upstream commit
Add a new authorized_keys option "restrict" that
includes all current and future key restrictions (no-*-forwarding, etc). Also
add permissive versions of the existing restrictions, e.g. "no-pty" -> "pty".
This simplifies the task of setting up restricted keys and ensures they are
maximally-restricted, regardless of any permissions we might implement in the
future.
Example:
restrict,pty,command="nethack" ssh-ed25519 AAAAC3NzaC1lZDI1...
Idea from Jann Horn; ok markus@
Upstream-ID: 04ceb9d448e46e67e13887a7ae5ea45b4f1719d0
diff --git a/auth-options.c b/auth-options.c
index e387697..cb68802 100644
--- a/auth-options.c
+++ b/auth-options.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth-options.c,v 1.68 2015/07/03 03:43:18 djm Exp $ */
+/* $OpenBSD: auth-options.c,v 1.69 2015/11/16 00:30:02 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -88,6 +88,36 @@
}
/*
+ * Match flag 'opt' in *optsp, and if allow_negate is set then also match
+ * 'no-opt'. Returns -1 if option not matched, 1 if option matches or 0
+ * if negated option matches.
+ * If the option or negated option matches, then *optsp is updated to
+ * point to the first character after the option and, if 'msg' is not NULL
+ * then a message based on it added via auth_debug_add().
+ */
+static int
+match_flag(const char *opt, int allow_negate, char **optsp, const char *msg)
+{
+ size_t opt_len = strlen(opt);
+ char *opts = *optsp;
+ int negate = 0;
+
+ if (allow_negate && strncasecmp(opts, "no-", 3) == 0) {
+ opts += 3;
+ negate = 1;
+ }
+ if (strncasecmp(opts, opt, opt_len) == 0) {
+ *optsp = opts + opt_len;
+ if (msg != NULL) {
+ auth_debug_add("%s %s.", msg,
+ negate ? "disabled" : "enabled");
+ }
+ return negate ? 0 : 1;
+ }
+ return -1;
+}
+
+/*
* return 1 if access is granted, 0 if not.
* side effect: sets key option flags
*/
@@ -95,7 +125,7 @@
auth_parse_options(struct passwd *pw, char *opts, char *file, u_long linenum)
{
const char *cp;
- int i;
+ int i, r;
/* reset options */
auth_clear_options();
@@ -104,45 +134,42 @@
return 1;
while (*opts && *opts != ' ' && *opts != '\t') {
- cp = "cert-authority";
- if (strncasecmp(opts, cp, strlen(cp)) == 0) {
- key_is_cert_authority = 1;
- opts += strlen(cp);
+ if ((r = match_flag("cert-authority", 0, &opts, NULL)) != -1) {
+ key_is_cert_authority = r;
goto next_option;
}
- cp = "no-port-forwarding";
- if (strncasecmp(opts, cp, strlen(cp)) == 0) {
- auth_debug_add("Port forwarding disabled.");
+ if ((r = match_flag("restrict", 0, &opts, NULL)) != -1) {
+ auth_debug_add("Key is restricted.");
no_port_forwarding_flag = 1;
- opts += strlen(cp);
- goto next_option;
- }
- cp = "no-agent-forwarding";
- if (strncasecmp(opts, cp, strlen(cp)) == 0) {
- auth_debug_add("Agent forwarding disabled.");
no_agent_forwarding_flag = 1;
- opts += strlen(cp);
- goto next_option;
- }
- cp = "no-X11-forwarding";
- if (strncasecmp(opts, cp, strlen(cp)) == 0) {
- auth_debug_add("X11 forwarding disabled.");
no_x11_forwarding_flag = 1;
- opts += strlen(cp);
- goto next_option;
- }
- cp = "no-pty";
- if (strncasecmp(opts, cp, strlen(cp)) == 0) {
- auth_debug_add("Pty allocation disabled.");
no_pty_flag = 1;
- opts += strlen(cp);
+ no_user_rc = 1;
goto next_option;
}
- cp = "no-user-rc";
- if (strncasecmp(opts, cp, strlen(cp)) == 0) {
- auth_debug_add("User rc file execution disabled.");
- no_user_rc = 1;
- opts += strlen(cp);
+ if ((r = match_flag("port-forwarding", 1, &opts,
+ "Port forwarding")) != -1) {
+ no_port_forwarding_flag = r != 1;
+ goto next_option;
+ }
+ if ((r = match_flag("agent-forwarding", 1, &opts,
+ "Agent forwarding")) != -1) {
+ no_agent_forwarding_flag = r != 1;
+ goto next_option;
+ }
+ if ((r = match_flag("x11-forwarding", 1, &opts,
+ "X11 forwarding")) != -1) {
+ no_x11_forwarding_flag = r != 1;
+ goto next_option;
+ }
+ if ((r = match_flag("pty", 1, &opts,
+ "PTY allocation")) != -1) {
+ no_pty_flag = r != 1;
+ goto next_option;
+ }
+ if ((r = match_flag("user-rc", 1, &opts,
+ "User rc execution")) != -1) {
+ no_user_rc = r != 1;
goto next_option;
}
cp = "command=\"";