upstream: give more context to UpdateHostKeys messages, mentioning

that the changes are validated by the existing trusted host key. Prompted by
espie@ feedback and ok markus@

OpenBSD-Commit-ID: b3d95f4a45f2692f4143b9e77bb241184dbb8dc5

1 files changed, 20 insertions, 3 deletions

diff --git a/clientloop.c b/clientloop.c
index f02fc5811..175b84802 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.335 2020/01/26 00:14:45 djm Exp $ */
+/* $OpenBSD: clientloop.c,v 1.336 2020/01/29 07:51:30 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1888,11 +1888,22 @@ hostkeys_find(struct hostkey_foreach_line *l, void *_ctx)
 }
 
 static void
-update_known_hosts(struct hostkeys_update_ctx *ctx)
+hostkey_change_preamble(void)
 {
-        int r, was_raw = 0;
         LogLevel loglevel = options.update_hostkeys == SSH_UPDATE_HOSTKEYS_ASK ?
             SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_VERBOSE;
+
+        do_log2(loglevel, "The server has updated its host keys.");
+        do_log2(loglevel, "These changes were verified by the server's "
+            "existing trusted key.");
+}
+
+static void
+update_known_hosts(struct hostkeys_update_ctx *ctx)
+{
+        int r, was_raw = 0, first = 1;
+        int asking = options.update_hostkeys == SSH_UPDATE_HOSTKEYS_ASK;
+        LogLevel loglevel = asking ?  SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_VERBOSE;
         char *fp, *response;
         size_t i;
         struct stat sb;
@@ -1903,16 +1914,22 @@ update_known_hosts(struct hostkeys_update_ctx *ctx)
                 if ((fp = sshkey_fingerprint(ctx->keys[i],
                     options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
                         fatal("%s: sshkey_fingerprint failed", __func__);
+                if (first && asking)
+                        hostkey_change_preamble();
                 do_log2(loglevel, "Learned new hostkey: %s %s",
                     sshkey_type(ctx->keys[i]), fp);
+                first = 0;
                 free(fp);
         }
         for (i = 0; i < ctx->nold; i++) {
                 if ((fp = sshkey_fingerprint(ctx->old_keys[i],
                     options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
                         fatal("%s: sshkey_fingerprint failed", __func__);
+                if (first && asking)
+                        hostkey_change_preamble();
                 do_log2(loglevel, "Deprecating obsolete hostkey: %s %s",
                     sshkey_type(ctx->old_keys[i]), fp);
+                first = 0;
                 free(fp);
         }
         if (options.update_hostkeys == SSH_UPDATE_HOSTKEYS_ASK) {