upstream: add a "no-touch-required" option for authorized_keys and

a similar extension for certificates. This option disables the default
requirement that security key signatures attest that the user touched their
key to authorize them.

feedback deraadt, ok markus

OpenBSD-Commit-ID: f1fb56151ba68d55d554d0f6d3d4dba0cf1a452e

1 files changed, 26 insertions, 12 deletions

diff --git a/auth-options.c b/auth-options.c
index 90b0d7f25..2d200944c 100644
--- a/auth-options.c
+++ b/auth-options.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth-options.c,v 1.89 2019/09/13 04:36:43 dtucker Exp $ */
+/* $OpenBSD: auth-options.c,v 1.90 2019/11/25 00:54:23 djm Exp $ */
 /*
  * Copyright (c) 2018 Damien Miller <djm@mindrot.org>
  *
@@ -96,7 +96,10 @@ cert_option_list(struct sshauthopt *opts, struct sshbuf *oblob,
                     name, sshbuf_len(data));
                 found = 0;
                 if ((which & OPTIONS_EXTENSIONS) != 0) {
-                        if (strcmp(name, "permit-X11-forwarding") == 0) {
+                        if (strcmp(name, "no-touch-required") == 0) {
+                                opts->no_require_user_presence = 1;
+                                found = 1;
+                        } else if (strcmp(name, "permit-X11-forwarding") == 0) {
                                 opts->permit_x11_forwarding_flag = 1;
                                 found = 1;
                         } else if (strcmp(name,
@@ -347,6 +350,8 @@ sshauthopt_parse(const char *opts, const char **errstrp)
                         ret->permit_agent_forwarding_flag = r == 1;
                 } else if ((r = opt_flag("x11-forwarding", 1, &opts)) != -1) {
                         ret->permit_x11_forwarding_flag = r == 1;
+                } else if ((r = opt_flag("touch-required", 1, &opts)) != -1) {
+                        ret->no_require_user_presence = r != 1; /* NB. flip */
                 } else if ((r = opt_flag("pty", 1, &opts)) != -1) {
                         ret->permit_pty_flag = r == 1;
                 } else if ((r = opt_flag("user-rc", 1, &opts)) != -1) {
@@ -567,14 +572,15 @@ sshauthopt_merge(const struct sshauthopt *primary,
                         goto alloc_fail;
         }
 
-        /* Flags are logical-AND (i.e. must be set in both for permission) */
-#define OPTFLAG(x) ret->x = (primary->x == 1) && (additional->x == 1)
-        OPTFLAG(permit_port_forwarding_flag);
-        OPTFLAG(permit_agent_forwarding_flag);
-        OPTFLAG(permit_x11_forwarding_flag);
-        OPTFLAG(permit_pty_flag);
-        OPTFLAG(permit_user_rc);
-#undef OPTFLAG
+#define OPTFLAG_AND(x) ret->x = (primary->x == 1) && (additional->x == 1)
+        /* Permissive flags are logical-AND (i.e. must be set in both) */
+        OPTFLAG_AND(permit_port_forwarding_flag);
+        OPTFLAG_AND(permit_agent_forwarding_flag);
+        OPTFLAG_AND(permit_x11_forwarding_flag);
+        OPTFLAG_AND(permit_pty_flag);
+        OPTFLAG_AND(permit_user_rc);
+        OPTFLAG_AND(no_require_user_presence);
+#undef OPTFLAG_AND
 
         /* Earliest expiry time should win */
         if (primary->valid_before != 0)
@@ -643,6 +649,7 @@ sshauthopt_copy(const struct sshauthopt *orig)
         OPTSCALAR(cert_authority);
         OPTSCALAR(force_tun_device);
         OPTSCALAR(valid_before);
+        OPTSCALAR(no_require_user_presence);
 #undef OPTSCALAR
 #define OPTSTRING(x) \
         do { \
@@ -765,7 +772,7 @@ sshauthopt_serialise(const struct sshauthopt *opts, struct sshbuf *m,
 {
         int r = SSH_ERR_INTERNAL_ERROR;
 
-        /* Flag and simple integer options */
+        /* Flag options */
         if ((r = sshbuf_put_u8(m, opts->permit_port_forwarding_flag)) != 0 ||
             (r = sshbuf_put_u8(m, opts->permit_agent_forwarding_flag)) != 0 ||
             (r = sshbuf_put_u8(m, opts->permit_x11_forwarding_flag)) != 0 ||
@@ -773,7 +780,11 @@ sshauthopt_serialise(const struct sshauthopt *opts, struct sshbuf *m,
             (r = sshbuf_put_u8(m, opts->permit_user_rc)) != 0 ||
             (r = sshbuf_put_u8(m, opts->restricted)) != 0 ||
             (r = sshbuf_put_u8(m, opts->cert_authority)) != 0 ||
-            (r = sshbuf_put_u64(m, opts->valid_before)) != 0)
+            (r = sshbuf_put_u8(m, opts->no_require_user_presence)) != 0)
+                return r;
+
+        /* Simple integer options */
+        if ((r = sshbuf_put_u64(m, opts->valid_before)) != 0)
                 return r;
 
         /* tunnel number can be negative to indicate "unset" */
@@ -817,6 +828,7 @@ sshauthopt_deserialise(struct sshbuf *m, struct sshauthopt **optsp)
         if ((opts = calloc(1, sizeof(*opts))) == NULL)
                 return SSH_ERR_ALLOC_FAIL;
 
+        /* Flag options */
 #define OPT_FLAG(x) \
         do { \
                 if ((r = sshbuf_get_u8(m, &f)) != 0) \
@@ -830,8 +842,10 @@ sshauthopt_deserialise(struct sshbuf *m, struct sshauthopt **optsp)
         OPT_FLAG(permit_user_rc);
         OPT_FLAG(restricted);
         OPT_FLAG(cert_authority);
+        OPT_FLAG(no_require_user_presence);
 #undef OPT_FLAG
 
+        /* Simple integer options */
         if ((r = sshbuf_get_u64(m, &opts->valid_before)) != 0)
                 goto out;