upstream: some clarifying comments

OpenBSD-Commit-ID: 5268479000fd97bfa30ab819f3517139daa054a2

1 files changed, 9 insertions, 2 deletions

diff --git a/ssh-ecdsa-sk.c b/ssh-ecdsa-sk.c
index 0004a73ca..c6927ecb2 100644
--- a/ssh-ecdsa-sk.c
+++ b/ssh-ecdsa-sk.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-ecdsa-sk.c,v 1.7 2020/06/22 05:58:35 djm Exp $ */
+/* $OpenBSD: ssh-ecdsa-sk.c,v 1.8 2020/06/22 23:44:27 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
@@ -97,6 +97,13 @@ webauthn_check_prepare_hash(const u_char *data, size_t datalen,
                 r = SSH_ERR_INVALID_FORMAT;
                 goto out;
         }
+
+        /*
+         * Prepare the preamble to clientData that we expect, poking the
+         * challenge and origin into their canonical positions in the
+         * structure. The crossOrigin flag and any additional extension
+         * fields present are ignored.
+         */
 #define WEBAUTHN_0      "{\"type\":\"webauthn.get\",\"challenge\":\""
 #define WEBAUTHN_1      "\",\"origin\":\""
 #define WEBAUTHN_2      "\""
@@ -113,7 +120,7 @@ webauthn_check_prepare_hash(const u_char *data, size_t datalen,
         fprintf(stderr, "%s: expected clientData premable:\n", __func__);
         sshbuf_dump(m, stderr);
 #endif
-        /* Check that the supplied clientData matches what we expect */
+        /* Check that the supplied clientData has the preamble we expect */
         if ((r = sshbuf_cmp(wrapper, 0, sshbuf_ptr(m), sshbuf_len(m))) != 0)
                 goto out;