}
|
|
|