upstream: when downloading FIDO2 resident keys from a token, don't

prompt for a PIN until the token has told us that it needs one. Avoids
double-prompting on devices that implement on-device authentication (e.g. a
touchscreen PIN pad on the Trezor Model T). ok dtucker@

OpenBSD-Commit-ID: 38b78903dd4422d7d3204095a31692fb69130817

1 files changed, 15 insertions, 8 deletions

diff --git a/ssh-keygen.c b/ssh-keygen.c
index aa4ec0655..cf8e1ba97 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.402 2020/03/06 18:29:14 markus Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.403 2020/03/13 03:12:17 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -2960,18 +2960,25 @@ do_download_sk(const char *skprovider, const char *device)
         struct sshkey **keys;
         size_t nkeys, i;
         int r, ok = -1;
-        char *fp, *pin, *pass = NULL, *path, *pubpath;
+        char *fp, *pin = NULL, *pass = NULL, *path, *pubpath;
         const char *ext;
 
         if (skprovider == NULL)
                 fatal("Cannot download keys without provider");
 
-        pin = read_passphrase("Enter PIN for authenticator: ", RP_ALLOW_STDIN);
-        if ((r = sshsk_load_resident(skprovider, device, pin,
-            &keys, &nkeys)) != 0) {
-                freezero(pin, strlen(pin));
-                error("Unable to load resident keys: %s", ssh_err(r));
-                return -1;
+        for (i = 0; i < 2; i++) {
+                if (i == 1) {
+                        pin = read_passphrase("Enter PIN for authenticator: ",
+                            RP_ALLOW_STDIN);
+                }
+                if ((r = sshsk_load_resident(skprovider, device, pin,
+                    &keys, &nkeys)) != 0) {
+                        if (i == 0 && r == SSH_ERR_KEY_WRONG_PASSPHRASE)
+                                continue;
+                        freezero(pin, strlen(pin));
+                        error("Unable to load resident keys: %s", ssh_err(r));
+                        return -1;
+                }
         }
         if (nkeys == 0)
                 logit("No keys to download");