upstream: fix two PIN entry bugs on FIDO keygen: 1) it would allow more

than the intended number of prompts (3) and 2) it would SEGV too many
incorrect PINs were entered; based on patch by Gabriel Kihlman

OpenBSD-Commit-ID: 9c0011f28ba8bd8adf2014424b64960333da1718

1 files changed, 12 insertions, 6 deletions

diff --git a/ssh-keygen.c b/ssh-keygen.c
index a6ba6cc7a..0d6ed1fff 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.397 2020/02/06 22:30:54 naddy Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.398 2020/02/07 03:27:54 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -3588,7 +3588,7 @@ main(int argc, char **argv)
                 passphrase = NULL;
                 if ((attest = sshbuf_new()) == NULL)
                         fatal("sshbuf_new failed");
-                for (i = 0 ; i < 3; i++) {
+                for (i = 0 ; ; i++) {
                         fflush(stdout);
                         r = sshsk_enroll(type, sk_provider, sk_device,
                             sk_application == NULL ? "ssh:" : sk_application,
@@ -3598,15 +3598,21 @@ main(int argc, char **argv)
                                 break;
                         if (r != SSH_ERR_KEY_WRONG_PASSPHRASE)
                                 fatal("Key enrollment failed: %s", ssh_err(r));
-                        if (passphrase != NULL)
+                        else if (i > 0)
+                                error("PIN incorrect");
+                        if (passphrase != NULL) {
                                 freezero(passphrase, strlen(passphrase));
+                                passphrase = NULL;
+                        }
+                        if (i >= 3)
+                                fatal("Too many incorrect PINs");
                         passphrase = read_passphrase("Enter PIN for "
                             "authenticator: ", RP_ALLOW_STDIN);
                 }
-                if (passphrase != NULL)
+                if (passphrase != NULL) {
                         freezero(passphrase, strlen(passphrase));
-                if (i > 3)
-                        fatal("Too many incorrect PINs");
+                        passphrase = NULL;
+                }
                 break;
         default:
                 if ((r = sshkey_generate(type, bits, &private)) != 0)